Temperature-stable and high Q composite ceramics in low-temperature sinterable BaO–V2O5 binary system

• Ba2V2O7–Ba3(VO4)2 ceramics were explored in terms of structure and properties.
• The Q × f values were dominated by the packing fraction of each phase in the samples.
• The x = 0.42 sample attained good dielectric properties and chemical stability with Ag.

The low-temperature sinterable microwave dielectric composites with compositions of (1−x)Ba2V2O7–xBa3(VO4)2 (x = 0.27–0.52, in volume fraction) were prepared by cofiring mixtures of pure-phase Ba2V2O7 and Ba3(VO4)2. The phase structure and grain morphology of the ceramics were studied by X-ray diffraction and field emission scanning electron microscopy. The results indicated that the two phases of Ba2V2O7 and Ba3(VO4)2 can well coexist at sintering temperatures owing to different crystal structures. The microwave dielectric properties of this system were strongly related to densification, packing fraction, and the volume ratio of Ba2V2O7 and Ba3(VO4)2. The quality factor Q × f values and temperature coefficients of the resonant frequency (τf) of the ceramics can be significantly boosted by adjusting the relative content of the two phases. Consequently, a high Q × f value of 71,700 GHz, a near-zero τf of −1.4 ppm/°C and a low dielectric constant εr of 11.4 were obtained for the x = 0.42 sample sintered at a low temperature of 875 °C for 4 h, which are superior to those of several available low-loss dielectrics. In addition, no evidence of chemical reaction between the ceramics and Ag was observed during the cofiring process, suggesting that the as-prepared composite ceramics are suitable for low-permittivity low temperature co-fired ceramic applications.