Structural Characterization for Ceramic Pyrochlores of Bi-Zn-Nb-O

Ceramic pyrochlores, the basis of Bi2O3-ZnO-Nb2O5 (BZN), have dielectric properties of great interest, such a high dielectric constant (ε), a low dielectric loss tangent (tan δ) and a low coefficient of capacitance with temperature (TCC). The system has two main phases, Bi1,5ZnNb1,5O7 (α) and Bi2Zn0,67Nb1,33O7 (β) with cubic and orthorhombic crystal structures, and very different dielectric properties. The purpose of this article was to synthesize chemically homogeneous ceramic pyrochlores BZN-α and BZN-β, using the ceramic method in obtaining nanopowders and their characterizations by scanning electron microscopy (SEM), X-Ray Diffraction (XRD), and the Rietveld refinement method of the structures. The powders were weighed in stoichiometric proportions and calcined at 700 °C/2h, they were sintered at 900, 950 and 1000 °C/2h. A pure BZN-α phase was obtained, while the BZN-β has remained in phases as Bi5Nb3O15 and BiNbO4.