Energy storage performance and electrocaloric effect of Zr doped BaTiO3-based lead-free ferroelectric ceramics

Environment-friendly Ba_0.95Ca_0.05Ti_0.91Sn_0.09-xZr_xO₃ ceramics, with x = 0.00 and 0.01 (BCTSZ_x) were prepared through a standard solid-state sintering process. The diffusion coefficient estimated from the Santos-Eiras fit of \({\varepsilon }_{r}\)-T plot implies that the ferroelectric-paraelectric transition is a diffuse type. Well-saturated and fatigue resistant P-E hysteresis loops were obtained at room temperature (RT). The energy-storage density (W_rec) and the associated efficiency (η) were obtained from P-E loops data. When applying a relatively losw electric field of 30 kV/cm, a large value of adiabatic temperature change (∆T = 0.73 K), high values of electrocaloric responsivity (ξ = 0.247*10⁻⁶ K·m·V⁻¹) and coefficient of performance (COP = 12.26) were obtained in BCTSZ ceramic. In addition, the pyroelectric figures of merit (FOMs) were calculated. The density of pyroelectric energy harvesting increased from 206 to 237 kJ/m³ when the Olsen cycle was operated at temperatures between 25 and 100 °C and an electric field between 0 and 30 kV/cm. The results indicate that the increase in the grain size significantly enhances the dielectric, electrocaloric and pyroelectric properties. This research not only presents a novel technique for generating high-performance ceramic for refrigeration devices, but also expands the field of applications for BaTiO₃-based lead-free ferroelectrics for energy storage applications.