JPH0616471A - Heat resistant conductive sintered body - Google Patents

Abstract

(57) [Summary] [Purpose] Compared with known materials, it has excellent sinterability and conductivity, and has excellent mechanical properties and thermal stability even at high temperatures.
The main purpose is to provide a dense conductive material having excellent durability even in the presence of water vapor at a high temperature. [Structure] (1) R _1-x A _x Cr _{1- y My} O ₃ (wherein R is at least one lanthanide element; A
Is at least one of Ca and Sr; M is Co, M
At least one of n and Ni; 0.05 ≦ x ≦ 0.50; 0 <
a sintered body having a perovskite structure having a composition of y ≦ 0.30), and (2) the bulk density of the sintered body is 6.0 g / cm.
³ or more, (3) the electrical conductivity at 1000 ° C. in the atmosphere is 5 S / cm or more, (4) the average crystal grain size of the sintered body is 5 to 80 μm, and (5) 100 including 5% of water vapor.
A heat-resistant conductive sintered body, which is stable in shape and conductivity even after kept in an atmosphere of 0 ° C. for 100 hours.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat resistant conductive sintered body useful as a material for heating elements, electrodes, fuel cells and the like.

[0002]

2. Description of the Related Art R (Ca, Sr) CrO ₃ in which a part of R of a sintered body represented by the formula: RCrO ₃ (R is a lanthanide; the same applies hereinafter) is solid-solution-substituted with Ca or Sr, particularly La ( C
a, Sr) CrO ₃ is known as a high melting point heat-resistant conductive oxide having a perovskite type crystal structure. However, since this material is a difficult-to-sinter material, it is difficult to obtain a dense sintered body. Also, the formula: R (Ca,
The sintered body represented by Sr) MO ₃ (M is at least one of Co, Mn, and Ni; the same applies hereinafter) also has a perovskite-type crystal structure, and R (Ca, Sr) Cr.
It is known as an oxide that has higher conductivity than O ₃ and is easily sintered. However, these materials have a drawback that they are inferior in stability because they cause phenomena such as dissociation, evaporation, and significant decrease in conductivity in a particular atmosphere, particularly in a high temperature or low oxygen atmosphere, and the conditions under which they can be used Is extremely limited. Therefore, R _1-x A _x Cr _{1-y in} which a part of Cr of R (Ca, Sr) CrO ₃ is replaced with M to form a solid solution
M _y O ₃ has been proposed as a material that combines the advantages of both. However, even if a dense and highly conductive sintered body is obtained, this material has the drawback of being inferior in mechanical properties when stressed at high temperature, and lacking in thermal stability over time. In particular, in an atmosphere with a partial pressure of water vapor, it is difficult to say that it is a practical material because the electrical conductivity and mechanical properties are significantly reduced.

[0003]

DISCLOSURE OF THE INVENTION The present invention is superior to known materials in sinterability and conductivity, mechanical properties and thermal stability even at high temperatures, and is superior to steam vapor at high temperatures. The main purpose of the present invention is to provide a dense conductive material that is excellent in durability even in the presence.

[0004]

The present inventor has conducted research while paying attention to the problems of the prior art as described above, and as a result, the R (Ca, Sr) Cr (M) O ₃ sintered body at a high temperature was obtained. It was found that it is necessary to control the average crystal grain size of the sintered body within a specific range in order to improve the mechanical properties of the sintered body, in addition to simply increasing its density. Further, deterioration of thermal stability of the sintered body with time, particularly the cause of deterioration of electrical conductivity and mechanical properties in the presence of water vapor is mainly controlled by the density and average crystal grain size within a specific range. In addition to that, it was also found that it was due to the non-uniform distribution of elements in minute portions such as crystal grain boundaries and pore surfaces of the sintered body.

The present invention has been completed based on the above new findings. That is, the present invention is to provide a heat-conductive sintered body following: _{"(1) R 1-x A} x Cr 1-y M y O 3 ( wherein, R is at least one lanthanide element ; A
Is at least one of Ca and Sr; M is Co, M
At least one of n and Ni; 0.05 ≦ x ≦ 0.50; 0 <
y ≦ 0.30) (2) The bulk density of the sintered body is 6.0 g / cm ³ or more, and (3) the electrical conductivity at 1000 ° C. in the atmosphere is 5 S / c.
m or more, and (4) the average crystal grain size of the sintered body is 5 to 80.
(5) A heat-resistant conductive sintered body characterized by being stable in shape and conductivity even after being held in an atmosphere of (5) 5% steam at 1000 ° C. for 100 hours.

