US2729880A - Aluminum oxide semi-conductors - Google Patents
Aluminum oxide semi-conductors Download PDFInfo
- Publication number
- US2729880A US2729880A US50883A US5088348A US2729880A US 2729880 A US2729880 A US 2729880A US 50883 A US50883 A US 50883A US 5088348 A US5088348 A US 5088348A US 2729880 A US2729880 A US 2729880A
- Authority
- US
- United States
- Prior art keywords
- aluminum
- oxide
- aluminum oxide
- semi
- resistance
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 title claims description 18
- 239000004065 semiconductor Substances 0.000 title claims description 10
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 23
- 229910052782 aluminium Inorganic materials 0.000 claims description 21
- 238000002844 melting Methods 0.000 claims description 4
- 230000008018 melting Effects 0.000 claims description 4
- 238000005245 sintering Methods 0.000 claims description 4
- 229940024548 aluminum oxide Drugs 0.000 description 15
- 239000000463 material Substances 0.000 description 10
- 229910052751 metal Inorganic materials 0.000 description 6
- 239000002184 metal Substances 0.000 description 6
- 239000000919 ceramic Substances 0.000 description 4
- 238000010304 firing Methods 0.000 description 4
- 239000000203 mixture Substances 0.000 description 4
- 238000000034 method Methods 0.000 description 3
- 230000001590 oxidative effect Effects 0.000 description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 239000004020 conductor Substances 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 239000012212 insulator Substances 0.000 description 2
- 239000011148 porous material Substances 0.000 description 2
- 229910052786 argon Inorganic materials 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 229910010293 ceramic material Inorganic materials 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 230000005611 electricity Effects 0.000 description 1
- 239000001307 helium Substances 0.000 description 1
- 229910052734 helium Inorganic materials 0.000 description 1
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 description 1
- 239000011261 inert gas Substances 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 239000008188 pellet Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01C—RESISTORS
- H01C7/00—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material
- H01C7/04—Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered semi-conducting material with or without insulating material having negative temperature coefficient
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B1/00—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
- H01B1/06—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors mainly consisting of other non-metallic substances
- H01B1/08—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors mainly consisting of other non-metallic substances oxides
Definitions
- This invention relates to improvements in that class of materials known generally as semi-conductors and having a negative temperature coefiicient of resistance.
- the resistance of this class of materials is relatively high but not nearly as high as that of materials classed as good insulators.
- the present invention relates more particularly to materials of this nature.
- One object of the present invention is to provide improved materials having relatively high resistance and a relatively low temperature coeflicient of resistance.
- Another object of the invention is to provide a novel.
- product comprising aluminum oxide and aluminum, which product has a negative temperature coefiicient of resistance.
- Another object of the invention is to provide improved semi-conducting materials which can be operated at high temperatures.
- the products of the present inventi n are made by combining certain proportions of aluminum and aluminum oxide at sintering temperatures in the presence of a non-oxidizing atmosphere.
- a nonoxidizing atmosphere is meant a vacuum, a reducing at mosphere or an inert atmosphere. It is preferable to exclude water vapor from the atmosphere.
- Aluminum itself is, of course, a good conductor of electricity while aluminumoxide is normally a good insulator. If so much aluminum is added to the aluminum oxide that a continuous conducting path around the insulating particles is provided by the aluminum, the mixture would then become a fairly good conductor.
- this type of composition does not come within the scope of the present invention. It has been found that aluminum will disperse freely throughout a body of aluminum oxide. It is not possible to mix any randomly selected metal with a randomly selected ceramic material and have the metal disperse freely throughout the ceramic. Also, in those compositions in which there is free dispersal, the resulting product is not always a semi-conductor having a negative temperature coefficient of resistance. It, therefore, appears to be an individual problem as to whether any particular metal and a particular ceramic will produce the desired type of product.
- Example I One part of aluminum was mixed with three parts aluminum oxide and the mixture molded into a cylinder one-sixteenth inch in diameter and one-fourth inch long.
- the cylinder was fired in vacuo at about l,500 C. for
- Example II A cylinder similar to that above described was made up containing one part aluminum to twenty-five parts aluminum oxide and fired at the same temperature and for the same time as the material in Example I. When tested under similar conditions, the product had a resistance or about seventy-five ohms.
- the complete range of proportions of aluminum oxide to aluminum has been found to be from 3 to l toabout 40 to 1 by weight.
- the firing temperatures may range from about 1,450" C. to temperatures just below the melting point of aluminum oxide (2,050 C.).
- the time of firing varies inversely with firing temperature. Times of twenty minutes up to one and one-ha1f hours have proved satisfactory depending upon the temperature of firing. There does not appear to be any critical upper limit of time after the product has once become stabilized. Further heating neither causes deterioration of the product nor improvement. If vacuum heating is used, the vacuum must be good enough so that all appreciable amounts of oxygen are excluded.
