US2831137A - Cathode coating - Google Patents

Cathode coating Download PDF

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Publication number
US2831137A
US2831137A US563754A US56375456A US2831137A US 2831137 A US2831137 A US 2831137A US 563754 A US563754 A US 563754A US 56375456 A US56375456 A US 56375456A US 2831137 A US2831137 A US 2831137A
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United States
Prior art keywords
barium
alkaline
weight
oxide
metal
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Expired - Lifetime
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US563754A
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English (en)
Inventor
Roebling Werner
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Osram GmbH
Original Assignee
Patent Treuhand Gesellschaft fuer Elektrische Gluehlampen mbH
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J61/00—Gas-discharge or vapour-discharge lamps
    • H01J61/02—Details
    • H01J61/04—Electrodes; Screens; Shields
    • H01J61/06—Main electrodes
    • H01J61/067—Main electrodes for low-pressure discharge lamps
    • H01J61/0675—Main electrodes for low-pressure discharge lamps characterised by the material of the electrode
    • H01J61/0677—Main electrodes for low-pressure discharge lamps characterised by the material of the electrode characterised by the electron emissive material

Definitions

  • FIG.2
  • This invention relates to low-pressure electric discharge devices filled with gas and/or vapor and, more part cularly, to fluorescent lamps and cathode emission coatings therefor.
  • Fluorescent lamps are usually provided with incandescent filamentary electrodes which carry a mixture of alkaline-earth oxides as electron-emission material.
  • the emission of electrons is effected principally by barium oxide which normally has a small stoichiometric excess of metallic barium as is well known.
  • the other alkaline-earth oxides which may be included, e. g., strontium and calcium oxides, are eifective in retarding the evaporation of the barium oxide or of the metallic barium.
  • barium oxide has the lowest electronic work function as compared to the other alkaline-earth oxides, but it also has the highest vapor pressure so that it is normally preferably not to use an emission material consisting solely of barium oxide since the life is decreased, except in special applications.
  • Fig. 1 illustrates an elevational view of a fluorescent lamp
  • Fig. 2 illustrates an axial view taken through an electrode of the lamp illustrated in Fig. 1.
  • the emission material is normally applied to a refractory metal coil, such as timgsten, by suspending the alkaline-earth carbonates and a binder, such as nitrocellulose, in an organic solvent,
  • the cathode coil is dipped into the suspended emission material which fills the turns between the coils. If a coiled-coil type is used, only the turns between the minor coils are filled with emission material.
  • the coated electrodes are then mounted in the lamp and treated by heating to thedecornposition temperatures of the coated alkalineearth carbonates to convert the carbonates to oxides, as is well known.
  • the eifect is the same, that is, the life of the lamp is increased and the end blackening decreased.
  • the ion radius of potassium which is 1.33 A. U., lies between the ion radius of barium, which is 1.43 A. U., and that of strontium, which is 1.29 A.
  • the ion radius of sodium which is 0.98 A. U., is close to that of calcium, which is 1.06 A. U.
  • the alkaline earth'tartrate prepared in the aforesaid manner is then liberated from excessive outward-adher- Patented Apr. 15, 1958.
  • the strontium compound is a base, which has a deleterious effect on the binder and the second heating eliminates this Following is a specific example of the foregoing procedure:
  • Carbonates prepared in accordance with the foregoing specific examples will contain alkali carbonates as follows:
  • the percentages by weight of potassium and sodium with respect to the total barium in the emission material are then 0.25 for potassium and 0.09 for sodium.
  • the calcium carbonate if such is to be used in the mixture, is preferably precipitated without the alkali addition, by methods which are well known.
  • calcium carbonate may be precipitated alkali free with ammonium carbonate and calcium nitrate.
  • barium carbonate and strontium carbonate may be mixed in proportions of 1:1 by weight.
  • Calcium carbonate may be substituted fully or partly for the strontium carbonate, if desired.
  • the barium, strontium and calcium carbonates prepared as above may be admixed in the proportions by weight of 5:3:2 respectively.
  • the percent by weight of sodium with respect to the total barium is from 0.031% to 0.62%.
  • lamps embodying the emission materials of this invention have displayed a increase in life. Also the first appearance of end blackening averaged about 1200 hours later in life than the control lamps.
  • a low-pressure gaseous discharge fluorescent lamp comprising a vitreous light-transmitting tubular envelope 1, having a luminescent material coated on the interior surface thereof, for example, the well-known zinc beryllium silicate. Sealed through the ends of the envelope are lead conductors which support electrodes 2 between their inwardly extending extremities.
  • the electrodes 2 consist of a refractory metal, such as tungsten, coiled to receive the emission material of this invention between the coils.
