High Energy Storage Performance in BiFeO3‐Based Lead‐Free High‐Entropy Ferroelectrics

Abstract Dielectric capacitors are widely used in advanced electrical and electronic systems due to the rapid charge/discharge rates and high power density. High comprehensive energy storage properties are the ultimate ambition in the field of application achievements. Here, the high‐entropy strategy is proposed to design and fabricate single‐phase homogeneous (Bi 0.5 Ba 0.1 Sr 0.1 Ca 0.2 Na 0.1 )(Fe 0.5 Ti 0.3 Zr 0.1 Nb 0.1 )O 3 ceramic, the hierarchical heterostructure including rhombohedral‐tetragonal multiphase nanoclusters and locally disordered oxygen octahedral tilt can lead to the increased dielectric relaxation, diffused phase transition, diverse local polarization configurations, grain refinement, ultrasmall polar nanoregions, large random field, delayed polarization saturation and improved breakdown field. Accordingly, a giant W rec ≈13.3 J cm −3 and a high η ≈78% at 66.4 kV mm −1 can be simultaneously achieved in the lead‐free high‐entropy BiFeO 3 ‐based ceramic, showing an obvious advantage in overall energy‐storage properties over BiFeO 3 ‐based lead‐free ceramics. Moreover, an ultrafast discharge rate ( t 0.9 = 18 ns) can be achieved at room temperature, concomitant with favorable temperature stability in the range of 20–160 °C, due to the enhanced diffuse phase transition and fast polarization response. This work provides a feasible pathway to design and generate dielectric materials exhibiting high comprehensive energy‐storage performance.