EP0248470A1 - Méthode de fabrication d'une cathode à réserve - Google Patents

Méthode de fabrication d'une cathode à réserve Download PDF

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Publication number
EP0248470A1
EP0248470A1 EP87200951A EP87200951A EP0248470A1 EP 0248470 A1 EP0248470 A1 EP 0248470A1 EP 87200951 A EP87200951 A EP 87200951A EP 87200951 A EP87200951 A EP 87200951A EP 0248470 A1 EP0248470 A1 EP 0248470A1
Authority
EP
European Patent Office
Prior art keywords
tungsten body
scandium oxide
surface area
electron emission
tungsten
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.)
Granted
Application number
EP87200951A
Other languages
German (de)
English (en)
Other versions
EP0248470B1 (fr
Inventor
Johannes Van Esdonk
Jan Hasker
Antonius Hendrikus Maria Swemmers
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.)
Koninklijke Philips NV
Original Assignee
Philips Gloeilampenfabrieken NV
Koninklijke Philips Electronics NV
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Philips Gloeilampenfabrieken NV, Koninklijke Philips Electronics NV filed Critical Philips Gloeilampenfabrieken NV
Publication of EP0248470A1 publication Critical patent/EP0248470A1/fr
Application granted granted Critical
Publication of EP0248470B1 publication Critical patent/EP0248470B1/fr
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • 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
    • 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
    • H01J9/047—Cathodes having impregnated bodies

Definitions

  • the invention relates to a method of manufacturing a dispenser cathode comprising a porous tungsten body having a surface area intended for electron emission, which tungsten body incorporates scandium oxide at least in a layer adjacent the surface area intended for electron emission, and which tungsten body containing the scandium oxide is impregnated with an oxidic material after sintering.
  • the tungsten body can then be given the required shape mechanically (US-A 26 69 008).
  • the copper is removed from the tungsten body by evaporation in a vacuum.
  • the method described in the opening paragraph is therefore characterized in that molten copper is absorbed in the entire scandium oxide-­containing sintered tungsten body prior to impregnation and in that the copper is removed from the tungsten body after a mechanical design treatment of the tungsten body which is effected at least on the side of the surface area intended for electron emission.
  • the method according to the invention is surprising because the processibility of the tungsten body, even if it contains a comparatively high percentage by volume of scandium oxide, is very satisfactory in the presence of copper. Furthermore, the copper can be removed in a comparatively simple manner after the mechanical operation so that there is certainly no question of an expensive, time-­consuming and cumbersome method.
  • a scandium oxide content of preferably 2 to 10% by weight is used in the tungsten body.
  • a scandium oxide content of 3 to 7% by weight is used with special preference in the tungsten body.
  • the mechanical treatment preferably extends from the surface area intended for elecron emission throughout a scandium oxide-containing layer adjacent the surface area.
  • the drawing diagrammatically shows in a cross-­section a part of a dispenser cathode manufactured by means of the method according to the invention.
  • a dispenser cathode which has a porous tungsten body 1 with a surface area 2 intended for electron emission scandium oxide is incorporated in a layer 3 adjacent the surface area 2 intended for electron emission.
  • This is effected, for example, as follows.
  • a 0.5 mm thick layer of tungsten powder is introduced into a mould having a circular opening with a diameter of 1.8 mm.
  • a 0.1 mm thick layer of powder consisting of a mixture of tungsten and 5% by weight of scandium oxide is provided on the layer of tungsten powder.
  • the pellet After compression to a pellet the pellet is sintered in hydrogen at 1500°C for 1 hour. The total thickness of the sintered body is then approximately 0.6 mm and the thickness of the layer 3 is approximately 0.1 mm.
  • molten copper is absorbed in the entire scandium oxide-containing sintered tungsten body 1.
  • the body is provided with oxygen-free copper as a plate or a pellet in a quantity which is at least equal to the free space in the sintered body (the free space in the sintered body is approximately 20%) and is absorbed as a melt in the tungsten body.
  • the tungsten body 1 is subjected to a mechanical design treatment at least on the side of the surface area 2 intended for electron emission.
  • the latter treatment may be a conventional treatment such as turning, drilling or milling.
  • the design treatment extends throughout the layer 3 and the size of the scandium oxide-containing layer 3 is limited so that also the surface area 2 intended for electron emission is limited.
  • the copper is removed from the tungsten body. This is effected, for example, by means of nitric acid and water in a 1:1 ratio so that substantially all copper is removed. After cleaning and rinsing any possible last remainders of copper are removed by evaporation for several minutes at 1700°C in hydrogen. By burning the hydrogen flowing from the equipment the absence of copper can be established by the absence of a green colour. Subsequently the tungsten body is impregnated in a conventional manner with oxides of barium, calcium and aluminium (4:1:1), cleaned and welded to a shaft 4 provided with a heating element 5.
  • the dispenser cathode shown in the drawing is used, for example, as a component of a diode gun in a cathode ray tube.
  • a diode gun in a cathode ray tube.
  • Such a gun accommodates above the cathode an anode 6 having a small aperture 7 (diameter, for example, 40 ⁇ m).
  • the beam current passes through this aperture during operation while the anode potential is of course positive with respect to the cathode. Since the diameter of the electron emitting part is small ( ⁇ 0.3 mm) due to the processing operation, the thermal load of the anode may be sufficiently low.

