Rapid crystallization of refractory oxides and the possibility of formation of a two-phase zone

The results are given of numerical calculations of temperature fields under conditions of free cooling and rapid crystallization of a pool with molten alumina formed as a result of heating a sample by concentrated laser radiation, as well as of "effective" brightness temperatures corresponding to the radiation leaving the sample. Measurements are performed of the effective brightness temperatures and reflectivity for different wavelengths in the process of cooling molten alumina and zirconia formed as a result of heating ceramics by concentrated laser radiation. Comparison of the calculation and experimental results reveals the important part played by the extended two-phase zone formed in semitransparent oxides in the formation of temperature fields and related thermal-radiation properties.