Phenomenological modeling of phase transitions and electrocaloric effect in Ba(Zr_0.2Ti_0.8)O₃‐(Ba_0.7Ca_0.3)TiO₃

Abstract

Ba(Zr 0.2 Ti 0.8 )O 3 -x(Ba 0.7 Ca 0.3 )TiO 3 (BZT-xBCT) is a promising lead-free ferroelectric system. In this paper, we present two sets of free energy coefficients and carry out phenomenological modeling to study the phase transition and electrocaloric effect. The calculated phase diagram is in excellent quantitative agreement with experiments. Furthermore, we propose a new method based on effective internal electric field to simulate polarization in the macroscopic paraelectric state of ferroelectric relaxor. The computed composition and temperaturedependent entropy and temperature change induced by electrocaloric effect are in good agreement with the measured data available for single crystal.

Anisotropic Properties of Epitaxial Ferroelectric Lead-Free 0.5[Ba(Ti0.8Zr0.2)O3]-0.5(Ba0.7Ca0.3)TiO3 Films

“…Our work shows that (001)-oriented BZT-BCT films exhibit the coexistence of O + T phases, whereas the (110)-and/or (111)-oriented epitaxial BZT-BCT films do not. The enhancement of dielectric properties along certain crystallographic orientations could, for this reason, be explained by the local PNRs directly related to the microstructures, where the coexistence of different phases at room temperature and the specific composition of x = 0.5 can lead to a generally flattened energy barrier [53][54][55][56][57]. Under applied electric fields, the ease of domain switching and polarization rotation can come from the instability of the polarization direction at the MPB characterized by an ultra-low-energy barrier, leading to heightened ferroelectric and piezoelectric responses [58].…”