US3170772A - Oxide coated cathodes for electron tubes - Google Patents

Oxide coated cathodes for electron tubes Download PDF

Info

Publication number
US3170772A
US3170772A US80784A US8078461A US3170772A US 3170772 A US3170772 A US 3170772A US 80784 A US80784 A US 80784A US 8078461 A US8078461 A US 8078461A US 3170772 A US3170772 A US 3170772A
Authority
US
United States
Prior art keywords
layer
oxide coated
core metal
electron tubes
electron
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
US80784A
Inventor
Sato Reiji
Ohtsuki Taro
Suzuki Akira
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.)
Toshiba Corp
Original Assignee
Tokyo Shibaura Electric Co Ltd
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 Tokyo Shibaura Electric Co Ltd filed Critical Tokyo Shibaura Electric Co Ltd
Priority to US80784A priority Critical patent/US3170772A/en
Application granted granted Critical
Publication of US3170772A publication Critical patent/US3170772A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • 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
    • H01J1/26—Supports for the emissive material
    • 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
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S428/00—Stock material or miscellaneous articles
    • Y10S428/922—Static electricity metal bleed-off metallic stock
    • Y10S428/9335—Product by special process
    • Y10S428/934—Electrical process
    • Y10S428/935—Electroplating
    • 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
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S428/00—Stock material or miscellaneous articles
    • Y10S428/922—Static electricity metal bleed-off metallic stock
    • Y10S428/9335—Product by special process
    • Y10S428/941—Solid state alloying, e.g. diffusion, to disappearance of an original layer
    • 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
    • Y10T428/12—All metal or with adjacent metals
    • Y10T428/12493—Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, joint, etc.]
    • Y10T428/12535—Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, joint, etc.] with additional, spatially distinct nonmetal component
    • 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
    • Y10T428/12—All metal or with adjacent metals
    • Y10T428/12493—Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, joint, etc.]
    • Y10T428/12535—Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, joint, etc.] with additional, spatially distinct nonmetal component
    • Y10T428/12611—Oxide-containing component
    • 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
    • Y10T428/12—All metal or with adjacent metals
    • Y10T428/12493—Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, joint, etc.]
    • Y10T428/12771—Transition metal-base component
    • Y10T428/12861—Group VIII or IB metal-base component
    • Y10T428/12944—Ni-base component

Definitions

  • This invention relates to improvements in oxide coated cathodes for electron tubes.
  • a conventional oxide coated cathode comprises a core or base of metal containing a minor quantity of C, Mg, Al, Si, Cr, W, Ti, U, Th, Zr, Be or other element that can reduce oxides, and an oxide coating.
  • the reducing el ments as enumerated above serve to reduce the alkaliearth oxides covering the core metal to form an alkaliearth layer having good thermal emissivity.
  • Another object of the present invention is to provide electron tubes of improve performance and extended life.
  • a core metal 1 according to the present invention is applied during one step of its manufacture with a very thin layer of anti-oxidizing metal 2 plated thereon, and an emitter coating 3 of emitter materialsof suitable oxides or the raw material of conventionalcarbonates is formed on the anti-oxidizing layer 2 by painting or the like.
  • the core metal 1 is formed of nickel containing a minor quantity of a reducing element or elements selected from the group consisting of C, Mg, Al, Si, Cr, W, Ti, U, Th, Zr, Be and the like that are effective to reduce the oxides of the coating 3.
  • the preferred metal suitable for forming the thin anti-oxidizing layer 2 is platinum or pure nickel.
  • the metal of thin antioxidizing layer 2 is incorporated unitarily with the core metal 1.
  • the thin anti-oxidizing layer 2 is temporarily present and substantially disappears by virtue of the heat treatment during its manufacture to form a substantially uniform structure with the core metal 1.
  • the anti-oxidizing 3,170,772 Patented Feb. 23, 1965 CCv layer 2 can be so formed that it effectively protects the surface portion of core metal 1 against oxidization during the exhausting operation of electron tube and its aging. It then disappears when a high vacuum has been established in the tube. oxidizing layer 2, it disappears by formation of a solid solution with core metal 1.
  • the core metal 1 and the reducing elements contained therein diffuse outwardly into the purev nickel antioxidizing layer 2, thus forming a uniform and indiscriminate core or base on which usual oxide coating is formed.
  • the surface portion of core metal 1 will not be oxidized during the heat treatment of the cathode, and any substantial boundary layer of insulating or other undesirable character is not formed between the core metal and oxide coating.
  • the interface resistance between the core metal and the oxide coating is extremely low.
  • the reducing elements contained in the base metal can react directly with the oxide coating without obstruction by any intermediary layer. There results an effective reduction of the oxide layer, so that the lowering of mutual conductance as well as electron emissivity of the vacuum tube is kept small throughout the whole life of the tube and eventually extends the useful life of the tube.
  • peeling off of the oxide coating is effectively prevented, and a superior oxide coated cathode with stable performance is obtained.
  • core metals 1 of nickel containing 0.04% of Mg and 4.0% of W were plated with pure nickel layers 2 of l to 5 micron thickness, and painted thereon with conventional emitter materials such as alkali-earth carbonates forming the emitter coating 3.
  • .Such cathodes were assembled into 616 type vacuum tubes. These tubes were tested in comparison with standard 616 type vacuum tubes of the same ratings underthe same operating conditions for the same period of working time. The average rate of lowering of mutual conductance of the new tubes was lower than a half of that of standard tubes. When operated under more severe conditions, a more decreased rate of lowering of mutual conductance has been obtained.
  • An oxide coated cathode having a minimized interface resistance for an electron tube said cathode comprising a core metal of about 0.04% magne sium, 4% tungsten and the remainder nickel, a layer of pure nickel having a thickness between 1 to 5 microns plated on said core metal, and a layer of emitter materials applied over said layer of pure nickel whereby when said cathode is heated said layer of pure nickel is incorporated with said core metal so that no interface layer exists between said emitter material and said core metal.

