Evolution behavior of electrocaloric effect in BaTiO3‐based ceramics with different phase structures and phase transitions

Abstract

AbstractIn 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)O3 ceramics was selected. Diffuseness exponent γ increases linearly with rising x. Electrocaloric temperature change (ΔT) shows an opposite variation, whereas temperature span (Tspan) displays the same tendency with γ changing. The degeneration of maximum polarization and polarization change rate contributes to the decrease in ΔT 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 ΔT 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 ΔT. Besides, small electrocaloric strength (ΔT/ΔE) is obtained in the single‐phase region and increases with elevating E. A high ΔT/ΔE is present in the phase‐transition region but decreases with elevating E. When phase transition becomes diffusion, ΔT variation with E becomes obvious, whereas ΔT/ΔE 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.