US3113236A - Oxide dispenser type cathode - Google Patents

Oxide dispenser type cathode Download PDF

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Publication number
US3113236A
US3113236A US36827A US3682760A US3113236A US 3113236 A US3113236 A US 3113236A US 36827 A US36827 A US 36827A US 3682760 A US3682760 A US 3682760A US 3113236 A US3113236 A US 3113236A
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United States
Prior art keywords
layer
barium
cathode
nickel
oxide
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Expired - Lifetime
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US36827A
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English (en)
Inventor
Lemmens Hendrikus Johannes
Zalm Pieter
Antonius Johannes Albe Stratum
Blatter Johannes Reinier
Almer Friedrich Herman Raymund
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US Philips Corp
North American Philips Co Inc
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US Philips Corp
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    • 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

  • This invention relates to cathodes -for electron devices or electric discharge tubes.
  • it relates to a thermionic, oxide, dispenser-type cathode, in which a non-metallic emissive layer activated by barium is separated from a source or layer dispensing barium by means of a permeable metal layer.
  • a known cathode comprises an electron emissive layer which consists of alkaline-earth oxides sprayed onto a porous ⁇ metal layer having beneath it a layer of bariumaluminum which contains a metal binding the aluminum and which in turn is supported by a carrier of, for example, ceramic material.
  • the barium-aluminum dispenses barium at a comparatively high vapo-r pressure, which diffuses through the porous metal layer into the alkaline-earth oxide layer. The evaporation of barium from such a cathode will be considerable.
  • cathode is made by spraying onto a support a mixture of carbonyl nickel powder, bariumstrontium carbonatos and zirconium hydride as a reducing agent. The layer is pressed under high pressure and sintered. Since the layer contains a high percentage of nickel powder, the cathode has a metallic appearance and its emission density is lower than that of ordinary oxide cathodes.
  • the chief object of the invention is to provide a cathode capable of high continuous emission densities at relatively low operating temperatures and possessing low evaporation of active material.
  • the cathode comprises a non-metallic emissive layer activated by barium, and possibly strontium, separated ⁇ from a layer or source dispensing the alkaline-earth metal by a metal layer permeable to said alkaline-earth metal.
  • the permeable metal layer constitutes the current supply means or conductor for the activated layer and is of a composition such that this metal layer, together with the non-metallic activated layer, substantially does not form any insulating interfaces.
  • the layer or supply ydispensing the alkaline-earth metal consists of alkaline-earth metal compounds from which tree alkaline-earth metal is produced or generated by a metal surrounding it or contained in it.
  • a simple embodiment of a cathode according to the invention comprises a layer of barium-strontium oxide provided on a sprayed layer of inactive or passive nickel powder having beneath it a layer of barium-strontium oxide on a support of active nickel, which serve as the dispensing source, the nickel powder layer making electric contact with the active nickel support.
  • active and inactive or passive nickel is to be understood herein to mean nickel containing or substantially not containing respectively reducing impurities such as aluminum, silicon, tungsten, or magnesium, which function to -free by a reducing process barium from bariumstrontium oxide.
  • active nickel contains an irnpurity content exceeding, in weight percent, 0.01% of aluminum or 0.5% of tungsten or 0.01% of silicon or 0.01% of magnesium, or combinations of these impurities equivalent to the specified value of one of them.
  • Pass-ive nickel contains a much lower impurity content than that specified above, and when it contains no reducing impurities at all, it may be described as inactive, which is 3,113,236 Patented Dec. 3, 1963 ice preferred -in the invention.
  • cathodes of the invention are capable of a continuous (DC. emission, in contrast to pulsed emission) current density of 1.5 a./m.2 at a temperature of 760 C., which is several tens of degrees lower than is usual for oxide cathodes.
  • a tine nickel gauze or mesh or a perforated nickel foil may be employed as the permeable metal member instead of the porous sprayed nickel layer, although the workability of these materials with the required purity is comparatively poor.
  • nickel instead of nickel as the material for the permeable metal layer, it is alternatively possible, -for example, to use molybdenum or tungsten or, if the cost is not objectionable, platinum.
  • a barium oxide compound mixed for example, with reducing material, for example Til-l2 (which during heating decomposes to ⁇ form Ti), which alfords the advantage that it is not necessary to use carbonates to form the oxides previously suggested, in which latter event a fairly large quantity of gas is always evolved.
  • reducing material for example Til-l2 (which during heating decomposes to ⁇ form Ti)
  • barium-strontium oxides obtained from the corresponding carbonates
  • the eniissive layer for example, barium oxide or strontium oxide or calcium oxide, or barium zirconate, which also affords the advantage that it ⁇ does not itself evolve gas upon activation of the cathode and is not harmed by contact with air.
  • FIGS. 1, 2, and 3 are cross-sectional views of three embodiments of a cathode according to the invention.
  • FlG. 1 illustrates a planar type cathode of the invention, comprising a nickel cylinder 1 having a reentrant upper side 2 forming a cavity 12 containing bariumstrontium oxide 3 in the form of a pellet.
  • a gauze or mesh d of pure nickel wire for example, of 35 microns thickness, is welded on top of the cylinder enclosing the cavity l2.