- the inert atmosphere may be any of the usual inert gases such as helium, nitrogen or argon.
- the product may be prepared by first forming a compressed body of aluminum oxide and then maintaining the com.- pressed body in an atmosphere of aluminum vapor until sufficient diffusion has taken place of the metal throughout the ceramic.
- Another way to combine the two substances is to immerse a compressed pellet of the ceramic in a bath of molten aluminum.
- a semi-conductor having a negative temperature 00- efiicient of resistance consisting essentially of a compact porous body of sintered aluminum oxide and aluminum, said body being made by diffusing aluminurm metal homogeneously throughout the pores of a compact body of aluminum oxide at sintering temperatures of said oxide above about l,450 C. but below the melting temperature of said oxide and in a non-oxidizing atmosphere, and the ratio by weight of said oxide to said aluminum being within the range of about 40 to 1 and about 3 to l.
- a method of making a semi-conducting material comprising diffusing aluminum metal homogeneously throughout the pores of a compressed body of aluminum oxide, that is, above about 1450 C. at sintering temperatures of said oxide but below the melting point of said oxide and in a non-oxidizing atmosphere, the ratio by weght of said oxide to said aluminum being within the range of about 40 to 1 and about 3 to l.
Landscapes
- Engineering & Computer Science (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Physics & Mathematics (AREA)
- Electromagnetism (AREA)
- Compositions Of Oxide Ceramics (AREA)
- Conductive Materials (AREA)
Description
United States Patent ALUMINUM OXIDE SEMI-CONDUCTORS William A. Miller, Port Jefferson, N. Y., assignor to Radio Corporation of America, a corporation of Delaware No Drawing. Application September 23, 1948,
Serial No. 50,883 Y 7 Claims. (Cl. 29-182-1) This invention relates to improvements in that class of materials known generally as semi-conductors and having a negative temperature coefiicient of resistance. The resistance of this class of materials is relatively high but not nearly as high as that of materials classed as good insulators.
In certain applications of semi-conducting materials, it is desirable to employ a form having a low temperature coefficient of resistance. The present invention relates more particularly to materials of this nature.
One object of the present invention is to provide improved materials having relatively high resistance and a relatively low temperature coeflicient of resistance.
Another object of the invention is to provide a novel.
product comprising aluminum oxide and aluminum, which product has a negative temperature coefiicient of resistance.
Another object of the invention is to provide improved semi-conducting materials which can be operated at high temperatures.
These and other objects will be more apparent and the invention will be better understood from the following specification.
In general, the products of the present inventi n are made by combining certain proportions of aluminum and aluminum oxide at sintering temperatures in the presence of a non-oxidizing atmosphere. By a nonoxidizing atmosphere is meant a vacuum, a reducing at mosphere or an inert atmosphere. It is preferable to exclude water vapor from the atmosphere.
Aluminum, itself is, of course, a good conductor of electricity while aluminumoxide is normally a good insulator. If so much aluminum is added to the aluminum oxide that a continuous conducting path around the insulating particles is provided by the aluminum, the mixture would then become a fairly good conductor. However, this type of composition does not come within the scope of the present invention. It has been found that aluminum will disperse freely throughout a body of aluminum oxide. It is not possible to mix any randomly selected metal with a randomly selected ceramic material and have the metal disperse freely throughout the ceramic. Also, in those compositions in which there is free dispersal, the resulting product is not always a semi-conductor having a negative temperature coefficient of resistance. It, therefore, appears to be an individual problem as to whether any particular metal and a particular ceramic will produce the desired type of product.
Example I One part of aluminum was mixed with three parts aluminum oxide and the mixture molded into a cylinder one-sixteenth inch in diameter and one-fourth inch long.
The cylinder was fired in vacuo at about l,500 C. for
,. lce
Example II A cylinder similar to that above described was made up containing one part aluminum to twenty-five parts aluminum oxide and fired at the same temperature and for the same time as the material in Example I. When tested under similar conditions, the product had a resistance or about seventy-five ohms.
The complete range of proportions of aluminum oxide to aluminum has been found to be from 3 to l toabout 40 to 1 by weight.
The firing temperatures may range from about 1,450" C. to temperatures just below the melting point of aluminum oxide (2,050 C.). The time of firing varies inversely with firing temperature. Times of twenty minutes up to one and one-ha1f hours have proved satisfactory depending upon the temperature of firing. There does not appear to be any critical upper limit of time after the product has once become stabilized. Further heating neither causes deterioration of the product nor improvement. If vacuum heating is used, the vacuum must be good enough so that all appreciable amounts of oxygen are excluded. The inert atmosphere may be any of the usual inert gases such as helium, nitrogen or argon.
