EP0560436A1 - Cathode à élément solide - Google Patents

Cathode à élément solide Download PDF

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Publication number
EP0560436A1
EP0560436A1 EP93200613A EP93200613A EP0560436A1 EP 0560436 A1 EP0560436 A1 EP 0560436A1 EP 93200613 A EP93200613 A EP 93200613A EP 93200613 A EP93200613 A EP 93200613A EP 0560436 A1 EP0560436 A1 EP 0560436A1
Authority
EP
European Patent Office
Prior art keywords
metallic
range
oxidic
components
cathode according
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.)
Granted
Application number
EP93200613A
Other languages
German (de)
English (en)
Other versions
EP0560436B1 (fr
Inventor
Georg Dr. Gärtner
Hans Dr. Lydtin
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.)
Philips Intellectual Property and Standards GmbH
Koninklijke Philips NV
Original Assignee
Philips Patentverwaltung GmbH
Philips Gloeilampenfabrieken NV
Koninklijke Philips Electronics NV
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 Philips Patentverwaltung GmbH, Philips Gloeilampenfabrieken NV, Koninklijke Philips Electronics NV filed Critical Philips Patentverwaltung GmbH
Publication of EP0560436A1 publication Critical patent/EP0560436A1/fr
Application granted granted Critical
Publication of EP0560436B1 publication Critical patent/EP0560436B1/fr
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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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
    • H01J1/14—Solid thermionic cathodes characterised by the material
    • 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

