JPH11251109A - Thermistor element and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To constitute a thermistor element to have resistance value stability, when the element is exposed to a reducing atmosphere. SOLUTION: A pair of lead wires 11 and 12 is imparted to a thermistor element 1. The thermistor element 1 is constituted by forming an anti-reduction film 14 composed of an anti-reduction composition, such as Y2 O3 , Al2 O3 , SiO2 , Y3 Al5 O12 , 3Al2 O3 .2SiO2 , Y2 SiO5 , etc., on the surface of a thermistor section 13 consisting of a mixed sintered body (or Y(CrMn)O3 .Y2 O3 (or Y(CrMn)O3 .Al2 O3 ), etc.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermistor element used in a high temperature range, and is particularly suitable for use as a temperature sensor for automobile exhaust gas.

[0002]

2. Description of the Related Art Conventionally, this type of thermistor element has
It is used to measure the temperature of automobile exhaust gas, gas fire temperature of gas water heaters and the like, temperature of heating furnace, etc. in the medium to high temperature range of 400 to 1300 ° C. As a material having resistance characteristics suitable for this type of thermistor element, an oxide material (for example, a perovskite-based material) is mainly used, and for example, JP-A-6-325907 and JP-A-7-201528. Japanese Patent Application Laid-Open Publication No. H10-202,279 has been proposed. In order to realize a thermistor element usable in a wide temperature range from a medium temperature to a high temperature range, Y, Sr, C
mixing oxides such as r, Fe, Ti, etc. at a predetermined composition ratio,
This was fired to obtain a complete solid solution to form a thermistor element.

[0003]

When the above-mentioned thermistor element is used as a temperature sensor for detecting the temperature of exhaust gas from automobiles, the tip of the temperature sensor is generally detected for the purpose of preventing accumulation of dust, soot and the like in the detected gas. The thermistor element arranged in the section is covered with a metal cap. Here, the metal cap is thermally oxidized by high-temperature exhaust gas heat of about 900 ° C. or the like, so that the inside of the metal cap becomes a reducing atmosphere, and the internal thermistor element is subjected to a reducing action and the resistance value changes. .

For this reason, the temperature sensor is usually placed in an electric furnace and subjected to a heat aging treatment at 900 to 1000 ° C. for about 100 hours to stabilize the resistance value. If air enters the cap due to the opening of the hole or the cap loosening, etc., and the thermistor element itself is again exposed to the reducing atmosphere,
The change in the resistance value may occur.

In Japanese Patent Application Laid-Open No. 9-69417, a special metal material such as Inconel 600 (trademark) is selected as a metal cap and processed into a cap, and the thermistor element itself is reduced. The problem of resistance change when exposed to atmosphere has not been solved. In any case, when the thermistor element itself is exposed to a reducing atmosphere in a temperature sensor or the like, there is no thermistor element having resistance value stability.

In view of the above problems, an object of the present invention is to provide a thermistor element having a resistance value stability when exposed to a reducing atmosphere.

[0007]

Means for Solving the Problems If the present inventors try to eliminate the movement of oxygen atoms from the thermistor element material constituting the thermistor element in a reducing atmosphere, the thermistor element itself is not reduced and the resistance does not change. I thought it might be. By focusing on forming a reduction-resistant composition that does not easily react with oxygen on the thermistor element surface, and as a result of an experimental study, it was confirmed that the resistance change of the thermistor element itself was suppressed.

The invention according to claim 1 and claim 2 has been made based on the results of the above-mentioned study, and is formed on the thermistor portion (13) made of a thermistor material and on the surface of the thermistor portion (13). A reduction-resistant coating (14) made of a reduction-resistant composition.
Here, the reduction-resistant composition can be formed by fixing the organometallic compound as a precursor to the surface of the thermistor portion (13) and then firing the composition.

According to the present invention, since the surface of the thermistor element is configured to be covered with the reduction resistant film (14), the resistance value stability can be maintained even when the thermistor element itself is exposed to a reducing atmosphere. It is possible to provide an element configuration having By the way, when a thermistor element is used as a temperature sensor, a pair of electric wiring members (for example, metal lead wires) for detecting a temperature from a change in resistance of the element are usually electrically connected to the thermistor element. When the thermistor element (1) according to claim 1 or 2 is used as a temperature sensor, the pair of electric wiring members are
It is configured to penetrate the reduction-resistant film (14) as a surface layer and conduct to the internal thermistor portion (13).

Therefore, in order to prevent an electric short circuit between the pair of electric wiring members, it is preferable that the reduction resistant coating (14) has electric insulation. According to the study of the present inventors, it has been found that the reduction-resistant composition constituting the reduction-resistant coating (14) preferably has higher electric resistance than the thermistor material constituting the thermistor portion (13). .

The invention according to claim 10 is based on the knowledge about the electric resistance of the reduction-resistant composition, and in the temperature sensor (100), the electric resistance between the pair of electric wiring members (11, 12). Insulation can be ensured. Further, from the above-described studies, it can be said that the reduction-resistant composition constituting the reduction-resistant coating (14) preferably does not pass oxygen and has a high resistance value. As such, it has been found that the compositions according to claims 3 and 4 are practically desirable.

That is, in the invention according to the third aspect, the reduction resistant composition contains one or more elements selected from Y (yttrium), Al (aluminum), and Si (silicon). In the invention described in Item 4, Y ₂ O
₃ (yttria), Al ₂ O ₃ (alumina), SiO _{2
(Silica), Y 3 Al 5 O 12} (YAG, yttrium -
Aluminum - Garnet), 3Al ₂ O ₃ · 2SiO
₂ (Mullite) and one or more types of compositions selected from Y ₂ SiO ₅ .

Further, the invention according to claim 5 can provide a thermistor element used at a temperature of 900 ° C. or higher, which tends to be in a reducing atmosphere, and which has resistance value stability. The thermistor (1
On the surface of 3), a reduction-resistant coating (1) made of a reduction-resistant composition
A method for manufacturing a thermistor element formed by the method 4), that is, a method for manufacturing a thermistor element according to claims 1 to 5 was also studied. Claims 6 to 9
The described invention has been made on a method for manufacturing this thermistor element.

According to a sixth aspect of the present invention, after forming a precursor of the reduction resistant composition on the surface of the thermistor part (13), the precursor is fired to form a reduction resistant coating (14) on the thermistor part (13). A method for manufacturing a thermistor element formed on a surface and having the effects of the first aspect of the present invention can be provided. According to a seventh aspect of the present invention, an organometallic compound is used as the precursor of the sixth aspect.
A method for manufacturing the described thermistor element may be provided. Here, as the organometallic compound, an alcoholate (metal alkoxide) composition containing at least one element selected from Y, Al, and Si is practically desirable. A method for manufacturing a thermistor element according to claim 4 can be provided.

Further, in the invention according to claim 9, the thermistor portion (13) is subjected to dip coating using a solution containing an organometallic compound, so that the precursor of the reduction-resistant composition is converted to the thermistor portion (13). The method is characterized in that the precursor is fixed to the surface of 13), and the precursor can be fixed more easily as compared with spraying or application using a spinner.

The reference numerals in parentheses of the above-mentioned means indicate the correspondence with the concrete means described in the embodiments described later.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION In the present embodiment,
In the temperature range of 1000 ° C., the resistance is set to 50Ω to 100Ω.
The present invention is applied to a thermistor element having a kΩ (hereinafter, referred to as a wide-range thermistor element). The thermistor element of the present embodiment is used, for example, as a temperature sensor for detecting the temperature of automobile exhaust gas.

