Symposium Organizers
Sung Hun Wee Oak Ridge National Laboratory
Venkat Selvamanickam University of Houston
Quanxi Jia Los Alamos National Laboratory
Hideo Hosono Tokyo Institute of Technology
Hai-Hu Wen Institute of Physics, CAS
L1: Iron Arsenide Superconductors I
Session Chairs
Paul Canfield
David Mandrus
Tuesday PM, April 06, 2010
Room 2005 (Moscone West)
9:00 AM - **L1.1
Grain Boundaries in Cuprates and Pnictides – Are There Reasonable Hopes for Better Properties?
David Larbalestier 1
1 ASC/NHMFL, Florida State University, Tallahassee, Florida, United States
Show AbstractThe current that can cross grain boundaries of arbitrary misorientation remains the single largest determinant of possible conductor architecture. In cuprates, experience with YBCO and Bi-2223 shows that misorientations of only a few degrees decrease the critical current density significantly, the critical angle at which depression of the intragrain current density starts in [001] tilt grain boundaries being as small as 2-3°. In a broad sense the better properties of YBCO compared to Bi-2223, which corresponds to the 1st to 2nd generation HTS conductor technology change, can be plausibly explained just in terms of the much worse uniaxial texture (FWHM ~12°) of Bi-2223, as compared to the biaxial texture of ~5° possible in YBCO. But in fact the situation is more complex and more promising than this simple explanation would suggest. Neither Bi-2223 nor pure YBCO can be significantly overdoped, making the case of round wire Bi-2212 which can be overdoped of great interest. Moreover there are marked benefits of allowing ex situ growth in which grain boundaries meander so as to avoid separate populations of Abrikosov-Josephson vortices in GBs. Segregation effects can also very beneficially enhance the Jc of GBs. Moreover, GBs in pnictides appear to show similar sensitivity to misorientation as in the cuprates, making the detailed understanding of how far GBs can be pushed of great practical and scientific interest. I will review recent work of my collaborators (Dmytro Abraimov, Chang-Beom Eom, Ron Feenstra, Alex Gurevich, Eric Hellstrom and Fumitake Kametani) and me on Bi-2212, YBCO and its related compounds and pnictides with a particular view towards expanding the domain in which GB properties can be enhanced.
9:30 AM - **L1.2
Symmetry or Asymmetry Between Electron- and Hole-dopings in Fe-Pnictide Superconductors.
Paul C. W. Chu 1 2
1 Texas Center for Superconductivity, University of Houston, Houston, Texas, United States, 2 , Lawrence Berkeley National Laboratory, Berkeley, California, United States
Show AbstractThe symmetric or asymmetric nature of doping on the Tc of high temperature superconductors can have significant implications on the theoretical models proposed and on their predictions. Although it has been demonstrated chemically that superconductivity can be induced in Fe-pnictides by either electron or hole doping, the real underlying reason remains unsettled. A systematic high pressure study has therefore been carried out on Fe-pnictides with dopings of different chemical nature (i.e., electron or hole) at different concentrations to explore this specific feature of high temperature superconductors by resistive, thermoelectric, and magnetic measurements. The results will be presented, discussed, and compared with model calculations.
The work in Houston is supported in part by AFOSR Grant No. FA9550-09-1-0656, the T. L. L. Temple Foundation, the John J. and Rebecca Moores Endowment, and the State of Texas through the Texas Center for Superconductivity at the University of Houston; and at Lawrence Berkeley Laboratory by the Director, Office of Science, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering of the U.S. Department of Energy.
10:00 AM - **L1.3
Spin Fluctuations in Fe-based Superconductors.
David Mandrus 1 2
1 Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States, 2 Department of Materials Science and Engineering, The University of Tennessee, Knoxville, Tennessee, United States
Show AbstractSpin fluctuations are widely believed to be involved in the pairing mechanism of Fe-based superconductors. In this talk I will review what we have learned about spin fluctuations from experiment, with a particular focus on neutron scattering and NMR measurements. I will also discuss the effects of spin and nematic fluctuations on the elastic properties of the Fe-based materials. Research supported by DOE BES Division of Materials Sciences and Engineering.
10:30 AM - L1.4
Unification of the Electronic Phase Diagrams of the RO1-xFxFeAs-Compounds by Using the Real Fluorine Content.
Anke Koehler 1 2 , Guenter Behr 1
1 , IFW Dresden, Dresden Germany, 2 , Goethe-Universität, Frankfurt am Main Germany
Show AbstractThe physical properties of RO1-xFxFeAs-compound are strongly depended on the fluorine doping (substitution of the oxygen by fluorine). The sample with a fluorine content of about x = 0.1 shows the maximum transition temperature up to Tc = 56 K. But so far, the published data also show contradicting results concerning the dependency of the magnetic and superconducting transition temperatures on the fluorine content. E.g., a publication by Uemura [1] presents a comparison of different electronic phase diagrams for the compounds LaO1-xFxFeAs, SmO1-xFxFeAs and CeO1-xFxFeAs. It seems to be not easy to bring this divers data into agreement with each other. However, our measurement of the actual fluorine content of the samples by wavelength-dispersive X-ray spectroscopy (WDX) enables solving this inconsistence. We found the nominal fluorine content (initial weight) x does not always correspond to the effectively measured value. In particular for SmO1-xFxFeAs, the measured value only reached approximately half of the required value. In the lanthanum compound LaO1-xFxFeAs, we found a good agreement mainly for x = 0.05, but the fluorine hardly goes into the sample for x < 0.05. Consequently, the graphs showing the dependence of the magnetic and superconducting transition temperature on the fluorine content have to be corrected. We can conclude that the nominal values overstate the real fluorine content in many cases. The optimum values xopt (for maximum Tc) become similar for different RO1-xFxFeAs-compounds when using the corrected x-values. The apparently conflicting literature data are crucially caused by the lack of agreement of nominal and real composition as well as inhomogeneities. Generally, one has to point out that a more substantial characterization of the samples is necessary to understand the physical properties.[1] Y.J. Uemura, Physica B 404 (2009) 3195
10:45 AM - L1.5
Role of Chemical Composition in pnictide HTSC.
Lorenzo Malavasi 1 , Gianluca Artioli 1 , Maria Mozzati 2
1 Physical Chemistry, University of Pavia, Pavia Italy, 2 Physics ``A. Volta", University of Pavia, Pavia Italy
Show AbstractWe have investigated the NdFeAsO1-xFx and SmFeAsO1-xFx solid solution by determining the role of chemical composition in terms of "real" F-stoichiometry, amount of spourius phases (as a function of F-doping) and oxygen stoichiometry. The results reported here have important implications since they demonstrate that by using a routine method for the preparation of F-doped iron based HTSCs the obtained final stoichiometry is quite different from the nominal ones. The precise definition of the lower limit of F-content for the insurgence of superconductivity and of the TC vs F trends require a strict control of F-stoichiometry (and oxygen stoichiometry). It is clear that the role played by F-content in pnictide HTSCs has several similarities with the role played by the oxygen content in cuprate superconductors. In a similar way, after the discovery of HTSC in cuprates some time was needed before the accurate and precise determination of oxygen content was recognized as the basic issue in order to provide reliable and comparable results in those materials. Important issues regarding the chemical control in pnictide HTSC still remain open; among these the development of routine methods for the exact determination of the oxygen content together with the F-content (since O-deficient samples show superconductivity) and a microscopic investigation of the F-distribution over the sample bulk.[1] L .Malavasi et al., JACS, 131, 12044[2] L. Malavasi et al., Angew. Chem. Int. Ed., in press
11:30 AM - **L1.6
Effects of Doping on BaFe2As2: Rules for Understanding When and How Superconductivity Can Be Induced.
Paul Canfield 1 2
1 Department of Physics, Iowa State University, Ames, Iowa, United States, 2 , Ames Laboratory, Ames, Iowa, United States
Show AbstractExtensive work on the transition metal (TM) doping of BaFe2As2 has been performed on over a hundred different sample compositions for TM = Co, Ni, Cu, Rh, and Pd. As a result a unified phase diagram has been formed and rules for when superconductivity can be stabilized, as well as understanding of why it can be stabilized, have been formulated. In this talk I will provide an over-view of our work based on an analysis of structural, compositional, thermodynamic, transport, microscopic and spectroscopic measurements.Work at the Ames Laboratory was supported by the Department of Energy, Basic Energy Sciences under Contract No. DE-AC02-07CH11358.
12:00 PM - **L1.7
Single Crystal Growth and Superconducting Properties of LnFeAsO (Ln=La, Pr, Nd, Sm, Gd) and AFe2As2 (A=Ba, Rb, Ca, Eu).
Janusz Karpinski 1 , Nikolai Zhigadlo 1 , Serguiy Katrych 1 , Zbigniew Bukowski 1 , Roman Puzniak 1 , Krzysztof Rogacki 1 , Philip Moll 1 , Bertram Batlogg 1 , Stephen Weyeneth 2 , Hugo Keller 2 , Mauro Tortello 3 , Renato Gonnelli 3 , Fedor Balakirev 4
1 Laboratory for Solid State Physics, ETH , Zurich Switzerland, 2 Physik Institut, Universität Zürich, Zürich Switzerland, 3 Dipartimento di Fisica, Politecnico di Torino, Torino Italy, 4 , National High Magnetic Field Laboratory , Los Alamos, New Mexico, United States
Show AbstractGrowth, structure, and superconducting properties of LnFeAsO (Ln=La, Pr, Nd, Sm, Gd) and AFe2As2 (A=Ba, Ca, Eu) single crystals are presented and compared. LnFeAsO single crystals were grown from NaCl/KCl flux at high-pressure of 30 kbar. Superconductivity in LnFeAsO has been induced by partial substitution of O by F, Ln by Th or Ar by P. Superconducting single crystals of Ba1-xRbxFe2As2, CaFe2- xCoxAs2 and EuFe2-xCoxAs2 were grown in quartz ampoules from Sn flux at low pressure. X-ray diffraction studies confirmed high structural perfection of the studied crystals. Four-probe magneto-resistivity measurements on SmFeAs(O,F) were performed with in- and out-of-plane current flow in magnetic field up 65 T applied along both the c-axis and the ab-plane. The critical current density was found to be remarkably high and at low temperature almost independent on field direction and exceeds 2*10^6 A/cm2 measured both magnetically and by transport. Isotropic character of critical current seems to be very promising for practical application of pnictides. The penetration depth anisotropy γλ and upper critical field anisotropy γH are different and temperature dependent, what indicates multigap electronic structure. Ba1- xRbxFe2As2 crystals are electronically more isotropic than LnFeAsO1-xFx, indicative of better coupling of the FeAs layers by the (Ba,Rb) layers than by the Sm(O,F) layers. Point-Contact Andreev-Reflection spectroscopy studies show the existence of two gaps in the SmFeAsO1-xFx crystals, which energy varies with doping level.
12:30 PM - L1.8
Half-integer Flux Quantization in Iron-based High-temperature Superconductors.
Ching-Tzu Chen 1 , Chang C. Tsuei 1 , Mark Ketchen 1 , Zhi-An Ren 2 , Zhong Xian Zhao 2
1 Physical Sciences Department, IBM TJ Watson Research Center, Yorktown Heights, New York, United States, 2 , Institute of Physics, Chinese Academy of Sciences, Beijing China
Show AbstractThe recent discovery of iron-based superconductors challenges the existing paradigm of high-temperature superconductivity. Owing to their unique multi-orbital band structure, magnetism and electron correlation, prevailing theories propose a novel s-wave pairing state, with the order parameter changing sign between the electron and hole Fermi pockets. However, because of the complex Fermi surface topology and other material related issues, the predicted sign reversal remains unconfirmed. To elucidate the nature of the pairing, we have developed a new phase-sensitive technique that enables the observation of both integer and half-integer flux-quantum transitions in composite niobium/iron-pnictide loops. This finding establishes the microscopic spin and orbital structures of electron pairing, providing the first phase-sensitive evidence for the predicted exotic sign-reversed pairing symmetry in these new superconductors. Implications on the microscopic pairing mechanism will also be discussed.
12:45 PM - L1.9
Current Transport at Grain Boundaries in Superconducting Ba(Fe1-xCox)2As2 Bicrystals.
Jianyi Jiang 1 , A. Yamamoto 1 , A. Polyanskii 1 , D. Abraimov 1 , C. Tarantini 1 , F. Kametani 1 , J. Weiss 1 , Eric Hellstrom 1 , Alex Gurevich 1 , David Larbalestier 1 , Sanghan Lee 2 , C. Folkman 2 , C. Bark 2 , S. Baek 2 , H. Jang 2 , C. Eom 2 , C. Nelson 3 , Y. Zhang 3 , X. Pan 3
1 Applied Superconductivity Center, National High Magnetic Field Laboratory, Tallahassee, Florida, United States, 2 Department of Materials Science and Engineering, University of Wisconsin, Madison, Wisconsin, United States, 3 Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan, United States
Show AbstractGrain boundaries (GBs) transparent to current are intrinsic to Nb-Ti, Nb3Sn and MgB2. The ferropnictide superconductors, which now encompass 4 families of materials, have important application properties, namely Tc up to 55K, Hc2 of 100 T or more, strong vortex pinning, moderate anisotropy, and Hirr close to Hc2, leaving open only the key question whether GBs can transmit current. Here we report the explicit study of this vital property, using extensive transport, magneto-optical (MO), low-temperature scanning laser microscopy (LTLSM), and high resolution transmission electron microcopy (HRTEM) investigations of Ba(Fe1-xCox)2As2 (Ba-122) epitaxial thin film bicrystals. We show that the critical current density Jgb across [001] tilt GBs of thin film Ba(Fe1-xCox)2As2 bicrystals is strongly depressed, similar to high-Tc cuprates.
L2: Iron Arsenide Superconductors II
Session Chairs
Xianhui Chen
Bernhard Holzapfel
Tuesday PM, April 06, 2010
Room 2005 (Moscone West)
2:30 PM - **L2.1
Superconductivity and Phase Diagram in High-Tc Pnictide Superconductors.
Xianhui Chen 1
1 , University of Science and Tchnology of China, Hefei China
Show AbstractWe will talk about the discovery of superconductivity with Tc higher than 40 K in Fe-based superconductors SmFeAsO1-xF¬. Tc higher than McMillan limit of 39 K definitely proves pnictide superconductors high-Tc superconductivity1,2. In this talk, we present the transport properties: resistivity, Hall coefficient and transport properties under high magnetic field. These results suggest a quantum phase transition around x=0.14 in SmFeAsO1-xFx system. A electronic phase diagram is proposed, and coexistence of superconductivity and spin-density-wave is observed in Sm-1111 and Ba-122 system. We show you the contrasting behavior between the region with coexistence of superconductivity and spin-density-wave and the region without the spin-density-wave ordering by high pressure, structure, high-magnetic field and muSR measurements. In this talk, we report the novel family of pnictide-oxides compounds (SrF)2Ti2Pn2O (Pn=As and Sb) and (SmO)2Ti2Sb2O, which were predicted from the stacking of the well-known fluorite type block [Sr2F2]2+ or [Sm2O2]2+ alternating regularly with the anti-CuO2-type Ti2O square planar layer. These compounds also exhibit an anomalous transition in resistivity and susceptibility at TS. A drop in carrier concentration evidenced by a pronounced rise in RH is observed below TS for (SrF)2Ti2Sb2O. Additionally, TEP changes sign below TS for (SrF)2Ti2Pn2O. Heat capacity demonstrates an anomalous peak at TS, consistent with that observed in resistivity and susceptibility. Such anomaly could arise from the SDW/CDW instability or structure distortion. All those behaviors of compounds are quite similar to that of FeAs-based high-TC parent compound REFeAsO and AEFe2As2 with SDW instability. They could be considered as a possible parent compound for superconductivity.1. Chen, X. H. et al. Nature 453, 761-762 (2008).2. Liu, R. H. et al. Phys. Rev. Lett. 101, 087001 (2008).
3:00 PM - **L2.2
Pressure Studies for 1111 and 11 Type Iron-based Superconductors.
