SOL-GEL SYNTHESIS OF SIO2-P2O5 GLASSES

Citation
C. Fernandezlorenzo et al., SOL-GEL SYNTHESIS OF SIO2-P2O5 GLASSES, Journal of non-crystalline solids, 176(2-3), 1994, pp. 189-199
Citations number
26
Categorie Soggetti
Material Science, Ceramics
ISSN journal
00223093
Volume
176
Issue
2-3
Year of publication
1994
Pages
189 - 199
Database
ISI
SICI code
0022-3093(1994)176:2-3<189:SSOSG>2.0.ZU;2-U
Abstract
The synthesis of P2O5-SiO2 glasses from solutions has been studied thr ough gelation kinetics, Raman and nuclear magnetic resonance (NMR) spe ctroscopies. Different preparation methods are compared. The effect of the phosphorus precursor has been investigated. Phosphoric acid ester s are not hydrolyzed and they do not yield condensation with silica. R eaction of anhydrous H3PO4 with Si-OR groups leads to the formation of Si-O-P bonds which are easily hydrolyzed. Only a few remain after add ition of water and gelation. Therefore, P-Si homogeneity is difficult to achieve after gelation and the following drying and heat-treatment procedures. This absence of homogeneity is observed by solid-state mag ic angle spinning (MAS)-NMR and X-ray diffraction studies performed on gel samples heated at 300, 500 and 800 degrees C in the case of xerog els and 500, 950 and 1140 degrees C for aerogels.