JP4302487B2 - Sintered body for thermistor, thermistor element, and temperature sensor - Google Patents

Description

  The present invention relates to a thermistor element sintered body, a thermistor element, and a temperature sensor. More specifically, the temperature can be detected in a wide temperature range from a low temperature to a high temperature, and the electrical resistance value changes with respect to a high thermal history. The present invention relates to a thermistor element sintered body capable of providing a small number of thermistor elements and a temperature sensor using the thermistor element.

  A thermistor is a sintered body of a specific metal oxide whose electric resistance changes with temperature. A thermistor element formed by this sintered body and a pair of electrodes has been conventionally used in various fields. For example, it is widely used for detecting the temperature of an integrated circuit, the exhaust gas temperature of an automobile, the flame temperature of a gas water heater, and the like.

  The thermistor element sintered body that forms the thermistor element used to detect this temperature has (1) a small B constant, (2) a small resistance change with respect to thermal history, and (3) a resistance value. Small variation is required. Here, the B constant is a constant serving as an index of change in the electric resistance value with respect to a predetermined temperature range, and means that the smaller the value, the smaller the change in the electric resistance value with respect to the temperature change. The thermistor element (sintered body for thermistor element) having the required performance described above has a wide detection temperature range, excellent heat resistance, and excellent temperature detection accuracy.

As such a sintered body for the thermistor element, one having (Y, Sr) (Cr, Fe, Ti) O ₃ as a main component has been known so far (see Patent Document 1). This sintered body for thermistor element has an electric resistance value of about 100 KΩ at 300 ° C. and about 80Ω at 900 ° C., a B constant at 300 to 900 ° C. is about 8000 K, and in the temperature range of 300 to 1000 ° C., It is an excellent sintered body for thermistor elements that is stable against history. Further, a thermistor for _{Y (Cr, Mn) O 3} + Y 2 O 3 thermistor sintered body for which the main component (see Patent Document 2) and _{the (Y, Ca) CrO 3 +} 0.5YAlO 3 as a main component An element sintered body (see Patent Document 3) is also known.
JP-A-7-201526 JP 2002-124403 A JP-A-6-338402

  However, since the sintered body for the thermistor element shown in Patent Document 1 contains Ti, the B constant tends to increase. At a temperature of 300 ° C. or lower, the electrical resistance value is MΩ of the insulation resistance level. There was a problem that the temperature could not be detected in the low temperature region.

  Further, the sintered body for the thermistor element can change its component composition, for example, to make the electrical resistance value at 100 ° C. 500 Ω or less so that a temperature near 100 ° C. can be detected, There has also been a problem that the stability of the resistance temperature characteristic is easily impaired by a thermal history such as repeated exposure to a high temperature of about 1000 ° C. or continuous exposure for a long time.

  Furthermore, the sintered bodies for thermistor elements shown in Patent Documents 1 to 3 contain Cr, and since Cr is a highly volatile element, the resistance temperature characteristics of the element vary depending on the amount of volatilization. There was also a problem that was likely to occur.

  The present invention solves such a conventional problem and can detect a temperature in a wide temperature range from a low temperature of 100 ° C. or less than 100 ° C. to a high temperature in the vicinity of 900 ° C. In addition, for a high heat history. It is an object of the present invention to provide a thermistor element sintered body capable of providing a thermistor element with little change in electrical resistance value, a thermistor element including the thermistor element sintered body, and a temperature sensor using the thermistor element. To do.

  In order to solve the above-mentioned problems, the inventors have conducted various studies on the element components constituting the sintered body for the thermistor element, and as a result, at least one selected from Group 3 of the periodic table (excluding La). Contains at least one element selected from the group of elements, Group 2 of the periodic table, Mn, Al and oxygen, and contains no transition elements other than Mn and at least one element selected from Group 3 of the periodic table. By including, a sintered body for thermistor elements that can detect the temperature in a wide temperature range from low temperature to high temperature, and can provide a thermistor element with little change in electrical resistance value against high thermal history. Based on this finding, the present invention has been completed.

