US4570099A
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US
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Thermionic electron emitters
Assignee: E M I-Varian Ltd
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Filing: 1984-10-12
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Granted: 1986-02-11
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Expires: 2004-10-12
Abstract
Abstract A thermionic cathode (FIG. 1) comprises an emitter (3) comprising a matrix (4) of tungsten impregnated with an alkaline earth activator. The matrix is coated with a coating (5) of about 20-30% osmium fully alloyed with tungsten formed by cosputtering osmium and tungsten onto the matrix. A diffusion barrier (6) of osmium may be interposed between the matrix 4 and coating (5) (FIG. 2) and, optionally, osmium may be diffused into the matrix (4). Alternatively the whole matrix may comprise a mixture of about 20-30% osmium fully alloyed with tungsten (FIG. 3). Alternative to osmium and tungsten may be used, and various modifications may be made, and other methods of making the emitter may be used. In particular the proportion of osmium may be about 40%.
Inventors
- 👤 Michael C. Green
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 14:15
CPC Classifications
H; H01; H01J; H01J1/00; H01J1/02; H01J1/13; H01J1/14; H01J9/00; H01J9/02; H01J9/04; H01J9/042; H01J9/047
Claims Analysis
Total Claims: 33
Claim 1
Independent Claim
113 words
A thermionic emitter comprising: a porous body of metal selected from the group consisting of tungsten, molybdenum and alloys thereof; an emissive surface layer of a fully alloyed material being a coating on said porous body; said fully alloyed material consisting solely of 15 to 45% of a first metal selected from the group consisting of osmium, iridium, ruthenium, rhodium, rhenium and alloys thereof, fully alloyed with 85 to 55% of a second metal selected from the group consisting of tungsten, molybdenum and alloys thereof, such that said fully alloyed material has said first metal and said second metal substantially fully interdiffused therein; and, an alkaline earth activator dispersed within said porous body.
Claim 2
Dependent Claim
113 words
A thermionic emitter comprising: a porous body of metal selected from the group consisting of tungsten, molybdenum and alloys thereof; an emissive surface layer of a fully alloyed material being a coating on said porous body; said fully alloyed material consisting solely of 15 to 45% of a first metal selected from the group consisting of osmium, iridium, ruthenium, rhodium, rhenium and alloys thereof, fully alloyed with 85 to 55% of a second metal selected from the group consisting of tungsten, molybdenum and alloys thereof, such that said fully alloyed material has said first metal and said second metal substantially fully interdiffused therein; and, an alkaline earth activator dispersed within said porous body.
Claim 3
Dependent Claim
57 words
A thermionic emitter according to claim 1 wherein said activator comprises a mixture of barium oxide or a compound of barium which decomposes on heating to the oxide, an oxide or compound which decomposes on heating to the oxide of an alkaline earth metal other than barium, and at least one of aluminium oxide and boron oxide.
Claim 4
Dependent Claim
28 words
A thermionic emitter according to claim 2, wherein the said alkaline earth metal other than barium comprises a metal selected from the group of calcium, strontium and magnesium.
Claim 5
Dependent Claim
26 words
A thermionic emitter according to claim 1, wherein a layer is interposed between said coating and said porous body, the layer composed of said first metal.
Claim 6
Dependent Claim
18 words
A thermionic emitter according to claim 4, further comprising said first metal diffused into the said porous body.
Claim 7
Dependent Claim
20 words
A thermionic emitter according to claim 1, wherein the activator further comprises 1% or less of the said first metal.
Claim 8
Dependent Claim
33 words
A thermionic emitter according to claim 1, wherein the said fully alloyed material comprises about 30% to 20% of said first metal fully alloyed with about 70% to 80% of said second metal.
Claim 9
Dependent Claim
32 words
A thermionic emitter according to claim 1, wherein said fully alloyed material comprises about 35% to 45% of said first metal fully alloyed with about 65% to 55% of said second metal.
Claim 10
Dependent Claim
19 words
A thermionic emitter according to claim 1, wherein said first metal comprises osmium and said second metal comprises tungsten.
Claim 11
Dependent Claim
90 words
A thermionic emitter comprising: a porous body formed of a fully alloyed material; said fully alloyed material consisting solely of 15 to 45% of a first metal selected from the group consisting of osmium, iridium, ruthenium, rhodium, rhenium and alloys thereof, fully alloyed with 85 to 55% of a second metal selected from the group consisting of tungsten, molybdenum and alloys thereof, such that said fully alloyed material has said first metal and said second metal substantially fully interdiffused therein; and, an alkaline earth activator dispersed within said porous body.
