Measuring spectral emissivity up to 4000 K

An inter-laboratory comparison involving three participants (PTB, CAE, TU Graz) was conducted on spectral emissivity measurements using experimental setups covering a temperature range from 1250 K to 4000 K and a spectral range between 0.6 μm and 20 μm. The main objective here was to carry out a European-level assessment of the coherency of spectral emissivity measurements at high temperatures. Three refractory materials (molybdenum, tungsten and isotropic graphite) were selected for this comparison. Samples were machined from the same batch of materials and then sandblasted and thermally annealed (PTB, CAE) to achieve uniform and stable surface properties and reduce potential scattering of results between participants. The spectral emissivity of the three materials was then measured by each of the three participants up to the maximum temperature attainable by the devices used. In the overlapping wavelength range from 600 nm to 1100 nm, all measurement methods were in good agreement with regards to their respective uncertainties.