DE1039650B - Cathode for discharge tubes and processes for their manufacture - Google Patents

Description

Patent 883,936 relates to a cathode for discharge tubes, whose active substance consists of cesium or rubidium, in which the active substance in one closed container is provided, the wall of which at least at one point of the container made of porous Tungsten is made. On the one hand, this arrangement significantly extends the service life of the cathode, because the active substance diffuses through the pores of the tungsten body only slowly, and on the other hand the work function is greatly reduced because the active substance is on the surface of the tungsten distributed. In the container advantageously made of nickel or another similar metal instead of the pure metallic cesium or rubidium, you can also use a reducible cesium or provide a rubidium compound and a reducing agent.

The improvement according to the invention for such a cathode is that the work function Is further reduced by the fact that between the metallic surface of the sintered, porous Tungsten body and the active metal present on this tungsten body oxides of the active metal and oxides of tungsten are present. The cathode then acts as an oxide cathode.

The oxides are expediently at least partly in a finely divided tungsten powder as a reducing agent embedded.

_{W 2} O ₅ and / or one or more blue tungsten oxides are preferably located on the porous tungsten body. In this description and in the claims, tungsten oxide is _{understood to mean the oxide W 2} O ₅ and the so-called blue oxides that are related to this.

In order to produce a cathode according to the invention, the sintered tungsten body is oxidized before the assembly of the cathode in such a way that tungsten oxide is formed on its surface. After arranging the active substance or its oxides and the reducing agent in the metal container and closing it off with a sintered and oxidized, porous tungsten body, the active alkali metal, i.e. cesium or rubidium, reaches the surface of the tungsten when the cathode is heated. However, since the surface of the tungsten is covered by an oxide layer, this oxide is at least partially reduced by the metallic cesium or rubidium, the active metal itself being partially converted into an oxide. This process continues until a state of equilibrium is reached in which various oxides are intercalated between the metallic tungsten on the one hand and the metallic cesium or rubidium on the other, which act as the work function of the cathode for discharge tubes
and four ways to make them

Addendum to patent 883 936

Applicant:

Egyesält Izzolämpa es Villamossägi
Reszvenytärsasag, Budapest

Representative: Dipl.-Ing. W. Meissner,

Berlin-Grunewald, Herbertstr. 22

and Dipl.-Ing. H. Tischer, Munich 2, patent attorneys

Claimed priority:
Hungary from January 11, 1951

Dipl.-Ing. Ernö Winter, Budapest,
has been named as the inventor

reduce the cathode significantly. The metallic tungsten reduced from the tungsten oxide shows an extremely fine structure, and the alkali metal oxides, i.e. cesium and / or Rubidium oxide are embedded in this tungsten metal, with the metallic cesium or rubidium is present on the outer surface of the oxide layer.

The sintered, porous tungsten body is advantageously in a gas atmosphere consisting of nitrogen and a few tenths of a percent oxygen, advantageously 0.10%, heated at about 600 to 800 ° C, the Oxidation takes place on the surface of the tungsten.

The advantage of the cathode according to the invention does not only consist in the smaller work function Cathodes in which the metallic cesium and / or rubidium are located directly on the metallic Tungsten surface is located, but the temperature resistance of the cathode is also essential better.

Claims (4)

Patent claims: 1. Cathode for discharge tubes, the active substance of which consists of cesium and / or rubidium, the is provided in a closed container, the wall of which at least at one point from a porous tungsten body, according to patent - 809 639/376 883 936, characterized in that between the metallic surface of the porous tungsten body and the active metal present on this tungsten body, oxides of the active metal and oxides of tungsten are present. 2. Cathode according to claim 1 or 2, characterized in that there are on the porous tungsten body W ₂ O ₅ and / or one or more blue tungsten oxides. 3. A method for producing a cathode according to any one of the preceding claims, characterized in that a porous tungsten body is superficially oxidized in such a way that W ₂ O ₅ or a blue tungsten oxide or both arise that then with the oxidized tungsten body of the active substance or its Compound and a reducing agent-containing container is closed and the cathode is heated so that the active substance, passing through the porous body, partly reduces the tungsten oxide, partly oxidizes itself until a state of equilibrium is reached and the remaining metallic active substance is deposited on the oxide layer or embeds itself in this. 4. The method according to claim 3, characterized in that for the purpose of producing the tungsten oxides the porous tungsten body in a nitrogen atmosphere containing a few tenths of a percent oxygen is heated at a temperature of about 600 to 800 ° C. Considered publications: German patent specifications No. 627 176, 662 921,
724142; "Excerpts from German patent applications", Vol. 5, 1948, p. 581, application S148674 VIIIc / 21g; Swiss patent specification No. 181367,241098; British Patent Nos. 374 241, 472 333; »Philips' tech. Rdsch. ”, Vol. 11, 1950, pp. 349 to 358; Herrmann-Wagener: "The Oxide Cathode", 1st part, 2nd edition, Leipzig, 1948, pp. 51 to 53. © 809 639/376 9.5 «