Ultrahigh Energy‐Storage in Dual‐Phase Relaxor Ferroelectric Ceramics

High-performance dielectric energy-storage ceramics are beneficial for electrostatic capacitors used in various electronic systems. However, the trade-off between reversible polarizability and breakdown strength poses a significant challenge in simultaneously achieving high energy density and efficiency. Here a strategy is presented to address this issue by constructing a dual-phase structure through in situ phase separation. (Bi0.5Na0.5)TiO3-BaTiO3-based relaxor ferroelectric ceramics are developed, creating a grain-separated dual perovskite phase structure using a facile solid-state reaction method. These ceramics feature two interactive relaxor phases with diversified nanoscale polar structures and heterogeneous grain boundaries, synergistically contributing to high polarization with low hysteresis, substantially increased resistivity, and suppressed electrostrain. Remarkably, a record-high energy density of 23.6 J cm-3 with a high efficiency of 92% under 99 kV mm-1 is achieved in the bulk ceramic capacitor. This strategy holds promise for enhancing overall energy-storage performance and related functionalities in ferroelectrics.