US3458749A - Dispenser cathode made of tungsten powder having a grain size of less than three microns - Google Patents

Dispenser cathode made of tungsten powder having a grain size of less than three microns Download PDF

Info

Publication number
US3458749A
US3458749A US644003A US3458749DA US3458749A US 3458749 A US3458749 A US 3458749A US 644003 A US644003 A US 644003A US 3458749D A US3458749D A US 3458749DA US 3458749 A US3458749 A US 3458749A
Authority
US
United States
Prior art keywords
mixture
cathode
tungsten
less
grain size
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
US644003A
Other languages
English (en)
Inventor
Antonius Johannes Albe Stratum
Franciscus Johannes Verest
Hans Henkes
Pieter Zalm
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.)
US Philips Corp
Original Assignee
US Philips Corp
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 US Philips Corp filed Critical US Philips Corp
Application granted granted Critical
Publication of US3458749A publication Critical patent/US3458749A/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
    • H01J1/28—Dispenser-type cathodes, e.g. L-cathode

Definitions

  • pressed dispenser cathodes may be manufactured from a mixture of powdery tungsten and powdery tribariumaluminate, which preferably contains, in addition, calcium oxide, pressed by a high pressure (11,000 kg./cm. into a cathode body, and heated in vacuum or in a hydrogen atmosphere at 1800 to 1900 C. at which the aluminate melts and the gases are expelled from the cathode. Owing to the use of aluminates the cathode can be preserved in air only to a restricted extent.
  • cathodes exhibited a high rate of barium evaporation and had a short lifetime.
  • the active metal in this cathode was tungsten.
  • An alloy of tungsten and molybdenum was used afterwards for reducing the evaporation of barium from the cathode. It appeared to be necessary to use an alloy of about 75% of Mo and 25% of W, but this reduced the emission as compared with the use of pure tungsten powder.
  • the metal powders employed were mixtures of grains having a size lying between about 4 and 1212.
  • the electron emission obtained is equivalent to that of the so-called L-cathode, in which the active barium oxide is accommodated in a cavity beneath a porous tungsten body.
  • An advantage of the inventive cathode is that degassing and activation thereof takes considerably less time than in the case of an L-cathode.
  • the pressure of 25,000 l g./cm. required for compressing a cathode according to the invention is more than twice ice that required for the known pressed cathodes using tungsten powders of a grain size lying between 4 and 12;/., but technically this involves no particular difliculties. The higher the pressure, the less the evaporation. Pressures below 20,000 kg./cm. are unsuitable because the Ba evaporation becomes too high.
  • the cathode according to the invention has the same properties as the L-cathode, owing to the absence of molybdenum, but it can be manufactured at much lower cost.
  • the cathode shown comprises a pressed emissive body 1, accommodated in a cylindrical molybdenum foil 2.
  • the cylinder 2 is provided with strips 3 for securing same in the electrode system of the usual electron t-ube, e.g., a cathode-ray tube.
  • the cylinder 2 accommodates a heating element 4 and a partition 5 of molybdenum in order to avoid emission from the body 1 to the heater 4.
  • the body 1 consists of a powdery coprecipitated mixture of barium carbonate, calcium carbonate, and aluminum oxide in a molecular ratio of 5:312 (SBaCO 3CaCO 2Al O nH O), and tungsten powder having a grain size of less than 0.5 ,u.
  • Such fine tungsten powder cannot be obtained by grinding, but is obtainable for example by the reduction of gaseous tungsten chloride (WCI with hydrogen, which is known as such.
  • WCI with hydrogen gaseous tungsten chloride
  • the mixture contains furthermore a small supply of carbon, preferably in the form of a soluble carbon compound such as sugar (C H O since this ensures a homogeneous distribution of the carbon in the mixture.
  • the ratio in weight of the powder mixture to be compressed is: 93% of tungsten, 6.8% of coprecipitated barium-calcium-aluminate compound, and 0.2% of sugar.
  • the mixture is introduced into a mold comprising the molybdenum cylinder 2 and the partition 5 and it is compressed with a pressure of 25,000 kg./cm. while the upper rim of the cylinder 2 is slightly pressed inwardly, so that the cathode body 1 is firmly held in place. Then the supporting strips 3 are welded to the cylinder 2 and the heating body 4 is slipped into it.
  • the body 1 may be compressed to form a pellet which is subsequently fastened in a holder.
  • a representative example of one manufacturing method is as follows:
  • a thermionic dispenser cathode comprising a pressed and sintered mixture of barium-calcium aluminate powder and tungsten powder, said tungsten powder having a maximum grain size of less than 3 microns, said aluminate being formed in the pressed cathode-body by conversion of coprecipitated barium carbonate, calcium carbonate and aluminum oxide in a hydrogen atmosphere.
  • a cathode as set forth in claim 2 wherein the coprecipitated mixture comprises barium oxide, calcium oxide and aluminum oxide in a mole ratio of about 523:2.
  • a method of manufacturing a pressed tungsten dispenser cathode comprising the steps of coprecipitating barium carbonate, calcium carbonate, and aluminum oxide to form a homogeneous mixture thereof, drying the mixture, adding a solution of a carbon containing compound thereto to form a slurry, drying the carboncontaining slurry and grinding the resulting carbon-containing mixture, mixing said mixture with fine tungsten powder having a maximum grain size below 3 microns, subjecting the mixture to a pressing operation at a pressure of at least 25,000 kg./cm. and then heating the mixture to remove gases, to convert the coprecipitated mixture into aluminuates and to sinter the mixture.

