Large electrocaloric effect in lead-free K_0.5Na_0.5NbO₃-SrTiO₃ ceramics

The electrocaloric effect (ECE), i.e., the adiabatic temperature change ΔT_EC, of the lead-free relaxor ferroelectric 0.85K_0.5Na_0.5NbO₃-0.15SrTiO₃ (KNN-STO) ceramics is investigated. The ECE data obtained by a direct method show the existence of a large ECE near the temperature of the dielectric permittivity maximum. Due to the high break-down electric field, a large ΔT_EC exceeding 1.2 K at 300 K and 1.9 K at 340 K was observed at 159 kV/cm in a broad temperature range of 80 K. Such a high ECE response near the room temperature is comparable to that found in lead-based ceramic materials, thus making KNN-STO a strong candidate to replace lead-based materials in future electrocaloric applications.