Electrocaloric fatigue of lead magnesium niobate mediated by an electric-field-induced phase transformation

• Published in: Acta materialia Vol. 169; pp. 275 - 283
• Main Authors: Bradeško, Andraž, Fulanović, Lovro, Vrabelj, Marko, Otoničar, Mojca, Uršič, Hana, Henriques, Alexandra, Chung, Ching-Chang, Jones, Jacob L., Malič, Barbara, Kutnjak, Zdravko, Rojac, Tadej
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.05.2019
• Subjects: Electrocaloric effect; Fatigue; Ferroelectric; Phase transformation; Relaxor; Electrocaloric effect; Ferroelectric; Phase transformation; Fatigue; Relaxor
• ISSN: 1359-6454; 1873-2453
• DOI: 10.1016/j.actamat.2019.03.017

Electrocaloric fatigue, i.e., the degradation of the electrocaloric temperature change of an active material under continuous electric-field cycling, has not been addressed in detail so far, despite the elevated electric fields expected for EC cooling devices. Here, we investigate the electrocaloric fatigue mechanism of a prototype relaxor material, i.e., Pb(Mg1/3Nb2/3)O3, by directly measuring its temperature response under device-relevant electric-field conditions. We show that after a critical number of field cycles the temperature of the sample begins to increase dramatically, leading to a significant degradation of the cooling properties. The degradation of cooling properties is investigated using a combination of multiscale characterization techniques, revealing that the origin of the degradation is the increased grain boundary conductance caused by an unexpected electric-field-induced phase transformation to a ferroelectric phase. We further show that this transformation and thus the fatigue can be regulated by careful control of the temperature and electric-field conditions. By revealing a previously unexplored fatigue mechanism, this study provides the first guidelines for the integration of high-performance relaxors into cooling devices. [Display omitted]