Structure of SiO2–MgO–Na2O glasses by FTIR, Raman and 29Si MAS NMR

The study of SiO2–MgO–Na2O glasses is of particular relevance because some compositions can exhibit adequate properties for their use in biomedical applications.The influence of substitution of divalent Mg2+ ions for monovalent Na+ in the structure of silicate glasses which contain 55 mol% SiO2 was investigated by Magic-Angle Spinning (MAS) Nuclear Magnetic Resonance (NMR), Raman spectroscopy and Fourier Transformed Infrared Spectroscopy (FTIR), in both qualitative and quantitative basis. According to the results, the structure of the glasses predominantly comprised Q2 and Q3 structural species. In glasses with more than 25% molar MgO, the substitution of Na2O by MgO promotes a significant change in the main silicate chain through a disproportionation reaction 2Q2⇆Q1+Q3, while glasses with less than 20% molar MgO show no evidence of silicate chain modifications.Information about the glass structure is of major importance for the understanding of the parameters that can control the biomedical properties, such as the chemical dissolution rate, pH and cell viability.