Temperature-stable crystal structure and microwave dielectric properties of BaSi2O5-Ba3V2O8 composite ceramics

(1-x)BaSi2O5-xBa3V2O8 (x = 0.05–0.25 in molar) novel low-dielectric ceramics were successfully synthesized and investigated via a solid-state sintering process. X-ray photoelectron spectroscopy proved that the valence of V element is V5+ without V4+ and Ba3V2O8 is a pure phase in the composite ceramics. The coexistence of BaSi2O5 and Ba3V2O8, without other phases, was demonstrated by X-ray diffraction and Raman spectroscopy. Furthermore, scanning electron microscopy combined with energy dispersive spectroscopy indicated the composition of grains and the distribution of the two phases. τf value close to zero was obtained in the composite ceramics with x = 0.2. Meanwhile, for 0.8BaSi2O5–0.2Ba3V2O8 ceramics after sintered at 1140 °C, the fantastic microwave dielectric properties were found: εr = 9.34, Q × f = 55,641 GHz, and near-zero τf of 0.14 ppm/°C, which make 0.8BaSi2O5–0.2Ba3V2O8 a pioneering candidate for 5G microwave applications.