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°C, 0.5 wt% WO₃-doped Mg₄Nb₂O₉ ceramics possess a dielectric constant (εr) of 13.25, a apparent density of 4.22 g/cm³ (96.3% TD), a Q×f value of 250,000 GHz, and a temperature coefficient of resonant frequency (τ_f) of -62 ppm/°C. In contrast to pure Mg₄Nb₂O₉ ceramics, incorporating additional WO₃ helps to render a dielectric material with a ~30% dielectric loss reduction, a higher dielectric constant and retain a comparable τ_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.