An in-situ real-time study on solid phase formation and its degree of structural disorder could shed light on the mechanisms of solidification from the liquid and allow insight into the creation of materials designed to possess enhanced properties and facilitate their production and application. The implementation of a Rapid Scan technique on a FT-IR emissometer designed to allow the observation of materials under extreme temperature conditions allows following the liquid to solid-state phase transition mechanisms through time-resolved emissivity spectra acquired at a speed of 20 spectra per second. The cooling rate of the material can be modified by controlling the laser-heating system. This technique has been validated on SrAl2Si2O8 feldspar, a material which displays structural disorder. The technique is sufficiently accurate to determine small changes in the linewidths of spectra obtained at different cooling rates, suggesting that structural order is increased at slower cooling speeds and confirming the Al/Si ordering dependence on thermal history.

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 α→β 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.

A new methodology allowing real time observation of materials during their cooling, from the molten state to low temperature has been developed. This possibility originates from the implementation of a Rapid Scan feature on a FT-IR emissometer designed to probe materials submitted to extreme temperature conditions. Original time-resolved emissivity dependence during the phase transition are reported for the first time. The resulting out of equilibrium, dynamic, new data have been compared to the equilibrium, static, classical measurements to demonstrate the reliability of the new technique on two reference samples (Al2O3 and SiO2). The proposed method has high possibilities to be applied to different materials to enable the observation of fast structural transformations during liquid to solid phase change through the evolution of the dielectric function.