Hiroki Takahashi 1 , Hironari Okada 1 , Hiroyuki Takahashi 2 , Yoichi Kamihara 3 , Satoru Matsuishi 4 , Masahiro Hirano 4 5 , Hideo Hosono 4 5 6 , Yoshikazu Mizuguchi 7 8 , Yoshihiko Takano 7 8
1 College of Humanities & Sciences, Nihon University and JST,TRIP, Tokyo Japan, 2 Graduate School of Integrated Basic Sciences, Nihon University, Tokyo Japan, 3 JST, TRIP, Tokyo Institute of Technology, Yokohama Japan, 4 FRC, Tokyo Institute of Technology, Yokohama Japan, 5 ERATO-SORST, JST, in FRC, Tokyo Institute of Technology, Yokohama Japan, 6 Materials and Structures Laboratory, Tokyo Institute of Technology, Yokohama Japan, 7 , National Institute for Materials Science, Tsukuba Japan, 8 , University of Tsukuba, Tsukuba Japan
Show AbstractElectrical, magnetic and structural measurements on iron-based superconductors under high pressure have been performed. Large enhancement of Tc and pressure-induced superconductivity were found in LaFeAsO1-xFx system. In this paper, we will present the recent results of electrical, magnetic and structural studies on 1111 and 11 type iron-based superconductors.For LaFeAsO1-xFx, LaFeAsO exhibits the magnetic and structural transitions. F-doping suppressed these phase transitions and raised superconductivity. For x= 0.11 and 0.14, the maximum Tc was 43 K under high pressure. However, pressure effect on Tc of lightly doped sample with x = 0.05 was not so large. The lightly doped samples are thought to be affected by magnetic phase which exists close to the superconducting phase. In case of LaFeAsO, the maximum Tc was about 20 K under high pressure, which was as low as x = 0.05. The high-pressure Mössbauer spectrum measurements for LaFeAsO revealed that the magnetic transition disappears at around 30 GPa, which indicates that the suppression of Tc may be affected by the magnetic phase. High-pressure x-ray diffraction measurement is now proceeding for LaFeAsO1-xFx to examine crystal structure under high pressure at low temperature.For SmFeAsO1-xFx, the maximum Tc of 50 K for x = 0.07 was not enhanced by pressure, which is contrast to the LaFeAsO1-xFx. SmFeAsO exhibits the pressure-induced superconductivity like LaFeAsO. However, the maximum Tc of SmFeAsO was half value of one of LaFeAsO, although the maximum Tc of 50 K is twice as much as 26 K of LaFeAsO1-xFx. For Ca(Fe1-xCox)AsF, CaFeAsO exhibits the magnetic and structural transition. Co-doping suppressed these phase transitions and raised superconductivity. Pressure-induced superconductivity was observed for x = 0.0 and 0.05 after suppression of these transitions. Unlike the pressure effect on Tc for LaFeAsO1-xFx, all the Co-doped superconductors show no marked enhancement, which is less than 1 K. Consequently, the highest Tc was obtained in parent compound under high pressure. There results suggest that Co doping suppresses superconductivity. The maximum Tc observed in parent compound is higher than that in LaFeAsO, suggesting that CaFeAsF is considered as a candidate parent compound for realizing higher Tc.For FeTe0.92, two resistive anomalies were found under high pressure. Unlike FeAs-based compounds, pressure-induced superconductivity was not detected under high pressures up to 19 GPa, although the resistive anomaly at atmospheric pressure due to the structural phase transition and the antiferromagnetic ordering was suppressed by applying pressure. The existence of high pressure phases which is examined by x-ray diffraction measurements may inhibit the emergence of superconductivity in FeTe0.92.
3:30 PM - L2.3
Competition Between Superconductivity and Magnetic Ordering in Iron Chalcogenide.
Romain Viennois 1 2 , Giannini Enrico 2 , Cerny Radovan 3 , Jason Hancock 2 , Carmine Senatore 2 , Dirk van der Marel 2
1 Institut Gerhardt, Universite Montpellier II, Montpellier France, 2 Departement de la Matiere Condensee, Universite de Geneve, Geneve Switzerland, 3 Laboratoire de Cristallographie, Universite de Geneve, Geneve Switzerland
Show AbstractAmong the new iron-based superconducting class discovered in 2008, the iron chalcogenides have recently attracted the attention in reason to their simple crystalline structure composed of only one two-dimensional layer, to the absence of arsenic and the possibility to grow large single-crystals. In the present communication, we will show the crucial role of the presence of iron in a second site with square-pyramidal coordination and its effect on the structural and magnetic properties on selenium alloyed iron telluride. Indeed, there is a competition between magnetism and superconductivity in function of both the selenium concentration and the iron content in the non-tetrahedral site. We will also study the vortex phase diagram for the 30 % Se alloyed iron telluride and show from heat capacity experiment under high field (up to 19 T) the very high value of the critical filed (more than 50 T) despite the low critical temperature of about 12 K. Finally we will also discuss about the spectroscopic probes of the magnetic ground state of iron telluride and about the problems of the determination of spectral weight in the optical properties and the efficency of the standard band structure calculations to explain the optical properties.
3:45 PM - L2.4
Zintl Phases as Doping Sources in the Flux Synthesis of Iron Arsenide Superconductors.
Josiah Mathieu 1 , Susan Latturner 1
1 Chemistry and Biochemistry, Florida State University, Tallahassee, Florida, United States
Show AbstractZintl phases such as K4Sn4 and K4Pb4 are being explored as precursors for improved alkali metal doping control in metal flux synthesis of iron arsenide superconductors. Initial experiments have shown successful incorporation and control of potassium doping in KxBa1-xFe2As2. The growth of large crystals facilitated by this method allows for a better crystallographic analysis of the nature of tin incorporation from the flux, which appears to lower the superconducting transition temperature. The current emphasis is now on increasing crystal size with this method, while maintaining dopant control. This technique is also being explored to assess the impact of doping in related phases such as BaNi2As2.
4:30 PM - **L2.5
Fabrication and Transport Critical Current Properties of Iron-based Superconducting Wires and Tapes by the PIT Method.
Yanwei Ma 1 , Lei Wang 1 , Yanpeng Qi 1 , DongLiang Wang 1 , Xiangping Zhang 1 , Zhaoshun Gao 1
1 , Institute of Electrical Engineering, Chinese Academy of Sciences, Beijing China
Show AbstractThe recent discovery of superconductivity in the iron based superconductors with very high upper critical fields presents a new possibility for practical applications, but fabricating fine-wire is a challenge because of mechanically hard and brittle powders and the toxicity and volatility of arsenic. In this talk, we present the synthesis and the physical characterization of iron pnictide wires and tapes prepared by the common powder-in-tube method (PIT). A new class of high-Tc iron pnictide composite wires, such as LaFeAsO1−xFx, SmFeAsO1−xFx and Sr1-xKxFeAs, has been fabricated by the in situ PIT technique. Most importantly, we recently achieved large transport critical currents in Sr1-xKxFeAs wires and tapes using the Ag powder as dopants. The transport Jc improvement was mainly due to the elimination of microcracks and enhanced connectivity. This beneficial effect was promoted by the Ag addition. The wires and tapes exhibit a very weak Jc-field dependence behavior even at high temperatures. The upper critical field Hc2(0) value can exceed 100 T, surpassing those of MgB2 and all the low temperature superconductors and indicating a strong potential for applications requiring very high field. These results clearly demonstrate the feasibility of producing superconducting pnictide composite wire.
5:00 PM - **L2.6
Structural and Electric Transport Properties of Epitaxially Grown Superconducting Iron-based Pnictide Thin Films Prepared by Pulsed Laser Deposition.
Bernhard Holzapfel 1 , Martin Kidszun 1 , Silvia Haindl 1 , Tom Thersleff 1 , Stefan Baunack 3 , Ruben Huehne 1 , Alexander Kauffmann 1 , Konstantin Nenkov 1 , Guenter Fuchs 1 , Nadja Kozlova 1 , Jochen Werner 2 , Ludwig Schultz 1
1 Institute for Metallic Materials, IFW Dresden, Dresden Germany, 3 Institute for Integrative Nanoscience , IFW Dresden, Dresden Germany, 2 Institute for Solid State Research, IFW Dresden, Dresden Germany
Show AbstractSince the discovery of high-temperature superconductivity in LaFeAsO1-xFx by Kamihara et al. an intensive investigation of this material system has started. We report on the progress in superconducting thin film fabrication of the so called 1111 and 122 phase superconductors. Both polycrystalline and epitaxial thin films were successfully grown by a two step Pulsed Laser Deposition approach for the 1111-LaFeAs(O,F) superconductors. For Co substituted 122-BaFeAs thin films in-situ epitaxial growth is possible on a number of substrate materials. Structural investigations by XRD and TEM indicate a nearly phase pure and homogeneous film growth. For the 1111 films resistive measurements show a high superconductive transition temperature up to 28 K and pulsed field investigations up to 40 T demonstrate a steep slope of the upper critical field. An overview on the current status with regard to the obtained magnetic phase diagram including the results of U(I)-measurements, critical current and anisotropy for both systems will be presented. Further, the role of flux pinning and possible applications will be discussed.
5:30 PM - L2.7
Template Engineering of Co-doped BaFe2As2 Single-crystal Thin Films.
Sanghan Lee 1 , Chung Wung Bark 1 , Seung Hyub Baek 1 , Ho Won Jang 1 , Chad Folkman 1 , Chang-Beom Eom 1 , Jianyi Jiang 2 , Jeremy Weiss 2 , Chiara Tarantini 2 , Anatolii Polyanskii 2 , Dmytro Abraimov 2 , Akiyasu Yamamoto 2 , Eric Hellstrom 2 , David Larbalestier 2 , Christopher Nelson 3 , Yi Zhang 3 , Xiao Qing Pan 3
1 , UW-Madison, Madison, Wisconsin, United States, 2 , FSU, Tallahassee, Florida, United States, 3 , U of Michigan, Ann Arbor, Michigan, United States
Show AbstractUnderstanding new superconductors requires high-quality epitaxial thin films to explore intrinsic electromagnetic properties, control grain boundaries and strain effects, and evaluate device applications. So far superconducting properties of ferropnictide thin films appear compromised by imperfect epitaxial growth and poor connectivity of the superconducting phase. Here we report novel template engineering using single-crystal intermediate layers of (001) SrTiO3 and BaTiO3 grown on various perovskite substrates that enables genuine epitaxial films of Co-doped BaFe2As2 with high transition temperature (Tc, ρ=0 of 21.5K), small transition widths (1.3K), superior Jc of 4.5 MA/cm2 (4.2K, self field) and strong c-axis flux pinning. Implementing SrTiO3 or BaTiO3 templates to match the alkaline earth layer in the Ba-122 with the alkaline earth-oxygen layer in the templates opens new avenues for epitaxial growth of ferropnictides on multi-functional single crystal substrates. Beyond superconductors, it provides a framework for growing heteroepitaxial intermetallic compounds on various substrates by matching interfacial layers between templates and thin film overlayers.
5:45 PM - L2.8
Chemical Stability of Co-doped AEFe2As2 (AE = Ba and Sr) Epitaxial Thin Films and Improvement of Crystalline Qualities and Superconducting Properties.
Takayoshi Katase 1 , Hidenori Hiramatsu 2 , Toshio Kamiya 1 2 , Hideo Hosono 1 2 3
1 , Materials and Structures Laboratory, Tokyo Institute of Technology, Yokohama Japan, 2 , ERATO-SORST, Japan Science and Technology Agency, Yokohama Japan, 3 , Frontier Research Center, Tokyo Institute of Technology, Yokohama Japan
Show AbstractAbstractExtensive researches on superconductivity in Fe-based layered compounds have been performed since the discovery of superconductivity at 26 K in F-doped LaFeAsO [1], and the superconducting transition temperatures (Tc) over 50 K in REFeAsO (RE = rare earths) [2,3] have been reported. New Fe-based high-Tc superconducting materials have been found also in other materials systems composed of a square lattice of Fe atoms. A prominent feature of these Fe-based superconductors is high critical magnetic fields, which are important for practical applications. To measure the intrinsic properties of Fe-based superconductors and apply them to superconducting devices, it is important to grow high-quality epitaxial films. We reported epitaxial growth of Fe-based superconductors such as Co-doped SrFe2As2 (SrFe2As2:Co) [4], but these films are not satisfactory for a device application because they have rough surfaces and are decomposed by reactions with water vapor in an ambient atmosphere even at room temperature (RT). Here we report epitaxial growth of Co-doped BaFe2As2 (BaFe2As2:Co) films. They exhibited the onset superconducting transition temperature of ~20 K and had higher crystallinity than the SrFe2As2:Co films. Their surfaces were composed of atomically-flat steps-and-terraces structures. It is worth noting that the BaFe2As2:Co epitaxial films are stable against water vapor at least for 48 hours of exposure at RT. We will discuss the origin of the chemical stability of BaFe2As2:Co compared with that of SrFe2As2:Co. [1]Y. Kamihara et al., J. Am. Chem. Soc. 130 (2008) 3296. [2] X.-H. Chen et al., Nature 453 (2008) 761. [3] C. Wang et al., Europhys. Lett. 83 (2008) 67006. [4] H. Hiramatsu et al., Appl. Phys. Express 1 (2008) 101702.
Symposium Organizers
Sung Hun Wee Oak Ridge National Laboratory
Venkat Selvamanickam University of Houston
Quanxi Jia Los Alamos National Laboratory
Hideo Hosono Tokyo Institute of Technology
Hai-Hu Wen Institute of Physics, CAS
L3: HTS Wires and Films
Session Chairs
Wednesday AM, April 07, 2010
Room 2005 (Moscone West)
9:00 AM - **L3.1
Artificial Nanostructures in HTS Films Grown via PLD: Formation and Performance.
Alexander Usoskin 1 , Alexander Rutt 1 , Antje Hallbauer 1 , Klaus Schlenga 1
1 , Bruker HTS GmbH, Alzenau Germany
Show AbstractBeing an extremely non-equilibrium process, the pulsed laser deposition (PLD) exhibits a number of intrinsic features including: (i) a wide energy spectrum up to 100 eV for particles/ion flow, (ii) flow of self-ejected particles, (iii) flow of adiabatically condensed nano-particulates and (iv) plasma flow, which interacts with the growing film. None of these film growth conditions are common for other deposition techniques.Together with artificial nano-inclusions originating from doped or periodically alternating targets these features determine specific morphology and structures of nano-particles embedded in HTS films. In this study, different techniques for the formation of such nano-structures via PLD were employed and compared one to other. Conditions for random and quasi-periodic spatial distribution of the nano-pinning centers are analysed. Performance of HTS coated conductors with different types of nano-inclusions is demonstrated in the range from 6 to 18 T at 4.2 K at different field orientations. The most efficient ways for nano-structuring of long-length HTS coated conductors are discussed in a view of applicability in industrial production.This work is supported in part by German Ministry of Economy and Technology (BMWi), project no. 0327456A.
9:30 AM - **L3.2
Enhancing Performance of MOD-YBCO/RABiTS-based 2G Wire.