  • the electrodes may also take the form of a coiled-coil, as is customary in many designs, in which case the emission material normally is coated between the turns of the minor coil.
  • the envelope contains a small charge of mercury, as is customary and a small filling of inert, ionizable gas to facilitate starting, as is customary, a filling of argon at a pressure of 4 mm. mercury, for example, being suitable.
  • Fig. 2 represents a section of the electrode 2 showing the emission material 3 of this invention held between the turns of the electrode coil.
  • An electromemissive coating material for electric gaseous discharge device electrodes said material always containing barium oxide and comprising at least one oxide of an alkaline-earth metal and a total of from about 0.05% to 1.5% by weight of emission material of at least one alkali metal having a work function greater than barium and an ion radius less than barium.
  • An electron-emissive coating material for electric gaseous discharge device electrodes said material always containing barium oxide and comprising at least one oxide of an alkaline-earth metal and at least one of the group consisting of sodium and potassium, the percent by weight of sodium with respect to total barium expressed as metal being from 0.03l% to 0.62%, the percent by weight oi' potassium with respect to total barium expressed as metal being from 0.04% to 0.81%, and the total weight of said alkali metal being from about 0.05% to 1.5 by weight of said coating material.
  • An electron-emissive coating material for electric gaseous discharge device electrodes comprising barium oxide and strontium oxide in the ratio of 1:1 and at least one of the group consisting of sodium and potassium, the percent by weight of sodium with respect to total barium expressed as metal being from 0.04% to 0.62%, the percent by weight of potassium with respect to total barium expressed as metal being from 0.04% to 0.81%, and the total weight of said alkali metal being from about 0.05% to 1.5% by weight of said coating material.
  • An electron-emissive coating material for electric gaseous discharge device electrodes comprising barium oxide and strontium oxide and calcium oxide in the ratio of 5:312 and at least one of the group consisting of sodium and potassium, the percent by weight of sodium with respect to total barium expressed as metal being from 0.031% to 0.62%, the percent by weight of potassium with respect to total barium expressed as metal being from 0.04% to 0.81%, and the total weight of said 5 alkali metal being from about 0.05% to 1.5% by weight of said coating material.
  • An electron-emissive coating material for electric gaseous discharge device electrodes said material always containing barium oxide and comprising at least one oxide of an alkaline earth metal and from 0.04% to 0.81% by weight of potassium with respect to total barium expressed as metal.
  • An electron-emissive coating material for electric gaseous discharge device electrodes said material always containing barium oxide and comprising at least one oxide of an alkaline earth metal and about 0.25% by weight of potassium with respect to total barium expressed as metal.
  • An electron-emissive coating material for electric gaseous discharge device electrodes said material always containing barium oxide and comprising at least one oxide of an alkaline earth metal and from 0.031% to 0.62% by weight of total barium of sodium with respect to total barium expressed as metal.
  • An electron-emissive coating material for electric gaseous discharge device electrodes said material always containing barium oxide and comprising at least one oxide of an alkaline earth metal and about 0.09% by weight of sodium with respect to total barium expressed as metal.
  • a fluorescent lamp comprising a sealed, light-transmitting envelope, a coating of fluorescent material on the inner wall of said envelope, a quantity of mercury in said envelope, a filling of inert gas in said envelope, filamentary electrodes in said envelope and a coating material on said electrodes, said coating material always containing barium oxide and comprising at least one oxide of an alkaline-earth metal and at least one of the group consisting of sodium and potassium, the percent by weight of sodium with respect to total barium expressed as metal being from 0.031% to 0.62%, the percent by weight of potassium with respect to total barium expressed as metal being from 0.04% to 0.81% and the total weight of said alkali metal being from about 0.05% to 1.5% by weight of said coating material.
  • a fluorescent lamp comprising a sealed, light-transmitting envelope, a coating of fluorescent material on the inner wall of said envelope, a quantity of mercury in said envelope, a filling of inert gas in said envelope, filamentary electrodes in said envelope and a coating material on said electrodes, said coating material always containing barium oxide and comprising at least one oxide of an alkaline-earth metal and from 0.04% to 0.81% by weight of potassium with respect to barium expressed as metal.
  • a fluorescent lamp comprising a sealed, light-transmitting envelope, a coating of fluorescent material on the inner wall of said envelope, a quantity of mercury in said envelope, a filling of inert gas in said envelope, filamentary electrodes in said envelope and a coating material on said electrodes, said coating material always containing barium oxide and comprising at least one oxide of an alkaline-earth metal and from 0.031% to 0.62% by weight of sodium with respect to barium expressed as metal.

