Excellent Energy Storage Performance Achieved in Sr(Sc_0.5Nb_0.5)O₃-Doped Bi_0.5Na_0.5TiO₃-Based Lead-Free Relaxor Ferroelectric Ceramics

Dielectric energy storage ceramics have received significant attention as the primary component for high-pulse power capacitors. Currently, their development is limited by poor energy storage performance, which affects the miniaturization and lightweighting of electronic devices. In this study, a comprehensive optimization approach was adopted to enhance the storage performance (recoverable energy density W_rec and conversion efficiency η) of 0.8Bi_0.5Na_0.5TiO₃-0.2NaNbO₃ (BNT-NN) through component optimization design and repeated rolling process (RRP). A series of Sr(Sc_0.5Nb_0.5)O₃ (SSN) was introduced into BNT-NN to modulate the phase structure and improve the relaxation properties. The repeated rolling process was applied to refine the grain and enhance the dense property to boost the breakdown of the electric field. Following the mentioned strategy, we have succeeded in simultaneously obtaining ultrahigh W_rec (∼7.22 J·cm^-3) and outstanding η (∼95.32%) under 515 kV·cm^-1 for 0.8(BNT-NN)-0.2SSN (RRP) ceramic. More importantly, the ceramic sample possesses outstanding stability over a wide range of temperatures (25-60 °C) and frequencies (1-100 Hz). This study proposes a viable route to better performance of dielectric ceramics for energy storage, and the outstanding performance of the 0.8(BNT-NN)-0.2SSN (RRP) ceramic indicates its promising applicability in high- and high-pulse-power electronic devices.