Description

Feb. 23, 1965 REL]; s o ETAL 3,170,772
OXIDE COATED CATHODES FOR ELECTRON TUBES Filed Jan. 5, 1961 United States Patent 3,170,772 OXIDE COATED CA I'IHBOEDES FOR ELECTRON U S Reiji Sato and Taro Ohtsuki, Tokyo, and Akira Suzuki, Kawasaki-shi, Japan, assignors to Tokyo Shibaura Electric Co., Ltd., Kawasaki-ski, Japan, a corporation of Japan Filed Jan. 5, 1961, Ser. No. 80,784 1 Claim. (Cl. 29-183.5)
This invention relates to improvements in oxide coated cathodes for electron tubes.
A conventional oxide coated cathode comprises a core or base of metal containing a minor quantity of C, Mg, Al, Si, Cr, W, Ti, U, Th, Zr, Be or other element that can reduce oxides, and an oxide coating. The reducing el ments as enumerated above serve to reduce the alkaliearth oxides covering the core metal to form an alkaliearth layer having good thermal emissivity.
It has been found, however, that most of the reducing elements contained in the base metals form boundary layers of insulating compounds between the base metals and the oxide coatings. These boundary layers tend to produce contact potentials or increase interface resistance, thus impairing the performance of electron emissive cathodes. It has also been found that the very time when such a boundary layer is formed during the manufacture of an electron tube is in the stages of decomposition of alkaliearth carbonates, the raw materials for forming the desired oxides, and subsequent aging of the electron tube, when the cathode is heat treated in a gas atmosphere within the tube.
It is, a primary object of the. present invention to provide oxide coated cathodes for electron tubes having minimum interface resistance and thus to improve the thermal emissivity of the cathodes.
Another object of the present invention is to provide electron tubes of improve performance and extended life.
Other objects and advantages of the present invention, which become apparent from the following description with reference to the accompanying drawings, in which the single figure is an enlarged fragmental sectional view of a cathode embodying the present invention showing its laminar construction at a particular stage during its manufacture.
Referring to the sole figure, a core metal 1 according to the present invention is applied during one step of its manufacture with a very thin layer of anti-oxidizing metal 2 plated thereon, and an emitter coating 3 of emitter materialsof suitable oxides or the raw material of conventionalcarbonates is formed on the anti-oxidizing layer 2 by painting or the like. According to the present invention, the core metal 1 is formed of nickel containing a minor quantity of a reducing element or elements selected from the group consisting of C, Mg, Al, Si, Cr, W, Ti, U, Th, Zr, Be and the like that are effective to reduce the oxides of the coating 3. The preferred metal suitable for forming the thin anti-oxidizing layer 2 is platinum or pure nickel.
When the cathode as above-specified is heated during the course of its manufacture, the metal of thin antioxidizing layer 2 is incorporated unitarily with the core metal 1. In other words, it should be noted that the thin anti-oxidizing layer 2 is temporarily present and substantially disappears by virtue of the heat treatment during its manufacture to form a substantially uniform structure with the core metal 1.
By appropriately selecting the material of the anti-oxidizing layer 2 as well as its thickness, the anti-oxidizing 3,170,772 Patented Feb. 23, 1965 CCv layer 2 can be so formed that it effectively protects the surface portion of core metal 1 against oxidization during the exhausting operation of electron tube and its aging. It then disappears when a high vacuum has been established in the tube. oxidizing layer 2, it disappears by formation of a solid solution with core metal 1. When pure nickel is employed, the core metal 1 and the reducing elements contained therein diffuse outwardly into the purev nickel antioxidizing layer 2, thus forming a uniform and indiscriminate core or base on which usual oxide coating is formed.
Consequently, according to the present invention, the surface portion of core metal 1 will not be oxidized during the heat treatment of the cathode, and any substantial boundary layer of insulating or other undesirable character is not formed between the core metal and oxide coating. Thus, the interface resistance between the core metal and the oxide coating is extremely low. In addition, after the anti-oxidizing layer 2 has disappeared as hereinbefore explained, the reducing elements contained in the base metal can react directly with the oxide coating without obstruction by any intermediary layer. There results an effective reduction of the oxide layer, so that the lowering of mutual conductance as well as electron emissivity of the vacuum tube is kept small throughout the whole life of the tube and eventually extends the useful life of the tube. In addition, peeling off of the oxide coating is effectively prevented, and a superior oxide coated cathode with stable performance is obtained.
As practical examples of the present cathodes, core metals 1 of nickel containing 0.04% of Mg and 4.0% of W were plated with pure nickel layers 2 of l to 5 micron thickness, and painted thereon with conventional emitter materials such as alkali-earth carbonates forming the emitter coating 3. .Such cathodes were assembled into 616 type vacuum tubes. These tubes were tested in comparison with standard 616 type vacuum tubes of the same ratings underthe same operating conditions for the same period of working time. The average rate of lowering of mutual conductance of the new tubes was lower than a half of that of standard tubes. When operated under more severe conditions, a more decreased rate of lowering of mutual conductance has been obtained.
What is claimed is:
An oxide coated cathode having a minimized interface resistance for an electron tube, said cathode comprising a core metal of about 0.04% magne sium, 4% tungsten and the remainder nickel, a layer of pure nickel having a thickness between 1 to 5 microns plated on said core metal, and a layer of emitter materials applied over said layer of pure nickel whereby when said cathode is heated said layer of pure nickel is incorporated with said core metal so that no interface layer exists between said emitter material and said core metal. 8
References Cited by the Examiner UNITED STATES PATENTS DAVID L. R ECK, Primary Examiner. WHITMORE A. WILTZ, HYLAND BIZOT, Examiners.
When platinum is used as the anti
US80784A 1961-01-05 1961-01-05 Oxide coated cathodes for electron tubes Expired - Lifetime US3170772A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
US80784A US3170772A (en) 1961-01-05 1961-01-05 Oxide coated cathodes for electron tubes

