JPH07277849A - Porous sintered compact, heat resistant electrode and solid electrolyte type fuel cell - Google Patents

Abstract

PURPOSE:To obtain a porous sintered compact having stability to a heat cycle when a heating-cooling cycle is applied between a temp. of 900-1,100 deg.C and a temp. of room temp. to 600 deg.C and to prevent the occurrence of cracks between a heat resistant electrode made of the porous sintered compact and other constituent material. CONSTITUTION:This porous sintered compact is made of a multiple oxide having a perovskite structure (ABO3) and contg. an Mn atom in the B site and atoms of one or more kinds of primary metals selected from among Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Y, Yb and Lu in the A site. The dimensional shrinkage of this porous sintered compact caused by a heat cycle between room temp. and 1,000 deg.C is <=0.01% per one heat cycle.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a porous sintered body, a heat resistant electrode using the same, and a solid oxide fuel cell.

[0002]

2. Description of the Related Art In solid oxide fuel cell development projects, it is important to search for stable materials at high temperatures. Therefore, the power generation temperature of the solid oxide fuel cell has conventionally been 10
In the vicinity of 00 ° C., an experiment has been conducted in which the air electrode is held for a long time and its durability is measured. As an air electrode material for a solid oxide fuel cell, a lanthanum manganite sintered body is currently considered to be promising (Energy Engineering, 13, 2, 52-68, 1990). The above-mentioned porous sintered body made of lanthanum manganite is excellent in terms of stability and heat resistance at the operating temperature of the power generator, and is therefore being paid attention to. As such lanthanum manganite sintered bodies, those having a substantially stoichiometric composition and those having a partial loss of A site (lanthanum site) (manganese-rich composition) are known. In particular, a porous sintered body made of lanthanum manganite having A site doped with Ca or Sr is regarded as a promising material for an air electrode including a self-supporting air cathode tube.

[0003]

However, the present inventor first discovered that the lanthanum manganite porous sintered body has the following problems. That is, the present inventor of the conventional lanthanum manganite porous sintered body has a power generation temperature of the solid oxide fuel cell of 900 to 1
A heating-cooling cycle was applied between a temperature of 100 ° C. and a temperature of room temperature to 600 ° C. to test its stability.
In this lanthanum manganite, the B site is not particularly replaced, and 10% to 20% of the A site is replaced by calcium, or 10% of the A site is replaced.
% To 15% were replaced by strontium.

As a result, a temperature of 900 to 1100 ° C.
It was found that when a heating-cooling cycle was applied between room temperature and 600 ° C., the dimensions of the above porous sintered body shrank by 0.01 to 0.04% per thermal cycle. Moreover, it was found that the shrinkage due to this thermal cycle did not converge even after 100 thermal cycles, and reached several percent after 100 thermal cycles. When the air electrode made of a porous sintered body contracts in this way, cracks may occur between the air electrode made of a porous sintered body and other constituent materials of the unit cell, resulting in destruction of the unit cell. There was found. Moreover,
Even when this unit cell was operated at 1000 ° C. for a long time, such a crack did not occur at all. Therefore, this phenomenon was considered not to be due to the firing shrinkage of the porous sintered body, but to the dimensional change due to the thermal cycle.

An object of the present invention is to provide a heat-resistant porous sintered body which is stable against the above heat cycle. Further, the object of the present invention, particularly in the heat-resistant electrode used in the solid oxide fuel cell, etc., due to the dimensional shrinkage of the heat-resistant electrode due to the thermal cycle, between the heat-resistant electrode and other constituent materials. The purpose is to prevent the occurrence of cracks.

[0006]

The present invention is a porous sintered body composed of a complex oxide having a perovskite structure, wherein the B site of the complex oxide contains a manganese atom. The A site of contains at least one first metal atom selected from the group consisting of praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, yttrium, ytterbium and lutetium. And the dimensional shrinkage caused by the thermal cycle between room temperature and 1000 ° C. is 0.01 per thermal cycle.
% Or less, the present invention relates to a porous sintered body.

The present invention also relates to a heat-resistant electrode comprising the above porous sintered body. The present invention also relates to a solid oxide fuel cell, characterized by comprising an air electrode made of the above-mentioned porous sintered body.

