Preparation, microstructure and microwave dielectric properties of Zr_xTi_1-xO₄ (x=0.40-0.60) ceramics

Zr_xTi_1-xO₄ (x = 0.40-0.60) ceramics sintered without additives were prepared from powders made by the coprecipitation of metal salts from aqueous solutions in order to investigate the existence range of a homogeneous phase and the relationships between composition, microstructure and the dielectric properties. XRD, TEM, SEM, EDS, and the dielectric measurements were used to characterize the products. A homogeneous solid solution was obtained. Its crystal structure was isomorphous with ZrTiO₄. The variation of the lattice parameters with TiO₂ content was discussed. The optimum sintering temperature of samples was dependent of composition. TiO₂ suppressed the densification and acted as a grain growth enhancer during the sintering process. With the increase in TiO₂ content the relative densities of the sintered bodies decrease, while the grain sizes increase. The dielectric properties at microwave frequency (1.8 GHz) in this system, especially Q value, were poor, due to low densification, impurities and lattice defects. The dielectric constant ε_r and Q value exhibited a significant dependence on the relative density and composition. Both ε_r and Q increased with the increase in relative density, but they were primarily influenced by the composition and the effect of the relative density could be ignored when the relative density was greater than 90% theoretical. ε_r increased slightly with increasing TiO₂ content, while Q value decreased.