Electrocaloric Properties of Defect-Engineered 0.9Pb(Mg_1/3Nb_2/3)O₃–0.1PbTiO₃ Ceramics Upon Neutron and Gamma Radiation

The heating of electronic components has been identified as a severe deficiency in consumer electronics, and even more in professional electronics, where harsh conditions, such as radiation or elevated temperature, add additional requirements to the stability of operation. Application areas include medical diagnostics and therapy, such as proton therapy, space technologies, particle colliders, or nuclear fusion and fission reactors. Electrocaloric (EC) cooling – technology based on the EC effect, i.e., temperature change triggered by the change in applied voltage, could be used to cool electronic components. Relaxor ferroelectrics, exemplified by 0.9Pb(Mg_1/3Nb_2/3)O₃–0.1PbTiO₃ (PMN–10PT), represent a material system that exhibits high enough EC temperature changes of a few K in a broad enough temperature interval of a few 10 K. However, the peak EC values not only increase until we reach the breakdown field but also shift towards higher temperatures as we increase the field amplitude. By introducing defects into the perovskite lattice via aliovalent doping, the temperature range of the peak EC response may be shifted and/or broadened, as shown in the case of Mn-doped PMN-10PT [1].<br/>When considering using EC-based cooling in harsh conditions, the radiation hardness of the EC material is one of the criteria that need to be fulfilled. Neutron and gamma radiation are expected to affect the functional properties of the irradiated materials and, thus, the performance of the entire component or device. We show that PMN-10PT ceramics exhibit similar dielectric, ferroelectric and EC properties after exposure to doses up to 10¹⁷ neutrons / cm² as the pristine samples [2]. But what about PMN-10PT ceramics in which defects are introduced by donor or acceptor doping and contribute to changes in the dielectric, and ferroelectric properties? How do such materials respond to neutron and gamma radiation?<br/>We prepared undoped, acceptor (Mn) and donor (La) doped PMN-10PT ceramics and irradiated them in the TRIGA Mark II research reactor [3]. The ceramics were exposed to 1 MeV equivalent neutron fluence for silicon of 10¹⁶ cm^-2 and 10¹⁷ cm^-2 of and gamma ray dose of 145 kGy and 1200 kGy. In the lecture, we discuss the influence of neutron and gamma radiation on crystal structure, microstructure, dielectric, ferroelectric and EC properties of defect-engineered PMN-10PT ceramics and compare them with those of undoped material used as reference.<br/><br/>[1] A. Bradeško, M. Vrabelj, L. Fulanović, Š. Svirskas, M. Ivanov, R. Katiliute, D Jablonskas, M. Šimenas, G. Usevičius, B. Malič, J. Banys, T. Rojac, Implications of acceptor doping in the polarization and the electrocaloric response of 0.9Pb(Mg_1/3Nb_2/3)O₃–0.1PbTiO₃ relaxor ferroelectric ceramics, <i>J. Mater. Chem. C</i>, 9, 2021, 3204-3214.<br/>[2] H. Uršič Nemevšek, U. Prah, T. Rojac, A. Jazbec, L. Snoj, S. Drnovšek, A. Bradeško, A. Mirjanić, M. Vrabelj, B Malič, High radiation tolerance of electrocaloric (1−x)Pb(Mg_1/3Nb_2/3)O₃−xPbTiO₃, <i>J. Europ. Ceram. Soc.</i>, 42, (13), 2022, 5575-5583.<br/>[3] L. Snoj, G. Zerovnik, A. Trkov, Computational analysis of irradiation facilities at the JSI TRIGA reactor, <i>Appl. Radiat. Isot.</i>, 70(3), 2012, 483-488.