Submicron Sr0.7Bi0.2TiO3 dielectric ceramics for energy storage via a two-step method aided by cold sintering process

A serials of relaxor ferroelectrics of Sr0.7Bi0.2TiO3 ceramics with different grain sizes were prepared by a conventional sintering (CS) and a two-step cold sintering aided process (CSP) method. The microstructure, dielectric and energy storage performance of the synthesized ceramics were systematically studied. Owing to the involvement of CSP, grain size is reduced to submicrometer scale, and uniform and dense morphology are achieved at a lower sintering temperature compared with the CS method. As a consequence, high critical electric field (420 kV/cm), a good recoverable energy storage density (3.32 J/cm3), and a superior energy efficiency (92.84 %) can be realized for the ceramic via CSP sintered at 1170 °C. Meanwhile, it also exhibits good stability over wide ranges of measuring frequencies and temperatures, and increasing cycles to 107. A high power density (85.46 MW/cm3) is achieved due to a very fast discharge rate (∼61.7 ns). Moreover, the synthesized ceramic demonstrates an ultrahigh hardness of ∼ 8.73 GPa. These results indicate that CSP is a feasible solution to achieve outstanding comprehensive dielectric energy storage performance by utilizing the synergistic effects of grain refinement and densification.