Microstructure and Microwave Dielectric Properties of Modified Zinc Titanates (II)

Zinc titanates ZnO–TiO2 (Zn/Ti = 0.67–2.0) and Zn1−xMgxTiO3 (x = 0–0.4) were prepared by a conventional mixed-oxide method, and the microstructure and dielectric properties in the microwave range were investigated. In the ZnO–TiO2 system, zinc orthotitanate, Zn2TiO4, had rutile solubility up to 0.33 mol followed by a decrease in the cubic lattice parameters as the amount of rutile increased. The zero τf was obtained at near Zn/Ti = 1.15 composition. The ϵr and Q∗f of the composition were 25 and 23,000, respectively. In the Zn1−xMgxTiO3 system, the composite structure with zinc orthotitanate and rutile of 1ZnO·1TiO2 transformed into the (Zn, Mg)TiO3 hexagonal solid solution at x = 0.3–0.4. However, phase decomposition occurred in this range at a temperature above 1160°C, which induced microcracks and resulted in a decrease in Q factors. A range of dielectric resonators with ϵr = 20–30, Q = 2,500–13,000 at 10 GHz, and τf = −70 to +50 ppm/°C can be obtained in this system at a sintering temperature as low as 1100°C.