Lead-free ceramic capacitors are widely applied for novel pulse power supply systems owing to their environmental friendliness, high power density, and fast charge−discharge characteristics. Nevertheless, the simultaneous achievement of a higher recoverable energy storage density (W rec ) and efficiency (η) is still challenging and must be investigated. To obtain a dielectric capacitor with a high W rec and η, the energy storage characteristics can be improved by reducing the residual polarization and increasing the breakdown strength. In this work, the doping modification of the NaNbO 3 (NN) ceramics is used to produce a local random field to improve the electrical breakdown strength, obtaining a lead-free dielectric capacitor with high energy storage characteristics. According to this strategy, Bi(Ni 0.67 Ta 0.33 )O 3 is added to NN, and an ultrahigh E b is obtained so that the ceramics have ideal W rec and η values. 0.85NN−0.15Bi(Ni 0.67 Ta 0.33 )O 3 has a very high W rec (5.53 J cm −3 ) and η (82.0%) at 575 kV cm −1 . Furthermore, the energy storage characteristics of the ceramics exhibit good thermal stability and frequency stability that are superior to those of most of the lead-free dielectric capacitors reported to date. In particular, the 0.85NN−0.15 Bi 0.5 Na 0.5 TiO 3 (0.85NN−0.15BNT) ceramic also allows an ultrafast discharge time (t 0.9 = 27.5 ns), large current density (C D = 506.42 A cm −2 ), and higher power density (P D = 35.45 mW cm −3 ). These results indicate that (1 − x)NN−xBNT ceramics are promising for applications in lead-free dielectric ceramic capacitors with a high energy storage density and conversion efficiency.
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