That is, the first means for solving the problems of the present invention is as follows:
(A) containing at least one element selected from group 3 of the periodic table (excluding La), at least one element selected from group 2 of the periodic table, Mn, Al, and oxygen, and Mn And a thermistor element sintered body characterized by being substantially free of transition elements other than at least one element selected from Group 3 of the periodic table.

As a preferable aspect in the first means,
1) The content of at least one element selected from group 3 of the periodic table (excluding La) is 1-a (mol) and at least one element selected from group 2 of the periodic table When the content is a (mole), the Mn content is b (mole), and the Al content is c (mole), the above (a) satisfying the following formulas (1) and (2): ) Of thermistor elements.
0.02 ≦ a <1 (1)
b + c = 1 (2)
In this embodiment, the Mn content b (mol) is preferably in the range of 0.10 ≦ b ≦ 0.30.

Moreover, as a preferable aspect in the first means,
2) At least one element selected from Group 3 of the periodic table (excluding La) is Y, Sc, Ce, Nd, Sm, Eu, Gd, Dy, Er, or Yb, The thermistor element sintered body according to (a) above, wherein the at least one element selected from Group 2 is Ca, Sr, Mg, or Ba.

Furthermore, as a preferable aspect in the first means,
3) The thermistor element sintered body described in (a) above containing Si element.

The second means for solving the problems of the present invention is as follows:
(B) a sintered body for the thermistor element according to (a), and a pair of electrode wires embedded in the sintered body for the thermistor element and at least one end thereof led out to extract an output signal; A thermistor element comprising:

Furthermore, the third means for solving the above-mentioned problems of the present invention is as follows:
(C) A temperature sensor comprising the thermistor element of (b).

The sintered body for the thermistor element of this invention first contains at least one element selected from Group 3 of the periodic table. However, La is excluded. If the oxide of La remains unreacted in the sintered body for the thermistor element, the unreacted substance reacts with moisture in the atmosphere to generate La (OH) ₃ , and the thermistor element (for thermistor element) This is because cracks are induced in the sintered body and the resistance value becomes unstable. Two or more of these elements may be contained.

  The periodic table refers to a periodic table according to the IUPAC 1990 recommendation [“Inorganic chemical nomenclature—IUPAC 1990 recommendation”]. J. et al. Edited by LEIGH, translated by Kazuo Yamazaki, page 43, first edition, first edition, published on March 26, 1993, Tokyo Chemical Co., Ltd.].

  The sintered body for the thermistor element of the present invention contains at least one element selected from Group 2 of the periodic table. Two or more of these elements may be contained, and the periodic table is as described above.

  It is noted that the sintered body for the thermistor element of the present invention contains Mn, Al and oxygen, but does not contain Mn and a transition element of at least one element selected from Group 3 of the periodic table. It is a point. This is because if there is a transition element other than Mn and at least one element selected from Group 3 of the periodic table, for example, Fe, Co, Ni, Ti, etc., the B constant tends to increase. In addition, although it is desirable that Mn and the transition element of at least one element selected from Group 3 of the periodic table are not contained at all in the sintered body for the thermistor element, it is extremely small in the raw material used for production (industrial). It may be unavoidably included depending on the case where it is included as an impurity and the case where it is mixed during manufacture. Therefore, in the present invention, when the sintered body for the thermistor element is measured at an acceleration voltage of 20 kV by surface analysis using EDS, for example, using a scanning electron microscope “JED-2110 type” manufactured by JEOL Ltd., If no transition element of at least one element selected from Mn and Group 3 of the periodic table is detected, substantially no transition element of Mn and at least one element selected from Group 3 of the periodic table is contained. As defined herein.

