US2929133A - Dispenser cathode - Google Patents

Dispenser cathode Download PDF

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Publication number
US2929133A
US2929133A US608130A US60813056A US2929133A US 2929133 A US2929133 A US 2929133A US 608130 A US608130 A US 608130A US 60813056 A US60813056 A US 60813056A US 2929133 A US2929133 A US 2929133A
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US
United States
Prior art keywords
cathode
mixture
carbon
barium
cathodes
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US608130A
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English (en)
Inventor
Ray C Hughes
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
US Philips Corp
North American Philips Co Inc
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US Philips Corp
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Filing date
Publication date
Priority to BE560502D priority Critical patent/BE560502A/xx
Priority to NL101006D priority patent/NL101006C/xx
Application filed by US Philips Corp filed Critical US Philips Corp
Priority to US608130A priority patent/US2929133A/en
Priority to GB27384/57A priority patent/GB816997A/en
Priority to DEN14060A priority patent/DE1040701B/de
Priority to FR1201432D priority patent/FR1201432A/fr
Application granted granted Critical
Publication of US2929133A publication Critical patent/US2929133A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J1/00—Details of electrodes, of magnetic control means, of screens, or of the mounting or spacing thereof, common to two or more basic types of discharge tubes or lamps
    • H01J1/02—Main electrodes
    • H01J1/13—Solid thermionic cathodes
    • H01J1/20—Cathodes heated indirectly by an electric current; Cathodes heated by electron or ion bombardment
    • H01J1/28—Dispenser-type cathodes, e.g. L-cathode
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J9/00—Apparatus or processes specially adapted for the manufacture, installation, removal, maintenance of electric discharge tubes, discharge lamps, or parts thereof; Recovery of material from discharge tubes or lamps
    • H01J9/02—Manufacture of electrodes or electrode systems
    • H01J9/04—Manufacture of electrodes or electrode systems of thermionic cathodes
    • H01J9/042—Manufacture, activation of the emissive part

