Near‐Room‐Temperature Large Electrocaloric Effect in Barium Titanate Single Crystal Based on the Electric Field–Temperature Phase Diagram

Phase transition plays a key role in the electrocaloric effect, but the first‐order ferroelectric–paraelectric phase transition always occurs far above room temperature, which heavily limits the practical application. Herein, the focus is on the orthorhombic–tetragonal first‐order ferroelectric–ferroelectric phase transition (@288 K) in <011>‐oriented barium titanate single crystal. Ferroelectric properties under a high electric field indicate a reversible field‐induced tetragonal–orthorhombic phase transition, based on which the electric field–temperature phase diagram is established. It is strongly related to the enhanced electrocaloric effect, and a large adiabatic temperature change of 1.33 K is obtained at 288 K under 15 kV cm −1 , that is, a high electrocaloric strength of 88.7 mK cm kV −1 . The large electrocaloric effect near room temperature makes lead‐free BaTiO 3 a promising candidate for next‐generation solid‐state refrigeration.