Boosting energy storage performance in Ba_0.8Sr_0.2Zr_0.1Ti_0.9O₃–Na_0.5Bi_0.5TiO₃ lead-free nanoceramics through polar nanoregions and grain refinement engineering

Polar nanoregions and grain refinement engineering are alternative methods to develop comprehensive energy storage performance ceramic materials. In our work, Ba_0.8Sr_0.2Zr_0.1Ti_0.9O₃ (BSZT) and Na_0.5Bi_0.5TiO₃ (NBT) powders with average particle sizes of 200 nm and 50 nm were fabricated by a wet chemical method and BSZT-xNBT (x = 0, 0.02, 0.04, 0.06, 0.08 wt%) ceramic samples were prepared by utilizing the two powders. The systematic study confirmed that pure BSZT ceramics possessed pseudocubic phase, and the coexistence of tetragonal phase (T) and rhombic phase (R) was observed at x = 0.06. PFM and TEM examinations revealed that the domain structure of BSZT-0.06NBT ceramics had transformed from ferroelectric domains into polar nanoregions. Additionally, the sintering behavior of ceramics could be effectively improved by the addition of NBT with small particle size, and the dense fine-grained ceramics with 198 nm were obtained when the NBT amount reached up to 0.06. BSZT-0.06NBT ceramics sintered at 980 °C exhibit a high dielectric constant of 3620 and a low dielectric loss of 0.02 at Curie temperature. Ferroelectric hysteresis loops become slimmer and slimmer with the increased x, which may be ascribed to the enhancement of relaxor behavior and domain transition in the ceramics. For the composition of x = 0.06, the maximum energy storage density of 1.72 J cm⁻³ and a moderate energy storage efficiency of 78.2% were realized under 18.32 kV mm⁻¹. This work suggests that BSZT-0.06NBT relaxor ferroelectric ceramics are expected to be applied in the energy storage field.