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

Abstract For high‐efficiency and zero‐emission electrocaloric refrigeration, a continuing challenge is to achieve a large enthalpy change (Δ H ) below/near room temperature (RT) for commercial viability. To address this issue, antiferroelectric PbMg 0.5 W 0.5 O 3 multilayer ceramic capacitors (PMW MLCCs) are synthesized as a result of spontaneous‐chessboard‐ordered arrangement of heterovalent B‐site ions. PMW has a giant Δ H (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 Δ H and produces both a giant positive and negative electrocaloric effect, Δ T max+ = 7.17 K at 20 °C (@240 kV cm −1 ) and Δ T 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.