Abstract
This paper describes experimental investigation of the thermionic emission properties of the transition metal carbides (TiC, ZrC, HfC, TaC, NbC) coated on tatalum wires. The carbide coating was carried out by rf reactive sputtering or direct carburization. It was found that these coated emitters were suitable for hot cathode used in vacuum measurements. The emission characteristics of these emitters during and after interaction with several gases was compared with that of tungsten emitter, especially for TaC, the variation of emissivities was investigated in relation whit the change of surface chemical composition analyzed by Auger spectroscopy.
