Studies on thermionic emission and structure transformations in W and Mo alloys with group 4sup(a) transition metal carbides in the process of long-term testing

Studied is thermionic emission of cathodes of the 4sup(a) group carbide (TiC, ZrC, HfC) alloys with tungsten and molybdenum. The investigations are carried out in vacuum not worse than 1x10-7 toor at the temperature of 2.300 K. The measurement of the work function with carbide concentration has shown that in the range of 20-80 wt.% the effective work function is 0.1-0.4 eV lower in carbide-metal alloys than in pure carbides. The stability of emission was studied in experimental diodes during 1.000 h at the temperature of 2.300 K. It is shown that under operating conditions structure of the emitting surface formed differs from that of the emitter body. The experimental results confirm a film mechanism of cathode operation