Effect of bismuth excess on the energy storage performance of 0.5Na0.5Bi0.5TiO3-0.5SrTiO3 ceramics

Lead free 0.5Na0.5Bi0.5TiO3-0.5SrTiO3 ceramics with Bi excess (NB0.5+xT-ST) were prepared by a conventional solid-state reaction method. The effects of bismuth excess on microstructure, dielectric properties and energy storage performances of NB0.5+xT-ST ceramics were investigated systematically. The results show that all ceramics exhibit a perovskite structure with excess Bi doping, the grain size decreased and density enhanced. Typical relaxor ferroelectric P-E hysteresis loops were observed with introduction of Bi2O3. The sample with Bi2O3 excess concentration of 1 mol% exhibits the maximum energy storage density 1.05 J cm−3, which is 2 times higher than that of pure NBT-ST. Meanwhile, the sample displays a high current density of 245.6 A cm−2 and a power density of 6.5 MW cm−3. These results indicate that the Bi2O3 excess improved NB0.5+xT-ST ceramics are useful for potential applications in energy storage ceramic capacitors.