Colossal Barocaloric Effect by Large Latent Heat Produced by First‐Order Intersite‐Charge‐Transfer Transition

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AbstractMaterials which show novel thermal properties can be used to make highly efficient and environmentally friendly energy systems for thermal energy storage and refrigeration through caloric effects. An A‐site‐ordered quadruple perovskite‐structure oxide, NdCu3Fe4O12, is found to release significant latent heat, 25.5 kJ kg−1 (157 J cc−1), at the intersite‐charge‐transfer transition temperature near room temperature. The transition is first‐order and accompanied by an unusual magnetic ordering and a large negative‐thermal‐expansion‐like volume change, and thus, it causes a large entropy change (84.2 J K−1 kg−1). The observed entropy change is comparable to the largest changes reported in inorganic solid materials, and more importantly, it is utilized through a colossal barocaloric effect. The adiabatic temperature change by applying 5.1 kbar pressure is estimated to reach 13.7 K, which means efficient refrigeration can be realized through this effect.