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 rela-tively 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 degrees C to 200 degrees 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.