Claim 12
Dependent Claim
90 words
A thermionic emitter comprising: a porous body formed of a fully alloyed material; said fully alloyed material consisting solely of 15 to 45% of a first metal selected from the group consisting of osmium, iridium, ruthenium, rhodium, rhenium and alloys thereof, fully alloyed with 85 to 55% of a second metal selected from the group consisting of tungsten, molybdenum and alloys thereof, such that said fully alloyed material has said first metal and said second metal substantially fully interdiffused therein; and, an alkaline earth activator dispersed within said porous body.
Claim 13
Independent Claim
118 words
A method of making a thermionic electron emitter comprising the steps of: providing a first metal selected from the group consisting of osmium, iridium, ruthenium, rhodium, rhenium and alloys thereof and a second metal selected from the group consisting of tungsten, molybdenum and alloys thereof, providing a porous body; fully alloying said first and second metals to form at least an emissive surface layer on said porous body as a fully alloyed material consisting solely of 15 to 45% of said first metal and about 85 to 55% of said second metal, such that said fully alloyed material has said first and said second metal substantially interdiffused therein; and incorporating an alkaline earth activator in said porous body.
Claim 14
Independent Claim
118 words
A method of making a thermionic electron emitter comprising the steps of: providing a first metal selected from the group consisting of osmium, iridium, ruthenium, rhodium, rhenium and alloys thereof and a second metal selected from the group consisting of tungsten, molybdenum and alloys thereof, providing a porous body; fully alloying said first and second metals to form at least an emissive surface layer on said porous body as a fully alloyed material consisting solely of 15 to 45% of said first metal and about 85 to 55% of said second metal, such that said fully alloyed material has said first and said second metal substantially interdiffused therein; and incorporating an alkaline earth activator in said porous body.
Claim 15
Dependent Claim
55 words
A method according to claim 11, wherein the activator comprises a mixture of barium oxide a compound of barium which decomposes on heating to the oxide, an oxide or compound which decomposes on heating to the oxide of an alkaline earth metal other than barium, and at least one of aluminium oxide and boron oxide.
Claim 16
Dependent Claim
25 words
A method according to claim 12, wherein the said metal other than barium comprises a metal selected from the group of calcium, strontium and magnesium.
Claim 17
Dependent Claim
31 words
A method according to claim 11, wherein the proportions of the selected metals are about 65 to 55% of said second metal and about 35 to 45% of said first metal.
Claim 18
Dependent Claim
31 words
A method according to claim 11, wherein the proportions of the selected metals are about 70 to 80% of said second metal and about 30 to 20% of said first metal.
Claim 19
Dependent Claim
18 words
A method according to claim 11, wherein said second metal is tungsten and said first metal is osmium.
Claim 20
Independent Claim
136 words
A method of making a thermionic electron emitter comprising the steps of: (i) providing a porous matrix of a metal selected from the group consisting of tungsten, molybdenum and alloys thereof; (ii) impregnating the matrix with an alkaline earth activator; and (iii) providing a first metal selected from the group consisting of osmium, iridium, ruthenium, rhodium, rhenium, and alloys thereof and a second metal selected from the group consisting of tungsten, molybdenum and alloys thereof; (iv) fully alloying said first and second metals and forming a fully alloyed coating as an emissive surface layer on the impregnated matrix, said fully alloyed coating consisting solely of 15 to 45% of said first metal and about 85 to 55% of said first metal, and said fully alloyed coating having said first and said second metal substantially interdiffused therein.
Claim 21
Independent Claim
136 words
A method of making a thermionic electron emitter comprising the steps of: (i) providing a porous matrix of a metal selected from the group consisting of tungsten, molybdenum and alloys thereof; (ii) impregnating the matrix with an alkaline earth activator; and (iii) providing a first metal selected from the group consisting of osmium, iridium, ruthenium, rhodium, rhenium, and alloys thereof and a second metal selected from the group consisting of tungsten, molybdenum and alloys thereof; (iv) fully alloying said first and second metals and forming a fully alloyed coating as an emissive surface layer on the impregnated matrix, said fully alloyed coating consisting solely of 15 to 45% of said first metal and about 85 to 55% of said first metal, and said fully alloyed coating having said first and said second metal substantially interdiffused therein.
Claim 22
Dependent Claim
24 words
A method according to claim 17, wherein said fully alloyed coating is formed by co-sputtering said first and second metals onto said porous matrix.
