Classifications

• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
  • C04B35/01—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
  • C04B35/46—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on titanium oxides or titanates
  • C04B35/462—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on titanium oxides or titanates based on titanates
  • C04B35/465—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on titanium oxides or titanates based on titanates based on alkaline earth metal titanates
• • 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
• • 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
  • H01C7/02—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 positive temperature coefficient
  • H01C7/022—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 positive temperature coefficient mainly consisting of non-metallic substances
  • H01C7/023—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 positive temperature coefficient mainly consisting of non-metallic substances containing oxides or oxidic compounds, e.g. ferrites
  • H01C7/025—Perovskites, e.g. titanates

Definitions

• the invention relates to a method of manufacturing an electrically conducting material having a positive temperature coefficient of the resistance, and to a conductor manufactured of this material.
• An electrically conducting material is known from the Netherlands Patent Application No. 298,534 published on 25th November 1965. This material can be obtained by reducing sintering of a mixture mainly comprising magnesium oxide and containing 0.5 to 3.0% by weight of titanium dioxide and 1.0 to 3.0% by weight of silicon dioxide. This material is very suitable for the manufacture of resistors which are exposed for long periods to comparatively high temperatures during operation.
• Such resistors are frequently used as auxiliary resistors for limiting the ignition voltage in high-pressure mercury vapour discharge lamps in which the resistors are provided within the outer envelopes of the lamps.
• the resistors are brought to a temperature of, for example, 600 C. Under these circumstances the resistance of the resistor is to remain substantially constant. This requirement is satisfactorily fulfilled by the resistors manufactured of the known electrically conducting material.
• the known resistors also have satisfactory mechanical properties and maintain these properties for very long periods.
• a drawback of the known electrically conducting material is that the spread in the resistance of the conductors manufactured of this material is very large. A result thereof is that large numbers of the conductors have to be rejected because it is found that they do not have the desired resistance.
• An object of the invention is to provide a method of manufacturing an electrically conducting material in which the above-mentioned drawback does not occur or substantially does not occur.
• a mixture is preferably used which contains 0.4 to 0.9 mol percentoftitanium dioxide, 0.6 to 1.35 mole percent of silicon dioxide and furthermore 0.6 to 1.35 mol percent of calcium oxide.
• conducting materials are then obtained whose resistances are most suitable for practical uses.
• calcium oxide, titanium dioxide and silicon dioxide are present in the mixture in the molar ratio (3:0.5):(2i0.5):(3:0.5).
• the average resistance of the conductors manufactured of the material can very well be adjusted at a given desired value. This is particularly the case when the said molar ratio is substantially 3 :2:3 and this ratio is therefore preferably used.
• the value of the average resistance of the conductors in case of a constant molar ratio of the oxides is determined by the total quantity of calcium oxide, titanium dioxide and silicon dioxide in the mixture.
• a given desired value of the resistance can be adjusted by varying the total quantity of the said oxides at a constant molar ratio (preferably 3:2:3), on the understanding that the resistance is larger as the total quantity of the oxides is chosen to be smaller.
• magnesium oxide a compound from which this oxide is produced upon heating
• magnesium carbonate a compound from which this oxide is produced upon heating
• Titanium dioxide, silicon dioxide and calcium oxide may be present in the starting mixture as such or entirely or partly in a bound state, for example, as magnesium titanate or magnesium silicate.
• Calcium oxide may be used, for example, as calcium carbonate or as a coprecipitate of calcium carbonate and magnesium carbonate.
• a starting mixture is preferably used which in addition to the same constituents contains an organic binder, for example, methyl cellulose or nitrocellulose.
• an organic binder for example, methyl cellulose or nitrocellulose.
• Sintering and reducing may be effected, for example, in a gas mixture consisting of approximately vol percent of nitrogen and approximately 15 vol percent of hydrogen at temperatures of between 1700 and 2000 C. and preferably at approximately 1800 C., for example, for 5-30 minutes.
• a pulverulent mixture consisting of 97.1 mol percent of magnesium oxide, 1.1 mol percent of calcium carbonate, 0.7 mol percent of titanium dioxide and 1.1 mol percent of silicon dioxide is intimately mixed with a binder consisting of 4.8% by weight of methyl cellulose and 95.2% by weight of water and subsequently it is moulded into bars.
• the bars are dried in air and subsequently heated Pafented Aug. 20, 1974 for 60 minutes at approximately 1350 C. Subsequently the bars are heated in an atmosphere of approximately 92% by volume of nitrogen and approximately 8% by volume of hydrogen for 15 minutes at approximately 1800 C.
• Electrodes are provided in av manner known per se on the conducting bars thus obtained for use as auxiliary resistors in high-pressure mercury vapour discharge lamps.
• An electrical conductor having a'pos'itive temperature coeflicient of resistance and consi'stingessentially of the heat reaction product of 0.25 to 1.5,mollpercent1o t titanium dioxide, 0.35 to 25 mol percent of silicon dioxide and 0.35 to 2.5 mol percent of calcium .oxide, andQ- the balance principally magnesium oxide, said. electri'cal conductor being made in accordance with the. process defined in Claim 1.

Landscapes

• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Ceramic Engineering (AREA)
• Microelectronics & Electronic Packaging (AREA)
• Materials Engineering (AREA)
• Physics & Mathematics (AREA)
• Electromagnetism (AREA)
• Manufacturing & Machinery (AREA)
• Structural Engineering (AREA)
• Organic Chemistry (AREA)
• Compositions Of Oxide Ceramics (AREA)
• Ceramic Products (AREA)
• Thermistors And Varistors (AREA)

Applications Claiming Priority (1)

Publications (1)

Family

ID=19813104

Family Applications (1)

Country Status (9)

Cited By (1)

• 1971
  • 1971-05-07 NL NL7106267.A patent/NL162230C/xx not_active IP Right Cessation
• 1972
  • 1972-04-29 DE DE2221328A patent/DE2221328C3/de not_active Expired
  • 1972-05-01 US US00249389A patent/US3830758A/en not_active Expired - Lifetime
  • 1972-05-04 CA CA141,282A patent/CA982810A/en not_active Expired
  • 1972-05-04 AT AT387472A patent/AT312743B/de not_active IP Right Cessation
  • 1972-05-04 IT IT68387/72A patent/IT960375B/it active
  • 1972-05-05 BE BE783116A patent/BE783116A/xx unknown
  • 1972-05-08 GB GB2135672A patent/GB1339112A/en not_active Expired
  • 1972-05-08 FR FR7216352A patent/FR2137614B1/fr not_active Expired

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