EP0673051A1 - Dispenser cathode - Google Patents
Dispenser cathode Download PDFInfo
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- EP0673051A1 EP0673051A1 EP95103216A EP95103216A EP0673051A1 EP 0673051 A1 EP0673051 A1 EP 0673051A1 EP 95103216 A EP95103216 A EP 95103216A EP 95103216 A EP95103216 A EP 95103216A EP 0673051 A1 EP0673051 A1 EP 0673051A1
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- 229910052751 metal Inorganic materials 0.000 claims abstract description 32
- 239000002184 metal Substances 0.000 claims abstract description 32
- 239000000463 material Substances 0.000 claims abstract description 21
- 239000000843 powder Substances 0.000 claims abstract description 20
- QDOXWKRWXJOMAK-UHFFFAOYSA-N dichromium trioxide Chemical compound O=[Cr]O[Cr]=O QDOXWKRWXJOMAK-UHFFFAOYSA-N 0.000 claims abstract description 19
- 229910052804 chromium Inorganic materials 0.000 claims abstract description 17
- 229910052762 osmium Inorganic materials 0.000 claims abstract description 17
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 claims abstract description 16
- SYQBFIAQOQZEGI-UHFFFAOYSA-N osmium atom Chemical compound [Os] SYQBFIAQOQZEGI-UHFFFAOYSA-N 0.000 claims abstract description 16
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 claims abstract description 15
- 229910052721 tungsten Inorganic materials 0.000 claims abstract description 14
- 229910052750 molybdenum Inorganic materials 0.000 claims abstract description 7
- 229910052741 iridium Inorganic materials 0.000 claims abstract description 3
- 229910052759 nickel Inorganic materials 0.000 claims abstract description 3
- 229910052697 platinum Inorganic materials 0.000 claims abstract description 3
- 229910052702 rhenium Inorganic materials 0.000 claims abstract description 3
- 229910052703 rhodium Inorganic materials 0.000 claims abstract description 3
- 229910052707 ruthenium Inorganic materials 0.000 claims abstract description 3
- 229910052742 iron Inorganic materials 0.000 claims abstract 2
- 229910052763 palladium Inorganic materials 0.000 claims abstract 2
- 238000003860 storage Methods 0.000 claims description 21
- WGLPBDUCMAPZCE-UHFFFAOYSA-N Trioxochromium Chemical compound O=[Cr](=O)=O WGLPBDUCMAPZCE-UHFFFAOYSA-N 0.000 claims description 18
- 229910000423 chromium oxide Inorganic materials 0.000 claims description 17
- 239000011651 chromium Substances 0.000 claims description 16
- 239000000203 mixture Substances 0.000 claims description 15
- 239000010937 tungsten Substances 0.000 claims description 13
- 150000002739 metals Chemical class 0.000 claims description 5
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims description 4
- 229910052593 corundum Inorganic materials 0.000 claims description 4
- 229910001845 yogo sapphire Inorganic materials 0.000 claims description 4
- 229910001930 tungsten oxide Inorganic materials 0.000 claims description 2
- 229910000287 alkaline earth metal oxide Inorganic materials 0.000 claims 1
- 229910000487 osmium oxide Inorganic materials 0.000 claims 1
- 230000000737 periodic effect Effects 0.000 claims 1
- 239000011159 matrix material Substances 0.000 abstract description 6
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 abstract description 5
- 239000011733 molybdenum Substances 0.000 abstract description 5
- 238000010438 heat treatment Methods 0.000 abstract 1
- 239000000654 additive Substances 0.000 description 8
- 230000000996 additive effect Effects 0.000 description 5
- 238000005245 sintering Methods 0.000 description 4
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 3
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 3
- 238000000034 method Methods 0.000 description 2
- 239000010948 rhodium Substances 0.000 description 2
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 1
- KJTLSVCANCCWHF-UHFFFAOYSA-N Ruthenium Chemical compound [Ru] KJTLSVCANCCWHF-UHFFFAOYSA-N 0.000 description 1
- 230000032683 aging Effects 0.000 description 1
- 229910017052 cobalt Inorganic materials 0.000 description 1
- 239000010941 cobalt Substances 0.000 description 1
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 description 1
- 238000005470 impregnation Methods 0.000 description 1
- GKOZUEZYRPOHIO-UHFFFAOYSA-N iridium atom Chemical compound [Ir] GKOZUEZYRPOHIO-UHFFFAOYSA-N 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- QGLKJKCYBOYXKC-UHFFFAOYSA-N nonaoxidotritungsten Chemical compound O=[W]1(=O)O[W](=O)(=O)O[W](=O)(=O)O1 QGLKJKCYBOYXKC-UHFFFAOYSA-N 0.000 description 1
- YXIFBDPASYPBNG-UHFFFAOYSA-N osmium tungsten Chemical compound [W].[Os] YXIFBDPASYPBNG-UHFFFAOYSA-N 0.000 description 1
- 239000004482 other powder Substances 0.000 description 1
- 238000003825 pressing Methods 0.000 description 1
- WUAPFZMCVAUBPE-UHFFFAOYSA-N rhenium atom Chemical compound [Re] WUAPFZMCVAUBPE-UHFFFAOYSA-N 0.000 description 1
- MHOVAHRLVXNVSD-UHFFFAOYSA-N rhodium atom Chemical compound [Rh] MHOVAHRLVXNVSD-UHFFFAOYSA-N 0.000 description 1
- 150000003326 scandium compounds Chemical class 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
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Classifications
-
- 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
- the present invention relates to a supply cathode according to the preamble of claim 1.
