US3495120A - Microheating elements,more particularly for cathodes of electron tubes - Google Patents
Microheating elements,more particularly for cathodes of electron tubes Download PDFInfo
- Publication number
- US3495120A US3495120A US706897A US3495120DA US3495120A US 3495120 A US3495120 A US 3495120A US 706897 A US706897 A US 706897A US 3495120D A US3495120D A US 3495120DA US 3495120 A US3495120 A US 3495120A
- Authority
- US
- United States
- Prior art keywords
- cathodes
- elements
- electron tubes
- microheating
- heating
- 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
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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
- H01J1/22—Heaters
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01C—RESISTORS
- H01C7/00—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material
- H01C7/02—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material having positive temperature coefficient
- H01C7/022—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material having positive temperature coefficient mainly consisting of non-metallic substances
-
- 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
- H01J1/15—Cathodes heated directly by an electric current
Definitions
- MICROHEATING ELEMENTS MORE PARTICULARLY FUR CATHODES OF ELECTRON TUBES Filed Feb. 20, 1968 INVENTORS WILHELMUS E KNIPPENBERG PIETER ZALM BY M AEmr United States Patent 3,495,120 MICROHEATING ELEMENTS, MORE PARTIC- ULARLY FOR CATHODES OF ELECTRON TUBES 1 Wilhelmus Franciscus Knippenberg, and Pieter Zalm, Em-
- a microheating element for an electron discharge tube is disclosed as a support of monocrystalline silicon carbide material and a layer of emissive material covering a portion of the surface of the support, whereby said support constitutes the heating element for the cathode.
- This invention relates to microheating elements, which are to be understood in this specification to mean elements which are not longer than a few millimetres.
- Such heating elements may especially be used for heating cathodes for small size electron tubes such as used, for example, in mobilophones and transistorised television sets.
- Heating elements of metal have the disadvantage that their resistivity is comparatively low so that stable elements of a sufliciently high resistance cannot be obtained or with difiiculty only.
- Semiconductor materials have a higher resistivity. In view of the purpose above referred to, the materials must be able to withstand high temperatures and must also be chemically resistant. This desired combination of properties is found with silicon carbide.
- micro heating elements could be obtained by grinding olf siliconcarbide crystals, but these are comparatively expensive and diflicult to grind to size. If use is made of considerably cheaper siliconcarbide plates obtained by sintering, then difliculties are encountered in manufacturing large quantities of elements of uniform resistivity. Furthermore, sintered elements of small dimensions are very weak in mechanical respect.
- the invention relates to a microheating element, especially for cathodes of electron tubes, and is characterized in that the element comprises a filamentary siliconcarbide crystal.
- Filamentary crystals which are frequently referred to in engineering as whiskers, are to be understood in this specification to mean not only crystals of circular crosssection but also crystals of polygonal cross-section and strip-shaped crystals.
- Such silicon crystals may, for example, be reproducibly deposited in the required small thickness on the Wall of a space bounded by silicon carbide by recrystallisation and/ or condensation in an inert gas containing lanthanum at temperatures above 2000 C., more particularly between 2200" C. and 2600 C.
- the whisker crystals are grown on Patented Feb. 10, 1970 a substrate from a gas phase containing silicon and carbon by locally providing finely-divided iron on the substrate and heating to a temperature above 1200 C., during which process silicon and carbon are absorbed from the gas phase by the iron and silicon carbide crystals are deposited on the substrate.
- heating elements it is important for them to have a positive temperature coeflicient of the resistance. This may in the present example be achieved by carrying out the whisker crystallisation in an atmosphere containing an addition, such as nitrogen.
- Whiskers of the desired thickness and resistivity can be obtained in the manner described, whereas division of the whiskers in the direction of length provides a large number of heating elements.
- the siliconcarbide crystal is indicated by 1.
- Current supply wires 2 may be provided in a simple manner by connecting the ends of a whisker part 1 to a wire of a refactory metal, for example, by means of soldering materal 3 consisting of a gold alloy containing 5% by weight of tantalum.
- soldering materal 3 consisting of a gold alloy containing 5% by weight of tantalum.
- Such joints can withstand temperatures up to 1300 C.
- Suitable soldering materials for higher temperatures may be, for example, nickel containing 5% by Weight of molybdenum (up to 1500 C.) or tungsten (up to 1800" C.).
- the heating element 1 When using the heating element 1 in a cathode of an electron tube, it is important that the heating circuit should be separated from the emission circuit.
- this may be achieved in a simple manner by providing an insulating layer 4 which can withstand high temperatures, for example, a layer consisting of oxide or nitride of aluminium or silicon, and applying to this layer a metal layer and a mass 5 of, for example, barium oxide containing an addition of calcium, which emits electrons upon heating.
