US2446468A - Selenium rectifiers - Google Patents

Selenium rectifiers Download PDF

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US2446468A
US2446468A US599518A US59951845A US2446468A US 2446468 A US2446468 A US 2446468A US 599518 A US599518 A US 599518A US 59951845 A US59951845 A US 59951845A US 2446468 A US2446468 A US 2446468A
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selenium
electrode
layer
counter
cadmium
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Stanley S Fry
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Fansteel Inc
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having at least one potential-jump barrier or surface barrier, e.g. PN junction, depletion layer or carrier concentration layer
    • H01L21/06—Manufacture or treatment of semiconductor devices or of parts thereof the devices having at least one potential-jump barrier or surface barrier, e.g. PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising selenium or tellurium in uncombined form other than as impurities in semiconductor bodies of other materials
    • H01L21/12—Application of an electrode to the exposed surface of the selenium or tellurium after the selenium or tellurium has been applied to the foundation plate
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/02104—Forming layers
    • H01L21/02365—Forming inorganic semiconducting materials on a substrate
    • H01L21/02518—Deposited layers
    • H01L21/02521—Materials
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/02104—Forming layers
    • H01L21/02365—Forming inorganic semiconducting materials on a substrate
    • H01L21/02612—Formation types
    • H01L21/02617—Deposition types
    • H01L21/02623—Liquid deposition
    • H01L21/02625—Liquid deposition using melted materials
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/02104—Forming layers
    • H01L21/02365—Forming inorganic semiconducting materials on a substrate
    • H01L21/02612—Formation types
    • H01L21/02617—Deposition types
    • H01L21/02631—Physical deposition at reduced pressure, e.g. MBE, sputtering, evaporation
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/02104—Forming layers
    • H01L21/02365—Forming inorganic semiconducting materials on a substrate
    • H01L21/02656—Special treatments
    • H01L21/02664—Aftertreatments
    • H01L21/02667—Crystallisation or recrystallisation of non-monocrystalline semiconductor materials, e.g. regrowth

Definitions

  • a rigid carrier electrode or supporting electrode is provided with a thin coating or layer of selenium.
  • the supporting electrode may be formed of nickel, nickel-plated iron, aluminum, magnesium, beryllium or other metals and alloys.
  • a common practice in the production of selenium rectifiers includes grit blasting the iron disc or plate and electroplating the disc with nickel, The purpose of the grit blasting is to present a roughened surface to the selenium and to thereby improve the adherence of the selenium to the carrier electrode. The disc is then thoroughly cleaned and a thin film of selenium is applied over the nickel layer.
  • the selenium film or layer may be formed by a variety of methods.
  • the plate or disc may be heated to a temperature above the melting point .of selenium, for example, to a temperature of from 230 C. to 250 C., andthe selenium in stick form may be rubbed across the heated plate in order to melt the selenium and formthe desired film.
  • Another method of application includes over the heated'plate by. mechanical means, as with a-glass rod.
  • the selenium may also be deposited on the carrier electrode from a. vapor phase. The vaporization method is commonly employed in depositing the selenium filmupon the" light metal carrier electrodes.
  • Various materials may be added to the selenium to increase its conductivity and otherwise impart --desired characteristics and properties.
  • the selenium is then transformed into its gray, crystalline state by heat treatment.
  • the coated discs are generally stacked with mica, aluminum or other inert, smooth-surfaced discs or washers in contact with the selenium and between adjacent plates, and the stack subjected to a moderate pressure.
  • the stacks under pressure are then subjected to a relatively low temperature, that is, a temperature below 150 C., and maintained at such temperature for from one hour to four or five hours.
  • a relatively low temperature that is, a temperature below 150 C., and maintained at such temperature for from one hour to four or five hours.
  • the selenium softens so that the pressure produces a layer of selenium oi relatively uniform thickness and having a smooth surface.
  • the stacks are withdrawn from the oven or heat treating furnace and the plates are removed from the stack.
  • the plates are then given a further heat treatment at a temperature approachm the melting point of selenium.
  • This heat treatment is generally conducted at temperatures between about 200 C. and the melting point of selenium, for example, about 210 C., for a period of from fifteen minutes to several hours.
  • a layer of selenium is produced having a smooth surface of more or less uniform thickness and the selenium is transformed from its amorphous, non-conducting form into its gray, crystalline, conducting form.
  • the smooth surface of the selenium film is then treated to form an artificial blocking layer and a counter-electrode consisting of a relatively low melting point alloy is applied, as by spraying, over the selenium coating.