Martin Rupich 1 , Xiaoping Li 1 , Srivatsan Sathyamurthy 1 , Cees Thieme 1 , Steve Fleshler 1
1 , American Superconductor Corporation, Devens, Massachusetts, United States
Show AbstractAmerican Superconductor is manufacturing 2G wire for initial commercial applications. The properties of the current 2G wire satisfies the requirements for these projects; however, improvement in the wire performance, properties and cost is needed to address the broad range of anticipated commercial and military applications. In order to meet these anticipated wire requirements, AMSC’s R&D effort is focused on continual improvement in wire performance and cost reduction. Two major areas of focus are (1) higher critical current and (2) enhanced flux pinning. AMSC’s current 2G production wire, designed around a 0.8 μm thick YBCO layer deposited by a metal organic deposition (MOD) process, carries a critical current in the range of 280 – 300 A/cm-w (77K, sf). Additional improvement in the critical current requires increasing the thickness of the YBCO layer. This can be accomplished either by the deposition of multiple MOD-YBCO layers or, preferably, by increasing the thickness of the single layer MOD coating. In the past, the thickness of single-coat MOD-YBCO films has been limited by the formation of mechanical defects during the decomposition process, necessitating the multi-coat approach. However, improvements in the MOD precursor and decomposition process have increased the maximum thickness of the single-coat films by 50%, resulting in a critical current of ~440 A/cm-w. Current R&D is focused on establishing the limit of the single coat MOD process and additional increase in the critical current. Commercial applications, such as generators and motors, also require the 2G HTS wire to carry high current in the presence of magnetic fields. AMSC’s approach to controlling the flux pinning microstructure in MOD-YBCO is based on the selective formation of nanoparticles and planar defects in the YBCO films. These two processes can be controlled independently to tune the anisotropy for specific applications. Current R&D is focused on additional optimization of the pinning microstructure and identifying more efficient pinning centres for MOD-YBCO films. This presentation will present R&D progress on increasing the critical current of MOD-YBCO films and describe approaches to engineering improved pinning microstructures in MOD-YBCO films.
10:00 AM - **L3.3
Coated Conductor R&D Progress and Directions at LANL-STC.
Kenneth Marken 1
1 , Los Alamos National Laboratory, Los Alamos, New Mexico, United States
Show AbstractThe main coated conductor efforts at Los Alamos National Laboratory Superconductivity Technology Center are presently focused on simpler, lower cost IBAD templates and higher performance YBCO films achieved through engineered pinning structures. The nanometer scale substrate smoothness required for well textured IBAD coatings has conventionally been obtained by electropolishing, but rapid progress is underway with an alternative solution deposition coating which holds many advantages. Dramatically simplified IBAD template architectures have been demonstrated using nanocomposite layers. Improvements in critical current density and pinning force continue to be made through better understanding and control of the range of nanoengineered defects now available in the YBCO material. In addition to these main efforts, progress continues with the potentially lower cost reactive coevaporation method for depositing YBCO. Recent results in modeling and measuring ac losses in coated conductors will also be presented.
10:30 AM - **L3.4
Progress in Chemical Solution Approaches to Grow Nanocomposite Superconducting Films.
Teresa Puig 1 , Anna LLordes 1 , Anna Palau 1 , Huan Chen 1 , Katerina Zalamova 1 , Patricia Abellan 1 , Fernando Martinez 1 , Roxana Vlad 1 , Marta Gibert 1 , Jone Zabaleta 1 , Alberto Pomar 1 , Felip Sandiumenge 1 , Susagna Ricart 1 , Xavier Granados 1 , Narcis Mestres 1 , Xavier Obradors 1
1 , ICMAB-CSIC, Bellaterra Spain
Show AbstractChemical solution deposition (CSD) has emerged as a very competitive low cost technique to obtain epitaxial films, multilayers and nanocomposite films of high quality with controlled nanostructure and functionalities. In particular, the all CSD approach has been shown to be one of the most promising ways for low-cost production of second generation superconducting wires with high performances. The development of high performance nanostructured superconductors with enhanced vortex pinning properties requires a good control of YBa2Cu3O7 (YBCO) epitaxy and interfaces with second phase nanoparticles distributed within the superconducting matrix and with strain-induced nanoislands grown as interfacial templates. In this presentation we will report first on recent innovations concerning processing of YBCO films based on TFA precursors. We have particularly investigated the influence of oxygen and total pressure on the TFA route to YBCO films and we have devised a new route to decrease the growth temperature, keeping high superconducting performances. Second, we will report on latest advances to the preparation of nanocomposite YBCO films through modified metal-organic solutions, colloidal YBCO precursor solution with pre-formed nanoparticles and using oxide interfacial nanotemplates also grown by CSD. The role of strain and microstrain engineering to tune interfaces in nanocomposites and their correlation with vortex pinning will be highlighted as a very versatile tool to enhance vortex pinning. * We acknowledge financial support from MEC (MAT2008-01022), Consolider Nanoselect, Generalitat de Catalunya (Pla de Recerca SGR-770 and XaRMAE) and EU (HIPERCHEM and NESPA)
11:30 AM - L3.5
Performance Optimization and Coordinated Characterization of MOCVD-YBCO Films.
Tolga Aytug 1 , M. Paranthaman 1 , E. Specht 1 , S. Cook 1 , C. Cantoni 1 , F. List 1 , K. Kim 1 , Y. Zhang 1 , A. Goyal 1 , D. Christen 1 , Y. Chen 3 , V. Selvamanickam 3 , V. Maroni 2 , D. Miller 2 , A. Kropf 2 , N. Zaluzec 2
1 , Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States, 3 , SuperPower, Inc., Schenectady, New York, United States, 2 , Argonne national Laboratory, Argonne, Illinois, United States
Show AbstractA research-scale metal-organic chemical vapor deposition (MOCVD) system has been used to investigate processing variables for MOCVD REBCO precursors. In addition, we have sought to understand the effects of rare earth (Ce and Ho) and transition metal (Zr and Nb) addition/substitution on the micro-structural properties and flux pinning performance of these films. Systematic studies have revealed trends in the resulting performance/property correlations, as characterized by coordinated analyses of electrical transport, x-ray diffraction, scanning electron microscopy, and transmission electron microscopy, In particular, the micro-structural analyses correlate well with the flux pinning behavior and relate to differences in defect structures that are generated with the selective metal element doping. From the combination of these characterization techniques, an improved understanding of the growth characteristics and trends in pinning performance of MOCVD REBCO films was established and will be discussed.
11:45 AM - L3.6
YBCO Films Grown by Reactive Co-evaporation on Simplified Coated Conductor IBAD-MgO Templates.
Vladimir Matias 1 , Yates Coulter 1 , Terry Holesinger 1 , Boris Maiorov 1 , Chris Sheehan 1 , Brian Moeckly 2
1 MPA-STC, Los Alamos National Laboratory, Los Alamos, New Mexico, United States, 2 , Superconductor Technologies Inc., Santa Barbara, California, United States
Show AbstractWe describe a method for growth of high-quality high temperature superconducting (HTS) films by reactive co-evaporation (RCE) on ion-beam assisted deposition (IBAD) textured layers on top of metal substrates. The method utilizes cyclic deposition and reaction (CDR), by rotating the samples through a deposition zone and an oxygen reaction zone.[1] Temperature stability during HTS film growth is enhanced with this black-body type heater. Furthermore, we have demonstrated a simplified IBAD template architecture for RCE-CDR by the elimination of the epitaxial buffer layers such as LaMnO3 or SrTiO3.[2] YBa2Cu3Oy is grown directly on thin MgO layers which are grown on IBAD textured templates on flexible polycrystalline metal alloy tapes. The solution deposition planarization (SDP) process is used for coating the substrate tapes with a very smooth surface layer that is ready for IBAD deposition. The SDP layer serves as both a diffusion barrier layer and a bed layer for IBAD texturing. YBCO layers exhibit in-plane alignment with mosaic spreads less than 2.5°. Critical current density of 4 MA/cm^2, at 75 K and self field, has been achieved with this process in a YBCO film with 1 µm thickness. Best thick film to date by RCE had a critical current of 950 A/cm-width in self field at 75 K. We discuss some practical possibilities for manufacturing of superconducting wire using this method. This work is supported by the Department of Energy Office of Electricity Delivery & Energy Reliability. [1] V. Matias, J. Hänisch, D. Reagor, E.J. Rowley and C. Sheehan, IEEE Trans Appl. Supercon. 19 3172-4 (2009).[2] V. Matias, T. Holesinger, B. Maiorov, E. J. Rowley, Y. Coulter, C. Sheehan, C. Yung, V. Glyantsev and B. Moeckly, Super. Sci. Technol. to be published (2009).
12:00 PM - L3.7
Ink-jet Printing of Water-based YBa2Cu3Ox Coatings and Patterns.
Jonas Feys 1 , Simon Hopkins 2 , Jan Bennewitz 3 , Petra Lommens 1 , Klaartje De Buysser 1 , Isabel Van Driessche 1
1 Inorganic and Physical Chemistry, Ghent University, Ghent Belgium, 2 Department of Materials Science and Metallurgy, University of Cambridge, Cambridge United Kingdom, 3 , Zenergy Power GmbH, Rheinbach Germany
Show AbstractUntil now, YBa2Cu3Ox (YBCO) remains the material of choice in the production of long length coated conductors. The coated conductor design which is most promising is based on a metallic Ni-5%W tape with a La2Zr2O7 – CeO2 buffer structure on top. In this work, the deposition of YBCO coatings on single crystal (SrTiO3) and on buffered NiW substrates using piezoelectric ink-jet printing (Dimatix Materials Printer and Microfab single-nozzle) was investigated. The combination of a chemical solution with ink-jet printing gives important advantages over traditional deposition techniques (e.g. spincoating) such limited waste of the precursor solution, production in long lengths and the possibility to switch quite easily from depositing a coating to a multifilamentary superconductor. The precursor solutions we use for printing YBCO layers are based on a fluorine-free sol-gel system containing metal acetates and using water as the primary solvent. The absence of fluor in the precursor solution simplifies and shortens the heat treatment. To maintain stability in the precursors, the influence of chelating agents such as triethanolamine and EDTA was explored. This study was specifically concerned with the optimization of the ink rheology and printing parameters necessary to obtain a well textured YBCO coating. After deposition of the aqueous film, an appropriate heat treatment was applied. The resulting ceramic films were analysed with optical microscopy, SEM and XRD. Superconducting properties of the YBCO films were investigated.Research funded by EU project EFECTS (FP7-NMP-2007-SMALL-1 grant n°205854).
12:15 PM - L3.8
Reel-to-reel Continuous Simultaneous Double-sided Deposition of YBCO Coated Conductors.
Jie Xiong 1 2
1 Superconductivity Technology Center, Los Alamos National Lab, Los Alamos, New Mexico, United States, 2 State Key Laboratory of Electronic Thin Film and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, Sichuan, China
Show AbstractA reel-to-reel system which allows simultaneous deposition of double-sided long length epitaxial CeO2/YSZ/Y2O3 multi-buffer layers on biaxially textured Ni-5at.%W tape with direct-current (d.c.) reactive magnetron sputtering method is described. Deposition is accomplished through two opposite holes in the cavity by inverted cylindrical magnetron (ICM) sputtering guns. The films were characterized by means of x-ray diffraction (XRD), and atomic force microscope (AFM). The samples exhibited good epitaixal growth with c-axis perpendicular to the substrate surface for both sides. AFM observations revealed a smooth, dense and crack-free surface morphology. Biaxially textured buffer multilayers up to 100-m length could be fabricated with production speed of more than 2m/h. Epitaxial YBa2Cu3O7-δ (YBCO) films grown by d.c. sputtering technique on the short prototype CeO2/YSZ/Y2O3/NiW conductors yielded self-field critical current densities (Jc) as high as 1.5MA/cm2 at 77K. An Ic values of 280A/cm was obtained for double-sided YBCO coated conductors. These results demonstrate the strong potential of using double-sided method for the enhancing current carrying capability. Ongoing R&D is focused on the development of the method for high deposition rate, thicker YBCO layers and improved flux pinning centers.
12:30 PM - L3.9
HTS Films Deposited by Reactive Coevaporation for Low-cost Coated Conductors.
Brian Moeckly 1 , Viktor Glyantsev 1 , Jeong-uk Huh 1 , Vladimir Matias 2 , Chris Sheehan 2 , Yates Coulter 2
1 , Superconductor Technologies, Inc., Santa Barbara, California, United States, 2 Superconductivity Technology Center, Los Alamos National Laboratory, Los Alamos, New Mexico, United States
Show AbstractSecond generation (2G) high temperature superconducting (HTS) coated conductors remain expensive compared to conventional copper and aluminum wire. We believe that HTS films deposited by reactive coevaporation using cyclic deposition and reaction (RCE-CDR) represent the potentially lowest-cost approach for manufacture of 2G coated conductors. In the past we have adapted this technique for high-volume production of very high-yield, highly uniform, low-cost HTS films on single crystal substrates. This method also allows deposition of HTS films onto new low-cost, simplified textured templates developed at Los Alamos National Laboratory. These templates employ MgO layers grown by ion beam assisted deposition on top of Y2O3 layers deposited by solution deposition planarization onto flexible metallic alloy substrate tapes. We will discuss our measurements of the transport and materials properties of YBa2Cu3O7-δ films grown by RCE-CDR directly on the thin MgO layer of these simplified templates. These HTS films display out-of-plane crystallinity that rivals that of films grown on single-crystal substrates, and the in-plane alignment is excellent. These tapes exhibit critical current densities of several MA/cm2 at 77 K and self field for thin films, and thicker films support critical currents of several hundred amps/cm-width. We are also developing an RCE-CDR deposition system for production of long lengths of 2G HTS tape. We will report on the fabrication and properties of multi-meter lengths of HTS coated conductors produced in this system.
12:45 PM - L3.10
Round or low-aspect Ratio, High-temperature Superconducting Wires Based on Epitaxial Growth of YBCO Films on Structural, Single-crystal, Faceted Fibers (SSIFFS).
Sung Hun Wee 1 2 , Amit Goyal 1 , Eliot Specht 1 , Yuri Zuev 1 3 , Claudia Cantoni 1
1 Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States, 2 Department of Materials Science and Engineering, University of Tennessee, Knoxville, Tennessee, United States, 3 Department of Physics, University of Tennessee, Knoxville, Tennessee, United States
Show AbstractA potential route towards “round” or “low aspect ratio” wires having low ac-loss is developed via epitaxial growth of REBa2Cu3O7-δ (RE = rare earth elements including Y, REBCO) superconducting films on Structural, Single-Crystal, Faceted, Fibers (SSIFFS) which are long, flexible, low-aspect ratio, Al2O3 single-crystal templates with the crystallographic facets of an R-plane orientation. Single or multiple buffer layers including YSZ and CeO2 are deposited epitaxially on the R-plane facets formed on the fiber. High quality, REBCO films are then deposited epitaxially on R-plane facets of the fibers with such buffer stacks. For the first time, critical current density, Jc, higher than 2 MA/cm2 was demonstrated on R-plane faceted fibers made using the SSIFFS process. Detailed structural and superconducting properties for YBCO films grown on SSIFF templates will be presented.This research was sponsored by the U.S. DOE Office of Electricity Delivery and Energy Reliability - Advanced Cables and Conductors under contract DE-AC05-00OR22725 with UT-Battelle, LLC managing contractor for Oak Ridge National Laboratory.
L4: Flux-pinning I
Session Chairs
Amit Goyal
Kaname Matsumoto
Wednesday PM, April 07, 2010
Room 2005 (Moscone West)
2:30 PM - **L4.1
Artificial Pinning Center Technology: Control of Flux Pinning and Glass-liquid Transition.
Kaname Matsumoto 1
1 , Kyushu Institute of Technology, Kitakyushu Japan
Show AbstractBy evaluating vortex behaviors in the vortex liquid phase using a flux transformer experiment, it was concluded that the upper limit of Tg was determined by the loss of line tension of vortices. In addition, a question also arises as to what kind of pinning centers achieve the upper limit of Tg. In order to clarify this matter, the upper limit of Tg should be discussed based on experimental results on the GL transition. The upper limit of Tg is important also from technological points of view. Various types of artificial pinning centers were incorporated into YBCO coated conductors (CCs) to enhance their vortex pinning properties. It is true that the vortex pinning in CCs was improved, but superconductor applications would always expect higher and higher performance CCs. Therefore, the upper limit of the vortex pinning (the upper limit of Tg) should be clarified in order to set the final goal on the control of vortex pinning in CCs and to enhance the performance of CCs as much as possible. In this work, we discuss the optimizing pinning centers, critical temperature, and a matching field.
3:00 PM - **L4.2
Effect of Strain, BZO Content and the Incorporation of Double-perovskite-based Ta- and Nb- Oxide Nanostructures on Flux-pinning in Coated Conductors.
