Determination of diffusion coefficient of titanium ion in TiO 2SiO 2 wet gel prepared from metal alkoxides during leaching

Abstract

It was found that the radial gradient refractive index ( r-GRIN) glass rod could be produced by the leaching of wet gel prepared by a sol-gel method from metal alkoxides and heat-treatment of the gel. The concentration gradient of the doped component resulting from its diffusion in the wet gel was studied. In order to estimate the exact diffusion coefficient of the titanium ion in the binary TiO 2SiO 2 wet gel, its value was measured by using two methods. The observed diffusion coefficient by colorimetric analysis was about 1.1 × 10 −6 cm 2/s, while the value obtained from analysis of EPMA was about 1.2 × 10 −6 cm 2/s, and both values were nearly equal to each other. The activation energy of titanium ion diffusion in the wet gel was estimated to be about 11 kcal/mol.