Structure and Physical Properties of TiO2-V2O5 Gel Coatings

Abstract

ABSTRACTSemiconducting V2O5 gels containing up to 30 mol% of TiO2 were prepared through simultaneous hydrolysis of alkoxides in ethanol solution. Coatings of these gels about 5 nm to 20 μm,in thickness were made by dip coating. The coatings were yellowish green and transparent. The fiber-like structure of the gels was observed by TEM. The gels were about 10 nm or less in diameter, and the diameter decreased with increasing TiO2 content. The refractive indices, n, and the thickness, d, of the coatings were determined by ellipsometry. d was approximately proportional to the square root of the pulling rate. When d was less than 10 nm, the refractive indices parallel to the pulling direction were lower than those perpendicular to the pulling direction. The dc conductivity parallel to the surface of the coatings, σ//, of V2O5 gel coating was higher than that of crystalline V2O5. The dc conductivity perpendicular to the surface of the coatings, σ/, was about 3 to 4 orders of magnitude lower than σ//. With increasing Tio2 content, both σ// and σ/ decreased.