US2830218A - Dispenser cathodes and methods of making them - Google Patents

Dispenser cathodes and methods of making them Download PDF

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Publication number
US2830218A
US2830218A US382085A US38208553A US2830218A US 2830218 A US2830218 A US 2830218A US 382085 A US382085 A US 382085A US 38208553 A US38208553 A US 38208553A US 2830218 A US2830218 A US 2830218A
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United States
Prior art keywords
cathode
recess
cover
holder
refractory metal
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
US382085A
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English (en)
Inventor
James E Beggs
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General Electric Co
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General Electric Co
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Filing date
Publication date
Priority to NL96853D priority Critical patent/NL96853C/xx
Application filed by General Electric Co filed Critical General Electric Co
Priority to US382085A priority patent/US2830218A/en
Priority to GB23248/54A priority patent/GB757272A/en
Priority to FR1112390D priority patent/FR1112390A/fr
Application granted granted Critical
Publication of US2830218A publication Critical patent/US2830218A/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

  • Dispenser type cathodes having a porous metal cover for a reservoir of thermionic material are advantageously employed in many applications especially in view of the long life permitted by the reservoir of thermionic material and the ease with which the cathode surface may be machined for accurate spacing from other electrode surfaces.
  • the enclosed emission material be exposed only through the pores of the dispenser cover, it is necessary that the remainder of the holder be impervious and that the cover be very tightly fitted to the holder. Emission from the sides of the porous cathode cover rather than from the upper surface only has been found to impair the high frequency performance of discharge devices in which such cathodes are employed because of the different transit angles of different parts of the electron stream.
  • both the cathode holder and its porous cover are made of compacted refractory metal powders which are sintered together in their assembled position with the cathode acti vating material enclosed.
  • the cathode holder sinters more readily than the cover by employing a refractory metal having a lower sintering temperature than tungsing without. closing the pores. Because it begins to sinter at a lower temperature, the cathode holder shrinks more than does the porous cover so that it both grips the cover tightly and is sintered to it.
  • Fig. 1 illustrates apparatus for compacting a cathode holder
  • Fig. 2 illustrates apparatus for compacting a powdered metal cathode cover
  • Fig. 3 represents a dispenser cathode made in accordance with the teachings of my invention and employing the cathode holder and cover of Figs. '1 and 2; and
  • Fig. 4 illustrates another embodiment of a dispenser axis.
  • a piston or ram 3 is arranged to enter the bore of the mold 1 from its upper end and compact powdered materialwithin the mold.
  • the ram 3 has a tapered end portion .4 of reduced diameter terminated in a plane transverse to the axis of the bore.
  • the mold 1 is filled with a powdered refractory metal before the ram is introduced.
  • Molybdenum is preferably employed, although other metal powders such as nickel or tungsten may be used.
  • the particle sizes are chosen so that with the ram pressure employed the cathode holder is so densely compacted that after sintering it is mechanically strong and substantially impervious to the diffusion of an activator material therethrough.
  • the pressed or compacted powder part to be employed as a cathode holder is formed as a hollow cylinder 5 with a transverse inner partition 6, the recesses on either side of the partition being formed by the core 2 and the reduced end portion 4 of the ram.
  • the upper recess is designed to be the reservoir for the active cathode material or cathode activator and the lower recess is preferably longer to enclose a cathode heater.
  • the thickness of the cathode holder partition 6 is made less than the thickness of the cylinder walls to increase the effectiveness of the heater.
  • Fig. 2 illustrates the apparatus for making or pressing the powder part which constitutes the cathode cover.
  • the mold 7 has a cylindrical bore closed at the lower end and having a bevel or taper 8 from the bottom of the bore to a height representing the desired thickness of
  • a cylindrical ram 9 is arranged to enter the top of the cylindrical bore and to compress powder filling the wall '7 to the desired thickness.
  • the completed compacted powder cover itlis a cylindrical disk having tapered side walls. The angle of taper corresponds to that of the upper portion of the cathode holder 5' so that the disk may fit within the upper recess of the cathode holder with its upper surface flush with the upper end of the holder.
  • the refractory metal powder employed in the disk It) is preferably tungsten, although other material such as molybdenum or tantalum may be substituted.
  • the cover 10 however is not compacted so firmly or to such a high percentage of its maximum density as is the cathode holder 5 in order that for 'a given sintering temperature, the cathode disk may be relatively porous and frangible as compared with the cathode holder 5.
  • a completed cathode assembly is shown in Fig. 3.
  • The, assembly is formed by positioning a quantity of cathode activator material, suitably in the form of a pellet 11 on the upper surface of the partition 6 of the cathode holder 5.
  • the cathode cover 10 is then fitted into the top of the upper recess in the holder thus enclosing the cathode activating material.
  • the pressed powder parts and it) are both relatively soft and porous and must be handled carefully to avoid breakage. Either or both may also be presintered to some degree to facilitate handling, if so desired.
  • the assembly is then heated in a furnace to a temperature sufiicient to sinter both pressed powder parts.
  • a temperature of 1400 C. or generally in the range of 1300" to 2000 C. is sufficient to sinter the powdered assembly.
  • the sintering process is preferably carried out in vacuum or in a hydrogen atmosphere to minimize oxidation of the cathode.
  • Other reducing or inert atmospheres may also be employed, the choice depending to some extent upon the particular cathode activating material enclosed within the cathode.
  • the cathode activating material 11 which may suitably be barium carbonate, functions in a manner known in the art to activate the upper surface of the cathode cover 10.
  • the barium carbonate Upon heating of the carbonate, as occurs during the sintering process, the barium carbonate dissociates, reducing to barium oxide. Further heating is believed to cause the barium oxide to react with the tungsten, producing barium.
  • the barium atoms slowly migrate along the'tortuous, indirect paths defined by the pores, eventually diffusing through to the outer surface of the cathode cover 10 and forming a monatomic layer whose effect is to reduce the work function of the tungsten from around 4.5 electron volts to a value from 1.6 to 2.0 electron volts.