Furthermore, in the sintered body for the thermistor element of the present invention, the content of at least one element selected from Group 3 of the periodic table (excluding La) is 1-a (mol), and the periodic table 2 is used. When the content of at least one element selected from the group is a (mol), the content of Mn is b (mol), and the content of Al is c (mol), the following formula (1 ) And (2) are preferred thermistor element sintered bodies.
0.02 ≦ a <1 (1)
b + c = 1 (2)

  In particular, by setting the content a (mol) of at least one element selected from Group 2 of the periodic table to 0.02 ≦ a <1, it is stable against thermal history and has a B constant characteristic. Can bring. If the content a (mol) of at least one element selected from Group 2 of the periodic table is less than 0.02, it is not preferable because it may exhibit unstable characteristics against thermal history.

  Further, the Mn content b (mol) is preferably in the range of 0.10 ≦ b ≦ 0.30. By making the content of Mn within such a range, good temperature detection performance is provided for a wide region from a low temperature region of 100 ° C. or less than 100 ° C. to a high temperature region of 900 ° C. In addition, better temperature detection performance is brought about when the content b (mol) of Mn satisfies the range of 0.14 ≦ b ≦ 0.26.

  Furthermore, in the sintered body for the thermistor element of the present invention, at least one element selected from Group 3 of the periodic table (excluding La) is Y, Sc, Ce, Nd, Sm, Eu, Gd. , Dy, Er or Yb, among which Y is the most preferred element. In addition, at least one element selected from Group 2 of the periodic table is preferably Ca, Sr, Mg, or Ba, and among these, Ca is the most preferable element. In particular, in the sintered body for the thermistor element according to the present invention, the element selected from group 3 of the periodic table (excluding La) is Y, and the element selected from group 2 of the periodic table is Ca. Is most preferable. This is because by selecting Y and Ca in this way, it is possible to provide a thermistor element sintered body that is more stable against thermal history and has a smaller B constant.

  Furthermore, it is preferable that the sintered body for the thermistor element of this invention contains Si element. This is because the Si element not only enables firing at a low temperature in obtaining a sintered body for the thermistor element, but also increases the strength of the obtained sintered body.

  As described above, the present invention is a sintered body for a thermistor element that does not contain a transition element other than Mn and at least one element selected from Group 3 of the periodic table. For this reason, according to the present invention, due to the high volatility of Cr, the conventional problem that the variation in resistance value becomes large due to the large amount of volatilization is eliminated. A ligation is provided. Further, since the sintered body for the thermistor element of the present invention does not contain Fe, Ti, Co and Ni, the initial electric resistance value in the temperature range such as 100 ° C. or 150 ° C. becomes too large, or the B constant becomes large. The above problem is solved, and good temperature detection performance is exhibited in a wide region from a low temperature region near 100 ° C. or less than 100 ° C. to a high temperature region such as 900 ° C.

Embodiments to which the present invention is applied will be described below with reference to the drawings.
In producing the sintered body for the thermistor element of the present invention, first, the raw material of the sintered body for the thermistor element is weighed and collected so as to have a predetermined content ratio. Examples of the raw material for the thermistor element sintered body include oxides, hydroxides and carbonates of the elements constituting the thermistor element sintered body, and oxides and carbonates are particularly preferred. And the collected raw material of each element is wet-mixed by a pot mill for 5 to 30 hours, and dried to form a powder. The average particle size of each raw material powder is preferably in the range of 0.5 to 2.0 μm, and being in the range of 0.5 to 1.5 μm can disperse each raw material powder more uniformly. It is more preferable because it is possible. It should be noted that sulfates and nitrates of the above elements can also be used as raw materials for the thermistor element sintered body. In this case, it is also possible to employ a technique in which the raw material is dissolved and mixed in water, and then heated, polymerized, and dried to form a powder.

Subsequently, the mixed powder obtained by mixing the predetermined elements obtained as described above is calcined in the atmosphere at 1100 to 1500 ° C. for 1 to 10 hours, and calcined powder obtained by calcining is desired. Then, the sintering aid is mixed, wet pulverized and dried. Examples of the sintering aid include SiO ₂ and CaSiO ₃ , and among these, SiO ₂ is suitable as the sintering aid. The mixing ratio of the sintering aid is usually 0.3 to 10% by mass with respect to the calcined powder.

