Vacuum electron tube having an oxide cathode comprising chromium reducing agent
AssigneeRCA Licensing Corporation
InventorKenneth K. T. Chiang
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Abstract
In a vacuum electron tube, a novel oxide cathode comprising a metal substrate, means for heating said substrate to its operating temperature, and a layer of alkaline-earth-metal oxide on the substrate. The substrate is essentially free from silicon and contains operative concentrations greater than 1.0 weight % of chromium metal for progressively migrating into the oxide layer and reducing the oxide to yield alkaline-earth-metal.
Claims13
In a vacuum electron tube, an oxide cathode comprising a metal substrate a sleeve, means within said sleeve for heating said substrate to its operating temperature and a layer consisting essentially of alkaline-earth-metal oxide on said substrate,
- wherein said substrate is essentially free from silicon and contains operative concentrations greater than 1.0 weight percent of chromium metal for progressively reducing said oxide to yield alkaline earth metal.
In a vacuum electron tube, a thermionic cathode comprising
- (a) a metal substrate having a major external surface,
- (b) a layer of electron-emissive material on said surface, said material including an oxide compound of barium as an essential ingredient,
- (c) a sleeve adjacent to said metal substrate,
- (d) and means within said sleeve for heating said substrate and layer at temperatures at which said layer is electron emissive,
- said metal substrate consisting essentially of a major proportion of nickel metal and a minor proportion greater than 1.0 weight percent of chromium metal as an essential reducing agent for progressively reducing said barium oxide to barium metal, said substrate being essentially free from silicon.
A vacuum electron tube comprising an evacuated envelope having therein an indirectly-heated thermionic cathode, said cathode having been prepared by
- (1) providing a bimetal substrate comprising an inner layer consisting essentially of an alloy of nickel and chromium bonded to an outer layer consisting essentially of nickel metal, said inner and outer layers being free from silicon,
- (2) coating the surface of said outer layer with material consisting essentially of oxidic compounds of at least one of barium, strontium and calcium,
- (3) mounting said coated substrate in said envelope,
- (4) evacuating said envelope to a low gas pressure, and then
- (5) heating said substrate and coating at temperatures in the range of 1030.degree. to 1080.degree. K. for at least ten hours, whereby said coating of oxidic compound decomposes to form an oxide layer and chromium migrates into said outer layer.
Dependencies are inferred from the claim text.