Achieving high energy storage density and efficiency simultaneously in Sr(Nb0.5Al0.5)O3 modified BiFeO3 based lead-free ceramics

Environmentally friendly BiFeO3-based capacitors have attracted great attention in energy storage applications. Via a design of crossover relaxor ferroelectric state with high maximum polarization and small remanent polarization at moderate electric fields, a large W-rec of 3.95 J/cm(3) and an excellent of 85.9 % was obtained in 0.85 (0.67BiFeO(3)-0.33BaTiO(3))-0.15Sr(Nb-0.5 Al-0.5)O-3 crossover relaxor ceramic. The addition of Sr(Nb0.5Al0.5)O-3 facilitates to the formation of crossover relaxor ferroelectric state and suppresses the early polarization saturation. The breakdown strength of Sr(Nb0.5Al0.5)O-3 modified ceramics is enhanced due to the significantly decreased grain size and the increased band gap. More importantly, the X = 0.15 ceramic exhibits an excellent thermal stability (25-110 degrees C), frequency stability (1-300 Hz), fatigue endurance (after 10 5 cycles), and fast discharge rate (t(0.9) similar to 0.108 mu s) at 140 kV/cm. These results indicate that the BF-BT-0.15SNA ceramic is a promising dielectric energy storage material.