  • the cathode contains a heating lilament 6.
  • a lead-inconductor 1.3 is welded to the bottom end of the nickel support 1.
  • the nickel cylinder ll consists of nickel and several hundredths percent (0.03%) of aluminum and silicon, and is thus active nickel.
  • the nickel mesh l is of high purity and contains no detectable amount of any of the reducing impurities referred to earlier, and is thus inactive nickel.
  • the nickel cylinder 1 may be formed to the shape illustrated in the drawing by a drawing operation.
  • the oxide pellet 3 is placed inside the cavity 12.
  • the pellet 3 may have dimensions of 2 millimeters in diameter and 0.3 millimeter thick, and may comprise a mixture of barium and strontium carbonates in the ratio of 55 to 45 by weight. These carbonates, which are available in powder form, may be heated at 1050 C.
  • the mesh d whose mesh openings are approximately 0.05 millimeter by 0.05 millimeter, is welded over the cavity 12 so as to completely enclose the pellet 3, except, of course, for the mesh openings.
  • a suitable spraying mixture is provided by ball milling 50 grams of powder in 100 millilitres of amyl acetate after which 40 millilitres of butanol with nitrocellulose is added.
  • the terminal i3 which constitutes a current supply lead for the cathode from the external circuit, is welded in place and the ilament 6 provided within the hollow support 1.
  • the supply conductor l by which the cathode is connected in the external circuit, provides a direct current connection through the nickel cylinder l directly to the mesh d, to which it is in direct electrical contact and on which the emissive layer is located.
  • the structure below the mesh comprises the barium dispensing source.
  • the cathode may be operated in the usual electron device at temperatures ranging from about 700 C. to 850 C. ln this range of temperatures, the impurities in the active nickel portion 2 reduce the barium-strontium oxides 3 in the cavity producing free barium, which, by a didusion process, passes outwardly through the openings in the mesh 4 into the oxide layer 5 thereby activating it and causing it in turn to be capable of very high electron emission densities. Because of the constant supply of barium to the emissive layer 5, high continuous or D.C.
  • the cathode of the invention is capable of operation at the low temperatures of the oxide cathode, but without being restricted to the usual pulse operation to produce high emission densities. Moreover, it has been found that barium or strontium evaporation from the cathode is relatively small.
  • FlG. 2 shows a modification of the cathode illustrated in FIG. 1.
  • the pellet 3 consists of barium aluminate, in which the mole ratio of barium oxide (BaO) to aluminum oxide (M203) is 21/2 to 1.0, to which has been added 5% by weight of titanium hydride (Til-I2).
  • the titanium hydride serves as a reducing agent for the barium compound which, when heated to about 800 C., will result in the generation of free barium.
  • the support l, 2 need not contain any reducing impurities. Thus, it may consist of passive nickel or molybdenum.
  • the support l, 2 need not contain any reducing impurities.
  • it may consist of passive nickel or molybdenum.
  • the pellet 3 fills the cavity 12 and forms with the surrounding portions of the cylinder l a relatively smooth surface. Onto this surface is sprayed a layer 7 of pure nickel powder, which thus has an inactive character, for example, to a thickness of 20 microns. As will be noted, the layer '7 is directly electrically connected to the support l. Finally, onto the pure nickel layer '7 is provided an oxide layer 8, which may be a mixture of barium and strontium oxides in the ratio of 55 to 45. The layer 3 may be, for example, 40 microns thick.
  • the barium aluminate may be replaced with a mixture of barium and strontium oxides to which the titanium hydride is added. This combination produces a higher vapor pressure of barium, which means then that the dispensing rate is increased. This renders the cathode less susceptible to poisoning.
  • FIG. 3 shows a cylindrical type cathode of the invention.
  • a hollow support lli with a rectangu- ,liasse lar cross-section and which may be of active cathode nickel, supports on opposed surfaces sprayed layers of mixtures of barium and strontium oxides 9, which, as usual, are provided in the carbonate form and which are converted to the oxides during activation, and on top of the oxide layers 9 is sprayed a layer of pure, inactive, nickel powder lll, which encloses the oxide layers 9.
  • Such sprayed layers are porous and permeable to diffusing barium atoms.
  • layers ll of strontium oxide which, as usual, are initially provided in the carbonate form and converted to the oxide during activation.
  • the nickel layer l0 contacts the nickel support 14.
  • the current supply member or permeable layers 4, 7, and l0 are of inactive material, they do not form insulating interfaces with the emissive layer, which is responsible for the high D.C. emission capabilities of the cathode of the invention.
  • a therm'ionic icathode for an electron device operable at temperatures of about 700 C. to 850 C. cornprising a support, a rst layer on said support off a barium oxidic compound associated Wit-h a reducing substance and capable when heated of reacting together to dispense continuously free barium metal, a barium-permeable electrically-conductive grid-like metal member over and enclosing the said rst layer, means providing an external circuit connection -to said grid-like metal member, an oxidic emissive layer on the grid-like metal member on the side remote from said lirst layer, and means for heating said cathode whereby barium dis Jensed by said iirst layer diffuses through the grid-like metal member into the oxidic emissive layer activating same to produce copious electrons, said grid-like metal member consisting essentially of inactive nickel free of any element selected from the group consisting of aluminum, silicon, tungsten and magnesium and

