Ultrahigh recoverable energy storage density and efficiency in barium strontium titanate-based lead-free relaxor ferroelectric ceramics

Recently, dielectrics for energy storage have been attracting increasing attention due to their ultrahigh power density. However, the widespread application of dielectrics remains limited by their low energy density. In this work, lead-free single-phase relaxor (1 − x)Ba0.55Sr0.45TiO3-xBiMg2/3Nb1/3O3 [(1 − x)BST-xBMN] (x = 0, 0.05, 0.07, and 0.10) bulk ceramics were prepared by a conventional solid-state reaction process. The dielectric properties, the relaxor behavior, and the energy storage properties were explored in detail. With increasing BMN content, the observed increase in activation energy (Ea) and the decrease in freezing temperature (Tf) indicate that the coupling between polar nano-regions (PNRs) gradually weakened, leading to the decrease in remanent polarization (Pr) and the increase in energy storage efficiency (η). For the composition x = 0.07, the breakdown strength (BDS) significantly increased from 240 kV cm of pure BST to 450 kV cm. Finally, large Wrec (4.55 J cm3) and high η (81.8%) were achieved in 0.93BST-0.07BMN ceramics. The results demonstrate that the (1 − x)BST-xBMN ceramics have superior potential for use in advanced pulsed power capacitors.