- Storage cathodes are also referred to as matrix cathodes or dispenser cathodes. They generally consist of a storage body which is pressed or sintered from a metal powder and which is impregnated with the actual emission material. Metals such as tungsten and molybdenum are particularly suitable as metal powder for the storage body. It is also known to use mixtures of such metal powders. From DE-OS 20 48 224 it is known to press the storage body into a cavity in a cathode sleeve. From DE-OS 41 14 856 it is For example, it is known to build up the storage body in layers. The porous matrix body can be impregnated with an emission material which consists, for example, of BaO-CaO-Al2O3, by impregnation, melting or the like.
- MM cathodes mixed metal cathodes
- the stock bodies of mixed metal cathodes generally consist of metals from a first group, such as tungsten, chromium or molybdenum, and metals from a second group, such as iron (Fe), cobalt (Co), nickel (Ni), ruthenium (Ru), rhodium (Rh ), Paladium (Pd), Rhenium (Re), Osmium (Os), Iridium (Ir), Platinum (Pt).
- a first group such as tungsten, chromium or molybdenum
- metals from a second group such as iron (Fe), cobalt (Co), nickel (Ni), ruthenium (Ru), rhodium (Rh ), Paladium (Pd), Rhenium (Re), Osmium (Os), Iridium (Ir), Platinum (Pt).
- the emissivity of the cathodes can be improved by adding scandium compounds in the cathode body or in the emission material.
- scandium compounds in the cathode body or in the emission material.
- scandium compounds in the cathode body or in the emission material.
- the present invention is therefore based on the object of improving a storage cathode of the type mentioned at the outset, in particular with regard to electron emission (high current density) with a long service life.
- FIG. 1 schematically shows the structure of a supply cathode with an emission surface 6.
- the cathode body 1 which can also consist of two or three layers, is e.g. by pressing a powder mixture (e.g. W + Os + Cr2O3) into the cathode holder 2 (e.g. made of molybdenum). After sintering, the material is filled with the emission material (e.g. BaO + CaO + Al2O3) e.g. by watering.
- a powder mixture e.g. W + Os + Cr2O3
- the emission material e.g. BaO + CaO + Al2O
- the heater 3 is e.g. with Al2O3 4 embedded in a pot 5 made of molybdenum, which is attached to the cathode holder 2.
- FIG. 2 shows the electron work function (e ⁇ / eV), the value of which was determined from (current measured at 1000 o C) current-voltage characteristics according to known methods, as a function of the cathode temperature (T in o C).
- the work function for cathodes with Cr2O3 addition is low temperatures about 0.1 eV lower than for cathodes without additives, at high temperatures about 0.05 eV.
- FIG. 3 shows the change in work function (e ⁇ / eV) (for 1000 o C) during operation with (to accelerate aging) increased temperature (1100 o C) over the operating time in hours (h).
- the work function for cathodes with Cr2O3 additive drops somewhat at the beginning of operation and remains practically constant during the observation period (almost 10,000 hours).
- the work function for cathodes without additives increases, so that after 1000 hours their value is about 0.1 eV higher than for cathodes with Cr2O3.
- FIG. 4 shows, as an example of the size of the current that can be achieved, the change over time in the saturation current (current density j in A / cm 2) at a field strength of 35 kV / cm over the operating time t (h).
- the saturation current behaves according to the work function (FIG. 3); it changes less for cathodes with Cr203 addition than for those without addition. After a long period of operation (in the example, almost 10,000 hours at 1100 o C), the saturation current for cathodes with Cr203 addition is still about twice as large as the current for cathodes without addition. (Both types show practically no waste at low temperatures).
- the chromium or chromium oxide additive is added to the sintered body of the cathode body. This is advantageously done in such a way that the powder or metals of the first group and the second group powdered chromium oxide (Cr203) is mixed, this mixture is then pressed and is then sintered into a porous sintered body.
- the chromium oxide content of the powder mixture is 1-20% by weight, preferably 7-14% by weight, in particular approximately 10% by weight.
- the other powder fractions preferably consist of tungsten and osmium, the tungsten fraction expediently not to be smaller than the osmium fraction.
