Simultaneously achieving large energy density and high efficiency in NaNbO₃-(Sr,Bi)TiO₃-Bi(Mg,Zr)O₃ relaxor ferroelectric ceramics for dielectric capacitor applications

High-performance dielectric materials, the critical candidate of multilayer ceramic capacitors, are urgently needed for advanced energy storage or pulse power technologies and applications. However, it is still challenging to simultaneously realize high energy storage density (W_rec) and high efficiency (η) in one material. In this study, a novel NaNbO₃-based 0.88(0.85NaNbO₃-0.15Sr_0.7Bi_0.2TiO₃)-0.12Bi(Mg_0.5Zr_0.5)O₃ (NN-SBT-BMZ) relaxor ferroelectric ceramic was designed based on the domain structure and band gap engineering. An enhanced disorder degree and increased inherent electronic band gap was realized though the formation of the NN-SBT-BMZ complex solid solution. The resultant materials present enhanced linearity of the polarization-electric field relationship and breakdown strength. As a result, an ultrahigh energy storage density of 7.59 J cm⁻³ and a high energy storage efficiency of 81.3% are achieved at the same time. NN-SBT-BMZ also displays excellent temperature stability (an ultrawide range of −120 to 180 °C), frequency stability (10-150 Hz) and cycle stability (up to 10⁶ cycles). In addition, charge-discharge tests indicate that the sample shows outstanding power density (76.78 MW cm⁻³) with an ultrafast discharge rate (t_0.9 ∼ 35 ns). The abovementioned performances demonstrate that the designed NN-SBT-BMZ ceramic is very promising for dielectric capacitor applications.