  Next, a binder is optionally added to the powder obtained by wet pulverization and drying (powder for thermistor sintered body), dried, and then granulated to obtain a molding granule. The average particle size of the obtained granular material is preferably 500 μm at most.

  Examples of the binder used as desired include binders mainly composed of polyvinyl alcohol, polyvinyl butyral, and the like. Although there is no restriction | limiting in particular in the usage-amount of this binder, It is 5-20 mass parts with respect to 100 mass parts of powders for the thermistor sintered bodies obtained by wet-grinding and drying, Preferably it is 10-20 mass parts.

  The sintered body for the thermistor element is manufactured by press-molding the molding granule thus obtained into a predetermined shape and firing the molded body. The firing conditions are not particularly limited, but the firing temperature is preferably 1400 to 1700 ° C, more preferably 1400 to 1600 ° C, and the firing time is preferably 1 to 5 hours, more preferably 1 to 2 hours. Moreover, although it does not specifically limit about baking atmosphere, Usually, it is air | atmosphere.

  When the thermistor element is formed using the molded body, the molded body and a pair of electrode wires made of a Pt—Rh alloy or the like are used to form a predetermined shape by press molding. Then, the thermistor element 2 shown in FIG. 1 can be obtained by firing the integrated molded body.

  The thermistor element 2 has a structure in which a pair of electrode wires 9 are embedded in the thermistor element sintered body 1 and at least one end side of the electrode wires 9 is drawn to the outside in order to take out an output signal. Further, the sintered body 1 for the thermistor element is formed in a hexagonal shape when a cross section in a direction parallel to the extending direction of the electrode wire 9 is taken. The shape of the thermistor element sintered body constituting the thermistor element is not particularly limited, and may be formed in a disk shape. In addition, the pair of electrode wires may be drawn not only from one end side but also from the other end side from the thermistor element sintered body.

  Further, the sintered body for the thermistor element and the thermistor element can be subjected to heat treatment as necessary after being sintered as described above. The heat treatment conditions are 800 to 1100 ° C., preferably 850 to 1100 ° C., more preferably 900 to 1100 ° C., 30 hours or longer, preferably 100 hours or longer, more preferably 200 hours or longer. By performing heat treatment at such a temperature and processing time, the resistance temperature characteristic of the sintered body for the thermistor element can be further stabilized. Further, the atmosphere in the case of performing the heat treatment may be an air atmosphere or a special atmosphere other than the air.

  Next, a temperature sensor using the thermistor element 2 made of the sintered body 1 for the thermistor element will be described with reference to FIG. FIG. 2 is a partially cutaway side view showing the structure of the temperature sensor 100 for detecting the exhaust gas temperature provided in the exhaust gas passage of the automobile.

  In this temperature sensor 100, the thermistor element 2 is housed in a metal tube 3 made of a bottomed cylindrical SUS310S. The metal tube 3 has its front end side 3a closed and its rear end side 3b open. A flange 4 made of SUS310S is argon welded to the rear end side 3 b of the metal tube 3. On the flange 4, a nut 5 having a hexagonal nut portion 5a and a screw portion 5b is rotatably inserted. A cylindrical joint 6 made of SUS304 is argon welded to the rear end side 4 a of the flange 4.

  Inside the metal tube 3, the flange 4, and the joint 6, a sheath 8 that includes a pair of sheath core wires 7 is disposed. The sheath 8 is made of a metal outer tube made of SUS310S, a pair of conductive sheath core wires 7 made of SUS310S, and an insulating powder that insulates the outer tube from each sheath core wire 7 and holds the sheath core wire 7. It consists of. Inside the metal tube 3, the electrode wire 9 of the thermistor element 2 is welded to the sheath core wire 7 protruding to the distal end side 8 a of the sheath 8. Inside the tip side 3 a of the metal tube 3, a nickel oxide pellet 10 is arranged.

  Further, a cement 11 is filled around the thermistor element 2. Inside the joint 6, a pair of lead wires 13 are connected to the sheath core wire 7 protruding to the rear end side 8 b of the sheath 8 via a crimping terminal 12. These lead wires 13 are enclosed in an auxiliary ring 14 made of heat-resistant rubber. The sheath core wire 7 and the lead wire 13 are connected to each other by a crimping terminal 12.

