The crystal structures and dielectric properties of Bi2O3 doped SrBi2Ta2O9 ceramics

Ferroelectric materials with Bi-layered structure such as SrBi2Ta2O9 composition with excess x wt.% Bi2O3 (x = 0, 2, and 4) are investigated as the main composition, the effect of excess Bi2O3 content and sintering temperatures on the crystal structure and dielectric characteristics of SrBi2Ta2O9 ceramics are developed. Even 1280 °C is used as the sintering temperature of stoichiometry SrBi2Ta2O9 composition, the X-ray diffraction patterns will show that the SrBi2Ta2O9 phase is coexisted with the raw material of Ta2O5 and the secondary phases of SrBi2O4 and BiTaO4. For SrBi2Ta2O9 composition with excess 2 wt.%- or 4 wt.%-Bi2O3-doped and sintered at 1040 °C, the Ta2O5, SrBi2O4, and BiTaO4 phases are eliminated and only the SrBi2Ta2O9 phase is observed in the X-ray diffraction patterns. It is found that sintering temperatures and excess Bi2O3 content have large influence on the grain growth, the bulk densities, the maximum dielectric constants, and the Curie temperatures of SrBi2Ta2O9-based ceramics.