NL8701583A - Scandat cathod. - Google Patents

Scandat cathod. Download PDF

Info

Publication number
NL8701583A
NL8701583A NL8701583A NL8701583A NL8701583A NL 8701583 A NL8701583 A NL 8701583A NL 8701583 A NL8701583 A NL 8701583A NL 8701583 A NL8701583 A NL 8701583A NL 8701583 A NL8701583 A NL 8701583A
Authority
NL
Netherlands
Prior art keywords
cathode
scandium
body
characterized
method according
Prior art date
Application number
NL8701583A
Other languages
Dutch (nl)
Original Assignee
Philips 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 Nv filed Critical Philips Nv
Priority to NL8701583 priority Critical
Priority to NL8701583A priority patent/NL8701583A/en
Publication of NL8701583A publication Critical patent/NL8701583A/en
Priority claimed from US07/738,061 external-priority patent/US5261845A/en

Links

Classifications

    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01JELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J9/00Apparatus 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
    • H01J9/02Manufacture of electrodes or electrode systems
    • H01J9/04Manufacture of electrodes or electrode systems of thermionic cathodes
    • H01J9/042Manufacture, activation of the emissive part
    • H01J9/047Cathodes having impregnated bodies
    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01JELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J1/00Details 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
    • H01J1/02Main electrodes
    • H01J1/13Solid thermionic cathodes
    • H01J1/20Cathodes heated indirectly by an electric current; Cathodes heated by electron or ion bombardment
    • H01J1/28Dispenser-type cathodes, e.g. L-cathode

Description

* * ΡΗΝ 12,171 1 N.V. Philips' Incandescent lamp factories in Eindhoven.

Scandat cathode.

The invention relates to a method for manufacturing a back-supply cathode, comprising a barium compound for supplying barium to an emissive surface of a porous cathode body, which mainly consists of a high-melting metal.

The invention also relates to a subsequent supply cathode manufactured by means of such a method, as well as an electron tube provided with such a cathode.

Subsequent delivery cathodes are characterized in that there is a functional separation between the electron-emitting surface on the one hand and a stock of the emitter material on the other hand, which serves to effect a sufficiently low exit potential on the emitting surface. The emitter material is located in the pores of the porous metal cathode body.

A method of the type described in the opening paragraph is described in U.S. Patent No. 4,077,393. It describes how a tungsten powder pressed and subsequently sintered cathode body with a porosity of about 20% is impregnated with a mixture which, in addition to barium oxide, also contains calcium oxide, aluminum oxide and scandium oxide.

In European Patent No. 0 091 161 shows how such cathodes can be improved with respect to ion bombardment susceptibility and recovery by pressing the cathode body (especially the top layer) from a mixture of tungsten powder and scandium oxide and then sintering it. In order to obtain a cathode body with a thin (about 0.1 mm) and as homogeneous top layer as possible, the pressing is generally carried out in two steps. First, the tungsten portion of the cathode body is lightly pre-pressed. The top layer powder is then evenly distributed over a surface of the tungsten section, after which the final pressing follows.

The object of the invention is to indicate a different method 870 1583 t PHN 12.171 2 for the manufacture of such a subsequent supply cathode which is simpler and leads to similar results with regard to current density and service life.

To this end, a method according to the invention is characterized in that the cathode body is pressed from an amount of metal powder, which is mixed with scandium or scandium hydride, after which the body is sintered and the cathode is provided with emitter material. The amount of scandium or scandium hydride in the amount of metal powder is preferably 0.3-0.7% by weight.

Such a method is more advantageous from a manufacturing point of view because the pressing only has to be carried out once and the distribution of the top layer powder is no longer necessary. The cathode bodies manufactured by means of such a method can undergo mechanical operations such as turning or other types of shaping without introducing the impregnant without adverse effects.

In order to prevent scandium from being lost during sintering, which preferably takes place in a hydrogen atmosphere, this sintering preferably takes place at a temperature lower than the melting point of scandium (1539 ° C). On the other hand, however, the sintering temperature must be chosen as high as possible to give the cathode body sufficient strength.

A preferred embodiment of a method according to the invention is therefore characterized in that the sintering temperature is between 1430 ° C and 1500 ° C.

The invention is now further illustrated by way of example with reference to a few exemplary embodiments and the drawing, in which:

Figure 1 shows a longitudinal section of a cathode according to the invention and;

Figure 2 shows a view of a cylindrical cathode according to the invention.

