# US 4,393,328 A · Hot cathode, its production process and electron tube incorporating such a cathode

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- Number: US 4,393,328 A
- Document ID: US4393328A
- Status: Granted
- Kind: A
- Application number: 06/204,176
- Filed: 1980-11-05
- Granted: 1983-07-12
- Earliest claimed: 1979-11-09
- Assignees: Thomson-CSF
- Inventors: Arvind Shroff; Pierre Palluel
- Web page: https://patentgrep.com/patent/US4393328A

## CPC

- H01J 9/04: of thermionic cathodes
- H01J 1/14: characterised by the material
- H01J 23/04: Cathodes
- H01J: ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS (spark-gaps H01T; electric arc lamps H05B31/00; particle accelerators H05H)

## Abstract

The hot cathode, according to the invention, is constituted by a fritted matrix 1 and a heating filament 4, said matrix being formed from a powder mixture 2 of tungsten and another high work function refractory metal and covered with a high work function refractory metal film 3. FIG. 3.

## Claims

### Claim 1

A process for producing a cathode formed from a matrix of a fritted powder metal impregnated with a barium compound, and a heating filament associated with said matrix, wherein the matrix is formed from a mixture of two metals, tungsten and another high work function refractory metal, and wherein the matrix is covered with a high work function refractory metal film, comprising the following successive stages:
(a) mixing powders of tungsten and another high work function refractory metal
(b) pressing the mixture between 7 and 10 t/cm.sup.2
(c) prefritting under hydrogen at between 1100.degree. and 1300.degree. CB for approximately 12 h
(d) fritting in vacuo at a temperature between 1850 and
(e) impregnation with calcium and barium aluminates
(f) elimination of the excess aluminate present on the surface by a chemical process
(g) deposition of the high work function refractory metal film.

### Claim 2 (depends on 1)

A process according to claim 1 wherein said high work function refractory metal is selected from the group comprising iridium, osmium, ruthenium, and rhenium.

### Claim 3 (depends on 1)

A process according to claim 1 wherein the deposition is by cathodic sputtering.

### Claim 4 (depends on 1)

A process according to claim 1 wherein the deposition is by evaporation.