Structural evolution during Ag+/Na+ ion exchange in a sodium silicate glass

The structural evolution during Ag+/Na+ ion exchange in a sodium silicate glass has been investigated by micro infrared reflectance spectroscopy (IRRS) and Si-29 MAS-NMR spectroscopy. The IRRS spectrum varied depending on the AE concentration in the glass. The spectrum for the original glass had two distinct peaks corresponding to Si-Q-Si and Si-O- stretching vibrations in the wavelength region from 1500 to 700 cm(-1). The spectrum at a depth of 0.05 mm from the surface of ion-exchanged glass having Ag2O concentration of about 31 mol% had one peak and two shoulders, whereas the spectrum at a depth of 0.13 mm having Ag2O concentration of about 15 mol% had only one peak and the shoulders were not resolved. This change in the IRRS spectra was attributed, from Si-29 MAS-NMR spectroscopy, to the structural change induced by the Ag+/Na+ ion exchange to from Q(4) and Q(2) species at the expense of Q(3) species, which is responsible for the reduction in glass transition temperature.