Crystal phase, microstructure and microwave properties of Ba 2 V x O 7 (1.85 ≤ x ≤ 2.05) ceramics

Crystal phase, microstructure and microwave properties of Ba2VxO7 (1.85 ≤ x ≤ 2.05) ceramics were researched. XRD results revealed that the single-phase Ba2V2O7 was formed when x ≥ 2, while the second-phase Ba3V2O8 was observed with 1.85 ≤ x < 2. Rietveld refinement demonstrated that the amount of Ba3V2O8 increased with the decline of vanadium content. Further, HRTEM observation verified that the co-existence of Ba3V2O8 and Ba2V2O7 in the sample for x = 1.9. Meanwhile, SAED pattern confirmed the triclinic structure of Ba2V2O7. The τf value presented a tendency of shifting to zero with the augment of Ba3V2O8. FWHM of the highest peak 884 cm−1 in Raman spectra proved that an appropriately absent vanadium ions improved the quality factor. The satisfied microwave properties of er = 10.89, Q × f = 55,047 GHz (at 10 GHz), and τf = − 43.4 ppm/°C were achieved for Ba2V1.9O7 ceramic.