Enhanced energy-storage properties and charge-discharge performances in Sm3+ modified (Na0.5Bi0.5)TiO3-SrTiO3 lead-free relaxor ferroelectric ceramics

Relaxor ferroelectric materials are highly favorable for pulse power devices owing to the fast charge-discharge speed and large power density. However, the low energy density is still a shortcoming for energy-storage applications. In this work, the excellent energy-storage properties are achieved in 0.5Na0.5Bi0.5TiO3-0.5Sr1-1.5xSmxTiO3 (NBT-SST) relaxor ferroelectric ceramics by a synergistic effect of microstructures based on Sm3+ doping. It is proposed that the introduction of Sm3+ decreases the grain size and tunes the domain structure, leading to the increase of breakdown strength and the enhancement of relaxation characteristics. The maximum recoverable energy-storage density reaches 3.81 J/cm3 coupled with an energy efficiency of 84.7% when x = 0.2. Meanwhile, the ceramic exhibits superior energy-storage stability in the temperature (20–200 ℃) and frequency (10–400 Hz) ranges. Moreover, a high-power density of 135 MW/cm3 and a fast charge-discharge speed of 89 ns are also achieved for ceramic with x = 0.2. These results suggest the NBT-SST ceramic is a potential candidate material in energy-storage capacitor applications.