Enhanced energy storage performance of 0.88(0.65Bi0.5Na0.5TiO3-0.35SrTiO3)-0.12Bi(Mg0.5Hf0.5)O3 lead-free relaxor ceramic by composition design strategy

Dielectric ceramic capacitors with high energy density are one of the great bright energy storage devices. Here, the Bi 0.5 Na 0.5 TiO 3 , 0.75Bi 0.5 Na 0.5 TiO 3 -0.25SrTiO 3 , 0.65Bi 0.5 Na 0.5 TiO 3 -0.35SrTiO 3 and 0.88(0.65Bi 0.5 Na 0.5 TiO 3 -0.35SrTiO 3 )-0.12Bi(Mg 0.5 Hf 0.5 )O 3 , (abbreviated as BNT, BNT-25ST, BNT-35ST and BNST-BMH, respectively) ceramics were produced by solid state sintering method. The influence of solid solution of SrTiO 3 and Bi(Mg 0.5 Hf 0.5 )O 3 doping in Bi 0.5 Na 0.5 TiO 3 on crystal structure, microstructure, electrical and energy storage performance were evaluated systematically. By optimizing ceramics composition, high breakdown field and slim hysteresis loops were simultaneously realized due to enhanced band gap, refined grain size and nano-domains formed, which can be verified by the transmission electron microscope (TEM), piezoelectric force microscope (PFM) and ultraviolet–visible spectrum. Therefore, an ultrahigh recoverable energy density of 5.59 J/cm 3 with brilliant efficiency of 85.3% is realized in BNST-BMH ceramic. Besides, the BNST-BMH also exhibits prominent temperature stability at 20–140 °C, superior fatigue resistance beyond 10 5 cycles and outstanding frequency stability at 1–200 Hz. Our work offers a novel way for designing dielectric capacitors and also proves that BNST-BMH is indeed a great hopeful dielectric energy storage material in pulse power electronics.