Static and kinetic study of the structure and dynamics of vitreous silica at high temperatures by infrared emission spectroscopy

Emissivity spectra of amorphous silica have been acquired in a wide range of temperatures: from 4 K to more than 2500 K in static isothermal conditions, and from 2500 K to 600 K in kinetic free-cooling conditions. A fitting procedure allows extracting the temperature dependence of the dielectric function in the range of vibrational frequencies. Both sets of data are equivalent for a quantitative study of the structure of this model glass, despite the lower resolution and signal-to-noise ratio of the rapid-scan measurements. The results present clear changes at a special temperature near the alpha ->beta transition temperature for crystalline quartz. Similarly, simple relations between the intensities of the modes are found at the glass transition. This study provides insight into the structure and dynamics of vitreous silica at high temperature and proves that rapid-scan infrared emission spectroscopy is a viable analytical technique for the study of materials in non-equilibrium conditions.