Large electrocaloric effect over a wide temperature range in BaTiO3-modified lead-free ceramics

Abstract

We report a large electrocaloric effect with an adiabatic temperature change (ΔT) of 0.47 K under 20 kV cm⁻¹ combined with a broad temperature span (T_span) of 23 K within 90% ΔT (maximum) attenuation in a (Ba_0.87Ca_0.13)(Ti_0.87Hf_0.13)O₃ ceramic by indirect measurement. Here, in this (Ba_0.87Ca_0.13)(Ti_0.87Hf_0.13)O₃ ceramic, Ca²⁺ and Hf⁴⁺ are introduced into BaTiO₃ to obtain a multiphase coexisting region with a diffuse phase transition character. The large electrocaloric effect benefits from a larger number of possible equilibrium orientations of polar states due to multiphase coexistence, and the broad temperature span comes from the diffuse phase transition character. Compared to the control sample, BaTi_0.82Hf_0.18O₃ with only diffuse transition but no multiphase coexistence, (Ba_0.87Ca_0.13)(Ti_0.87Hf_0.13)O₃ displays a ΔT value nearly 1.5 times larger than that of BaTi_0.82Hf_0.18O₃ (ΔT ∼ 0.33 K), although they exhibit similar T_span values. Our work may shed light on developing high performance electrocaloric materials with broad temperature ranges.