Synergistic relaxor regulation and 0-3 perovskite-pyrochlore composite design for high-performance energy storage in BiFeO3-BaTiO3 ceramics

Lead-free dielectric ceramic capacitors are promising for pulsed-power applications owing to their high power density and rapid charge-discharge capability. However, simultaneously achieving high recoverable energy density ( W rec ) and efficiency ( η ) under moderate electric fields remains challenging. Here, we develop (Na 0.7 La 0.1 )TaO 3 (NLT)-doped 0.67BiFeO 3 -0.33BaTiO 3 (BFBT) ceramics with exceptional energy storage properties through the synergy between relaxor regulation and 0-3 perovskite–pyrochlore composite design. The introduction of NLT is demonstrated to effectively disrupt the long-range ferroelectric order of BFBT and promote the formation of highly dynamic polar nanoregions, significantly minimizing their remanent polarization. When the NLT content exceeds the solid-solution limit, the Bi 2 Ti 2 O 7 pyrochlore secondary phase forms and establishes insulating interfaces that suppress long-range carrier migration and enhance the breakdown strength. Owing to these synergistic effects, the optimized ceramics with the addition of 15% NLT exhibit a large W rec of 3.81 J/cm 3 and a high η of 91% at 330 kV/cm, as well as excellent frequency, thermal, and cycling stability. The synergistic relaxor-regulation and grain-boundary-insulation strategy provides a feasible route for high-performance lead-free ceramic capacitors.