IR And Electrical Properties Of Tungsten-Doped Vanadium Dioxide Nanopowders Prepared By Thermolysis

Thermochromic vanadium dioxide VO₂ exhibits a semi-conducting to metallic phase transition at 68℃, involving strong variations in electrical, magnetic, optical transmittance in the IR region, especially its potential application background.As a special function material, vanadium dioxide (VO₂) have attracted great interest and been extensively studied.This paper reports that tungsten-doped vanadium dioxide nanopowders were synthesized by Deposition-Thermolysis method with active white powdery tungstic acid (WPTA) used as a substitutional dopant. It was found that this method was a valuable preparation technique for its cheap precursor, simple processes, can be doped tungsten easily, and great potential to produce markedly high quality nanopowders.The characterization and analysis of terminal resultant were determined by XRD, XPS, TEM, TG-DTA and DSC.The properties of thermochromic VO₂ nanopowders have been investigated by FT-IR and the four-probe method.The results show that VO₂ particle size is about 10～15nm.And we found that powders with dopant levels higher than 8.02% is not VO₂ anymore.The phase transition temperature of the doped VO₂ powders is decreased to25.6℃, even to 3.4℃, which is very close to the room temperature. The results indicated that WPTA was found to be exceptionally effective as a dopant for reducing transition temperature. The contrast of its transmission measured at 20℃and 30℃by FTIR below and above the phase-transition temperature is 92%. Such a low Tc is beneficial to the application and development of smart windows materials.