The heat resistant conductive sintered body according to the present invention is characterized by the following properties (1) to (5).

(1) R _1-x A _x Cr _{1- y My} O ₃ (wherein R is at least one lanthanide element; A
Is at least one of Ca and Sr; M is Co, M
At least one of n and Ni; 0.05 ≦ x ≦ 0.50; 0 <
y ≦ 0.30). The lanthanide element means 15 elements ranging from lanthanum having an atomic number of 57 to lutetium having an atomic number of 71. The lanthanide elements may be used alone or in combination of two or more. As the lanthanide element, La, Nd and Pr are more preferable, and especially La alone or a mixture of La and another lanthanide element is further preferable. L as the lanthanide element
When a, Nd or Pr is used, the conductivity of the sintered body is improved and the heat resistance is also improved. On the other hand,
When these elements are used, it is necessary to perform firing at a high temperature in order to obtain a high-density sintered body. Therefore, when lowering the firing temperature, some of them (10 ~ 30
It is preferable to replace (about mol%) with another lanthanide element. In the heat resistant conductive sintered body of the present invention, in the perovskite type oxide having RCrO3 as a basic composition, R
A portion (0.05 to 0.50 mol) of Ca and Sr (both of which may be collectively referred to simply as A) by substitution and solid solution, and a portion of Cr by substitution by at least one of M and solid solution. It is essential to melt.

When substituting trivalent R with divalent A,
The lack of charge of the cation caused by this is compensated by changing a part of trivalent Cr to tetravalent Cr.
As a result, the trivalent and tetravalent hopping conductions of Cr contribute to greatly improve the conductivity. The substitution amount of R by A is 5
If it is less than mol%, the conductivity is not sufficiently improved, the sinterability is also lowered, and the bulk density of the sintered body tends to be lowered. On the other hand, when the substitution amount of R by A exceeds 50 mol%, not only further improvement in conductivity is not observed, but also the thermal stability of the sintered body decreases. The substitution amount of R by A is more preferably 10 to 40 mol%. Regarding M, the conductivity and sinterability are generally improved in proportion to the substitution amount, but on the other hand, when the substitution amount is excessive, the stability, heat resistance, corrosion resistance, etc. of the sintered body are improved. Tends to lower. For example, Co improves sinterability, increases the coefficient of thermal expansion and conductivity, but reduces conductivity in a reducing atmosphere. Mn improves sinterability, but decreases stability, durability, conductivity, etc. in a reducing atmosphere. Ni improves sinterability and conductivity, but reduces conductivity in a reducing atmosphere. Therefore, the total amount of M should be 30 mol% or less in the sintered body represented by the above formula (1), more preferably about 1 to 20 mol%, and most preferably about 2 to 10 mol%. And It is preferable that M is appropriately selected depending on the intended use of the material in consideration of the properties of each element described above, or that two or more kinds are used in combination.

(2) In the present invention, the bulk density of the sintered body is 6.0 g / cm ³ or more. Bulk density is 6.0g
When it is less than / cm ³ , the number of pores existing in the crystal grains of the sintered body and in the grain boundaries is large, which leads to a decrease in conductivity due to a decrease in the conductive area, a decrease in airtightness, and a decrease in thermal stability. And with deterioration of mechanical properties. The bulk density is more preferably 6.1 g / cm ³ or more,
To maintain the airtightness against H ₂ gas, 6.2
It is more preferably g / cm ³ or more. The bending strength of the sintered body at room temperature is preferably 8 kgf / mm ² or more.

(3) In the sintered body of the present invention, 1
It is necessary that the electric conductivity at 000 ° C. is 5 S / cm or more. If the electrical conductivity under the above conditions is less than 5 S / cm, the electrical conductivity of the sintered body of the present invention as a heating element, an electrode, a separator of a fuel cell, etc., which is a field of application, becomes insufficient, which is not suitable. . The electric conductivity at 1000 ° C. in the atmosphere is more preferably 10 S / cm or more, and 20
It is more preferably S / cm or more. From the viewpoint of improving conductivity and durability, the content of each of the alkali metal oxide and SiO ₂ is preferably 0.2% or less.

