Method of making a ruggedized high current density cathode

Claim 1

Method of making a high current density cathode capable of operating at current densities of 2A/cm 2 to 30A/cm 2 in the temperature range of 900 degrees C. to 1125 degrees C., said method including the steps of A. machining a porous high purity pellet containing copper in its pores and also containing about 0.6 to 2 weight percent of an activator to the desired cathode shape without reducing the pores of the emitter pellet, wherein said pellet is selected from the group consisting of a tungsten pellet, a tungsten iridium pellet, a tungsten rhenium pellet and a tungsten osmium pellet, and wherein the activator is selected from the group consisting of hafnium and zirconium, B. firing the pellet at 1800 degrees C. in a non-oxidizing atmosphere selected from the group consisting of an inert gas and dry hydrogen to remove the copper filler material, C. impregnating the pellet with Ba 5 Sr(WO 6 ) 2 at about 1900 degrees C. in a dry inert gas atmosphere, wherein said Ba 5 Sr(WO 6 ) 2 impregnant is made by mixing stoichiometric amounts of barium carbonate, strontium carbonate, and tungsten trioxide according to the equation 5BaCO 3 +SrCO 3 +2WO 3 →Ba 5 Sr(WO 6 ) 2 +6CO 2 , ball milling the mixture overnight, and then firing in an air oven at 1475 degrees C. for 2 hours, and D. firing the impregnated emitter in a dry hydrogen atmosphere at about 1840 degrees C. for about 2.5 to 5 minutes.