Hereinafter, the present invention will be described in more detail with reference to examples.
[Manufacture of thermistor elements]
Examples 1 to 15 and Comparative Example 1
Y ₂ O ₃ powder (purity 99.9% or more, average particle size 1.1 μm), CaCO ₃ powder (purity 99.0% or more, average particle size 0.5 μm), MnO ₂ powder (purity 99.0% or more) , Average particle size 1.2 μm) and Al ₂ O ₃ powder (purity 99.5% or more, average particle size 0.6 μm) in the formula (Y _1-a , Ca _a ) (Mn _b Al _c ) O ₃ The a, b and c were weighed so as to have the molar values shown in Table 1 and wet mixed. Then, it was dried and calcined at 1200 ° C. for 2 hours in the air. Thereafter, 1 part by mass of a sintering aid (SiO ₂ powder, purity 99.0% or more, average particle size 1.5 μm) was added to 100 parts by mass of the calcined powder in Example 1, and Example 2 ˜15 and Comparative Example 1 were wet pulverized and dried without adding SiO ₂ powder to prepare a thermistor sintered body powder.

  Subsequently, 20 parts by mass of a binder mainly composed of polyvinyl butyral is added to 100 parts by mass of the prepared powder for thermistor sintered body, mixed, dried and granulated, and then the molding granule (average grain) Diameter 106-355 μm) was obtained. Next, a hexagonal shaped body was obtained by press molding using the obtained granular body and a pair of electrode wires, and this shaped body was fired at 1550 ° C. for 1 hour to obtain a thickness of 1. A 24 mm thermistor element was manufactured.

Example 16
Sm ₂ O ₃ powder (purity 99.9% or more, average particle size 1.3 μm), SrCO ₃ powder (purity 99.0% or more, average particle size 0.5 μm), MnO ₂ powder (purity 99.0% or more) , Average particle size 1.2 μm) and Al ₂ O ₃ powder (purity 99.5% or more, average particle size 0.6 μm) in the formula (Sm _1-a , Sr _a ) (Mn _b Al _c ) O ₃ They were weighed so that a, b, and c had the molar values shown in Table 2, and wet mixed. Subsequently, it dried and calcined at 1400 degreeC for 2 hours in air | atmosphere. Thereafter, 1 part by mass of a sintering aid (SiO ₂ powder, purity of 99.0% or more, average particle size of 1.5 μm) is added to 100 parts by mass of the calcined powder, wet pulverized and dried. The powder for the thermistor sintered body was prepared. Then, the molding process of the molded body and the firing process of the molded body were performed in the same manner as in Example 1 to obtain a thermistor element.

Examples 17-19
Y ₂ O ₃ powder (purity 99.9% or more, average particle size 1.1 μm), SrCO ₃ powder (purity 99.0% or more, average particle size 0.5 μm), MnO ₂ powder (purity 99.0% or more) , Average particle size 1.2 μm) and Al ₂ O ₃ powder (purity 99.5% or more, average particle size 0.6 μm) in the formula (Y _1-a , Sr _a ) (Mn _b Al _c ) O ₃ They were weighed so that a, b, and c had the molar values shown in Table 2, and wet mixed. Thereafter, for Example 17, the calcining step, the thermistor sintered body powder preparation step after adding the sintering aid (SiO ₂ powder), the molding step, and the molding step were performed in Example 16. And thermistor element was obtained. On the other hand, for Examples 18 and 19, after the wet mixing, the same calcination step as Example 16 was performed, and the powder for the thermistor sintered body was obtained by wet grinding and drying without adding the SiO ₂ powder. Prepared. And the molding process similar to Example 1 was implemented, and the obtained molded object was baked at 1500 degreeC for 1 hour, and the 1.24-mm-thick thermistor element shown in FIG. 1 was manufactured.

