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 tau(f) was obtained at near Zn/Ti = 1.15 composition. The epsilon(r) 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 . 1TiO(2) 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 degrees C, which induced microcracks and resulted in a decrease in Q factors. A range of dielectric resonators with epsilon(r) = 20-30, Q = 2,500-13,000 at 10 GHz, and tau(f) = -70 to +50 ppm/degrees C can be obtained in this system at a sintering temperature as low as 1100 degrees C. (C) 1998 Elsevier Science Ltd.