OPTICAL-CENTERS OF CERIUM IN SILICA GLASSES OBTAINED BY THE SOL-GEL PROCESS

A spectral-luminescent study of Ce-containing silica gel-glasses doped at the sol stage and by impregnating porous xerogels with activator chloride salt solutions has been performed. The influence of the degree of doping and redox conditions of vitrification on the activator charge state and the content of hydroxyl ions and chlorine in the glass is considered. The preservation of the glass phase composition and the non-linear increase in the visible absorption intensity with increasing activator concentration from 5 X 10(17) to 3.0 X 10(20) ions/cm(3) are noted. It is concluded that there are two main types of optical centre. It is assumed that they represent Ce(III) oxygen complexes whose nearest surrounding includes quadruply charged (the first type) and triply charged (the second type) ions of cerium. Evidence has been obtained in favor of the superexchange excitation transfer to the cental ion of Ce(III) oxygen complexes from photoreduced to the triply charged state of the same ion name of Ce(IV) oxygen complexes.