  • the final step in the manufacture of the rectifier plates consists of an electrical forming treatment.
  • This treatment consists of subjecting the plate to either an alternating or direct current voltage below about 15 volts or a pulsating direct current starting with a low voltage of about 8 .volts and gradually increasing the voltage to about 21 volts over a period of several hours.
  • a current limiting 'resistor In the use of an alternating current, it is necessary to include in the circuit a current limiting 'resistor because one-half cyclefiows in the forward direction of the rectifier plate.
  • the voltage may be about 20 volts and the period required for forming is generally greater than that require when a direct current is employed because only one-half cycle of the current flows in the reverse direction.
  • Light sensitive devices of the blocking layer class are produced in a similar manner.
  • a supporting electrode is provided with a thin film or layer of selenium in its. gray, crystalline modification and an artificial blocking layer formed on the surface of the selenium,
  • a second electrode is then applied over the treated surface of the selenium,
  • This electrode may consist of a lightpermeable film of metal or a metal grid. The application of the light-permeable metal may be accomplished by any of the methods known to the art.
  • This invention is directed to the manufacture of selenium rectifiers provided with a specific type of counter-electrode.
  • the method is not limited to any specific form, type or composition of carrier electrode. Any method may be employed in providing the carrier electrode with the film or layer of gray, crystalline, conducting selenium.
  • the selenium layer may or may not contain added a selenium rectifier element havingan appreciably higher break down voltage-than selenium rectifiers made with the usual and conventional low melting point counter-electrode.
  • thecounter-electrode consists oi a low. melting point alloy oi bismuth
  • the alloy consists of 4 5% to 55% bismuth. 'to. 30% tin and 20 to cadmium,- a common alloy containing 54% bismuth,26% tin and 20% cadmium. This alloy has a melting point oi about'l30 C.
  • Another common alloy consists of Wood's metal, contains approximately.50% bismuth, 25% lead, 12.5%
  • tin-cadmium alloys containing 25% to60% cadmium.-' An alloy of 68% tin and 32% cadmium has a melting point of about 180 C.
  • the counter-electrode disclosed in Patentf-No. 2,193,610 consists of 75% tin and 25% cadmium ,and has a melting point of about 165 C.
  • Selenium rectiflers provided with a magnesium containing counter-electrode may be operated at applied alternating current voltages between and 35 volts without danger of breakdown.
  • An artificial blocking layer may be du -res carrier electrode is provided with a thin film or layer of selenium in its gray. crystalline modification.
  • An artificial blocking layer may be pro-' vided by any desired manner.
  • the counterelectrodeof this invention is applied as by One of the methods commonly employed in grading and in evaluating the quality of selenium rectifier plates is the measurementof the current passed by the plate in the reverse or blocking direction upon application of a direct currentvoltage to the plate in the blocking directifier plates made in accordance with the present invention and of rectifier plates made with a conventional counter-electrode, a group of nickel plated iron discs, each having an area of approximately 3 sq.
  • cm. was provided with a layer-oi selenium in its gray, crystalline form.
  • the discs were heated to a temperature 01' about 240 C. and selenium in stick form rubbed across the plate. The selenium was spread over the surface of the heated discs with a glass rod.
  • the plates were then stacked with mica discs covering the selenium layer and the stack placed under pressure. The stack was heated to a temperature below C. for about 2 hours. pressure was then removed and the plates heated to about 210? C. and maintained at this temperature for about hour.
  • the group of plates was then divided into two series.
  • the first series of plates was provided with a counter-electrode consisting of approximately 54% bismuth. 26% tin and 20% cadmium.
  • the second series oi plates was provided with a counter-electrode consisting of the same alloy to which had been added about 2% magnesium.
  • the discs of the series of plates provided with the counter-electrode of the invention were subjected to an electrical forming treatment by the application of a rectified alternating current voltage to each plate in the reverse or blocking direction, the rectified voltage reaching a maximum of about 34 volts.
  • the discs or plates provided with the conventional counter-electrode were subjected to an electrical forming treatment by the application of a rectified aiternating current voltage to each plate in the reverse or blocking direction, the rectified voltage reaching a maximum of about 21 volts. It is not possible to apply a voltage much greater than 21 volts to these plates because the counterelectrodes melt and destroy the rectifier upon the application of voltages between about 23 volts and 25 volts.
  • a direct current voltage of 34 volts from a storage battery source was applied in the reverse or blocking direction to the individual discs of each series.
