Excellent energy storage and hardness performance of Sr0.7Bi0.2TiO3 ceramics fabricated by solution combustion-synthesized nanopowders

• An easy and rapid preparation method of dielectric ceramics was innovatively adopted. • An ultrahigh W rec of 5.21 J/cm 3 and a high η of 91.55% are simultaneously achieved in SCS04. • The excellent stability in energy storage performance is achieved in SCS1. • Ultrahigh hardness ( H v ) of ∼ 7.80 GPa is realized in SCS-derived ceramics. Relaxor ferroelectric Sr 0.7 Bi 0.2 TiO 3 ceramics were prepared by two types of powders synthesized by solid-state reaction (SSR) and solution combustion synthesis (SCS). The effects of the synthesis techniques of precursor powders on the microstructure, dielectric and energy storage performance of the ceramics were investigated. Compared with the SSR-derived samples, the SCS-derived ceramics show purer phase, more refined grain size, more uniform and denser morphology. Consequently, higher insulating resistivity and activation energy are obtained, thus inhibiting the carrier migration and improving the breakdown field. For the 0.1 mm-thickness ceramics via using SCS nanopowders in place of SSR powders, the critical electric field and recoverable energy density are enhanced from 320 kV/cm and 2.60 J/cm 3 to 380 kV/cm and 3.60 J/cm 3 , respectively. Particularly, a high recoverable energy density of 5.21 J/cm 3 with a high efficiency of 91.55% at 543 kV/cm is realized in the 0.04 mm-thickness SCS-derived ceramics. Meanwhile, the Vickers hardness of ceramics is promoted from ∼ 7.15 GPa to ∼ 7.80 GPa by using SSR instead of SCS method. This work suggests that SCS is an effective method to obtain precursor powders for sintering the dielectric ceramics with excellent energy storage and hardness performance.