Evolution Behavior of Electrocaloric Effect in BaTiO3‐based Ceramics with Different Phase Structures and Phase Transitions

In this work, the evolution behavior of electrocaloric effect in BaTiO3-based ceramics with different phase structures and phase transitions was compared. A paradigmatic system of (Ba0.85Ca0.15)(Ti1-xHfx)O-3 ceramics was selected. Diffuseness exponent ? increases linearly with rising x. Electrocaloric temperature change (?T) shows an opposite variation, whereas temperature span (T-span) displays the same tendency with ? changing. The degeneration of maximum polarization and polarization change rate contributes to the decrease in ?T due to the diffusion phase transition, whereas the diffusion can lead to a large Tspan. The ceramic with a single ferroelectric or paraelectric phase shows a small ?T but a high variation rate with elevating electric field (E), whereas a small variation rate is present in the phase-transition region that shows a high ?T. Besides, small electrocaloric strength (?T/?E) is obtained in the single-phase region and increases with elevating E. A high ?T/?E is present in the phase-transition region but decreases with elevating E. When phase transition becomes diffusion, ?T variation with E becomes obvious, whereas ?T/?E dependence will decrease. These phenomena result from the difficult polarization orientation in single ferroelectric phase or weak polarization in paraelectric phase, and the easy polarization orientation in the phase-transition region.