Correlations between local electrocaloric effect and domains in ferroelectric crystals

Abstract

Correlations between the local electrocaloric responses and the domains are critical to understanding the mechanisms of electrocaloric effect and, thus, enhancing the electrocaloric responses in ferroelectrics, which have not been explored. Combining phase-field simulations and entropy analysis, we establish the correlations between local electrocaloric responses and domains for ferroelectric crystals and investigate the local electrocaloric responses in different domain structures. The results reveal that both initial 180° and 90° domain walls (referring to stable domain walls before electric excitation) exhibit large positive electrocaloric responses due to the increased polarization under the applied electric field, where the responses of the initial 180° domain walls are more significant. The final 180° domain walls (referring to stable domain walls after electric excitation) show large negative electrocaloric responses, since the polarization changes from nonzero to zero under the applied electric field. Good agreement between simulations and experimental measurements is observed. In addition, as the domain wall density increases, the macroscopic average electrocaloric response can be enhanced multiplicatively, suggesting that increasing domain wall density is an alternative pathway to enhance electrocaloric response in ferroelectrics.