Improvement to a bench top instrument for measuring spectral emittance at high temperatures

Advanced ceramic materials are widely being developed and studied for application as thermal barrier coatings in the next generation of gas turbine engines. Knowledge of the spectral radiative properties at high temperatures is important so as to ensure the desired effect as a thermal barrier and for accurate radiation thermometry measurements. A bench top instrument previously introduced in this journal has been utilized to determine the high temperature spectral emittance of these materials from measurements of hemispherical-directional reflection and hemispherical-directional transmission in the infrared range of 500–12 500 wave numbers (20–0.8 μm). However, a temperature limitation of the instrument’s flat, near-blackbody source of infrared radiance has been shown to result in spectral dependent measurement error that is unacceptable when the sample of interest is a few hundred degrees or more higher than the source. This article describes an improved flat near-blackbody source that allows operation t...