THE HIGH-TEMPERATURE WORK FUNCTION BEHAVIOR OF POLYCRYSTALLINE OSMIUM

The thermionic emission behavior of randomly oriented polycrystalline osmium was investigated. Osmium exhibited a low thermionic work function of 4.68 eV at 1800 K which increased rapidly to 5.21 eV at 2600 K. The high temperatures and low pressures of these tests were designed to minimize any residual gas interactions with the sample surface. Still, the possibility that residual gases had some effect on the measured work function was not altogether ruled out. An allotropic phase transformation was considered as a possible explanation for the varying work function; however, X-ray diffraction experiments could not substantiate a new high-temperature phase.