Compositions – Electrically conductive or emissive compositions – Free metal containing
Patent
1998-05-18
2000-11-07
Kopec, Mark
Compositions
Electrically conductive or emissive compositions
Free metal containing
2525213, 2525195, 2525202, 2525211, 2525215, 338 22R, 264617, H01B 108, H01C 710
Patent
active
061432075
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a thermistor material and a method for producing it. More precisely, the invention relates to a wide-range thermistor material and a method for producing it.
BACKGROUND ART
Thermistor materials are those for resistors which are sensitive to temperature and of which the resistance varies depending on temperature, and the materials are used, for example, in various temperature sensors, fuel level gauges, switching powers, humidity sensors and anemometers.
Temperature sensors comprising conventional thermistor materials are problematic in that they are applicable to limited temperature range. For example, oxides of Mn, Co, Ni and Fe are used in low-temperature range sensors (from -30.degree. C. to 300.degree. C. or so); MnO--NiO--Cr.sub.2 O.sub.3 --ZrO.sub.3, SiC, and MgAl.sub.2 O.sub.4 --Cr.sub.2 O.sub.3 are in middle-temperature range sensors (from 200.degree. C. to 800.degree. C. or so); and ZrO.sub.2 --Y.sub.2 O.sub.3, and MgO--Al.sub.2 O.sub.3 --Cr.sub.2 O.sub.3 --Fe.sub.2 O.sub.3 are in high-temperature range sensors (from 700.degree. C. to 1200.degree. C. or so). For wide-range use, a plurality of those temperature sensors of different thermistors applicable to different temperature ranges must be used in combination.
To solve the problems in the prior art, various techniques have heretofore been proposed. One is "a high-temperature range thermistor" comprising a composite oxide of NiO--MgO in which NiO is from 30 to 99.9% by weight and MgO is from 0.01 to 70% by weight (see Japanese Patent Application Laid-Open No. 6-163206). They say that the high-temperature range thermistor exhibits wide-range temperature-dependent resistance changes, while indicating different resistance values and B constants varying in wide range, and has good direct current load life characteristics at high temperatures.
Another is "a high-temperature range thermistor" which comprises a sintered material of a mixture of (Mn.cndot.Cr)O.sub.4 spinel having a high resistance value and a high temperature coefficient of resistance, and YCrO.sub.3 having a low temperature coefficient of resistance, and of which the resistance value and the temperature coefficient of resistance are variable in wide range (see Japanese Patent Application Laid-Open No. 5-62805). They say that the high-temperature range thermistor has a lot of latitude for its resistance value and its temperature coefficient of resistance.
Still another is "a high-temperature range, ceramic thermistor material" which comprises a perovskite-structured ceramic material such as LaAlO.sub.3 or LaCrO.sub.3 and which is used in high temperature range of 300.degree. C. or higher (see Japanese Patent Publication No. 53-27480).
Still another is a "temperature sensor" comprising a solid solution of P-type conductive Cr.sub.2 O.sub.3 and N-type conductive Fe.sub.2 O.sub.3 in corundum-structured, high-resistance Al.sub.2 O.sub.3 (see Japanese Patent Application Laid-Open No. 6-283310). They say that the sensor can detect temperatures falling between 300.degree. C. and 1000.degree. C., and that, since the crystal of the solid solution constituting the sensor comprises both the P-type substance and the N-type substance, the time-dependent variation in the electrical resistance value of the sensor is small at the elevating temperature in the long time.
Still another is "a method for producing multi-functional ceramics", which comprises a step of mixing a granular material that comprises a ceramic powder and a powdery substance that is finer than the granular material with rolling them to thereby make the surfaces of the grains of the granular material uniformly (and completely) coated with the powdery substance, and a step of compacting the powdery substance-coated, granular material into a green body, followed by sintering the green body (see Japanese Patent Publication No. 7-74104).
Still another is "an electric resistor" which is composed of, as a whole, a nitride selected from a group consisting of silicon nitride, aluminium nitr
REFERENCES:
patent: 4110260 (1978-08-01), Yamamoto et al.
patent: 4906968 (1990-03-01), Gershenfeld et al.
patent: 5637543 (1997-06-01), Iwaya et al.
Asai Mitsuru
Kamiya Nobuo
Matsubara Yuko
Yamada Katsunori
Kabushiki Kaisha Toyota Chuo Kenkyusho
Kopec Mark
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