Enhancing the Energy Storage Performance of Flexible Na_0.5Bi_0.5TiO₃-Based Relaxor Thin Films Through a Relaxor...

Dielectric capacitors are employed in defense and automotive applications owing to their ultrahigh charge-discharge rates. To mitigate the high leakage current density of Na_0.5Bi_0.5TiO₃ (NBT), SrTiO₃ (STO), which exhibits excellent insulation performance, is incorporated into the NBT lattice to enhance both the breakdown field strength and the relaxor characteristics. Furthermore, the ionic radius of Sr²⁺ (0.1180 nm) is slightly larger than the average ionic radius of (NaBi)²⁺ (0.1025 nm). As a result, the introduction of STO induces lattice distortion, disrupts long-range ordering, and promotes the formation of short-range ordered domains, thereby strengthening the relaxor behavior (the relaxation degree γ increased from 1.63 to 1.84). Consequently, the 0.95(Na_0.5Bi_0.5)(Fe_0.02Ti_0.99)O₃-0.05SrTiO₃ thin film achieves a recoverable energy storage density (W_rec) of 43.88 J/cm³ and an efficiency (η) of 73.95%. In addition, the thin film exhibits excellent temperature stability over a range of 10 to 170 °C, good frequency stability from 0.1 to 2.0 kHz, and robust fatigue endurance up to 1 × 10⁸ switching cycles. This work provides reliable technical and theoretical guidance for the application of NBT-based materials in energy storage.