Amit Goyal 1 , Sung-hun Wee 1 , Eliot Specht 1 , Claudia Cantoni 1 , Yuri Zuev 1 , Yanfei Gao 1
1 Materials Science & Technology Division, Oak Ridge National Laboratory, Oak Ridge , Tennessee, United States
Show AbstractThe effect of strain on Tc, and Jc as a function of BZO content in REBCO based coated conductors will be presented. Data will be presented for films made using different techniques such as pulsed laser ablation, MOCVD and MOD. The effect of lattice-mismatch on self-assembly of columnar defects within YBCO films will also be presented. Using BaMO3-type additions, the lattice-mismatch was varied over a broad range of values by using different components for M such as Zr, Sn, Ce, etc. It is found that only a certain range of lattice mismatch is most amenable to self-assembly of columnar defects. Lastly, a new material or compound which is found to be very effective in forming self-assembled, columnar defects has been identified. These are double-perovskite based, Ba2RETaO6 and Ba2RENbO6 materials, where RE is a rare-earth. The lattice-mismatch of Ta and Nb-based, double perovskites is shown to be highly amenable to formation of such columnar defects. Massive improvement in flux-pinning is obtained via incorporation of such double perovskite-based, self-assembled columnar defects in REBCO films on coated conductors. This research was sponsored by the U.S. DOE Office of Electricity Delivery and Energy Reliability - Superconductivity Program for Electric Power Systems Advanced Cables and Conductors.
3:30 PM - L4.3
Enhanced Pinning in MOCVD-based Coated Conductors.
Venkat Selvamanickam 1 , Yimin Chen 2 , Goran Majkic 1 , Albert Guevara 1 , Ibrahim Kesgin 1 , Yangxin Zhang 1 , Shi Tuo 1 , Narayan Khatri 1 , Xin Tao 1 , Senthil Sambandam 2 , Andrei Rar 2 , Gene Carota 2 , John Dackow 2
1 Mechanical Engineering and Texas Center for Superconductivity, University of Houston, Houston, Texas, United States, 2 , SuperPower, Schenectady, New York, United States
Show AbstractCoated conductors based on Metal Organic Chemical Vapor Deposition (MOCVD) have now been produced in lengths exceeding one kilometer with a critical current performance levels of 300 A/cm. The performance of these coated conductors in high magnetic fields is important for several applications. Chemical doping especially based on Zr has been found to be an effective method to improve in-field performance of coated conductors. Recently, based on optimized process recipes, Zr-doped MOCVD-based coated conductors have been demonstrated in lengths of few hundred meters with uniform and effective pinning. In a field of 77 K, a critical current retention of 28% at B || c-axis and 17% retention in the minimum critical current orientation have been demonstrated with uniformity of about 3%. In addition to Zr content, the in-field performance at B || c is found to be very sensitive to the rare-earth content. Apart from improving the in-field performance at B || c, our work is focused on enhancements to the minimum critical current value as well as intermediate temperature performance. We are exploring multiple techniques to control the nanostructures created in the superconducting matrix to achieve our objectives. The presentation will summarize the latest developments in critical current and pinning behavior of high-performance MOCVD-based coated conductors.
3:45 PM - L4.4
Growth Dynamics and Pinning Properties of YBCO With Second Phase Additions.
Boris Maiorov 1 , D. Feldmann 1 , S. Baily 1 , H. Zhou 1 , J. Kennison 1 , P. Dowden 1 , S. Foltyn 1 , T. Holesinger 1 , L. Civale 1
1 , Los Alamos National Laboratory, Los Alamos, New Mexico, United States
Show AbstractOver the past years critical current density (Jc) in YBa2Cu3O7 (YBCO) films and coated conductors has steadily improved, mainly in the field dependence. Several of these pinning enhancement routes introduce nano-precipitates that are self-assembled. Angular dependent measurements are a key tool to identify and relate microstructure with vortex pinning and dynamics, both in YBCO with and without second phase additions. By changing the kinetics of the deposition in BaZrO3-doped YBCO we were able to change the proportions of pinning centers such as correlated and nano-particles inclusions. Also by changing the chemistry (amount and type of additions) we are able to affect the layered inclusions along the ab-planes that enhance Jc around this direction. These defects and the self-assembled c-axis defects act as a network of correlated defects resulting in better overall Jc. Results of the Jc enhancement as well as the pinning produced by different defect type and density will be presented, measured at different magnetic fields and temperatures that allow a better understanding of the vortex pinning nature.
4:30 PM - **L4.5
Exploring 3-D Landscaping of BaZrO3 Nanorods in YBa2Cu3O7-δ via Strain Engineering.
Judy Wu 1 , Javier Baca 1 2 , Rose Emergo 1 , Tim Haugan 2 , Paul Barnes 2
1 , University of Kansas, Lawrence, Kansas, United States, 2 , Air Force Research Laboratory, Wright-Patterson AFB, Ohio, United States
Show AbstractImpurity doping, such as BaZrO3 has shown remarkable enhancement of in-field critical current density in YBa2Cu3O7-δ (YBCO) films as consequence of formation of high density of BaZrO3 nanorods (BZO-NRs) aligned along the c-axis or film normal. The benefit of the aligned BZO-NRs is limited mostly when applied magnetic fields (H) is parallel to the c-axis. To extend the benefit to all orientations of H-fields, schemes in engineering strains on YBCO lattice have been explored to generate 3D landscaping of BZO-NRs. We have found that substrate modification by either vicinal cut or nanoscale template insertion can provide controllable tuning of the BZO-NRs alignment. The 3D landscaping of BZO-NRs is favorable as confirmed by significantly enhanced critical current density in the entire range of magnetic field orientations.
5:00 PM - **L4.6
Enhanced Flux Pinning in MOD YBCO Films With BaMO3 (M= Ce, Sn, Zr) Nanoparticle Inclusions.
Sang-Im Yoo 1 2 , Geo-Myung Shin 1 2 , Soon-Mi Choi 1 2
1 Department of Materials Science and Engineering, Seoul National University, Seoul Korea (the Republic of), 2 , Research Institute of Advanced Materials (RIAM), Seoul Korea (the Republic of)
Show AbstractBaMO3 (M = Ce, Sn, Zr) nanoparticles in MOD-processed YBa2Cu3O7-δ (YBCO) films on the SrTiO3 substrates were found very effective for the enhancement of critical current densities, Jc in high magnetic field. YBCO films with thickness up to 2.5 μm were prepared using Y and Cu fluorine-free sources. Two different nominal compositions of Y : Ba : Cu = 1 : 2 : 3 and 1 : 1.5 : 3 were employed for this study. The degradation in Jc with increasing film thickness over 1 μm was greatly improved by using Ba-poor composition since better in-plane texture of YBCO film could be achieved. Compared with undoped YBCO films, YBCO films containing the BaMO3 nanoparticles exhibit significantly higher in-field Jc values at 65 and 77 K. Thus, in-field magnetic Jc values over 0.3 MA/cm2 at 77 K for H = 1 T and also at 65 K for H = 3 T, which are about three times higher values than those of undoped YBCO films, are obtainable from BaZrO3- and BaSnO3-doped YBCO films. Drastically improved pinning force densities in the BaMO3-doped YBCO films are also found. Detailed effects of BaMO3 nanoparticle inclusions on the in-plane texture, microstructure, and flux pinning properties of the YBCO films will be presented for a discussion. This research was supported by a grant from Center for Applied Superconductivity Technology of the 21st Century Frontier R&D Program funded by the Ministry of Education, Science and Technology, Republic of Korea.
5:30 PM - L4.7
Growth of TFA-YBCO Nanocomposite Films With Added Preformed Nanoparticles.
Alberto Pomar 1 , F. Martinez-Julian 1 , S. Ricart 1 , A. Palau 1 , J. Arbiol 1 , F. Sandiumenge 1 , L. Perez-Mirabet 2 , R. Yanez 2 , J. Ros 2 , X. Obradors 1 , T. Puig 1
1 Institut de Ciencia de Materials de Barcelona, ICMAB-CSIC, Bellaterra Spain, 2 Department de Quimica Inorganica, UAB, Bellaterra Spain
Show AbstractIn the last years vortex pinning capabilities of coated conductors have been enhanced by the introduction of controlled secondary phases in the YBCO matrix. Generally, the strategy has been to use the in-situ approach where the secondary phase is formed during the same thermal treatment as the YBCO film. In that case, density and distribution of the secondary phase is controlled by modifying the growth parameters. However, tuning the size of the nanoparticles inside the YBCO matrix has been proved to be a very tough task. Chemical solution deposition techniques offer a different option: the ex-situ approach where preformed nanoparticles are added to the YBCO starting precursor solution, Here we will present our efforts in this approach to achieve enhanced and controlled pinning properties in YBCO.Therefore, nanoparticles have been synthesized as colloidal suspensions in organic, alcoholic and aqueous solvents using a reduction and precipitation process with nanoparticles concentrations in solution in the range 10-2-10-6M. Subsequently, we have grown YBCO thin films by the trifluoroacetates route with added preformed nanoparticles. An initial study of nanoparticles solution compatibility with YBCO TFA solution was required. The influence of both oxide and metallic nanoparticles in the YBCO growth will be analyzed . Microstructure of the nanocomposite YBCO films has been characterized by x-ray diffraction, SEM and TEM. Superconducting properties have been measured by both inductive (SQUID) and transport techniques. We will assess the role of size and density of the nanoparticles in the YBCO nanocomposites performances and, in particular, in the vortex pinning behaviour. Finally, we will discuss the introduction of magnetic nanoparticles inside the YBCO matrix to achieve magnetic pinning.We acknowledge financial support from MEC (MAT2008-01022), Consolider Nanoselect, Generalitat de Catalunya (Pla de Recerca SGR-770 and XaRMAE) and EU (HIPERCHEM and NESPA)
5:45 PM - L4.8
Interaction Between Solution Derived BaZrO3 Nanodot Interfacial Templates and YBa2Cu3O7 Films Leading to Enhanced Critical Currents.
Patricia Abellan 1 , Felip Sandiumenge 1 , Marie-Jo Casanove 2 , Marta Gibert 1 , Anna Palau 1 , Teresa Puig 1 , Xavier Obradors 1
1 , ICMAB CSIC, Bellaterra, Catalonia, Spain, 2 , CEMES CNRS, Toulouse France
Show AbstractTo elucidate the origin of enhanced critical current density found in solution derived YBa2Cu3O7 deposited on LaAlO3 (001) substrates decorated with self assembled BaZrO3 nanodots, the nanostructured interface is thoroughly investigated by high resolution transmission electron microscopy. The nanodots appear fully relaxed relative to the substrate, and their three dimensional epitaxy with the embedding film is highly coherent. The high interfacial coherence is promoted by continuity of BaO atomic layers through the YBa2Cu3O7 and BaZrO3 crystal structures, thus minimizing bonding between dissimilar atomic layers across the interface. Buried nanodots may undergo slight tilts (1.5 to 2 degrees), very likely to minimize the chemical contribution to the interfacial energy with the substrate. Such tilts cause a drag force on the adjacent, strongly bonded, (001)YBCO planes resulting in a severe distortion of the lattice on a scale length of a few unit cells around the tilted nanodots. On a larger scale length (several tens of nanometers), diffraction contrast images reveal columnar like diffuse long range strains emanating from the interfacial nanodots, running approximately parallel to the film normal. As a significant finding, the present results demonstrate that the template-film interaction does not involve dislocation emission but is accompanied by particular columnar-like propagation of elastic strains. The topological distribution of perturbed regions within the superconducting films qualitatively explain the overall enhancement of the critical current density in the whole angular range, which becomes particularly higher when the magnetic field is aligned with the cYBCO-axis.
Symposium Organizers
Sung Hun Wee Oak Ridge National Laboratory
Venkat Selvamanickam University of Houston
Quanxi Jia Los Alamos National Laboratory
Hideo Hosono Tokyo Institute of Technology
Hai-Hu Wen Institute of Physics, CAS
L5: Characterization of HTS Materials and Development of Templates for Coated Conductors
Session Chairs
Boris Maiorov
Vyacheslav Solovyov
Thursday AM, April 08, 2010
Room 2005 (Moscone West)
9:30 AM - **L5.1
Epitaxy of Textured YBCO on Technical Oxide Buffers.
Vyacheslav Solovyov 1 , Qiang Li 1 , Zhou Juan 1 , Katherine Develos-Bagarinao 2
1 Condensed Matter and Materials Science, Brookhaven Naational Laboratory, Upton, New York, United States, 2 , National Institute of Advanced Industrial Science and Technology, Tsukuba Japan
Show AbstractThe second generation (2G) high-temperature superconducting wire is comprised of several epitaxial layers: two or three oxide buffer stack topped by highly oriented Y1Ba2Cu3O7 (YBCO) film. Such a complex arrangement presents an optimization challenge due to a very large number of possible variables. We argue that the optimization process can be simplified by indentifying factors affecting nucleation and early growth stages of YBCO. The optimum processing environment ensures fast formation of dense array of epitaxial YBCO nuclei. Fast nucleation of epitaxial YBCO is important because it inhibits formation of non-superconducting phases, such as BaCuO2, which are detrimental for the conductor performance. One of critical factor is the substrate surface. Most of the technical buffers, used in 2G wires today, are thin (<100 nm) columnar Vollmer-Weber films of refractory oxides, such as CeO2, LaMnO3, SrTiO3. Structure of these buffers can be described by two independent parameters: lateral grain size and the average film density. To illustrate influence of these parameters on nucleation of epitaxial YBCO we present results of the study of YBCO formation during ex-situ processing using ceria buffers of RABiTS tape and during MOCV growth on IBAD LaMnO3 buffer on Hastelloy tape. Atomic force microscopy and synchrotron X-ray diffraction are used to obtain information on spatial distribution and structure of epitaxial YBCO on the early stages of growth. X-ray diffraction data are analyzed to show that YBCO universally nucleates as a disordered perovskite. Atomic force microscopy is used to locate sites of preferred attachment of YBCO nuclei on IBAD tape. To identify the nature of the nucleation centers active in YBCO nucleation on a RABiTS tape, we compare nucleation kinetics and performance of YBCO layers deposited by the metal-organic process on a standard RABiTS tape and on ceria buffers with well-controlled structure and surface morphology. It is shown, that the best buffers exhibit high YBCO nucleation rate and produce YBCO nuclei with the least amount of cation disorder. High YBCO nucleation rate is associated with high density of threading dislocation outcrops, suggesting a strategy for the buffer optimization.This work has been performed under Contract No. DE-AC02-98CHI-886 with the U. S. Department of Energy, Office of Electricity Delivery and Energy Reliability.
10:00 AM - L5.2
Relationship of Structure and Properties and Real Time Process Control for ReBCO-based Second-generation High Temperature Superconductors.
Andrei Rar 1 , Yimin Chen 1 , John Dackow 1 , Sofia Soloveichick 1 , Yi-Yuan Xie 1 , Venkat Selvamanickam 2
1 , SuperPower Inc., Schenectady, New York, United States, 2 , University of Houston, Houston, Texas, United States
Show AbstractIn the past year SuperPower has continued to increase self-field and in-field critical current of production-scale second-generation (2G) high temperature superconductor (HTS) wires, as well as increasing the piece lengths, critical current and processing speeds of the wire. SuperPower has demonstrated word-record wire performances in both long and short lengths, and has further improved in-field properties by BaZrO3 doping and has transferred production of the both the doped and high amperage films from R&D to manufacturing processes. This transition has created new challenges for characterization and quality control at different production steps. The steady increase in the wire length and production volume has required integration of highly automated characterization and quality control tools into the manufacturing process and quick feedback on the quality of the current run to the production team. Use of BaZrO3 doped films has required more detailed information about the structure and composition of the sample. In this presentation we will discuss the current status of characterization and quality control for our manufacturing and development efforts. We will discuss the current status of the relationship between sample structure and performance and the application of real time characterization systems for process monitoring.
10:15 AM - L5.3
Examination of Through-thickness/Through-time Phase Evolution During MOD-type REBCO Precursor Conversion Using Raman Microscopy.
