Semiconducting V2O5 gels with and without addition of GeO2 were prepared by hydrolysis of metal alkoxides in alcoholic solutions. Wet gels, xerogels dried at room temperature and supercritically dried aerogels, were characterized by transmission electron microscopy, X-ray diffraction and small-angle X-ray scattering. Crystalline vanadium oxides were not observed in xerogels, but V3O7 diffraction peaks were found for the aerogels kept at 250°C and 210 atm for 2 h or longer before drying. In the Porod region, in the range of scattering vector between about 10−2 and 10−1 Å−1, the power law was valid for wet and dry gels. Wet gels and aerogels are mass fractals. The fractal dimension of the wet gels increased from 2.1 to 3 during aging, but scarcely changed with supercritical drying. Xerogels are surface fractals with a surface fractal dimension of 2.1–2.5.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Ceramics and Composites
- Condensed Matter Physics
- Materials Chemistry