Extraordinarily Large Electrocaloric Strength of Metal‐Free Perovskites

Abstract The availability of materials with high electrocaloric (EC) strengths is critical to enabling EC refrigeration in practical applications. Although large EC entropy changes, ΔS_EC, and temperature changes, ΔT_EC, have been achieved in traditional thin‐film ceramics and polymer ferroelectrics, they require the application of very high electric fields and thus their EC strengths ΔS_EC/ΔE and ΔT_EC/ΔE are too low for practical applications. Here, a fundamental thermodynamic description is developed, and extraordinarily large EC strengths of a metal‐free perovskite ferroelectric [MDABCO](NH₄)I₃ (MDABCO) are predicted. The predicted EC strengths: isothermal ΔS_EC/ΔE and adiabatic ΔT_EC/ΔE for MDABCO are 18 J m kg⁻¹ K⁻¹ MV⁻¹ and 8.06 K m MV⁻¹, respectively, more than three times the largest reported values in BaTiO₃ single crystals. These predictions strongly suggest the metal‐free ferroelectric family of materials as the best candidates among existing materials for EC applications. The present work not only presents a general approach to developing thermodynamic potential energy functions for ferroelectric materials but also suggests a family of candidate materials with potentially extremely high EC performance.