A Combined Optimization Strategy for Improvement of Comprehensive Energy Storage Performance in Sodium Niobate-Based Antiferroelectric Ceramics

Sodium niobate (NaNbO₃, NN)-based lead-free antiferroelectric (AFE) ceramics are currently the focus of most attention on account of their outstanding energy storage density. Nevertheless, the high loss energy density (W_loss) by unique field-induced AFE-ferroelectric (FE) phase transition in pure NN ceramic and low breakdown electric field (E_b) largely restrict their practical application. Here, a combined optimization strategy was aimed at ameliorating energy storage characteristics of NN-based ceramics. First, the introduction of BiFeO₃-SrTiO₃ binary solid solution in pure NN ceramics destroys the long-range polar ordering and reduce the tolerance factor (t), thus reducing the polarization hysteresis, stabilizing the AFE phase and enhancing the energy storage efficiency. Then, the two-step sintering method was used to improve the compactness of ceramics and reduce the grain size. Finally, the VPP method was used to reduce the porosity, and thin the ceramic disk to a thickness of ∼100 μm. The high compactness and small thickness could effectively enhance the maximum breakdown electric field of ceramics. Ultimately, the optimum energy storage characteristics were obtained by the improvement of a combined optimization strategy, namely, an exceptional recoverable energy storage density (W_rec = 5.29 J/cm³) and efficiency (η = 82.1%) at a very high breakdown electric field (E_b = 380 kV/cm). This combined optimization strategy establishes a universal approach to ameliorate the energy storage characteristics of NN-based AFE ceramics for energy storage.