[0008]

First of all, the present inventor has studied the mechanism by which dimensional shrinkage of the porous sintered body occurs with the above thermal cycle.
I proceeded with my research. As a result, it was found that when the temperature was raised from room temperature to about 1000 ° C., the weight of the porous sintered body slightly decreased, and when the temperature was lowered to room temperature again, this weight was restored.

The mechanism by which such a phenomenon occurs is currently unknown. However, it is speculated that oxygen goes into and out of the crystal in the temperature range of 800 ° C or higher in the atmosphere due to the thermal cycle, and the crystal lattice is distorted due to this going in and out, promoting the mass transfer of metal atoms. To be done.

In the course of this research, the inventor of the present invention has made detailed studies on the composition of the complex oxide having the perovskite structure which constitutes the porous sintered body.

At present, lanthanum manganite is widely used as an air electrode material of a solid oxide fuel cell. However, the present inventor has discovered that the use of the above-mentioned specific heavy metal atom instead of lanthanum can remarkably reduce the amount of dimensional shrinkage due to the above-mentioned thermal cycle, and arrived at the present invention.

In particular, it was possible to suppress the dimensional shrinkage caused by the thermal cycle between room temperature and 1000 ° C. to 0.01% or less per thermal cycle. The dimensional shrinkage rate varies depending on the selection and composition of the heavy metal atoms described above, but can be suppressed to about 0.007% at the maximum.

As a result, particularly in a solid oxide fuel cell, such as a solid oxide fuel cell, in an electric power generation article in which an electrode made of a porous sintered body and other constituent materials are joined, a temperature of 900 to 1100 ° C. and a room temperature to 600 ° C. It was confirmed that no cracks were generated between the electrode made of the porous sintered body and the other constituent materials even when the heating-cooling cycle was performed at the temperature of.

"Dimensional shrinkage per thermal cycle" refers to the average value of each dimensional shrinkage from the first thermal cycle to the tenth thermal cycle after sintering the porous sintered body. To do.

[0015]

EXAMPLE A porous sintered body according to the present invention is composed of a complex oxide having a perovskite structure, a manganese atom is contained in the B site of the complex oxide, and praseodymium, neodymium, samarium and europium are contained in the A site. , Gadolinium, terbium, dysprosium, holmium, erbium, thulium, yttrium, ytterbium, and lutetium, and at least one first metal atom is contained. The B site may contain an atom other than a manganese atom, and the A site may contain a metal atom other than the first metal atom.

First, when the A site is occupied by the first metal atom, the dimensional shrinkage ratio due to the thermal cycle is 0.00% per 10 thermal cycles, and no dimensional shrinkage is observed. There wasn't. This composite oxide is represented by the following composition.

[0017]

[Formula 1] RMnO ₃

Here, R is praseodymium, neodymium,
It is one or more first metal atoms selected from the group consisting of samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, yttrium, ytterbium and lutetium.

In this composition, it was further confirmed that the average coefficient of linear thermal expansion was 11.8 × 10 ^-6 or less. That is, when the porous sintered body of the present invention is used as a heat-resistant electrode of a power generation article, in order to reduce the difference in thermal expansion with other constituent materials, the average linear coefficient of thermal expansion of the heat-resistant electrode. Should be kept as small as possible. In particular, when the porous sintered body of the present invention is used as an air electrode material for a solid oxide fuel cell, the average linear thermal expansion coefficient of the porous sintered body is set to the average linear thermal expansion of the solid electrolyte membrane. You have to be close to the rate.

This solid electrolyte membrane is a yttria-stabilized zirconium.
In the case of Konia, average between 25 ° C and 1000 ° C
Linear thermal expansion coefficient is 10.5 × 10^-6K^-1Known to be
ing. In this case, the average coefficient of linear thermal expansion of the porous sintered body
12.5 x 10 ^-6K^-1If suppressed below, porous sintered body
Of cracks due to the difference in thermal expansion between the solid electrolyte membrane and
Occurrence could be prevented. In particular, this is 11.8
× 10^-6K ^-1It is preferable to suppress it to the following.

From this viewpoint, in the above composition,
The average coefficient of linear thermal expansion of the porous sintered body is 11.8 × 10 ^-6 K ^-1
Since it can be suppressed to the following, it is preferable from the viewpoint of the matching of the average linear thermal expansion coefficient between the heat resistant electrode and the other constituent materials.