- a cathode for an electron discharge tube comprising, a support consisting of monocrystalline silicon carbide, a layer of emissive material covering a portion of the surface of said support, and means for connecting said support to a source of electrical current, whereby said support constitutes a heating element for said cathode 2.
Landscapes
- Engineering & Computer Science (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Ceramic Engineering (AREA)
- Physics & Mathematics (AREA)
- Electromagnetism (AREA)
- Solid Thermionic Cathode (AREA)
- Carbon And Carbon Compounds (AREA)
- Crystals, And After-Treatments Of Crystals (AREA)
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
NL6703548A NL6703548A (ja) | 1967-03-07 | 1967-03-07 |
Publications (1)
Publication Number | Publication Date |
---|---|
US3495120A true US3495120A (en) | 1970-02-10 |
Family
ID=19799479
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US706897A Expired - Lifetime US3495120A (en) | 1967-03-07 | 1968-02-20 | Microheating elements,more particularly for cathodes of electron tubes |
Country Status (7)
Country | Link |
---|---|
US (1) | US3495120A (ja) |
CH (1) | CH469351A (ja) |
DE (1) | DE1639354A1 (ja) |
ES (1) | ES351239A1 (ja) |
FR (1) | FR1558677A (ja) |
GB (1) | GB1222887A (ja) |
NL (1) | NL6703548A (ja) |
Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5118983A (en) * | 1989-03-24 | 1992-06-02 | Mitsubishi Denki Kabushiki Kaisha | Thermionic electron source |
US5475281A (en) * | 1991-02-25 | 1995-12-12 | U.S. Philips Corporation | Cathode |
US20200066474A1 (en) * | 2018-08-22 | 2020-02-27 | Modern Electron, LLC | Cathodes with conformal cathode surfaces, vacuum electronic devices with cathodes with conformal cathode surfaces, and methods of manufacturing the same |
CN111243917A (zh) * | 2020-01-19 | 2020-06-05 | 中国科学院电子学研究所 | 一种阴极热子组件及其制备方法 |
Families Citing this family (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB2404128B (en) | 2003-07-16 | 2005-08-24 | Kanthal Ltd | Silicon carbide furnace heating elements |
DE102017101946A1 (de) * | 2017-02-01 | 2018-08-02 | Epcos Ag | PTC-Heizer mit verringertem Einschaltstrom |
Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US1814759A (en) * | 1926-02-10 | 1931-07-14 | Frederick S Mccullough | Cathode structure |
US3380936A (en) * | 1965-10-18 | 1968-04-30 | Matsushita Electric Ind Co Ltd | Silicon carbide varistors |
-
1967
- 1967-03-07 NL NL6703548A patent/NL6703548A/xx unknown
-
1968
- 1968-02-06 DE DE19681639354 patent/DE1639354A1/de active Pending
- 1968-02-20 US US706897A patent/US3495120A/en not_active Expired - Lifetime
- 1968-03-04 CH CH315468A patent/CH469351A/de unknown
- 1968-03-04 GB GB00292/68A patent/GB1222887A/en not_active Expired
- 1968-03-05 ES ES351239A patent/ES351239A1/es not_active Expired
- 1968-03-06 FR FR1558677D patent/FR1558677A/fr not_active Expired
Patent Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US1814759A (en) * | 1926-02-10 | 1931-07-14 | Frederick S Mccullough | Cathode structure |
US3380936A (en) * | 1965-10-18 | 1968-04-30 | Matsushita Electric Ind Co Ltd | Silicon carbide varistors |
Cited By (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5118983A (en) * | 1989-03-24 | 1992-06-02 | Mitsubishi Denki Kabushiki Kaisha | Thermionic electron source |
US5475281A (en) * | 1991-02-25 | 1995-12-12 | U.S. Philips Corporation | Cathode |
US20200066474A1 (en) * | 2018-08-22 | 2020-02-27 | Modern Electron, LLC | Cathodes with conformal cathode surfaces, vacuum electronic devices with cathodes with conformal cathode surfaces, and methods of manufacturing the same |
CN111243917A (zh) * | 2020-01-19 | 2020-06-05 | 中国科学院电子学研究所 | 一种阴极热子组件及其制备方法 |
CN111243917B (zh) * | 2020-01-19 | 2021-12-07 | 中国科学院电子学研究所 | 一种阴极热子组件及其制备方法 |
Also Published As
Publication number | Publication date |
---|---|
GB1222887A (en) | 1971-02-17 |
DE1639354A1 (de) | 1970-06-04 |
NL6703548A (ja) | 1968-09-09 |
CH469351A (de) | 1969-02-28 |
ES351239A1 (es) | 1969-06-01 |
FR1558677A (ja) | 1969-02-28 |
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