EP0298558B1 - Verfahren zur Herstellung einer Scandat-Kathode - Google Patents

Verfahren zur Herstellung einer Scandat-Kathode Download PDF

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Publication number
EP0298558B1
EP0298558B1 EP88201392A EP88201392A EP0298558B1 EP 0298558 B1 EP0298558 B1 EP 0298558B1 EP 88201392 A EP88201392 A EP 88201392A EP 88201392 A EP88201392 A EP 88201392A EP 0298558 B1 EP0298558 B1 EP 0298558B1
Authority
EP
European Patent Office
Prior art keywords
cathode
scandium
hydride
approximately
manufacturing
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
EP88201392A
Other languages
English (en)
French (fr)
Other versions
EP0298558A1 (de
Inventor
Johannes Van Esdonk
Jan Hasker
Josef Johannes Van Lith
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 EP0298558A1 publication Critical patent/EP0298558A1/de
Application granted granted Critical
Publication of EP0298558B1 publication Critical patent/EP0298558B1/de
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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
    • 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
    • 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

Definitions

  • the invention relates to a method of manufacturing a dispenser cathode comprising a barium compound for dispensing barium to an emissive surface of a porous cathode body substantially comprising a metal melting at a high temperature.
  • the invention also relates to an electron tube provided with a cathode manufactured by such a method.
  • a characteristic feature of dispenser cathodes is that there is a functional separation between the electron emissive surface on the one hand and a store of the emitter material for realizing a sufficiently low work function on the emissive surface on the other hand.
  • the emitter material is present in the pores of the porous metal cathode body.
  • European Patent Specification No. 0,091,161 describes how such cathodes can be improved on sensitivity to and recovery after ion bombardment by compressing the cathode body (notably the top layer) from a mixture of tungsten powder and scandium oxide and by subsequently sintering it.
  • the compressing operation is generally performed in two steps. Firstly, the tungsten portion of the cathode body is slightly pre-compressed. Subsequently, the top layer powder is evenly distributed over a surface of the tungsten portion whereafter the definitive compressing operation is performed.
  • European Patent Specification 0.179.513 describes a method in which the porous body is obtained from a mixture of scandium hydride-tungsten powder and tungsten powder.
  • the scandium hydride-tungsten powder is obtained by compressing tungsten powder into a porous plug, into the pores if which scandium is drawn. After cooling in hydrogen the plug becomes brittle due to the fact that scandium is partly converted into scandiumhydride.
  • the plug is then pulverized and the fragments are heated in a hydrogen atmosphere. After cooling substantially all the scandium is converted into scandium hydride. The fragments are then ground to a powder consisting of tungsten grains having scandium hydride in their pores.
  • a method according to the invention is characterized in that the cathode body is compressed from a quantity of metal powder which is mixed with scandium or scandium hydride whereafter the body is sintered and the cathode is provided with emitter material.
  • the quantity of scandium hydride in the quantity of metal powder is preferably 0.3-0.7 % by weight.
  • Such a method is more advantageous because compressing is only to be performed in one operation and the distribution of the top-layer powder is no longer necessary. Also the method of preparing scandium hydride/tungsten grains can be dispensed with. After the introduction of the impregnant the cathode bodies manufactured by means of such a method can undergo mechanical treatments such as turning or other types of shaping without any detrimental effects.
  • this sintering operation is preferably performed at a temperature which is lower than the melting point of scandium (1539°C).
  • the sintering temperature must be chosen to be as high as possible in order to obtain a sufficiently robust cathode body.
  • a preferred embodiment of a method according to the invention is therefore characterized in that the sintering temperature is between 1430°C and 1500°C.
  • Figure 1 is a longitudinal cross-section of a cathode according to the invention.
  • the cathode body 1 is compressed from a mixture of tungsten powder and approximately 0.5% by weight of scandium or scandium-hydride. After compressing at a pressure of approximately 3.5 atmosphere and sintering in hydrogen for approximately one hour at 1450°, the cathode body of scandium and tungsten has a porosity of approximately 20%.
  • the cathode body 1 now has, for example, a thickness of 0.5 mm and a diameter of approximately 1.8 mm.
  • the cathode body 1 is impregnated in a hydrogen atmosphere with barium calcium aluminate (for example, 5BaO; 2Al2O3; 3CaO or 4BaO; 1Al2O3; 1CaO), compressed in a holder 2 and welded onto the cathode shank 3.
  • barium calcium aluminate for example, 5BaO; 2Al2O3; 3CaO or 4BaO; 1Al2O3; 1CaO
  • the cathode shank 3 accommodates a coiled cathode filament 4 comprising a helically wound metal core 5 and an aluminium oxide insulating layer 6.
  • the emission of the emissive surface 7 of such a cathode was approximately 100 A/cm2 at 950°C obtained at a pulse load at 1000 V in a diode with a cathode-anode distance of 0.3 mm.
  • Such an emission is comparable to that of a cathode with a top layer of tungsten and scandium oxide as described in European Patent Application No. 0,178,716 (PHN 11,169) which is more difficult to manufacture.
  • the recovery after ion bombardment was comparable to that of the cathode described in that Application with a cathode body sintered at approximately 1900°C (approximately 65%). In a cathode according to the invention, sintered at 1500°C this recovery was poorer and was approximately 58%.
  • the impregnant absorption was approximately 4.5%.
  • this absorption decreased to approximately 2% which shortens the life time of the cathode.
  • the quantity of absorbed impregnant is sufficient; the recovery after ion bombardment did not show any significant change in this range.
  • a cylinder 20 with an emissive surface 21 in which a heating element is provided and which is shown in an elevational view in Figure 2 can also be turned from a tungsten body compressed in accordance with the method as described hereinbefore.
  • the cathodes according to the invention may be used in electron tubes such as, for example magnetrons, transmitter tubes, etc., but also in cathode-ray tubes for e.g. television applications and electron microscopy.

