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 )Bi 0.5 Na 0.5 TiO 3 - x BaTiO 3 - y Bi 0.2 Sr 0.7 TiO 3 lead-free relaxor ferroelectrics have been explored for energy storage property. Particularly slim polarization hysteresis ( P - E ) loops are observed in 0.655Bi 0.5 Na 0.5 TiO 3 -0.065BaTiO 3 -0.28Bi 0.2 Sr 0.7 □ 0.1 TiO 3 (6.5BNBT-BST) at ambient temperature resulting in a giant recoverable energy density ( W rec = 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 Bi 0.2 Sr 0.7 TiO 3 (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 Bi 0.2 Sr 0.7 TiO 3 tailoring by A-site vacancies is a potential route when designing new relaxor ferroelectrics for energy-storage applications.