Enhancing energy storage performance of antiferroelectric NaNbO3-Bi1/3SbO3 ceramics guided by first-principles calculations

The application of Sodium niobate (NaNbO₃, NN) ceramics with antiferroelectric (AFE) crystal phase faces the severe limitations in low energy density and efficiency due to the instability of the antiferroelectric phase and relatively low breakdown strength. The traditional methods still rely on a large amount of experimental verification. However, the internal mechanism remains unclear. To address this challenge, in the present study, the results of A-site defect engineering from density function theory (DFT) guides to design the modified ingredient of (1-x)NaNbO₃-xBi_1/3SbO₃ ceramics with more stable AFE P phase. The theoretical results indicate that the BiSbO₃ (BS) doping helps to induce a crystal phase transition from the stable ferroelectric (FE) to the more stable AFE state, with an energy difference of 9.762 meV. The main reason is that doping with BS suppresses the distortion index D of BO₆ from 4.39 to 2.86 and increases the θ_c averaged tilting angle from 25.5 to 26.4, thereby significantly stabilizing the AFE P phase. However, this also generates Na vacancies, necessitating the formation of oxygen vacancies to maintain defect balance, which adversely affects the structural stability and breakdown strength of NN. First-principles calculations indicate that inhibiting oxygen vacancy formation raises the bandgap from 1.41 to 2.45 eV, thereby enhancing structural stability and breakdown strength. Guided by these theoretical insights, doped NN ceramics were heat-treated in oxygen atmosphere, and their insulation performance was evaluated. The results confirm the effectiveness of the oxygen vacancy suppression strategy. Ultimately, the experimental findings support our theoretical predictions, providing a strong theoretical and experimental foundation for improving the energy storage performance of NN-based AFE ceramics.