Energy storage performance and electrocaloric effect of lead-free NaNbO₃–La(Nb_1/3Mg_2/3)O₃–CaZrO₃ ceramics

Abstract

Lead-free (0.955 − x)NaNbO₃–0.045La(Nb_1/3Mg_2/3)O₃–xCaZrO₃ ceramics were prepared by the conventional method, the influences of CaZrO₃ content on dielectric properties, energy storage performance and electrocaloric effect (ECE) were studied. The introduction of CaZrO₃ could efficaciously reduce sintering temperature from 1270 to 1230 °C with stabilized anti-ferroelectric (AFE) provskite structure. Obvious thermal hysteresis was observed during phase transition, while the phase transition temperature was reduced from 233 to 177 °C. And the room temperature dielectric properties were also improved with enhanced dielectric constant and suppressed dielectric loss. As a result, the optimum recoverable energy storage density of 1.90 J/cm³ with a noteworthy efficiency of 84.5 % was obtained under 21.3 kV/mm when x = 1.0 %, which was resulted from the AFE-liked hysteresis loops. Moreover, it also presented attractive ECE aspect with positive ECE and negative ECE due to a mixed AFE and ferroelectric phase structure. This study contributes to the development of NaNbO₃-based ceramics in energy storage and solid refrigeration areas.