Energy Storage Performance of Na0.5Bi0.5TiO3-CaHfO3 Lead-Free Ceramics Regulated by Defect Engineering

Over the past decades, Na0.5Bi0.5TiO3 (NBT)-based ceramics have received increasing attention in energy storage applications due to their high power density and relatively large maximum polarization. However, their high remnant polarization (P-r) and low breakdown field strength are detrimental for their practical applications. In this paper, a new solid solution (1-x)Na0.5Bi0.5TiO3-xCaHfO(3) (x = 0.04, 0.08, 0.12, 0.16) was constructed by introducing CaHfO3 into NBT, and thus was prepared using a conventional solid-state reaction. With the addition of CaHfO3, the disorder of the structure increased, A-site vacancies formed, and thus oxygen vacancies were suppressed due to the replacement of the Na+ by Ca2+, resulting in the enhanced relaxation behavior and the reduced P-r, the refined grain, and improved breakdown strength. Furthermore, an optimal recoverable energy storage density (W-rec) of 1.2 J/cm(3) was achieved in 0.92Na(0.5)Bi(0.5)TiO(3)-0.08CaHfO(3) ceramics under the breakdown strength of 140 kV/cm, which is mainly attributed to the resultant defect of Na+ vacancy(.)