FIG. 1 is an explanatory diagram showing a schematic cross-sectional configuration of the thermistor element 1 of the present embodiment. Thermistor element 1
Is a thermistor portion 13 formed of a thermistor material formed in a bulk having a predetermined shape, and a reduction-resistant coating 14 formed of a reduction-resistant composition formed on substantially the entire surface of the thermistor portion 13.
It is composed of Here, according to the study of the present inventors, the thermistor material forming the thermistor portion 13 is made of a perovskite-based material having a relatively low resistance value and a relatively high resistance value in order to form a wide-range thermistor element. A mixed sintered body obtained by mixing two kinds of compounds with a material having the following is preferred.

According to the study of the present inventors, as the perovskite-based material, the composition (M1M2) O ₃ (where,
M1 is at least one element selected from Group 2A elements of the periodic table and elements of Group 3A excluding La;
M2 is preferably at least one element selected from Group 3B, Group 4A, Group 5A, Group 6A, Group 7A and Group 8 of the Periodic Table of the Elements.

La is not used as M2 because it has high hygroscopicity and has a problem that it reacts with moisture in the air to form an unstable hydroxide and destroy the thermistor element. Further, specifically, each element in (M1M2) O ₃ is M1
Are Mg, Ca, Sr, Ba (the above is 2A of the periodic table)
Group), Y, Ce, Pr, Nd, Sm, Eu, Gd, D
one or more elements selected from y, Ho, Er, Yb, and Sc (the above group 3A), wherein M2 is Zn (2B
Group), Al, Ga (above, group 3B), Ti, Zr, H
f (more than 4A), V, Nb, Ta (more than 5A)
Group, Cr, Mo, W (above, group 6A), Mn (group 7)
Group A), Fe, Co, Ni, Ru, Rh, Pd, Os,
It is practically desirable to be at least one element selected from Ir and Pt (the above, Group 8).

Materials having a relatively high resistance include:
According to the study of the present inventors, Y ₂ O ₃ (yttrium oxide) or Al ₂ O ₃ (aluminum oxide) has a relatively high resistance value and stabilizes the resistance value of the thermistor material.
Is preferred. Then, by mixing and sintering (M1M2) O ₃ and Y ₂ O ₃ , a mixed sintered body (M1M2) O _3.
A thermistor 13 made of Y ₂ O ₃ is obtained, and (M1
M2) to obtain the O ₃ and Al ₂ O ₃ and mixed sintered body by mixing sintering _{(M1M2) O 3 · Al 2} O 3 thermistor 13 consisting of. The method of mixed sintering will be described later.

On the other hand, the reduction-resistant coating 14 is made of an electrically insulating, reduction-resistant composition that is hardly permeable to oxygen and has a higher electrical resistance than the thermistor material constituting the thermistor portion 13 (that is, the mixed sintered body). It is configured. Here, as the reduction resistant composition, specifically, a composition containing one or more elements selected from Y, Al, and Si can be selected. For example, Y ₂ O ₃ (yttria), Al ₂ O ₃ ( Alumina), SiO ₂ (silica), Y ₃ Al ₅ O ₁₂ (YA
G) 3Al ₂ O ₃ .2SiO ₂ (Mullite), Y ₂ S
one or more compositions selected from iO ₅ can be selected.

As shown in FIG. 1, the thermistor element 1 has a pair of lead wires (electric wiring members) 11 and 12 made of platinum or the like for detecting a temperature from a change in resistance of the element.
Is provided. One end of each of the lead wires 11 and 12 penetrates the reduction-resistant coating 14 and is embedded in the thermistor 13. The embedded portions of the lead wires 11 and 12 in the thermistor 13 are not shown, but are arranged at a predetermined interval from each other.

Here, as described above, the reduction-resistant composition has higher electrical resistance than the thermistor material forming the thermistor portion 13 and has insulating properties.
4 can prevent an electrical short circuit between the two lead wires 11 and 12. Then, the thermistor element 1 provided with the lead wires 11 and 12 is incorporated in the temperature sensor 100 as shown in FIG. FIG. 2 is an explanatory diagram showing the temperature sensor 100 in a state where the inside of the metal cap is seen through,
FIG. 3 is a sectional view taken along line AA of FIG. Here, 2 is a cylindrical metal cap, and 3 is a metal pipe. Lead wire 11, 1
The thermistor element 1 provided with 2 is disposed inside the metal cap.

The ends of the lead wires 11 and 12 opposite to the portion embedded in the thermistor portion 13 are connected to a lead wire 31 for exchanging signals with an external circuit (for example, an ECU of an automobile). 32 is electrically connected. The connecting portion of the two lead wires 11, 12, 31, 32 may be inside or outside the metal pipe 3. In addition, as shown in FIG.
The inside of the metal pipe 3 is filled with magnesia powder 33 to ensure insulation of the lead wires 31 and 32 in the metal pipe 3.

The metal cap 2 is fixed to the outer periphery of the metal pipe 3 by caulking or the like, and the inside of the metal cap 2 is a closed space. Next, a method for manufacturing the thermistor element 1 of the present embodiment will be described. First, a case where a mixed sintered body (M1M2) O ₃ .Y ₂ O ₃ is used as the thermistor portion 13 will be described. The manufacturing process in this case is roughly divided into a first and a second preparation process.

Firstly, M1 and is a starting material M1 oxides of M2 oxides (M1O _X) and M2 a (M2O _X) or the like is blended to achieve the desired resistance value and resistance temperature coefficient (Formulation 1) , Pulverization using a medium stirring mill etc. (mixing process)
And then calcining (for example, about 1100 ° C. to 1300 ° C.)
(Temporary firing step). In this way, (M
1M2) Obtain an O ₃ · Y ₂ O ₃ composition. The above is the first preparation step.

Then, the obtained calcined body is weighed in a predetermined amount (formulation 2), the weighed calcined body is crushed (crushing step), a lead wire such as Pt is incorporated, and a mold is formed into a desired shape. After forming (forming step), baking (for example, at 1400 ° C.)
To about 1600 ° C.) (firing step). Thus, a mixed sintered body (thermistor portion 13) provided with the lead wires 11 and 12 is obtained.

Subsequently, the precursor of the reduction-resistant composition is fixed in a solution state on the surface of the thermistor section 13 by dip coating (dip coating step) and baked (for example, at 1200 ° C. or higher) (film forming step). Thus, the thermistor element 1 on which the reduction resistant film 14 is formed is obtained. The above is the second preparation step. Next, a case where a mixed sintered body (M1M2) O ₃ .Al ₂ O ₃ is used as the thermistor portion 13 will be described. The production process in this case is also largely divided into a first and a second preparation process, but after obtaining the calcined body (M1M2) O ₃ in the first preparation process,
Is different in that the calcined body and Al ₂ O ₃ are mixed so as to have a desired resistance value and a desired temperature coefficient of resistance.

First, in the first preparation step, M1 and M2
Preparation 1, mixing step and pre-baking step are performed from the raw material of (1) to obtain a (M1M2) O ₃ composition as a pre-baked body. In the second preparation step, the obtained calcined body is weighed in a predetermined amount, and the calcined body weighed so as to have a desired resistance value and a temperature coefficient of resistance is blended with Al ₂ O ₃ (formulation). 2). The weighed mixture is subjected to a pulverizing step, a forming step, and a baking step to obtain a mixed sintered body (thermistor section 13) provided with lead wires 11, 12. Subsequently, a dip coating step and a film forming step are performed to obtain the thermistor element 1.

