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 (Wrec) 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 $${\rm{B}}{{\rm{a}}_{0.105}}{\rm{N}}{{\rm{a}}_{0.325}}{\rm{S}}{{\rm{r}}_{0.245 - 1.5x}}{_{0.5x}}{\rm{B}}{{\rm{i}}_{0.325 + x}}{\rm{Ti}}{{\rm{O}}_3}$$ Ba 0.105 Na 0.325 Sr 0.245 − 1.5 x □ 0.5 x Bi 0.325 + x TiO 3 ($${\rm{BN}}{{\rm{S}}_{0.245 - 1.5x}}{_{0.5x}}{{\rm{B}}_{0.325 + x}}{\rm{T}}$$ BNS 0.245 − 1.5 x □ 0.5 x B 0.325 + x T , x = 0, 0.02, 0.04, 0.06, and 0.08) lead-free ceramics are selected as the representative. The $${\rm{BN}}{{\rm{S}}_{0.245 - 1.5x}}{_{0.5x}}{{\rm{B}}_{0.325 + x}}{\rm{T}}$$ BNS 0.245 − 1.5 x □ 0.5 x B 0.325 + x T ceramics are prepared by using pressureless solid-state sintering and achieve large Wrec (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 Wrec 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 °C is also obtained in $${\rm{BN}}{{\rm{S}}_{0.245 - 1.5x}}{_{0.5x}}{{\rm{B}}_{0.325 + x}}{\rm{T}}$$ BNS 0.245 − 1.5 x □ 0.5 x B 0.325 + x T (x = 0.06) ceramics. The excellent performances can be attributed to the A-site defect engineering, which can reduce remnant polarization (Pr) and improve the thermal evolution of polar nanoregions (PNRs). This work confirms that the $${\rm{BN}}{{\rm{S}}_{0.245 - 1.5x}}{_{0.5x}}{{\rm{B}}_{0.325 + x}}{\rm{T}}$$ BNS 0.245 − 1.5 x □ 0.5 x B 0.325 + x T (x = 0.06) ceramics are desirable for advanced pulsed power capacitors, and will push the development of a series of Bi0.5Na0.5TiO3 (BNT)-based ceramics with high Wrec and high-temperature stability.