Hydroxyl sites in SiO2 glass: a note on infrared and Raman spectra

Abstract

There is some interest in the speciation of water in silicate glasses and melts, and the effect of bulk composition on this speciation. We have obtained infrared and Raman spectra for Si02-H20 glasses with low (1200 ppm) and high (6.3 wt%) water contents. The lowwater-content glass shows an asymmetric band in the fundamental O-H stretching region, consistent with an SiOH species involved in a range of hydrogen-bonding environments. The high-water-content sample shows features due to both hydroxyl groups, as observed for the low-water-content glass, and molecular H20 dissolved in the glass. This sample also shows a Raman band at 3598 cm-i, which probably corresponds to a new type of SiOH species. We have also obtained the Raman spectrum for a sodium silicate glass Na20' 4Si02 containing 1 wt% H20. Addition of water to this composition causes considerable changes in the silicate band region below 1200 em-i. The O-H stretching bands are very different to those observed for the Si02-H20 glasses, and a weak band near 2350 cm-1 may correspond to SiOH groups involved in intratetrahedral hydrogen bonding, across an edge of the Si04 tetrahedron.