The mixed sintered body (M1M2) O ₃ .Y ₂
Also in the case of O ₃ , (M1M2) O ₃ as a calcined body is obtained in the first preparation step, and the desired resistance value and resistance temperature coefficient are obtained in Formulation 2 of the second preparation step. Then, a pre-sintered body (M1M2) O ₃ and Y ₂ O ₃ may be mixed together, and the mixture may be subjected to a firing step to obtain a mixed sintered body (M1M2) O ₃ .Y ₂ O ₃ .

Here, in the dip coating step, a solution containing an organometallic compound can be used. As the organometallic compound, an alcoholate (metal alkoxide) containing one or more elements selected from Y, Al, and Si can be used. By performing dip coating using a solution containing these organometallic compounds, an organometallic compound as a precursor of the reduction-resistant composition is fixed as a solution on the surface of the thermistor portion 13. Then, by subjecting to a film forming step, a reduction resistant film 14 made of Y ₂ O ₃ , Al ₂ O ₃ , Y ₃ Al ₅ O ₁₂ , mullite, Y ₂ SiO _5, etc. as a reduction resistant composition is formed. Is done.

Incidentally, in the above Formulation 1 or Formulation 2, it is preferable to add a sintering aid in order to improve the sinterability of each particle in the mixed sintered body. According to the study of the sintering aid by the present inventors, in order to obtain a thermistor element excellent in sintering density, CaO, CaCO ₃ , C
It is more preferable to use at least one or more sintering aids selected from aSiO ₃ and SiO ₂ . By adding the sintering aid, the sintering density is further improved, the resistance value of the thermistor element can be stabilized, and the variation of the resistance value with respect to the fluctuation of the firing temperature can be reduced.

The thermistor element 1 thus obtained
The thermistor portion 13 is made of a perovskite compound (M1M2) O ₃ and Y ₂ O ₃ (or Al ₂ O ₃ ) uniformly mixed via a grain boundary. Also,
The temperature sensor 100 using the thermistor element 1 is placed in a high-temperature furnace, and the resistance, the temperature coefficient of resistance β, and the resistance change rate ΔR during thermal aging at 900 ° C. are measured from room temperature (for example, 27 ° C.) to 1000 ° C. did. Here, since the thermistor element 1 is affected by the reducing atmosphere in the metal cap 2 due to this thermal aging, the resistance change rate ΔR is an index for stabilizing the resistance value of the thermistor element 1 of the present embodiment.

Here, β is β (K) = Ln (R / Ro)
/ (1 / K-1 / Ko). Here, Ln represents a natural logarithm, and R and Ro represent resistance values of the thermistor element at room temperature (300 K) and 1000 ° C. (1273 K) in the atmosphere, respectively. The resistance change rate ΔR represents the resistance change of the thermistor element 1 in a reducing atmosphere by each temperature sensor as described above, and is expressed by the following equation: ΔR (%) = (Rma
xt / Rt) .times.100-100. Note that Rt
Is an initial resistance value at a predetermined temperature t (for example, 600 ° C.),
Rmax t indicates the maximum resistance value of Rt during thermal aging at 900 ° C.

As a result, in the temperature range from room temperature to 1000 ° C., Rt is 50Ω to 100 kΩ and β is 200Ω.
It was confirmed that it could be adjusted to 0 to 4000 (K) and ΔR could be stably realized at a level of about + (plus) several% (see FIGS. 5 and 7). Therefore, according to the present embodiment, by adopting an element configuration in which the reduction resistant film 14 is formed,
Even when the device itself is exposed to a reducing atmosphere, the thermistor element 1 having a small resistance change rate ΔR and having stable characteristics (resistance value stability) can be provided.

According to the present embodiment, the high temperature (900
It is not necessary to perform thermal aging treatment for a long time (about 100 hours) for about 100 ° C.), so that the number of manufacturing steps can be reduced and the cost of the sensor can be reduced. In addition, since the thermistor portion 13 is made of the above-described mixed sintered body, the resistance value has a good resistance value temperature characteristic of 50 Ω to 100 kΩ in a temperature range of room temperature to 1000 ° C. A detectable thermistor element can be provided.

Further, in order to more reliably realize the above-mentioned resistance value (Rt) range and each value of β, according to the study of the present inventors, the mixed sintered body a (M1M2) O ₃ .bY ₂ In O ₃ and a (M1M2) O ₃ .bAl ₂ O ₃ , the respective molar fractions a and b are such that 0.05 ≦ a <1.0 and 0 <b ≦ 0.9.
5, it is preferable to satisfy the relationship of a + b = 1. Further, in the mixed sintered body, since the molar fraction can be changed in such a wide range, (M1M2) O ₃ and Y ₂
By appropriately mixing and firing O ₃ (or Al ₂ O ₃ ), the resistance value and the temperature coefficient of resistance can be variously controlled in a wide composition range.

Next, in this embodiment, the following
Examples 1 to 10 and Comparative Examples 1 and 2 will be described more specifically.
As will be described, the present embodiment is not limited to these examples.
Not. In the first to fifth embodiments, the thermistor unit 13 is used.
Mixed sintered body (M1M2) O_Three・ Y _TwoO_ThreeAnd M1
Is Y, M2 is Cr and Mn, that is, mixed firing
Consolidated Y (CrMn) O_Three・ Y_TwoO_ThreeAlso made about
In Examples 6 to 10, the mixing of the thermistor unit 13 was performed.
Sintered body (M1M2) O_Three・ Al_TwoO_ThreeAnd M1 is
Y and M2 are Cr and Mn, that is, mixed sintering
Body Y (CrMn) O_Three・ Al_TwoO_ThreeAlso made about
It is.

[0040]

(Embodiment 1) In this embodiment 1, Y ₂ O ₃ (M1
Mixed raw material ₃ using, as raw materials, Cr ₂ O ₃ , Mn ₂ O ₃ (above, the raw material of M2) and CaCO ₃ (sintering aid) as raw materials.
8Y (Cr _0.5 Mn _0.5 ) O ₃ .62Y ₂ O ₃ (a =
0.38, b = 0.62))
And a reduction resistant film 14 made of Y ₂ O ₃ (reduction resistant composition) is formed on the surface of the thermistor 13.

FIG. 4 shows a manufacturing process of the thermistor element of the first embodiment. In addition, the manufacturing process of Example 2 to Example 5 is also shown in FIG. Y ₂ O having a purity of 99.9% or more
₃ , Cr ₂ O ₃ , Mn ₂ O ₃ and CaCO ₃ were prepared.
In formulation 1, aY (Cr _0.5 Mn _0.5 ) O _3.
Y ₂ O ₃ , Cr ₂ O _3, and Mn ₂ O ₃ were weighed so that a and b of bY ₂ O ₃ became a: b = 38: 62, and the total amount was 2000 g. Further, 36 g of CaCO ₃ was added,
2036 g of the total of Y ₂ O ₃ , Cr ₂ O ₃ , Mn ₂ O ₃ and CaCO ₃ was used as a mixed raw material.

Next, in the mixing step, a medium stirring mill was used to atomize the mixed raw material. The medium stirring mill of this example is a pearl mill (RV1 manufactured by Ashizawa Corporation).
V, effective volume: 1.0 liter, actual volume: 0.5 liter). The mixing conditions using this pearl mill device are as follows:
As a grinding medium, 3.0 kg of zirconia balls having a diameter of 0.5 mm was used, and 80% of the volume of the stirring tank was filled with the zirconia balls.

