Multiscale structural engineering enables superior energy storage in tetragonal tungsten bronze relaxor ferroelectrics

Lead-free relaxor ferroelectric ceramics are promising for pulsed-power systems due to their ultrafast discharge and high-power density, yet their practical use remains limited by low breakdown strength and insufficient energy-storage density. Here, we report Ba2La1−xBixTi2Nb3O15 ceramics with a tetragonal tungsten bronze structure, which achieve a recoverable energy density of 14.39 J/cm3 and an efficiency of 87.69% under an ultrahigh field of 1400 kV/cm–one of the highest recoverable energy density values reported for bulk tetragonal tungsten bronze structured ceramics. By combining experiments, first-principles calculations, and finite-element simulations, we unravel a multiscale structural optimization mechanism. Bi3+ incorporation induces oxygen-octahedral distortion that disrupts long-range order and enhances relaxation behavior. Concurrent grain refinement and band gap widening substantially raise the breakdown strength, leading to superior energy-storage properties. Moreover, the material exhibits excellent stability against variations in temperature, frequency, and fatigue cycles. This work establishes a generally applicable multiscale structural-engineering strategy for tetragonal-tungsten-bronze dielectrics with high energy storage performance. Through multiscale structural engineering, this work achieves a high recoverable energy density of 14.39 J/cm3 (one of the highest reported for bulk tetragonal tungsten bronze ceramics) and an efficiency of 87.69% in Ba2LaTi2Nb3O15-based ceramics.