  • the barium oxide alone is not the emitter but rather than the barium layer together with the tungsten base provides the efiicient electron emitting surface characterizing this general type of cathode.
  • the barium carbonate placed in the reservoir of the cathode has been referred to as a cathode activating material and the term as used herein is intended to include metallic barium may be employed or metallic barium itself may be employed.
  • Other alkaline earth metals either singly or in combination may also be employed either in the form of the metals themselves or compounds Which may be reduced to provide them.
  • the upper surface of the cathode including the upper surface of the cathode cover It) is milled or otherwise machined to the exact dimensions required.
  • the porous disk 10 is relatively frangible and hence the machining operation, which in effect scrapes off an upper layer, can be effected without compressing or smearing the material and filling in the pores, which would, of course, adversely affect the operation of the cathode. It will be appreciated that despite the relative softness of the cathode cover 10 no difficulties are encountered in handling the material since it is integral with the mechanically stronger cathode holder 5.
  • a cathode heater 12. is suitably mounted within the lower recess of the holder 5.
  • the cathode 4 activation mentioned above is completed, the activation having been begun during the sintering process.
  • the cathode is not poisoned or permanently damaged but instead may be reactivated or the activation continued by further heating until the desired monatomic barium layer on the tungsten is obtained as evidenced by stable emission.
  • FIG. 4 A modification of my invention is indicated in the drawing at Fig. 4.
  • the cathode holder 13 corresponds to the holder 5 of Fig. 3 and is made by the same method.
  • the particular holder 13 of Fig. 3 also has an enlarged diameter or flange 14 at its upper end to facilitate the addition of a cylindrical metal foil heat shield and support 15.
  • the body 11 of the cathode activating material is closely surrounded by the packed powder parts. This is accomplished after withdrawal of the ram 3 from the holder mold by placing the cathode activator charge in the upper recess without removing the cathode holder 13 from the mold.
  • the unitary sintered assembly possesses the advantages also discussed in connection with Fig. 3 in that the porous portion 16 is sintered to the holder with the emitting surface restricted to its upper surface and the paths for the cathode activating material to the cathode surface restricted to the pores of the portion 16.
  • a dispenser cathode comprising a sintered integral refractory metal body having a recess receiving a quantity of thermionic emitting material, a sintered face portion closing said recess, said face portion of the body being porous relative to the remainder of said body to provide forthe gradual egress of emitting material from said recess.
  • a dispenser cathode comprising a substantially impervious sintered refractory metal recessed holder, a thermionic activator material positioned therein, and a porous sintered refractory metal face member in said recess sintered to said holder and enclosing said material.
  • a dispenser cathode comprising a sintered substantially impervious hollow tubular refractory metal member having a transverse partition therein to define a recess in each end of said tubular member, 1a thermionic activator material positioned in the recess at said one end, a porous sintered refractory metal plug in said one end sintered thereto and integral therewith, and a cathode heater positioned in the other recess in said tubular member.
  • a dispenser cathode comprising a sintered substantially impervious hollow tubular refractory metal member having a transverse partition therein to define a recess in each end of said tubular member, a thermionic activator meterial positioned in the recess at one end thereof, a porous sintered refractory metal cover completely filling the remainder of the space in said one end and sintered thereto and integral therewith, and a cathode heater positioned in the other recess in said tubular member.
  • a dispenser cathode which comprises forminga recessed cathode container member 1 from a densely packed refractory metal powder having a given sintering temperature, positioning a quantity of thermionic activator material within the recess of said containenpositioning a container cover of less densely packed refractory metal powder having a sintering temperature higher than said given temperature in said recess, and heating the assembly to sinter the refractory metal powders and join the said cover and said container together.
  • a dispenser cathode which comprises forming a recessed cathode container member from a packed refractory metal powder having a given sinteringtemperature, positioning a quantity of thermionic activator material within the recess of said container, positioning a container cover of a packed refractory metal powder having a higher sintering temperature than said given temperature in said recess, and heating the assembly to sinter the refractory metal powders and join said cover and said container together.
  • a dispenser cathode which comprises forming a recessed cathode container member from a densely packed refractory metal powder, positioning a quantity of thermionic activator material within the recess of said container, positioning a container cover of less densely packed refractory metal powder in said recess and sintering the assembly to join said cover and said container together.
  • a dispenser cathode which comprises forming a recessed cathode container member from a densely packed refractory metal powder, positioning a quantity of thermionic activator material within the recess of said container, positioning a container cover of less densely packed refractory metal powder in said recess, and heating the assembly to sinter the refractory metal powder and at least partially activate the cathode.
  • the method of making a dispenser cathode which comprises forming a cathode container member having a recess therein from a densely packed refractory metal powder, positioning a quantity of thermionic activator material within the recess of said container, packing the remainder of the recess with a refractory metal powder .less densely packed than said container member powder,
  • a dispenser cathode which comprises forming a recessed cathode container member from a densely packed molybdenum powder, positioning a quantity of thermionic activator material within the recess of said container, positioning a less densely packed tungsten container cover of powder in said recess, and heating the assembly to sinter the powders whereby the container and cover are integrally sintered together.
  • a dispenser cathode which comprises forming a recessed cathode container member from a densely packed molybdenum powder, positioning a quantity of thermionic activator material within the recess of said container, forming a less densely packed tungsten container cover of powder in said recess, and heating the assembly to sinter the powders whereby the container and cover are integrally sintered together.

