Influence of sintering aid on structural and electrical properties of Na(Nb_0.7Ta_0.3)O₃ ceramics

Lead-free NaNbO₃-based antiferroelectric ceramics are promising materials for energy storage applications due to their double hysteresis loops and lightweight properties. However, the high sintering temperatures (usually > 1350 °C) and poor microstructures, restrict their usage. In the present study, five different sintering aids (ZnO, MnO₂, MgO, CuO and Bi₂O₃) in concentrations of 0.5, 1.0, and 1.5 wt% were added to Na(Nb_0.7Ta_0.3)O₃ (NNT30) antiferroelectric ceramics, to systematically investigate their effects on phase evolution, dielectric properties and energy storage performance. Among all sintering aids and their concentrations, NNT30-Mn0.5 exhibited the optimal performance, achieving a 7.4% reduction in sintering temperature, a relative density of 95%, and a well-defined double P-E hysteresis loop, confirming stable antiferroelectric phase behavior. More importantly, well-defined double P-E hysteresis loops, contributed to a recoverable energy storage density of 2.7 J/cm³, corresponding to a 300% improvement over pure NNT30 (0.7 J/cm³). The enhanced performance is attributed to the combined effect of sustained AFE phase stability, reduced dielectric loss, increased resistivity, and enhanced microstructural densification. These results demonstrate that MnO₂ is an effective sintering aid for developing high-performance lead free antiferroelectric ceramics for energy storage applications.