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US36827A 1959-06-23 1960-06-17 Oxide dispenser type cathode Expired - Lifetime US3113236A (en)

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CH (1) CH397092A (de)
GB (1) GB929002A (de)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3318716A (en) * 1962-09-11 1967-05-09 Pennsalt Chemicals Corp Foam reduction and coating
US3320463A (en) * 1962-07-23 1967-05-16 Gen Electric Electron discharge tube having an improved electrode mounting structure
US3842309A (en) * 1970-11-12 1974-10-15 Philips Corp Method of manufacturing a storage cathode and cathode manufactured by said method
US4400647A (en) * 1981-08-24 1983-08-23 North American Philips Consumer Electronics Corp. Cathode structure for cathode ray tubes and method
US4404492A (en) * 1981-08-24 1983-09-13 North American Philips Consumer Electronics Corp. Cathode structure for cathode ray tubes and method for producing same
US5092779A (en) * 1990-02-21 1992-03-03 Piwonka Dennis F Academic quiz controller

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1234861B (de) * 1965-07-05 1967-02-23 Siemens Ag Vorratskathode fuer elektrische Entladungsgefaesse
US3710161A (en) * 1970-10-30 1973-01-09 Gen Electric Quick-heating impregnated planar cathode
KR910006044B1 (ko) * 1988-11-12 1991-08-12 삼성전관 주식회사 디스펜서 캐소오드의 제조방법
KR100195955B1 (ko) * 1995-12-20 1999-06-15 구자홍 음극구조체의 구조 및 전자방사체 도포방법

