US3833494A - Method of manufacturing a lanthanum hexaboride-activated cathode for an electric discharge tube - Google Patents

Method of manufacturing a lanthanum hexaboride-activated cathode for an electric discharge tube Download PDF

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US3833494A
US3833494A US00356620A US35662073A US3833494A US 3833494 A US3833494 A US 3833494A US 00356620 A US00356620 A US 00356620A US 35662073 A US35662073 A US 35662073A US 3833494 A US3833494 A US 3833494A
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lanthanum hexaboride
manufacturing
electric discharge
discharge tube
layer
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US00356620A
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Stratum A Van
N Mitra
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US Philips Corp
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US Philips Corp
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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

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  • the invention relates to a method of manufacturing a cathode for an electric discharge tube in which a layer of lanthanum hexaboride is cataphoretically provided on a rhenium support and is sintered.
  • the invention furthermore relates to a cathode manufactured in this manner.
  • the cataphoretically provided layer is slowly heated to a temperature of l,500 to l,550C and maintained at said final temperature for maximum 30 seconds until a smooth and shining surface is obtained, after which a second layer of lanthanum hexaboride is cataphoretically provided and also heated to a temperature of 1,500 to l,550C and maintained at said temperature for maximum 2 minutes.
  • a layer of rhenium boride is formed all over the surface of the rhenium wire and rhenium wire as a result of excessive boride formation ing example.
  • 1 denotes a part of a hard glass bottom in which two wires 2 and 3 of an iron-nickel-cobalt alloy are present.
  • a rhenium wire 4 of 0.18 mm diameter is welded to the lead-in wires 2 and 3. After firing the rhenium wire in hydrogen gas at 1,600C for 2 minutes, it is covered from a lanthanum boride suspension (unpurified LaB with a 50 p. thick layer. Said layer is heated for 5 minutes and sintered in hydrogen at 1,530C for 15 seconds. The layer becomes smooth and shining. A 20 microns thick layer of lanthanum hexaboride is then cataphoretically provided, said layer being sintered in hydrogen at l,550C for 2 minutes.
  • the cathode After sealing the bottom 1 in a tube and after evacuation thereof, the cathode is degassed at 1,600C for a few seconds. The cathode is then activated at 1,500C for 5 to 30 minutes.
  • the saturation emission (measured with pulses) is 10 Alcm
  • the life at said temperature is more than 8,000 hours.
  • the cathodes according to the invention are suitable for use in high voltage apparatus such as X-ray tubes, rectifier tubes and also in electron beam welding apparatus, electron microscopes and the like, in which comparatively poor vacuum conditions occur and which cathodes are exposed to air repeated times.
  • high voltage apparatus such as X-ray tubes, rectifier tubes and also in electron beam welding apparatus, electron microscopes and the like, in which comparatively poor vacuum conditions occur and which cathodes are exposed to air repeated times.
  • said cathodes are also suitable.
  • a method of manufacturing a cathode for an electric discharge tube in which a layer of lanthanum hexaboride is cataphoretically provided on a rhenium support and sintered characterized in that the cataphoretically provided layer is slowly heated to a temperature of l,500 to l,550C and maintained at said final temperature formaximum 30 seconds until a smooth and shining surface is obtained, after which a second layer of lanthanum hexaboride is cataphoretically provided and also heated to a temperature of l,500 to l,550C and maintained at said temperature for maximum 2 minutes.

Abstract

A layer of lanthanum hexaboride is applied cataphoretically to a rhenium wire and then sintered. The process is repeated. In this manner a cathode with small evaporation and long life is obtained.

