Investigations on sol-gel process and structural characterization of SiO2-P2O5 powders

► The pH for silico-phosphate sol-gel powders if P2O5 10% is 4.5 for TEP precursor. ► The gelling time decreases from days to hours as temperature increases to 40-41 °C. ► Strong FTIR maxima appear at 1080 and 1300 cm− 1, assigned to SiOP bonds. ► Raman vibration at 280 cm− 1 is due to (SiO) vibration in silico-phosphate network. ► 31P MAS NMR − 46 ppm resonance specific to Q3 species is due only to POSiIV bonds.