Large electrocaloric response with superior temperature stability in NaNbO3-based relaxor ferroelectrics benefiting from the crossover region

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 (Delta 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)NaNbO3-0.1BaTiO(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 Delta T of 1.14 K and superior temperature stability (52 K, within +/- 5% variation in maximal Delta T) were achieved in the vicinity of room temperature. Such an excellent Delta 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.