Description

Unite States Patent [1 1 Van Stratum et al.
[111 3,833,494 14 1 Sept. 3, 1974 METHOD OF MANUFACTURING A LANTHANUM HEXABORIDE-ACTIVATED CATHODE FOR AN ELECTRIC DISCHARGE TUBE [75] Inventors: Antonius Johannes Alberta Van I Stratum, Emmasingel, Eindhoven; Nira'njan Kumar Mitra, Best, both of Netherlands [73] Assignee: U. S. Philips Corporation, New
York, NY.
[22] Filed: May 2, 1973 211 App]. No.: 356,620
[30] Foreign Application Priority Data May 30, 1972 Netherlands 7207275 [52] US. Cl. 204/181, 313/346 R [51] Int. Cl C231! 13/00 [58] Field of Search 204/181; 313/346 R L. Favreau, Cataphoretic Coating Lanthanum Boride on Rhenium Filaments, Rev. Sci. In'st., Vol. 36, pages 856-857, (1965). I
Primary Examiner-John l-l. Mack Assistant Examiner-Aaron Weisstuch Attorney, Agent, or Firm-Frank R. Trifari; Carl P.
' Steinhauser [5 7 ABSTRACT A layer of lanthanum hexaboride is applied cataphoretically to a rhenium wire and then sintered. The process is repeated. In this manner a cathode with small evaporation and long life is obtained.
1 Claim, l Drawing Figure METHOD OF MANUFACTURING A LANTI-IANUM I-IEXABORIDE-ACTIVATED CATHODE FOR AN ELECTRIC DISCHARGE TUBE The invention relates to a method of manufacturing a cathode for an electric discharge tube in which a layer of lanthanum hexaboride is cataphoretically provided on a rhenium support and is sintered. The invention furthermore relates to a cathode manufactured in this manner.
The method described above is known from Rev.Sci. Inst. 36, 856-7, 1965.
It is found in practice that lives of only approximately 1,000 hours are obtained with such cathodes. The rhenium wire on which the lanthanum hexaboride is sintered then usually breaks. If the boride is not yet very pure, that is to say free from free boron and boron oxide, the life is still considerably shorter. This'is the result of the fact that in the presence of the said contaminations borides of rhenium are formed in an uncontrol- 20 lable manner. The reaction between the rhenium and the lanthanum hexaborideis then subject to considerable fluctuations and the operation of the cathodejis not satisfactory. Should lanthanum tetraboride also be present in the lanthanum hexaboride, a considerable evaporation of lanthanum occurs because the tetrabo ride first decomposes to hexaboride rather rapidly. The hexaboride reacts slowly with the rhenium and evaporates only slowly. Perhaps the lanthanum released from the tetraboride could'also react with the rhenium.
It is the object of the invention to provide a method by which cathodes of the indicated composition can be obtained with a long life.
According to the invention, in a method of manufacturing a cathode for an electric discharge tube in which a layer of lanthanum hexaboride is cataphoretically provided on a rhenium support and is sintered, the cataphoretically provided layer is slowly heated to a temperature of l,500 to l,550C and maintained at said final temperature for maximum 30 seconds until a smooth and shining surface is obtained, after which a second layer of lanthanum hexaboride is cataphoretically provided and also heated to a temperature of 1,500 to l,550C and maintained at said temperature for maximum 2 minutes.
Upon heating the first layer of hexaboride which need not be very pure, a layer of rhenium boride is formed all over the surface of the rhenium wire and rhenium wire as a result of excessive boride formation ing example.
is prevented and a long life of many thousands of hours can be achieved. At the normal operating temperature of the lanthanum hexaboride cathodes, good emission densities are achieved. If the second layer contains no lanthanum tetraboride, littleevaporation occurs.
The invention will be described in greater detail, also with reference to the FIGURE, by means of the follow- In the FIGURE, 1 denotes a part of a hard glass bottom in which two wires 2 and 3 of an iron-nickel-cobalt alloy are present.
A rhenium wire 4 of 0.18 mm diameter is welded to the lead-in wires 2 and 3. After firing the rhenium wire in hydrogen gas at 1,600C for 2 minutes, it is covered from a lanthanum boride suspension (unpurified LaB with a 50 p. thick layer. Said layer is heated for 5 minutes and sintered in hydrogen at 1,530C for 15 seconds. The layer becomes smooth and shining. A 20 microns thick layer of lanthanum hexaboride is then cataphoretically provided, said layer being sintered in hydrogen at l,550C for 2 minutes.
After sealing the bottom 1 in a tube and after evacuation thereof, the cathode is degassed at 1,600C for a few seconds. The cathode is then activated at 1,500C for 5 to 30 minutes.
At a temperature of l,400C the saturation emission (measured with pulses) is 10 Alcm The life at said temperature is more than 8,000 hours.
Like all the hexaboridecathodes, the cathodes according to the invention are suitable for use in high voltage apparatus such as X-ray tubes, rectifier tubes and also in electron beam welding apparatus, electron microscopes and the like, in which comparatively poor vacuum conditions occur and which cathodes are exposed to air repeated times. In apparatus in which layers have to be locally activated by means of electron beams or be worked differently, said cathodes are also suitable.
What is claimed is:
1. A method of manufacturing a cathode for an electric discharge tube in which a layer of lanthanum hexaboride is cataphoretically provided on a rhenium support and sintered, characterized in that the cataphoretically provided layer is slowly heated to a temperature of l,500 to l,550C and maintained at said final temperature formaximum 30 seconds until a smooth and shining surface is obtained, after which a second layer of lanthanum hexaboride is cataphoretically provided and also heated to a temperature of l,500 to l,550C and maintained at said temperature for maximum 2 minutes.
US00356620A 1972-05-30 1973-05-02 Method of manufacturing a lanthanum hexaboride-activated cathode for an electric discharge tube Expired - Lifetime US3833494A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
NL7207275A NL167796C (en) 1972-05-30 1972-05-30 METHOD FOR MANUFACTURING A LANTHANE HEXABORIDE-ACTIVATED CATHOD FOR AN ELECTRIC DISCHARGE TUBE