Next, the A site of the composite oxide is preferably occupied by the first metal atom and one or more second metal atoms selected from the group consisting of calcium and strontium. This composition can be represented by the following general formula:

[0023]

[Formula 2] R _1-X A _X MnO ₃

R is a first metal atom and A is a second metal atom. x is 0.01 or more and 0.70 or less. Here, when the content ratio of the second metal atom in the A site is 5% or less (x is 0.05 or less), the dimensional shrinkage rate due to the heat cycle is remarkably reduced.

By setting the content ratio of the second metal atom in the A site to 10% or more (x is 0.10 or more), the electric conductivity of the porous sintered body is improved. Further, by setting this to 70% or less (x is 0.70 or less), the average linear thermal expansion coefficient of the porous sintered body is 12.5 × 1.
It can be reduced to 0 ^-6, it can be kept high even electrical conductivity of the porous sintered body.

Further, by setting the content ratio of the second metal atom in the A site to 25% or more (x is 0.25 or more), the dimensional shrinkage rate of the porous sintered body due to the heat cycle is more remarkable. It was found to be reduced to. Specifically, within this range, 0.00 per thermal cycle
It was less than 2%.

Further, by setting the content ratio of the second metal atom in the A site to 30% or more (x is 0.30 or more), dimensional shrinkage of the porous sintered body due to the heat cycle is not observed. It was also found that the electric conductivity of the porous sintered body was significantly increased.

Further, by setting the content ratio of the second metal atom in the A site to 60% or less (x is 0.60 or less), the electric conductivity of the porous sintered body is more remarkably increased. . Furthermore, by setting the content rate of the second metal atom in the A site to be 50% or less (x is 0.50 or less), the average linear thermal expansion coefficient of the porous sintered body is more significantly reduced, and 11 The ^value could be suppressed to 8 × 10 ^-6 K ^-1 or less.

Further, the first metal atom is praseodymium,
Neodymium, samarium, europium, gadolinium,
1 selected from the group consisting of terbium and dysprosium
When the number of metal atoms is one or more, the electric conductivity of the porous sintered body is further increased. In this case, in particular, when the content ratio of the second metal atom in the A site is in the range of 30% to 60%, the electric conductivity of the porous sintered body is 100 S / c.
Since it exceeds m, it is preferable.

It was also found that in this case, the dimensional shrinkage ratio of the porous sintered body due to the heat cycle was relatively small. Among them, especially selected from the group consisting of praseodymium, neodymium, samarium and dysprosium 1
The use of one or more first metal atoms results in a small dimensional shrinkage rate due to the thermal cycle.

When the first metal atom is one or more metal atoms selected from the group consisting of holmium, erbium, thulium, yttrium, ytterbium and lutetium, the average coefficient of linear thermal expansion is relatively large. Becomes smaller. From this viewpoint, yttrium is particularly preferable.

Further, at least one third metal atom selected from the group consisting of aluminum, cobalt, copper, magnesium, chromium, nickel, iron, titanium and zinc is the above-mentioned B.
If you occupy more than 2% and less than 20% of the site,
This has the effect of further reducing the dimensional shrinkage ratio. In particular, A
The content ratio of the second metal atom in the site is 5% or more,
When the content is 25% or less, the dimensional shrinkage ratio due to the heat cycle is higher than the other content ratios. However, in this case, if one or more third metal atoms selected from the group consisting of aluminum, cobalt, copper, magnesium, chromium, nickel, iron, titanium and zinc occupy 2% or more of the B site. The dimensional shrinkage ratio can be suppressed to be small. In this case, this effect is particularly remarkable when the content ratio of the second metal atom in the A site is 10% or more and 20% or less.

When the content ratio of the second metal atom in the A site is 25% or more and 70% or less, the dimensional shrinkage ratio is almost 0 and the electric conductivity of the porous sintered body is high. Can be kept high. This effect is particularly remarkable when the content ratio of the second metal atom in the A site is 30% or more and 60% or less.

The general formula of such composition is shown below.

[Formula 3] R _1-X A _X Mn _1-Z E _z O ₃

R and A are as described above. E is the third metal atom. x is 0.05 to 0.70
(5% to 70%). z is 0.02 to 0.20
(2% to 20%).

