Structure and dielectric properties of Bi2O3–ZnO–CaO–Ta2O5 ceramics

The effects of chemical substitution of Ca2+ cation on the structure and the microwave dielectric properties of BiZnTa-based ceramics were investigated. The relations between B-site partially substituting in Bi2(Cay/3Zn2/3−y/3Ta4/3)O7 and dielectric properties especially the temperature coefficient of dielectric constant were evaluated. The phase structure was studied by XRD and microstructure by SEM techniques. The crystal structure of the un-substituted Bi2(Zn1/3Ta2/3)2O7 was characterized as monoclinic zirconolite-like structure. With increasing amount of Ca2+ cation substitution, the crystal structure gradually transforms from monoclinic zirconolite-like structure to a co-existing phase structure with fluorite and BCT phase.