A spectroscopic method to measure the spectral emissivity of semi-transparent materials up to high temperature

A spectroscopic method to measure directional spectral emissivity for homogeneous and heterogeneous semi-transparent materials, giving access to a large spectral 10–12 000 cm−1 range and to temperatures lying between 600 and 3000 K is reported. Sample heating is supplied by a carbon dioxide laser and the blackbody flux reference is obtained with a lanthanum chromite furnace. Experimental results obtained with this setup on several dielectric oxides such as silica, alumina, and magnesia are in good agreement with the results obtained by an indirect method based on the Kirchhoff’s laws. A brief overview of the setup abilities and a detailed discussion of the emissivity spectra are also proposed.