Improved High-Q Microwave Dielectric Resonator Using WO3-doped Mg4Nb2O9 Ceramics

The microwave dielectric properties and microstructures of WO3-doped Mg4Nb2O9 ceramics prepared by the conventional solid-state route were investigated. The prepared ceramics exhibits a mixture of phases Mg4Nb2O9 and Mg5Nb4O15. It is found that low-level doping of WO3 (up to 1.5 wt%) can significantly improve the density and dielectric properties of Mg4Nb2O9 ceramics. At 1330 degrees C, 0.5 wt% WO3-doped Mg4Nb2O9 ceramics possess a dielectric constant (epsilon(r)) of 13.25, a apparent density of 4.22 g/cm(3) (96.3% TD), a Qxf value of 250,000 GHz, and a temperature coefficient of resonant frequency (tau(f)) of -62 ppm/degrees C. In contrast to pure Mg4Nb2O9 ceramics, incorporating additional WO3 helps to render a dielectric material with a similar to 30% dielectric loss reduction, a higher dielectric constant and retain a comparable tau(f), which makes it a very promising candidate for applications requiring low microwave dielectric loss. Moreover, a band-pass filter is also designed and simulated on the proposed dielectric to study its performance.