The operating conditions were a peripheral speed of 12 m / sec and a rotation speed of 3110 rpm. To 2036 g of the mixed raw material, 4.5 liters of distilled water was used as a dispersion medium, and at the same time, a dispersant and a binder were added, followed by mixing and grinding for 10 hours. As the binder, polyvinyl alcohol (P
VA) was added in an amount of 20 g per 2036 g of the mixed raw material. As a result of evaluating the mixed and pulverized raw material slurry of the thermistor material with a laser particle size meter, the average particle size was 0.4 μm (micron meter).

Subsequently, the obtained raw material slurry was spray-dried at a drying chamber inlet temperature of 200 ° C. and an outlet temperature of 120 ° C.
It dried under the conditions of ° C (drying process). The obtained thermistor raw material powder was spherical with an average particle diameter of 30 μm.
A crucible made of 9.3% Al ₂ O _{3 is} baked in a high-temperature furnace at 1100 ° C. to 1300 ° C. for 1 to 2 hours in the atmosphere, and a calcined body Y (Cr _0.5 Mn _0.5 ) O ₃ .Y ₂ O ₃ Was obtained (temporary firing step).

Next, the preliminarily calcined body which was formed into a lump solid by preliminarily calcining was coarsely pulverized with a raikai machine and passed through a # 30 mesh sieve to obtain a predetermined amount of Y (Cr _0.5 Mn _0.5 ) O ₃ .Y ₂ O _Three
Was obtained (Formulation 2). Next, in the pulverization step (shown as mixing / pulverization in the figure), Y (Cr _0.5 Mn _0.5 ) O ₃
A pearl mill was used in the same manner as in the above mixing step in order to atomize the Y ₂ O ₃ powder. The pulverization conditions by the pearl mill device are the same as the conditions in the mixing step. In the pulverizing step, a dispersant, a binder, and a release agent were added, and pulverized at the same time to obtain a slurry. As a result of evaluating the raw material slurry of the pulverized thermistor material with a laser fineness meter, the average powder diameter was 0.3 μm (micrometer).

Y (Cr _0.5 Mn _0.5 ) O ₃ obtained after pulverization
The Y ₂ O ₃ slurry is pulverized with a spray dryer in the same manner as in the drying step, and Y (Cr _0.5 Mn _0.5 ) O _3.
A granulated powder of Y ₂ O ₃ was obtained (granulation / drying step). The thermistor 13 was formed using the granulated powder. The molding process is performed by a mold molding method, and Pt100 (φ0.3
mm × 10.5 mm) as the lead wires 11 and 12, the above-mentioned granulated powder is put into a female mold having an outer diameter of 1.89 mm, and molded at a pressure of about 1000 kgf / cm ² to give the lead wires 11 and 12. A molded body of the thermistor part 13 thus obtained was obtained.

In the firing step, the compacts were arranged on a corrugated setter made of Al ₂ O ₃ ,
Baking for 2 hours, mixed sintered body 38Y (Cr _0.5 Mn _0.5 )
A shape composed of O ₃ · 62Y ₂ O ₃ φ1.6 mm × 1.2
Thus, a small bulk type thermistor 13 having a thickness of 1 mm was obtained. next,
Thermistor section 13 to which these lead wires 11 and 12 are attached
A reduction resistant composition is formed on the surface of the substrate. First, in the dip coating step, an yttrium organometallic compound (yttrium alkoxide in this example), which is a precursor of the reduction-resistant composition Y ₂ O ₃ , was fixed to the surface of the thermistor portion 13.

The yttrium organometallic compound is fixed to the surface of the thermistor section 13 by using an yttrium organometallic compound solution (SYM-Y01, manufactured by Symmetrics, USA).
, The thermistor 13 was immersed in this solution, and the thermistor 13 was pulled up from the solution to perform dip coating. Thus, the reduction resistant composition Y ₂ O
_The organometallic compound of yttrium as the precursor of No. ₃ was fixedly formed on the surface of the thermistor portion 13.

Thereafter, the solvent contained in the yttrium organometallic compound solution is vaporized in an air atmosphere at room temperature to 40 ° C., and the thermistor 13 having the precursor fixed on the surface is fired at 1200 ° C. or more, The thermistor element 1 was obtained in which the reduction-resistant composition was formed on the surface of the thermistor portion 13 as the reduction-resistant coating 14 with a thickness of 0.5 to 5.0 μm (coating forming step).

The thermistor element 1 provided with the lead wires 11 and 12 is assembled as shown in FIG.
And This temperature sensor 100 is placed in a high-temperature furnace, and has a resistance characteristic (resistance value,
β, ΔR) were evaluated. FIG. 5 shows the evaluation results. In addition,
The predetermined temperature t in ΔR (%) = (Rmax t / Rt) × 100-100 was 600 ° C.

The temperature sensor 100 according to the first embodiment has a resistance of 50Ω to 10Ω in a temperature range of room temperature to 1000 ° C.
Since the resistance is in the range of 0 kΩ and has good resistance-temperature characteristics, it is possible to provide a thermistor element capable of detecting the temperature over a high temperature range from room temperature to 1000 ° C. Further, in the temperature sensor 100 of the first embodiment, it was confirmed that the maximum resistance change rate ΔR of the thermistor element 1 in the metal cap can be stably realized at a level of about 3%.

Therefore, according to the thermistor element 1 of the present embodiment,
Conventionally, the temperature sensor is heat-aged at about 900 ° C. to stabilize the element resistance (see a comparative example described later).
In addition, it is not necessary to use a cap made of an expensive special metal material, and it is possible to provide a temperature sensor having resistance value stability even when the thermistor element 1 itself is exposed to a reducing atmosphere.

(Embodiment 2) In Embodiment 2, after obtaining the thermistor 13 in the same manner as in Embodiment 1, Al ₂ O ₃ is formed on the surface of the thermistor 13 as a reduction resistant composition. . In the same manner as in Example 1, the process up to the firing step was performed to obtain a thermistor portion 13 provided with the lead wires 11 and 12. The thermistor portion 13 is similarly made of the mixed sintered body 38Y (Cr _0.5
Mn _0.5 ) O ₃ · 62Y ₂ O ₃ .

Next, in the dip coating step, the surface of the thermistor portion 13 is coated with a reduction-resistant composition Al ₂ O ₃
An aluminum organometallic compound (aluminum alkoxide in this example) as a precursor of was fixed. Al ₂ O ₃
Solution of aluminum organometallic compound (SY
Using M-AL04 (manufactured by Symmetrics Corporation, USA), dip coating was performed in the same manner as in Example 1 to form a precursor of the reduction-resistant composition Al ₂ O ₃ .

Thereafter, in the film forming step, the first embodiment was used.
Similarly to the above, the thermistor element 1 in which the reduction-resistant composition was formed as the reduction-resistant coating 14 on the surface of the thermistor portion 13 to a thickness of 0.5 to 5.0 μm by evaporating and baking the solvent.
I got Using this thermistor element 1, a temperature sensor 100 was manufactured in the same manner, and the resistance-temperature characteristic was similarly evaluated (see FIG. 5). And the maximum resistance change rate Δ of the thermistor element 1 in the metal cap.
It has been confirmed that R can stably achieve a level of 2%. Therefore, it is possible to provide a thermistor element having the same effect as that of the first embodiment.