  • the leakage current or the reverse current flowing in the standard plates averaged approximately 25 milliamperesl
  • the leakage current in the plates provided with the counterelectrode of this invention averaged approximately 2 milliamperes.
  • the standard or control plates it was necessary to measure or read the current flow as rapidly as possible because at this applied voltage the counter-electrode melts in a short period which may be less than one minute.
  • the continuous application of this voltage does not damage or injure the rectifier and such plates may be operated at applied alternating current voltages up to 34 or 35 volts.
  • a blocking layer device comprising a carrier electrode, a layer of gray, crystalline selenium and a counter-electrode consisting essentially of hismuth, tin, lead, cadmium and a small amount of magnesium, the counter-electrode having a melting point not exceeding 180 C.
  • a blocking layer device comprising a carrier electrode, a layer of gray, crystalline selenium and a counter-electrode consisting essentially 01' bismuth, tin, lead, cadmium and from about 0.25% to about 2% magnesium, the counter-electrode having a melting point not exceeding 180 C.
  • a selenium rectifier comprising a, carrier electrode, a layer of gray, crystalline selenium and a counter-electrode consisting essentially of bismuth, tin, lead, cadmium and a small amount of magnesium. the counter-electrode having a melting point not exceeding 180 C.
  • a selenium rectifier comprising a carrier electrode, a layer of gray, crystalline selenium and a counter-electrode consisting essentially 01 bismuth, tin, lead. cadmium and irom about 0.25% to about 2% magnesium, the counter-electrode having a melting point not exceeding 180 C.
  • a selenium rectifier comprising a carrier electrode, a layer 01' gray. crystalline selenium and a counter-electrode consisting essentially oi bismuth, tin, cadmium and a small amount of magnesium.
  • a selenium rectifier comprising a carrier electrode, a layer or gray.
  • crystalline selenium and a counter-electrode consisting essentially of bismuth, tin, cadmium and from about 0.25% to about 2% magnesium.
  • a selenium rectifier comprising a carrier electrode, a layer oi gray, crystalline selenium and a counter-electrode composed of an alloy consistcadmium and magnesium in amounts up to about 8.
  • a selenium rectifier comprising a carrierelectrode, a layer of gray, crystalline selenium and a counter-electrode composed of an alloy consisting essentially of bismuth, cadmium and magnesium in amounts up to about 2%.
  • a selenium rectifier comprising a carrier electrode, a layer-ot gray, crystalline selenium on the carrier electrode, a thin layer of an alloy of bismuth. tin, cadmium and magnesium on the selenium layer and a layer or an alloy of bismuth,
  • a selenium rectifier comprising a carrier electrode, a layer of gray, crystalline selenium. a thin layer of'an alloy consisting essentially 01 bis. muth and cadmium and containing magnesium on the selenium layer and an exterior layer of an alloy consisting essentially of bismuth and.
  • a selenium rectifier comprising a carrier electrode, a layer or gray, crystalline selenium and a counter-electrode, the counter-electrode comprising a thin layer of an alloy on the selenium layer, the alloy consisting essentially oi bismuth. tin, lead. cadmium and a small amount of magnesium and having a melting point not exceeding 0., and an exterior layer of an alloy over the magnesium containing layer, the last named alloy consisting essentially of bismuth. tin, lead and cadmium and having a melting point not exceeding 180 C.
  • a selenium rectifier comprising a carrier electrode, a layer of gray, crystalline selenium and a counter-electrode composed of an alloy consisting essentially of cadmium, tin and magnesium in amounts up to about 2%.
  • a selenium rectifier comprising a carrier electrode, a layer of gray, crystalline selenium, a thin layer or an alloy consisting essentially of cadmium and tin and containing magnesium on the selenium layer and an exterior layer of an alloy consisting essentially oi. cadmium and tin.

Description

Patented Aug. 3, 1948 SELENIUM RECTIFIERS Stanley S. Fry, North Chicago, Ill., assignor to Fansteel Metallurgical Corporation, North Chicago, Ill.. a corporation of New York No Drawing. Application June 14, 1945,
Serial No. 599,511!
13 Claims. (Cl. 175-366) This invention relates to selenium rectifiers.
.In the production of selenium rectiflers, a rigid carrier electrode or supporting electrode is provided with a thin coating or layer of selenium. The supporting electrode may be formed of nickel, nickel-plated iron, aluminum, magnesium, beryllium or other metals and alloys. A common practice in the production of selenium rectifiers includes grit blasting the iron disc or plate and electroplating the disc with nickel, The purpose of the grit blasting is to present a roughened surface to the selenium and to thereby improve the adherence of the selenium to the carrier electrode. The disc is then thoroughly cleaned and a thin film of selenium is applied over the nickel layer.
