Advancing energy storage capabilities in 0.7BNST_(1-x)-0.3BLMN_x lead-free dielectric ceramic materials

Lead-free ferroelectric ceramics with a composition of 0.7(Bi_0.5Na_0.5)_0.7Sr_0.3Ti_(1-x)O₃-0.3Ba_0.94La_0.04(Mg_1/3Nb_2/3)_xO₃ (abbreviated as 0.7BNST_(1-x)-0.3BL(MN)_x, 0 ≤ x ≤ 0.12) were prepared using solid-phase sintering method, involving co-substituting at A and B sites. High recoverable energy density (W_rec) of 3.54 J/cm³ and energy efficiency (η) 85.49% are achieved at an electric field of 270 kV/cm. Furthermore, these ceramics exhibited excellent temperature and cycle stability at 120 kV/cm (within 25 °C–150 °C, W_rec fluctuation range <14 %; under 1∼10⁶ cycles, the W_rec fluctuation range <5 %). In terms of dielectric performance, they exhibited a high dielectric constant (ε_r∼4540), an extremely low dielectric loss tanδ of <0.04 (30 °C–300 °C), and good temperature stability with Δε/ε_{150 °C} ≤ ±15 % (−19.5 °C–233.4 °C). During the charging and discharging process, these ceramics demonstrated a high energy density (W_d) of 1.2 J/cm³, a power density (P_D) of 61.7 MW/cm³, and an extremely short discharge time (t_0.9) of approximately ∼0.11 μs. This study has improved the dielectric energy storage performance of BNT-based lead-free piezoelectric ceramics, making them suitable for use in pulse power devices.