Vanadium oxide (V2O5) and V2O5/Al2O3 mixed oxides have received much attention in recent years due to their optical properties, which make them interesting for various applications such as photocatalysis [Srinivas S.T. 1997, Deo G. 1994, and Kao C.K., 1994], gas sensors, as a window for solar cells, for electrochromic devices [Kumar A. 2008], color filters [Atuchin V.V. 2008], reflectance mirrors, smart windows, and surfaces with tunable emittance for temperature control of space vehicles [Ramana C.V. 1998, Park Y.J. 2002, and Wu Q. 2004] and in the synthesis of nanocomposites [Choi H. 1999].
In this study, The solid-state reaction method was used to prepare tablets of (V2O5)100-x (Al2O3)x with x=5, 10, 15, 20 wt.%. Thin films of thin films of Al2O3-doped V2O5 were deposited onto microscopic glass substrates using an electron-beam evaporation technique. The XRD measurements revealed that the as-deposited films and the annealed films at 300oC were amorphous in nature, meanwhile, after annealing at 500oC some diffraction peaks, Two vanadium oxidation peaks, were found in the amorphous matrix. This behaviour could play an important role as a cathode in fabrication of TFBs.
The optical properties of films were measured in the UV–Vis–NIR wavelength range using a double-beam spectrophotometer. For as-deposited films it was found that with increase in the Al2O3 ratio, the transmittance slightly decreased, meanwhile the reflectance and refractive index increased. The decrease in optical transmittance has been attributed to the oxygen deficiency. This oxygen deficiency makes the compositions very suitable for use as an oxygen sensor.
For annealed films, it was observed that the average transmittance in the visible region gradually decreased with annealing temperature. In the near-infrared region it was found that the average transmittance decreased for all films up to 400oC, then exhibited a slight increase above 400oC. It was also established that the refractive index is related to the packing density of the film. The optical bandgap was found to vary from 1.82 to 2.83 eV and it decreased with annealing temperature for all films with different ratios of Al2O3