Chemical and sonochemical approaches to the formation of VO{sub 2} films and VO{sub 2}-impregnated materials

A new chemical and chemical/ultrasonic approach to the preparation of VO{sub 2} films and VO{sub 2}-impregnated bulk materials has been developed. In this approach, a V{sub 2}O{sub 5} sol prepared by quenching is used to coat SiO{sub 2} substrates. The resulting gel-film is heat treated in a reducing atmosphere to form a film identified as VO{sub 2} from the results of X-ray diffraction and both optical and resistivity measurements, which reveal the phase transition characteristic of vanadium dioxide. The advantage of this approach to the formation of VO{sub 2} is that the V{sub 2}O{sub 5} sol can be used to impregnate porous materials, which are then heated treated to form an optically active composite material. The switching properties of the VO{sub 2} films are investigated using optical and resistivity measurements, and the results are compared to those obtained for VO{sub 2}-films prepared by more-conventional methods