Boosting low-field polarization and relaxation via Bi0.5Na0.5TiO3 doping in NaNbO3 Ceramics

The ongoing miniaturization and integration of electronic devices are imposing stringent demands on the energy storage performance of dielectric ceramics under low electric fields. NaNbO 3 (NN), an environmentally friendly and low-cost antiferroelectric (AFE) dielectric ceramic, shows significant potential in this context. However, the instability of its AFE P -phase under low electric fields results in unfavorable polarization behavior, which limits its energy storage performance. To overcome this limitation, we introduced the perovskite ferroelectric material Bi 0.5 Na 0.5 TiO 3 (BNT) with high maximum polarization ( P max ) into the NN matrix. With increasing BNT content, the crystal structure transitions from the AFE P -phase to a more stable AFE R -phase. This phase transition is accompanied by enhanced relaxor behavior, which in turn leads to slimmer polarization–electric field ( P-E ) hysteresis loops and a reduced remnant polarization ( P r ). In addition, the P max of NN ceramic is also enhanced,. The 0.85NaNbO 3 -0.15Bi 0.5 Na 0.5 TiO 3 (NN-0.15BNT) ceramic exhibits a P max of 16.73 μC/cm 2 at 100 kV/cm, a value approximately three times higher than that of pure NN ceramic ( P max  = 5.63 μC/cm 2 ). Consequently, under a low electric field of 100 kV/cm, the NN-0.15BNT ceramic achieves a recoverable energy storage density ( W rec ) of 0.65 J/cm 3 and an efficiency ( η ) of 87.6%, representing nearly fourfold ( W rec  = 0.16 J/cm 3 for NN) and twofold ( η  = 45.1% for NN) enhancements, respectively, over pure NN. The achieved performance is competitive with other lead-free relaxor ferroelectrics under similar low-field conditions. The synergistic optimization strategy proposed in this work provides a valuable guideline for designing high-performance energy storage ceramics suitable for low-electric-field applications.