The selenium film or layer may be formed by a variety of methods. The plate or disc may be heated to a temperature above the melting point .of selenium, for example, to a temperature of from 230 C. to 250 C., andthe selenium in stick form may be rubbed across the heated plate in order to melt the selenium and formthe desired film. Another method of application includes over the heated'plate by. mechanical means, as with a-glass rod. The selenium may also be deposited on the carrier electrode from a. vapor phase. The vaporization method is commonly employed in depositing the selenium filmupon the" light metal carrier electrodes. Various materials may be added to the selenium to increase its conductivity and otherwise impart --desired characteristics and properties.
The selenium is then transformed into its gray, crystalline state by heat treatment. The coated discs are generally stacked with mica, aluminum or other inert, smooth-surfaced discs or washers in contact with the selenium and between adjacent plates, and the stack subjected to a moderate pressure. The stacks under pressure are then subjected to a relatively low temperature, that is, a temperature below 150 C., and maintained at such temperature for from one hour to four or five hours. During this stage of the heat treatment the selenium softens so that the pressure produces a layer of selenium oi relatively uniform thickness and having a smooth surface.
The stacks are withdrawn from the oven or heat treating furnace and the plates are removed from the stack. The plates are then given a further heat treatment at a temperature approachm the melting point of selenium. This heat treatment is generally conducted at temperatures between about 200 C. and the melting point of selenium, for example, about 210 C., for a period of from fifteen minutes to several hours. During the combined heat treatment, a layer of selenium is produced having a smooth surface of more or less uniform thickness and the selenium is transformed from its amorphous, non-conducting form into its gray, crystalline, conducting form.
The smooth surface of the selenium film is then treated to form an artificial blocking layer and a counter-electrode consisting of a relatively low melting point alloy is applied, as by spraying, over the selenium coating.
The final step in the manufacture of the rectifier plates consists of an electrical forming treatment. This treatment consists of subjecting the plate to either an alternating or direct current voltage below about 15 volts or a pulsating direct current starting with a low voltage of about 8 .volts and gradually increasing the voltage to about 21 volts over a period of several hours.
In the use of an alternating current, it is necessary to include in the circuit a current limiting 'resistor because one-half cyclefiows in the forward direction of the rectifier plate. The voltage may be about 20 volts and the period required for forming is generally greater than that require when a direct current is employed because only one-half cycle of the current flows in the reverse direction.
Light sensitive devices of the blocking layer class are produced in a similar manner. A supporting electrode is provided with a thin film or layer of selenium in its. gray, crystalline modification and an artificial blocking layer formed on the surface of the selenium, A second electrode is then applied over the treated surface of the selenium, This electrode may consist of a lightpermeable film of metal or a metal grid. The application of the light-permeable metal may be accomplished by any of the methods known to the art.
This invention is directed to the manufacture of selenium rectifiers provided with a specific type of counter-electrode. The method is not limited to any specific form, type or composition of carrier electrode. Any method may be employed in providing the carrier electrode with the film or layer of gray, crystalline, conducting selenium. The selenium layer may or may not contain added a selenium rectifier element havingan appreciably higher break down voltage-than selenium rectifiers made with the usual and conventional low melting point counter-electrode.
Other objects and-advantages of In conventional-methods of production of selenium rectifier elements, thecounter-electrode consists oi a low. melting point alloy oi bismuth,
cadmium and tin. The particular composition or the alloy differs with various manufacturers depending in mostinstances upon individual preference. Commonly. thealloy consists of 4 5% to 55% bismuth. 'to. 30% tin and 20 to cadmium,- a common alloy containing 54% bismuth,26% tin and 20% cadmium. This alloy has a melting point oi about'l30 C. Another common alloy consists of Wood's metal, contains approximately.50% bismuth, 25% lead, 12.5%
' cadmium and 12.5% tin and has a melting point of about 65.5 C. Various tin-cadmium alloys and bismuth-cadmium alloys have been proposed. For example, in Patent No. 2,235,051
there is disclosed tin-cadmium alloys containing 25% to60% cadmium.-' An alloy of 68% tin and 32% cadmium has a melting point of about 180 C. The counter-electrode disclosed in Patentf-No. 2,193,610 consists of 75% tin and 25% cadmium ,and has a melting point of about 165 C.