- the metal of the second group for example osmium, can be dispensed with entirely.
- the chromium or the chromium oxide is not added to the powder mixture for the sintered body, but rather to the emission material, likewise prepared as a powder mixture, with which the porous sintered body is then impregnated.
- the sintered body does not have to contain chromium or chromium oxide.
- Metallic chromium or chromium oxide can be added to the emission material. Chromium is expediently added in proportions of 1-12% by weight, preferably 4-10% by weight, in particular 6-8% by weight. Chromium oxide is expediently added in proportions of 2-18% by weight, preferably 5-15% by weight, in particular 8-12% by weight.
- the chromium content of the emission material should be chosen to be lower.
- the basic matrix, that is the sintered body suitably consists of a tungsten-osmium mixture with a possibly very low osmium content.
- the chromium additive according to the invention is particularly advantageous for use with a storage cathode, the storage body consists of several superimposed and sintered sintered layers, as described for example in DE-OS 41 14 856 A1.
- the layer sintering described there consists of at least two layers which consist of essentially the same materials. However, the percentage by weight of the materials differs in at least two adjacent layers in such a way that in one layer the proportion of the metal of the first group is greater than the proportion of the metal in the second group and in the other layer the proportion of the metal in the second group is greater than the proportion of metal in the first group.
- chromium or chromium oxide should be present at least in the layer having the emission surface 6, wherein the chromium oxide or chromium can either be contained in the sintered body or, if appropriate, the layers can only be introduced with the emission material .
- Such a supply cathode is preferably produced with a multilayer cathode body using a method known from DE-OS 4 114 856, in which the sintered body is produced with an additional layer and this additional layer is removed again after sintering.
- FIG. 5 shows in the right half a cross section through a sintered body with a first layer 11, a second layer 12 and a third layer 13 in a cathode holder 2.
- the first layer is essentially composed of a metal powder mixture of more than 50% by weight, preferably more produced as 70% by weight of tungsten and the rest of osmium.
- the third layer 13 is preferably composed in exactly the same way as the first layer.
- the second layer 12 is produced from a mixture of tungsten metal powder, osmium metal powder and approximately 10% by weight of chromium oxide powder, the content of osmium being higher than in layers 11 and 13 and preferably more than 50% by weight. is.
- the various powder mixtures are successively filled into the cathode holder, pressed under high pressure and sintered together.
- the third layer 13 and part of the second layer 12 up to the broken line are removed after sintering, e.g. by grinding, so that a two-layer cathode body sketched in the left half of FIG. 5 is formed with the emission surface 6 forming the exposed surface of the second layer.
- the metal matrix is preferably filled (impregnated) with the emission material before the third and part of the second layer are removed.
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- Solid Thermionic Cathode (AREA)
- Powder Metallurgy (AREA)
Abstract
Description
Die vorliegende Erfindung betrifft eine Vorratskathode nach dem Oberbegriff des Patentanspruches 1.The present invention relates to a supply cathode according to the preamble of
Vorratskathoden werden auch als Matrix-Kathoden oder Dispenser-Kathoden bezeichnet. Sie bestehen im allgemeinen aus einem Vorratskörper, der aus einem Metallpulver gepreßt oder gesintert ist und der mit dem eigentlichen Emissionsmaterial imprägniert ist. Als Metallpulver für den Vorratskörper kommen insbesondere Metalle wie Wolfram und Molybdän in Frage. Es ist auch bekannt, Mischungen solcher Metallpulver zu verwenden. Aus der DE-OS 20 48 224 ist es bekannt, den Vorratskörper in eine Höhlung einer Kathodenhülse einzupressen. Aus der DE-OS 41 14 856 ist es z.B. bekannt, den Vorratskörper schichtförmig aufzubauen. Die Imprägnierung des porösen Matrix-Körpers mit einem Emissionsmaterial, das z.B. aus BaO-CaO-Al₂O₃ besteht, kann durch Tränken, Einschmelzen oder dergleichen erfolgen.Storage cathodes are also referred to as matrix cathodes or dispenser cathodes. They generally consist of a storage body which is pressed or sintered from a metal powder and which is impregnated with the actual emission material. Metals such as tungsten and molybdenum are particularly suitable as metal powder for the storage body. It is also known to use mixtures of such metal powders. From DE-OS 20 48 224 it is known to press the storage body into a cavity in a cathode sleeve. From DE-OS 41 14 856 it is For example, it is known to build up the storage body in layers. The porous matrix body can be impregnated with an emission material which consists, for example, of BaO-CaO-Al₂O₃, by impregnation, melting or the like.
