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 Wrec of 3.95 J/cm3 and an excellent η of 85.9 % was obtained in 0.85(0.67BiFeO3-0.33BaTiO3)-0.15Sr(Nb0.5Al0.5)O3 crossover relaxor ceramic. The addition of Sr(Nb0.5Al0.5)O3 facilitates to the formation of crossover relaxor ferroelectric state and suppresses the early polarization saturation. The breakdown strength of Sr(Nb0.5Al0.5)O3 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 °C), frequency stability (1–300 Hz), fatigue endurance (after 105 cycles), and fast discharge rate (t0.9 ∼ 0.108 μs) at 140 kV/cm. These results indicate that the BF-BT-0.15SNA ceramic is a promising dielectric energy storage material.