US3472693A - Cathodes for use in electric discharge tubes - Google Patents

Cathodes for use in electric discharge tubes Download PDF

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Publication number
US3472693A
US3472693A US526050A US3472693DA US3472693A US 3472693 A US3472693 A US 3472693A US 526050 A US526050 A US 526050A US 3472693D A US3472693D A US 3472693DA US 3472693 A US3472693 A US 3472693A
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United States
Prior art keywords
cathode
layer
temperature
cathodes
electric discharge
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Expired - Lifetime
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US526050A
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English (en)
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Friedrich Hermann Raymun Almer
Adrianus Kuiper
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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
    • 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

Definitions

  • the invention relates to a cathode for use in an electric discharge tube, more particularly to a cathode the emissive layer of which consists of barium-strontiumoxides.
  • the usual operating temperature of such a cathode is approximately 750 C. (real temperature). This temperature is based on a compromise. At an excessively high temperature a satisfactory emission is obtained, it is true, since the reduction of the oxides of the emissive layer proceeds more rapidly, but the evaporation of Ba also increases considerably, as a result of which the life is shortened. The formation of a poorly conducting intermediate layer between the emissive oxide layer and a support consisting of active nickel is also strongly promoted so that such a layer will cause difficulties before the usual life of the cathode has been attained. In indirectly heated cathodes, the insulation between cathode and heating wire moreover materially deteriorates owing to the high temperature.
  • titanium and titanium hydride may have a favourable influence on the emissive layer, but it has been found in practice that it is not desirable to simply mix these substances with the Ba-Sr oxides since at the said usual cathode temperature an intermediate layer of high resistance is then soon formed. It has therefore already been suggested to replace Ti by rhenium. Since Ti reduces the electric resistance of the oxide layer itself, it has already been suggested to use this substance in heavily loaded cathodes. In order to avoid the disadvantages of the formation of an intermediate layer of 3,472,693 Patented Oct. 14, 1969 high resistance, the Ti-containing layer was separated, however, from the Ba-Sr oxide layer by a layer consisting of pure nickel or by gauze. In this manner, the reducing action of Ti was consequently utilized without difficulties arising as a result of an intermediate layer of high resistance.
  • Ti in the emissive layer is undesirable, consists in that such a Ticontaining layer has a darker surface than a layer consisting of Ba-Sr oxide so that the heating energy must be raised in order to attain the usual cathode temperature, which is also undesirable.
  • the emissive barium-strontium oxide layer of the cathode contains 2 to 4% by weight of titanium hydride while the nominal operating temperature of the cathode lies below 700 C. real temperature. Owing to the lower operating temperature the formation of an insulating intermediate layer now proceeds so slowly that this layer does not cause any difiiculties during the life of the cathode. It has further been found that the TiH prevents the life of the cathode from being shortened as a result of the low operating temperature. In the first place the TiH promotes the reduction of the emissive oxides so that a sufiicient quantity of Ba is released notwithstanding the low operating temperature, but moreover the TiH prevents this Ba from being oxidized again by oxidizing gases.
  • the reduction of life at an excessively low cathode temperature is mainly due to the fact that oxidizing gases released from the electrodes oxidize the barium still available in the oxide layer, since these gases are not bound sufliciently rapidly owing to the lower evaporation of Ba while oxides, if any, formed by these gases in the layer are decomposed less rapidly.
  • the operating temperature of a cathode in accordance with the invention may be considerably lower than is usual, it is not required for the heating energy to be raised although the emissive layer has a darker surface. Owing to this fact alone, the cathode temperature is reduced by C. to C. It has been found that in many cases the heating energy can be even reduced by 20 to 30% without the cathode being adversely affected.
  • the invention is of importance especially with regard to the tendency to reduce the dimensions of discharge tubes to a minimum, since the insulating layer between cathode and heating wire may be thinner and the electrode distances may be reduced.
  • a thermionic cathode for an electric discharge tube comprising a support and an electron-emissive layer thereon, said electron-emissive layer consisting essentially of alkaline-earth oxides and 2 to 4% by weight of titanium 3 4 hydride, said cathode having a nominal operating tem- 3,159,461 12/1964 MacNair 313346 X perature below 700 C. real temperature. 3,333,141 7/1967 Lemmens et a1. 313-346 2.
  • a thermionic cathode as claimed in claim 1 in which the support is nickel and the alkaline-earth oxides are FOREIGN PATENTS barium and strontium oxides. 5 1,103,263 5/1955 France.

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  • Discharge Lamp (AREA)
  • Solid Thermionic Cathode (AREA)
US526050A 1965-02-17 1966-02-09 Cathodes for use in electric discharge tubes Expired - Lifetime US3472693A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
NL6501944A NL6501944A (xx) 1965-02-17 1965-02-17

Publications (1)

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US3472693A true US3472693A (en) 1969-10-14

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US526050A Expired - Lifetime US3472693A (en) 1965-02-17 1966-02-09 Cathodes for use in electric discharge tubes

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US (1) US3472693A (xx)
AT (1) AT258427B (xx)
BE (1) BE676530A (xx)
CH (1) CH441514A (xx)
DE (1) DE1564381A1 (xx)
DK (1) DK112397B (xx)
ES (1) ES323084A1 (xx)
GB (1) GB1069102A (xx)
NL (1) NL6501944A (xx)

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR1103263A (fr) * 1953-07-03 1955-11-02 English Electric Valve Co Ltd Perfectionnements aux revêtements métalliques adhérents
US3099577A (en) * 1960-08-24 1963-07-30 Philips Corp Method of manufacturing oxide cathodes and cathodes manufactured by such methods
US3155864A (en) * 1960-03-21 1964-11-03 Gen Electric Dispenser cathode
US3159461A (en) * 1958-10-20 1964-12-01 Bell Telephone Labor Inc Thermionic cathode
US3333141A (en) * 1961-03-08 1967-07-25 Philips Corp Double layer oxide cathode with reducing agent

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR1103263A (fr) * 1953-07-03 1955-11-02 English Electric Valve Co Ltd Perfectionnements aux revêtements métalliques adhérents
US3159461A (en) * 1958-10-20 1964-12-01 Bell Telephone Labor Inc Thermionic cathode
US3155864A (en) * 1960-03-21 1964-11-03 Gen Electric Dispenser cathode
US3099577A (en) * 1960-08-24 1963-07-30 Philips Corp Method of manufacturing oxide cathodes and cathodes manufactured by such methods
US3333141A (en) * 1961-03-08 1967-07-25 Philips Corp Double layer oxide cathode with reducing agent

Also Published As

Publication number Publication date
NL6501944A (xx) 1966-08-18
DK112397B (da) 1968-12-09
GB1069102A (en) 1967-05-17
ES323084A1 (es) 1967-01-01
AT258427B (de) 1967-11-27
CH441514A (de) 1967-08-15
BE676530A (xx) 1966-08-16
DE1564381A1 (de) 1970-03-12

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