Synergistic Relaxor Doping and Multilayer Engineering Unlocking Superior Energy Storage in Lead-Free NaNbO3-based Ceramic Capacitors

The urgent need for sustainable and green energy storage has intensified the demand for high-performance, lead-free dielectric capacitors that couple high power density with ultra-fast charge-discharge characteristics. Herein, a novel lead-free relaxor antiferroelectric ceramic, ( 1-x )[0.9NaNbO 3 -0.1BiFeO 3 ]- x Bi(Mg 2/3 Nb 1/3 )O 3 (NN-BF-BMN), was designed by incorporating BMN as a third component to the NN-BF matrix. This synergistic approach of BMN incorporation demonstrates inducing relaxor antiferroelectric characteristics, enhancing polarization response and enabling superior energy storage performance. Resultantly, the 0.9(NN-BF)-0.1BMN bulk ceramic achieves an excellent recoverable energy density ( W rec ) of 7.3 J/cm 3 and a high efficiency ( η ) of 86.6% under an electric field ( E b ) of 720 kV/cm. The optimized composition with x = 0.10 was further selected for multilayer ceramic capacitors (MLCCs) fabrication via tape casting. The MLCCs revealed a breakthrough in energy storage performance, exhibiting an ultrahigh W rec of 12.2 J/cm 3 with an outstanding η of 89.6% at a high E b of 920 kV/cm along with thermal stability across the broader temperature range from 30 to 150 °C with little variation in W rec (< 7.1 %) and η (< 5.7 %). Furthermore, a robust discharge time ( t 0.9 = 19.2 ns), and ultra-high current density ( C D = 1598.7 A/cm 2 ) along with substantial power density ( P D = 263.8 MW/cm 3 ) represent a promising lead-free environmentally friendly candidate​ for next-generation advanced pulsed power applications.