Structure and dielectric properties of pyrochlore–fluorite biphase ceramics in the Bi₂O₃–ZnO–Nb₂O₅ system

The structure and dielectric properties of Bi₂O₃–ZnO–Nb₂O₅-based ceramics with pyrochlore–fluorite biphase structure were investigated. Mixed-sintered ceramics were prepared by two precalcined constituents in the system of x[Bi_1.5Zn_0.5(Zn_0.5Nb_1.5)O₇]−(1 − x)Bi_3/4Nb_1/4O_7/4 (0.05 ≤ x ≤ 0.35), where Bi_1.5Zn_0.5(Zn_0.5Nb_1.5)O₇ is a cubic pyrochlore (α) and Bi_3/4Nb_1/4O_7/4 is a defect cubic fluorite (F). The phase composition of the mixed-sintered ceramics were characterized as a biphasic structure with a distorted pyrochlore (β) and a fluorite (F) coexisting. The phase ratio of β pyrochlore and F fluorite is related to the chemical composition x. The dielectric properties of the ceramics gradually change with their structure.