Phase Structure, Crystal Chemistry and Dielectric Property of Oxygen-site Doped Bi_1.5ZnNb_1.5O₇ Ceramics

By substituting F^- for O^2-, Bi_1.5-xCa_xZnNb_1.5O₇ (0.00≤x≤0.30, abbreviated as C-x), Bi_1.5-xCa_xZnNb_1.5O_7-yF_y (0.00≤x≤0.20, abbreviated as CF-x) ceramics samples were prepared by conventional solid-state reaction method. The way of defect compensation, doping position substitution position, the influence of F^- dopant on phase structure, crystal chemistry and dielectric properties of Ca-doped Bi_1.5ZnNb_1.5O₇ (abbreviated as α-BZN) ceramics samples were investigated. The results revealed that F^- incorporation declined the solid solution of Ca²⁺ in α-BZN, and F^- was dissolved into the oxygen site of BO₆ octahedral. In the same amount of Ca²⁺ dopant, with F^- incorporation, both the dielectric constant and the dielectric loss decreased, which was consistent to the bond valence sums for A₄O′. Compared with Ca²⁺ doping, the bond valence sums for A₄O′ of F^- and Ca²⁺ co-doping increased. The shift of the dielectric constant peak to higher temperature could be associated with the increase in activation energy due to the addition of F^-.