High Energy Storage Performance under Moderate Electric Field in Fine-Grain Bi_0.5Na_0.5TiO₃-Based Ceramics

Ceramic-based dielectric capacitors are one of the core components in high-/pulsed-power devices due to the giant power density and ultrafast discharge time. However, the current high recoverable energy density (W_rec) is widely obtained under a huge electric breakdown strength (E_b > 500 kV/cm). Herein, a relaxor ferroelectric ceramic based on Bi_0.5Na_0.5TiO₃-NaNbO₃-BaZrO₃ is prepared and exhibits a high W_rec of 7.7 J/cm³ and a high η of 87.3% under a moderate electric field of 450 kV/cm, which is salient among BNT-based ceramics under the close applied electric field. This is attributed to the enhanced ergodic relaxor state and greatly decreased grain size, enabling a high polarization difference (ΔP) of 39.4 μC/cm² and a large E_b of 464 kV/cm. Furthermore, the sample with optimal composition also possesses excellent reliability of frequency (1-100 Hz), fatigue (up to 10⁶), and temperature (30-180 °C), and a high dynamic discharge energy density (W_d ∼ 4.8 J/cm³). This work provides some effective clues for the further exploitation of lead-free dielectric ceramics with high-capacitive energy storage.