Influence of Reaction Conditions on Sol-Gel Process Producing SiO₂ and SiO_2-P₂O₅ Gel and Glass

Abstract

The effect of H 2 O and the slow thermal annealing on the properties of pure silica (SiO 2 ) and phosphosilicate (SiO 2 -P 2 O 5 ) gel-glasses are presented. The monolithic samples have been prepared via sol-gel process using tetraethorthosilicate (TEOS), Si(C 2 H 5 O) 4 and Triethylphosphate (TEP) (C 2 H 5 O) 3 P(O) as SiO 2 and P 2 O 5 precursors. Phosphate incorporates into the silicate network by substituting Si atoms and consequently, we observed changes in structural and spectroscopic properties for these systems. The structures of prepared samples were examined by observed weight loss, XRD and FTIR. It has been found that in the structure of pure silica and phosphosilicate glasses there are formed domains characterized by certain degree of ordering of the units present in their composition, while the structure of pure silica is still amorphous of these glasses. The changing character of domains structure may be the reason of different chemical activities of phosphosilicate glass.