Relaxor behavior and ferroelectric polarization modified by Sm doping of Ba0.9Sr0.1Ti0.93Sn0.07O3 ceramics for electrocaloric cooling applications

Abstract

Electrocaloric (EC) cooling is a promising alternative to conventional vapor-compression refrigeration by virtue of its potential for miniaturization, its high energy efficiency, cost-effectiveness, and environmental benignity. However, the practical application of lead-free EC ceramic materials is hindered by the challenge of simultaneously realizing a large adiabatic temperature change (ΔT) and a broad operating temperature span (T_span). In this work, Sm³⁺ was doped into the A-sites of a Ba_0.9Sr_0.1Ti_0.93Sn_0.07O₃ ceramic system to modify its ferroelectric polarization and relaxor behavior. The (Ba_0.9Sr_0.1)_0.995Sm_0.005Ti_0.93Sn_0.07O₃ ceramic exhibits a ΔT of 3.8 K at an electric field of 200 kV cm⁻¹ near room temperature, accompanied by a wide T_span of 78 °C. A decrease in oxygen-vacancy concentration with increasing Sm³⁺ doping content significantly improves the dielectric breakdown strength of the ceramics. The enhanced breakdown strength effectively boosts spontaneous polarization, thus enabling excellent room-temperature electrocaloric performance. This work provides a facile and effective compositional regulation strategy for optimizing the electrocaloric properties of BaTiO₃-based ceramics for solid-state cooling applications.