Figure 1 shows a longitudinal section of a cathode according to the invention. The cathode body 1 is pressed from a mixture of tungsten powder and about 0.5 weight percent scandium or scandium hydride. After compression at a pressure of about 3.5 atmospheres and sintering in hydrogen for about an hour at 87 01 58 5? PHN 12.171 3 1450 ° C has the scandium-containing tungsten cathode body with a porosity of about 20¾. The cathode body 1 now has, for example, a thickness of 0.5 mm and a diameter of approximately 1.8 mm.

When using scandium hydride, this is decomposed during sintering. Because scandium hydride has a greater specific volume than scandium, it is therefore preferable to pump out the hydrogen when sintering in hydrogen.

Then, the cathode body 1 is impregnated in a hydrogen atmosphere with barium-calcium aliminate (for example 5BaO; 10 2AI2O3; 3CaO or 4BaO; IAI2O3; 1CaO), pressed into a holder 2 and welded onto the cathode shaft 3. In the cathode shaft 3 there is a spiral cathode filament 4, which consists of a metal spiral wound core 5 and an aluminum oxide insulating layer 6. The emission from the emissive surface 7 of such a cathode was about 100 A / cm @ 950 ° C obtained with a pulse load at 1,000 V in a diode with a cathode-anode spacing of 0.3 mm. Such an emission is comparable to that of a cathode with a tungsten and scandium oxide top layer, as described in European patent application no. 0 178 716 (PHN 11.169), which is more difficult to manufacture. The recovery after ion bombardment was comparable to that of the cathode described there with a cathode body sintered at about 1900 ° C (about 65%). With a cathode according to the invention, sintered at 1500 ° C, this recovery was worse and amounted to about 58%. For the significance of the recovery percentages and the method of determination thereof, reference is made to European patent application no. 0 178 716 or the journal article "Properties and manufacture of top-layer scandate cathodes" in Applied Surface Science 26 (1986), pages 173-195.

The impregnant absorption in the above example was about 4.5%. When the amount of scandium (hydride) 30 in the mixture to be pressed was increased to 1% by weight, this uptake decreased to about 2%, which shortens the life of the cathode. For an amount of 0.3-0.7% by weight of scandium (hydride), the amount of impregnant incorporated is sufficient; the recovery after ion bombardment showed no significant change in this region.

Also, from a tungsten body that has been pressed according to the above-described method, a cylinder 20 with an emissive surface 21, shown in view in Figure 2, can be rotated, into which an 8701583.

PHN 12.171 4 heating element is fitted.

The cathodes according to the invention can be used in electron tubes such as, for example, microwave ovens, transmission tubes, etc., but also in cathode ray tubes for television applications and electron microscopy.

8701583

Claims (7)

  1. A method of manufacturing a back-supply cathode, comprising a barium compound for supplying barium to an emissive surface of a porous cathode body, which consists essentially of a high-melting metal, characterized in that the cathode body is pressed from an amount of metal powder mixed with scandium or scandium hydride, after which the body is sintered and the cathode is provided with emitter material.
  2. 2. Process according to claim 1, characterized in that the amount of scandium or scandium hydride in the mixture of metal powder and scandium or scandium hydride is about 0.3 to 0.7% by weight.
  3. A method according to claim 1 or 2, characterized in that the sintering temperature is lower than the melting temperature of scandium.
  4. Method according to claim 3, characterized in that the sintering temperature is between 1430 ° C and 1500 ° C.
  5. Method according to any one of the preceding claims, characterized in that the cathode body undergoes final shaping after being provided with emitter material.
  6. Subsequent delivery cathode manufactured using a method according to any one of claims 1 to 5.
  7. Electron tube provided with a cathode according to claim 6. 8701583 PHN 12.171 6 t λ Extract: Pressed scandate cathode. An impregnated scandate cathode cathode body is obtained by pressing and sintering a mixture of tungsten powder with about 0.5 weight percent scandium, after which the body is impregnated. 8701583
NL8701583A 1987-07-06 1987-07-06 Scandat cathod. NL8701583A (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
NL8701583 1987-07-06
NL8701583A NL8701583A (en) 1987-07-06 1987-07-06 Scandat cathod.