  • the invention relates to a cathode with a solid element, which contains metallic components and oxidic components.
  • Replenishment cathodes consist of a porous metal matrix with more than 70% metal volume, which ensures good electrical conductivity, as well as an oxide component such as Alkaline earth oxides BaO or CaO or 4BaO.CaO.Al2O3, which is located in the pores of the metal matrix or in a storage area.
  • an oxide component such as Alkaline earth oxides BaO or CaO or 4BaO.CaO.Al2O3, which is located in the pores of the metal matrix or in a storage area.
  • atomic films consisting of the metal (s) (Ba) and atomic oxygen (O) contained in the oxide form on the metal cathode surface (W) and ensure a low work function.
  • Known cathodes of this type are the I cathode (cf. EP-A 0333 369) and the scandate cathode (cf. EP-A 0442 163). Such cathodes have the features mentioned above.
  • Oxide cathodes consist of a relatively thick porous oxide layer made of alkaline earth oxides (for example BaO.SrO) and other oxide dopants (for example Sc2O3, Eu2O3) on a metal support such as nickel. They allow significantly lower operating temperatures of approx. 730 to 850 ° C with emission current densities of 10 to 50A / cm2, but only in the ⁇ sec range. Due to the 50A / cm2, but only in the ⁇ sec range. Due to the low electrical conductivity of the oxide components, the permanent load capacity is limited to 1-3 A / cm2.
  • alkaline earth oxides for example BaO.SrO
  • other oxide dopants for example Sc2O3, Eu2O3
  • the invention has for its object to design a solid element of the type mentioned in such a way that high emission current densities result in a long service life even at low operating temperatures.
  • the solution is achieved in that the structure of the components and the volume ratio v m of the metallic components relative to the total volume of the solid element are chosen such that the specific resistance ⁇ is a value in the range ⁇ O ⁇ 10 ⁇ 4> ⁇ > ⁇ m ⁇ 102 has, where ⁇ O or ⁇ m are the specific resistances of the pure oxidic components or the pure metallic components determined at 20 ° C.
  • the specific electrical resistance ⁇ of a solid-state element according to the invention has a value in the range of the so-called percolation threshold.
  • Cathodes with solid-state elements according to the invention can therefore be referred to as percolation cathodes.
  • the metallic conductivity changes to the oxide conductivity.
  • the specific resistance ⁇ lies between ⁇ O 10 ⁇ 4 and ⁇ m 102, preferably in the range between 103 ⁇ cm and 10 ⁇ 3 ⁇ cm.
  • the specific electrical resistance ⁇ (measured at room temperature) of a solid composed of BaO and W particles of average size 30 nm is represented on a logarithmic scale as a function of the percentage metal volume fraction v m .
  • a metallic conductance behavior is determined in the range v ma ⁇ v m ⁇ V mb of the percolation threshold.
  • the relative volume composition of a solid-state element according to the invention is selected, with volume fractions in the hatched area being particularly favorable for cathodes. For this shaded area, the additional condition is that d4log ⁇ / d V m 4 is positive.
  • the steepness of the characteristic curve P depends to a large extent on the structure of the solid element according to the invention, namely on the size of the metallic and / or oxidic particles and on the homogeneity of their distribution.
  • An advantageous embodiment is characterized in that the oxidic volume fraction is larger than the metallic one.
  • Particles in the sense of the present invention are particles which are formed separately (laser ablation, sputtering of a target) and to a solid element, or grains, which were formed on a substrate by chemical precipitation from the vapor phase (CVD). Furthermore, separately formed further particles can be mixed in between CVD grains (cf. EP-A 0442 163), so that, for example, BaO particles supplied to the substrate via a gas stream are embedded in a tungsten matrix formed on the substrate by CVD.
  • Solid-state elements according to the invention consist of fine and homogeneously mixed structures of individual chemically different types of solid-state elements, a spatial network of metallic particles being nested in a spatial network of oxidic components or vice versa and possibly including tunnel current paths. Furthermore, both the oxidic and the metallic constituents can also be present as particles or grains.
  • Particularly high emission current densities are achieved in that the metallic constituents or the oxidic constituents in the form of particles in the other constituent are distributed so homogeneously that volume ranges of size (20 d ⁇ ) 3 the number of particles differs by less than + -20% from the corresponding volume fraction in the entire solid element, whereby d ⁇ is the average diameter of the particles. Large local agglomerations of particles should be avoided.
  • the solid-state element according to the invention is preferably characterized in that the metallic particles are arranged in such a way that - possibly via tunnel sections - tracks with metallic conductivity through the oxidic braid exist.
  • Heavy-duty cathodes were also obtained in that the average diameter d ⁇ the particle is selected to be smaller than 800 nm, preferably in the range from 0.5 to 100 nm and in particular in the range from 1 to 20 nm.
  • solid-state elements according to the invention can be produced particularly reliably with the desired percolation properties.
  • the solid properties for example electrical resistance
  • the solid properties are sufficiently isotropic when the particles are thoroughly mixed.
  • the specific electrical resistance ⁇ is set in the range from 10 2 to 10 12 ⁇ cm and that the mean diameter d ⁇ the particle is selected in the range from 0.5 to 4 nm.
  • the desired data can be advantageously achieved while at the same time being economically viable in that the diameters d ⁇ the particles are monomodal and have a half-width of ⁇ 50% and the mean d ⁇ have.
  • both the metallic and the oxidic constituents are in the form of particles, the mean diameter d ⁇ 1 the particles of a component less than about 100 nm and the average diameter d ⁇ 2 the body of the particles of the other component is less than 10 times the value d ⁇ 1 are selected, and that the particles of both components are distributed so homogeneously that in a volume range of size (20 d ⁇ 2) 3 the number of particles of each component deviate by less than ⁇ 20% from the corresponding volume fraction in the entire solid element.
  • Percolation cathodes constructed with solid-state elements according to the invention can be subjected to higher loads than oxide cathodes, lower operating temperatures being required than with subsequent delivery cathodes.
  • Solid-state elements according to the invention require only relatively low operating temperatures in the range from 730 to 850 ° C. Since neither a high-temperature impregnation step at temperatures of more than 1500 ° C. nor a longer activation at temperatures of about 1100 ° C. are necessary, the structure of a solid-state element structured according to the invention remains largely stable, even when components are used whose solid solubility in one another is not negligible is.
  • a solid-state element according to the invention can be heated by direct current passage.
  • Such a solution is advantageously characterized in that the proportions and / or the particle sizes of the oxidic (negative temperature coefficient) and / or metallic (positive temperature coefficient) components are selected such that the specific resistance in the range from room temperature to operating temperature is less than 5 %, preferably 1%, changes.
  • This has the advantage that when the solid-state element is heated directly, the heating current and voltage do not have to be readjusted, or only slightly, when heating up to a certain operating temperature.
  • Solid-state elements according to the invention can be produced in any known manner. For example, suitable processes are described in EP-A 0442 163 or in EP-A 0333 369.
  • a solid-state element according to the invention are not only achieved with a compact and 100% leakproof construction.
  • a porosity of up to about 20% is even advantageous because it facilitates the subsequent delivery of the emitting film components to the surface.
  • the electrical conductivity is nevertheless only insignificantly determined by electron gas conduction, but almost exclusively by the percolation structure.
  • the percolation cathode indicated in cross section in FIG. 1 consists of a tungsten heating coil 1, a molybdenum heating cap 2, a metal base 3 made of tungsten or nickel and a solid element 4 structured according to the invention, the specific electrical resistance ⁇ of which in the area of the percolation threshold on the characteristic branch P.
  • Figure 2 lies.
  • a volume element of the solid element 4 is shown greatly enlarged in cross section in FIG.
  • the metallic particles 5 consist of tungsten (28 vol.%).
  • the oxide particles 6 (closely hatched) consist of scandium oxide Sc2O3 (2 vol.%), while the oxidic particles 7 (not hatched) consist of barium oxide / strontium oxide (BaO / SrO) with a share of 60 vol.% Of the total volume.
  • pulse emission current densities of more than 160A / cm2 and permanent loads of 20A / cm2 were measured.
  • the specified values for permanent load capacity apply for a service life of more than 104 hours.
  • Similar good values were achieved with a modified pore-free structure according to FIG. 4, in which otherwise the same proportions for the constituents W, Sc2O3 or BaO / SrO were provided as for the structure according to FIG. 3.
  • W and Sc2O3 are particles 8 or 9 with an average diameter of 10 nm embedded in a solid matrix 10 of BaO / SrO.

