Room-Temperature Symmetric Giant Positive and Negative Electrocaloric Effect in PbMg_0.5W_0.5O₃ Antiferroelectric Ceramic

As an emerging solid-state refrigeration technology with zero-emission and high energy conversion efficiency, there is a compelling need for ferroelectric materials with giant electrocaloric effects (ECEs) at room temperature suitable for refrigeration applications. The complex perovskite antiferroelectric (AFE), PbMg_0.5W_0.5O₃, containing non-equivalent B-site ions with a symmetric giant positive and negative ECE near room temperature is presented. At the Curie temperature of 36 °C, the first-order AFE–paraelectric phase transition gives rise to a large enthalpy change of 3.92 J g⁻¹, more than four times that of BaTiO₃. This leads to a significant ECE under the influence of an electric field. The direct electrocaloric characterization shows that the adiabatic temperature change, ΔT, exhibits symmetric peaks with a giant positive maximum of 1.79 K (ΔS = 1.68 J kg⁻¹ K⁻¹) at 36 °C and a negative maximum of −2.02 K (ΔS = −1.93 J kg⁻¹ K⁻¹) at 34 °C. The ultrahigh magnitude of ΔT near room temperature makes PbMg_0.5W_0.5O₃ a superior electrocaloric material far beyond traditional PbZrO₃-based AFEs. The coexistence of symmetric giant positive and negative ΔT to further improve cooling efficiency is expected. In addition, the good reversibility and negligible leakage current should pave the way for practical applications.