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  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Solid Thermionic Cathode (AREA)
  • Powder Metallurgy (AREA)
US382085A 1953-09-24 1953-09-24 Dispenser cathodes and methods of making them Expired - Lifetime US2830218A (en)

Priority Applications (4)

Application Number Priority Date Filing Date Title
NL96853D NL96853C (is") 1953-09-24
US382085A US2830218A (en) 1953-09-24 1953-09-24 Dispenser cathodes and methods of making them
GB23248/54A GB757272A (en) 1953-09-24 1954-08-10 Improvements relating to dispenser cathodes
FR1112390D FR1112390A (fr) 1953-09-24 1954-09-10 Cathodes à réserve

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US382085A US2830218A (en) 1953-09-24 1953-09-24 Dispenser cathodes and methods of making them

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US2830218A true US2830218A (en) 1958-04-08

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US (1) US2830218A (is")
FR (1) FR1112390A (is")
GB (1) GB757272A (is")
NL (1) NL96853C (is")

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2945150A (en) * 1958-12-11 1960-07-12 Gen Electric Thermionic cathodes and methods of making
US2971246A (en) * 1957-01-26 1961-02-14 Philips Corp Method of producing cavity-type dispenser cathode
DE1112209B (de) * 1959-03-20 1961-08-03 Siemens Ag Mittelbar geheizte Kathode mit einer scheibenfoermigen Emissionsflaeche und mit einer Halterung aus nahtlosem Folie-Rohr
US3045320A (en) * 1959-03-12 1962-07-24 Raytheon Co Impregnated cathodes
US3323916A (en) * 1964-10-23 1967-06-06 Westinghouse Electric Corp Method of making heater assemblies by wet-settling techniques
US3441780A (en) * 1966-03-29 1969-04-29 Siemens Ag Indirectly heated dispenser cathode for electronic discharge devices
US3911309A (en) * 1972-09-18 1975-10-07 Patent Treuhand Ges Fuer Elektrische Gluehlampen Mbh Electrode comprising a porous sintered body
DE3527360A1 (de) * 1985-07-31 1987-02-05 Licentia Gmbh Vorratskathode
DE3708687A1 (de) * 1986-04-01 1987-10-08 Ceradyne Inc Vorratskathode und verfahren zu deren herstellung
DE3627384A1 (de) * 1986-08-12 1988-02-18 Siemens Ag Indirekt geheizte vorratskathode, insbesondere metall-kapillar-kathode, fuer elektrische entladungsgefaesse
EP0915492A1 (en) * 1997-11-04 1999-05-12 Sony Corporation Impregnated cathode and method of manufacturing the same, electron gun and electron tube
US20120158110A1 (en) * 2010-12-20 2012-06-21 Heraeus Precious Materials Gmbh & Co. Kg Method for manufacturing a medical implant and medical implant