Example 3 In Example 3, after obtaining the thermistor portion 13 in the same manner as in Example 1, 3Al ₂ O ₃ .2SiO ₂ (mullite) was used as the surface of the thermistor portion 13 as a reduction resistant composition. It is formed in. In the same manner as in Example 1, the process up to the firing step was performed to obtain a thermistor portion 13 provided with the lead wires 11 and 12. Similarly, the thermistor portion 13 is made of a mixed sintered body 38Y (Cr _0.5 Mn _0.5 ) O ₃ .62Y
₂ O ₃ .

Next, in the dip coating step, an aluminum organometallic compound and a silicon organometallic compound (both alkoxides in this example), which are precursors of the reduction resistant composition mullite, were fixed to the surface of the thermistor portion 13. Aluminum organometallic compound solution (SYM-AL0
4, using a silicon organometallic compound solution (SYM-SI05, manufactured by U.S. Symmetrics, Inc.) and a silicon organometallic compound solution, and baking the aluminum organometallic compound solution and the silicon organometallic compound solution to obtain 3Al ₂ O _3.
The resulting mixture was mixed to obtain 2SiO ₂ to prepare a mixed solution of an aluminum organometallic compound solution and a silicon organometallic compound solution.

The fixation of the reduction-resistant composition to the surface of the thermistor portion 13 was carried out by dip coating by dipping the mixed solution and pulling up the thermistor portion 13 as in Example 1. Thus, a precursor of the reduction resistant composition mullite was formed. Thereafter, in the film forming step, the above-described Example 1 was used.
Similarly to the above, the solvent contained in the mixed solution was vaporized and baked, whereby the reduction-resistant composition was formed on the surface of the thermistor portion 13 as the reduction-resistant coating 14 with a thickness of 0.5 to 5.0 μm. The thermistor element 1 was obtained. A temperature sensor 100 was similarly manufactured using this thermistor element 1, and the resistance-temperature characteristics were similarly evaluated (see FIG. 5).

The temperature sensor 100 according to the third embodiment also exhibits good resistance-temperature characteristics as in the first embodiment, and the maximum resistance change rate ΔR of the thermistor element 1 in the metal cap is 1 It has been confirmed that the level of 0.5% can be stably realized. Therefore, it is possible to provide a thermistor element having the same effect as that of the first embodiment. (Example 4) In Example 4, after obtaining a thermistor portion 13 in the same manner as in Example 1, Y ₃ Al was used as a reduction resistant composition.
₅ O ₁₂ is formed on the surface of the thermistor 13.
In the same manner as in Example 1, the process up to the firing step is performed,
Thus, a thermistor portion 13 to which the reference numeral 12 was added was obtained. The thermistor portion 13 is similarly made of the mixed sintered body 38Y (Cr _0.5 M
n _{0. 5)} is an O ₃ · 62Y ₂ O _3.

Next, in the dip coating step, the surface of the thermistor portion 13 is coated with a reduction resistant composition Y ₃ Al ₅
Yttrium organometallic compound and aluminum organometallic compound which are precursors of O ₁₂ (in this example, both are alkoxides)
Was fixed. Yttrium organometallic compound solution (SY
M-Y01, USA symmetrix Ltd.) and aluminum organometallic compound solution (SYM-AL04, using U.S. symmetrix Inc.), Y ₃ A these yttrium organic compound and an aluminum organometallic compound solution after firing
formulated such that l ₅ O _12, to prepare a mixed solution of yttrium organometallic compound solution and an aluminum organometallic compound solution.

The fixation of the reduction resistant composition on the surface of the thermistor portion 13 was carried out by immersing the composition in the mixed solution in the same manner as in Example 1.
Dip coating was performed by lifting. Thus, a precursor was formed on the surface of the thermistor 13. Thereafter, in the film formation step, the solvent contained in the mixed solution is vaporized and baked in the same manner as in Example 1 so that the surface of the thermistor 13 has a reduction resistant composition of 0.5 to 5.0 μm.
To obtain a thermistor element 1 formed as a reduction-resistant film 14. A temperature sensor 100 was similarly manufactured using this thermistor element 1, and the resistance-temperature characteristics were similarly evaluated (see FIG. 5).

The temperature sensor 100 of the fourth embodiment also exhibits good resistance-temperature characteristics, as in the first embodiment, and the maximum resistance change rate ΔR of the thermistor element 1 in the metal cap is 2 It has been confirmed that a level of 0.0% can be stably realized. Therefore, it is possible to provide a thermistor element having the same effect as that of the first embodiment. (Example 5) In Example 5, after obtaining a thermistor portion 13 in the same manner as in Example 1, Y ₂ Si was used as a reduction resistant composition.
O ₅ is formed on the surface of the thermistor 13. In the same manner as in Example 1, the steps up to the firing step are performed, and
2 was obtained. The thermistor portion 13 is similarly made of the mixed sintered body 38Y (Cr _0.5 Mn _0.5 ).
O ₃ · 62Y ₂ O ₃ .

Next, in the dip coating step, the surface of the thermistor portion 13 is coated with a reduction resistant composition Y ₂ SiO
_An organometallic compound of yttrium and a organometallic compound of silicon (both alkoxides in this example), which are the precursors of ₅ , were fixed. Yttrium organometallic compound solution (SYM-Y
01, manufactured by Symmetrics Inc. of the United States) and a silicon organometallic compound solution (SYM-SI05, manufactured by Symmetrics Inc. of the United States), and after sintering these yttrium organometallic compound solution and silicon organometallic compound solution, Y ₂ SiO ₅
Thus, a mixed solution of the yttrium organometallic compound solution and the silicon organometallic compound solution was prepared.

The fixation of the reduction resistant composition on the surface of the thermistor portion 13 was carried out by immersing the composition in the mixed solution as in Example 1.
Dip coating was performed by lifting. Thus, a precursor was formed on the surface of the thermistor 13. Thereafter, in the film formation step, the solvent contained in the mixed solution is vaporized and baked in the same manner as in Example 1 so that the surface of the thermistor 13 has a reduction resistant composition of 0.5 to 5.0 μm.
To obtain a thermistor element 1 formed as a reduction-resistant film 14. A temperature sensor 100 was similarly manufactured using this thermistor element 1, and the resistance-temperature characteristics were similarly evaluated (see FIG. 5).

The temperature sensor 100 according to the fifth embodiment also exhibits good resistance-temperature characteristics as in the first embodiment, and the maximum resistance change rate ΔR of the thermistor element 1 in the metal cap is 3 It has been confirmed that a level of 0.0% can be stably realized. Therefore, it is possible to provide a thermistor element having the same effect as that of the first embodiment. (Embodiment 6) In this embodiment 6, the mixed sintered body 40Y (Cr
_0.5 Mn _0.5 ) O ₃ .60Y ₂ O ₃ (a = 0.40, b
= 0.60), and a reduction-resistant film 14 made of Y ₂ O ₃ (reduction-resistant composition) is formed on the surface of the thermistor 13.

FIG. 6 shows a manufacturing process of the thermistor element according to the sixth embodiment. In addition, the manufacturing steps of the seventh to tenth embodiments are also shown in FIG. Y ₂ of which purity is 99.9% or more
O ₃ , Cr ₂ O ₃ , Mn ₂ O ₃ and CaCO ₃ were prepared. In formulation 1, composition Y (Cr _0.5 Mn) after calcination
_0.5 ) In order to obtain O ₃ , the molar ratio Y: Cr: Mn
, And Y ₂ O ₃ , Cr ₂ O ₃ and M
n ₂ O ₃ was weighed to a total weight of 2000 g. Furthermore, Ca
36 g of CO ₃ was added, and Y ₂ O ₃ , Cr ₂ O ₃ and Mn ₂ were added.
2036 g of the total of O ₃ and CaCO ₃ was used as a mixed raw material.

