EP0248470B1 - Method of manufacturing a dispenser cathode - Google Patents
Method of manufacturing a dispenser cathode Download PDFInfo
- Publication number
- EP0248470B1 EP0248470B1 EP87200951A EP87200951A EP0248470B1 EP 0248470 B1 EP0248470 B1 EP 0248470B1 EP 87200951 A EP87200951 A EP 87200951A EP 87200951 A EP87200951 A EP 87200951A EP 0248470 B1 EP0248470 B1 EP 0248470B1
- Authority
- EP
- European Patent Office
- Prior art keywords
- tungsten body
- scandium oxide
- surface area
- tungsten
- electron emission
- 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.)
- Expired - Lifetime
Links
- 238000004519 manufacturing process Methods 0.000 title claims description 6
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 claims description 39
- 239000010937 tungsten Substances 0.000 claims description 37
- 229910052721 tungsten Inorganic materials 0.000 claims description 37
- HYXGAEYDKFCVMU-UHFFFAOYSA-N scandium oxide Chemical compound O=[Sc]O[Sc]=O HYXGAEYDKFCVMU-UHFFFAOYSA-N 0.000 claims description 21
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 16
- 239000010949 copper Substances 0.000 claims description 16
- 229910052802 copper Inorganic materials 0.000 claims description 16
- 238000000034 method Methods 0.000 claims description 11
- 239000000463 material Substances 0.000 claims description 6
- 238000005470 impregnation Methods 0.000 claims description 2
- 238000005245 sintering Methods 0.000 claims description 2
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 3
- 229910052788 barium Inorganic materials 0.000 description 3
- DSAJWYNOEDNPEQ-UHFFFAOYSA-N barium atom Chemical compound [Ba] DSAJWYNOEDNPEQ-UHFFFAOYSA-N 0.000 description 3
- 229910052739 hydrogen Inorganic materials 0.000 description 3
- 239000001257 hydrogen Substances 0.000 description 3
- 239000008188 pellet Substances 0.000 description 3
- 230000008020 evaporation Effects 0.000 description 2
- 238000001704 evaporation Methods 0.000 description 2
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 description 1
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 239000004411 aluminium Substances 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- 239000011575 calcium Substances 0.000 description 1
- 229910052791 calcium Inorganic materials 0.000 description 1
- 238000004140 cleaning Methods 0.000 description 1
- 230000006835 compression Effects 0.000 description 1
- 238000007906 compression Methods 0.000 description 1
- 238000005553 drilling Methods 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 239000000155 melt Substances 0.000 description 1
- 238000003801 milling Methods 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 229910017604 nitric acid Inorganic materials 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 238000007514 turning Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Images
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J9/00—Apparatus 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
- H01J9/02—Manufacture of electrodes or electrode systems
- H01J9/04—Manufacture of electrodes or electrode systems of thermionic cathodes
-
- 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
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J9/00—Apparatus 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
- H01J9/02—Manufacture of electrodes or electrode systems
- H01J9/04—Manufacture of electrodes or electrode systems of thermionic cathodes
- H01J9/042—Manufacture, activation of the emissive part
- H01J9/047—Cathodes having impregnated bodies
Definitions
- the invention relates to a method of manufacturing a dispenser cathode comprising a porous tungsten body having a surface area intended for electron emission, which tungsten body incorporates scandium oxide at least in a layer adjacent the surface area intended for electron emission, and which tungsten body containing the scandium oxide is impregnated with an oxidic material after sintering.
- the tungsten body can then be given the required shape mechanically (US-A 2 669 008).
- the copper is removed from the tungsten body by evaporation in a vacuum.
- the method described in the opening paragraph is therefore characterized in that molten copper is absorbed in the entire scandium oxide-containing sintered tungsten body prior to impregnation and in that the copper is removed from the tungsten body after a mechanical design treatment of the tungsten body which is effected at least on the side of the surface area intended for electron emission.
- the method according to the invention is surprising because the processibility of the tungsten body, even if it contains a comparatively high percentage by volume of scandium oxide, is very satisfactory in the presence of copper. Furthermore, the copper can be removed in a comparatively simple manner after the mechanical operation so that there is certainly no question of an expensive, time-consuming and cumbersome method.
- a scandium oxide content of preferably 2 to 10% by weight is used in the tungsten body.
- a scandium oxide content of 3 to 7% by weight is used with special preference in the tungsten body.
- the mechanical treatment preferably extends from the surface area intended for elecron emission throughout a scandium oxide-containing layer adjacent the surface area.
- the drawing diagrammatically shows in a crossection a part of a dispenser cathode manufactured by means of the method according to the invention.
- a dispenser cathode which has a porous tungsten body 1 with a surface area 2 intended for electron emission
- scandium oxide is incorporated in a layer 3 adjacent the surface area 2 intended for electron emission. This is effected, for example, as follows. A 0.5 mm thick layer of tungsten powder is introduced into a mould having a circular opening with a diameter of 1.8 mm. A 0.1 mm thick layer of powder consisting of a mixture of tungsten and 5% by weight of scandium oxide is provided on the layer of tungsten powder.
