IR and Raman spectroscopic studies of sol-gel derived alkaline-earth silicate glasses

IR and Raman spectroscopies have been utilized to study the structure and vibrational modes of sol-gel-derived binary silicate glasses. The present study is motivated by the immense geological significance and focuses on the MO-SiO (2) (M = Ca, Mg) binary systems in an effort to unveil the role of the CaO and MgO modifiers when incorporated to the 3D silica structure. Glasses in the composition range x =0, 0 center dot 1, 0 center dot 2, 0 center dot 3 and 0 center dot 4 prepared by the sol-gel method were compared with the corresponding glasses formed by appropriate mixing of SiO (2) and MO powders through melting and fast cooling. The vibrational spectra of the sol-gel-derived glasses have revealed considerable changes in relative intensities as a function of the MO mole fraction. These changes signify structural modifications on the silica network. The population of the Q (3) species was found to increase for both modified silicate systems. The rate of increase is more pronounced in the CaO-SiO (2) glasses. The extent of network depolymerization in the porous glass is higher at the same content of alkaline earth oxide compared to the bulk glass. The results are indicative of a more 'defective' nature of the sol-gel glasses compared to the corresponding melt-quenched ones.