Zhijun Chen 1 , Victor Maroni 1 , Dean Miller 1 , Xiaoping Li 2 , Martin Rupich 2 , Roeland Feenstra 3
1 , Argonne National Laboratory, Argonne, Illinois, United States, 2 , American Superconductor, Devens, Massachusetts, United States, 3 , Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States
Show AbstractA sampling and analysis method has been developed that permits through-thickness/time-dependent examination of quenched REBCO coated conductor samples prepared by processing of a metal-organic deposited (MOD) REBCO precursor on a RABiTS-based template. REBCO films having a final thickness of 1.2 um and a composition of Y(1)Dy(0.5)Ba(2)Cu(3)O(6+x) were fabricated by two routes. In one route, enough precursor was applied to the substrate in a single coating operation to produce the full 1.2 um thickness--henceforth referred to as the single layer (SL) film. In the second route, the 1.2 um thickness was achieved by two equivalent (0.6 um) sequential precursor depositions with an intermediate heat treatment that decomposed the first deposition layer--henceforth referred to as the double layer (DL) film. Specimens of each film type were subjected to the normal temperature ramp and reaction temperature (TR) used in American Superconductor’s MOD coated conductor production furnace, then quenched at selected time intervals between zero time at TR and the time required to complete the precursor conversion. The phase chemistry of the resulting film specimens was examined by milling a slope from the substrate to the film surface, followed by Raman microscopy examination along the slope. Key findings were (1) the presence of an evolving CuO, Cu2O, Ba-Cu-O, (Y,Dy)2Cu2O5, REBCO phase mix through the precursor conversion stages (i.e., through time), (2) the observation that the SL and DL films reacted to completion at about the same rate and came to a similar final composition, and (3) the detection of some residual (unreacted) Ba-Cu-O phases near the top of both the SL and DL films. The influence of the observed phase evolution and associated microstructure on wire performance for the SL and DL films will be presented and discussed.[Research done at the Argonne National Laboratory and at the Oak Ridge National Laboratory was sponsored by the U.S. Department of Energy (DOE), Office of Electricity Delivery and Energy Reliability, as part of a DOE program to develop electric power technology, under contract DE-AC02-06CH11357 between UChicago Argonne, LLC and the USDOE and under contract DE-AC05-00OR22725 between U.T.-Battelle, LLC and the USDOE.]
10:30 AM - L5.4
Breaking the Barrier for Thickness: Influence and Control of the ``Interlayer” on Texture in Multi-coat TFA-MOD Coated Conductors.
Dean Miller 1 , Vic Maroni 1 , Nestor Zaluzec 1 , Zhijun Chen 1 , Kayla Cooley 1 , Xiaoping Li 2 , S. Sathyamurthy 2 , Marty Rupich 2 , Ron Feenstra 3
1 , Argonne National Laboratory, Argonne, Illinois, United States, 2 , American Superconductor Corporation, Devens, Massachusetts, United States, 3 , Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States
Show AbstractOne important approach to improving the performance of rare-earth cuprate superconductor (REBCO) coated conductors is to increase the thickness of the conductor layer to increase current-carrying capability. However, the performance of such conductors generally does not increase proportionally to thickness, limiting the effectiveness of this approach. In MOD-based REBCO coated conductors produced by multi-coat approaches, a chemically segregated “interlayer” that forms between coating layers can limit performance. We have explored the nature of this “interlayer” in double-coat MOD films, focusing on its influence for both growth and texture. We show that the interlayer is both a physical and chemical barrier to the growth of REBCO, limiting performance by degrading texture as growth proceeds across the interlayer. Through electron beam imaging and chemical mapping, we identified a mechanism by which the growing REBCO penetrates the interlayer that also provides an explanation for degraded texture above the interlayer. Through our understanding of the effect and nature of the interlayer, mitigation strategies have been developed and are currently being explored. The critical aspects of each of these components will be presented and discussed.****Research sponsored by the U.S. DOE, Office of Electricity Delivery and Energy Reliability Advanced Cables and Conductors, under contract DE-AC02-06CH11357. The Electron Microscopy Center at Argonne is supported by the Office of Science.
10:45 AM - L5.5
The Significance and Systematic Behavior of ab-plane Pinning Variations in a Practical Length Wire Fabricated by the MOD / RABiTS Process.
James Coulter 1 , Jeffry Willis 1 , Leonardo Civale 1 , Doan Nguyen 1 , Terry Holesinger 1 , Martin Rupich 2
1 Superconductivity Technology Center, Los Alamos National Laboratory, Los Alamos, New Mexico, United States, 2 , American Superconductor, Devens, Massachusetts, United States
Show AbstractCoated conductors with lengths practical for applications from the Rare Earth, RE123 oxide materials system are being fabricated world wide. At this point in wire development, unintentional process variations result in critical current (Ic) variations along the length of the wires. These variations and their in-field behaviors can determine the suitability of a particular wire for use in power applications. The resulting uncertainty in performance necessitates additional critical current characterization to determine both the cause and effect of the variations. The wire characterization effort at Los Alamos National Laboratory has developed the apparatus and methods to identify and characterize Ic variations along the length of intact, practical coated conductors. Presently the apparatus is limited to Ic(H||c) measurements as a function of position. An Ic(H||ab) capability is in development and has achieved greater significance as our industrial collaborator American Superconductor recently identified H||ab plane Ic variations observed in wires fabricated by the MOD / RABiTS process to be of interest. These variations were confirmed by LANL to exist in a 20 m wire. As a step towards understanding the variations, an extensive piece-wise study of Ic(75 K, H, angle) was performed on short samples cut from the wire for which alpha, the power law coefficient of the field dependence, is used to quantitatively compare the field dependence over the range of H||ab plane Ic variations. We will briefly describe the status of position-dependent characterization, present results of the studies, and show the relevance of the methods and results to applications and further characterization development.
11:30 AM - L5.6
The Impact of Edge-Barrier Pinning in Superconducting Thin Films.
Wesley Jones 1 , Paul Barnes 1 , Matthew Mullins 1 , Francisco Baca 1 , Rose Emergo 1 , Timothy Haugan 1
1 Propulsion Directorate, Air Force Research Laboratory, Wright Patterson AFB, Ohio, United States
Show AbstractIt has been previously suggested that edge-barrier pinning might cause the critical current density (Jc) measured in bridged superconducting films to increase as the bridges are narrowed. Subsequent work by others suggests that this edge-barrier effect does not impact bridges of micron size or larger. However, we provide a theoretical assessment and supporting experimental data that suggests edge-barrier pinning can significantly enhance Jc for bridges of a few microns or even tens of microns in width, skewing comparison of Jc amongst institutions using different size bridges. In the present study, bridges in YBa2Cu3O7-δ (YBCO) thin films were repeatedly narrowed to avoid issues of sample to sample variation. Bridge widths starting at 500 µm and 50 µm were patterned by photolithography. Subsequent narrowing above 50 µm was performed by photolithography and below 50 µm was by focused ion beam milling. Transport Jc (77K)- and room temperature sensitivity was determined after each bridge size. Theoretical implications of the narrow bridge effect on Jc(H) and Jc(T) curve shapes will additionally be discussed as not simple scalar changes. This study suggests that the bridge width of the sample has to be taken into consideration as well as the film thickness for proper comparison of Jc.
11:45 AM - L5.7
Dynamic Studies on the Influence of Strain on Superconducting Properties Using Piezoelectric Substrates.
Ruben Huehne 1 , Sascha Trommler 1 , Kazumasa Iida 1 , Patrick Pahlke 1 , Thomas Thersleff 1 , Ludwig Schultz 1 , Bernhard Holzapfel 1
1 Institute for Metallic Materials, IFW Dresden, Dresden Germany
Show AbstractIt is known that the application of strain has a significant influence on the functional properties of superconducting materials. Typically, thin films are prepared on substrates with a different lattice misfit inducing a biaxial tensile or compressive strain to study this effect. Unfortunately, this approach is often restricted to very thin films. Furthermore, it is difficult to correlate strain and superconductivity directly, as the preparation conditions and the resulting microstructure may severely affect the superconducting properties. An alternative approach is the preparation of superconducting films on single crystalline piezoelectric substrates enabling a dynamical variation of the induced strain by applying an electric field on the substrate. This approach is used to study the strain dependence of superconducting properties in different materials. Therefore, thin epitaxial YBCO, La2-xSrxCuO4 and BaFe2-xCoxAs2 films were prepared on piezoelectric (001) Pb(Mg1/3Nb2/3)0.72Ti0.28O3 (PMN-PT) substrates. Depending on the lattice parameter of these materials, additional buffer layers are required to achieve an epitaxial growth of the superconductor on these substrates. The structural as well as the electrical properties of the grown films were characterized in detail. Finally, results on the influence of strain on superconducting properties like the transition temperature will be presented for these materials using dynamic investigations.
12:00 PM - L5.8
Development of Simplified Architectures to Improved IBAD-MgO/MOCVD-REBCO Coated Conductors.
Mariappan Paranthaman 1 , Tolga Aytug 1 , Claudia Cantoni 1 , S. Wee 1 , Amit Goyal 1 , Yuri Zuev 1 , Venkat Selvamanickam 2 , Liliana Stan 3 , Quanxi Xia 3
1 , Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States, 2 , SuperPower, Schenectady, New York, United States, 3 , Los Alamos National Laboratory, Los Alamos, New Mexico, United States
Show AbstractThe SuperPower/ORNL high performance LMO-enabled, high temperature superconducting tape (LMO e-HTS) is a robust, high-current second-generation superconducting wire. This superconducting wire with five-layer architecture of Ni-alloy/Al2O3/Y2O3/IBAD-MgO/Homoepi-MgO/LMO can be fabricated at high throughput rates using reel-to-reel processes. To reduce cost and complexity, as well as associated mechanical and reliability concerns, it is highly desirable to reduce the number of buffer layers. This was accomplished by utilizing LMO as the multi-functional material and eliminated the need for homoepi-MgO layer. Further, we have also developed process conditions to planarize the mechanically polished Hastelloy substrates using solution Al2O3 layers and demonstrated the growth of robust IBAD-MgO/LMO templates. We will also discuss in detail about the results achieved towards planarization of the substrate using solution layers. Research sponsored by the US Department of Energy, Office of Electricity Delivery and Energy Reliability – Advanced Cables and Conductors.
12:15 PM - L5.9
Single Ce0.9Zr0.1O2-δ Buffer Architecture Coated Conductors Based on MOD Method.
Valentina Roxana Vlad 1 , Alberto Pomar 1 , Anna Llordes 1 , Anna Palau 1 , Teresa Puig 1 , Xavier Obradors 1 , Alexander Usoskin 2 , Ruben Huehne 3 , Bernhard Holzapfel 3
1 , Institut de Ciència de Materials de Barcelona, ICMAB-CSIC, Campus UAB, 08193, Bellaterra, Catalonia, Spain, 2 , European High Temperature Superconductors GmbH & Co. KG, Alzenau Germany, 3 , IFW Dresden,Helmholtzstrasse 20, D-01069, Dresden Germany
Show Abstract(00l) oriented ceria layer is now widely used as a template for growth of epitaxial high-temperature superconductor, Y1Ba2Cu3O7-δ, which is a critical component of so-called second generation superconductors. In the present work, single thin Ce0.9Zr0.1O2-δ (CZO) buffer layers were prepared using Metal-Organic Decomposition (MOD) starting from a solution containing Ce(III), Zr(IV) acetylacetonates salts. This precursor solution was spin coated on different substrates: YSZ single crystals and also on ABADYSZ/Stainless Steel (SS) substrates. Several characterization methods were used to see the structure and the morphology of these samples: Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD) and Reflection High Energy Electron Diffraction (RHEED). The RHEED measurements confirmed the results gave by the AFM, in which good flat surface with large grains and small roughness was observed. We have demonstrated the growth of high performance MODYBCO films using this architecture with a critical current density Jc of 5.2 MA/cm2 (sf, 77 K) achieved on YSZ single crystal and 1.7 MA/cm2 on SS. Also, in order to enhance the Jc characteristics under magnetic fields, we have prepared YBCO coated conductors (CCs) with BaZrO3 (BZO) artificial pinning centres by modifying the precursor solution. We acknowledge the financial support from MICINN (MAT2008-01022, NAN2004-09133-CO3-01, Consolider NANOSELECT and FPU), Generalitat de Catalunya (Catalan Pla de Recerca 2009-SGR-770 and XaRMAE), and EU (HIPERCHEM and NESPA).
12:30 PM - L5.10
Optimization of Ion Assist Beam Deposition of Magnesium Oxide Template Films During Initial Nucleation and Growth.
James Groves 1 2 , Vladimir Matias 2 , Raymond DePaula 2 , Liliana Stan 2 , Robert Hammond 3 , Bruce Clemens 1
1 Materials Science and Engineering, Stanford University, Stanford, New Mexico, United States, 2 Superconductivity Technology Center, Los Alamos National Laboratory, Los Alamos, New Mexico, United States, 3 Geballe Laboratory for Advanced Materials, Stanford University, Stanford, California, United States
Show AbstractIon Beam Assisted Deposition (IBAD) of biaxially textured Magnesium Oxide (MgO) for depositing high-performance second-generation high-temperature superconductor wires has been successfully implemented by industry over the past few years. However, the fundamental mechanism of IBAD MgO nucleation and growth is not well understood. A detailed study of the initial nucleation and growth of MgO is presented here with emphasis on the effects of various nucleation surfaces and different ion-to-molecule arrival ratios and an improved model for the mechanism is presented. Use of a novel in-situ quartz crystal microbalance coupled with time-correlated in-situ Reflected High-Energy Electron Diffraction (RHEED) and ex-situ Transmission Electron Microscopy (TEM) have revealed different stages of IBAD texture development. This talk focuses on the initial stage during which the texture is formed through a process analogous to solid phase recrystallization. Changes in the nucleation surface type and ion-to-molecule ratio influences the development of texture and can be used in a more practical sense to improve processing schemes for coated conductors.
12:45 PM - L5.11
Properties of YBCO/IBAD MgO Coated Conductors Based on Y-Al-O Grown by Polymer-assisted Deposition.
Liliana Stan 1 , Hongmei Luo 2 , Yingying Zhang 1 , Boris Maiorov 1 , Raymond DePaula 1 , Eve Bauer 3 , Anthony Burrell 3 , Thomas McCleskey 3 , Quanxi Jia 1
1 Superconductivity Technology Center, Los Alamos National Laboratory, Los Alamos, New Mexico, United States, 2 Department of Chemical Engineering, New Mexico State University, Las Cruces, New Mexico, United States, 3 Materials Chemistry, Los Alamos National Laboratory, Los Alamos, New Mexico, United States
Show AbstractSimplifying the fabrication process of HTS coated conductors (CCs) can increase the production yields and reduce the production cost. By using Y-Al-O composite instead of Y2O3 and Al2O3 separate layers and growing the LaMnO3 buffer directly on the IBAD MgO, the number of non-superconducting layers between the polycrystalline metal substrate and the YBCO is reduced to three. Moreover, growing the Y-Al-O by polymer-assisted deposition (PAD) can further simplify the fabrication process by eliminating the electropolishing step. The PAD Y-Al-O provides the smooth surface necessary for IBAD texturing. Experimental results on film synthesis, morphology, microstructure and superconducting properties of the resulting HTS CC will be presented.
L6: Flux-pinning II
Session Chairs
Timothy Haugan
Haiyan Wang
Thursday PM, April 08, 2010
Room 2005 (Moscone West)
2:30 PM - **L6.1
Simultaneously Enhancing Intragranular and Intergranular Currents of Y-Ba-Cu-O Coated Conductors With Nanoparticle Additions.
