Shijie Yin, Yuxuan Dai, Yujia Qing, Huajie Luo, Shuhao Wang, Ji Zhang, Shan‐Tao Zhang
Abstract Dielectric ceramics with tetragonal tungsten bronze (TTB) structure have attracted great attention in energy storage owing to their complicated crystal structure and tunable electrical properties. Herein, the end‐member Bi 0.5 Na 0.5 TiO 3 (BNT) was incorporated into Sr 0.6 Ba 0.4 Nb 2 O 6 (SBN) ceramics to enhance the dielectric relaxation and energy storage performance without changing the TTB structure. The random substitution at A/B sites in SBN improved the lattice distortion, thereby breaking the long‐range ferroelectric orders and generating the highly dynamic polar nano‐regions. Finally, the ceramic sample with 8 mol% BNT delivered a high recoverable energy density ( W rec ) of 5.5 J/cm 3 and an impressive efficiency ( η ) of 88.7% when the applied electric field reached 450 kV/cm. Moreover, this composition showed very high reliability in W rec and η over a wide temperature range and good charging–discharging behavior. These results confirm the applicability of SBN‐BNT ceramics in advanced dielectric capacitors for energy storage applications.