Enhanced energy storage density of Sr0.7BixTiO3 lead-free relaxor ceramics via A-site defect and grain size tuning

The application of dielectric capacitors with high energy density is very important to solve the increasingly serious energy crisis. However, the further improvement of energy density is seriously confining by their poor breakdown fields. In this work, outstanding energy storage performance is achieved in Sr 0.7 Bi x TiO 3 (x = 0.1, 0.2, 0.3 and 0.4) ceramics via A-site defect and grain size tuning. It was found that the moderate Bi 3+ content is helpful to reduce sintering temperature and refine grain size, which lead to higher activation energy and breakdown field. Besides, moderate Bi 3+ doping in A-site enhances polarity owing to the hybridizations between 6p orbital of Bi and 2p orbital of O. Thus, a high recoverable energy density of 4.77 J/cm 3 with prominent efficiency of 85.7% at 570 kV/cm is realized in Sr 0.7 Bi 0.2 TiO 3 ceramic. Moreover, the Sr 0.7 Bi 0.2 TiO 3 ceramic also displays superior thermal stability from 20 °C to 160 °C and excellent fatigue endurance over 10 5 cycles. Our results in this work offer a better understanding and design methodology for developing novel high-performance dielectric capacitors.