Next, in the mixing step, a medium stirring mill was used to atomize the mixed raw material. As the medium stirring mill of the present example, the same one as the pearl mill described in Example 1 is used. The mixing conditions, operating conditions, and the addition amounts of the dispersant and the binder by this pearl mill device are the same as in Example 1. As a result of evaluating the raw material slurry of the mixed and crushed thermistor material with a laser particle size analyzer, the average particle size was 0.3 μm.

Subsequently, the obtained raw material slurry was dried by a spray drier in the same manner as in Example 1 (drying step), and the obtained thermistor raw material powder was put into a 99.3% Al ₂ O ₃ crucible, and heated at a high temperature. Pre-fired for 1 to 2 hours at 1100 to 1300 ° C. in the air in a furnace, and pre-fired Y (Cr _0.5 Mn _0.5 )
O ₃ was obtained (temporary firing step). Next, in Formulation 2, the calcined body which had become a blocky solid by calcining was coarsely pulverized with a raikai machine and passed through a # 30 mesh sieve to obtain Y (Cr _0.5 M
n _0.5 ) O ₃ powder was obtained. Further, Y (Cr _0.5 Mn
_0.5 ) O ₃ powder and Al ₂ O ₃ having a purity of 99.9% or more are prepared, and Y (Cr) having a blending molar ratio (a: b) of both is prepared.
_0.5 Mn _0.5 ) O ₃ : Al ₂ O ₃ was weighed so as to be 40:60 to make the total amount 2000 g.

Subsequently, in a pulverizing step (shown as mixing / pulverizing in the figure), the weighed mixture was mixed and pulverized by a pearl mill device in the same manner as in the mixing step. The pulverization conditions by the pearl mill device are the same as the conditions of the mixing step described in this example. In this pulverization step, a dispersant, a binder, and a release agent were added and pulverized at the same time to obtain a slurry. As a result of evaluating the raw material slurry of the pulverized thermistor material with a laser particle size analyzer, the average powder diameter was 0.3 μm.

Y (Cr _0.5 Mn _0.5 ) O ₃ obtained after pulverization
And Al ₂ O ₃ raw material slurry were pulverized by a spray dryer in the same manner as in the drying step, and Y (Cr _0.5 M
n _0.5 ) Granulated powder in which O ₃ and Al ₂ O ₃ were mixed was obtained (granulation / drying step). A thermistor element was molded using the granulated powder. The molding step was performed by the same mold molding method as described in Example 1. Lead wires 11 and 12 made of Pt100 were loaded into a male mold, and the above-mentioned granulated powder was put into a female mold.
Molding was performed under the same pressure to obtain a molded body of the thermistor portion 13 to which the lead wires 11 and 12 were applied. Then, the formed body of the thermistor portion 13 was subjected to a firing step in the same manner as in Example 1 to obtain the thermistor portion 13 to which the lead wires 11 and 12 were provided.

Subsequently, dip coating was performed in the same manner as in Example 1 above, and the yttrium organometallic compound of the precursor of the reduction-resistant composition Y ₂ O ₃ was fixed on the surface of the thermistor portion 13 and then subjected to a film forming step. , Thermistor unit 13
To obtain a thermistor 1 reduction resistance film 14 is formed consisting of Y ₂ O ₃ with a thickness of 0.5~5.0μm the surface.

Using this thermistor element 1, a temperature sensor 100 was manufactured in the same manner, and the resistance characteristics (resistance value, β, ΔR) were evaluated in the same manner as in the first embodiment. Fig. 7 shows the evaluation results.
Shown in Also in the temperature sensor 100 of the sixth embodiment, similar to the first embodiment, good resistance-temperature characteristics are exhibited.
Further, it has been confirmed that the maximum resistance change rate ΔR of the thermistor element 1 in the metal cap can be stably realized at a level of 3%. Therefore, it is necessary to provide a thermistor element having the same effect as that of the first embodiment. Can be. (Example 7) In Example 7, after obtaining a thermistor portion 13 in the same manner as in Example 6, Al ₂ O was used as a reduction resistant composition.
₃ is formed on the surface of the thermistor 13. In the same manner as in the sixth embodiment, the processes up to the sintering process are performed, and the lead wires 11 and 12
Is obtained. Thermistor part 1
3 is a mixed sintered body 40Y (Cr _0.5 Mn _0.5 ) O
A ₃ · 60Y ₂ O _3.

Next, the formation of the reduction resistant coating 14 made of the reduction resistant composition Al ₂ O _{3 on} the thermistor portion 13 was carried out in the same manner as in Example 2 described above. And the thermistor unit 13
A thermistor element 1 having a reduction-resistant composition formed on the surface thereof as a reduction-resistant coating 14 with a thickness of 0.5 to 5.0 μm was obtained. Using this thermistor element 1, the temperature sensor 1
00, and the resistance-temperature characteristics were similarly evaluated (FIG. 7).
reference).

In the temperature sensor 100 of the seventh embodiment, as in the first embodiment, good resistance-temperature characteristics are exhibited, and the maximum resistance change rate ΔR of the thermistor element 1 in the metal cap is 2 It has been confirmed that a level of 0.0% can be stably realized. Therefore, it is possible to provide a thermistor element having the same effect as that of the first embodiment. (Example 8) In Example 8, after obtaining the thermistor portion 13 in the same manner as in Example 6, 3Al ₂ was used as the reduction resistant composition.
O ₃ · 2SiO ₂ (mullite) is formed on the surface of the thermistor portion 13. In the same manner as in Example 6, the process up to the firing step was performed to obtain a thermistor portion 13 provided with the lead wires 11 and 12. The thermistor portion 13 is similarly made of the mixed sintered body 4.
0Y (Cr _0.5 Mn _0.5 ) O ₃ · 60Y ₂ O ₃ .

Next, the reduction-resistant composition 3Al ₂ O ₃ .2S
The formation of the reduction resistant film 14 made of iO ₂ (mullite) on the thermistor portion 13 was performed in the same manner as in Example 3 described above. Then, a thermistor element in which the reduction resistant composition was formed as the reduction resistant coating 14 on the surface of the thermistor portion 13 to a thickness of 0.5 to 5.0 μm was obtained. This thermistor element 1
, A temperature sensor 100 was fabricated in the same manner, and the resistance-temperature characteristics were similarly evaluated (see FIG. 7).

The temperature sensor 100 according to the eighth embodiment also exhibits good resistance-temperature characteristics as in the first embodiment, and the maximum resistance change rate ΔR of the thermistor element 1 in the metal cap is 1 It has been confirmed that the level of 0.5% can be stably realized. Therefore, it is possible to provide a thermistor element having the same effect as that of the first embodiment. (Example 9) In Example 9, after obtaining the thermistor 13 in the same manner as in Example 6, Y ₃ Al was used as the reduction resistant composition.
₅ O ₁₂ is formed on the surface of the thermistor 13.
In the same manner as in Example 6, the process up to the firing step is performed,
Thus, a thermistor portion 13 to which the reference numeral 12 was added was obtained. Similarly, the thermistor part 13 is a mixed sintered body 40Y (Cr _0.5 Mn _0.5 ).
O ₃ · 60Y ₂ O ₃ .