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JP (1) JPS5524224B2 (en)
CA (1) CA994280A (en)
CH (1) CH574677A5 (en)
DE (1) DE2325273C3 (en)
FR (1) FR2186725B1 (en)
GB (1) GB1378620A (en)
NL (1) NL167796C (en)
SE (1) SE382886B (en)

Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5128475A (en) * 1974-09-04 1976-03-10 Hitachi Ltd MAGUNETORONINKYOKUKOTAI
JPS51118362A (en) * 1975-04-10 1976-10-18 Natl Inst For Res In Inorg Mater Heat electon radiating cathode
JPS5231651A (en) * 1975-09-04 1977-03-10 Natl Inst For Res In Inorg Mater Scan-type electron microscope
JPS5231652A (en) * 1975-09-04 1977-03-10 Natl Inst For Res In Inorg Mater Electron microscope
US4019081A (en) * 1974-10-25 1977-04-19 Bbc Brown Boveri & Company Limited Reaction cathode
US4054946A (en) * 1976-09-28 1977-10-18 Bell Telephone Laboratories, Incorporated Electron source of a single crystal of lanthanum hexaboride emitting surface of (110) crystal plane
US4055780A (en) * 1975-04-10 1977-10-25 National Institute For Researches In Inorganic Materials Thermionic emission cathode having a tip of a single crystal of lanthanum hexaboride
US4482839A (en) * 1981-05-29 1984-11-13 Denki Kagaku Kogyo Kabushiki Kaisha Thermionic emission cathode and preparation thereof
US5142652A (en) * 1990-08-20 1992-08-25 Siemens Aktiengesellschaft X-ray arrangement comprising an x-ray radiator having an elongated cathode
US5170422A (en) * 1990-08-20 1992-12-08 Siemens Aktiengesellschaft Electron emitter for an x-ray tube
EP1983546A1 (en) * 2007-04-20 2008-10-22 PANalytical B.V. X-ray cathode and tube
US20100301736A1 (en) * 2007-11-30 2010-12-02 Toshiyuki Morishita Electron emitting source and manufacturing method of electron emitting source
US20150002009A1 (en) * 2012-07-03 2015-01-01 National Institute For Materials Science Metal hexaboride cold field emitter, method of fabricating same, and electron gun

Families Citing this family (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2117795A (en) * 1982-04-06 1983-10-19 Standard Telephones Cables Ltd Fabricating capacitors; forming ceramic films
GB8611967D0 (en) * 1986-05-16 1986-10-29 English Electric Valve Co Ltd Directly heated cathodes
JPS6489242A (en) * 1987-09-30 1989-04-03 Mitsubishi Electric Corp Electrode for discharge light source
DE4026298A1 (en) * 1990-08-20 1992-02-27 Siemens Ag Long life X=ray tube - has electron emitter based on rare earth material alloy
DE4026300A1 (en) * 1990-08-20 1992-02-27 Siemens Ag Electron emitter for X=ray tube - is of material contg. rare earth element covering support layer of large flat surface withstanding vibration
DE4026297A1 (en) * 1990-08-20 1992-02-27 Siemens Ag X=ray tube system - has heater for cathode contg. lanthanum material as electron emitter
DE10245392B3 (en) * 2002-09-28 2004-01-08 Vtd Vakuumtechnik Dresden Gmbh Tubular hollow cathode for high electrical outputs
CN104223613B (en) 2014-09-26 2016-09-28 京东方科技集团股份有限公司 Intelligent bracelet display control program and Intelligent bracelet

