Ultrahigh breakdown strength of NaNbO₃‐based dielectric ceramics for high‐voltage capacitor application

Dielectric ceramics have attracted significant attention in power electronic systems, owing to their exceptional charging and discharging speeds, as well as their high power density. However, simultaneously achieving a high recoverable energy density ( W rec ) and high efficiency ( η ) in high‐voltage dielectric ceramics remains a challenge for applications where a high breakdown electric field ( E b ) is required. In this study, high‐quality (1 – x )NaNbO 3 – x Sr 0.7 Bi 0.2 (Mg 1/3 Nb 2/3 )O 3 [(1 – x )NN –x SBMN] ceramics were prepared based on an optimization strategy combining phase structure with microstructural regulation. A quasilinear P–E loop with negligible hysteresis was realized in the ceramic with x = 0.4, excellent W rec of 5.61 J/cm 3 , and high η of 85.1% obtained at a largely improved E b of 710 kV/cm. To the best of our knowledge, the E b of 710 kV/cm is one of the highest values achieved in dielectric ceramics to date. The noticeable reduction in grain size (∼0.95 µm) and increased bandgap improve the E b to an ultra‐high level, which is a crucial factor in high energy storage density. The coexistence of a few antiferroelectric phases and the dominant paraelectric phase is the structural origin of the comprehensive energy‐storage performance improvement. Therefore, our research develops a unique approach to unleash the potential in NaNbO 3 ‐based ceramics, holding great promise for application in high‐voltage dielectric capacitors.