Melting points, spectral reflectivity, and emissivity of semitransparent ceramic materials

A new method based on multiwavelength optical probing and multiwavelength pyroreflectometry of open sample surface to measure spectral optical properties of semitransparent ceramic materials at their melting points and to determine their true melting temperatures has been developed. With the method developed the spectral optical properties (reflectivity, emissivity, transmittance) of Nd sub(2)O sub(3), Gd sub(2)O sub(3), Er sub(2)O sub(3), and Ho sub(2)O sub(3) for seven wavelengths in the spectral range 0.4 to 1.1 mu m at their melting points have been measured for the first time. It is shown that the method developed has a high precision in determining the true melting temperatures for semitransparent ceramic materials. In open surface pyrometry this method is used for the first time.