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Infrared emissivity spectroscopy of a soda-lime silicate glass up to the melt

The short-range structure of an iron doped soda-lime glass was investigated by infrared emissivity spectroscopy from room temperature up to the melt. Quantitative information on the distribution of the Q^n tetrahedral units was obtained by fitting the emissivity spectra using a dielectric function model (DFM). The DFM is based on causal Gaussian bands, associated with the stretching motions of the silicate tetrahedra. The changes in the absorption modes are related to the activation of a dynamical disorder that continuously increases with temperature. The obtained Q^n speciation at room temperature is in good agreement with the magic-angle spinning nuclear magnetic resonance (MAS NMR) study. The distribution of the tetrahedral species undergoes slight changes with temperature, except during glass crystallization where Q^4 units increases, with a slight augmentation of Q^2 and Q^4 units in the melt. These results demonstrate the potentiality of infrared spectroscopy in the quantitative analysis of the polymerization degree of glasses and melts.