When the content ratio of the third metal atom is less than 2%, the effect of reducing the dimensional shrinkage ratio is not remarkable. Therefore, it is preferable that the content ratio of the third metal atom is 2% or more. Further, when the content ratio of the third metal atom is 5% or more, the effect of reducing the dimensional shrinkage becomes more remarkable. On the other hand, if it exceeds 20%, the electrical conductivity of the porous sintered body is significantly reduced, so that the content ratio of the third metal atom in the B site is 20%.
% Or less is preferable. From this viewpoint, the content ratio of the third metal atom in the B site is more preferably 15% or less, and particularly preferably 10% or less.

As the third metal atom, one or more third metal atoms selected from the group consisting of aluminum, cobalt, copper, magnesium, nickel and chromium are more effective.

In each of the above-mentioned compositions, a composition variation of the composite oxide derived from some impurities inevitably mixed in the process for producing the porous sintered body is allowed. Further, since the complex oxide having a perovskite structure can have a non-stoichiometric composition, in the general formulas showing the respective compositions described above,
Although the ratio of A site to B site is expressed as 1: 1 for convenience, this composition ratio may vary.

In order to produce the porous sintered body according to the present invention, the raw material powders of the composite oxide are mixed to produce a mixed powder, the mixed powder is molded, and the molded body is fired to synthesize. It is preferred to produce the product and grind the composition.
At this time, the ratio of each metal atom in the composite oxide is controlled by changing the mixing ratio of the raw material powder of the composite oxide.

The firing temperature of the molded body is 1300 ° C to 160 ° C.
The temperature is preferably 0 ° C. If the firing temperature is less than 1300 ° C, the sintering will not be completed completely. If the temperature is higher than 1600 ° C, the structure of the sintered body will be too dense.

The porous sintered body produced according to the present invention is
In particular, it can be preferably used as a material for a heat resistant electrode which is stable against heat cycles. Such heat-resistant electrode materials include electrode materials for power generation products such as fusion reactors and MHD power generation.

The porous sintered body of the present invention can be particularly preferably used as an air electrode material for a solid oxide fuel cell. Further, it is preferably used as a material for a self-supporting air electrode substrate. Such an air electrode base is used as a base material of a single cell, and each component such as a solid electrolyte membrane, a fuel electrode membrane, an interconnector and a separator is laminated on the air electrode base. At this time, the shape of the air electrode substrate may be a cylindrical shape with both ends open, a bottomed cylindrical shape with one end open and the other end closed, or a flat plate shape. Of these, one of the above cylindrical shapes
It is particularly preferable because it is less likely to be subjected to thermal stress and gas sealing is easy.

The porosity of the porous sintered body is preferably 5 to 40%. When it is used as an air electrode material for a solid oxide fuel cell, the porosity is further increased to 1
It is preferably 5 to 40%, and more preferably 25 to 35%. In this case, the porosity of the air electrode should be 15%.
With the above, the gas diffusion resistance is reduced, and the porosity is set to 40% or less, so that a certain level of strength can be secured.

Hereinafter, more specific experimental results will be described. [Experiment A: Example of lanthanum manganite porous sintered body] As starting materials, La ₂ O ₃ , CaCO ₃ , and Sr
Powders of CO ₃ and Mn ₃ O ₄ were used. A predetermined amount of starting materials was weighed and mixed for each sample so that the composition ratio shown in Table 1 was obtained. This mixed powder was molded by a cold isostatic press method at a pressure of 1 tf / cm ² to prepare a molded body. In the air,
Heat treatment was performed at 1500 ° C. for 15 hours to synthesize composite oxides having the respective compositions shown in Table 1. However, the composition is La _1-X A _X Mn
O ₃ , and Table 1 shows the value of x and A.

This synthetic material was ground with a trommel for 8 to 12 hours to prepare a synthetic powder having an average particle diameter of 2 to 6 μm. Next, water and an acrylic binder as an organic binder were added to and mixed with this synthetic powder to prepare a slurry having a water content of 40%, and granulated with a spray dryer. Then, this granulated powder and an acrylic powder as a pore-forming agent are dry-mixed and molded by a cold isostatic press method at a pressure of 1 tf / cm ² to give an outer diameter of 20 m.
An annular shaped body having a diameter of m and an inner diameter of 10 mm was produced, and this tubular shaped body was fired at 1300 ° C to 1600 ° C for 5 hours to obtain a fired body. From this tubular sintered body, a tubular sample having a length of 50 mm was cut out.