Landscapes

  • Solid Thermionic Cathode (AREA)
  • Powder Metallurgy (AREA)
US644003A 1966-06-24 1967-06-06 Dispenser cathode made of tungsten powder having a grain size of less than three microns Expired - Lifetime US3458749A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
NL6608782A NL6608782A (en, 2012) 1966-06-24 1966-06-24

Publications (1)

Publication Number Publication Date
US3458749A true US3458749A (en) 1969-07-29

Family

ID=19796967

Family Applications (1)

Application Number Title Priority Date Filing Date
US644003A Expired - Lifetime US3458749A (en) 1966-06-24 1967-06-06 Dispenser cathode made of tungsten powder having a grain size of less than three microns

Country Status (8)

Country Link
US (1) US3458749A (en, 2012)
AT (1) AT270820B (en, 2012)
BE (1) BE700464A (en, 2012)
CH (1) CH489111A (en, 2012)
ES (2) ES342176A1 (en, 2012)
GB (1) GB1131586A (en, 2012)
NL (1) NL6608782A (en, 2012)
SE (1) SE318031B (en, 2012)

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3534455A (en) * 1968-05-03 1970-10-20 Us Army Method of making thermionic cathodes
US3656020A (en) * 1970-11-18 1972-04-11 Spectra Mat Inc Thermionic cathode comprising mixture of barium oxide, calcium oxide and lithium oxide
US3760218A (en) * 1972-04-10 1973-09-18 Spectramat Inc Thermionic cathode
JPS5046058U (en, 2012) * 1973-08-27 1975-05-08
JPS5150955U (en, 2012) * 1974-10-16 1976-04-17
WO1989009480A1 (en) * 1988-03-28 1989-10-05 Hughes Aircraft Company Expandable dispenser cathode
US5092805A (en) * 1988-11-11 1992-03-03 Samsung Electron Devices Co., Ltd. Manufacturing method for dispenser code
US20050047801A1 (en) * 2003-08-27 2005-03-03 Karl Schrodinger Optical receiver circuit

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR930014673A (ko) * 1991-12-20 1993-07-23 김정배 함침형 음극 구조체 및 그 제조방법

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2912611A (en) * 1953-08-14 1959-11-10 Int Standard Electric Corp Thermionic cathodes
US2975320A (en) * 1958-12-03 1961-03-14 Rca Corp Low-temperature plasma source
US3076916A (en) * 1959-01-21 1963-02-05 Semicon Associates Inc Impregnated tungsten cathode structures and methods for fabricating same

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2912611A (en) * 1953-08-14 1959-11-10 Int Standard Electric Corp Thermionic cathodes
US2975320A (en) * 1958-12-03 1961-03-14 Rca Corp Low-temperature plasma source
US3076916A (en) * 1959-01-21 1963-02-05 Semicon Associates Inc Impregnated tungsten cathode structures and methods for fabricating same

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3534455A (en) * 1968-05-03 1970-10-20 Us Army Method of making thermionic cathodes
US3656020A (en) * 1970-11-18 1972-04-11 Spectra Mat Inc Thermionic cathode comprising mixture of barium oxide, calcium oxide and lithium oxide
US3760218A (en) * 1972-04-10 1973-09-18 Spectramat Inc Thermionic cathode
JPS5046058U (en, 2012) * 1973-08-27 1975-05-08
JPS5150955U (en, 2012) * 1974-10-16 1976-04-17
WO1989009480A1 (en) * 1988-03-28 1989-10-05 Hughes Aircraft Company Expandable dispenser cathode
US5092805A (en) * 1988-11-11 1992-03-03 Samsung Electron Devices Co., Ltd. Manufacturing method for dispenser code
US20050047801A1 (en) * 2003-08-27 2005-03-03 Karl Schrodinger Optical receiver circuit

Also Published As

Publication number Publication date
BE700464A (en, 2012) 1967-12-27
CH489111A (de) 1970-04-15
NL6608782A (en, 2012) 1967-12-27
DE1614256B2 (de) 1975-09-11
AT270820B (de) 1969-05-12
ES342176A1 (es) 1968-10-01
SE318031B (en, 2012) 1969-12-01
ES353888A1 (es) 1969-10-01
DE1614256A1 (de) 1970-05-27
GB1131586A (en) 1968-10-23

Similar Documents

Publication Publication Date Title
US2700118A (en) Incandescible cathode
US4594220A (en) Method of manufacturing a scandate dispenser cathode and dispenser cathode manufactured by means of the method
US3458749A (en) Dispenser cathode made of tungsten powder having a grain size of less than three microns
US3582702A (en) Thermionic electron-emissive electrode with a gas-binding material
US4083811A (en) Lanthanated thermionic cathodes
US2716716A (en) Cathode containing a supply of an electron-emissive material
US2173259A (en) Active metal compounds for vacuum tubes
US2173258A (en) Active metal compound for vacuum tubes
US3148056A (en) Cathode
JPS6191822A (ja) スカンジウムを含むデイスペンサ陰極の製造方法及びそれで作られたスカンジウムを含むデイスペンサ陰極
JPH02186525A (ja) 貯蔵形ディスペンサー陰極及びその製造方法
US2929133A (en) Dispenser cathode
US2914402A (en) Method of making sintered cathodes
EP0390269B1 (en) Scandate cathode
Coppola et al. A new pressed dispenser cathode
US2175696A (en) Electron emitter
US2917415A (en) Method of making thermionic dispenser cathode and cathode made by said method
JPH0765694A (ja) 電子管用の陰極
US3088851A (en) Method of manufacturing oxide cathodes and cathodes manufactured by such methods
US3201639A (en) Thermionic dispenser cathode
US3269804A (en) Dispenser cathode and method for the production thereof
US5982083A (en) Cathode for electron tube
US1552310A (en) Electrode for discharge tubes
US2737607A (en) Incandescible cathode
US3688150A (en) Degassing arrangement for electron beam tube including an mk dispenser cathode