Process for the manufacture of an impregnated cathode and a cathode obtained by this process

A process for preparing an impregnated cathode having an electron emissive surface, comprising:

• a. preparing an emissive pellet by copressing a mixture of a powder having the stoichiometric proportions of about 80 wt. % of at least one refractory element or alloy selected from the group consisting of tungsten, molybdenum, tantalum, and rhenium, about 2 wt. % of a powder of an electron-emission-improving element or alloy selected from the group consisting of osmium, ruthenium, iridium, scandium and scandium oxide, and about 15 wt. % of an electron emissive material including;
• 1. a powder of barium and calcium aluminates, or with
• 2. barium and calcium carbonate to which alumina has been added,
• the alumina content of the electron emissive material being about 3 wt. % of said mixture,
• b. sintering said pellet in a hydrogen atmosphere at a temperature of about 2000.degree. C., and c. attaching said emissive pellet to a support, said pellet having a top electron emissive surface which forms the emissive surface of said cathode.