The temperature variation of the total hemispherical emissivity εh of an electropolished surface of 3N8 pure tungsten has been investigated with a transient calorimetric technique in the temperature range 180–1000 K. The experimental data are believed to be the first ever obtained on tungsten below 273 K and also the first ever obtained on electropolished tungsten above 273 K. It is found that the data depart in a significant manner at all temperatures investigated from the theory that assumes a zero relaxation time τ for conduction electrons. In the range 180–300 K, εh behaves as though τ is finite and nearly independent of the frequency. At higher temperatures, εh behaves in a manner that indicates qualitatively that τ is frequency dependent. Beginning at 600 K, the slope of the εh-vs-T graph increases steadily up to 1000 K. This increase is belived to be due to the onset of interband excitations.
© 1978 Optical Society of America
D. P. Verret and K. G. Ramanathan, "Total hemispherical emissivity of tungsten," J. Opt. Soc. Am. 68, 1167-1172 (1978)