Next, the formation of the reduction resistant coating 14 made of the reduction resistant composition Y ₃ Al ₅ O _{12 on} the thermistor portion 13 is as follows.
It carried out similarly to the said Example 4. Then, the thermistor element 1 in which the reduction resistant composition is formed on the surface of the thermistor portion 13 as the reduction resistant coating 14 with a thickness of 0.5 to 5.0 μm.
I got A temperature sensor 100 was similarly manufactured using this thermistor element 1, and the resistance-temperature characteristics were similarly evaluated (see FIG. 7).

The temperature sensor 100 of the ninth embodiment also exhibits good resistance-temperature characteristics, as in the first embodiment, and the maximum resistance change rate ΔR of the thermistor element 1 in the metal cap is 2 It has been confirmed that a level of 0.0% can be stably realized. Therefore, it is possible to provide a thermistor element having the same effect as that of the first embodiment. (Example 10) In Example 10, after obtaining a thermistor 13 in the same manner as in Example 6, Y ₂ was used as a reduction resistant composition.
SiO ₅ is formed on the thermistor portion 13 surface. In the same manner as in Example 6, the process up to the firing step
A thermistor part 13 to which Nos. 1 and 12 were applied was obtained. The thermistor portion 13 is similarly made of the mixed sintered body 40Y (Cr _0.5 Mn).
_0.5) a O ₃ · 60Y ₂ O _3.

Next, the formation of the reduction-resistant film 14 made of the reduction-resistant composition Y ₂ SiO _{5 on} the thermistor portion 13 was carried out in the same manner as in Example 5 described above. And thermistor part 1
The thermistor element 1 in which the reduction-resistant composition was formed as a reduction-resistant coating 14 on the three surfaces with a thickness of 0.5 to 5.0 μm was obtained. A temperature sensor 100 was similarly manufactured using this thermistor element 1, and the resistance-temperature characteristics were similarly evaluated (see FIG. 7).

In the temperature sensor 100 of the tenth embodiment, as in the first embodiment, good resistance-temperature characteristics are exhibited, and the maximum resistance change rate ΔR of the thermistor element 1 in the metal cap is 3 It has been confirmed that a level of 0.0% can be stably realized. Therefore, it is possible to provide a thermistor element having the same effect as that of the first embodiment.

(Comparative Example 1) In Comparative Example 1, as in Example 1, mixed sintered body 38Y (Cr ₂ O ₃ , Cr ₂ O ₃ , Mn ₂ O _3, and CaCO ₃ was used as a raw material. _0.5 Mn
After obtaining the thermistor 13 consisting of _{0.5) O 3 · 62Y 2 O} 3, is obtained by the thermistor element without forming a reduction-resistant composition on the surface thereof. In other words, the thermistor element 1 shown in FIG.

The thermistor element of Comparative Example 1 was incorporated in a temperature sensor in the same manner as the configuration of the temperature sensor 100 shown in FIG. 2, and the resistance characteristics of this temperature sensor were evaluated in the same manner as in Example 1. FIG. 8 shows the evaluation results. In the temperature sensor of this example, the resistance value is 50 in a temperature range from room temperature to 1000 ° C.
In the range of Ω to 100 kΩ and good resistance temperature characteristics, but the maximum resistance change rate ΔR in the metal cap
Is about 30% level, and the resistance value stability is inferior when the thermistor element itself is exposed to a reducing atmosphere as compared with the above embodiment.

Note that the temperature sensor of this example is 900 ° C. × 1
When subjected to thermal aging of 00Hr, the resistance change rate Δ
R dropped to the 5% level and stabilized. Therefore, in order to stabilize the resistance of the thermistor element of this example, 900 ° C. × 10
Thermal aging of 0 Hr is required. Comparative Example 2 In Comparative Example 2, mixed sintering was performed using Y ₂ O ₃ , Cr ₂ O ₃ , Mn ₂ O ₃ , CaCO _3, and Al ₂ O ₃ as raw materials in the same manner as in Example 6. Body 40Y (Cr
After obtaining the thermistor portion 13 composed of _0.5 Mn _0.5 ) O ₃ .60Al ₂ O ₃ , a thermistor element was obtained without forming a reduction resistant composition on the surface. That is, like the comparative example 1, the thermistor element 1 shown in FIG.

The thermistor element of Comparative Example 1 was incorporated in a temperature sensor in the same manner as in Comparative Example 1, and the resistance-temperature characteristics were evaluated (FIG. 8). Although the temperature sensor of this example also has good resistance-temperature characteristics, the maximum resistance change rate ΔR in the metal cap is at the 25% level.
Resistance stability is poor when the thermistor element itself is exposed to a reducing atmosphere.

In the temperature sensor of this embodiment, 90
When subjected to thermal aging at 0 ° C. × 100 hours, the rate of change in resistance ΔR was reduced to the 4% level and stabilized. Therefore,
In order to stabilize the resistance of the thermistor element of this example, 900
Thermal aging at 100 ° C. × 100 hours is required. (Other Modifications) By the way, except for the above-mentioned first to tenth embodiments, C
high temperature thermistor element mainly composed of r ₂ O ₃ , (Al,
Forming the reduction-resistant composition of the present invention on the surface of a conventional thermistor element such as a thermistor element having a Cr, Fe) ₂ O ₃ -based corundum type composition and a thermistor element having a single composition of Y (Cr, Ti, Fe) O ₃ perovskite. By doing so, it is possible to provide a thermistor element that has stable characteristics without resistance change even in a reducing atmosphere in a metal cap and that does not require thermal aging by a temperature sensor.

In each of the above examples, the reduction resistant composition was Y ₂ O ₃ , Al ₂ O ₃ , SiO ₂ , Y ₃ Al ₅
O ₁₂ (YAG), 3Al ₂ O ₃ .2SiO ₂ (mullite) and Y ₂ SiO ₅ have been described, but when a mixture comprising all or a part of these reduction resistant compositions is used as the reduction resistant composition, However, it goes without saying that a thermistor element having stable characteristics without a change in resistance can be provided as described above.

Further, as a reduction resistant composition, Y ₂ O
₃ , Al ₂ O ₃ , SiO ₂ , Y ₃ Al ₅ O ₁₂ (YA
G) 3Al ₂ O ₃ .2SiO ₂ (Mullite), Y ₂ S
The same effect as described above can also be obtained by forming a reduction-resistant coating composed of a plurality of layers of the reduction-resistant composition on the surface of the thermistor element by arbitrarily combining iO ₅ . In each of the above embodiments, the shape φ1.6 mm × 1.2 mm
The effect is obtained by forming a reduction-resistant composition on the surface of the small bulk type thermistor portion 13, but this does not depend on the shape of the thermistor portion 13.

For example, a binder, a resin material and the like are mixed and added to the thermistor element raw material to adjust the viscosity and hardness suitable for sheet forming, and a sheet-shaped thermistor sheet having a thickness of 200 μm is obtained. 5 thermistor sheets
In a thermistor element having a thermistor part of a sheet lamination type having a thickness of 1 mm and a lead wire provided by laminating the sheets, the same effect as in the above embodiment can be obtained by forming a reduction resistant film on the surface. it can.

Further, a binder is added to the thermistor element raw material,
Mixing and adding a resin material and the like, adjusting the viscosity and hardness suitable for extrusion molding, obtaining a molded body of a thermistor element having a hole for providing a lead wire by extrusion molding, and forming a lead wire. By loading and firing, the same effect as in the above embodiment can be obtained even in a thermistor element in which a lead wire is formed.

