Electrocaloric effect of (Ba1-Sr )(Hf Ti1-)O3 lead-free ferroelectric ceramics with phase structure regulation

Electrocaloric (EC) refrigeration is a new type of solid-state refrigeration technology based on the electrocaloric effect (ECE), which has the advantages of environmental protection, high efficiency, easy integration and miniaturization. In this paper, Sr2+ and Hf4+ are doped into the A and B sites of BaTiO3 (BT), respectively. By adjusting the proportional composition, the multicritical point is constructed to improve the adiabatic temperature change (ΔT), and the relaxor ferroelectrics are formed to broaden the working temperature span (Tspan). The effect of doping content on the crystal structure, surface morphology, dielectric, ferroelectric and electrocaloric properties of ceramics is studied systematically. The phase diagram of (Ba1-xSrx)(HfxTi1-x)O3 (BSHT) ceramics is established, and (Ba0.9Sr0.1)(Hf0.1Ti0.9)O3 (BSHT10) is at the multicritical point. It has the most excellent comprehensive electrocaloric performance, with ΔTmax obtained 1.2 K and Tspan (ΔT ≥ 0.9 ΔTmax) reached 45 °C under 50 kV/cm, indicating its potential as a lead-free bulk ceramic material for EC refrigeration applications.