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
  • H01C7/02—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
• • 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
  • C04B35/468—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 based on barium titanates
  • C04B35/4682—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 based on barium titanates based on BaTiO3 perovskite phase

Definitions

• the invention relates to a method of manufacturing ceramic resistance bodies for electric resistors having a positive temperature coefficient of the electric resistivity, which bodies mainly consist of semiconductive barium titanate; the invention further relates to resistance bodies thus manufactured and resistors manufactured by means of said bodies (so-called FTC-resistors).
• FTC-resistors the resistance body of which consists of semiconductive barium titanate, the electric resistance of which can increase considerably when the temperature increases to and above the ferro-electric Curie-temperature are known per se.
• resistors the ceramic resistance bodies of which consist of barium titanate in which a part of the barium ions is replaced by la ions or Sb ions or part of the Ti ions by Nb ions.
• PlC-resistors can be manufactured the said temperature-dependence of the electric resistance of which is considerably larger than of known PTC- resistors on the basis of semiconductive titanate.
• PTCresistors manufactured according to the invention show a considerably stronger increase of the electric resistance than the known resistors on the basis of semiconductive barium titanate when the temperature is increased to and above the ferro-electric Curie-temperature, or the absolute increase of the electric resistance in a given temperature range is considerably larger than of those known resistors; often both effects occur in a FTC-resistor obtained with the use of the invention.
• These FTC-resistors often have a substantially constant temperature coefficient of the electric resistance over a large temperature range.
• the FTC-resistors according to the invention can advantageously be used in those cases where electric resistors having positive temperature coefficients can be used, for example, for current limiting and stabilization in thermoregulators and voltage stabilizers, for safeguarding electric motors and for temperature and radiation measurements.
• the invention relates to a method of manufacturing a ceramic resistance body consisting of substantially pure semiconductive barium titanate which has been made semiconductive with the use of the principle of the controlled valency from a powder which substantially consists of barium titanate or substantially of compounds which are converted into barium titanate upon heating in an oxygen-containing atmosphere, characterized in that before shaping the powder is intimately mixed with a fluoride of an element of the group consisting of Ca, Sr and Ba in a quantity corresponding to 0.5 at. percent of fluorine, calculated on barium titanate present in the ceramic resistance body, to a ceramic resistance body thus manufactured and PTC-resistors manufactured by means of said body.
• the ceramic resistance bodies thereof must consist of substantially pure semiconductive barium titanate and preferably of such a barium titanate which contains a small excess, up to 3 mol. percent and preferably 1.5 2.0 mol. percent, of titanium dioxide.
• a ceramic resistance body consisting of substantially pure semiconductive barium titanate is to be understood to mean herein such a body which consists for at least 95 mol. percent of barium titanate.
• barium titanate semiconductive For making barium titanate semiconductive the known methods may be used and at least one element which introduces semiconductivity with the use of the principle of the controlled valency may be incorporated in suitable quantifies.
• elements are antimony, bismuth, niobium, cerium, yttrium, rare earth metals, for example, lanthanum.
• a fluoride is preferably used calcium fluoride.
• the quantity of fluoride to be used corresponds to 0.5 10 at. percent of fluorine, calculated on barium titanate in the ceramic resistance body. This content preferably corresponds to l 8 at. percent of fluorine and in particular to 2 6 at. percent of fluorine.
• the manufacture of ceramic resistance bodies according to the invention may be carried out, for example, as follows:
• Powders of barium carbonate, titanium dioxide and antimony oxide, (Sb O are carefully mixed, for example, by grinding, and the mixture is heated in air at l,l00 C for 60 minutes.
• the resulting product is ground.
• the fluoride to be added for example, Calis intimately mixed with the resulting powder, for example, by grinding.
• the resulting pulverulent product is given the desired shape for example, of a rod, sheet or strip, for example, by compression.
• the body thus obtained is sintered in an oxygen-containing atmosphere to form a ceramic resistance body, for example, by heating in air at l,400 C for 60 minutes.
• the resulting resistance body may be provided in known manner with ohmic electrodes and supply wires for the manufacture of PT C-resistors.
• Ceramic resistance bodies to be investigated (wafers, diameter 7.5 mms, thickness 1.85 mms) were provided with ohmic electrodes as a result of which no contact resistances occur. The electric resistance was measured at different temperatures.
• the basic composition of the ceramic bodies was the followmg:
• the ceramic bodies according to the present invention are of a fine crystallinity. Applicants suppose that this is due to a limitation of crystal growth by the influence of fluoride. Due to this the bodies show a high breakdown voltage. The high order of reproducibility in the manufacture of the resistors is also due to the said effect.
• an electric ceramic resistor having a positive temperature coefficient of electrical resistance and comprising a barium titanate body and a metal capable of inducing semiconductivity into said barium titanate and provided with at least one ohmic contact electrode, the improvement wherein said semi-conductive body contains 0.5 to at. percent inclusive of fluorine in the form of barium, calcium or strontium fluoride calculated on the barium titanate.
• a ceramic resistance body consisting of semiconductive barium titanate comprising the steps, first shaping a powder consisting substantially of barium-titanate or compounds heat-convertable to barium titanate and a compound of a metal capable of inducing semiconductivity into the barium titanate into a shaped mass and then sintering the resultant shaped mass by heating in oxygen, the improvement which comprises adding to the powder before shaping at least one fluoride of an element selected from the group consisting of Ca, Sr and Ba in a quantity corresponding to 0.5-10 at. percent of fluorine, calculated on the barium titanate present in the ceramic resistance body.

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

Applications Claiming Priority (1)

Publications (1)

Family

ID=19794963

Family Applications (1)

Country Status (8)

Cited By (2)

Families Citing this family (2)

• 1965
  • 1965-12-18 NL NL6516534A patent/NL6516534A/xx unknown
• 1966
  • 1966-12-15 CH CH1791266A patent/CH495609A/de not_active IP Right Cessation
  • 1966-12-15 AT AT1155666A patent/AT270807B/de active
  • 1966-12-15 SE SE17207/66A patent/SE318642B/xx unknown
  • 1966-12-16 GB GB56451/66A patent/GB1171756A/en not_active Expired
  • 1966-12-16 FR FR87738A patent/FR1505751A/fr not_active Expired
  • 1966-12-16 BE BE691370D patent/BE691370A/xx unknown
• 1970
  • 1970-01-26 US US6052A patent/US3674713A/en not_active Expired - Lifetime

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