Allgemein hat sich gezeigt, daß sogenannte Mischmetall-Kathoden (MM-Kathoden), d.h. also Kathoden, deren Vorratskörper aus einem Metallpulvergemisch gepreßt und gesintert sind, verbesserte Emissionseigenschaften und eine bessere Stromstabilität aufweisen. Die Vorratskörper von Mischmetall-Kathoden bestehen im allgemeinen aus Metallen einer ersten Gruppe wie Wolfram, Chrom oder Molybdän und Metallen einer zweiten Gruppe, wie Eisen (Fe), Kobalt (Co), Nickel (Ni), Ruthenium (Ru), Rhodium (Rh), Paladium (Pd), Rhenium (Re), Osmium (Os), Iridium (Ir), Platin (Pt).In general, it has been shown that so-called mixed metal cathodes (MM cathodes), i.e. that is, cathodes whose storage bodies are pressed and sintered from a metal powder mixture, have improved emission properties and better current stability. The stock bodies of mixed metal cathodes generally consist of metals from a first group, such as tungsten, chromium or molybdenum, and metals from a second group, such as iron (Fe), cobalt (Co), nickel (Ni), ruthenium (Ru), rhodium (Rh ), Paladium (Pd), Rhenium (Re), Osmium (Os), Iridium (Ir), Platinum (Pt).
Aus der DE-PS 30 17 429 ist weiterhin bekannt, Wolfram oder Wolframoxid dem Emissionsmaterial zuzusetzen.From DE-PS 30 17 429 it is also known to add tungsten or tungsten oxide to the emission material.
Weiter ist bekannt, daß durch Zusatz von Scandium-Verbindungen im Kathodenkörper oder im Emissionsmaterial die Emissionsfähigkeit der Kathoden verbessert werden kann. Allerdings sind die Langzeit-Eigenschaften dieser sogenannten "Scandat-Kathoden" bisher noch nicht befriedigend.It is also known that the emissivity of the cathodes can be improved by adding scandium compounds in the cathode body or in the emission material. However, the long-term properties of these so-called "scandate cathodes" have so far not been satisfactory.
Der vorliegenden Erfindung liegt daher die Aufgabe zugrunde, eine Vorratskathode der eingangs genannten Art insbesondere hinsichtlich der Elektronenemission ( hoher Stromdichte) bei langer Lebensdauer zu verbessern.The present invention is therefore based on the object of improving a storage cathode of the type mentioned at the outset, in particular with regard to electron emission (high current density) with a long service life.
Diese Aufgabe wird durch die im Kennzeichen des Patentanspruches 1 angegebenen Merkmale gelöst.This object is achieved by the features specified in the characterizing part of
Bei Versuchen mit verschiedenen Zusätzen hat sich gezeigt, daß mit einer Beimischung von Cr₂O₃-Pulver insbesondere zum Mischmetall-Pulver Kathoden mit merklich verbesserten Emissionseigenschaften erhalten werden können. Insbesondere bei Vorratskathoden mit einem Vorratskörper in Schichtaufbau wie z.B. in der DE 41 14 856 A1 beschrieben, konnten bei gleicher Kathodentemperatur eine gegenüber einer Kathode ohne chromhaltigen Zusatz etwa doppelt so große Stromdichten erreicht werden, die sich auch nach längerer Betriebszeit kaum änderten. Entsprechend ist die Austrittsarbeit ( für 1000oC) bei Kathoden mit z.B. 10% Cr₂O₃-Zusatz zu einem W/Os-Pulver um etwa 0,1 eV niedriger als bei den Kathoden ohne Zusatz.Experiments with various additives have shown that with an admixture of Cr₂O₃ powder, in particular to the mixed metal powder, cathodes with noticeably improved emission properties can be obtained. Particularly in the case of storage cathodes with a storage body in a layered structure, as described, for example, in DE 41 14 856 A1, at the same cathode temperature it was possible to achieve a current density which was about twice as large as that of a cathode without an addition containing chromium and which hardly changed even after a long operating time. Correspondingly, the work function (for 1000 o C) for cathodes with, for example, 10% Cr₂O₃ addition to a W / Os powder is about 0.1 eV lower than for the cathodes without addition.
Anhand der Figuren wird die Erfindung nachfolgend näher erklärt.
- FIG. 1
- zeigt schematisch einen Querschnitt durch eine Vorratskathode dessen Kathodenkörper auch aus zwei oder drei übereinanderliegenden Schichten bestehen kann.
- FIG. 2
- zeigt eine Kurve der Austrittsarbeit in Abhängigkeit von der Kathodentemperatur für eine Mischmetallkathode (W/Os) mit und ohne chromhaltigen Zusatz (vor Lebensdauer-Betrieb).
- FIG. 3
- zeigt eine Kurve der Austrittsarbeit bei 1000oC in Abhängigkeit von der Betriebszeit bei erhöhter Kathodentemperatur (1100oC) für Mischmetallkathoden (W/Os) mit und ohne chromhaltigen Zusatz.
- FIG. 4
- zeigt eine Kurve des Sättigungsstroms für 35 kV/cm in Abhängigkeit von der Betriebszeit für Mischmetallkathoden (W/Os) mit und ohne chromhaltigen Zusatz.
