Microwave dielectric properties of (1 − x)Cu₃Nb₂O₈−xZn₃Nb₂O₈ ceramics

The sintering behavior and microwave dielectric properties of (1 − x)Cu₃Nb₂O₈−xZn₃Nb₂O₈ have been investigated using dilatometry, x-ray diffraction, and a network analyzer. It was found that (1 − x)Cu₃Nb₂O₈−xZn₃Nb₂O₈ ceramics have a much lower melting temperature than Zn₃Nb₂O₈ ceramics without Cu₃Nb₂O₈ additives. Samples sintered at 900 °C for 2 h exhibited densities >97% of the theoretical density. Cu₃Nb₂O₈ acts as a sintering aid. Two phase regions were identified with increasing Zn₃Nb₂O₈ contents. A Cu₃Nb₂O₈−Zn₃Nb₂O₈ solid solution exists from 0 < x < 0.5 while a mixture of Cu₃Nb₂O₈ and Zn₃Nb₂O₈ exists from 0.5 < x < 1. The microwave dielectric properties correlated to the crystal structure. In Cu₃Nb₂O₈−Zn₃Nb₂O₈ solid solution region, the variation of dielectric properties could be explained by the structure distortion of Cu₃Nb₂O₈ due to electronic anisotropies of Cu²⁺ cations.