US1921065A - Electron emitter and process of making same - Google Patents

Electron emitter and process of making same Download PDF

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Publication number
US1921065A
US1921065A US218998A US21899827A US1921065A US 1921065 A US1921065 A US 1921065A US 218998 A US218998 A US 218998A US 21899827 A US21899827 A US 21899827A US 1921065 A US1921065 A US 1921065A
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US
United States
Prior art keywords
core
oxide
electro
barium
cathode
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
US218998A
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English (en)
Inventor
Joseph A Becker
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.)
AT&T Corp
Original Assignee
Bell Telephone Laboratories Inc
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
Priority to BE352966D priority Critical patent/BE352966A/xx
Priority to NL27285D priority patent/NL27285C/xx
Application filed by Bell Telephone Laboratories Inc filed Critical Bell Telephone Laboratories Inc
Priority to US218998A priority patent/US1921065A/en
Priority to GB17102/28A priority patent/GB297028A/en
Priority to FR658058D priority patent/FR658058A/fr
Application granted granted Critical
Publication of US1921065A publication Critical patent/US1921065A/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
    • 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
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00—Stock material or miscellaneous articles
    • Y10T428/24—Structurally defined web or sheet [e.g., overall dimension, etc.]
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00—Stock material or miscellaneous articles
    • Y10T428/26—Web or sheet containing structurally defined element or component, the element or component having a specified physical dimension
    • Y10T428/261—In terms of molecular thickness or light wave length

Definitions

  • This invention relates to electron emitters and the process of making them.
  • An object of-this invention is to increase the elciency and thermionic activity 'of oxidecoated cathodes.
  • Another object of the invention is to increase the uniformity of the coating of cathodes of the oxide coated type.
  • a cathode is produced in which an electro-positive element is combined with an electro-negative metal or alloy to form a core.
  • a comparatively thin and uniform layer of oxide of the electro-positive element contained in the core may be formed thereon or an oxide layer of a combination of elements may be formed upon the core.
  • An adsorbed layer of the electropositive element is then formed on the exterior of the oxide layer. to produce a highly efficient 20 active cathode for electron discharge devices.
  • a platinum Iridium lament core is alloyed with alkaline earth metals, such as barium and strontium in vacuum.
  • the alloy core is then treated in an oxidizing atmosphere to form a layer or layers of oxide of barium and strontium on the core and thereafter heated in vacuum to such a temperature that some of the metallic barium and strontium will diffuse through the oxide layer and form a thin nlm orv monomolecular layer of active metal on the oxide layer.
  • Fig. 1 shows a filamentary cathode or emitter produced in accordance with this invention
  • Fig. 2 is an enlarged cross-sectional view on the line 2 2 of a portion of the cathode shown in Fig. 1, illustrating the relative thickness of the different materials in the cathode;
  • Fig. 3 illustrates one embodiment of the invention in a three-electrode discharge device.
  • the cathode or electron emitter made in accordance withthis invention comprises a metallic core 10 preferably consisting of an alloy of electro-negative metal and one or more elements of the electro-positive group.
  • a metallic core 10 preferably consisting of an alloy of electro-negative metal and one or more elements of the electro-positive group.
  • Such a core may be made in accordance with this invention by heating platinum or a platinum iridium alloy and a supply of electropositive elements in an evacuated vessel or a reducing atmosphere.
  • the electro-positive material may consist of one or more elements of the alkali group, alkaline earth group or metals of the rare earth group.
  • a desirable material which may be obtained in a relatively pure state consists of metallic barium or a combination of metallic barium and strontium.
  • Barium is particularly desirable since thisA metal has a low work function while the addition of strontium to barium-increases the ability of the barium to adhere to the oxide layer at high temperatures.
  • the alloy produced in this manner may then be drawn into wire form suitable for a cathode core.
  • the drawing operation is preferably performed in a non-oxidizing atmosphere.
  • the alloy core 10 is heated in an oxidizing atmosphere to diffuse some of the barium and strontium to the surface of the core where it forms a coating of barium and strontium oxide 11.
  • the core may be produced on the core by repeated diffusion of the metallic barium and strontium from the core and oxidizing the surface layer.
  • all of the barium and strontium is not diffused from the core, but only suicient diffusion takes place to secure a desirable coating of oxide on the core base 10. It is desirable that this oxide coating be neither too thick nor too thin; 10 to 100 molecular layers is suicient.
  • oxide coating produced on the core in accordance with this invention is distinctly oxide and no'particles of metallic barium or strontium are contained therein. Furthermore, the oxide coating produced in this manner is more uniform over the whole surface of the core 10.
  • the coated cathode is placed in a vessel which has been highly evacuated and the cathode is heated to such a temperature that some of the barium or barium and strontium in the core is diffused through the oxide onto the surface of the filament and forms an adsorbed layer 12 of thermionically active metal containing principally metallic barium or metallic barium and metallic strontium.
  • the layer of pure metal 12 on the oxide 110 layer 1l be a continuous layer or lm.
  • the barium or barium and strontium may cover the surface in an atomic or molecular form or else form colloidal particles on the oxide coating.
  • the relative thicknesses of the materials in the cathode core is shown more clearly in Fig.
  • the metallic layer 12 is a relatively thin film compared with the oxide coating 1l and the diameter of the core 10.
  • the combination of the metal coating 12 and the layers of oxide 11 is responsible for the increased thermionic activity of a filament made in accordance with this invention.
  • the life of the cathode may be increased by the vcontinuous diiusion of additional barium or barium and strontium from the core and their adsorption on the oxide coating.
  • the barium in the core acts as a reservoir to replenish the active layer 12 upon the oxide layer 11.
  • a suitable thermionically active cathode may also be produced by combining the electro-positive material such as metallic barium and strontium with any other electro-negative metal in wire form by forming an alloy on the Wire.
  • the oxidation and diffusion steps heretofore described may then be applied to the alloy Wire core to form an improved cathode or electron emitter in accordance with this invention.
  • the cathode of this invention may also be produced by forming oxides of alkaline earth metal on any suitable core for a cathode and thereafter forming a thin layer of pure metals of the alkaline earth group on the oxidecoating by heating in a vacuum or a deducing atmosphere.
  • FIG. 3 One type of electron discharge device to which this invention is applicable is shown in Fig. 3. It comprises an enclosing vessel 13 having a reentrant stem 14 terminating in a press 15 in which are sealed the leading-in wires for the electrodes.
  • a glass arbor 16 is fused to the side of the stem and extends substantially parallel to the axis thereof.
  • a cathode of electron emitter 1'7. produced in accordance with this invention, is resiliently supported from the arbor 16.
  • a grid electrode 18 and an anode or plate electrode 19 are supported in cooperative relationto the cathode 17 by wires extending from the arbor 16.
  • the invention is applicable to other types of electron discharge devices than that shown in Fig. 3, and it is to be limited only by the scope of the appended claims.
  • An electron emitter comprising acathode core containing an alloy of an electro-negative element and an electro-positive element, an oxide layer on said core, and an adsorbed film of said electro-positive element on said oxide layer.
  • An electron emitter comprising a cathode core containing an alloy of an electro-negative metal and an electro-positive metal, an oxide layer of an electro-positive metal thereon, and a thin film of said electro-positive metal superimposed on said oxide layer.
  • An electron emitter comprising a cathode core containing an alloy of a refractory metal and a metal of the alkaline earth group, a layer of oxide of said metal on said core, and a molecular layer of said metal on said oxide layer.
  • a cathode comprising a core of an alloy of a refractory metal and a metal of the alkaline earth group, a layer of alkaline earth oxide on said core, and an adsorbed thermionically active layer of said metal on said oxide layer.
  • a cathode comprising an alloy core of electro-negative and electro-positive metals, a layer of oxide of the electro-positive metal thereon, and a filmy of active electro-positive metal on said oxide.
  • a cathode comprising an alloy core consisting of platinum and barium, a layer of barium oxide on said core oxide, and a coating of metallic barium on said oxide layer.

