Improved sinterability and microwave dielectric properties of [Zn0.5Ti0.5]3+-doped ZnAl2O4 spinel solid solution

Low-permittivity ZnAl2-x(Zn0.5Ti0.5)(x)O-4 ceramics were synthesized via conventional solid-state reaction method. A pure ZnAl2O4 solid-state solution with an Fd-3m space group was achieved at x <= 0.1. Results showed that partial substitution of [Zn0.5Ti0.5](3+) for Al3+ effectively lowered the sintering temperature of the ZnAl2O4 ceramics and remarkably increased the quality factor (Q x f) values. Optimum microwave dielectric properties (epsilon(r) = 9.1, Q x f = 115,800 GHz and tau(f) = -78 ppm/degrees C) were obtained in the sample with x = 0.1 sintered at 1400 degrees C in oxygen atmosphere for 10 h. The temperature used for the sample was approximately 250 degrees C lower than the sintering temperature of conventional ZnAl2O4 ceramics.