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  • Discharge Lamp (AREA)
US563754A 1955-02-23 1956-02-06 Cathode coating Expired - Lifetime US2831137A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DEP13621A DE1005636B (de) 1955-02-23 1955-02-23 Elektrische Niederdruckentladungsroehre, insbesondere Leuchtstofflampe

Publications (1)

Publication Number Publication Date
US2831137A true US2831137A (en) 1958-04-15

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US563754A Expired - Lifetime US2831137A (en) 1955-02-23 1956-02-06 Cathode coating

Country Status (5)

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US (1) US2831137A (fr)
BE (1) BE545445A (fr)
DE (1) DE1005636B (fr)
FR (1) FR1141719A (fr)
GB (1) GB822553A (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2963450A (en) * 1958-03-17 1960-12-06 Interlectric Corp Filament coating composition
US20040164680A1 (en) * 2001-11-12 2004-08-26 Saes Getters S.P.A. Discharge lamps using hollow cathodes with integrated getters and methods for manufacturing same

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1817636A (en) * 1926-06-09 1931-08-04 Electrons Inc Electron emissive materials
US2201167A (en) * 1937-03-09 1940-05-21 Germeshausen Kenneth Joseph Gaseous-discharge device
US2530394A (en) * 1947-06-05 1950-11-21 Sylvania Electric Prod Electrode coating for discharge devices
US2677623A (en) * 1949-10-27 1954-05-04 Ets Claude Paz & Silva Process for manufacturing electron emissive material and electrodes
US2714681A (en) * 1948-08-27 1955-08-02 Gen Electric Electric discharge device

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1817636A (en) * 1926-06-09 1931-08-04 Electrons Inc Electron emissive materials
US2201167A (en) * 1937-03-09 1940-05-21 Germeshausen Kenneth Joseph Gaseous-discharge device
US2530394A (en) * 1947-06-05 1950-11-21 Sylvania Electric Prod Electrode coating for discharge devices
US2714681A (en) * 1948-08-27 1955-08-02 Gen Electric Electric discharge device
US2677623A (en) * 1949-10-27 1954-05-04 Ets Claude Paz & Silva Process for manufacturing electron emissive material and electrodes

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2963450A (en) * 1958-03-17 1960-12-06 Interlectric Corp Filament coating composition
US20040164680A1 (en) * 2001-11-12 2004-08-26 Saes Getters S.P.A. Discharge lamps using hollow cathodes with integrated getters and methods for manufacturing same
US20050136786A1 (en) * 2001-11-12 2005-06-23 Alessandro Gallitognotta Hollow cathodes with getter layers on inner and outer surfaces

Also Published As

Publication number Publication date
GB822553A (en) 1959-10-28
FR1141719A (fr) 1957-09-06
DE1005636B (de) 1957-04-04
BE545445A (fr)

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