SPECTROSCOPIC INVESTIGATION OF GLASS TRANSITIONS, STRUCTURE, AND CATION VIBRATIONS IN INORGANIC OXIDE GLASSES

Author Institution: Department of Chemistry, Brown UniversityFar infrared ($10-800 cm^{-1}$) spectra of metal-polymetaphosphate glasses having the compositions $M_{2}O \cdot P_{2}O_{5}$ or $MO\cdot P_{2}O_{5}$ reveal broad, low frequency cation-motion bands, whose frequencies and half-bandwidths vary inversely with cation mass. The bands shift to lower frequencies as the $M_{2}O$ or MO mole-fraction of a given glass is decreased. Force field elements for the alkali cation-network vibrations, calculated assuming the cation local environment to be an $O_{h}$ oxygen field, vary linearly with the glass transition temperature of the stoichiometric glasses. Comparison between the spectra for the glassy and crystalline forms of alkali metaphosphates indicates that the observed cation-dependent bands in the glass spectra results from strong damping of analogous crystalline modes. Interionic vibrations are also observed for metaborate and metagermanate glasses and for mixed alkali glasses. The Raman spectra of drawn glass fibers from the phosphate, borate, and germanate glass forming systems yield information relating to the glass molecular structure, through measurement of the fiber-orientation angular dependence of the polarization of the Raman bands. High temperature Raman spectroscopy is employed to follow glass to crystal phase transitions in alkali metaphosphate glasses