Timothy Haugan 1 , Joshua Reichart 1 , Matthew Mullins 1 , Francisco Baca 1 , Eric Brewster 1 , John Olds 1 , Paul Barnes 1 , Haiyan Wang 2
1 AFRL/RZPG, U.S. Air Force Research Laboratory, Wright-Patterson AFB, Ohio, United States, 2 Dept. of Elect. and Comp. Eng., Texas A&M Univ., College Station, Texas, United States
Show AbstractAddition of nanosize defects to YBa2Cu3O7-δ (YBCO) coated conductors are being studied worldwide, to enhance flux pinning and the critical current density (Jc) inside grains (intragranular). Examples of nanosize defects include 1-dimensional (1-D) such as nanoparticles or chemical substitutions, two-dimensional (2-D) such as nanorods or grain boundaries, and three-dimensional (3-D) which combine various defects. In addition to improving intragranular currents, it is also of interest to increase current flow across misoriented grains (intergranular), which affect the performance of long length conductors. However methods to increase intergranular current flow have focused thus far mostly on chemical additions or substitutions. In this paper, on-going studies to increase both the intragranular Jc and intergranular Jc of YBa2Cu3O7-δ (YBCO) coated conductors with nanoparticle additions will be described. Interestingly, we have found that optimized nanoparticle additions can strongly improve both intragranular and intergranular current flows, simultaneously. Nanoparticles with varying structure including nanorods were incorporated by pulsed laser deposition of (M/YBCO)N multilayer and (YBCO)1-xMx single-target films, with M additions including insulators Y2BaCuO5, Y2O3 and BaZrO3, magnetic phases including SrRuO3, Y3Fe5Oy and BaFe12Oy, and others. Extensive testing and optimization of Jc has been done for each YBCO+M system including varying the deposition temperature, layer parameters, and volume % additions from 0-20 %. Unique and unexpected trends of intragranular Jc(H,T,theta) were observed for each YBCO+M system, also depending on the exact film microstructures. Using Y-Ca-Ba-Cu-O insulating nanoparticles, intergranular grain boundary Jc increased 2x to 40x compared to YBCO for [001] and [001] tilts from 4° to 36°. Possible mechanisms for increasing intergranular current flow across technologically important low-angle grain boundaries < 10° will be discussed, and correlated with compressive-strain studies of YBCO films deposited on SrTiO3 bicrystals. Microstructural and superconducting properties will be summarized, including analysis by TEM and SEM. This work supported by – AFRL Propulsion Directorate and the Air Force Office Scientific Research (AFOSR)
3:00 PM - L6.2
Multifunctional, Phase-separated, Nanostructured Cap Buffer Layers for Improved Flux-pinning in YBa2Cu3O7-δ-based Coated Conductors.
Junsoo Shin 1 , Sung Hun Wee 1 2 , Claudia Cantoni 1 , Yuri Zuev 1 , Amit Goyal 1
1 , Oak Ridge National Lab., Oak Ridge, Tennessee, United States, 2 , University of Tennessee, Knoxville, Tennessee, United States
Show AbstractOrdered, epitaxial, surface decoration of controllable nanostructures can result in reproducible generation of columnar defects within superconducting films. Phase separated, epitaxial, nanostructured films comprised of BaTiO3 (BTO) + CoFe2O4 (CFO) and LaMnO3 (LMO) + MgO nanocomposites have been developed as potential multifunctional cap buffer layers for improved flux-pinning in YBa2Cu3O7-δ (YBCO) films. All films were deposited by pulsed laser deposition. The CFO or LMO fraction and growth temperature were identified as key factors to determine the areal number density and mean diameter of CFO or LMO nanocolumns. Compared to the reference sample grown on pure BTO or pure LMO cap layer by PLD, the YBCO films grown by PLD on BTO+CFO or LMO+MgO cap layers have a remarkable improvement in isotropic flux-pining and consequently, Jc, over the entire field and angular regime at 77K. TEM analysis confirmed the presence of a very defective YBCO layer containing a high density of randomly distributed defects at the interface area, induced by nanostructural modulation on the surface of BTO+CFO or LMO+MgO composite cap layer. Detailed morphological features of BTO-CFO and LMO+MgO nanocomposite films with different CFO or LMO additions, and superconducting properties for YBCO films grown on nanocomposite cap layers will be discussed in this presentation. This research was sponsored by the U.S. DOE Office of Electricity Delivery and Energy Reliability - Superconductivity Program for Electric Power Systems Advanced Cables and Conductors.
3:15 PM - L6.3
Engineered Nanostructures by Nanolithography Techniques on YBCO Films Grown by Chemicals Methods. A Promising Method for Improving and Controlling Flux Pinning.
Carlos Monton 1 , Anna Palau 1 , Jone Zabaleta 1 , Roberto Luccas 1 , Xavier Granados 1 , Narcis Mestres 1 , Xavier Obradors 1 , Teresa Puig 1
1 , Institut de Ciencia de Materiales de Barcelona, CSIC, Bellaterra, Barcelona, Spain
Show AbstractHigh critical current YBCO coated superconductors are nowadays a reality. We have developed experience in generating YBa2Cu3O7 (YBCO) films and coated conductors by chemical solution deposition (CSD) capable to carry current densities in the range of 3 to 4 MA/cm2 (at 77K and H=0). However their application in most power devices still depend on understanding vortex pinning mechanisms to control and improve vortex pinning capabilities at high magnetic fields and temperatures. For that purpose, by means of high resolution nanolithography techniques like Focused Ion Beam (FIB), Electron Beam Lithography and Nanoindentation, we have explored different artificial arrays of nano-pinning sites. We observe that channels performed by FIB on the superconducting film provide very effective pinning properties, when an external current is applied parallel to them. In addition, vortex visualization of these nanofabricated films using Bitter magnetic decoration has revealed that FIB channels introduce linear order in the vortex lattice. Additionally, vortex depinnig can be controlled by patterning FIB asymmetric pinning potentials which consist of arrays of triangular anti-dots. These arrays induce enhanced asymmetric pinning properties which depend on the current and applied magnetic field orientations. In another approach, we have explored the use of nanoindentation to induce pinning sites by generating nano-channels on the substrate before growing the YBCO film. As a result transport measurements show that pinning properties of the superconducting film are also improved. Consequently, our work demonstrates that the mentioned high resolution nanolithography techniques are very promising tools to analyze the vortex pinning mechanisms of high temperature superconductors and YBCO superconducting films. The analysis of the described systems, with a very well controlled geometry, enables us to manipulate and gather knowledge on vortex motion in the mentioned samples.
3:30 PM - L6.4
Ordered Arrays of Magnetic Artificial Pinning Centers in Superconducting Films via Nanoporous Anodic Alumina.
Rafael Dinner 1 , Adam Robinson 2 , Judith MacManus-Driscoll 1 , Mark Blamire 1
1 Department of Materials Science, University of Cambridge, Cambridge United Kingdom, 2 Nanoscience Centre, University of Cambridge, Cambridge United Kingdom
Show AbstractWe have fabricated large-scale arrays of artificial pinning centers (APCs) in niobium films using self-assembled arrays of nanopores in alumina templates. The templates are sputtered and anodized directly on the superconducting films, and act as a mask for ion milling of the superconductor. The resultant holes through the superconductor serve as ideal APCs, increasing the critical current (Jc) by a factor of 50, with additional pinning at the matching magnetic field calculated from the APC density. The fabrication process is reliable and scalable, allowing us to create >1010 pores over centimeters of film. The pore density can be adjusted to achieve matching fields of 0.05-1 T. We will discuss how this technology might be applied to high temperature superconductors.The niobium model system allows us to address open questions in the field of artificial pinning engineering. First, we examine whether magnetic inclusions can further improve Jc over ideal insulating inclusions, as suggested by recent theoretical and experimental work [1, 2]. We isolate the effect of magnetism on pinning by measuring Jc before and after evaporating cobalt inclusions into the pores. We find that Jc is affected by the magnetization of the inclusions, but not enhanced as the Lorentz force reduction theory predicts [1].We can also control the exact placement of the APCs by seeding the pore formation, using FIB to indent the aluminum surface prior to anodization. We then study the influence of the APC lattice geometry on Jc. Transport measurements show that below the first matching field, randomly placed APCs are more effective than ordered lattices.[1] M. G. Blamire, R. B. Dinner, S. C. Wimbush and J. L. MacManus-Driscoll, "Critical current enhancement by Lorentz force reduction in superconductor-ferromagnet nanocomposites", Supercond. Sci. Technol. 22 025017 (2009).[2] R. B. Dinner, S. Sahonta, R. Yu, N. A. Stelmashenko, J. L. MacManus-Driscoll and M. G. Blamire, "Superconductor-ferromagnet nanocomposites created by co-deposition of niobium and dysprosium", Supercond. Sci. Technol. 22 075001 (2009).This work was supported by the UK EPSRC (grant number E011020) and Hughes Hall, Cambridge.
3:45 PM - L6.5
Further Functionalization of LaMnO3: Flux Pinning Enhancements in YBCO Films Through Phase Separated, Self-assembled LaMnO3-MgO Nanocomposite Films.
O. Polat 2 1 , Tolga Aytug 1 , M. Paranthaman 1 , K. Leonard 1 , A. Lupini 1 , S. Pennycook 1 , H. Meyer 1 , K. Kim 1 , X. Qiu 1 , S. Cook 1 , J. Thompson 2 , D. Christen 1 , A. Goyal 1 , X. Xiong 3 , V. Selvamanickam 3
2 , University of Tennessee, Knoxville, Tennessee, United States, 1 , Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States, 3 , SuperPower, Inc., Schenectady, Tennessee, United States
Show AbstractTechnological applications of high temperature superconductors (HTS) require high critical current density, Jc defects through creative processing. In this work, we generated correlated disorder for strong vortex pinning in YBa2Cu3O7-δ (YBCO) films by replacing the standard LaMnO3 (LMO) cap buffer layers with LMO:MgO composite films on ion beam assisted deposited MgO templates. The added volume percentages (vol.%) of MgO mixed with the LMO are 5%, 25%, 50%, and 75%. The microstructural analysis of such films revealed the formation of two phase-separated, vertically aligned and self-assembled MgO nanostructures that extend throughout the entire thickness of the film. These MgO columns induce additional c-axis correlated disorder within the subsequently grown YBCO films, effectively leading to improved pinning characteristics and higher in-field Jc performance. The present results demonstrate the feasibility of novel and potentially practical approaches and the importance of nanostructure engineering in the pursuit of more efficient, economical, and high performance superconducting devices
4:30 PM - **L6.6
Microstructure and Pinning Properties of Nanostructured YBa2Cu3O7-δ Thin Films.
Haiyan Wang 1 , Chen-Fong Tsai 1 , Li Chen 1 , Yuanyuan Zhu 1 , J. MacManus-Driscoll 2 , Q. Jia 3 , C. Varanasi 4 , T. Haugan 4 , P. Barnes 4
1 Electrical and Computer Engineering, Texas A&M University, College Station, Texas, United States, 2 Department of Materials Science and Metallurgy, University of Cambridge, Cambridge United Kingdom, 3 CINT, Los Alamos National Laboratory, Los Alamos, New Mexico, United States, 4 Propulsion Directorate-Power Division, Air Force Research Laboratory, Wright-Patterson AFB, Ohio, United States
Show AbstractThis talk summarizes several successful approaches for enhancing the pinning properties of YBa2Cu3O7-δ (YBCO) thin films in applied magnetic field. The approaches include nanoparticle-doping and nanolayering of various secondary phases such as CeO2, BaZrO3, Y2O3 and magnetic particles. The interfacial defects, including misfit dislocations, lattice distortion introduced by secondary phases, and stacking faults in different systems were studied and compared using cross-section transmission electron microscopy (TEM) and high resolution TEM. We also conducted detailed transport measurements to correlate these interfacial defects for different systems with their transport properties. We observed that the pinning properties have strong correlation with the interfacial defects in the systems.
5:00 PM - L6.7
Effect of Pinning Enhancement Techniques on the Critical Current of Grain Boundaries in Coated Conductors.
John Durrell 1 , Sophie Harrington 1 , Stuart Wimbush 1 , Judith MacManus-Driscoll 1
1 Materials Science and Metallurgy, University of Cambridge, Cambridge United Kingdom
Show AbstractA range of pinning enhancing additions is now available to those designing coated conductors for specific applications. These include BZO, pyrochlore materials and ferromagnetic additions. Additionally, as recently demonstrated by Harrington et al. [1] the nature of the assembly of pyrochlore pinning additions within the superconducting matrix can be changed by changing the growth conditions. However most workers concentrate on showing enhancement of in-grain properties that are caused by these additions and have not considered what effect they may have on the very different structure at a grain boundary.We have prepared thin films of pyrochlore and ferromagnetic pinning enhanced YBCO superconductor on bi-crystal strontium titanate substrates. We show that the angular dependence of the critical current at the grain boundary depends on the type and assembly of the pinning addition used. However, importantly, we do not see any significant deleterious effect on grain boundary properties arising from the use of pinning additions. We discuss the consequences of these observations for the performance of coated conductors containing large assemblies of such pinning enhanced grain boundaries.[1] Harrington S. A., Submitted to “Nanotechnology”
5:15 PM - L6.8
Optimization of Minute Doping of Y1-xRExBaCO Thin Films With RE = Tb and Nd.
Joshua Reichart 1 , Evan Thomas 2 , Timothy Haugan 1 , Xueyan Song 3 , Paul Barnes 1
1 Propulsion Directorate, Air Force Research Laboratory, Wright-Patterson AFB, Ohio, United States, 2 Metals and Ceramics Division, University of Dayton Research Institute, Dayton, Ohio, United States, 3 Mechanical and Aerospace Engineering, West Virginia University, Morgantown, West Virginia, United States
Show AbstractDoping of YBa2Cu3O7-δ (YBCO) has become an effective means of increasing the flux pinning and critical current densities (Jc) in thin film superconductors, while maintaining the transition temperature (Tc). In previous research efforts, our group showed that doping (Y1-xREx)BCO with typically deleterious rare earth (RE) elements can actually be used to improve the film’s current density via flux pinning when the x molar additions are less than 1%. However, data was only presented for different orders of magnitude (x = 0.01%, 0.1%, 1%) without consideration of optimization. The research presented here demonstrates that the deleterious RE elements can differ greatly in how broad the range of optimal doping concentration is, in addition to the relative doping concentration. Rare-earth elements Nd and Tb were compared due to the difference in degradation mechanisms: Nd additions results in Ba site substitution and Tb123 exhibits poor phase formation. Thin films of Nd and Tb doped YBCO films were grown by pulsed laser deposition (PLD) using standard deposition parameters for plain YBCO. The compositions studied were (Y1-xREx)BCO where x was varied from 0.0001 to 0.025 for Nd and 0.005 to 0.015 for Tb. Targets for PLD were prepared using solid state reaction and sintering procedures. All films were characterized for Jc and Tc by vibrating sample magnetometry. Data for Jc (H,T,theta) and Tc were compared to undoped YBCO films processed under the same conditions. The results show a measurable increase in flux pinning for both different concentrations and range of Nd and Tb doping, with little decrease in Tc.
5:30 PM - L6.9
Effect of BaZr3 (BZO) Nanocolumns on Anisotropy and Asymmetry of the Irreversibility Field in YBCO Coated Conductors.
Yuri Zuev 1 2 , Chiara Tarantini 3 , Jan Jaroszynski 3 , Alex Gurevich 3 , David Larbalestier 3 , Yifei Zhang 2 , Claudia Cantoni 2 , David Christen 2 , Venkat Selvamanickam 4
1 Physics, University of Tennessee, Oak Ridge, Tennessee, United States, 2 Materials Science and Technology Division, Oak Ridge National Laboratory Lab, Oak Ridge , Tennessee, United States, 3 , Applied Superconductivity Center, Tallahassee, Florida, United States, 4 , Superpower, Inc, Schenectady, New York, United States
Show AbstractWe have studied the orientation dependence of the $H_{\mathrm{irr}}$ in coated conductors in magnetic fields up to 45 T. We will discuss an apparent reduced anisotropy and asymmetry of the irreversibility field near $c$ axis, and possible underlying mechanisms for this. The effect of the BZO nanocolumns on the $H_{\mathrm{irr}}$ asymmetry, apparent reduced mass anisotropy and the $ab-$plane transport $J_C$ will be presented.Work at UT and ORNL sponsored by the U.S. DOE Office of Electricity Delivery and Energy Reliability - Advanced Cables and Conductors.