Citations (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2131204A (en) * 1936-01-15 1938-09-27 Siemens Ag Indirectly heated thermionic cathode
US2499192A (en) * 1948-01-15 1950-02-28 Gen Electric Dispenser type cathode
US2543728A (en) * 1947-11-26 1951-02-27 Hartford Nat Bank & Trust Co Incandescible cathode
US2698913A (en) * 1951-11-29 1955-01-04 Philips Corp Cathode structure
US2813995A (en) * 1952-10-22 1957-11-19 Gen Electric Cathode and method of manufacture
US2864028A (en) * 1955-08-15 1958-12-09 Philips Corp Thermionic dispenser cathode
DE1046203B (de) * 1952-12-15 1958-12-11 Siemens Ag Vorratskathode fuer elektrische Entladungsgefaesse
DE1047320B (de) * 1956-04-21 1958-12-24 Gen Electric Verfahren zur Herstellung von Oxydkathoden fuer elektrische Entladungsroehren, derenTraegermetall aus reinem Nickel besteht
CA568817A (en) * 1959-01-13 C. Van Der Linden Petrus Thermionic cathode
US2912611A (en) * 1953-08-14 1959-11-10 Int Standard Electric Corp Thermionic cathodes
US2945150A (en) * 1958-12-11 1960-07-12 Gen Electric Thermionic cathodes and methods of making
US2965793A (en) * 1959-05-12 1960-12-20 Westinghouse Electric Corp Electron device
US3056061A (en) * 1959-03-06 1962-09-25 Philips Corp Method of manufacturing nickel supports for oxide cathodes and cathodes provided with such supports

Patent Citations (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CA568817A (en) * 1959-01-13 C. Van Der Linden Petrus Thermionic cathode
US2131204A (en) * 1936-01-15 1938-09-27 Siemens Ag Indirectly heated thermionic cathode
US2543728A (en) * 1947-11-26 1951-02-27 Hartford Nat Bank & Trust Co Incandescible cathode
US2499192A (en) * 1948-01-15 1950-02-28 Gen Electric Dispenser type cathode
US2698913A (en) * 1951-11-29 1955-01-04 Philips Corp Cathode structure
US2813995A (en) * 1952-10-22 1957-11-19 Gen Electric Cathode and method of manufacture
DE1046203B (de) * 1952-12-15 1958-12-11 Siemens Ag Vorratskathode fuer elektrische Entladungsgefaesse
US2912611A (en) * 1953-08-14 1959-11-10 Int Standard Electric Corp Thermionic cathodes
US2864028A (en) * 1955-08-15 1958-12-09 Philips Corp Thermionic dispenser cathode
DE1047320B (de) * 1956-04-21 1958-12-24 Gen Electric Verfahren zur Herstellung von Oxydkathoden fuer elektrische Entladungsroehren, derenTraegermetall aus reinem Nickel besteht
US2945150A (en) * 1958-12-11 1960-07-12 Gen Electric Thermionic cathodes and methods of making
US3056061A (en) * 1959-03-06 1962-09-25 Philips Corp Method of manufacturing nickel supports for oxide cathodes and cathodes provided with such supports
US2965793A (en) * 1959-05-12 1960-12-20 Westinghouse Electric Corp Electron device

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3320463A (en) * 1962-07-23 1967-05-16 Gen Electric Electron discharge tube having an improved electrode mounting structure
US3318716A (en) * 1962-09-11 1967-05-09 Pennsalt Chemicals Corp Foam reduction and coating
US3842309A (en) * 1970-11-12 1974-10-15 Philips Corp Method of manufacturing a storage cathode and cathode manufactured by said method
US4400647A (en) * 1981-08-24 1983-08-23 North American Philips Consumer Electronics Corp. Cathode structure for cathode ray tubes and method
US4404492A (en) * 1981-08-24 1983-09-13 North American Philips Consumer Electronics Corp. Cathode structure for cathode ray tubes and method for producing same
US5092779A (en) * 1990-02-21 1992-03-03 Piwonka Dennis F Academic quiz controller

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GB929002A (en) 1963-06-19
CH397092A (de) 1965-08-15

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