Definitions

  • My invention relates to dispenser cathodes, and in particular to thermionic, dispenser cathodes 'of the type comprising an alkaline earth metal compound dispersed in a refractory metal matrix, and to methods of making such cathodes.
  • a cathode comprising a pressed and sintered mixture of powdered refractory metal and barium aluminate.
  • a reaction occurs between the aluminate and the refractory metal productive of free alkaline earth metal, i.e., barium, which is then supplied to a surface' of the pressed body and forms a monatomic layer thereon.
  • free alkaline earth metal i.e., barium
  • the cathode described in said patent exhibits an important drawback, to wit, that after assembly in a discharge tube, it requires an aging period of about 24 hours before its emission reaches a maximum, stable value. This aging treatment makes more complex the manufacture of the cathode, and results in an attendant increase in cost and time consumption.
  • the chief object of my invention is to provide an improved cathode of the "type described in which the aging time to realize full emission is materially shortened and preferably substantially eliminated.
  • my invention involves the incorporation into the cathode mixture prior to pressing and sintering of a small amount of a reducing substance, such as carbon, capable of binding up any excess oxygen-present in the pressed mixture during the sintering and activation there,- of and forming therewith'gaseous reaction products, which may then bedriven ed and thus removed from the resultant cathode.
  • a reducing substance such as carbon
  • a planar cathode comprising a cylindrical, H-shaped in cross-section, refractory metal support 10, for example, of molybdenum.
  • a body 11 constituted of a pressed and sintered mixture of refractory metal and alkaline earth metal compound.
  • the lower chamber formed by the support houses the usual heating filament 12.
  • the upper, exposed surface 13 of the body 11 constitutes the electron emissive surface. While the invention is being described in connection with a planar cathode, it will be appreciated that the principles thereof are equally applicable to cylindrical or other types of cathodes for producing various shapes of electron beams.
  • the cathode shown may be manufactured in the following way.
  • a refractory metal powder of the 2 proper composition is provided.
  • a refractory metal powder of the 2 proper composition is provided.
  • an alloy of tungsten and molybdenum as described in a copending application, Serial No. 392,966, filed. November 18, 1953, issued as Patent No. 2,899,592 is employed.
  • a preferred form of this alloy is molybdenum and 25% tungsten in weight percent.
  • my invention is not to be limited to cathodes made only of this particular alloy, as the results desired can be obtained with alloys in which the tungsten varies upwards from 10% and even including pure tungsten alone.
  • the invention will also be operable with other refractory metals, such as tantalum, for example, or alloys of tantalum with molybdenum.
  • an alkaline earth metal compound capable of reacting therewith, when heated, to produce free alkaline earth metal.
  • the alkaline earth metal compound I prefer to use barium aluminate, since with the latter material uniform ly excellent cathodes have been produced.
  • the barium aluminate may be produced in the following way. To 5 moles of barium carbonate, which decomposes upon heating to barium oxide, is added 2 moles of aluminum oxide and 0.3 mole of calcium oxide. The mixture is then fused, and, upon solidfication, pulverized into a powder.
  • the composition of the resultant product is not precisely known, but it is believed to be a mixture of normal and basic aluminates of barium and calcium.
  • the calcium serves mainly to increase the emission and is preferably included, though satisfactory cathodes can be madewithout the addition of the calcium.
  • the barium oxide preferably constitutes between 60 and by weight of the aluminates, as is set forth in my aforementioned patent.
  • the powdered alloy and aluminate composition are then intimately mixed in the proportions of about 9 parts of the refractory metal alloy to about 1 part of the aluminate, considerable variation in these proportions being possible, and the mixture fired at l,700 C. for about /2 minute to fuse the alkaline earth metal com pounds.
  • the fused compounds, in this case the aluminates flow and are dispersed over the metal alloy particles resulting in a more uniform distribution of pow ders, which tends to eliminate voids and improve the smoothness of the surface of the sintered body, which is subsequently formed.
  • the fired mixture is then crushed and finely ground, and then to the resultant powder is added up to 1% by weight of powdered carbon.
  • the resultant cathode is then removed from the furnace, the filament 12 mounted in the lower chamber, and the cathode assembled into the envelope of an electric discharge tube.
  • the tube is then placed on a pumping system and evacuated. While pumping out, the various electrodes are degassed by the usual high frequency Patented Mar. 2 2, 1960.
  • the cathode in turn, is degassed and activated by simply heating it at a temperature about 100 C.
  • the temperature employed for degassing is chosen to be 1,100".
  • C. "In less than about one minute of heating on the pumping system, full emission from the cathode is realized, after which the tube may be tipped-off and thus permanently sealed. If a getter is present, it may then be flashed,.and the tube is ready to be used. No aging is necessary, as compared to similar cathodes made without the carbon in which aging times of '24 hours was necessary to achieve full emission from the cathode. I
  • the 1% upper limit of the carbon is believed due to the fact that an excess of carbon remaining in the cathode, namelv, carbon not reacting with oxygen and being driven off as a gas, is harmful and causes a drop in emission.
  • the optimum quantity of carbon is just that amount capable of completely tying up the excess oxygen and thus being removed as a gas, leaving no harmful residues. This amount has been found to be about of one percent.
  • Another interesting and completely unexpected result of the invention is an increase in emission of up to 30% as compared to prior art pressed cathodes made without the carbon. This increase in emission. as yet has no logical explanation.
  • a method of manufacturing a dispenser cathode comprising providing a powder mixture of refractory metal, a fused mixture of barium oxide and aluminum oxide wherein the former constitutes between and by weight of the fused mixture, and more than zero and up to about 1% by weight of carbon, and thereafter pressing and sintering said mixture to form a coherent body.
  • the powder mixture contains as the refractory metal an alloy of tungsten and molybdenum, and also contains a small amount of calcium aluminate.
  • a method of manufacturing a dispenser cathode comprising providing a mixture of powders of refractory metal anda fused mixture of barium oxide and aluminum oxide wherein the former constitutes between 60 and 90% by Weight of the fused mixture, heating said mixture at a temperature atv which the mixture of barium oxide and aluminum oxide fuses and is dispersed over the metal powder, thereafter pulverizing the mixture to form a powder again, thereafter mixing with the thusformedpowdermore.
  • han Zero and up to about 1% by weight of carbon, and thereafter pressing and sintering the mixture to form a strong, compact body.
  • thermonic cathode comprising a pressed and sintered mixture of barium aluminate, a refractory metal and more than zero and up to about 1% by weight of carbon, wherein the barium aluminate comprises a fused mixture of barium oxide and aluminum oxide with the former constituting between 60 and 90% by weight of the fused mixture, and means for heating the mixture at an elevated temperature' 6.
  • the mixture contains as the refractory metal an alloy of tungsten and molybdenum, a small amount of calcium aluminate, and about 0.1% of carbon.

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  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Solid Thermionic Cathode (AREA)
  • Powder Metallurgy (AREA)
US608130A 1956-09-05 1956-09-05 Dispenser cathode Expired - Lifetime US2929133A (en)

Priority Applications (6)

Application Number Priority Date Filing Date Title
BE560502D BE560502A (is") 1956-09-05
NL101006D NL101006C (is") 1956-09-05
US608130A US2929133A (en) 1956-09-05 1956-09-05 Dispenser cathode
GB27384/57A GB816997A (en) 1956-09-05 1957-08-30 Improvements in or relating to dispenser cathodes
DEN14060A DE1040701B (de) 1956-09-05 1957-08-30 Verfahren zur Herstellung einer aus einem gepressten und gesinterten Gemisch bestehenden Vorratskathode
FR1201432D FR1201432A (fr) 1956-09-05 1957-09-03 Cathode pressée et son procédé de fabrication

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US608130A US2929133A (en) 1956-09-05 1956-09-05 Dispenser cathode

Publications (1)

Publication Number Publication Date
US2929133A true US2929133A (en) 1960-03-22

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ID=24435167

Family Applications (1)