- FIG. 5
- zeigt schematisch einen Querschnitt durch einen Kathodenkörper mit zwei Schichten und dessen Herstellung aus einem dreischichtigen Sinterkörper.
- FIG. 1
- shows schematically a cross section through a supply cathode whose cathode body can also consist of two or three layers lying one above the other.
- FIG. 2nd
- shows a curve of the work function as a function of the cathode temperature for a mixed metal cathode (W / Os) with and without an addition containing chromium (before service life).
- FIG. 3rd
- shows a curve of the work function at 1000 o C as a function of the operating time at elevated cathode temperature (1100 o C) for mixed metal cathodes (W / Os) with and without chromium-containing additive.
- FIG. 4th
- shows a curve of the saturation current for 35 kV / cm as a function of the operating time for mixed metal cathodes (W / Os) with and without chromium-containing additive.
- FIG. 5
- shows schematically a cross section through a cathode body with two layers and its production from a three-layer sintered body.
FIG. 1 zeigt schematisch den Aufbau einer Vorratskathode mit einer Emissionsfläche 6. Der Kathodenkörper 1 der auch aus zwei oder drei Schichten bestehen kann, wird z.B. durch Pressen einer Pulvermischung (z.B. W + Os + Cr₂O₃) in den Kathodenhalter 2 (z.B. aus Molybdän) hergestellt. Nach dem Sintern erfolgt das Füllen mit dem Emissionsmaterial (z.B. BaO + CaO + Al₂O₃) z.B. durch Tränken.FIG. 1 schematically shows the structure of a supply cathode with an
Der Heizer 3 wird z.B. mit Al₂O₃ 4 in einen Topf 5 aus Molybdän eingebettet, der an dem Kathodenhalter 2 befestigt ist.The heater 3 is e.g. with
FIG. 2 zeigt die Elektronen-Austrittsarbeit (eΦ/eV), deren Wert aus (bei 1000oC gemessenen) Strom-Spannungs-Kennlinien nach bekannten Verfahren ermittelt wurde, in Abhängigkeit von der Kathoden-Temperatur (T in oC).FIG. 2 shows the electron work function (eΦ / eV), the value of which was determined from (current measured at 1000 o C) current-voltage characteristics according to known methods, as a function of the cathode temperature (T in o C).
Bei neu hergestellten Kathoden (sehr kurze Betriebszeit) ist die Austrittsarbeit für Kathoden mit Cr₂O₃-Zusatz bei tiefen Temperaturen etwa 0,1 eV niedriger als für Kathoden ohne Zusatz, bei hohen Temperaturen noch etwa 0,05 eV.With newly manufactured cathodes (very short operating time), the work function for cathodes with Cr₂O₃ addition is low temperatures about 0.1 eV lower than for cathodes without additives, at high temperatures about 0.05 eV.
FIG. 3 zeigt die Änderung der Austrittsarbeit (eΦ/eV) (für 1000oC) während des Betriebs mit (zur Beschleunigung der Alterung) erhöhter Temperatur (1100oC) über der Betriebszeit in Stunden (h). Die Austrittsarbeit für Kathoden mit Cr₂O₃-Zusatz fällt am Anfang des Betriebs noch etwas ab und bleibt während der Beobachtungszeit (fast 10 000 Stunden) praktisch konstant. Die Austrittsarbeit für Kathoden ohne Zusatz steigt an, sodaß nach 1000 Stunden ihr Wert etwa 0,1 eV höher liegt als bei Kathoden mit Cr₂O₃.FIG. 3 shows the change in work function (eΦ / eV) (for 1000 o C) during operation with (to accelerate aging) increased temperature (1100 o C) over the operating time in hours (h). The work function for cathodes with Cr₂O₃ additive drops somewhat at the beginning of operation and remains practically constant during the observation period (almost 10,000 hours). The work function for cathodes without additives increases, so that after 1000 hours their value is about 0.1 eV higher than for cathodes with Cr₂O₃.
FIG. 4 zeigt als Beispiel für die Größe des erreichbaren Stroms die zeitliche Änderung des Sättigungsstroms (Stromdichte j in A/cm²) bei einer Feldstärke von 35 kV/cm über der Betriebszeit t(h). Entsprechend zur Austrittsarbeit (FIG. 3) verhält sich der Sättigungsstrom; er ändert sich für Kathoden mit Cr₂0₃-Zusatz weniger als für solche ohne Zusatz. Nach längerer Betriebszeit (im Beispiel fast 10000 Stunden bei 1100oC) ist der Sättigungs-Strom für Kathoden mit Cr₂0₃-Zusatz noch etwa doppelt so groß wie der Strom bei Kathoden ohne Zusatz. (Bei tiefer Temperatur zeigen beide Typen praktisch keinen Abfall).FIG. 4 shows, as an example of the size of the current that can be achieved, the change over time in the saturation current (current density j in A / cm 2) at a field strength of 35 kV / cm over the operating time t (h). The saturation current behaves according to the work function (FIG. 3); it changes less for cathodes with Cr₂0₃ addition than for those without addition. After a long period of operation (in the example, almost 10,000 hours at 1100 o C), the saturation current for cathodes with Cr₂0₃ addition is still about twice as large as the current for cathodes without addition. (Both types show practically no waste at low temperatures).
