Enhanced energy storage performance in Na(Nb,Ta)O3-doped Ba(Ti,Ca)O3-based ceramics through bidirectional optimization strategy

(1-x)(0.9Ba 1.003 Ti 0.97 Ca 0.03 O 3 –0.1(Bi 0.51 Na 0.47 ) 0.94 Ba 0.06 TiO 3 )-xNa(Nb 0.85 Ta 0.15 )O 3 ( x  = 0.03–0.15) ceramics were designed and fabricated through a bidirectional optimization strategy using traditional solid reaction method. The results revealed that the introduction of Na(Nb 0.85 Ta 0.15 )O 3 increased the vacancy concentration at the A site , conducing to improved polarization and reduced grain size. The substitution at the B site disrupted the long-range ordered ferroelectric domains and generated polar nanodomains, leading to enhanced relaxation behavior. The optimum energy storage density of 3.57 J/cm 3 and efficiency of 87.5% were simultaneously achieved under the electric field of 220 kV/cm in the sample with x  = 0.09. Moreover, it also exhibits extremely high-power density (∼57 MW/cm 3 ), ultrafast discharge time (∼103 ns), high discharge density (1.35 J/cm 3 ), along with excellent temperature (30‒120 °C) and frequency stability (1‒100 Hz) under the equivalent electric field of 120 kV/cm. This novel design strategy provides theoretical guidance for the development of advanced electrical energy storage devices.