Phase compositions and microwave dielectric characteristics of xMg2B2O5-(1-x)Ba3V2O8 (0.5 ≤x ≤ 0.7) ceramics

Herein, xMg ₂B ₂O ₅-(1-x)Ba ₃V ₂O ₈ (0.5 ≤x ≤ 0.7) microwave dielectric composite ceramics were prepared via the solid-state reaction method at a relatively low sintering temperature (around 940–1020 °C). The phase compositions, microstructure, and elemental compositions of the ceramics were characterized by X-ray diffraction (XRD), and scanning electron microscopy (SEM) combined with energy-dispersive spectroscopy (EDS), respectively. According to the results, both Mg ₂B ₂O ₅ and Ba ₃V ₂O ₈ phases coexisted after sintering in the temperature range of 940–1020 °C. The growth of Ba ₃V ₂O ₈ grains was inhibited by the increase in amount of Mg ₂B ₂O ₅ inclusions. Moreover, mixing these two phases in a proper ratio did not only reduce the sintering temperature, but also improved the temperature coefficient of resonant frequency (τ _f ) and Q×f value (Q is quality factor=1/ dielectric loss, f=resonant frequency) of the xMg ₂B ₂O ₅-(1-x)Ba ₃V ₂O ₈ microwave dielectric ceramics. In particular, the optimal microwave dielectric properties (ε _r = 10.1, Q×f = 48,050 GHz, τ _f = −3 ppm/°C) were reached after 2 h of sintering at 960 °C for the ceramic with x = 0.7.