- the pellet After compression to a pellet the pellet is sintered in hydrogen at 1500°C for 1 hour. The total thickness of the sintered body is then approximately 0.6 mm and the thickness of the layer 3 is approximately 0.1 mm.
- molten copper is absorbed in the entire scandium oxide-containing sintered tungsten body 1.
- the body is provided with oxygen-free copper as a plate or a pellet in a quantity which is at least equal to the free space in the sintered body (the free space in the sintered body is approximately 20%) and is absorbed as a melt in the tungsten body.
- the tungsten body 1 is subjected to a mechanical design treatment at least on the side of the surface area 2 intended for electron emission.
- the latter treatment may be a conventional treatment such as turning, drilling or milling.
- the design treatment extends throughout the layer 3 and the size of the scandium oxide-containing layer 3 is limited so that also the surface area 2 intended for electron emission is limited.
- the copper is removed from the tungsten body. This is effected, for example, by means of nitric acid and water in a 1:1 ratio so that substantially all copper is removed. After cleaning and rinsing any possible last remainders of copper are removed by evaporation for several minutes at 1700°C in hydrogen. By burning the hydrogen flowing from the equipment the absence of copper can be established by the absence of a green colour. Subsequently the tungsten body is impregnated in a conventional manner with oxides of barium, calcium and aluminium (4:1:1), cleaned and welded to a shaft 4 provided with a heating element 5.
- the dispenser cathode shown in the drawing is used, for example, as a component of a diode gun in a cathode ray tube.
- a diode gun in a cathode ray tube.
- Such a gun accommodates above the cathode an anode 6 having a small aperture 7 (diameter, for example, 40 um).
- the beam current passes through this aperture during operation while the anode potential is of course positive with respect to the cathode. Since the diameter of the electron emitting part is small (-0.3 mm) due to the processing operation, the thermal load of the anode may be sufficiently low.
Landscapes
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Solid Thermionic Cathode (AREA)
Description
- The invention relates to a method of manufacturing a dispenser cathode comprising a porous tungsten body having a surface area intended for electron emission, which tungsten body incorporates scandium oxide at least in a layer adjacent the surface area intended for electron emission, and which tungsten body containing the scandium oxide is impregnated with an oxidic material after sintering.
- In the manufacturing practice of dispenser cathodes the mechanical design of the hard and brittle tungsten body has often been found to be a problem.
- In a known method for the mechanical design of porous tungsten bodies copper is therefore absorbed in the tungsten body prior to the mechanical design.
- The tungsten body can then be given the required shape mechanically (US-A 2 669 008).
- Subsequently the copper is removed from the tungsten body by evaporation in a vacuum.
- According to US-A 2 986 799 the method using copper is time-consuming, costly and cumbersome. This patent describes the use of an oxidic barium-containing material instead of copper. This also simplifies processing of the tungsten body and this oxidic material does not have to be removed from the tungsten body because it is required anyway in the electron emission of the cathode.
- In the further development of dispenser cathodes it has been found to be advantageous to incorporate scandium oxide in at least a layer adjacent a surface area of the tungsten body intended for electron emission during the manufacture of the. tungsten body (NL-A 8 201 371).
- It is found that the presence of scandium oxide in the tungsten body may reduce the absorption possibility of barium-containing oxidic material by the tungsten body. Moreover, the prospects for a satisfactory mechanical processing in the presence of scandium oxide are poor because sintered scandium oxide is much more difficult to process mechanically than sintered tungsten.
- It is an object of the invention, inter alia, to obviate the described problem at least to a considerable extent.
- According to the invention, the method described in the opening paragraph is therefore characterized in that molten copper is absorbed in the entire scandium oxide-containing sintered tungsten body prior to impregnation and in that the copper is removed from the tungsten body after a mechanical design treatment of the tungsten body which is effected at least on the side of the surface area intended for electron emission.
- The method according to the invention is surprising because the processibility of the tungsten body, even if it contains a comparatively high percentage by volume of scandium oxide, is very satisfactory in the presence of copper. Furthermore, the copper can be removed in a comparatively simple manner after the mechanical operation so that there is certainly no question of an expensive, time-consuming and cumbersome method.
- A scandium oxide content of preferably 2 to 10% by weight is used in the tungsten body.
- A scandium oxide content of 3 to 7% by weight is used with special preference in the tungsten body.
- The mechanical treatment preferably extends from the surface area intended for elecron emission throughout a scandium oxide-containing layer adjacent the surface area.
- The invention will now be described in greater detail with reference to an example and the accompanying drawing.
- The drawing diagrammatically shows in a crossection a part of a dispenser cathode manufactured by means of the method according to the invention.
