Raman Study on Sol-Gel Derived Tungsten Oxides from Tungsten Ethoxide

Abstract

Tungsten oxide gels were prepared by a sol-gel process from a tungsten ethoxide/ethanol/water solution (sol). Tungstic hydrates were observed in high-viscosity sol by Raman spectroscopy. As the sol is reduced to the gel, Raman bands ascribed to amorphous tungsten oxide appeared. The result of the Raman measurement shows that the structure of the gel changes progressively during heat treatment and that the amorphous tungsten oxide becomes a crystalline solid at 410°C.

Structural and gas-sensing properties of WO/sub 3/ nanocrystalline powders obtained by a sol-gel method from tungstic acid

“…For sol-gel WO , peak position is close to that usually found in the literature (807 cm ) and it approaches this value as annealing temperature increases. Similar behavior has already been reported for other sol-gel processes [12]. However, pyrolytic WO has its main peak shifted from the common position and it does not move to the common value as annealing temperature increases.…”

“…However, the peak at 947 cm , that is present in commercial tungstic acid, has not completely disappeared in dried gel. This peak is reported to correspond to the mode W O, which is also a bond of tungsten oxide hydrates (WO nH O) when a water molecule occupies one axial position [12], [17]. This confirms the XRD result about that some tungsten oxide hydrate was present.…”

“…Many methods have been applied to obtain thin films of this material such as sputtering [9], CVD [10], spray-pyrolysis [11], and spin coating or dip coating of sol-gel precursors [12].…”

Effect of SiO2 Doping on Growth Retardation of WO3 Nanoplate

“…Figure 1 shows IR spectra of dried precipitates obtained from the tungsten precursor with and without the addition of TEOS. Broad absorption band centered at around 710 cm -1 is assigned to a W-O stretching, 11) while broad absorption bands between 3,200 to 3,600 cm -1 are assigned to an O-H vibration of physically adsorbed water. Sharp absorption band at around 1,400 cm -1 is attributed to a stretching vibration of N-H bond in ammonia.…”

Raman spectra of sol-gel-derived tungsten oxides

“…The technology possesses the advantage that the amorphous films can be easily prepared from a colloidal solution (sol) by dip-coating or spraying [3]. There is the sol-gel method in which tungsten alkoxide is used as the raw material [5,6]. We have reported the Raman study of the gelation of the sol prepared by this method and the crystallization of the gel [6].…”