The high-temperature electron emission and vaporization of tungsten-osmium alloys

Abstract

Effective work functions from the polycrystalline surfaces of three arc-melted binary tungsten-osmium alloys of varying composition and one sintered tungsten-osmium alloy were examined. Alloy content varied from 4.76 to 13.05 wt pct osmium. Emphasis was placed on obtaining data over a wide temperature range and maintaining as high a vacuum as possible. Work functions were obtained by the thermionic method with high-temperature electron emission measured by a guard-ringed vacuum emission vehicle (VEV) designed to use a Schottky technique. The surface osmium activity was analyzed by employing a high-temperature quad-rupole mass spectrometer designed to detect subliming vapors from a freely vaporizing solid material. The work function of the sintered W-5 pct Os and arc-melted W-5 pct Os did not vary with an increase in temperature. Likewise, the arc-melted W-9 pct Os and W-13 pct Os both exhibited a constant work function. The highest observed work function (4.92 eV) was obtained at temperatures of 2100 and 2200 K from the W-13 pct Os sample. The W-13 pct Os sample yielded high work functions (4.85 to 4.92 eV) over the entire temperature range studied(i.e.), 1700 to 2800 K).