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US80784A US3170772A (en) 1961-01-05 1961-01-05 Oxide coated cathodes for electron tubes

Publications (1)

Publication Number Publication Date
US3170772A true US3170772A (en) 1965-02-23

Family

ID=22159593

Family Applications (1)

Application Number Title Priority Date Filing Date
US80784A Expired - Lifetime US3170772A (en) 1961-01-05 1961-01-05 Oxide coated cathodes for electron tubes

Country Status (1)

Country Link
US (1) US3170772A (en)

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3374385A (en) * 1963-07-10 1968-03-19 Rca Corp Electron tube cathode with nickel-tungsten alloy base and thin nickel coating
US3419744A (en) * 1964-08-17 1968-12-31 Sylvania Electric Prod Integral laminated cathode and support structure
FR2337885A1 (en) * 1976-01-08 1977-08-05 Westinghouse Electric Corp ALKALINE IONIZATION DETECTOR
US4136227A (en) * 1976-11-30 1979-01-23 Mitsubishi Denki Kabushiki Kaisha Electrode of discharge lamp
FR2404912A1 (en) * 1977-09-30 1979-04-27 Hitachi Ltd ELECTRONIC TUBE CATHODE, AND ITS MANUFACTURING PROCESS
US4273683A (en) * 1977-12-16 1981-06-16 Hitachi, Ltd. Oxide cathode and process for production thereof
US4279784A (en) * 1977-12-26 1981-07-21 Hitachi, Ltd. Thermionic emission cathodes
US4308178A (en) * 1979-09-17 1981-12-29 North American Philips Consumer Electronics Corp. Thermionic cathode emitter coating
US4313854A (en) * 1978-11-15 1982-02-02 Hitachi, Ltd. Oxide-coated cathode for electron tube
US5102363A (en) * 1985-03-18 1992-04-07 Hitachi, Ltd. Manufacturing method of indirectly heated cathode

Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1197615A (en) * 1911-10-26 1916-09-12 Gen Electric Compound metal.
US2447038A (en) * 1945-10-31 1948-08-17 Raytheon Mfg Co Cathode structure
US2543439A (en) * 1945-05-02 1951-02-27 Edward A Coomes Method of manufacturing coated elements for electron tubes
US2557372A (en) * 1948-02-21 1951-06-19 Westinghouse Electric Corp Manufacture of thoria cathodes
US2878410A (en) * 1954-11-09 1959-03-17 Gen Electric Electronic tube structure
US2912611A (en) * 1953-08-14 1959-11-10 Int Standard Electric Corp Thermionic cathodes
US2965793A (en) * 1959-05-12 1960-12-20 Westinghouse Electric Corp Electron device
US2996795A (en) * 1955-06-28 1961-08-22 Gen Electric Thermionic cathodes and methods of making

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1197615A (en) * 1911-10-26 1916-09-12 Gen Electric Compound metal.
US2543439A (en) * 1945-05-02 1951-02-27 Edward A Coomes Method of manufacturing coated elements for electron tubes
US2447038A (en) * 1945-10-31 1948-08-17 Raytheon Mfg Co Cathode structure
US2557372A (en) * 1948-02-21 1951-06-19 Westinghouse Electric Corp Manufacture of thoria cathodes
US2912611A (en) * 1953-08-14 1959-11-10 Int Standard Electric Corp Thermionic cathodes
US2878410A (en) * 1954-11-09 1959-03-17 Gen Electric Electronic tube structure
US2996795A (en) * 1955-06-28 1961-08-22 Gen Electric Thermionic cathodes and methods of making
US2965793A (en) * 1959-05-12 1960-12-20 Westinghouse Electric Corp Electron device

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3374385A (en) * 1963-07-10 1968-03-19 Rca Corp Electron tube cathode with nickel-tungsten alloy base and thin nickel coating
US3419744A (en) * 1964-08-17 1968-12-31 Sylvania Electric Prod Integral laminated cathode and support structure
FR2337885A1 (en) * 1976-01-08 1977-08-05 Westinghouse Electric Corp ALKALINE IONIZATION DETECTOR
US4047101A (en) * 1976-01-08 1977-09-06 Westinghouse Electric Corporation Filament for alkali metal ionization detector
US4136227A (en) * 1976-11-30 1979-01-23 Mitsubishi Denki Kabushiki Kaisha Electrode of discharge lamp
FR2404912A1 (en) * 1977-09-30 1979-04-27 Hitachi Ltd ELECTRONIC TUBE CATHODE, AND ITS MANUFACTURING PROCESS
US4273683A (en) * 1977-12-16 1981-06-16 Hitachi, Ltd. Oxide cathode and process for production thereof
US4279784A (en) * 1977-12-26 1981-07-21 Hitachi, Ltd. Thermionic emission cathodes
US4313854A (en) * 1978-11-15 1982-02-02 Hitachi, Ltd. Oxide-coated cathode for electron tube
US4308178A (en) * 1979-09-17 1981-12-29 North American Philips Consumer Electronics Corp. Thermionic cathode emitter coating
US5102363A (en) * 1985-03-18 1992-04-07 Hitachi, Ltd. Manufacturing method of indirectly heated cathode

Similar Documents

Publication Publication Date Title
US3170772A (en) Oxide coated cathodes for electron tubes
US4313854A (en) Oxide-coated cathode for electron tube
US2233917A (en) Black coating for electron discharge devices
US4291252A (en) Electron tube cathode
US1883898A (en) Thermionic cathode
US3535757A (en) Method for making cathode assembly for electron tube
US3183396A (en) Method of manufacturing sintered cathode
US2226720A (en) Reduction of undesired emissions of electronic discharge devices
US6362563B1 (en) Two-layer cathode for electron gun
US3240569A (en) Cathode base structure
CA1274580A (en) Vacuum electron tube having an oxide cathode comprising chromium reducing agent
US5102363A (en) Manufacturing method of indirectly heated cathode
US1981620A (en) Electrode for electron discharge devices
US4119761A (en) Heat radiation anode
US2552535A (en) Electron discharge device electrode
CN1099513A (en) Oxide cathode
JPS58106734A (en) Directly heated electron tube cathode
JP2951939B2 (en) Cathode for electron tube
US2872611A (en) Cathode
KR920008786B1 (en) Cathode
US3530559A (en) Anode electrode fabrication
US3342634A (en) Method of producing black, metalcontaining surface layers
US2837423A (en) Nickel base cathode emissive alloy
JPH0624091B2 (en) Oxide cathode structure
KR830000725B1 (en) Tube cathode