(4) The average crystal grain size in the sintered body of the present invention is 5 to 80 μm. The average crystal grain size of the sintered body is 5μ
If it is less than m, mechanical properties when stressed at high temperature, particularly strength and creep resistance are deteriorated and durability when used at high temperature becomes insufficient, and steam exists at high temperature. Stability and durability deteriorate when used in an atmosphere. Furthermore, when the sintered body of the present invention is used as a separator for a solid oxide fuel cell, a reaction with a lanthanum manganate-based oxide, nickel cermet or the like that comes into contact with the sintered body is likely to occur. On the other hand, when the average crystal grain size of the sintered body is more than 80 μm, the creep resistance is good but the mechanical strength and the like are deteriorated, which is not preferable. Further, when the crystal grain size is large, voids are generated in the grain boundaries during the crystal grain growth process, which deteriorates durability in an atmosphere having a water vapor partial pressure, which is not preferable. The average crystal grain size in the sintered body of the present invention is more preferably about 10 to 70 μm.

(5) It is stable in shape and conductivity even after being kept for 100 hours in an atmosphere of 1000 ° C. containing 5% of water vapor. Here, "excellent stability"
Means that the sintered body according to the present invention contains 1000% of water vapor.
After holding for 100 hours in the atmosphere of ℃, 80 ~ 100 ℃
It means that dimensional change and reduction in conductivity are not substantially observed even after being left for 10 days in an atmosphere having a relative humidity of 80% or more. Such stability is judged from the fact that there is no sharp endothermic reaction in the differential thermal analysis at 200 to 1000 ° C. when the sintered body is powdered. When the sintered body represented by the formula (1) is used as a heating element, an electrode, a fuel cell separator or the like, long-term durability is required. "10 in an atmosphere of 1000 ° C containing 5% of water vapor
When it satisfies the condition that "it is stable in shape and conductivity after being held for 0 hours", it can be used for such an application. In addition to the above requirements (2) and (4), such stability can be achieved by the distribution of the elements particularly in a minute portion of the sintered body, particularly in a minute portion such as a crystal grain boundary or a pore surface of the sintered body. It is achieved by the non-uniformity of. In addition, alkali metal oxides and SiO ₂
It is also convenient to improve the stability that the content of each is 0.2% or less.

The sintered body according to the present invention is usually manufactured as follows. First, the raw materials to be the R source, A source, Cr source and M source are blended so that the ratio of each component at the time of producing a sintered body is within a predetermined range, and mixed and pulverized to obtain a uniform powder mixture. . As the raw materials for the R source, A source, Cr source and M source, compounds in the form of compounds such as oxides, hydroxides, nitrates, carbonates, sulfates, chlorides and oxalates are used. The particle size of the powder is not particularly limited, but is 5
It is preferably about μm or less. Generally, during the synthesis process, since Cr easily diffuses into the container,
It is preferable to mix a slightly larger amount of r source. This point may be appropriately determined in consideration of the sintering temperature and time, but, for example, it is more preferable to use Cr than the final composition of the sintered body.
It is preferable to add a large amount of the source and the M source in an amount of about 0.2% by weight (as Cr ₂ O ₃ and M ₂ O ₃ , respectively). The mixing may be performed by either wet mixing or dry mixing of powders, or may be performed by mixing aqueous solutions of respective raw materials.

Next, the powder mixture obtained as described above contains R (Ca, Sr) C as the main component (preferably 70% or more).
Heat treatment is performed at a temperature equal to or higher than the temperature at which the perovskite structure of r (M) O _{3 is formed} , to obtain a synthetic powder. The heat treatment temperature may vary depending on the type, particle size, mixing method, etc. of each raw material compound constituting the powder mixture, but is usually in the range of 700 to 1400 ° C, and more preferably in the range of 900 to 1300 ° C. . If the heat treatment temperature is too low, the shrinkage at the time of sintering described later becomes large and firing distortion occurs,
Not preferable. On the other hand, if the heat treatment temperature is too high,
Since the crystal grain size of the synthetic powder becomes too large, the sinterability and the uniformity of minute portions of the composition are deteriorated, which is also not preferable. The heat treatment time is also related to the heat treatment temperature,
It is usually about 0.5 to 3 hours.

