The Structure, Vibrational Spectra, and Thermal Expansion Study of AVO₄ (A=Bi, Fe, Cr) and Co₂V₂O₇

Vanadate is an important functional material. It has been widely studied and applied in luminescence and photocatalysis. Vanadium compounds have been synthesized to investigate the thermal expansion properties and structure. Both BiVO₄ and Co₂V₂O₇ are monoclinic at room temperature, FeVO₄'s crystal structure is triclinic, and CrVO₄ is orthorhombic. The relatively linear, thermal-expansion, and temperature-dependent Raman spectroscopy results showed that the phase transition of BiVO₄ occurred at 200 to 300 °C. The coefficient of thermal expansion (CTE) of Co₂V₂O₇ was larger than that of the monoclinic structure BiVO₄. The CTE of the tetragonal structure of BiVO₄ was 15.27 × 10^-6 °C^-1 which was the largest CTE in our measurement results, and the CTE of anorthic structure FeVO₄ was 2.84 × 10^-6 °C^-1 and was the smallest.