Bei einem vorteilhaften Ausführungsbeispiel wird der Chrom- bzw. der Chromoxidzusatz dem Sinterkörper des Kathodenkörpers zugesetzt. Dies geschieht zweckmäßig in der Weise, daß dem oder den Pulvern der Metalle der ersten Gruppe und der zweiten Gruppe pulverförmiges Chromoxid (Cr₂0₃) zugemischt wird, diese Mischung dann gepreßt und dann zu einem porösen Sinterkörper gesintert wird. Der Chromoxidanteil der Pulvermischung beträgt 1-20 Gew.%, vorzugsweise 7-14 Gew.%, insbesondere etwa 10 Gew.%. Bevorzugt bestehen die anderen Pulveranteile aus Wolfram und Osmium, wobei der Wolframanteil zweckmäßig nicht kleiner sein soll, als der Osmiumanteil. Gegebenenfalls kann auf das Metall der zweiten Gruppe, also z.B. Osmium, ganz verzichtet werden.In an advantageous embodiment, the chromium or chromium oxide additive is added to the sintered body of the cathode body. This is advantageously done in such a way that the powder or metals of the first group and the second group powdered chromium oxide (Cr₂0₃) is mixed, this mixture is then pressed and is then sintered into a porous sintered body. The chromium oxide content of the powder mixture is 1-20% by weight, preferably 7-14% by weight, in particular approximately 10% by weight. The other powder fractions preferably consist of tungsten and osmium, the tungsten fraction expediently not to be smaller than the osmium fraction. If necessary, the metal of the second group, for example osmium, can be dispensed with entirely.
Bei einem weiteren Ausführungsbeispiel wird das Chrom bzw. das Chromoxyd nicht dem Pulvergemisch für den Sinterkörper zugemischt, sondern dem ebenfalls als Pulvermischung aufbereiteten Emissionsmaterial, mit dem dann der poröse Sinterkörper getränkt wird, beigemischt. Der Sinterkörper muß in diesem Falle kein Chrom- oder Chromoxyd enthalten. Dem Emissionsmaterial kann metallisches Chrom oder Chromoxyd zugesetzt werden. Chrom wird zweckmäßig in Anteilen von 1-12 Gew.% vorzugsweise 4-10 Gew.% insbesondere 6-8 Gew.% zugesetzt. Chromoxid wird zweckmäßig in Anteilen von 2-18 Gew.%, vorzugsweise 5-15 Gew.%, insbesondere 8-12 Gew.% zugesetzt.In a further exemplary embodiment, the chromium or the chromium oxide is not added to the powder mixture for the sintered body, but rather to the emission material, likewise prepared as a powder mixture, with which the porous sintered body is then impregnated. In this case, the sintered body does not have to contain chromium or chromium oxide. Metallic chromium or chromium oxide can be added to the emission material. Chromium is expediently added in proportions of 1-12% by weight, preferably 4-10% by weight, in particular 6-8% by weight. Chromium oxide is expediently added in proportions of 2-18% by weight, preferably 5-15% by weight, in particular 8-12% by weight.
Sollte der Sinterkörper bereits schon einen gewissen Chromoxidanteil aufweisen, so ist die Chromhaltigkeit des Emissionsmaterials geringer zu wählen. Die Grundmatrix, das ist der Sinterkörper, besteht zweckmäßig aus einem Wolfram-Osmiumgemisch mit ggf. sehr niedrigem Osmiumgehalt.If the sintered body already contains a certain amount of chromium oxide, the chromium content of the emission material should be chosen to be lower. The basic matrix, that is the sintered body, suitably consists of a tungsten-osmium mixture with a possibly very low osmium content.
