Modulating WeaklyCoupled Polar Nanoregions via DomainEngineering for Ultrahigh Energy Density and X9R-Compliant ThermalStability in Bi0.5Na0.5TiO3‑BasedCeramics

Dielectric ceramic capacitors are critical to advanced power electronics by virtue of exceptional power density and rapid charge/discharge capability. However, achieving high energy storage density and efficiency under harsh thermal environments remains a significant challenge. Herein, a domain-engineering strategy is implemented in Bi_0.5Na_0.5TiO₃ (BNT) ceramics via the incorporation of Ca(Zn_1/3Nb_2/3)O₃ (CZN), which promotes weakly coupled polar nanoregions (PNRs) generating an ergodic relaxor state at ambient temperature. Remarkably, the optimized 0.84BNT–0.16CZN composition achieves a high recoverable energy density (W_rec) of 8.79 J/cm³, efficiency (η) of 84.8% at 584 kV/cm, and an ultrafast discharge time of t_0.9 = 27.9 ns, surpassing most reported lead-free ceramics. Piezoresponse force microscopy confirms dynamic PNRs as the origin of superior energy storage behavior. Moreover, this composition maintains excellent temperature stability (20 to 180 °C) with high W_rec (>3.4 J/cm³) and η (>78.2%). Importantly, it exhibits X9R-compliant dielectric stability, enabling reliable operation across extreme temperatures. All these features demonstrate that the 0.84BNT–0.16CZN ceramic is expected to be widely used in next-generation wide-temperature dielectric capacitors.