Solid state [formula omitted] NMR and FT Raman spectroscopy of the devitrification of lithium metasilicate glass

Abstract

Lithium metasilicate glass was found to devitrify in two steps. In the primary step the glass undergoes a transformation which is exothermic and in which there is almost no crystal growth. The nature of this process and the modification that it causes in the glass has been investigated by a combination of solid state 29 Si nuclear magnetic resonance spectroscopy and Raman spectroscopy. During the primary step a redistribution of Q N units occurs as shown by changes in the intensities of the 29 Si resonances associated with these structural units. The absence of narrow resonances in samples heated to the primary step suggests that most of the sample is not crystalline. This amorphous state is consistent with the powder X-ray diffraction where only diffraction peaks with small intensities are seen.