Synthesis and structural properties of stoichiometric and oxygen deficient CuV2O6 prepared via co-precipitation method

Copper vanadates were synthesized using co-precipitation method. Scanning electron microscopy showed that the crystallinity of the materials increased with heat treatment temperature. X-ray diffraction study showed the material heat treated at 600 °C was stoichiometric triclinic α-CuV2O6, whereas the material heat treated at 400 °C was an oxygen deficient counterpart of α-CuV2O6, which was CuV2O5.88 obtained from the thermogravimetric data. X-ray absorption near edge spectroscopy confirmed a valence state of + 5 for V in α-CuV2O6, whereas a valence state lower than + 5 in CuV2O5.88. The symmetrical degree of the [VO6] octahedron in α-CuV2O6 is higher than that of orthorhombic V2O5 and oxygen deficiency CuV2O5.88. The Raman band of the V–O1 stretching vibration showed a red shift for copper vanadates with respect to orthorhombic V2O5 because of the electrostatic attraction between Cu and O1 atoms. Moreover, the V4+–O1 stretching vibration was observed for oxygen deficient CuV2O5.88.