' Selenium rectifiers provided with counterelectrodes of these alloys are generally operated at an applied alternating current voltage of about lito 18 volts since the rectifier elements break down at voltages in excess of about 18 volts when applied continuously. In some instances this voltage limitation has been a disadvantage in the use of selenium rectifiers.
I have discovered that the addition of small amounts of magnesium to the counter-electrode alloy greatly increases the voltage which may be safely and continuously applied to the selenium rectifier. The amount of magnesium does not appear to be particularly critical so far as exceedingly thin sprayed coating containing magnesium and coating or covering this thin film with the usual counter-electrode containing no magnesium so as to provide a better mechanical layer or film.
Selenium rectiflers provided with a magnesium containing counter-electrode may be operated at applied alternating current voltages between and 35 volts without danger of breakdown.
- The production of the selenium rectifiers may be identical to that commonly used wherein a this invention will become apparent irom the following description andclaims.
' materials-to impart desired characteristicsi and properties. An artificial blocking layer may be du -res carrier electrode is provided with a thin film or layer of selenium in its gray. crystalline modification. An artificial blocking layer may be pro-' vided by any desired manner. The counterelectrodeof this invention is applied as by One of the methods commonly employed in grading and in evaluating the quality of selenium rectifier plates is the measurementof the current passed by the plate in the reverse or blocking direction upon application of a direct currentvoltage to the plate in the blocking directifier plates made in accordance with the present invention and of rectifier plates made with a conventional counter-electrode, a group of nickel plated iron discs, each having an area of approximately 3 sq. cm., was provided with a layer-oi selenium in its gray, crystalline form. The discs were heated to a temperature 01' about 240 C. and selenium in stick form rubbed across the plate. The selenium was spread over the surface of the heated discs with a glass rod. The plates were then stacked with mica discs covering the selenium layer and the stack placed under pressure. The stack was heated to a temperature below C. for about 2 hours. pressure was then removed and the plates heated to about 210? C. and maintained at this temperature for about hour.
The group of plates was then divided into two series. The first series of plates was provided with a counter-electrode consisting of approximately 54% bismuth. 26% tin and 20% cadmium. The second series oi plates was provided with a counter-electrode consisting of the same alloy to which had been added about 2% magnesium. The discs of the series of plates provided with the counter-electrode of the invention were subjected to an electrical forming treatment by the application of a rectified alternating current voltage to each plate in the reverse or blocking direction, the rectified voltage reaching a maximum of about 34 volts. The discs or plates provided with the conventional counter-electrode were subjected to an electrical forming treatment by the application of a rectified aiternating current voltage to each plate in the reverse or blocking direction, the rectified voltage reaching a maximum of about 21 volts. It is not possible to apply a voltage much greater than 21 volts to these plates because the counterelectrodes melt and destroy the rectifier upon the application of voltages between about 23 volts and 25 volts.
A direct current voltage of 34 volts from a storage battery source was applied in the reverse or blocking direction to the individual discs of each series. The leakage current or the reverse current flowing in the standard plates averaged approximately 25 milliamperesl The leakage current in the plates provided with the counterelectrode of this invention averaged approximately 2 milliamperes. In the case of the standard or control plates it was necessary to measure or read the current flow as rapidly as possible because at this applied voltage the counter-electrode melts in a short period which may be less than one minute. In the case of the plates having a counter-electrode of this in- The vention, the continuous application of this voltage does not damage or injure the rectifier and such plates may be operated at applied alternating current voltages up to 34 or 35 volts.
The improvements in the operating characteristics of rectifier plates made in accordance with this invention are quite apparent from this data. It is obvic us that the numerical values of the leakage current will differ with different size rectifier plates and also with selenium having various addition agents. The data, however, is representative oi the improvements attained in the practice oi my invention. The improvements obtained by the addition of small amounts of magnesium are not limited to the specific bismuthtin-cadmium alloys set 'iorth in the specific example but are also obtained when magnesium is added to other bismuth-tin-cadmium alloys and other low melting point alloys or the type commonly used in providing selenium rectifier elements with counter-electrodes.
I claim:
1. A blocking layer device comprising a carrier electrode, a layer of gray, crystalline selenium and a counter-electrode consisting essentially of hismuth, tin, lead, cadmium and a small amount of magnesium, the counter-electrode having a melting point not exceeding 180 C.
2. A blocking layer device comprising a carrier electrode, a layer of gray, crystalline selenium and a counter-electrode consisting essentially 01' bismuth, tin, lead, cadmium and from about 0.25% to about 2% magnesium, the counter-electrode having a melting point not exceeding 180 C.
