Improved high-Q microwave dielectric material using B₂O₃-doped MgNb₂O₆ ceramics

In this paper, the microstructures and microwave dielectric properties of MgNb₂O₆ ceramics doped with B₂O₃ are investigated. The formation of an impurity phase is not detected by X-ray diffraction pattern and the grain growth is apparent with increasing the sintering temperature from scanning electron microscopy results. With adding the sintering aid B₂O₃, not only decreasing the sintering temperature but also enhancing the quality factor (Q) value are obtained. The maximum Q × f value obtained in this study is 115,800(GHz) with 0.25 wt.% B₂O₃ added sintered at 1260 °C that possesses a dielectric constant (ε_r) of 21.5 and the temperature coefficients of resonant frequency (τ_f) of -48 ppm/°C. The correlation between dielectric properties and the microstructures with different doped amounts of B₂O₃ is also discussed.