Supported by the National Natural Science Foundation of China (Grant No. T2488302, T2342010, etc.), Prof. Xiaoshi Qian’s team at the Interdisciplinary Research Center for Engineering Science, School of Mechanical Engineering, Shanghai Jiao Tong University, has made an advance in the research of lead-free electrocaloric ceramics. The related research titled “Giant electrocaloric effect in high-polar entropy perovskite oxides” was published online on April 9, 2025 in Nature. Link to the paper: https://www.nature.com/articles/s41586-025-08768-8.

The electrocaloric effect is a thermal phenomenon resulting from the reversible change in polar entropy of polar materials when subjected to an electric field. It is considered a next-generation cooling technology due to its zero-greenhouse effect, high energy efficiency, and lightweighting design. Inorganic ferroelectric ceramics have long been widely studied as a major electrocaloric material due to their high polarization strength. However, most electrocaloric ceramics with high performance contain a large amount of lead, scandium, and other rare earth elements, so that their large-scale production will face additional environmental and cost issues.To address these issues, the team designed and synthesized a lead-free perovskite oxide with a high-polar-entropy state, discovering the giant electrocaloric effect in it and revealing its intrinsic constitutive relationship. The researchers have created a “high-polar-entropy ceramic” with lattice-level disorder by simultaneously substituting various elements in the A- and B- sites of the BaTiO₃ ceramic to disrupt the ordering of the polar structure, which significantly enhances the electrocaloric effect in lead-free ferroelectric ceramics. The target material can exhibit an adiabatic temperature change of up to 10 K and a large operating temperature window of 60 K near room temperature under an applied electric field (10 MV/m). This study presents an innovative design approach to key materials for electrocaloric cooling technology, and supports the development  of integrated, multilayer electrocaloric work materials.

Figure. “High-polar-entropy” electrocaloric ceramic material sample and its ultra-fine, highly disordered polar structure