Applications Claiming Priority (7)

Application Number Priority Date Filing Date Title
NL8701583A NL8701583A (en) 1987-07-06 1987-07-06 Scandat cathod.
KR1019880008245A KR890002949A (en) 1987-07-06 1988-07-04 Dispenser cathode manufacturing method
EP88201392A EP0298558B1 (en) 1987-07-06 1988-07-04 Method of manufacturing a scandat cathode
JP63165191A JP2685232B2 (en) 1987-07-06 1988-07-04 Method for manufacturing scandium-based cathode
DE3889696T DE3889696T2 (en) 1987-07-06 1988-07-04 Process for making a scandate cathode.
DE3889696A DE3889696D1 (en) 1987-07-06 1988-07-04 Process for making a scandate cathode.
US07/738,061 US5261845A (en) 1987-07-06 1991-07-30 Scandate cathode

Publications (1)

Publication Number Publication Date
NL8701583A true NL8701583A (en) 1989-02-01

Family

ID=19850259

Family Applications (1)

Application Number Title Priority Date Filing Date
NL8701583A NL8701583A (en) 1987-07-06 1987-07-06 Scandat cathod.

Country Status (5)

Country Link
EP (1) EP0298558B1 (en)
JP (1) JP2685232B2 (en)
KR (1) KR890002949A (en)
DE (2) DE3889696T2 (en)
NL (1) NL8701583A (en)

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NL8902793A (en) * 1989-11-13 1991-06-03 Philips Nv Scandat cathod.
BE1007677A3 (en) * 1993-10-28 1995-09-12 Philips Electronics Nv Method for manufacturing a dispenser cathode
BE1007676A3 (en) * 1993-10-28 1995-09-12 Philips Electronics Nv Method for manufacturing a dispenser cathode
AT167755T (en) * 1993-10-28 1998-07-15 Philips Electronics Nv Stock cathode and manufacturing method
US5407633A (en) * 1994-03-15 1995-04-18 U.S. Philips Corporation Method of manufacturing a dispenser cathode

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NL165880C (en) * 1975-02-21 1981-05-15 Philips Nv Delivery cathod.
JPH054772B2 (en) * 1982-03-10 1993-01-20 Hitachi Ltd
NL8201371A (en) * 1982-04-01 1983-11-01 Philips Nv Methods for manufacturing a supply cathod and supply cathod manufactured by these methods
NL8403032A (en) * 1984-10-05 1986-05-01 Philips Nv Method for manufacturing a scandal follow-up cathod, follow-up cathod made with this method
NL8403031A (en) * 1984-10-05 1986-05-01 Philips Nv METHOD FOR MANUFACTURING A SCANDAL FOLLOW-UP CATHOD AND SCANDAL FOLLOW-UP CATHOD Manufactured By This Method
JPS63254636A (en) * 1987-04-10 1988-10-21 Hitachi Ltd Impregnated cathode

Also Published As

Publication number Publication date
JP2685232B2 (en) 1997-12-03
EP0298558A1 (en) 1989-01-11
JPH01163941A (en) 1989-06-28
KR890002949A (en) 1989-04-12
DE3889696D1 (en) 1994-06-30
DE3889696T2 (en) 1994-12-08
EP0298558B1 (en) 1994-05-25

Similar Documents

Publication Publication Date Title
US4797593A (en) Cathode for electron tube
US4518890A (en) Impregnated cathode
US2912611A (en) Thermionic cathodes
CA1042061A (en) Dispenser cathode with oxide of barium, scandium and aluminium
EP0584858A1 (en) Low pressure discharge lamp having sintered "cold cathode" discharge electrodes
US2700118A (en) Incandescible cathode
EP0317002B1 (en) Scandate cathode
CA1265329A (en) Method of manufacturing a scandate dispenser cathode and dispenser cathode manufactured by means of the method
US2700000A (en) Thermionic cathode and method of manufacturing same
US4350920A (en) Dispenser cathode
JP3175592B2 (en) Discharge lamp electrode
US3911309A (en) Electrode comprising a porous sintered body
US4823044A (en) Dispenser cathode and method of manufacture therefor
US4400648A (en) Impregnated cathode
EP0204477B1 (en) Cathode for electron tube and manufacturing method thereof
US3558966A (en) Directly heated dispenser cathode
US6664733B2 (en) Electrode for discharge tube, and discharge tube using it
CA1212715A (en) Methods of manufacturing a dispenser cathode and dispenser cathode manufactured according to the method
US2501089A (en) Thermionic electron emitter
US3842309A (en) Method of manufacturing a storage cathode and cathode manufactured by said method
US6447355B1 (en) Impregnated-type cathode substrate with large particle diameter low porosity region and small particle diameter high porosity region
KR930006341B1 (en) Method of manufacturing a dispenser cathodes
US2389060A (en) Refractory body of high electronic emission
US2716716A (en) Cathode containing a supply of an electron-emissive material
US4494035A (en) Thermoelectric cathode for a hyperfrequency valve and valves incorporating such cathodes

Legal Events

Date Code Title Description
A1B A search report has been drawn up
BV The patent application has lapsed