Microwave dielectric properties of forsterite-based solid solutions

Recently forsterite has been reported as an excellent dielectric material for millimeter wave application. However, its temperature variation of the resonant frequency (τf) is relatively large which precludes its immediate use in practical applications. In this paper, we report the effect of substituting Ca and Mn for Mg on the microwave dielectric properties of forsterite. The composition 0.975Mg2SiO4–0.025Mn2SiO4 showed excellent Q × f value of 180,000 GHz with a τf of −71 ppm/°C. The end member Mn2SiO4, showed a Q × f of 50,000GHz, ɛr of 8.52 and τf = −90 ppm/°C. In the case of Ca substitution for Mg, τf shifted to high negative value with increasing amount of Ca. However, Q × f did not show much change in its value. It is suggested that the increase of τf towards a more negative value is related to the ionic radii of the substitutes.