Preparation of titania-silica glasses by the gel method

Abstract

A series of bulk glasses in the TiO₂-SiO₂ system have been prepared by hydrolysing the mixture solution of Ti(OC₃H₇)₄ and Si(OC₂H₅)₄ with water and hydrochloric acid, and slowly heating the resultant gels up to 800° C. The conversion of gels to glasses was examined by the measurements of Vickers' hardness, IR and TGA. The properties of TiO₂-SiO₂ glasses in the less than 12.9 wt% TiO₂ range obtained by the gel method were very similar to those of oxide glasses made by the flame hydrolysis process. These glasses showed ultra-low thermal expansion, but the precipitation of anatase remarkably increased the thermal expansion. In the less than 10.4 wt% TiO₂ range, the glasses obtained by heating up to 800° C were not crystallized at 1000° C or higher, while in the more than 20 wt% TiO₂ range anatase was precipitated at 900° C. It was found that glasses obtained by the gel method were a true solid solution at least up to 7.4 wt% TiO₂ composition.