In Examples 1 to 10, alcoholate (metal alkoxide) which is an organometallic compound composed of a single metal element was used as a precursor of the reduction resistant composition.
l, an alcoholate solution that is an organometallic compound containing at least one element selected from Si, such as a solution of an yttrium-aluminum organometallic compound or a solution of an yttrium-silicon organometallic compound, is fixed to a precursor of a reduction-resistant composition. Can be used.

Further, an organometallic compound was used as a precursor of the reduction-resistant composition, but a compound containing at least one element selected from Y, Al, and Si, such as nitrate, chloride, acetate, and oxalate An acid salt or the like is used as a precursor, and these solutions can be used for fixing the precursor of the reduction resistant composition. Further, in Examples 1 to 10 described above, dip coating, which is a representative of a wet manufacturing process, was described as a method for forming a reduction-resistant composition. However, a thermistor element in which the reduction-resistant composition was formed on the thermistor portion surface was used. In order to obtain, the method of forming the reduction resistant composition is not limited.

Examples of the wet production process include forming a reduction-resistant composition or forming a precursor of the reduction-resistant composition by spraying, spraying, coating, printing, plating, electrophoresis, or the like. A thermistor element can be obtained by forming a reduction resistant composition by firing or the like.
Examples of the dry manufacturing process include a PVD method (physical vapor deposition method) such as electron beam vapor deposition and sputtering;
A thermistor is formed by forming a reduction-resistant composition by a VD method (chemical nutrition method) or the like, or by forming a precursor of the reduction-resistant composition and forming the reduction-resistant composition by firing or the like. An element can be obtained.

The thickness of the reduction resistant composition can be arbitrarily set depending on the operating conditions of each production process. Further, in the above Examples 1 to 10, the reduction resistant composition was formed on the surface of the thermistor part after the firing step, but the molded body of the thermistor part after the die molding (forming step) in the manufacturing step shown in FIG. To
A thermistor element having a reduction-resistant composition formed on its surface can be obtained by applying a precursor of the reduction-resistant composition and firing it at the same time.

Further, after the molding in the manufacturing process shown in FIG. 1, the molded body of the thermistor portion was calcined at 1200 to 1400 ° C. to obtain a calcined body of the thermistor portion. By applying and baking the precursor of the reduction-resistant composition, a thermistor element having the reducing composition formed on the surface thereof can also be obtained. Further, in order to increase the adhesion strength of the reduction-resistant composition to the thermistor element, a primary layer (primer layer) is formed on the thermistor portion surface by a wet manufacturing process method or a dry manufacturing process method. The same effect as described above can be obtained in a thermistor element in which the reduction-resistant composition as the secondary layer is formed on the entire surface of the primary layer by the method of the wet manufacturing process or the method of the dry manufacturing process.

For the first layer, the reduction resistant composition Y ₂
O ₃ , Al ₂ O ₃ , SiO ₂ , Y ₃ Al ₅ O ₁₂ (YA
G) 3Al ₂ O ₃ .2SiO ₂ (Mullite), Y ₂ S
The composition ratio of such iO _5, the concentration of the precursor solution, optionally selected by the operation conditions of the wettability or the manufacturing process of the thermistor portion can be controlled. Furthermore, thermal expansion coefficient, thermal conductivity,
In order to add / provide the heat resistance function, it is possible to add another material to the above-mentioned first layer and the second layer, or to form a composite with the added material. Has the same effect as described above.

The temperature sensor 100 shown in FIG. 1 using the thermistor element of each of the above examples may have a sensor configuration without the metal cap 2. As described above, the thermistor element of the present invention focuses on suppressing the movement of oxygen atoms from the thermistor section to the outside of the element in a thermistor element in a reducing atmosphere, and has a reduction resistant composition on the surface of the thermistor section. The device configuration is such that an object is formed, thereby suppressing reduction of the thermistor device itself and realizing resistance value stability.

Therefore, in the thermistor element of the present invention, it is not necessary to perform thermal aging for stabilizing the element resistance or use an expensive special metal material cap, and the resistance change rate ΔR is small and stable. A temperature sensor having improved characteristics can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic sectional configuration diagram of a thermistor element according to an embodiment of the present invention.

FIG. 2 is a sectional configuration diagram of a temperature sensor using the thermistor element of FIG. 2;

FIG. 3 is a sectional view taken along line AA of FIG. 2;

FIG. 4 is a manufacturing process diagram of the thermistor elements of Examples 1 to 5 of the present invention.

FIG. 5 is a table showing resistance characteristics of the thermistor elements of Examples 1 to 5;

FIG. 6 is a manufacturing process diagram of the thermistor elements of Examples 6 to 10 of the present invention.

FIG. 7 is a table showing resistance characteristics of the thermistor elements of Examples 6 to 10;

FIG. 8 is a table showing resistance characteristics of the thermistor elements of Comparative Examples 1 and 2.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Thermistor element, 11, 12 ... Lead wire, 13 ... Thermistor part, 14 ... Reduction resistant coating.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Kaoru Kuzuoka 1-1-1 Showa-cho, Kariya-shi, Aichi Prefecture Inside DENSO Corporation

Claims (10)

[Claims] 1. A thermistor part (13) made of a thermistor material, and a reduction-resistant coating (14) made of a reduction-resistant composition formed on the surface of the thermistor part (13). Thermistor element. 2. The reduction-resistant composition is formed by fixing an organometallic compound as a precursor to the surface of the thermistor section (13) and then firing the same. Item 2. Thermistor element according to item 1. 3. The method according to claim 2, wherein the reduction-resistant composition is Y, Al, Si.
The thermistor element according to claim 1, comprising at least one element selected from the group consisting of: 4. The reduction-resistant composition according to claim ₂ , wherein the composition is Y ₂ O ₃ , Al
₂ O ₃ , SiO ₂ , Y ₃ Al ₅ O ₁₂ , ₃ Al ₂ O ₃ .2
4. The thermistor element according to claim 3, which is at least one composition selected from SiO ₂ (mullite) and Y ₂ SiO ₅ . 5. The thermistor element according to claim 1, wherein the thermistor element is used at a temperature of 900 ° C. or higher. 6. A method for manufacturing a thermistor element comprising a reduction-resistant coating (14) made of a reduction-resistant composition formed on the surface of a thermistor portion (13) made of a thermistor material, The precursor of the conductive composition is added to the thermistor part (1).
3) is formed on the surface and fired to form the reduction resistant coating (14) on the thermistor portion (13) surface.
Forming a thermistor element. 7. The method according to claim 6, wherein an organometallic compound is used as a precursor of the reduction resistant composition. 8. The organic metal compound includes Y, Al,
The method for manufacturing a thermistor element according to claim 7, wherein a metal alkoxide containing at least one element selected from Si is used. 9. A dip coating is performed on the surface of the thermistor portion (13) using a solution containing the organometallic compound, whereby the precursor of the reduction-resistant composition is fixed to the surface of the thermistor portion (13). 9. The method for manufacturing a thermistor element according to claim 7, wherein: 10. A thermistor element (1) having a thermistor part (13) made of a thermistor material and a reduction-resistant coating (14) made of a reduction-resistant composition formed on the surface of the thermistor part (13). A temperature sensor comprising: a pair of electric wiring members (11, 12) provided through the reduction resistant coating (14) and electrically connected to the thermistor portion (13); A temperature sensor characterized in that the composition has higher electrical resistance than the thermistor material and electrical insulation.