Mixture behavior and microwave dielectric properties of (1-x)CaWO4-xTiO(2)

The microwave dielectric characteristics and mixture behavior of (1-x)CaWO4-xTiO2 ceramics prepared with conventional solid-state route were studied using a network analyzer and X-ray power diffraction, respectively. The CaWO4 compound had good properties (low permittivity and high quality factor) for microwave applications, but it had a high negative temperature coefficient of resonant frequency (tau(f) = -53). Hence, in order to tune the dielectric properties, (1-x)CaWO4-xTiO2 were prepared for different values of x. X-ray powder diffraction and SEM analysis revealed that CaWO4 and TiO2 coexisted as a mixture. The mixture formation and dielectric properties could be explained by mixture rule. In particular, at x = 2.6, good microwave dielectric properties were obtained: Qf = 27,000, epsilon(r) = 17.48, and tau(f) = similar to 0 ppm/degrees C. (C) 2007 Published by Elsevier Ltd.