Study of structure and dielectrc properties of non-stoichiometric Bi2O3-ZnO-Nb2O5 ceramics

Bi-based ceramics with pyrochlore structure exhibit interesting dielectric properties such as high dielectric constant and small dielectric loss at high frequency and low firing temperature. Structure and dielectric properties of non-stoichiometric ceramics Bi1.5-xZnNb1.5O7-1.5x (with x=-0.25 similar to 0.6) were investigated. The compounds departured from stoichiomeric compositions lead to structural parameters change. The second phase appeared when x >= 0.4. The lattice parameters of cubic pyrochlore Bi1.5-xZnNb1.5O7 and grain size decreased as x increased. The experimental results show that dielectric constant decrease with increasing of their value. The dielectric relaxation and defect resulting from non-stoichiometric ceramics Bi1.5-xZnNb1.5O7-1.5x were discussed.