Next, the synthetic powder obtained above is dispersed or finely pulverized. This dispersion or fine pulverization is preferably carried out in the presence of an organic solvent such as water or alcohol.
The dispersion or fine pulverization is performed until the obtained powder has an average particle size of 2 μm or less and a specific surface area of 2 m ² / g or more, more preferably an average particle size of 1 μm or less and a specific surface area of 4 m ² / g or more. It is preferable to carry out. This dispersion or fine pulverization prevents segregation of the composition in the sintered body.

Then, the powder dispersed or crushed to a predetermined grain size is molded into a predetermined shape by a conventional method for molding ceramics, that is, by CIP, mechanical press, casting, injection, extrusion, tape molding or the like. . At this time, it goes without saying that an additive such as a known molding aid such as an acrylic type may be used in combination. Then, the obtained molded body is fired. The atmosphere during firing may be any of reduced pressure, normal pressure and increased pressure. The firing temperature is usually 13
It is in the range of about 00 to 1900 ° C, and 1400 to 17
It is more preferable that the temperature is about 50 ° C. When pressure sintering is performed, the sintered body can be densified at a lower temperature. When the amounts of A component and M component are small, it is necessary to raise the firing temperature. The conductivity of the sintered body fired under the low oxygen partial pressure condition is lowered. Therefore, in this case, it is preferable that the oxide sintered body be heat-treated in the atmosphere at a temperature of 1000 ° C. or higher to improve its conductivity. This heat treatment does not necessarily have to be performed subsequent to the sintering treatment, and may be performed in the process of using the sintered body as long as the above conditions are satisfied.

[0017]

According to the present invention, the following remarkable effects are achieved. (1) The heat resistance, conductivity, and density of the R (Ca, Sr) Cr (M) O ₃ sintered body can be increased to a level that cannot be achieved by conventional techniques. (2) R (Ca, Sr), which has excellent thermal stability and long-term durability in a high temperature atmosphere where water vapor is present.
A Cr (M) O ₃ sintered body is obtained. (3) Since the sintered body according to the present invention has excellent mechanical properties even at high temperatures, when used as, for example, a heating element, a separator or interconnector of a solid oxide fuel cell, it is less likely to be deformed or destroyed. , Increase the reliability of these. (4) Since it can maintain airtightness and maintain high conductivity for a long period of time even in an oxidizing or reducing atmosphere in which water vapor is present, it is used as a practical material for heating elements, separators of solid oxide fuel cells and interconnectors. It is useful.

[0018]

EXAMPLES Examples and comparative examples will be shown below to further clarify the features of the present invention.

Example 1 Raw material powders of La ₂ O ₃ , Cr ₂ O ₃ , SrCO ₃ and NiO were blended so as to have a composition of La _0.8 Sr _0.2 Cr _0.95 Ni _0.05 O ₃ and wet in the presence of water. After being mixed and dispersed in, the mixture was dried and heat-treated at 1200 ° C. for 2 hours to obtain a powder in which 95% or more was synthesized in a perovskite structure. The obtained synthetic powder was wet pulverized for 12 hours in the presence of alcohol using a medium made of alumina by a medium stirring mill to obtain a powder having an average particle size of 0.7 μm. Next, an acrylic molding aid was added to this, and a granular powder (average particle size 60 μm) for molding was prepared with a spray dryer. CIP this granular powder at a molding pressure of ² ton / cm ² .
After molding to obtain a molded body of 50 mm × 50 mm × 5 mm, it was fired in air at 1700 ° C. for 3 hours. The sintered body obtained by grinding with a diamond grindstone to finish the surface had the following characteristics. Bulk density = 6.4 g / cm ³ Average crystal grain size = 15 μm Conductivity = 42 s / cm (1000 ° C., in air) Conductivity = 5 s / cm (1000 ° C., in H ₂ ) JIS 3-point bending strength = 11 kgf / mm ² (room temperature) JIS three-point bending strength = 9 kgf / mm ² (1000 ° C.) Further, the above sintered body was held in an atmosphere of 1000 ° C. containing 5% of steam for 100 hours to obtain a relative humidity of 90% and a temperature of 8
After leaving it for 10 days under the condition of 5 ° C., it was allowed to cool, and the dimensional change at room temperature and the conductivity at 1000 ° C. were measured. As a result, both values were the same as those before the heat treatment. Further, when the sintered body was subjected to a chemical analysis, it was found that 0.13% of Al ₂ O ₃ mixed from the alumina medium for grinding was contained.
SiO ₂ and Na ₂ O were each 0.1% or less.