When the porosity of each sample was measured by the water substitution method, all were 30% ± 1%.

Further, the dimensional shrinkage ratio by the heat cycle was measured as follows. In other words, each sample was
The temperature was raised to 600 ° C at a rate of 600 ° C / hour, and then 600
10 ° C with 200 ° C / hour
A heat cycle was applied and the temperature was lowered to room temperature. At this time, in each heat cycle, 30 at 600 ℃ and 1000 ℃, respectively.
A constant temperature was maintained for a minute. Then, the dimension of each sample was measured using a micrometer, and the dimensional shrinkage before and after the thermal cycle was calculated. Table 1 shows the dimensional shrinkage rate per 10 thermal cycles.

[0048]

[Table 1]

As can be seen from Table 1, the dimensional shrinkage ratio by the heat cycle is 0.012 per heat cycle.
It reached 0.034%. In particular, this dimensional shrinkage peak was present in the range of 10 to 20% in the content of calcium or strontium at the A site.

Further, the inventor measured the dimensional change of the porous sintered body by increasing and decreasing the temperature from room temperature to 1000 ° C. for each sample shown in Table 1 and using a thermal expansion meter. As a result, the dimensional shrinkage phenomenon is 900
We have identified what is happening in the temperature range of ℃ to 800 ℃. Therefore, it is assumed that oxygen atoms are absorbed and metal atoms are moved in this temperature range. Further, the result of the thermal cycle between 600 ° C. and 1000 ° C., which is the condition of this experiment, is the same as the result of the thermal cycle between room temperature and 1000 ° C.

A sample having a calcium content of 15% was kept in the atmosphere at 1000 ° C. for 10 hours,
After cooling to room temperature, the dimensional change rate before and after heating was measured, and it showed 0.031% shrinkage. on the other hand,
Looking at Table 1, regarding the 10 thermal cycles after firing,
The dimensional shrinkage rate per thermal cycle was 0.034%. Therefore, the shrinkage of 0.031% substantially corresponds to the dimensional shrinkage of one heat cycle.

From this result, the above-mentioned 0.034% dimensional shrinkage did not occur during the holding at 1000 ° C., but during the temperature decreasing process from 1000 ° C. to room temperature. is there. In other words, the shrinkage phenomenon of the porous sintered body due to the above-mentioned thermal cycle is caused by a mechanism completely different from the progress of sintering due to the holding of the porous sintered body at a high temperature.

[Experiment B] As a starting material, Pr ₆ O ₁₁ ,
Nd ₂ O ₃ , Sm ₂ O ₃ , Dy ₂ O ₃ , Yb ₂ O ₃ , Y
Powders of ₂ O ₃ , CaCO ₃ , SrCO ₃ , and Mn ₃ O ₄ were used. To obtain the composition ratios shown in Table 2 and Table 3,
For each sample number, a predetermined amount of starting material was weighed and mixed. This mixed powder was molded by a cold isostatic press method at a pressure of 1 tf / cm ² to prepare a molded body. This molded body is heated in the atmosphere at 1500 ° C. for 15
Heat treatment was performed for a period of time to synthesize composite oxides having the respective compositions shown in Tables 2 and 3.

However, the composition shown in Table 2 is R _{1 -X} Ca _X
It is MnO ₃ , and Table 2 shows the value of x and R. The composition shown in Table 3 is R _1-X Sr _X MnO ₃ , and Table 3 shows that
The value of x and R are shown.

This synthetic material was pulverized with a trommel for 8 to 12 hours to prepare a synthetic powder having an average particle diameter of 2 to 6 μm. Next, water and an acrylic binder as an organic binder were added to and mixed with this synthetic powder to prepare a slurry having a water content of 40%, and granulated with a spray dryer. Then, this granulated powder and an acrylic powder as a pore-forming agent are dry-mixed and molded by a cold isostatic press method at a pressure of 1 tf / cm ² to give an outer diameter of 20 m.
An annular shaped body having a diameter of 10 mm and an inner diameter of 10 mm was produced, and this tubular shaped body was fired at 1300 ° C. to 1600 ° C. for 5 hours to obtain a fired body having a porosity of 30% ± 1%. From this tubular sintered body, a tubular sample having a length of 50 mm was cut out.

