Selective and Continual Thermal Emission of Polycrystalline Yb₂O₃, Eu₂O₃, Ruby, and Sapphire

Abstract—Spectra of thermal emission in polycrystalline Yb₂O₃, Eu₂O₃, ruby, and sapphire at resonant laser, laser-thermal, and gas-kinetic excitation are experimentally studied. Spectra of oxides in the visible and near IR regions are superposition of selective and continual spectra. Intensity of selective spectra at transitions between thermally populated electron-vibrational states of the structure and impurity ions is determined by the relation between radiative and nonradiative relaxation. It is found out that continual emission is not related to the chemical composition and micro- and electron structure of the investigated materials, and the temperature dependence of the spectra under thermodynamic equilibrium is described by the Planck function. The results are important for understanding the nature of thermal emission of oxides and for thermometry of hypersonic aerodynamic and thermophotovoltaic materials under extreme conditions.