Synthesis of various stoichiometry nano-powder of VO2

The violet polycrystalline (NH4)(5) [(VO)(6)(CO3)(4)(OH)(9)] . 10H(2)O( I) was synthesized by using V2O5, HCl, N2H4 . 2HCl and NH4HCO3 as the starting materials. The yield was 80%similar to95%. The TG/DTG and DTA of I were studied in a flow of N-2. The effects of partial pressure of oxygen(p(O2)) in N-2-air flow and temperature of reaction on VO2 Stoichiometry were investigated in the pyrolysis of I in a silica tube. The results show that x value of VOx is proportional to p(O2) at pyrolysis temperature of 500degreesC. At p(O2) = 30.3 Pa and in the temperature range from 450 to 520degreesC the products are oxygen-deficient VO2 , and when the temperature is lower than 450degreesC or higher than 520degreesC, the products are oxygen-rich VO2. In this paper, various stoichiometry VO, powders from VO1.927 to VO2.080 were successfully synthesized by pyrolysizing the precursor. XRD patterns of VO2 show that none of the impurity peaks was observed. The SEM micrograph of sample indicates that as-prepared VO2 is spherical particles with mean size 20 nm and is homogeneous in distribution. Further experiments testify that the composition of nano-powders is homogeneous.