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| Size for forming glass fibers having a reduced tendency to give gumming deposits |
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| Method of preparing ferromagnetic material |
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| Acicular .alpha.-iron particles, their preparation and recording media employing same |
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| Stable colloidal dispersions of triacontanol |
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Method of manufacturing a dispenser cathode and the use of the method
| Details |
Inventors: van Esdonk, Johannes; van Hal, Henricus A. M.; van Lith, Josef J.;
Assignee: U.S. Philips Corporation (New York, NY)
Primary Examiner: Ramsey; Kenneth J.
Assistant Examiner:
Attorney, Agent or Firm: Spain; Norman N.
The invention relates to a method of manufacturing a dispenser cathode having a porous tungsten body, in which a metal oxide is provided in the body and the body is impregnated with barium. Good results as regards life and resistance to ion bombardment are obtained if the comparatively cheap oxides of gallium and indium are used. |
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DETAILED DESCRIPTION OF THE INVENTION If the indium- or gallium oxide is provided in a surface layer of the dispenser body, a content of metal oxide from 2 to 20% by weight calculated on metal oxide + tungsten, in particular approximately 10% by weight, is preferably used.
The said contents give particularly good results, for example, an emission of 70-80 A/cm.
sup.
2 at a temperature of 950.
degree.
C.
and a life of the cathode at of least 10,000 hours, while moreover the cathode withstands very well an ion bombardment.
A first embodiment of the method according to the invention is characterized in that a powder layer of indium oxide and/or gallium oxide and tungsten is provided on top of a volume of tungsten powder, after which the whole is compressed and sintered and impregnated via a metal oxide-free surface.
Particularly good results are obtained when an indium- and/or gallium oxide-containing layer is used which at the surface destined for emission extends over a thickness of from 20 to 100 .
mu.
m.
A second embodiment of the method according to the invention is characterized in that a tungsten compact is provided which comprises the indium oxide and/or gallium oxide mixed through the whole tungsten compact, a content of metal oxide from 0.
5 to 5% by weight, in particular approximately 2% by weight, being used.
It has been found that when gallium oxide and/or indium oxide is incorporated in the whole volume of tungsten powder (matrix), the resulting body after compaction and sintering absorbs better than when scandium oxide is used.
The method according to the invention is particularly suitable for the manufacture of, for example, L-cathodes.
Some embodiments of the method according to the invention will now be described with reference to a few examples and the accompanying drawing in which FIG.
1 is a diagrammatic longitudinal sectional view of a part of a first dispenser cathode manufactured by means of the method according to the invention, and FIG.
2 is a diagrammatic longitudinal sectional view of a part of a second dispenser cathode again manufactured by means of the method according to the invention
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Manufacturing Materials 