- In a method of manufacturing a dispenser cathode which has a
porous tungsten body 1 with asurface area 2 intended for electron emission, scandium oxide is incorporated in alayer 3 adjacent thesurface area 2 intended for electron emission. This is effected, for example, as follows. A 0.5 mm thick layer of tungsten powder is introduced into a mould having a circular opening with a diameter of 1.8 mm. A 0.1 mm thick layer of powder consisting of a mixture of tungsten and 5% by weight of scandium oxide is provided on the layer of tungsten powder. - After compression to a pellet the pellet is sintered in hydrogen at 1500°C for 1 hour. The total thickness of the sintered body is then approximately 0.6 mm and the thickness of the
layer 3 is approximately 0.1 mm. - According to the invention, prior to impregnating the sintered tungsten body with an oxidic material, molten copper is absorbed in the entire scandium oxide-containing sintered
tungsten body 1. - To this end the body is provided with oxygen-free copper as a plate or a pellet in a quantity which is at least equal to the free space in the sintered body (the free space in the sintered body is approximately 20%) and is absorbed as a melt in the tungsten body.
- Subsequently the
tungsten body 1 is subjected to a mechanical design treatment at least on the side of thesurface area 2 intended for electron emission. The latter treatment may be a conventional treatment such as turning, drilling or milling. - In the case shown in the drawing, the design treatment extends throughout the
layer 3 and the size of the scandium oxide-containinglayer 3 is limited so that also thesurface area 2 intended for electron emission is limited. - After the design treatment the copper is removed from the tungsten body. This is effected, for example, by means of nitric acid and water in a 1:1 ratio so that substantially all copper is removed. After cleaning and rinsing any possible last remainders of copper are removed by evaporation for several minutes at 1700°C in hydrogen. By burning the hydrogen flowing from the equipment the absence of copper can be established by the absence of a green colour. Subsequently the tungsten body is impregnated in a conventional manner with oxides of barium, calcium and aluminium (4:1:1), cleaned and welded to a shaft 4 provided with a
heating element 5. - The dispenser cathode shown in the drawing is used, for example, as a component of a diode gun in a cathode ray tube. Such a gun accommodates above the cathode an
anode 6 having a small aperture 7 (diameter, for example, 40 um). The beam current passes through this aperture during operation while the anode potential is of course positive with respect to the cathode. Since the diameter of the electron emitting part is small (-0.3 mm) due to the processing operation, the thermal load of the anode may be sufficiently low.
Claims (5)
1. A method of manufacturing a dispenser cathode comprising a porous tungsten body having a surface area intended for electron emission, which tungsten body incorporates scandium oxide at least in a layer adjacent the surface area intended for electron emission and which tungsten body containing the scandium oxide is impregnated with an oxidic material after sintering, characterized in that molten copper is absorbed in the entire scandium oxide-containing sintered tungsten body prior to impregnation and in that the copper is removed from the tungsten body after a mechanical design treatment of the tungsten body which is effected at least on the side of the surface area intended for electron emission.
2. A method as claimed in Claim 1, characterized in that a scandium oxide content of 2 to 10% by weight is used in the tungsten body.
3. A method as claimed in Claim 2, characterized in that a scandium oxide content of 3 to 7% by weight is used in the tungsten body.
4. A method as claimed in any one of the preceding Claims, characterized in that the mechanical treatment extends from the surface area intended for electron emission throughout a scandium oxide-containing layer adjacent said surface area.
5. A cathode ray tube including a dispenser cathode manufactured by means of the method as claimed in any one of the preceding Claims.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| NL8601374 | 1986-05-29 | ||
| NL8601374A NL8601374A (en) | 1986-05-29 | 1986-05-29 | METHOD FOR MANUFACTURING A SUPPLY CATHOD |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| EP0248470A1 EP0248470A1 (en) | 1987-12-09 |
| EP0248470B1 true EP0248470B1 (en) | 1990-03-28 |
Family
ID=19848086
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP87200951A Expired - Lifetime EP0248470B1 (en) | 1986-05-29 | 1987-05-20 | Method of manufacturing a dispenser cathode |
Country Status (5)
| Country | Link |
|---|---|
| EP (1) | EP0248470B1 (en) |
| JP (1) | JPH0711935B2 (en) |
| KR (1) | KR870011653A (en) |
| DE (1) | DE3762075D1 (en) |
| NL (1) | NL8601374A (en) |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4236287A (en) * | 1979-06-25 | 1980-12-02 | The United States Of America As Represented By The Secretary Of The Army | Method of making a ruggedized high current density cathode |
| 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 |
-
1986
- 1986-05-29 NL NL8601374A patent/NL8601374A/en not_active Application Discontinuation
-
1987
- 1987-05-20 DE DE8787200951T patent/DE3762075D1/en not_active Expired - Lifetime
- 1987-05-20 EP EP87200951A patent/EP0248470B1/en not_active Expired - Lifetime
- 1987-05-26 JP JP12730587A patent/JPH0711935B2/en not_active Expired - Lifetime
- 1987-05-26 KR KR870005197A patent/KR870011653A/en not_active Ceased
Also Published As
| Publication number | Publication date |
|---|---|
| NL8601374A (en) | 1987-12-16 |
| EP0248470A1 (en) | 1987-12-09 |
| DE3762075D1 (en) | 1990-05-03 |
| KR870011653A (en) | 1987-12-24 |
| JPH0711935B2 (en) | 1995-02-08 |
| JPS62281223A (en) | 1987-12-07 |
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