Composition design strategy for high energy storage property in lead-free (Bi, Na)TiO3 ceramics

Lead-free dielectric ceramic capacitors have attracted substantial attention for high pulsed power technologies, but achieving a large recoverable energy storage density ( W rec ) with high efficiency ( η ) and good thermal stability remains a bottleneck. In this work, we address this challenge in (Bi,Na)TiO 3 -based relaxor ferroelectric through a composition design strategy that induces local structure heterogeneity. This heterogeneity is created from the local random field/stress of the chemical modifiers due to different valence states and ionic sizes, which promotes the formation of polar nano-regions (PNRs). These PNRs minimize the energy barrier, resulting in an excellent energy storage performance, W rec of 8.53 J/cm 3 and η of 80.7 %. Moreover, the material exhibits breakthrough thermal stability, maintaining a W rec ≈ 3.41 ± 0.40 J/cm 3 and η  ≈ 82.2 ± 8.2 % over a wide temperature range up to 240 °C. This study provides a path for designing advanced relaxor ferroelectric dielectric ceramic capacitors for energy storage applications.