5:45 PM - L6.10
Angular Dependence of In-field Critical Current in YBCO Films With Correlated Pinning Centers by 3D Simulations of Vortex Dynamics.
Jose Rodriguez 1
1 Physics and Astronomy, California State University at Los Angeles, Los Angeles, California, United States
Show AbstractMassively parallel computers are exploited in order to perform three-dimensional (3D) simulations of vortex dynamics in superconducting films of YBa2Cu3O7-x (YBCO) that are threaded by linear pinning centers such as edge dislocations and nano-rod inclusions along the c axis. Three dimensionality is achieved by assigning the vortex dynamics within a given layer of YBCO to a particular central processing unit (CPU), and then by communicating between pairs of CPU’s that correspond to adjacent layers of vortices. This computational scheme used to determine the in-field critical current that results from weak linear pinning centers aligned along the c axis in YBCO thin films. It should therefore be particularly relevant to the regime where the applied magnetic field approaches the irreversibility line. We find evidence for the coherent summation of pinning forces along the length of a correlated pin at orientations of the external magnetic field that are sufficiently close to the c axis. The pinning forces along the length of a vortex line add up incoherently, on the other hand, at orientations of the magnetic field that are sufficiently far away from the c axis. We believe that this effect is the root cause for the c-axis peak commonly exhibited by the critical current of YBCO thin films as a function of the magnetic-field orientation. Last, at intermediate orientations of the external magnetic field about the c axis, we search for the presence of a broken vortex lattice state that is characterized by bundles of vortex lines pinned to material line defects in a step-wise fashion.This work is supported in part by the Air Force Office of Scientific Research grant no. FA9550-09-1-0660.
L7: Poster Session
Session Chairs
Janusz Karpinski
Mariappan Paranthaman
Friday AM, April 09, 2010
Salon Level (Marriott)
9:00 PM - L7.1
Development of Simplified Buffer Architectures Based on IBAD-TiN for Coated Conductor Applications.
Ruben Huehne 1 , Ronald Gaertner 1 , Ludwig Schultz 1 , Bernhard Holzapfel 1
1 Institute for Metallic Materials, IFW Dresden, Dresden Germany
Show AbstractIon Beam Assisted Deposition (IBAD) is one of the major approaches to provide biaxially textured templates for REBCO coated conductors. Whereas IBAD-MgO layers are already in use for long-length production, other materials like TiN might be applied in the same way as they show a similar strong cube texture at a thickness of less than 10 nm, if an amorphous or nanocrystalline seed layers is used. Accordingly, cube textured IBAD-TiN layers have been deposited reactively using pulsed laser deposition on polished metal tapes as Hastelloy or stainless steel. The influence of an amorphous or nanocrystalline seed layer as well as of the roughness of the tape on the in-plane texture has been studied in detail. An amorphous metallic TaxNi1-x seed layer was tested successfully for the IBAD-process leading to highly textured TiN films with an in-plane orientation below 10°. Furthermore, suitable single buffer layers as for example SrZrO3 were used afterwards directly on TiN. As a result, biaxially textured YBCO layers were obtained showing an in-plane alignment below 10° and critical current densities of about 1 MA/cm2.
9:00 PM - L7.10
Fabrication of YBCO Coated Conductor on NiW Tapes by Pulsed Laser Deposition.
Yijie Li 1 , Linfei Liu 1 , Huaran Liu 1 , Zuncheng Zhao 1 , Xiaokun Song 1 , Dan Hong 1
1 Department of Physics, Shanghai Jiao Tong University, Shanghai, Shanghai, China
Show AbstractYBCO coated conductor has been fabricated on rolling assisted biaxially textured Ni-W tapes by pulsed laser deposition (PLD). All of YBCO layer and multi-layer buffer architecture were deposited in a compact reel-to-reel PLD system. Fast and practical deposition processes have been developed for long tape fabrication. The influence of deposition conditions on the orientation, texture, surface morphology and superconducting properties have been systematically studied. It was found that the orientation of cerium oxide seed layer was very sensitive to forming gas (97%Ar+3% hydrogen) pressure. High critical current density of YBCO layers has been achieved by inhibiting misorientation of YBCO along Ni crystal grain boundaries. Under optimized deposition conditions, over 4×10<6>A/cm<2> critical current density has been realized.
9:00 PM - L7.11
Effects of a Liquid Carbon Dopant on the Superconducting Properties of MgB2.
Hai Woong Park 1 , Hyo Jin Kim 1 , Chan Joong Kim 2
1 Materials Engineering, Korea University of Technology and Education, Cheonan, ChungNam, Korea (the Republic of), 2 Nuclear Nanomaterials Development Laboratory, Korea Atomic Energy Research Institute, Daejeon, ChungNam, Korea (the Republic of)
Show AbstractVarious types of chemical doping have been reported as very effective methods to improve the superconducting properties of MgB2 superconductor. Specially, carbon doping via liquid type of carbon-containing compounds have been shown better superconducting properties. In this work, the liquid type of glycerin (C3H8O3) was used as a carbon dopant in MgB2 synthesis. The glycerin was mixed with a liquid media at a different ratio and then pretreated with refined boron powder. Then carbon doped MgB2 superconductor was synthesized through subsequent heat treatment of the pretreated boron powder with magnesium powder. Variation of the amount of carbon dopants and viscosity of the liquid media was correlated with critical current densities and other superconducting properties of MgB2 bulk. The effects of liquid carbon dopants on the superconducting properties also compared with those of solid dopants.
9:00 PM - L7.12
Synthesis of Superconductor Materials Using Carbothermic Reduction Method.
Claudio Carvalho 1 , Elen Arlindo 1 , Stevan Pereira 1 , Victor Reynoso 1 , Joao Silveira 1 , Hermes Aquino 1
1 Physics and Chemistry, Unesp, Ilha Solteira, SP, Brazil
Show AbstractIn the past few years, materials in a nanometric scale, known as nanostructured materials or nanomaterials, have attracted the attention of several research groups due to the new properties displayed by these sorts of materials. In this work, it was studied the synthesis of cuprate superconductor Bi2Sr2CaCu2O8 (BSCCO-2212) nanostructured materials, because the great technological perspective that these materials present. In order to perform the syntheses, a carbothermal reduction method was used. In this method, oxides are mixed with carbon to furnish the growth of nanostructured materials in lower temperatures than by conventional evaporation methods. The resulting materials were characterized by x-ray diffraction and electronic microscopy techniques. The ceramics were have also submitted to x-ray diffractometry to analyze the structural phases developed during the thermal treatment, hence indicating that phase 2212 may be the predominant phase and there are some spurious phases, segregation phases, such as Ca2PbO4, which frequently forms along the synthesis process. The results showed that nanobelts with different oxidation states can be obtained and also that the growth of such nanobelts is very dependent on the atmosphere applied during the syntheses. By electron microscopy, it was possible to verify that the nanobelts are single crystals. These results also confirm that carbothermal reduction method is a good route to grow pure cuprate superconductor one-dimensional nanostructures. Alternative thermal treatments to get the expected phase as well as electrical and magnetic measurements are in progress.
9:00 PM - L7.13
Synthesis of Ceramic Materials Using Microwaves.
Claudio Carvalho 1 , Joao Silveira 1 , Victor Reynoso 1 , Hermes Aquino 1 , Stevan Pereira 1
1 Physics and Chemistry, Unesp, Ilha Solteira, SP, Brazil
Show AbstractGdFeAsO1-δ is one of the most studied new superconductive materials (Tc=55 K). Many papers have been published on the Ln–Fe–As–O system in which Ln may be replaced by rare earth elements to obtain physical property modifications, such as higher critical temperature and critical current density. The synthesis of these materials can be obtained by the solid state reaction technique, which requires special conditions. The heating–cooling cycle, if a conventional oven is used, may be take a couple of hours and high temperature. On the other hand, microwave heating has been suggested as a means of reducing the time of preparation, the energy consumption and as a sintering tool. In our laboratory we are studying the possibility to substitute the conventional oven with a microwave oven (600 W / 2.45 GHz) for the synthesis of GdFeAsO1-δ and the Ln–Fe–As–O system doped with rare earth elements. The results obtained indicate that at least in the case of simple microwave heating, the same intermediate compounds are formed in the same sequence as in conventional furnace heating. Samples can be obtained with a very sharp reduction in reaction time and, when the microwave treatment is performed in a reaction boat surrounded by SiC The samples were heated for periods of 15 min. After each heating step, the sample was allowed to cool for about 15 min, and an aliquot was taken for x-ray analysis. Further studies on the synthesis of GdFeAsO1-δ films on different substrates and on the Ln–Fe–As–O system doped with rare earth elements are at present in progress, and the preliminary results are encouraging.
9:00 PM - L7.14
Influence of Zn Doping on Dielectric Properties of Cu0.5Tl0.5Ba2 Ca3Cu4-yZnyO12-δSuperconductor.
Adnan Younis 1
1 Department of Physics, Quaid-i-Azam University Islamabad, Rawalpindi, Punjab, Pakistan
Show AbstractThe role of Zn doping in Cu0.5Tl0.5Ba2Ca3Cu4-yZnyO12-δ (y=0, 3) superconductor to modify the dielectric properties, such as dielectric loss (tanδ) and ac-conductivity (σac) by means of capacitance (C) and conductance (G) measurements with test frequency (f) in the range of 10 KHz to 10 MHz have been studied. A negative capacitance (NC) phenomenon has been observed, which is most likely arising due to higher Fermi level of ceramic superconductor samples than metal electrodes. Also the NC may be due to the space charge located at the multiple insulator-superconductor interfaces (grain boundaries) in the materials. The large values of negative dielectric constant (ε/) show strong dispersion at low frequencies. The lower thermal agitation at 79 K may enhance the polarizability and hence the dielectric constants (ε/ and ε//). The effect of the variation of carriers concentration in the conducting CuO2/ZnO2 planes of Cu0.5Tl0.5Ba2Ca3Cu4-yZnyO12-δ (y = 0, 3) superconductors by post-annealing in oxygen on their dielectric properties has also been investigated.
9:00 PM - L7.15
Microstructure and Defects of Epitaxial Co-doped BaFe2As2 Thin Films Grown on Perovskite Substrates.
Yi Zhang 1 , Christopher Nelson 1 , S. Lee 2 , C. Bark 2 , Chang-Beom Eom 2 , Xiaoqing Pan 1
1 Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan, United States, 2 Department of Materials Science and Engineering, University of Wisconsin, Madison, Wisconsin, United States
Show AbstractThe discovery of any new high transition temperature superconductor immediately poses the question of whether it has the essential qualities for applications such as high critical current density Jc and capability of grain boundaries (GBs) to transmit supercurrent. These properties depend strongly on the microstructures and defects of the fabricated materials. In this paper we report the microstructures and defects and their effects on the electrical properties of the epitaxial Co-doped BaFe2As2 thin films on various perovskite oxide substrates. Transmission electron microscopy (TEM) revealed that the film on bare SrTiO3 (STO) or STO/(La,Sr)(Al,Ta)O3 (LSAT) structure shows epitaxial growth with uniformly distributed nanopillars of a secondary phase running along the Ba-122 c-axis, while the film on bare LSAT shows polycrystalline textures with many misoriented grains. The density of the secondary phase nanopillars is found to increases with the lattice mismatch between Ba-122 thin films and the substrates. Based on atomic resolution TEM imaging and quantitative analysis by x-ray dispersive spectroscopy and electron energy-loss spectroscopy, the high resistivity of a film on bare LSAT in comparison to that of a film on templated LSAT might be caused by grain boundary scattering. The vertical nanopillars in films on templated LSAT and bare STO are found to be strong flux pinning centers, resulting in a higher Jc in the film on STO/LSAT than that of the film on bare STO.
9:00 PM - L7.16
X-ray Anomalous Scattering Studies of the Geometrically Frustrated Antiferromagnet Herbertsmithite.
Danna Freedman 1 , Andrea Prodi 1 , Young Lee 1 , Daniel Nocera 1
1 , MIT, Cambridge, Massachusetts, United States
Show AbstractThe frustrated antiferromagnet herbertsmithite displays no magnetic ordering transition down to 50 mK. The structure of herbersmithite consists of kagomé layers of Cu2+ ions separated by charge balancing layers of Zn2+. Since the successful synthesis and characterization of this compound seven years ago, numerous researchers have examined the possibility that herbersmithite is a perfect geometrically frustrated magnet, behaving as a spin liquid. For spin liquid behavior to occur it is expected that there is no Zn present in the kagomé layers. The presence of Zn cations could lead to spin glass behavior which would manifest itself in a manner akin to geometric magnetic frustration. Therefore, positive identification of Zn in the kagomé layer or the elimination of that possibility is essential to the characterization of herbersmithite, the only potential perfect S = ½ geometrically frustrated antiferromagnet. Due to the difficulty in differentiating Cu and Zn using traditional crystallographic methods, we pursued X-ray absorption studies at the Cu and Zn edges to determine the occupancy of Zn in the Cu layers. Preliminary results which show a positive identification of Cu in two samples of the structurally analogous mineral paratacamite, prepared with 33% and 50% Cu occupancy in the charge balancing layers. X-ray absorption studies on herbersmithite, which are in progress, will also be presented.
9:00 PM - L7.17
Design for a Superconductor Discovery Engine(SCODEngine).
O.Paul Isikaku-Ironkwe 1 2 , Dan Asiegbu 2 1 , Emeka Oguzie 3 1
1 Novel Materials Department, The Center for Superconductivity Technologies (TCST), Abuja FCT, Abuja FCT, Nigeria, 2 Department of Physics, Michael Okpara University of Agriculture, Umudike, Abia State, Nigeria, 3 Department of Chemistry, Federal University of Technology, Owerri, Imo State, Nigeria
Show AbstractMost known superconductors were discovered by serendipity rather than by design.A paradigm shift from discovery by serendipity to discovery by design would trigger a revolution in superconductivity.Correlations of superconductivity transition temperature with electronegativity, valence electron count and atomic number make it possible to design search maps based on superconductor stoichiometries.Linking these maps to databases of known superconductors and employing search engine technology,we design a superconductor discovery engine:SCODEngine.SCODEngine also incorporates a knowledge discovery engine.With SCODEngine we can execute a rapid computational combinatorial search and discovery of novel superconductors. We demonstrate the power of SCODEngine by predicting some novel superconductors.
9:00 PM - L7.18
Predicting New Families of High-Tc Superconductors.
O.Paul Isikaku-Ironkwe 1 , Emeka Oguzie 2 1
1 Novel Materials, The Center for Superconductivity Technologies (TCST), Abuja FCT, Abuja FCT, Nigeria, 2 Department of Chemistry, Federal University of Technology, Owerri, Imo State, Nigeria
Show AbstractA grand challenge of superconductivity is moving from serendipitous discovery to discovery by design. Strong correlations have been established between superconducting transition temperature (Tc) and three parameters namely: electronegativity(X), valence electron count (Ne) and atomic number (Z). We develop a formula linking all three parameters to Tc. The average Ne over the square root of Z we found is a determining factor of superconductivity. When this ratio is greater than 0.5 and less than 1, we are likely to have a superconductor, if the electronegativity is greater than 1.5. Exceptions occur for carbon-based superconductors and a few Pnictide superconductors. We provide data on the spectrum of known superconductor families with electronegativity ranging from 1.5 to 2.7. From this spectrum map, we locate the X, Ne and Z parameters of yet to be discovered superconductors and predict their probable Tcs. We also propose possible stoichiometries for achieving those high-Tcs.
9:00 PM - L7.2
EPR and Speciation Simulation Study on the Complexation of Cu2+ Ions in the Aqueous Sol-gel System Used for the Preparation of Superconducting YBCO Coatings.