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  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Electrodes For Compound Or Non-Metal Manufacture (AREA)
  • Solid Thermionic Cathode (AREA)
US218998A 1927-09-12 1927-09-12 Electron emitter and process of making same Expired - Lifetime US1921065A (en)

Priority Applications (5)

Application Number Priority Date Filing Date Title
BE352966D BE352966A (en)) 1927-09-12
NL27285D NL27285C (en)) 1927-09-12
US218998A US1921065A (en) 1927-09-12 1927-09-12 Electron emitter and process of making same
GB17102/28A GB297028A (en) 1927-09-12 1928-06-13 Electron emitters and process of making same
FR658058D FR658058A (fr) 1927-09-12 1928-07-25 Perfectionnements aux éléments émetteurs d'électrons pour dispositifs à décharge électronique et à leur procédé de fabrication

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US218998A US1921065A (en) 1927-09-12 1927-09-12 Electron emitter and process of making same

Publications (1)

Publication Number Publication Date
US1921065A true US1921065A (en) 1933-08-08

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Family Applications (1)

Application Number Title Priority Date Filing Date
US218998A Expired - Lifetime US1921065A (en) 1927-09-12 1927-09-12 Electron emitter and process of making same

Country Status (5)

Country Link
US (1) US1921065A (en))
BE (1) BE352966A (en))
FR (1) FR658058A (en))
GB (1) GB297028A (en))
NL (1) NL27285C (en))

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5022883A (en) * 1990-11-06 1991-06-11 The United States Of America As Represented By The Secretary Of The Army Method of making a long life high current density cathode from aluminum oxide and tungsten oxide powders

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5022883A (en) * 1990-11-06 1991-06-11 The United States Of America As Represented By The Secretary Of The Army Method of making a long life high current density cathode from aluminum oxide and tungsten oxide powders

Also Published As

Publication number Publication date
FR658058A (fr) 1929-05-30
BE352966A (en))
NL27285C (en))
GB297028A (en) 1929-08-08

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