Remarkably enhanced dielectric stability and energy storage properties in BNT-BST relaxor ceramics by A-site defect engineering for pulsed power applications

Lead-free bulk ceramics for advanced pulsed power capacitors show relatively low recoverable energy storage density (W_rec) especially at low electric field condition. To address this challenge, we propose an A-site defect engineering to optimize the electric polarization behavior by disrupting the orderly arrangement of A-site ions, in which Ba_0.105Na_0.325Sr_0.245-1.5x▯_0.5xBi_0.325+xTiO₃ (BNS_0.245-1.5x▯_0.5xB_0.325+xT, x = 0, 0.02, 0.04, 0.06, and 0.08) lead-free ceramics are selected as the representative. The BNS_0.245-1.5x▯_0.5xB_0.325+xT ceramics are prepared by using pressureless solid-state sintering and achieve large W_rec (1.8 J/cm³) at a low electric field (@110 kV/cm) when x = 0.06. The value of 1.8 J/cm³ is super high as compared to all other W_rec in lead-free bulk ceramics under a relatively low electric field (< 160 kV/cm). Furthermore, a high dielectric constant of 2930 within 15% fluctuation in a wide temperature range of 40-350 ℃ is also obtained in BNS_0.245-1.5x▯_0.5xB_0.325+xT (x = 0.06) ceramics. The excellent performances can be attributed to the A-site defect engineering, which can reduce remnant polarization (P_r) and improve the thermal evolution of polar nanoregions (PNRs). This work confirms that the BNS_0.245-1.5x▯_0.5xB_0.325+xT (x = 0.06) ceramics are desirable for advanced pulsed power capacitors, and will push the development of a series of Bi_0.5Na_0.5TiO₃ (BNT)-based ceramics with high W_rec and high-temperature stability.