Since aluminum vaporizes readily in a vacuum, the product may be prepared by first forming a compressed body of aluminum oxide and then maintaining the com.- pressed body in an atmosphere of aluminum vapor until sufficient diffusion has taken place of the metal throughout the ceramic.
Another way to combine the two substances is to immerse a compressed pellet of the ceramic in a bath of molten aluminum.
The principal advantages of the improved materials of the present invention are:
First, that they are highly refractory and, therefore, eminently suited to those uses where large amounts of power must be dissipated at high temperatures, and
Second, that they are useful where it is desired to use a material having a very low negative temperature coefiicient of resistance.
There has thus been described a new and useful type of semi-conducting material comprising aluminum and aluminum oxide ceramically combined. It is desired that the invention be limited only as defined in the appended claims.
I claim as my invention:
1. A semi-conductor having a negative temperature 00- efiicient of resistance, consisting essentially of a compact porous body of sintered aluminum oxide and aluminum, said body being made by diffusing aluminurm metal homogeneously throughout the pores of a compact body of aluminum oxide at sintering temperatures of said oxide above about l,450 C. but below the melting temperature of said oxide and in a non-oxidizing atmosphere, and the ratio by weight of said oxide to said aluminum being within the range of about 40 to 1 and about 3 to l.
2. A material according to claim 1 in which said ratio is 25 to l. v
3. A material according to claim 1 in which said ratio is 3 to 1.
4. A method of making a semi-conducting material comprising diffusing aluminum metal homogeneously throughout the pores of a compressed body of aluminum oxide, that is, above about 1450 C. at sintering temperatures of said oxide but below the melting point of said oxide and in a non-oxidizing atmosphere, the ratio by weght of said oxide to said aluminum being within the range of about 40 to 1 and about 3 to l.
5. A method according to claim 4 in which the oxide and the aluminum are mixed together before the oxide is sintered.
6. A method according to claim 4 in which the oxide is first formed into a compressed body, simered and their immersed in molten aluminum.
7. A method according to claim 4 in which the oxide is first formed into a compressed body, sintered and then exposedto an atmosphere of aluminum va or.
References Cited in the file of this patent UNITED STATES PATENTS 4 Bethel Oct. 17, 1933 'MAfifiiif 061. 28, 1941 Goldschmidt et a1 May 19, 1942 Preis Apr. 27, 1943 Colbert et a1. Dec. 16, 1947 Alexander 2.22;; July 6, 1948 McKinley Mar. 1, 1949 Hend'ren s s== s Mar. 29, 1949 FOREIGN PATENTS Great Britain 11113: 8, 1920 OTHER REFERENCES Metal industry, May 14, 1948, pa es 405-407.
Claims (1)
1. A SEMI-CONDUCTOR HAVING A NEGATIVE TEMPERATURE COEFFICIENT OF RESISTANCE, CONSISTING ESSENTIALLY OF A COMPACT POROUS BODY OF SINTERED ALUMINUM OXIDE AND ALUMINUM, SAID BODY BEING MADE BY DIFFUSING ALUMINUM METAL HOMOGENEOUSLY THROUGHOUT THE PORES OF A COMPACT BODY OF ALUMINUM OXIDE AT SINTERING TEMPERATURES OF SAID OXIDE ABOVE ABOUT 1,450* C. BUT BELOW THE MELTING TEMPERATURE OF SAID OXIDE AND IN A NON-OXIDIZING ATMOSPHERE, AND THE RATIO BY WEIGHT OF SAID OXIDE TO SAID ALUMINUM BEING WITHIN THE RANGE OF ABOUT 40 TO 1 AND ABOUT 3 TO 1.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US50883A US2729880A (en) | 1948-09-23 | 1948-09-23 | Aluminum oxide semi-conductors |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US50883A US2729880A (en) | 1948-09-23 | 1948-09-23 | Aluminum oxide semi-conductors |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| US2729880A true US2729880A (en) | 1956-01-10 |
Family
ID=21968069
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| US50883A Expired - Lifetime US2729880A (en) | 1948-09-23 | 1948-09-23 | Aluminum oxide semi-conductors |
Country Status (1)
| Country | Link |
|---|---|
| US (1) | US2729880A (en) |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2958936A (en) * | 1946-09-06 | 1960-11-08 | Meyer-Hartwig Eberhard | Electrical semi-conductors and method of manufacture |
| US3025441A (en) * | 1958-09-19 | 1962-03-13 | Gen Electric | Electrical capacitor |