[0020] Example _{2 La 1-x A x Cr} 1-y M y O 3 type A and M of the sintered body having a composition represented by, as shown values and firing temperature of the x and y in Table 1 A sintered body was produced in the same manner as in Example 1 except that various changes were made. The composition of each of the used samples 2-a to 2-d is as follows. 2-a ... La _0.8 Sr _0.2 Cr _0.9 Ni _0.1 O ₃ 2-b ... La _0.8 Sr _0.2 Cr _0.8 Ni _0.2 O ₃ 2-c ... La _0.8 Sr _0.2 Cr _0.7 Ni _0.3 O ₃ 2-d ... La _0.95 Ca _0.05 Cr _0.6 Ni _0.4 O ₃ The characteristics of the obtained sintered body are also shown in Table 1. Table 1 Sample Calcination temperature Bulk density (g / cm ³ ) Particle size Conductivity (μm) (1000 ℃ S / cm) 2-a 1650 ℃ 6.1 10 43 2-b 1700 ℃ 6.4 20 50 2-c 1650 ℃ 6.4 25 65 2-d 1750 ℃ 6.0 60 7 As is clear from the results shown in Table 1, the sintered body according to the present invention has high density, excellent mechanical properties, and high conductivity. Next, the above-mentioned sintered body is mixed with 5% of water vapor at 10%.
Hold for 100 hours in an atmosphere of 00 ° C, relative humidity 90
%, A temperature of 85 ° C. was left for 10 days and then allowed to cool, and the dimensional change at room temperature and the conductivity at 1000 ° C. were measured. With the sintered bodies of the present invention (2-a to 2-c), the values were the same as those before the heat treatment. On the other hand, comparative sintered body 2-d
Had collapsed after the same treatment, and the conductivity could not be measured.

Example 3 La ₂ O ₃ , Cr ₂ O ₃ , SrCO ₃ , CoO and N
Each raw material powder of iO was added to La _1-x Sr _x Cr _0.9 Co _0.05.
Ni _0.05 O ₃ composition was added (however, the value of x and the firing conditions are as shown in Table 2), and otherwise, Example 1
A sintered body was manufactured in the same manner as in. Table 3 shows the characteristics of the sintered body. Table 2 Test Material x Burning Conditions Temperature Pressure 3-a 0.03 1700 ℃ 3- c 0.30 1600 ℃ in air during 3-b 0.10 1650 ℃ in air atmosphere 3-d 0.40 1600 ℃ in air 3-e 0.55 1600 ° C in air Table 3 Sample bulk density (g / cm ³ ) Grain size Conductivity (Μm) (1000 ° C. S / cm) 3-a 5.8 4 26 3-b 6.3 25 30 3-c 6.4 18 50 3-d 6.3 20 65 3-e 6.0 15 15 35 As is clear from the results shown in Tables 2 and 3, 0.
The sintered body of the present invention (3-
b to 3-d) have high bulk density and high conductivity. Next, the above sintered body is heated to 1000% containing 5% steam.
After keeping it in an atmosphere of 100 ° C. for 100 hours and leaving it for 90 days in a relative humidity of 90% and a temperature of 85 ° C., it was allowed to cool and the dimensional change at room temperature and the conductivity at 1000 ° C. were measured. The invention sintered bodies (3-b to 3-d) did not change from the values before the heat treatment. On the other hand, in the comparative sample 3-a in which the amount of x, the bulk density and the average crystal grain size are out of the specified ranges, the dimension is increased by 3% after the similar treatment,
The strength was remarkably reduced. Further, in the comparative sample 3-e in which the amount of x was 0.55, the conductivity at 1000 ° C. after the similar treatment was significantly reduced to 15 S / cm.

