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-CuV ₂O₆, whereas the material heat treated at 400 °C was an oxygen deficient counterpart of α-CuV₂O₅, which was CuV₂O_5.88 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 CuV₂O_5.88. The symmetrical degree of the [VO₆] octahedron in α-CuV₂O₆ is higher than that of orthorhombic V₂O₅ and oxygen deficiency CuV ₂O_5.88. 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 CuV₂O_5.88.