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US608130A Expired - Lifetime US2929133A (en) 1956-09-05 1956-09-05 Dispenser cathode

Country Status (6)

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US (1) US2929133A (is")
BE (1) BE560502A (is")
DE (1) DE1040701B (is")
FR (1) FR1201432A (is")
GB (1) GB816997A (is")
NL (1) NL101006C (is")

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3055763A (en) * 1958-07-10 1962-09-25 Jack R Kreigh Metal-aggregate product
US3169862A (en) * 1961-01-10 1965-02-16 Ciba Ltd Process for making anodes for electrolytic condensers
US3269804A (en) * 1963-11-01 1966-08-30 Gen Electric Dispenser cathode and method for the production thereof
US3275435A (en) * 1963-11-01 1966-09-27 Gen Electric Method of production of a dispenser cathode
US3558966A (en) * 1967-03-01 1971-01-26 Semicon Associates Inc Directly heated dispenser cathode
US3688150A (en) * 1965-06-30 1972-08-29 Siemens Ag Degassing arrangement for electron beam tube including an mk dispenser cathode
US4393328A (en) * 1979-11-09 1983-07-12 Thomson-Csf Hot cathode, its production process and electron tube incorporating such a cathode
WO1989009480A1 (en) * 1988-03-28 1989-10-05 Hughes Aircraft Company Expandable dispenser cathode
DE3913338A1 (de) * 1989-04-22 1990-10-25 Licentia Gmbh Einbettmasse, insbesondere fuer kathoden von elektronenroehren

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1552310A (en) * 1923-07-24 1925-09-01 Gen Electric Electrode for discharge tubes
US1720000A (en) * 1926-07-28 1929-07-09 Westinghouse Lamp Co Vibration and sag resistant filament
US1883898A (en) * 1928-12-14 1932-10-25 Westinghouse Electric & Mfg Co Thermionic cathode
US1895354A (en) * 1929-10-23 1933-01-24 Gen Electric Resintered hard metal composition
US2179960A (en) * 1931-11-28 1939-11-14 Schwarzkopf Paul Agglomerated material in particular for electrical purposes and shaped bodies made therefrom
US2246166A (en) * 1939-02-02 1941-06-17 Gen Electric Sintered hard-metal alloy for implements and tools
US2700118A (en) * 1951-11-29 1955-01-18 Philips Corp Incandescible cathode

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AT187993B (de) * 1953-11-18 1956-12-10 Philips Nv Kathodenkörper für eine elektrische Entladungsröhre

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1552310A (en) * 1923-07-24 1925-09-01 Gen Electric Electrode for discharge tubes
US1720000A (en) * 1926-07-28 1929-07-09 Westinghouse Lamp Co Vibration and sag resistant filament
US1883898A (en) * 1928-12-14 1932-10-25 Westinghouse Electric & Mfg Co Thermionic cathode
US1895354A (en) * 1929-10-23 1933-01-24 Gen Electric Resintered hard metal composition
US2179960A (en) * 1931-11-28 1939-11-14 Schwarzkopf Paul Agglomerated material in particular for electrical purposes and shaped bodies made therefrom
US2246166A (en) * 1939-02-02 1941-06-17 Gen Electric Sintered hard-metal alloy for implements and tools
US2700118A (en) * 1951-11-29 1955-01-18 Philips Corp Incandescible cathode

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3055763A (en) * 1958-07-10 1962-09-25 Jack R Kreigh Metal-aggregate product
US3169862A (en) * 1961-01-10 1965-02-16 Ciba Ltd Process for making anodes for electrolytic condensers
US3269804A (en) * 1963-11-01 1966-08-30 Gen Electric Dispenser cathode and method for the production thereof
US3275435A (en) * 1963-11-01 1966-09-27 Gen Electric Method of production of a dispenser cathode
US3688150A (en) * 1965-06-30 1972-08-29 Siemens Ag Degassing arrangement for electron beam tube including an mk dispenser cathode
US3558966A (en) * 1967-03-01 1971-01-26 Semicon Associates Inc Directly heated dispenser cathode
US4393328A (en) * 1979-11-09 1983-07-12 Thomson-Csf Hot cathode, its production process and electron tube incorporating such a cathode
WO1989009480A1 (en) * 1988-03-28 1989-10-05 Hughes Aircraft Company Expandable dispenser cathode
DE3913338A1 (de) * 1989-04-22 1990-10-25 Licentia Gmbh Einbettmasse, insbesondere fuer kathoden von elektronenroehren
DE3913338C2 (de) * 1989-04-22 1999-12-02 Aeg Elektronische Roehren Gmbh Einbettmasse, insbesondere für Kathoden von Elektronenröhren, Verfahren zur Herstellung einer solchen Einbettmasse und Verwendung einer solchen Einbettmasse

Also Published As

Publication number Publication date
DE1040701B (de) 1958-10-09
FR1201432A (fr) 1959-12-30
NL101006C (is")
GB816997A (en) 1959-07-22
BE560502A (is")

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