Example 20
Nd ₂ O ₃ powder (purity 99.9% or more, average particle size 1.5 μm), SrCO ₃ powder (purity 99.0% or more, average particle size 0.5 μm), MnO ₂ powder (purity 99.0% or more) , Average particle size 1.2 μm) and Al ₂ O ₃ powder (purity 99.5% or more, average particle size 0.6 μm) in the formula (Nd _1-a , Sr _a ) (Mn _b Al _c ) O ₃ They were weighed so that a, b, and c had the molar values shown in Table 2, and wet mixed. Thereafter, a calcining step, a thermistor sintered body powder preparation step after adding a sintering aid (SiO ₂ powder), a forming step of the formed body, and a firing step of the formed body are performed in the same manner as in Example 16, A thermistor element was obtained.

Example 21
Gd ₂ O ₃ powder (purity 99.9% or more, average particle size 1.3 μm), SrCO ₃ powder (purity 99.0% or more, average particle size 0.5 μm), MnO ₂ powder (purity 99.0% or more) , Average particle size 1.2 μm) and Al ₂ O ₃ powder (purity 99.5% or more, average particle size 0.6 μm) in the formula (Gd _1-a , Sr _a ) (Mn _b Al _c ) O ₃ They were weighed so that a, b, and c had the molar values shown in Table 2, and wet mixed. Thereafter, a calcining step, a thermistor sintered body powder preparation step with the addition of a sintering aid (SiO ₂ powder), a molded body molding step, and a molded body firing step were carried out in the same manner as in Example 16. An element was obtained.

Example 22
Y ₂ O ₃ powder (purity 99.9% or more, average particle size 1.1 μm), MgO powder (purity 99.0) obtained by heat-treating 4MgCO ₃ .Mg (OH) ₂ .5H ₂ O at 1000 ° C. % Or more, average particle size 1.0 μm), MnO ₂ powder (purity 99.0% or more, average particle size 1.2 μm) and Al ₂ O ₃ powder (purity 99.5% or more, average particle size 0.6 μm) Was weighed so that a, b and c in the formula (Y _1-a , Mg _a ) (Mn _b Al _c ) O ₃ had the molar values shown in Table 2, and wet-mixed. Thereafter, the calcining step, the thermistor sintered body powder preparation step after adding the sintering aid (SiO ₂ powder), the molding step, and the molding step are performed in the same manner as in Example 1. A thermistor element was obtained.

Example 23
Y ₂ O ₃ powder (purity 99.9% or more, average particle size 1.1 μm), BaCO ₃ powder (purity 99.0% or more, average particle size 0.5 μm), MnO ₂ powder (purity 99.0% or more) , Average particle size 1.2 μm) and Al ₂ O ₃ powder (purity 99.5% or more, average particle size 0.6 μm) in the formula (Y _1-a , Ba _a ) (Mn _b Al _c ) O ₃ They were weighed so that a, b, and c had the molar values shown in Table 2, and wet mixed. Thereafter, the calcining step, the thermistor sintered body powder preparation step after adding the sintering aid (SiO ₂ powder), the molding step, and the molding step are performed in the same manner as in Example 1. A thermistor element was obtained.

Comparative Examples 2-4
Y ₂ O ₃ powder (purity 99.9% or more, average particle size 1.1 μm), SrCO ₃ powder (purity 99.0% or more, average particle size 0.5 μm), Cr ₂ O ₃ powder (purity 99.3) % Or more, average particle size 0.5 μm), Fe ₂ O ₃ powder (purity 99.4% or more, average particle size 0.9 μm) and TiO ₂ powder (purity 99.0% or more, average particle size 1.8 μm) Was weighed so that a, b and c in the formula (Y _1-a , Sr _a ) (Cr _1-b-c , Fe _b Ti _c ) O ₃ had the molar values shown in Table 3, and wet-mixed . Thereafter, a calcining step, a thermistor sintered body powder preparation step after adding a sintering aid (SiO ₂ powder), a forming step of the formed body, and a firing step of the formed body are performed in the same manner as in Example 16, A thermistor element was obtained.