3. A selenium rectifier comprising a, carrier electrode, a layer of gray, crystalline selenium and a counter-electrode consisting essentially of bismuth, tin, lead, cadmium and a small amount of magnesium. the counter-electrode having a melting point not exceeding 180 C.
4. A selenium rectifier comprising a carrier electrode, a layer of gray, crystalline selenium and a counter-electrode consisting essentially 01 bismuth, tin, lead. cadmium and irom about 0.25% to about 2% magnesium, the counter-electrode having a melting point not exceeding 180 C.
5. A selenium rectifier comprising a carrier electrode, a layer 01' gray. crystalline selenium and a counter-electrode consisting essentially oi bismuth, tin, cadmium and a small amount of magnesium.
6. A selenium rectifier comprising a carrier electrode, a layer or gray. crystalline selenium and a counter-electrode consisting essentially of bismuth, tin, cadmium and from about 0.25% to about 2% magnesium.
7. A selenium rectifier comprising a carrier electrode, a layer oi gray, crystalline selenium and a counter-electrode composed of an alloy consistcadmium and magnesium in amounts up to about 8. A selenium rectifier comprising a carrierelectrode, a layer of gray, crystalline selenium and a counter-electrode composed of an alloy consisting essentially of bismuth, cadmium and magnesium in amounts up to about 2%. a
9. A selenium rectifier comprising a carrier electrode, a layer-ot gray, crystalline selenium on the carrier electrode, a thin layer of an alloy of bismuth. tin, cadmium and magnesium on the selenium layer and a layer or an alloy of bismuth,
tin and cadmium on the first named alloy layer.
10. A selenium rectifier comprising a carrier electrode, a layer of gray, crystalline selenium. a thin layer of'an alloy consisting essentially 01 bis. muth and cadmium and containing magnesium on the selenium layer and an exterior layer of an alloy consisting essentially of bismuth and.
cadmium.
11. A selenium rectifier comprising a carrier electrode, a layer or gray, crystalline selenium and a counter-electrode, the counter-electrode comprising a thin layer of an alloy on the selenium layer, the alloy consisting essentially oi bismuth. tin, lead. cadmium and a small amount of magnesium and having a melting point not exceeding 0., and an exterior layer of an alloy over the magnesium containing layer, the last named alloy consisting essentially of bismuth. tin, lead and cadmium and having a melting point not exceeding 180 C.
12. A selenium rectifier comprising a carrier electrode, a layer of gray, crystalline selenium and a counter-electrode composed of an alloy consisting essentially of cadmium, tin and magnesium in amounts up to about 2%.
13. A selenium rectifier comprising a carrier electrode, a layer of gray, crystalline selenium, a thin layer or an alloy consisting essentially of cadmium and tin and containing magnesium on the selenium layer and an exterior layer of an alloy consisting essentially oi. cadmium and tin.
STANLEY S. FRY.
nnrnnnncss CITED The following references. are of record in the file 01' this patent:
UNITED STATES PATENT S Lorenz Nov. 12, 1940
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Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1826955A (en) * 1927-03-30 1931-10-13 Ruben Rectifier Corp Electric current rectifier
US1866351A (en) * 1927-01-29 1932-07-05 Gen Electric Rectification of alternating currents
US2039083A (en) * 1934-03-29 1936-04-28 Gen Electric Light measuring instrument
US2162487A (en) * 1936-09-28 1939-06-13 Westinghouse Electric & Mfg Co Selenium rectifier
US2175016A (en) * 1936-06-20 1939-10-03 Gen Electric Method of producing selenium rectifiers or the like
US2221596A (en) * 1938-01-22 1940-11-12 Fides Gmbh Method of manufacturing dry rectifiers

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1866351A (en) * 1927-01-29 1932-07-05 Gen Electric Rectification of alternating currents
US1826955A (en) * 1927-03-30 1931-10-13 Ruben Rectifier Corp Electric current rectifier
US2039083A (en) * 1934-03-29 1936-04-28 Gen Electric Light measuring instrument
US2175016A (en) * 1936-06-20 1939-10-03 Gen Electric Method of producing selenium rectifiers or the like
US2162487A (en) * 1936-09-28 1939-06-13 Westinghouse Electric & Mfg Co Selenium rectifier
US2221596A (en) * 1938-01-22 1940-11-12 Fides Gmbh Method of manufacturing dry rectifiers

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