Der erfindungsgemäße Chromzusatz ist besonders vorteilhaft bei einer Vorratskathode anzuwenden, deren Vorratskörper aus mehreren übereinanderliegenden und zusammengesinterten Sinterschichten besteht, wie sie z.B. in der DE-OS 41 14 856 A1 beschrieben ist. Der dort beschriebene Schichtsinterling besteht mindestens aus zwei Schichten, die aus im wesentlichen gleichen Materialien bestehen. Der gewichtsprozentuale Anteil der Materialien ist jedoch in wenigstens zwei aneinandergrenzenden Schichten unterschiedlich und zwar in der Weise, daß in der einen Schicht der Anteil des Metalles der ersten Gruppe größer ist als der Anteil des Metalles der zweiten Gruppe und in der anderen Schicht der Anteil des Metalles der zweiten Gruppe größer ist als der Anteil des Metalles der ersten Gruppe. Auch bei einem solchen Kathodenkörper mit geschichtetem Sinterling soll zumindest in der die Emissionsoberfläche 6 aufweisenden Schicht Chrom- bzw. Chromoxid vorhanden sein, wobei das Chromoxid bzw. Chrom entweder im Sinterling enthalten sein kann oder ggf. auch erst mit dem Emissionsmaterial die Schichten eingebracht werden kann.The chromium additive according to the invention is particularly advantageous for use with a storage cathode, the storage body consists of several superimposed and sintered sintered layers, as described for example in DE-OS 41 14 856 A1. The layer sintering described there consists of at least two layers which consist of essentially the same materials. However, the percentage by weight of the materials differs in at least two adjacent layers in such a way that in one layer the proportion of the metal of the first group is greater than the proportion of the metal in the second group and in the other layer the proportion of the metal in the second group is greater than the proportion of metal in the first group. Even with such a cathode body with a layered sintered body, chromium or chromium oxide should be present at least in the layer having the
Vorzugsweise wird eine solche Vorratskathode mit einem mehrschichtigen Kathodenkörper unter Anwendung eines aus der DE-OS 4 114 856 bekannten Verfahrens hergestellt, bei welchem der Sinterkörper mit einer zusätzlichen Schicht hergestellt wird und diese zusätzliche Schicht nach dem Sintern wieder entfernt wird.Such a supply cathode is preferably produced with a multilayer cathode body using a method known from
FIG. 5 zeigt in der rechten Hälfte einen Querschnitt durch einen Sinterkörper mit einer ersten Schicht 11, einer zweiten Schicht 12 und einer dritten Schicht 13 in einem Kathodenhalter 2. Die erste Schicht ist im wesentlichen aus einem Metallpulvergemisch von mehr als 50 Gew.%, vorzugsweise mehr als 70 Gew.% Wolfram und Rest Osmium hergestellt. Die dritte Schicht 13 ist vorzugsweise genauso zusammengesetzt wie die erste Schicht. Die zweite Schicht 12 ist hergestellt aus einem Gemisch von Wolfram-Metallpulver, Osmium-Metallpulver und ca. 10 Gew.% Chromoxid-Pulver, wobei der Gehalt von Osmium höher ist als in den Schichten 11 und 13 und vorzugsweise mehr als 50 Gew.% beträgt. Die verschiedenen Pulvermischungen werden nacheinander in den Kathodenhalter eingefüllt, unter hohem Druck gepreßt und gemeinsam gesintert.FIG. 5 shows in the right half a cross section through a sintered body with a
Die dritte Schicht 13 und ein Teil der zweiten Schicht 12 bis zu der unterbrochenen Linie werden nach dem Sintern entfernt, z.B. durch Schleifen, so daß ein in der linken Hälfte der Fig. 5 skizzierter zweischichtiger Kathodenkörper mit der die freiliegende Oberfläche der zweiten Schicht bildenden Emissionsoberfläche 6 entsteht. Die Füllung (Imprägnierung) der Metall-Matrix mit dem Emissionsmaterial erfolgt vorzugsweise vor dem Entfernen der dritten und des Teils der zweiten Schicht.The
Claims (14)
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE4408941A DE4408941A1 (en) | 1994-03-16 | 1994-03-16 | Supply cathode |
| DE4408941 | 1994-03-16 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| EP0673051A1 true EP0673051A1 (en) | 1995-09-20 |
| EP0673051B1 EP0673051B1 (en) | 1997-08-13 |
Family
ID=6512957
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP95103216A Expired - Lifetime EP0673051B1 (en) | 1994-03-16 | 1995-03-07 | Dispenser cathode |
Country Status (4)
| Country | Link |
|---|---|
| US (1) | US5594299A (en) |
| EP (1) | EP0673051B1 (en) |
| JP (1) | JPH07272614A (en) |
| DE (2) | DE4408941A1 (en) |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| RU2138877C1 (en) * | 1997-08-12 | 1999-09-27 | Институт металлургии им.А.А.Байкова РАН | Material of thermal emitter for surface ionization of organic compounds in air and method of its activation |
