Bi(Mg0.5Hf0.5)O3-modified SrTiO3 lead-free ceramics for high-temperature energy storage capacitors

Lead-free (1 − x )SrTiO 3 – x Bi(Mg 0.5 Hf 0.5 )O 3 (0.05 ≤ x ≤ 0.4) ceramics were prepared by high-temperature solid-state sintering method. The microstructure, dielectric properties, and energy storage performance were investigated. The diffused phase transition was observed in samples with x ≥ 0.1, showing typical relaxor characteristic. In particular, 0.8ST-0.2BMH composition exhibits stable dielectric permittivity with variation below 15% over temperature range of − 100 °C to 185 °C, superior to that of undoped SrTiO 3 . The calculated Weibull characteristic breakdown strength is 480 kV/cm for 0.8ST-0.2BMH ceramic, and a large energy density of 4.1 J/cm 3 with high energy efficiency of 92% is obtained at electric field of 470 kV/cm. Of particular significance is that the energy efficiency remains above 91% at elevated temperature of 180 °C. In addition, fast discharge time (~ 0.88 µs) with high-power density of 2.8 MW/cm 3 is achieved in 0.8ST-0.2BMH ceramic. All the above results indicate that the 0.8ST-0.2BMH relaxor dielectric is a promising lead-free ceramic for high-temperature energy storage applications.