Landscapes

  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Solid Thermionic Cathode (AREA)
EP87200951A 1986-05-29 1987-05-20 Méthode de fabrication d'une cathode à réserve Expired - Lifetime EP0248470B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
NL8601374A NL8601374A (nl) 1986-05-29 1986-05-29 Werkwijze voor het vervaardigen van een naleveringskathode.
NL8601374 1986-05-29

Publications (2)

Publication Number Publication Date
EP0248470A1 true EP0248470A1 (fr) 1987-12-09
EP0248470B1 EP0248470B1 (fr) 1990-03-28

Family

ID=19848086

Family Applications (1)

Application Number Title Priority Date Filing Date
EP87200951A Expired - Lifetime EP0248470B1 (fr) 1986-05-29 1987-05-20 Méthode de fabrication d'une cathode à réserve

Country Status (5)

Country Link
EP (1) EP0248470B1 (fr)
JP (1) JPH0711935B2 (fr)
KR (1) KR870011653A (fr)
DE (1) DE3762075D1 (fr)
NL (1) NL8601374A (fr)

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4236287A (en) * 1979-06-25 1980-12-02 The United States Of America As Represented By The Secretary Of The Army Method of making a ruggedized high current density cathode
EP0179513A1 (fr) * 1984-10-05 1986-04-30 Koninklijke Philips Electronics N.V. Procédé de fabrication d'une cathode à réserve comprenant du scandate et cathode à réserve fabriquée par ce procédé

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4236287A (en) * 1979-06-25 1980-12-02 The United States Of America As Represented By The Secretary Of The Army Method of making a ruggedized high current density cathode
EP0179513A1 (fr) * 1984-10-05 1986-04-30 Koninklijke Philips Electronics N.V. Procédé de fabrication d'une cathode à réserve comprenant du scandate et cathode à réserve fabriquée par ce procédé

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
JOURNAL OF PHYSICS D, vol. 4, no. 1, January 1971, pages 39-46, Letchworth, Hertfordshire, GB; N.K. MITRA: "A small high current-density thermionic emitter" *

Also Published As

Publication number Publication date
EP0248470B1 (fr) 1990-03-28
KR870011653A (ko) 1987-12-24
DE3762075D1 (de) 1990-05-03
JPH0711935B2 (ja) 1995-02-08
NL8601374A (nl) 1987-12-16
JPS62281223A (ja) 1987-12-07

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