| US6054801A (en) * | 1998-02-27 | 2000-04-25 | Regents, University Of California | Field emission cathode fabricated from porous carbon foam material |
| RU2176833C1 (en) * | 2000-11-30 | 2001-12-10 | Закрытое акционерное общество Научно-производственный центр "СОЛИТОН-НТТ" | Electrode material for low-temperature plasma generator |
| RU2260869C1 (en) * | 2004-04-12 | 2005-09-20 | Капустин Владимир Иванович | Heated emitter material for surface ionization of organic compounds in the open and heated emitter activation process |
| WO2006115428A1 (en) * | 2005-04-27 | 2006-11-02 | Vladimir Ivanovich Kapustin | Thermoemitter material for surface ionisation of organic compounds in the air and method for activating a thermoemitter |
| GB2567853B (en) | 2017-10-26 | 2020-07-29 | Isotopx Ltd | Gas-source mass spectrometer comprising an electron source |
| CN116511519A (en) * | 2023-04-10 | 2023-08-01 | 中国电子科技集团公司第十二研究所 | Chromium-containing emission active material for film-coated diffusion cathode, preparation method and application thereof |
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|---|---|---|---|---|
| FR1114163A (en) * | 1953-11-28 | 1956-04-09 | Siemens Ag | electron emitting electrode |
| US2995674A (en) * | 1959-02-27 | 1961-08-08 | Raytheon Co | Impregnated cathodes |
| US3155864A (en) * | 1960-03-21 | 1964-11-03 | Gen Electric | Dispenser cathode |
| EP0282040A1 (en) * | 1987-03-10 | 1988-09-14 | Siemens Aktiengesellschaft | Dispenser cathode, especially metal capillary cathode, for electric discharge vessels |
| EP0299126A1 (en) * | 1987-07-13 | 1989-01-18 | Syracuse University | Impregnated thermionic cathode |
| EP0322304A1 (en) * | 1987-12-23 | 1989-06-28 | Thomson-Csf | Method of manufacturing an impregnated cathode, and cathode manufactured according to this method |
| DE4114856A1 (en) * | 1991-05-07 | 1992-11-12 | Licentia Gmbh | STOCK CATHODE AND METHOD FOR THE PRODUCTION THEREOF |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3017429A1 (en) * | 1980-05-07 | 1981-11-12 | Licentia Patent-Verwaltungs-Gmbh, 6000 Frankfurt | Emission material for impregnating electron tube cathode - with porous sintered matrix, contains aluminium, barium, calcium, strontium and opt. tungsten |
| US4417173A (en) * | 1980-12-09 | 1983-11-22 | E M I-Varian Limited | Thermionic electron emitters and methods of making them |
| DE3122950A1 (en) * | 1981-06-10 | 1983-01-05 | Licentia Patent-Verwaltungs-Gmbh, 6000 Frankfurt | Process for fabricating a dispenser cathode |
| US5019752A (en) * | 1988-06-16 | 1991-05-28 | Hughes Aircraft Company | Plasma switch with chrome, perturbated cold cathode |
| KR910003698B1 (en) * | 1988-11-11 | 1991-06-08 | Samsung Electronic Devices | Cavity reservoir type dispenser cathode and method of the same |
| KR920009849B1 (en) * | 1990-12-28 | 1992-10-31 | 주식회사 금성사 | Method of manufacturing an impregnated cathode |
| KR930007461B1 (en) * | 1991-04-23 | 1993-08-11 | 주식회사 금성사 | Method of making a dispenser type cathode |
-
1994
- 1994-03-16 DE DE4408941A patent/DE4408941A1/en not_active Withdrawn
-
1995
- 1995-03-07 DE DE59500487T patent/DE59500487D1/en not_active Expired - Lifetime
- 1995-03-07 EP EP95103216A patent/EP0673051B1/en not_active Expired - Lifetime
- 1995-03-09 US US08/401,728 patent/US5594299A/en not_active Expired - Lifetime
- 1995-03-15 JP JP5625295A patent/JPH07272614A/en active Pending
Patent Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR1114163A (en) * | 1953-11-28 | 1956-04-09 | Siemens Ag | electron emitting electrode |
| US2995674A (en) * | 1959-02-27 | 1961-08-08 | Raytheon Co | Impregnated cathodes |
| US3155864A (en) * | 1960-03-21 | 1964-11-03 | Gen Electric | Dispenser cathode |
| EP0282040A1 (en) * | 1987-03-10 | 1988-09-14 | Siemens Aktiengesellschaft | Dispenser cathode, especially metal capillary cathode, for electric discharge vessels |
| EP0299126A1 (en) * | 1987-07-13 | 1989-01-18 | Syracuse University | Impregnated thermionic cathode |
| EP0322304A1 (en) * | 1987-12-23 | 1989-06-28 | Thomson-Csf | Method of manufacturing an impregnated cathode, and cathode manufactured according to this method |
| DE4114856A1 (en) * | 1991-05-07 | 1992-11-12 | Licentia Gmbh | STOCK CATHODE AND METHOD FOR THE PRODUCTION THEREOF |
Also Published As
| Publication number | Publication date |
|---|---|
| EP0673051B1 (en) | 1997-08-13 |
| DE4408941A1 (en) | 1995-09-21 |
| US5594299A (en) | 1997-01-14 |
| JPH07272614A (en) | 1995-10-20 |
| DE59500487D1 (en) | 1997-09-18 |
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