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2121589A (en) * 1934-06-28 1938-06-21 Westinghouse Electric & Mfg Co Emissive incandescent cathode
US2460739A (en) * 1946-04-17 1949-02-01 Gen Electric Electrode construction
US2543728A (en) * 1947-11-26 1951-02-27 Hartford Nat Bank & Trust Co Incandescible cathode
US2643332A (en) * 1949-03-29 1953-06-23 Hartford Nat Bank & Trust Co High-frequency electron discharge tube system
US2663069A (en) * 1951-07-20 1953-12-22 Philips Lab Inc Method of making incandescent cathodes
US2673277A (en) * 1949-10-25 1954-03-23 Hartford Nat Bank & Trust Co Incandescible cathode and method of making the same
US2700118A (en) * 1951-11-29 1955-01-18 Philips Corp Incandescible cathode

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2121589A (en) * 1934-06-28 1938-06-21 Westinghouse Electric & Mfg Co Emissive incandescent cathode
US2460739A (en) * 1946-04-17 1949-02-01 Gen Electric Electrode construction
US2543728A (en) * 1947-11-26 1951-02-27 Hartford Nat Bank & Trust Co Incandescible cathode
US2643332A (en) * 1949-03-29 1953-06-23 Hartford Nat Bank & Trust Co High-frequency electron discharge tube system
US2673277A (en) * 1949-10-25 1954-03-23 Hartford Nat Bank & Trust Co Incandescible cathode and method of making the same
US2663069A (en) * 1951-07-20 1953-12-22 Philips Lab Inc Method of making incandescent cathodes
US2700118A (en) * 1951-11-29 1955-01-18 Philips Corp Incandescible cathode

Cited By (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2971246A (en) * 1957-01-26 1961-02-14 Philips Corp Method of producing cavity-type dispenser cathode
US2945150A (en) * 1958-12-11 1960-07-12 Gen Electric Thermionic cathodes and methods of making
US3045320A (en) * 1959-03-12 1962-07-24 Raytheon Co Impregnated cathodes
DE1112209B (de) * 1959-03-20 1961-08-03 Siemens Ag Mittelbar geheizte Kathode mit einer scheibenfoermigen Emissionsflaeche und mit einer Halterung aus nahtlosem Folie-Rohr
US3323916A (en) * 1964-10-23 1967-06-06 Westinghouse Electric Corp Method of making heater assemblies by wet-settling techniques
US3441780A (en) * 1966-03-29 1969-04-29 Siemens Ag Indirectly heated dispenser cathode for electronic discharge devices
US3911309A (en) * 1972-09-18 1975-10-07 Patent Treuhand Ges Fuer Elektrische Gluehlampen Mbh Electrode comprising a porous sintered body
DE3527360A1 (de) * 1985-07-31 1987-02-05 Licentia Gmbh Vorratskathode
DE3708687A1 (de) * 1986-04-01 1987-10-08 Ceradyne Inc Vorratskathode und verfahren zu deren herstellung
DE3627384A1 (de) * 1986-08-12 1988-02-18 Siemens Ag Indirekt geheizte vorratskathode, insbesondere metall-kapillar-kathode, fuer elektrische entladungsgefaesse
US4803397A (en) * 1986-08-12 1989-02-07 Siemens Aktiengesellschaft Indirectly heated dispenser metal capillary cathode for electrical discharge devices
EP0915492A1 (en) * 1997-11-04 1999-05-12 Sony Corporation Impregnated cathode and method of manufacturing the same, electron gun and electron tube
US20120158110A1 (en) * 2010-12-20 2012-06-21 Heraeus Precious Materials Gmbh & Co. Kg Method for manufacturing a medical implant and medical implant
US8951464B2 (en) * 2010-12-20 2015-02-10 Heraeus Precious Metals Gmbh & Co. Kg Method for manufacturing a medical implant and medical implant

Also Published As

Publication number Publication date
FR1112390A (fr) 1956-03-13
NL96853C (is")
GB757272A (en) 1956-09-19

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