Claim 23
Dependent Claim
24 words
A method according to claim 17, wherein said fully alloyed coating is formed by co-evaporating said first and second metals onto said porous matrix.
Claim 24
Dependent Claim
30 words
A method according to claim 17, wherein said fully alloyed coating is formed by co-precipitating said first and second metals onto said porous matrix from reducible compounds of those metals.
Claim 25
Dependent Claim
28 words
A method according to claim 17, further comprising the step of forming a layer of said first metal on said matrix prior to forming said fully alloyed coating.
Claim 26
Dependent Claim
38 words
A method according to claim 17, further comprising the steps of forming a layer of said first metal on said matrix and causing the metal layer to diffuse into said matrix prior to forming said fully alloyed coating.
Claim 27
Dependent Claim
29 words
A method according to claim 22 further comprising the step of forming a further layer of said first metal on said matrix prior to forming said fully alloyed coating.
Claim 28
Dependent Claim
68 words
A method according to claim 17, wherein the impregnating step comprises: (i) forming a reducible impregnation mixture of the said activator and a compound of the a metal selected from the group consisting of osmium, iridium, ruthenium, rhodium, rhenium, and alloys thereof; (ii) providing a reducing atmosphere; and, (iii) impregnating said matrix using said mixture in said reducing atmosphere whereby said selected metal is released from its compound.
Claim 29
Independent Claim
124 words
A method of making a thermionic electron emitter comprising the steps of: (i) providing a first metal selected from the group consisting of osmium, iridium, ruthenium, rhodium, rhenium, and alloys thereof and a second metal selected from the group consisting of tungsten, molybdenum and alloys thereof; (ii) pressing a mixture of 15 to 45% of said first metal with about 85 to 55% of said second metal; (iii) sintering said mixture to form a porous matrix; (iv) producing a fully alloyed material consisting solely of said first metal fully alloyed with said second metal by heating said porous matrix, said fully alloyed material having said first and said second metal substantially interdiffused therein; and (v) impregnating said porous matrix with an alkaline earth activator.
Claim 30
Independent Claim
124 words
A method of making a thermionic electron emitter comprising the steps of: (i) providing a first metal selected from the group consisting of osmium, iridium, ruthenium, rhodium, rhenium, and alloys thereof and a second metal selected from the group consisting of tungsten, molybdenum and alloys thereof; (ii) pressing a mixture of 15 to 45% of said first metal with about 85 to 55% of said second metal; (iii) sintering said mixture to form a porous matrix; (iv) producing a fully alloyed material consisting solely of said first metal fully alloyed with said second metal by heating said porous matrix, said fully alloyed material having said first and said second metal substantially interdiffused therein; and (v) impregnating said porous matrix with an alkaline earth activator.
Claim 31
Independent Claim
109 words
A method of making a thermionic emitter comprising the steps of: (i) providing a powder of fully alloyed material comprising 15 to 45% of a first metal selected from the group consisting of osmium, iridium, ruthenium, rhodium, rhenium and alloys thereof and 85 to 55% of a second metal selected from the group consisting of tungsten, molybdenum, and alloys thereof, the particles of the fully alloyed powder having said first and said second metal substantially interdiffused therein; (ii) placing said powder in a mold; (iii) pressing said powder; (iv) sintering the pressed powder to form a porous matrix; and, (v) impregnating said porous matrix with an alkaline earth activator.
Claim 32
Independent Claim
109 words
A method of making a thermionic emitter comprising the steps of: (i) providing a powder of fully alloyed material comprising 15 to 45% of a first metal selected from the group consisting of osmium, iridium, ruthenium, rhodium, rhenium and alloys thereof and 85 to 55% of a second metal selected from the group consisting of tungsten, molybdenum, and alloys thereof, the particles of the fully alloyed powder having said first and said second metal substantially interdiffused therein; (ii) placing said powder in a mold; (iii) pressing said powder; (iv) sintering the pressed powder to form a porous matrix; and, (v) impregnating said porous matrix with an alkaline earth activator.
Claim 33
Dependent Claim
32 words
A method of making a thermionic electron emitter as claimed in claim 25 wherein the heating of said porous matrix takes place at 1800° to 2000° C. for five to ten hours.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1989-02-10 | 1989-08-12 | 1990-02-11 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1993-02-10 | 1993-08-12 | 1994-02-11 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1997-02-10 | 1997-08-12 | 1998-02-11 | $7700.00 | Window Closed / Lapsed |