Landscapes

  • Solid Thermionic Cathode (AREA)
EP93200613A 1992-03-07 1993-03-04 Cathode à élément solide Expired - Lifetime EP0560436B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE4207220 1992-03-07
DE4207220A DE4207220A1 (de) 1992-03-07 1992-03-07 Festkoerperelement fuer eine thermionische kathode

Publications (2)

Publication Number Publication Date
EP0560436A1 true EP0560436A1 (fr) 1993-09-15
EP0560436B1 EP0560436B1 (fr) 1995-07-26

Family

ID=6453449

Family Applications (1)

Application Number Title Priority Date Filing Date
EP93200613A Expired - Lifetime EP0560436B1 (fr) 1992-03-07 1993-03-04 Cathode à élément solide

Country Status (4)

Country Link
US (1) US5592043A (fr)
EP (1) EP0560436B1 (fr)
JP (1) JPH0628968A (fr)
DE (2) DE4207220A1 (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2308495A (en) * 1995-12-20 1997-06-25 Lg Electronics Inc Cathodes
US7138754B2 (en) 2002-03-21 2006-11-21 Samsung Sdi Co., Ltd. Cathode for electron tube and method for manufacturing the same

Families Citing this family (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4400353A1 (de) * 1994-01-08 1995-07-13 Philips Patentverwaltung Steuerbarer thermionischer Elektronenemitter
JPH0850849A (ja) * 1994-05-31 1996-02-20 Nec Kansai Ltd 陰極部材およびそれを用いた電子管
DE4421793A1 (de) * 1994-06-22 1996-01-04 Siemens Ag Thermionischer Elektronenemitter für eine Elektronenröhre
US6051165A (en) * 1997-09-08 2000-04-18 Integrated Thermal Sciences Inc. Electron emission materials and components
US6140753A (en) * 1997-12-30 2000-10-31 Samsung Display Devices Co., Ltd. Cathode for an electron gun
KR100249714B1 (ko) * 1997-12-30 2000-03-15 손욱 전자총용 음극
FR2810446A1 (fr) * 2000-06-14 2001-12-21 Thomson Tubes & Displays Cathodes a oxyde amelioree et son procede de fabrication
WO2002025681A1 (fr) * 2000-09-19 2002-03-28 Koninklijke Philips Electronics N.V. Tube cathodique a cathode a oxyde
KR100393047B1 (ko) * 2001-03-14 2003-07-31 삼성에스디아이 주식회사 금속 음극 및 이를 구비한 방열형 음극구조체
US20020195919A1 (en) * 2001-06-22 2002-12-26 Choi Jong-Seo Cathode for electron tube and method of preparing the cathode
KR20030047054A (ko) * 2001-12-07 2003-06-18 삼성에스디아이 주식회사 전자관용 금속 음극 및 그 제조방법
WO2007033247A2 (fr) 2005-09-14 2007-03-22 Littelfuse, Inc. Limiteur de surtension rempli de gaz, compose d'activation, rubans d'amorçage et procede associe
DE102008020187A1 (de) * 2008-04-22 2009-10-29 Siemens Aktiengesellschaft Kathode mit einem Flachemitter
US8578543B2 (en) 2011-04-21 2013-11-12 The Procter & Gamble Company Squeegee having at least one renewable blade surface for treating a target surface
US8495784B2 (en) 2011-04-21 2013-07-30 The Procter & Gamble Company Device having dual renewable blades for treating a target surface and replaceable cartridge therefor

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US4369392A (en) * 1979-09-20 1983-01-18 Matsushita Electric Industrial Co., Ltd. Oxide-coated cathode and method of producing the same
EP0333369A1 (fr) * 1988-03-18 1989-09-20 Varian Associates, Inc. Cathode matricielle en solution solide

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JPS5566819A (en) * 1978-11-15 1980-05-20 Hitachi Ltd Oxide cathode for electron tube
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Cited By (3)

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Publication number Priority date Publication date Assignee Title
GB2308495A (en) * 1995-12-20 1997-06-25 Lg Electronics Inc Cathodes
GB2308495B (en) * 1995-12-20 2000-08-30 Lg Electronics Inc A Cathode structure body and a method of coating an emitter
US7138754B2 (en) 2002-03-21 2006-11-21 Samsung Sdi Co., Ltd. Cathode for electron tube and method for manufacturing the same

Also Published As

Publication number Publication date
JPH0628968A (ja) 1994-02-04
DE59300389D1 (de) 1995-08-31
DE4207220A1 (de) 1993-09-09
EP0560436B1 (fr) 1995-07-26
US5592043A (en) 1997-01-07

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