Example 4 La_1-xA_xCr_1-yM_yO_ThreeBaked with the composition indicated by
Change the type of A and M and the values of x and y
And except that the firing temperature was changed as shown in Table 4.
A sintered body was manufactured in the same manner as in Example 1. Each sample used
The compositions of 4-a and 4-b are as follows. 4-a ... La_0.9Ca_0.1Cr_0.9Ni_0.1O₃ 4-b ... La_0.8Ca_0.1Sr_0.1Cr_0.95Ni_0.05O
_Three The properties of the obtained sintered body are also shown in Table 4. Table 4 Samples Firing temperature Bulk density (g / cm^Three) Particle size Conductivity      (μm) (1000 ° C S / cm) 4-a 1750 ° C. 6.2 13 15 4-b 1750 ° C. 6.3 10 25 As is clear from the results shown in Table 4, the sintered body of the present invention (4
-A and 4-b) have high bulk density and high conductivity.
I have it. Next, the above-mentioned two kinds of sintered bodies are treated with 5% steam.
Relative humidity is maintained for 100 hours in an atmosphere of 1000 ° C.
After leaving it under the condition of 90% temperature and 85 ° C for 10 days,
Allow to cool and measure dimensional change at room temperature and conductivity at 1000 ° C.
However, both values were the same as before the heat treatment.
It was

Comparative Example 1 A sintered body was produced in the same manner as in Example 1 except that the composition of the sintered body represented by the above formula was changed and the firing conditions were variously changed as shown in Table 5. . The composition of each of the samples a, b and c used is as follows. a ... La _0.9 Sr _0.1 Cr _0.8 Co _0.2 O ₃ b ... La _0.7 Sr _0.3 Cr _0.8 Ni _0.2 O ₃ c ... La _0.95 Ca _0.05 Cr _0.99 Ni _0.01 O ₃ The characteristics of the obtained sintered body are shown in Table 6. . Table 5 Test Material Burning Conditions Temperature Pressure Time ^{(hr) a 1500 ℃ 150kg /} cm 2 2 b 1650 ℃ 150kg / cm 2 12 c 1800 ℃ 2 Table 6 specimen bulk density in the air (g / cm ³⁾ particle size Conductivity (Μm) (1000 ° C S / cm) a 6.1 344 b 6.1 90 90 68 c 4.9 12 6 The JIS three-point bending strength of these sintered bodies at 1000 ° C is the sample a = 4.2 kgf. / Mm ² , sample b =
3.5 kgf / mm ² and sample c = 2.0 kgf / m
It was m ² . These values are 9.0 for the sintered body of Example 1.
It is significantly inferior to kgf / mm ² . Further, since the sample c had a low bulk density, it had air permeability and was unsuitable as a practical material. Next, the above sintered body is treated with water vapor 5
% Of 1000 ° C. for 100 hours, left at a relative humidity of 90% and a temperature of 85 ° C. for 10 days, and allowed to cool. Sample c collapsed, and the conductivity was measured. It was impossible. Further, the sample b was expanded by 1.5% as compared with that before the heat treatment, and the conductivity was lowered to 16 S / cm. Comparative Example 2 Using glass beads as the medium of the medium stirring mill, 1
A sintered body was prepared in the same manner as in Example 1 except that the powder was wet-ground for 2 hours and the average particle diameter of the synthetic powder was set to 1.0 μm, and the characteristics thereof were measured. The bulk density of the obtained sintered body is 6.4 g.
/ Cm ³ , the average crystal grain size was 20 μm, and the conductivity in the atmosphere at 1000 ° C. was 3 S / cm. Furthermore, this sintered body was heated in an atmosphere of 1000 ° C. containing 5% of steam for 10
After holding for 0 hour and leaving it for 10 days under the condition of relative humidity of 90% and temperature of 85 ° C., and then allowed to cool, the sintered body collapsed and the electrical conductivity could not be measured. When the sintered body was subjected to chemical analysis, SiO ₂ and Na ₂ O were contained in an amount of 0.3% and 0.1%, respectively.

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Claims (1)

[Claims] (1) R _1-x A _x Cr _{1- y My} O ₃ (wherein R is at least one lanthanide element; A
Is at least one of Ca and Sr; M is Co, M
at least one of n and Ni; 0.05 ≦ x ≦ 0.50; 0 <
a sintered body having a perovskite structure having a composition of y ≦ 0.30), and (2) the bulk density of the sintered body is 6.0 g / cm.
³ or more, (3) the electrical conductivity at 1000 ° C. in the atmosphere is 5 S / cm or more, (4) the average crystal grain size of the sintered body is 5 to 80 μm, and (5) 100 including 5% of water vapor.
A heat-resistant conductive sintered body, which is stable in shape and conductivity even after kept in an atmosphere of 0 ° C. for 100 hours.