Enhanced energy storage performance of Bi0.5Na0.5TiO3-based ceramics via grain tuning and relaxor construction

Relaxor ferroelectrics have become competitive candidates in energy storage applications owing to their relatively high maximum polarization, high breakdown strength, and relatively low remnant polarization. Here, Bi0.5Na0.5TiO3 (BNT) with large polarization was selected as the base composition, and Sr0.7Bi0.2Ti0.8Hf0.2O3 (SBTH), as a dopant, was added into BNT to improve its relaxor behavior and decrease the grain size. A series of (1-x)Bi0.5Na0.5TiO3-xSr0.7Bi0.2Ti0.8Hf0.2O3 (abbreviated as (1-x)BNT-xSBTH, x = 0.1, 0.2, 0.3 and 0.4) ceramics were synthesized. The addition of SBTH resulted in the increase in structural disorder, as confirmed by the red-shift in Raman spectra, the enhancement of the relaxor characteristic and the fast response of the domains in local poling measurements. As a result, excellent energy storage properties (with the recoverable energy storage density of 5.5 J/cm3 and efficiency of 85.9 % at 410 kV/cm) were realized in the 0.6BNT-0.4SBTH sample. Moreover, the sample also exhibited excellent thermal stability (20 °C to 200 °C) and frequency insensitivity (0.5–500 Hz). These results suggest that BNT-based relaxor ferroelectric ceramics modulated by SBTH possess great potential in dielectric energy-storage capacitors.