Spontaneous-Chessboard-Ordered Structure of PbMg_0.5W_0.5O₃ Multilayer Capacitors Offers Giant Electrocaloric Enthalpy Change Below Room Temperature

For high-efficiency and zero-emission electrocaloric refrigeration, a continuing challenge is to achieve a large enthalpy change (ΔH) below/near room temperature (RT) for commercial viability. To address this issue, antiferroelectric PbMg_0.5W_0.5O₃ multilayer ceramic capacitors (PMW MLCCs) are synthesized as a result of spontaneous-chessboard-ordered arrangement of heterovalent B-site ions. PMW has a giant ΔH (3.92 J g⁻¹) near RT (36 °C), and the stress-engineered MLCCs further lower the Curie temperature to below RT (19 °C). The complete polarization under high electric fields enables a full release of the large ΔH and produces both a giant positive and negative electrocaloric effect, ΔT_max+ = 7.17 K at 20 °C (@240 kV cm⁻¹) and ΔT_max- = −4.11 K at 10 °C (@180 kV cm⁻¹). Moreover, the coefficient of performance (COP) is dramatically improved by an electric-energy-recovery circuit, and a colossal value of 350 is achieved in a prototypical cooler with 400 MLCCs. This outstanding refrigeration performance opens the door to PMW MLCCs for RT cooling applications with large market potential.