Ultrahigh energy density and improved discharged efficiency in bismuth sodium titanate based relaxor ferroelectrics with A-site vacancy

Novel A-site deficient (1-x-y)Bi0.5Na0.5TiO3-xBaTiO3-yBi0.2Sr0.7TiO3 lead-free relaxor ferroelectrics have been explored for energy storage property. Particularly slim polarization hysteresis (P-E) loops are observed in 0.655Bi0.5Na0.5TiO3-0.065BaTiO3-0.28Bi0.2Sr0.7□0.1TiO3 (6.5BNBT-BST) at ambient temperature resulting in a giant recoverable energy density (Wrec = 1.5 J cm−3) and extremely high efficiency (η = 90%) at 100 kV cm−1, which are closed related to the track of P-E loops. As the addition of Bi0.2Sr0.7TiO3 (BST) content, the ergodic relaxor phase becomes dominant with dynamic polar nano-regions attributed to the absence of ferroelectric domain in the relaxor phase. Furthermore, the recoverable energy density exhibits small variation in elevated temperature where the depressed polarization is compensated by almost hysteresis free loops (η up to 97%). The achievement of these characteristics in P-E loops provides that Bi0.2Sr0.7TiO3 tailoring by A-site vacancies is a potential route when designing new relaxor ferroelectrics for energy-storage applications. [Display omitted] •6.5BNBT-BST displays giant energy densities of 1.5 J cm−3 and efficiencies of 90% at 100 kV cm-1 at RT.•This work provides a new avenue of composition modulation by introducing designed cationic vacancies.•6.5BNBT-BST exhibits weak temperature-dependent behavior and almost hysteresis free loops (η up to 97%).