Ultrahigh Energy Storage Density and Efficiency in Bi 0.5 Na 0.5 TiO 3 -Based Ceramics via the Domain and Bandgap Engineering.

Environmentally friendly lead-free dielectric ceramics have attracted wide attention because of their outstanding power density, rapid charge/dischargerate, and superior stability. Nevertheless, as a hot material in dielectric ceramic capacitors, the energy storage performance of Na _0.5 Bi _0.5 TiO ₃ -based ceramics has been not satisfactory because of their higher remnant polarization value and low dielectric breakdown strength, which is a problem that must be urgently overcome. In this work, the (1 - x ) (0.6Na _0.5 Bi _0.5 TiO ₃ - 0.4Sr _0.7 Bi _0.2 TiO ₃ ) - x Ba(Mg _1/3 Ta _2/3 )O ₃ (BNST- x BMT) systems were designed based on a dual optimization strategy of domain and bandgap to solve the above problems. As a result, a record-breaking ultrahigh energy density and excellent efficiency ( W _rec = 8.58 J/cm ³ , η = 93.5%) were obtained simultaneously under 565 kV/cm for the BNST-0.08BMT ceramic. The introduction of Sr _0.7 Bi _0.2 TiO ₃ induces the formation of nanodomains in BNT-based ceramics, leading to slim P - E curves, and the further modification of Mg/Ta reduces the grain sizes and increases the bandgap width, resulting in significant enhancement of the dielectric breakdown strength. Moreover, excellent stability and superior discharge performance ( W _d = 4.7 J/cm ³ , E = 320 kV/cm) in the BNST-0.08BMT ceramic were also achieved. The results suggest that the BNST-0.08BMT ceramic shows potential applicability for dielectric energy storage ceramics. Simultaneously, the composition-design concept in the system provides a good reference for the further development of ceramic dielectric capacitors.