| US3378498A (en) * | 1965-01-25 | 1968-04-16 | Metal Diffusions Ltd | Process for diffusing metal into a refractory or ceramic oxide using a nitrate promoter |
| US3718441A (en) * | 1970-11-18 | 1973-02-27 | Us Army | Method for forming metal-filled ceramics of near theoretical density |
| US4673435A (en) * | 1985-05-21 | 1987-06-16 | Toshiba Ceramics Co., Ltd. | Alumina composite body and method for its manufacture |
Citations (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB147685A (en) * | 1919-01-09 | 1921-12-08 | Optische Anstalt Goerz Ag | Improved manufacture of grinding tools |
| US1738141A (en) * | 1928-08-11 | 1929-12-03 | Charles F Noftzger | Electrical resistance unit and method of manufacturing same |
| US1790918A (en) * | 1931-02-03 | Max hatjser | ||
| US1856303A (en) * | 1929-02-05 | 1932-05-03 | Lava Crucible Company | Method and material employed in the manufacture of refractory articles |
| US1922221A (en) * | 1929-07-20 | 1933-08-15 | Westinghouse Electric & Mfg Co | Resistance material |
| US1931370A (en) * | 1927-11-29 | 1933-10-17 | Norton Co | Grinding, polishing, lapping, and finishing of metals |
| US2260392A (en) * | 1940-05-06 | 1941-10-28 | Wean Engineering Co Inc | Method for coating sheets |
| US2283250A (en) * | 1936-05-18 | 1942-05-19 | Goldschmidt Victor Moritz | Manufacture of refractory materials |
| US2317403A (en) * | 1941-03-07 | 1943-04-27 | American Can Co | Method of manufacturing tin plate |
| US2432657A (en) * | 1944-05-27 | 1947-12-16 | Libbey Owens Ford Glass Co | Process of evaporating metals |
| US2444763A (en) * | 1946-10-07 | 1948-07-06 | Alexander Paul | Process and apparatus for depositing metals on a support by thermal evaporation in avacuum |
| US2463404A (en) * | 1945-03-02 | 1949-03-01 | Du Pont | Process for the production of boron articles |
| US2465375A (en) * | 1947-10-20 | 1949-03-29 | Mc Feely Brick Company | Refractory and method of producing the same |
-
1948
- 1948-09-23 US US50883A patent/US2729880A/en not_active Expired - Lifetime
Patent Citations (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US1790918A (en) * | 1931-02-03 | Max hatjser | ||
| GB147685A (en) * | 1919-01-09 | 1921-12-08 | Optische Anstalt Goerz Ag | Improved manufacture of grinding tools |
| US1931370A (en) * | 1927-11-29 | 1933-10-17 | Norton Co | Grinding, polishing, lapping, and finishing of metals |
| US1738141A (en) * | 1928-08-11 | 1929-12-03 | Charles F Noftzger | Electrical resistance unit and method of manufacturing same |
| US1856303A (en) * | 1929-02-05 | 1932-05-03 | Lava Crucible Company | Method and material employed in the manufacture of refractory articles |
| US1922221A (en) * | 1929-07-20 | 1933-08-15 | Westinghouse Electric & Mfg Co | Resistance material |
| US2283250A (en) * | 1936-05-18 | 1942-05-19 | Goldschmidt Victor Moritz | Manufacture of refractory materials |
| US2260392A (en) * | 1940-05-06 | 1941-10-28 | Wean Engineering Co Inc | Method for coating sheets |
| US2317403A (en) * | 1941-03-07 | 1943-04-27 | American Can Co | Method of manufacturing tin plate |
| US2432657A (en) * | 1944-05-27 | 1947-12-16 | Libbey Owens Ford Glass Co | Process of evaporating metals |
| US2463404A (en) * | 1945-03-02 | 1949-03-01 | Du Pont | Process for the production of boron articles |
| US2444763A (en) * | 1946-10-07 | 1948-07-06 | Alexander Paul | Process and apparatus for depositing metals on a support by thermal evaporation in avacuum |
| US2465375A (en) * | 1947-10-20 | 1949-03-29 | Mc Feely Brick Company | Refractory and method of producing the same |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2958936A (en) * | 1946-09-06 | 1960-11-08 | Meyer-Hartwig Eberhard | Electrical semi-conductors and method of manufacture |
| US3025441A (en) * | 1958-09-19 | 1962-03-13 | Gen Electric | Electrical capacitor |
| US3378498A (en) * | 1965-01-25 | 1968-04-16 | Metal Diffusions Ltd | Process for diffusing metal into a refractory or ceramic oxide using a nitrate promoter |
| US3718441A (en) * | 1970-11-18 | 1973-02-27 | Us Army | Method for forming metal-filled ceramics of near theoretical density |
| US4673435A (en) * | 1985-05-21 | 1987-06-16 | Toshiba Ceramics Co., Ltd. | Alumina composite body and method for its manufacture |
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