Each of the samples shown in Tables 2 and 3 was ground in a mortar and subjected to X-ray diffraction measurement by the powder method.
As a result, each diffraction pattern of each sample number was almost the same and showed a single phase.

For each of the samples shown in Tables 2 and 3, the dimensional shrinkage rate due to the heat cycle was measured as described above. The results are shown in Tables 2 and 3.

[0058]

[Table 2]

[0059]

[Table 3]

First, when the A site is occupied by the first metal atom (when x = 0.00),
The dimensional shrinkage is 0.00% per 10 thermal cycles
And no dimensional shrinkage was observed. Next, A
When the content ratio of the second metal atom in the site is 5% or less (x is 0.05 or less), the dimensional shrinkage rate due to the heat cycle is remarkably reduced.

Further, by setting the content ratio of the second metal atom in the A site to be 25% or more (x is 0.25 or more), the dimensional shrinkage ratio of the porous sintered body can be more significantly reduced. ing. Specifically, within this range, the thermal cycle was 0.002% or less per thermal cycle. Furthermore, when this is set to 0.30 or more, the dimensional shrinkage becomes 0.00%, and even if x is further increased, dimensional shrinkage due to the thermal cycle is not observed at all.

Further, when one or more first metal atoms selected from the group consisting of praseodymium, neodymium, samarium and dysprosium are used, the dimensional shrinkage ratio due to the heat cycle becomes relatively small.

[Experiment C: Evaluation of Average Coefficient of Linear Thermal Expansion of Porous Sintered Body] In Experiment B, R _{1 -X} Ca _X Mn shown in Table 2 was used.
For the O ₃ system, R was changed as shown in Table 2 and x was changed as shown in Table 2, and as in Experiment B, Table 2
A porous sintered body made of the composite oxide having each composition shown in was produced. The average coefficient of linear thermal expansion between 25 ° C. and 1000 ° C. was measured for each of these samples, and the measurement results are shown in the graph of FIG. However, in FIG. 1, the horizontal axis represents the content ratio of calcium at the A site, and the vertical axis represents the value of the average linear thermal expansion coefficient.

As can be seen from FIG. 1, for the composition having a calcium content of 0, the average coefficient of linear thermal expansion of the porous sintered body was 11.8 × 10 ⁻⁶ or less. Moreover, when the content ratio of calcium is 70% or less (x = 0.70 or less), the average linear thermal expansion coefficient of the porous sintered body is 12.5 × 10 5.
^It can be seen that it becomes ^-6 K ^-1 or less.

Further, by setting the content ratio of calcium to 50% or less (x is 0.50 or less), the average linear thermal expansion coefficient of the porous sintered body is further remarkably reduced, and 11.8 × 10 5
^-6 K ^-1 or less. When the first metal atom is yttrium or ytterbium,
The average linear thermal expansion coefficient of the porous sintered body becomes relatively small. The substitution atom (second metal atom) at the A site was changed to strontium, and an experiment was conducted to obtain the same measurement results as above.

[Experiment D: Evaluation of Electric Conductivity of Porous Sintered Body] In Experiment B, R _{1 -X} Ca _X MnO ₃ shown in Table 2 was used.
In the system of No. 2, R was changed as shown in Table 2 and x was changed as shown in Table 2, and like Experiment B, a porous sintered body made of the composite oxide of each composition shown in Table 2 was used. Was manufactured. Each of these samples was evaluated for electrical conductivity at 1000 ° C. This measurement is performed in the atmosphere at 1000 ° C.
The DC four-terminal method was used. However, in order to eliminate the influence on the electric conductivity due to the difference in the porosity of the porous sintered body, the measurement data was corrected by calculation so that the value at the porosity of 30% was obtained.

The results are shown in FIG. However, in FIG. 2, the horizontal axis represents the content ratio of calcium in the A site, and the vertical axis represents the electric conductivity value (S / cm). Figure 2
As can be seen from the result, by setting the content ratio of calcium in the A site to 10% or more (x is 0.10 or more), the electric conductivity of the porous sintered body is higher than that in the case where calcium is not substituted. Greatly improved. Further, by setting this to 70% or less (x is 0.70 or less), the electric conductivity of the porous sintered body can be kept higher than that in the case where calcium is not substituted.