Comparative Example 5
Y ₂ O ₃ powder (purity 99.9% or more, average particle size 1.1 μm), SrCO ₃ powder (purity 99.0% or more, average particle size 0.5 μm), MnO ₂ powder (purity 99.0% or more) , Average particle size 1.2 μm), Al ₂ O ₃ powder (purity 99.5% or more, average particle size 0.6 μm) and Fe ₂ O ₃ powder (purity 99.4% or more, average particle size 0.9 μm) Is weighed so that a, b and c in the formula (Y _1-a , Sr _a ) (Fe _1-b-c , Mn _b Al _c ) O ₃ have the molar values shown in Table 4 and wet-mixed did. Then it performs the same calcination steps as in Example 16 without the addition of SiO ₂ powder, wet grinding and dried to prepare a powder for thermistor sintered body. And the molding process similar to Example 1 was implemented, and the obtained molded object was baked at 1500 degreeC for 1 hour, and the 1.24-mm-thick thermistor element shown in FIG. 1 was manufactured.

[Evaluation]
(1) Heat durability About the thermistor element obtained by Examples 1-23 and Comparative Examples 1-5, the electrical resistance value (initial electrical resistance value, unit: k (ohm)) in each temperature shown in Table 5 was measured. Next, these thermistor element sintered bodies were subjected to continuous heat treatment at 1000 ° C. for 150 hours, and then measured for electrical resistance values at respective temperatures shown in Table 6 (electric resistance values after heat treatment, unit: kΩ). The change amount (unit: ° C.) of the electrical resistance value with respect to the initial electrical resistance value was determined by the following formula (3). As will be described later, in Comparative Examples 2 and 5, the initial electrical resistance values at 100 ° C. and 150 ° C. show large values, and temperatures below 300 ° C. cannot be detected. The electrical resistance value and the amount of change in the electrical resistance value were not measured.

Temperature converted value of change in electric resistance value = 1 / [ln (electric resistance value after heat treatment / initial electric resistance value) / B + 1 / T]] − T (3)
T is an absolute temperature (unit: K) when the electric resistance value is measured.
B is a B constant (K). The B constant was calculated by the following formula (4) using two initial electrical resistance values between temperatures having the closest relationship at each temperature shown in Table 5 measured for each example and comparative example. . For example, in Example 1, B constant between −40 ° C. and 0 ° C., B constant between 0 ° C. and 100 ° C., B constant between 100 ° C. and 300 ° C., B constant between 300 ° C. and 600 ° C., 600 ° C. Each B constant between 900 ° C. is calculated.
B constant = ln (R / R ₀ ) / (1 / T−1 / T ₀ ) (4)
R (kΩ) is an initial electric resistance value at the absolute temperature T (K).
R ₀ (kΩ) is an initial electric resistance value at the absolute temperature T ₀ (K).
In addition, T is the absolute temperature higher than _{T 0.}
Table 5 shows initial electrical resistance values, Table 6 shows electrical resistance values after heat treatment, and Table 7 shows changes in electrical resistance values.

  From Tables 5 to 7, it can be seen that in Examples 1 to 23, the change in electrical resistance with respect to the thermal history is small and is ± 10 ° C. in the entire temperature range. In Examples 2 and 9 to 15, from about 100 ° C. to 900 ° C., in Examples 3 to 7, from about 0 ° C. to 900 ° C., and in Examples 1 and 8, about −40 ° C. It turns out that it has the characteristic which can detect to -900 degreeC. Moreover, in Examples 16-18, 20, 21, and 23, it can detect to 100-900 degreeC, and it turns out that it has a stable characteristic also with respect to a heat history. Furthermore, in Examples 19 and 22, it can be detected from 0 to 900 ° C., and it can be seen that it has stable characteristics against thermal history.

  On the other hand, in Comparative Examples 1, 3, and 4, although it has the characteristic which can detect to 150-900 degreeC, it turns out from Table 7 that the electrical resistance change with respect to a heat history is remarkably large. Further, in Comparative Examples 2 and 5, as shown in Table 5, it can be seen that the initial electrical resistance value at 100 ° C. and 150 ° C. is large and a temperature of 300 ° C. or less cannot be detected.

