Large electrocaloric response with superior temperature stability in NaNbO ₃-based relaxor ferroelectrics benefiting from the crossover region

Abstract

Large electrocaloric temperature change and superior temperature stability are achieved simultaneously in lead-free NaNbO ₃-based ceramics via construction of a crossover state between ferroelectrics and relaxor ferroelectrics.

Abstract

Electrocaloric refrigeration emerges as a newly developing technology with potential to be the next generation of coolers. However, the combination of large adiabatic temperature change (Δ T) and good temperature stability remains a long-term issue in lead-free ceramics for developing practical electrocaloric refrigeration devices. Herein, no-lead-footprint (0.9 − x)NaNbO ₃–0.1BaTiO ₃– xBaZrO ₃ (abbreviated here as NN–BT– xBZ) ceramics are optimized to select a special crossover state between ferroelectric and relaxor states. NN–BT–0.04BZ ceramic located at the crossover region benefits from multiple aspects involving large polarization, low-temperature ferro–paraelectric transition as well as the relaxor feature. Thus, a desired Δ T of 1.14 K and superior temperature stability (52 K, within ±5% variation in maximal Δ T) were achieved in the vicinity of room temperature. Such an excellent Δ T is almost two times larger than those of other niobate-based ceramics. Our work not only provides a promising electrocaloric material but expands NN-based materials to the electrocaloric refrigeration area, and offers a feasible design strategy for searching practical electrocaloric coolers in other systems.