Preparation of VO_2 Nanopowders and Their Properties

VO2 nanopowders with various stoichiometries and crystalline states were prepared by pyrolyzing the precursor, (NH4)5[(VO)6(CO3)4(OH)9]·10H2O, at low temperature in a mixed flow of air and N2. The adsorption properties of crystal, quasi-crystal and amorphous state nano-VO2-powders were studied. DSC results indicate that VO2.025 exhibits a phase transition at 70.1℃ and has the maximum phase transition heat in the range from VO1.985 to VO2.071. The unit-cell parameters of various stoichiometry VOx were determined. The results show that the unit-cell volume of the monoclinic VOx phase increases linearly from the oxygen-deficient VO2 to the oxygen-rich VO2.