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Vanadium oxide films and fibers have been fabricated by the acetylacetonate sol-gel method followed by annealing in wet nitrogen. The samples are characterized by X-ray diffraction and electrical conductivity measurements. The effects of a sol aging, the precursor decomposition and the gas atmosphere composition on the annealing process, structure and properties of the films are discussed. The two-stage temperature regime of annealing of amorphous films in wet nitrogen for formation of the well crystallized VO2 phase is chosen: 1) 25-550°C and 2) 550-600°C. The obtained films demonstrate the metal-insulator transition and electrical switching. Also, the effect of the polyvinylpyrrolidone additive concentration and electrospinning parameters on qualitative (absence of defects and gel drops) and quantitative (length and diameter) characteristics of vanadium oxide fibers is studied.

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-The sol-gel science and technology demonstrate an intense development over past few decades accompanied by important applications in electronics. The sol-gel technology represents a typical example of nanotechnology, since the gel products are actually nanocomposites or may contain nanoparticles. That is why the sol-gel science plays a crucial role in the R&D of contemporary nanotechnology for the fabrication of novel materials with new functional properties. In this paper we present an overview of our previous results on the properties of vanadium oxide gel structures, as well as report some recent findings in this area. Electrical and optical (including electrochromic effect) properties, influence of doping with tungsten and hydrogen, electrical switching. Moreover, the properties of vanadium oxide micro-and nanofibers are systematically described and discussed. Applied potentialities of the described phenomena for micro-and optoelectronics (electrochromic devices, sensors, electronic switches, etc) are also discussed.Index Terms -Transition metal oxides, sol-gel, vanadium oxide, metal-insulator transition, electrochromic effect. 1

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