Petra Lommens 1 , Henk Vrielinck 2 , Jonas Feys 1 , Klaartje De Buysser 1 , Freddy Callens 2 , Isabel Van Driessche 1
1 Department of Inorganic and Physical Chemistry, Ghent University, Ghent Belgium, 2 Department of Solid State Sciences, Ghent University, Ghent Belgium
Show AbstractCeramic high temperature superconductors (HTS) are near perfect conductors for electricity and promising materials for applications in green energy generation and energy saving industrial devices such as induction heaters. To allow for integration of HTS materials in for example conducting wires, we need to move from brittle bulk ceramics to thin films on flexible substrates. In our case, YBCO thin films are deposited from aqueous solutions containing precursor salts (metal-acetates) stabilized by complexants (tri-ethanolamine) at almost neutral pH. These precursor solutions are ink-jet printed on top of flexible metal substrates and after gelation, they are transformed into the desired YBCO phase by a subsequent heat treatment under controlled atmosphere. Good inks have to fulfill a number of requirements such as long time stability at more or less neutral pH, good gelation properties upon drying at 60°C and suited decomposition behavior at higher temperatures to avoid cracks and pores. The development of these inks is a time consuming and non-straightforward job that might be simplified if we could predict the stability of precursor inks containing varying concentrations of different complexing agents, additives and metal ions as a function of pH. Therefore, we used a speciation program called Hyss and coupled the generated results with experimental data to check the reliability of the simulations. Both Q-band and X-band EPR results are used to confirm the identity and speciation of the different Cu2+ complexes present. For the model system used here, we find that at pH below 7, only acetates are actively complexing the Cu2+ ions, while when reaching higher pH levels both triethanolamine and ammoniak complexes are formed. Further experiments to exclude the presence of binuclear species in solution are planned. This research is funded by EFECTS, EU project FP7-NMP-2007-SMALL-1 grant n°205854.
9:00 PM - L7.3
Fluorine-free Water-based YBCO Films on STO Single Crystal Substrates: Properties and Modelling.
Pieter Vermeir 1 2 , Jonas Feys 1 , Iwein Cardinael 1 , Jo Schaubroeck 2 , Michael Baecker 3 , Petra Lommens 1 , Isabel Van Driessche 1
1 Inorganic and Physical Chemistry, Ghent University, Ghent Belgium, 2 Department of Industrial Sciences, University College Ghent, Ghent Belgium, 3 , Zenergy Power GmbH, Rheinbach Germany
Show AbstractRecently, much research is being dedicated to the use of chemical solution deposition (CSD) for the production of thin films. High deposition speeds, scalability, low investment costs and the use of cheap and environmentally benign starting products promote CSD over the classically used vacuum techniques. Furthermore, this research focuses on fluorine-free sol-gel precursor solutions using water as primary solvent [1]. After dipcoating the precursor solution on SrTiO3 single crystal substrates, the amorphous gel is transformed into the desired phase by using an appropriate heat treatment. In this work, high quality YBCO films were produced with a Tc,onset of 92 K, a ΔTc of 2 K and a Ic of 50 A/cm-width at 77.3 K and self-field [2].We have intensively studied the thermal decomposition behaviour of the precursor, bringing us new insights in the mechanism behind this water-based approach for the deposition of YBCO coatings. A chemical reaction model reveals liquid phase sintering in which the formation of BaCO3 plays a key role for the production of highly textured layers. In contradiction to previous reported findings, we find that BaCO3 is a desirable intermediate product for the development of high-quality YBCO superconducting layers. We found that, by handling the proposed reaction model, the texturation using fluorine-free water-based precursor systems can be tuned adequately.[1]Schoofs B, Cloet V, Vermeir P, Schaubroeck J, Hoste S and Van Driessche I 2006 Supercond. Sci. Techn. 19 1178-84.[2]Vermeir P, Cardinael I, Backer M, Schaubroeck J, Scacht E, Hoste S and Van Driessche I 2009 Supercond. Sci. Techn. 22 075009.
9:00 PM - L7.4
Study on Resistance Increase Trends and Recovery Characteristics of YBCO Thin-film Wire According to Insulation Layer.
Ho-Ik Du 1 , Byoung-Sung Han 2 , Sang-Seob Song 3 , Jong-Su Lee 3 , Dong-Hyeok Lee 2
1 Advanced Graduate Education Center of Jeonbuk for Electronics and Information Technology-BK21, Chonbuk National University, Jeonju, Jeonbuk, Korea (the Republic of), 2 Department of Electrical Engineering, Chonbuk National University, Jeonju Korea (the Republic of), 3 Department of Electronics Engineering, Chonbuk National University, Jeonju Korea (the Republic of)
Show AbstractTo manufacture superior-performance superconducting power machines, it is essential to develop high-quality superconducting wires and to secure data regarding the accurate evaluation of the wire’s properties. Superconducting power machines are supposed to have superconducting characteristics: normal conducting phase changes. To understand such phase change characteristics, the resistance increase trends of superconducting wires at each prescribed temperature, and the post-quenching characteristics of recovery of the superconducting state, should be examined. Moreover, to apply the superconducting wire to power machines, it is necessary to conduct research on the characteristics of wire phase changes in connection with insulating layers. Thus, in this study, according to the presence or absence of insulating layers in the wire, and to the thickness of such layers, the wire’s resistance increase trends and the characteristics of its recovery from quenching were examined by current-applied cycle at the temperatures of 90, 180, 250, and 300 K. Towards this end, YBCO thin-film wires that have the same critical temperatures and that have copper and stainless-steel stabilizing layers were prepared. One level and three and five levels of superior-performance polyimide pressure-sensitive adhesive tape was attached to the wires at a very low temperature. Wires without insulating layers were also prepared. The eight prepared test samples were wound around the linear formers, then the wire’s voltage and current created owing to the phase change characteristics were measured at each prescribed temperature, using the four-point probe method. Further, near the examination temperatures of 90, 180, 250, and 300 K, the wire’s resistance and recovery characteristics were examined by cycle. In this study, YBCO thin-film wires with different stabilizing layers and with insulating layers were examined in terms of their various characteristics, such as quenching occurrence, spread, and distribution, based on their resistance increase trends and their recovery from quenching, and the results were qualitatively explained. The results of this study on the characteristics of YBCO thin-film wires’ superconducting and normal-conducting phase changes are expected to be useful in designing superconducting power machines and in improving their performance.
9:00 PM - L7.5
Strain Accommodation Mechanisms for Oxide Inclusions in REBa2Cu3O7-δ Coated Conductors.
Suman-Lata Sahonta 1 , Marcus Weigand 1 , John Durrell 1 , Judith MacManus-Driscoll 1
1 Materials Science and Metallurgy, University of Cambridge, Cambridge United Kingdom
Show AbstractCommercialization of high-temperature superconductors (HTSs) for use in power transmission cables, motors and electrical power generators has been augmented by the development of epitaxial HTS-coated conductor wires and tapes on biaxially-textured templates, such as YBa2Cu3O7-δ (YBCO) on multilayer buffer stacks based on ion-beam-assisted-deposition MgO film (IBAD-MgO). However, YBCO films over 1 µm thick are required to maintain the high critical current (IC) required for use in power transmission, meaning that high deposition rates, smooth surface layers and large-area coverage by metal–organic chemical vapor deposition (MOCVD) are essential. Owing to the small coherence length of a few nanometres in HTSs, the atomic-scale defect structure within the film determines the transport properties. It is well-known that the critical currents in HTS films are limited by the presence of grain boundaries (GBs), where the current density decreases exponentially with misorientation angle between adjacent grains owing to reduced pinning which causes flux channeling. In this work we present transmission electron microscopy (TEM) analysis of a 1 µm thick film composed of YBCO with small amounts of other rare earth elements substituting the yttrium (REBCO) which was deposited by MOCVD onto the IBAD-MgO-based buffer stack on electropolished Hastelloy tape. Rare earth oxide inclusions are observed in the HTS film. Four-probe measurements of dc voltage-current characteristics were used to measure IC values. The obtained current density (JC) of 2.8 × 1010 Am-2 at zero applied field and 77.35 K confirmed the high quality of the tape. The film comprised large grains of REBCO of approximately 3 µm in size. The average relative tilt angle of adjacent grains was measured as 1.7 ° by means of the Read-Shockley model whereby the GB is described as a low-angle tilt boundary populated by edge-type misfit dislocations (MDs), where the dislocation spacing D is related to the tilt angle θ as D = |b|/ sin θ, where |b| is the modulus of the dislocation Burgers vector. GBs with such low tilt angles are not expected to restrict the flow of supercurrent within the REBCO. The rare earth oxide inclusions (composed of a mixture of Sm2O3 and Y2O3) varied in size from 20 nm to over 100 nm and appeared to have segregated to GBs regardless of size, predominantly occupying junctions between three or more GBs in order to relieve strain in the growing film. The relative tilt angle of grains adjacent to oxide inclusions was on average 2.2 °, indicating that rigid body rotation of grains occurs to accommodate the inclusions into the film microstructure. The high IC values suggest that despite their large size, the inclusions do not obstruct the supercurrent significantly, and may allow vortex pinning at their edges.
9:00 PM - L7.6
V-I Characteristics of YBCO-based Coated Conductors: Effects of Stabilizers and Splices.
Yifei Zhang 1 , Robert Duckworth 1 , Tam Ha 1 , Michael Gouge 1 , David Christen 1
1 , Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States
Show AbstractThe voltage-current (V-I) characteristics of a coated conductor at the level where the electrical currents are above the critical current (Ic) are essential for consideration of power dissipation in the design of a superconducting device. While the V-I characteristics of the superconducting layer are strongly dependent on temperature and magnetic field, the overall characteristics are also affected by the metallic layer(s) that are used to reinforce and stabilize the conductors. In this study, transport measurements were carried out at different temperatures and magnetic fields on commercial coated conductors with different stabilizers. Effects of the stabilizing materials on the conductor’s V-I characteristics were analyzed. V-I characteristics of the conductors with splice joints were also investigated, where the soldered splices were fabricated using the methods recommended by the conductor manufacturers. The data are compared with model calculations based on independent measurements and known materials properties.Research sponsored by the U.S. DOE Office of Electricity Delivery and Energy Reliability – Advanced Cables and Conductors Program under contract DE-AC05-00OR22725 with Oak Ridge National Laboratory, managed and operated by UR-Battelle, LLC.
9:00 PM - L7.7
Microstructural and Pinning Properties of YBa2Cu3O7-δ Thin Films Doped With Magnetic Nanoparticles.
Chen-Fong Tsai 1 , Haiyan Wang 1
1 Department of Electrical and Computer Engineering, Texas A&M University, College Station, Texas, United States
Show AbstractIn this research, we conducted a systematic study on the microstructural and physical properties of the YBa2Cu3O7-δ (YBCO) thin films doped with magnetic nanoparticles. We incorporated magnetic nanoparticles (i.e., Ni, Fe2O3, etc.) with various particle doping approaches including nanoparticles on top, nanoparticle at bottom and nanolayer approach. We conducted a detailed microstructural characterization on all the doped samples by X-ray diffraction (XRD), scanning electron microscopy (SEM), and cross-sectional transmission electron microscopy (TEM). The critical current densities at both self-field and in-field (Jcsf and Jcin-field (H//c)) and the critical transition temperature (Tc) of the doped YBCO thin films and a reference YBCO sample were measured by a Superconducting Quantum Interference Device (SQUID). The Tc of the doped YBCO films varies from 85K-89K and the Jc is in the range of 1.2-2MA/cm2 (at liquid N2, 75.5K) depending on the dopant and doping approach. The pinning properties of these doped YBCO films were explored at different temperatures and correlated with their microstructural characteristics.
9:00 PM - L7.8
Phase Chemical Characterization of M-Doped YBCO Films (M = Ce, Ho, Nb, and Zr) Produced by Metal-Organic Chemical Vapor Deposition.
Victor Maroni 1 , Zhijun Chen 1 , Jeremy Kropf 1 , Dean Miller 1 , Nestor Zalusec 1 , Tolga Aytug 2 , Parans Paranthaman 2
1 , Argonne National Laboratory, Argonne, Illinois, United States, 2 , Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States
Show AbstractThe YBCO coated conductor produced by metal-organic chemical vapor deposition (MOCVD) is a leading candidate for practical applications of superconducting ceramics. Recent studies have shown that certain types of defect structures induced by selective metallic element doping of MOCVD YBCO films led to beneficial improvements in flux pinning. This paper will report the results of characterization studies carried out to (1) investigate the effects of M-doping of MOCVD YBCO (M = Ce, Ho, Nb, and Zr) on the phase chemistry of the resulting films and (2) correlate the observed phase chemistry with the measured superconducting properties and micro-structure of those same films. These studies were performed by a combination of Raman spectroscopy and x-ray absorption spectroscopy (XAS). Maximum improvements in flux pinning (H//ab and H//c at 77 K and 1 T) were obtained for Ce=5 m/o, Ho=10 m/o, and Zr=2.5 m/o, whereas Nb doping, even at low levels did not yield an improvement in current transport. Raman measurements showed that cation disorder and barium cuprate levels tended to increase with increasing dopant content--the increases being greatest for Ce- and Nb-addition, moderate for Zr-addition, and lowest for Ho-addition. XAS results for the Ho- and Zr-doped films confirmed the presence of several dopant containing phases: a barium zirconate-like phase (BZO) for Zr additions and an M2O3-like phase for Ho additions. Crystal field excitations seen in the Raman spectra of the Ho-doped films confirmed the presence of Ho-containing M2O3. The near edge XAS spectra of both the Ho-doped films and the Nb-doped films exhibited at least two isosbestic points indicating the existence of two or more phases containing Ho in the one case and Nb in the other. Estimates of the size range of the BZO particles in the Zr-doped films determined from the Zr K-alpha extended x-ray absorption fine structure indicated that some of the BZO-like particles in the optimally doped film were as small as 2 nm and that the range of BZO-like particle sizes broadened and increased in mean particle size with increasing Zr addition. These results will be compared with findings from transmission electron microscopy measurements reported on in a companion paper.[Research conducted at the Argonne National Laboratory and the Oak Ridge National Laboratory was supported by the U.S. Department of Energy, Office of Electricity Delivery and Energy Reliability, Advanced Cables and Conductors, under contract DE-AC02-06CH11357 between UChicago Argonne, LLC and the USDOE and under contract DE-AC05-00OR22725 between U.T.-Battelle, LLC and the USDOE. The Electron Microscopy Center at Argonne is supported by the Office of Science.]
9:00 PM - L7.9
Development of 3D Patterning and Probing Structures on YBCO Films by Raman Profiling Spectroscopy.
Maria Branescu 1 , Arturas Vailonis 2 , Emanuel Leroy 3 , Ian Ward 4
1 , National Institute of Materials Physics, Bucharest, Magurele Romania, 2 , Stanford University, Palo Alto, California, United States, 3 , Horiba Jobin Yvon Inc., Edison, New Jersey, United States, 4 , EAG, Sunnyvale, California, United States
Show AbstractWe present and develop a new nanoscale approach regarding 3D structures configured on YBCO films by Raman profiling system. We probe in-depth nanoscale effects of the laser light irradiation, belonging to the Raman profiling system, on an YBCO thin film. We probe the nanoscale function of in-depth Raman profiling spectra in YBCO films by using a broad spectrum of phonons (lattice vibrations), charge fluctuations (electronic excitations) and magnons (spin wave dispersion). Raman mapped and SEM images show the submicron boundaries between grains with different crystalline orientations and the surface aspect of the film, respectively. We correlated information of unaxial texture from X-ray diffraction pattern and the ratio of O(2,3) and O(4) Raman intensity. We analyze and detail new progress in engineering 3D quantum electronic devices by using both in-depth Raman profiling spectra (for passive components patterned on a predominantly c-axis oriented film) and Raman mapped images (for active components, patterned at a clear delimited planar boundary between an a-axis and a c-axis oriented grains). We propose a new possible tool of Raman profiling system to configure 3D structures useful for quantum electronics application. Other applications, highly desirable for transport improvement, as 3D control of size, shape, density of flux-pinning and the nanoscale optimization of superconducting properties, are also possible to experiment.