(2) Evaluation of variation in B constant For Example 6, thermistor elements for 6 lots (Examples 6-1, 6-2, 6-3, 6-4, 6-5 and 6-6) (each lot has 50 thermistor elements), and the initial electrical resistance value (kΩ) of the thermistor elements at 0 ° C. and 900 ° C. is determined for each lot. 50 pieces of each were measured. From this initial electrical resistance value, B0-900, which is a B constant between 0 ° C. and 900 ° C., is calculated using the above equation (4), then the average value (K) of B0-900 is calculated, An average value ± 3σ of B0-900 was calculated. The following equation (5) shows how much variation (variation of the B constant) ± 3σ has with respect to the average value of B0-900 when viewed by firing lot or when 6 firing lots are summarized. Determined by
B constant variation (%) = ± 3σ / B0−900 average value × 100 (5)
The results are shown in Table 8.

  For Comparative Example 2, thermistor elements for 6 lots (Comparative Examples 2-1, 2-2, 2-3, 2-4, 2-5 and 2-6) were used to evaluate the variation of the B constant due to firing. ) Were manufactured (there were 50 thermistor elements in each lot), and the electrical resistance values of the thermistor elements at 300 ° C. and 900 ° C. were measured 50 for each lot. From this electrical resistance value, an average value (K) ± 3σ of B300-900 was calculated. Then, when looking at each firing lot or when looking at 6 firing lots, how much variation (variation of the B constant) ± 3σ with respect to the average value of B300-900 was obtained by the above formula. . The results are shown in Table 9.

  From Tables 8 and 9, the variation of the B constant in Examples 6-1 to 6-6 is different from that of Comparative Examples 2-1 to 2-6 even when viewed by firing lots and when summarized into 6 firing lots. It turns out that it is getting smaller.

It is a perspective view of the external appearance of the thermistor element using the sintered compact for the thermistor elements of this invention. It is a partially broken notch side view which shows the temperature sensor provided with the thermistor element which consists of a sintered compact for the thermistor elements of this invention.

Explanation of symbols

1 Sintered body for thermistor element 2 Thermistor element 3 Metal tube 4 Flange 5 Nut 6 Joint 7 Sheath core wire 8 Sheath 9 Electrode wire 100 Temperature sensor

Claims (7)

At least one element selected from group 3 of the periodic table (excluding La), at least one element selected from group 2 of the periodic table, Mn, Al, and oxygen, and Mn and the period A sintered body for a thermistor element, characterized by being substantially free of transition elements other than at least one element selected from Table 3 group. The thermistor element sintered body according to claim 1,
The content of at least one element selected from Group 3 of the periodic table (excluding La) is 1-a (mol) and the content of at least one element selected from Group 2 of the periodic table Sinter for thermistor elements satisfying the following formulas (1) and (2), where a is a mol, the content of Mn is b (mol), and the content of Al is c (mol): body.
0.02 ≦ a <1 (1)
b + c = 1 (2) The thermistor element sintered body according to claim 2,
A sintered body for the thermistor element, wherein the Mn content b (mol) is in the range of 0.10 ≦ b ≦ 0.30. The thermistor element sintered body according to any one of claims 1 to 3,
At least one element selected from Group 3 of the periodic table (excluding La) is Y, Sc, Ce, Nd, Sm, Eu, Gd, Dy, Er, or Yb, and Group 2 of the periodic table A thermistor element sintered body, wherein at least one element selected from the group consisting of Ca, Sr, Mg, and Ba. A thermistor element sintered body according to any one of claims 1 to 4,
A sintered body for thermistor element containing Si element. A sintered body for the thermistor element according to any one of claims 1 to 5,
A thermistor element comprising: a pair of electrode wires embedded in the sintered body for the thermistor element and having at least one end portion led out to take out an output signal. A temperature sensor comprising the thermistor element according to claim 6.