Ba²⁺/Sr²⁺ regulation in A-site vacancy-engineered B_0.015+1.5xS_{0.245-1.5x0.03}BNT relaxor ceramics for energy storage

A-site vacancy-engineered Ba0.015+1.5xSr0.245-1.5x square 0.03Bi0.385Na0.325TiO3 (B0.015+1.5xS0.245-1.5x square 0.03BNT, x = 0, 0.012, 0.024, 0.036, 0.048, 0.06) ceramics were fabricated by a solid-state reaction method. The effect of Ba/Sr regulation on the structure, polarization, and dielectric energy storage properties of the B0.015+1.5xS0.245-1.5x square 0.03BNT ceramics were investigated. With the increase of the x value, the lamellar microdomains transform into the coexistence of banded domains and nanodomains. A double-like P-E hysteresis loop with a high polarization value (P-max > 35 mu C/cm(2)) can be obtained at a very low electric field of 60 kV/cm. Consequently, a large recoverable energy storage density (W-rec = 2.33 J/cm(3)) can be achieved at a relatively low applied electric field of 130 kV/cm. The designed B0.087S0.173 square 0.03BNT also exhibits high dielectric constant (epsilon(r) = 3510 @150 degrees C&1 kHz) with suitable temperature capacitance coefficient (TCC150 degrees C = +/- 15%) over the temperature range of 17 degrees C similar to 382 degrees C. These findings provide a novel vacancy-engineered avenue towards the design of BSBNT relaxor ceramics with high W-rec and good stability for low-voltage driven high-temperature pulsed power capacitor.