Textural and structural studies of sol–gel derived CaO- and MgO silica glasses

We report on a comparison of the textural and structural properties between the binary glasses xCaO · (1 − x)SiO2 and the xMgO · (1 − x)SiO2 (x = 0, 0.1, 0.2, 0.3) prepared by the sol–gel method. The textural properties (specific surface area and pore size distribution) obtained by N2-adsorption exhibit systematic changes with the alkaline earth oxide content exhibiting parallel behavior for CaO- and MgO-modified glasses. The specific surface area was found to decrease while pore volume increased when increasing the alkaline earth oxide content. Raman spectroscopy has been used to elucidate details of the local structure of these gel derived glasses. The findings have been correlated with the results obtained from the corresponding conventionally prepared melt-quenched glasses. The population of the Q3 species was found to increase for both CaO- and MgO-modified silica, with the increase of the former being more pronounced than the latter. The more ‘defective’ nature of the sol–gel glasses, in comparison with the melt-quenched ones, seems to be the factor for the alkaline earth cation ability to promote the reactions related to the bioactivity.