DE1265876B - Oxide cathode and process for its manufacture - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. Cl .:

HOIj

German class: 21g-13/03

Number: 1265 876

File number: L 52334 VIII c / 21 g

Filing date: December 8, 1965

Open date: April 11, 1968

The invention relates to an oxide cathode, which consists of a carrier made of noble metal and a sintered one emitting metal oxide layer.

Cathodes are already used in ionization manometer tubes with a precious metal core, which preferably consists of iridium, an emission layer, e.g. B. from thorium oxide, sintered is. This known combination of a noble metal core with a sintered layer of the metal oxide however, supplies base metal as an emission layer given temperature, a specific emission that is insufficient for various applications. The specific emission of such a cathode is determined firstly by the effective surface of the emitting Systems, d. H. essentially by the amount of oxide applied and, secondly, by the chemical Limited condition of this oxide layer. Since there is only one on a smooth precious metal core surface small amount of oxide can be built up stably, with an interaction between the noble metal ao and the oxide is negligible, the specific emission of such a system cannot exceed limits given by the arrangement can be increased.

It has also been proposed to use a core made of refractory metal, for example tungsten or molybdenum, an intermediate layer of zirconium or titanium, with the outer layer consists of thorium oxide. Here, as in other designs, the intermediate layer is used Lowering the reduction temperature or increasing the mechanical connection of the core with the emission layer.

The invention is based on the object of providing an oxide cathode which is insensitive to air and has an increased to create specific emissions. The invention consists in that on the carrier made of noble metal and a layer of the metal whose oxide forms the emission layer is sintered under the metal oxide layer. With such a structure, there is a substantial increase in the effective surface, and it becomes a stable installation of a relatively large amount of oxide in conjunction with a noble metal core is achieved. aside from that supports the reactive intermediate layer between the noble metal core and the emitting oxide layer through a chemical interaction between metal and oxide the emission process and causes an increased specific emission of the cathode.

In a preferred embodiment, a thorium layer is sintered onto an iridium core, and the Metal oxide layer contains at least for the most part thorium oxide. Instead of the com-oxide cathode and methods of making them

Applicant:

Leybold-Heraeus G. m. B. H. & Co. K. G.,

5000 Cologne-Bayental, Bonner Str. 504

Named as inventor:

Dr. Heinz Schierholz, 5300 Bonn;

Josef Könne, 5038 Rodenkirchen

Bination of thorium-thorium oxide can also be used by others metals known as emission substances are used. The precious metal core is heated directly or indirectly.

ao The inventive design of the cathode has a significantly larger surface a correspondingly larger emission achieved. In addition, there is an ingress of air - which is easy to Destruction of the system can lead to an additional formation of oxides, which can lead to emissions affects.

To produce such an oxide cathode, it may be useful to sinter the metallic layer onto the noble metal core in a known manner under a protective atmosphere, ie under protective gas or in an inert atmosphere, and then also to sinter the metal oxide layer under a protective atmosphere.
In the drawing, an embodiment of the subject matter of the invention is shown schematically. The directly heated noble metal core 1 can be seen, onto which a metallic layer 2 made of a base metal is sintered. The metallic layer 2 carries a metal oxide layer 3, which consists at least for the most part of the oxide of the base metal of the metallic layer, optionally with the addition of other metal oxides or metallic activators.

Claims (3)

Patent claims: 1. Oxide cathode, which consists of a carrier made of noble metal and a sintered-on emitting Metal oxide layer, characterized in that the carrier (1) consists of Noble metal and under the metal oxide layer (3) a layer (2) of that metal is sintered, whose oxide forms the emission layer. 809 538/420 2. Oxydkathode according to claim 1, characterized in that on an iridium core one Thorium layer (2) is sintered on and that the metal oxide layer (3) is at least predominantly Part contains thorium oxide. 3. A method for producing an oxide cathode according to claim 1 or 2, characterized in that that the metallic layer (2) is sintered onto the noble metal core (1) in a protective atmosphere and that afterwards the sintering of the metal oxide also takes place under a protective atmosphere (3) connects. Considered publications:
German patent specification No. 889 811. 1 sheet of drawings 809 538/420 4.68 © Bundesdruckerei Berlin