Spectral and Total Emissivity of the Reaction Bonded Silicon Nitride

Spectral (in the wavelength range of 1 – 25 μm) and total emissivity of reaction bonded silicon nitride were determined together with their temperature dependence in the range between room temperature and 1573 K. The influence of ytterbium oxide and nickel impurities on the optical properties of the material was investigated. Emissivity was determined from the total reflectance spectra at room temperature, the diffuse reflectance spectra at temperatures up to 1173 K, and by monochromatic radiation pyrometry, and measurement results were compared.