Achieving excellent energy storage performance at moderate electric field in Ca0.85Bi0.05Sm0.05TiO3-modified BiFeO3-based relaxor ceramics via multiple synergistic design

Lead-free BiFeO3-based capacitors have attracted considerable attention owing to their excellent energy storage potential. Herein, we report 0.7(0.67BiFeO3–0.33BaTiO3)–0.3Ca0.85Bi0.05Sm0.05TiO3 (BF–BT–CBST) relaxor ceramics with an excellent recoverable energy density (5.26 J/cm3) and high efficiency (82.4%) at 300 kV/cm, which is the optimal energy storage performance under moderate electric field among lead-free ceramic capacitors. The introduction of CBST suppressed the early polarization saturation of BF-based ceramics while maintaining a particularly high polarization of 41.5 μC/cm2 under 300 kV/cm. In addition, the refined grain size and increased bandgap improved the breakdown electric field. BF–BT–CBST ceramics demonstrated a record-breaking discharge rate of t0.9 ∼ 27 ns due to the generation of highly dynamic polar nanoregions that are sensitive to electric fields. CBST-modified ceramics also showed outstanding thermal stability (25 °C–160 °C), frequency stability (1–300 Hz), and fatigue endurance (105 cycles). Our results indicate that CBST facilitates the preservation of high polarization and is a good additive for the BF-based energy storage materials and may also be applied in other material systems.