Microwave dielectric properties of Ba-2(Mg1-2xY2xW1-xTix)O-6 ceramics

Phase formation, microstructure and microwave dielectric properties of Y2O3 and TiO2 doped BMW, i.e., Ba-2(Mg1-2xY2xW1-xTix)O-6, ceramics were investigated. Up to the composition of x = 0.5, the BMW ceramics having an ordered cubic structure were only observed and no secondary phase such as BaWO4 was detected. As the value of x increased, the lattice parameter increased linearly, implying that a substitutional solid solution occurred. A dense microstructure was observed. The grain shapes was certainly a polyhedron, indicating that the solid phase sintering occurred. As the x value increased, the dielectric constant (epsilon(r)) exhibited a tendency to increase slightly. The quality factor (Q x f(0)) sintered at 1700 degrees C increased up to x = 0.02 and then saturated. All of the compositions sintered at 1700 degrees C exhibited negative values of the temperature coefficient of resonant frequency (tau(f)). The absolute value of tau(f) decreased as the x value increased. Dielectric constant (epsilon(r)), quality factor (Q x f(0)) and temperature coefficient of resonant frequency (tau(f)) of the composition of x = 0.05, i.e., Ba-2(Mg0.40Y0.10W0.45Ti0.10)O-3, sintered at 1700 degrees C, were 19.6, 162,794 GHz, and -11.5 ppm/degrees C, respectively.