Microwave dielectric properties of Ba(Mg1/2W1/2)O-3-BaTiO3 ceramics

Ceramics with the chemical formula xBa(Mg1/2W1/2)O-3-(1-x)BaTiO3 (x = 0.40-1.0) are prepared for use as dielectric resonators. The specimens were investigated by X-ray diffraction analysis, scanning electron microscopy and transmission electron microscopy. As x decreased from 1.0 to 0.40, the temperature coefficient of resonant frequency increased gradually from -33 to +303.5 ppm/degrees C. At x = 2/3, the Q x f value increased markedly. The crystal structure with a Mg-W ordered B-site sublattice changed to a crystal structure with a Mg-W-Ti ordered B-site sublattice at x = 0.84-0.72. Ba(Mg1/3W1/3Ti1/3)O-3 is formed at x similar to 2/3, and has excellent dielectric properties (epsilon(r) = 14.5, Q x f = 107000 (GHz), tau(f) = -7.6 ppm/degrees C). The B-site cation of Ti improved the stability of the temperature coefficient of resonant frequency (TCF) for Ba(Mg1/2W1/2)O-3 (tau(f) = -33 ppm/degrees C).