Composition and Structure Optimized BiFeO₃ -SrTiO₃ Lead-Free Ceramics with Ultrahigh Energy Storage Performance

Dielectric ceramic capacitors have attracted increasing attention as advanced pulsed power devices and modern electronic systems owing to their fast charge/discharge speed and high power density. However, it is challenging to meet the urgent needs of lead-free ceramics with superior energy storage performance in practical applications. Herein, a strategy for the composition and structural modification is proposed to overcome the current challenge. The lead-free ceramics composed of BiFeO₃ -SrTiO₃ are fabricated. A low hysteresis and high polarization can be achieved via composition optimization. The experimental results and finite element simulations indicate that the two-step sintering method significantly influences the decrease in the grain size and improvement in the breakdown strength (E_BDS ). A high E_BDS of ≈750 kV cm^-1 accompanied by a large maximum polarization (≈40 µC cm^-2 ) and negligible remanent polarization (<2 µC cm^-2 ) contribute to the ultrahigh energy density and efficiency values of the order of 8.4 J cm^-3 and ≈90%, respectively. Both energy density and efficiency exhibit excellent stability over the frequency range of 1-100 Hz and temperatures up to 120 °C, along with the superior power density of 280 MW cm^-3 , making the studied BiFeO₃ -SrTiO₃ ceramics potentially useful for high-power energy storage applications.