Using an optical pyrometer method, the thermal conductivity of tungsten has been found to vary linearly from 1.170 watts/(cm2. K°/cm) at 1100°K to 1.026 watts/(cm2. K°/cm) at 2000°K. Similarly, the thermal conductivity of molybdenum has been found to vary linearly from 1.083 watts/(cm2. K°/cm) at 1200°K to 0.666 watt/(cm2. K°/cm) at 1900°K. Spectrographic analysis indicated only traces of impurities in samples of the two metals used in the investigation.
ROBERT H. OSBORN, "Thermal Conductivities of Tungsten and Molybdenum at Incandescent Temperatures," J. Opt. Soc. Am. 31, 428-432 (1941)