Recent Studies of the Chemical and Physical Processes in Thermionic Cathodes

The reason for the reduced effective work function of osmium coated dispenser cathodes has been investigated using emission microscopy, scanning electron microscopy, electron microprobe analysis and X-ray photo electron spectroscopy. The results indicate that the presence of osmium increases the thickness of the emitting layer and that this layer contains osmium which is chemically combined with the barium to form oxy-anion compounds. On partially coated cathodes an area of enhanced emission was observed at the tungsten/osmium interface.