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3312856A (en) * 1963-03-26 1967-04-04 Gen Electric Rhenium supported metallic boride cathode emitters
US3498897A (en) * 1967-07-25 1970-03-03 Ford Motor Co Method for manufacturing multilayered product
US3630770A (en) * 1969-04-30 1971-12-28 Gen Electric Method for fabricating lanthanum boride cathodes

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3312856A (en) * 1963-03-26 1967-04-04 Gen Electric Rhenium supported metallic boride cathode emitters
US3498897A (en) * 1967-07-25 1970-03-03 Ford Motor Co Method for manufacturing multilayered product
US3630770A (en) * 1969-04-30 1971-12-28 Gen Electric Method for fabricating lanthanum boride cathodes

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
L. Favreau, Cataphoretic Coating Lanthanum Boride on Rhenium Filaments, Rev. Sci. Inst., Vol. 36, pages 856 857, (1965). *

Cited By (16)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5128475A (en) * 1974-09-04 1976-03-10 Hitachi Ltd MAGUNETORONINKYOKUKOTAI
US4019081A (en) * 1974-10-25 1977-04-19 Bbc Brown Boveri & Company Limited Reaction cathode
JPS6040133B2 (en) * 1975-04-10 1985-09-09 科学技術庁無機材質研究所長 Manufacturing method of cathode for thermionic emission
US4055780A (en) * 1975-04-10 1977-10-25 National Institute For Researches In Inorganic Materials Thermionic emission cathode having a tip of a single crystal of lanthanum hexaboride
JPS51118362A (en) * 1975-04-10 1976-10-18 Natl Inst For Res In Inorg Mater Heat electon radiating cathode
JPS5231652A (en) * 1975-09-04 1977-03-10 Natl Inst For Res In Inorg Mater Electron microscope
JPS5231651A (en) * 1975-09-04 1977-03-10 Natl Inst For Res In Inorg Mater Scan-type electron microscope
US4054946A (en) * 1976-09-28 1977-10-18 Bell Telephone Laboratories, Incorporated Electron source of a single crystal of lanthanum hexaboride emitting surface of (110) crystal plane
US4482839A (en) * 1981-05-29 1984-11-13 Denki Kagaku Kogyo Kabushiki Kaisha Thermionic emission cathode and preparation thereof
US5142652A (en) * 1990-08-20 1992-08-25 Siemens Aktiengesellschaft X-ray arrangement comprising an x-ray radiator having an elongated cathode
US5170422A (en) * 1990-08-20 1992-12-08 Siemens Aktiengesellschaft Electron emitter for an x-ray tube
EP1983546A1 (en) * 2007-04-20 2008-10-22 PANalytical B.V. X-ray cathode and tube
US20100301736A1 (en) * 2007-11-30 2010-12-02 Toshiyuki Morishita Electron emitting source and manufacturing method of electron emitting source
US8456076B2 (en) * 2007-11-30 2013-06-04 Denki Kagaku Kogyo Kabushiki Kaisha Electron emitting source and manufacturing method of electron emitting source
US20150002009A1 (en) * 2012-07-03 2015-01-01 National Institute For Materials Science Metal hexaboride cold field emitter, method of fabricating same, and electron gun
US8952605B2 (en) * 2012-07-03 2015-02-10 National Institute For Materials Science Metal hexaboride cold field emitter, method of fabricating same, and electron gun

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JPS5524224B2 (en) 1980-06-27
FR2186725B1 (en) 1976-09-17
NL7207275A (en) 1973-12-04
CH574677A5 (en) 1976-04-15
SE382886B (en) 1976-02-16
DE2325273A1 (en) 1973-12-13
JPS4944661A (en) 1974-04-26
CA994280A (en) 1976-08-03
NL167796C (en) 1982-01-18
NL167796B (en) 1981-08-17
DE2325273B2 (en) 1980-09-04
DE2325273C3 (en) 1981-07-09
GB1378620A (en) 1974-12-27
FR2186725A1 (en) 1974-01-11

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