Landscapes

  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Solid Thermionic Cathode (AREA)
  • Powder Metallurgy (AREA)

Claims (6)

  1. Verfahren zum Herstellen einer Nachlieferkathode mit einer Bariumverbindung zum Nachliefern von Barium nach einer emittierenden Oberfläche eines porösen Kathodenkörpers, der im wesentlichen ein bei hoher Temperatur schmelzendes Metall enthält, dadurch gekennzeichnet, daß der Kathodenkörper aus einer Metallpulvermenge gepreßt wird, wobei das Metallpulver mit Scandium oder Scandiumhydrid vermischt ist, wonach der Körper gesintert und die Kathode mit Emittermaterial versehen wird.
  2. Verfahren nach Anspruch 1, dadurch gekennzeichnet, daß die Scandium- oder Scandiumhydridmenge in der Mischung aus Metallpulver und Scandium oder Scandiumhydrid etwa 0,3 bis 0,7 Gew. % beträgt.
  3. Verfahren nach Anspruch 1 oder 2, dadurch gekennzeichnet, daß die Sintertemperatur niedriger als die Schmelztemperatur des Scandiums ist.
  4. Verfahren nach Anspruch 3, dadurch gekennzeichnet, daß die Sintertemperatur zwischen 1430°C und 1500°C liegt.
  5. Verfahren nach einem oder mehreren der vorangehenden Ansprüche, dadurch gekennzeichnet, daß der Kathodenkörper eine endgültige Form erhält, nachdem er mit Emittermaterial versehen ist.
  6. Elektronenröhre mit einer Kathode, die mit Hilfe eines Verfahrens nach den Ansprüchen 1 bis 5 hergestellt worden ist.
EP88201392A 1987-07-06 1988-07-04 Verfahren zur Herstellung einer Scandat-Kathode Expired - Lifetime EP0298558B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
NL8701583A NL8701583A (nl) 1987-07-06 1987-07-06 Scandaatkathode.
NL8701583 1987-07-06

Publications (2)

Publication Number Publication Date
EP0298558A1 EP0298558A1 (de) 1989-01-11
EP0298558B1 true EP0298558B1 (de) 1994-05-25

Family

ID=19850259

Family Applications (1)

Application Number Title Priority Date Filing Date
EP88201392A Expired - Lifetime EP0298558B1 (de) 1987-07-06 1988-07-04 Verfahren zur Herstellung einer Scandat-Kathode

Country Status (5)

Country Link
EP (1) EP0298558B1 (de)
JP (1) JP2685232B2 (de)
KR (1) KR890002949A (de)
DE (1) DE3889696T2 (de)
NL (1) NL8701583A (de)

Families Citing this family (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NL8902793A (nl) * 1989-11-13 1991-06-03 Philips Nv Scandaatkathode.
EP0651419B1 (de) * 1993-10-28 1998-06-24 Koninklijke Philips Electronics N.V. Vorratskathode und Herstellungsverfahren
BE1007676A3 (nl) * 1993-10-28 1995-09-12 Philips Electronics Nv Werkwijze voor het vervaardigen van een naleveringskathode.
BE1007677A3 (nl) * 1993-10-28 1995-09-12 Philips Electronics Nv Werkwijze voor het vervaardigen van een naleveringskathode.
US5407633A (en) * 1994-03-15 1995-04-18 U.S. Philips Corporation Method of manufacturing a dispenser cathode
US6281626B1 (en) * 1998-03-24 2001-08-28 Casio Computer Co., Ltd. Cold emission electrode method of manufacturing the same and display device using the same

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NL165880C (nl) * 1975-02-21 1981-05-15 Philips Nv Naleveringskathode.
JPS58154131A (ja) * 1982-03-10 1983-09-13 Hitachi Ltd 含浸形陰極
NL8201371A (nl) * 1982-04-01 1983-11-01 Philips Nv Werkwijzen voor het vervaardigen van een naleveringskathode en naleveringskathode vervaardigd volgens deze werkwijzen.
NL8403032A (nl) * 1984-10-05 1986-05-01 Philips Nv Werkwijze voor het vervaardigen van een scandaatnaleveringskathode, naleveringskathode vervaardigd met deze werkwijze.
NL8403031A (nl) * 1984-10-05 1986-05-01 Philips Nv Werkwijze voor het vervaardigen van een scandaatnaleveringskathode en scandaatnaleveringskathode vervaardigd volgens deze werkwijze.
JPS63254636A (ja) * 1987-04-10 1988-10-21 Hitachi Ltd 含浸形陰極

Also Published As

Publication number Publication date
DE3889696D1 (de) 1994-06-30
EP0298558A1 (de) 1989-01-11
JPH01163941A (ja) 1989-06-28
KR890002949A (ko) 1989-04-12
DE3889696T2 (de) 1994-12-08
NL8701583A (nl) 1989-02-01
JP2685232B2 (ja) 1997-12-03

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