Ultrafast transient liquid assisted growth of YBa₂Cu₃O₇ coated conductors: why is it a novel process?

Coated conductors (CC) of REBa₂Cu₃O₇ (REBCO, RE= Rare Earth) are an exceptional achievement in materials science which encompassed many scientific and engineering challenges. These superconducting materials have emerged as the most attractive opportunity to reach unique performances at high and low temperatures, particularly at high magnetic fields, while reducing the cost/performance ratio continues to be a key objective for a large scale marketability.<br/>To address the challenge of reducing the cost/performance ratio it is unavoidable to develop ultrafast growth rate processes which will lead to high throughput manufacturing of CCs with high performance. Liquid assisted growth of epitaxial REBCO films appears as a very promising approach to reach growth rates beyond 100 nm/s. We have recently created a novel concept, the Transient Liquid Assisted Growth (TLAG) [1-3], which differs from previous growth paths because it is a non-equilibrium process, i.e. the Ba-Cu-O transient liquid with different stoichiometries leading to the formation of REBCO is not an equilibrium one and its properties can be manipulated through kinetic parameters [4]. We will show that different REBCO (RE= Y, Gd, Yb) films can be grown through TLAG using either the temperature or the PO₂ routes and also with different liquid compositions. The TLAG process is fully compatible with the use of preformed BaMO₃ (M=Zr, Hf) nanoparticles to prepare nanocomposite CCs when propionate metalorganic solutions are used in a Chemical Solution Deposition (CSD) route. Finally, we show that the TLAG process can also be extended to other precursors such as amorphous phases deposited by Pulsed Laser Deposition (PLD) at low temperatures [5]. The growth process has been analyzed by in-situ synchrotron X-ray diffraction analysis which have confirmed that ultrafast growth rates (&gt; 1.000 nm/s) can be achieved. We will show that high critical current densities have been achieved up of 3-5 MA/cm² at 77K in thin films and CCs and the process has been transferred to thicker films and metallic substrates. An overall overview of the features of the TLAG process, as compared to other growth approaches, will be presented [6], together with an outlook of the future potential and the pending challenges of this novel technique.<br/><b>References</b><br/>[1] L. Soler et al, Nature Communications 11, 344 (2020)<br/>[2] A. Queraltó et al, ACS Applied Materials and Interfaces 13, 9101 (2021)<br/>[3] L. Saltarelli et al, ACS Applied Materials and Interfaces 14, 48582 (2022)<br/>[4] S. Rasi et al, Advance Science, 9, 2203834 (2022)<br/>[5] A. Queraltó et al, Superconductor Science and Technology 36, 025003 (2023)<br/>[6] T. Puig et al, Nature Review Physics (in press)