Vol. 39, Issue 1, pp. 211-220 (2009)

Abstract

Knowledge of the physical parameters and optical constants of sols and sol–gel materials is important in view of their possible applications. In this work, silica and silica-titania sols were examined. Gelation time, surface tension, refractive index and optical transmittance were measured. The sol–gel materials were produced from the silica precursor Si(OC₂H₅)₄ mixed with the titanium dioxide precursor Ti(OC₂H₅)₄ and 96% ethyl alcohol. It was stated that the surface tension of pure silica sols is much higher than in case of silica-titania sols. The refractive index of fresh samples is lower than of stored sols. The transmittance is highest for the fresh samples  and it decreases with gelation time; however, this effect is stronger for silica-titania materials. By manipulating with the solvent content and titania addition, the required refractive index may be obtained.