Further, by setting the content ratio of calcium in the A site to 30% or more (x is 0.30 or more), the electric conductivity of the porous sintered body was further remarkably increased.
Furthermore, the content ratio of calcium in the A site is 60%.
By setting the ratio to be equal to or less than (x is 0.60 or less), the electrical conductivity of the porous sintered body was further significantly increased.

Further, the first metal atom is praseodymium,
When neodymium, samarium, or dysprosium is used, the electric conductivity of the porous sintered body is further increased. In this case, it is particularly preferable that the content ratio of the second metal atom in the A site is in the range of 30% to 60% because the electric conductivity of the porous sintered body exceeds 100 S / cm. The substitution atom (second metal atom) at the A site was changed to strontium, and an experiment was conducted to obtain the same measurement results as above.

[Experiment E: Said size by substitution of B site
Effect on Shrinkage] In Experiment B, Pr₆O₁₁, Nd₂
O₃, Sm₂O₃, Y₂O₃, CaCO ₃, SrC
O₃, Mn₃O_Four, NiO, CoO, MgCO₃Each powder of
The same as in Experiment B, except that each powder shown in Table 4 and Table 5 was used.
To produce a porous sintered body composed of a composite oxide having a composition
It was Then, for each porous sintered body sample, the thermal cycle
The dimensional shrinkage due to Kuru was measured. The results are shown in Table 4 and Table
5 shows.

[0071]

[Table 4]

[0072]

[Table 5]

However, in Tables 4 and 5, the content ratio of calcium in the A site was set to 15%. As can be seen from Tables 2 and 3, the calcium content is 1
This is because the dimensional shrinkage ratio is maximized when it is 5%. The strontium content is 10%
Set to.

In the composition shown in Table 4, calcium is used as the substitution metal atom at the A site, nickel is used as the substitution metal atom at the B site, and the content ratio of nickel is 0 to 25% (z = 0.00). ~ 0.25)
Changed within the range. As a result, it was observed that the dimensional shrinkage ratio was reduced when the content ratio of the third metal atom was 2% or more (z = 0.02 or more). In particular, when the content ratio of the third metal atom in the B site is 5% or more (z = 0.05 or more), the effect of reducing the dimensional shrinkage ratio is particularly large.

In each composition shown in Table 5, the content ratio of the third metal atom in the B site was set to 5%, each metal atom was variously changed, and the effect on the dimensional shrinkage ratio was observed. . As a result, a remarkable effect was observed in any composition.

[Experiment F: Effect of Substitution of B Site on Electric Conductivity] In the same manner as in Experiment E, a porous sintered body made of a composite oxide having each composition shown in Table 4 was produced. That is, N
d _0.85 Ca _0.15 Mn _1-Z Ni _z O ₃ system and Y _0.85 Ca
Regarding the porous sintered body composed of the complex oxide having the composition of _0.15 Mn _1-Z Ni _z O ₃ , the nickel content ratio z was changed as shown in FIG. The degree was measured by the method described above. The result is shown in FIG.

As can be seen from FIG. 3, as the nickel content increases, the electric conductivity of the porous sintered body tends to decrease. However, this tendency of decrease in electrical conductivity is not remarkable as long as z is small. Specifically, the content ratio of nickel is preferably 20% or less,
Further, it is understood that it is preferably 15% or less, and particularly preferably 10% or less.

In Experiment F, aluminum, cobalt, copper, magnesium and chromium were used instead of nickel as the third metal atom, and the same results as above were obtained.

[0079]

As described above, the porous sintered body of the present invention has the following characteristics when subjected to a heating-cooling cycle between a temperature of 900 to 1100 ° C and a temperature of room temperature to 600 ° C. It is stable against heat cycles. Therefore, the heat-resistant electrode formed by this porous sintered body, because the dimensional shrinkage due to the above-mentioned thermal cycle is extremely small, cracks occur between the heat-resistant electrode and other constituent materials, It can be prevented.

[Brief description of drawings]

FIG. 1 shows a porous sintered body composed of a composite oxide having a composition of the system R _1-X Ca _X MnO ₃ and the content ratio x of the first metal atom and calcium constituting R and the porous calcination. It is a graph which shows the relationship with the average linear thermal expansion coefficient of 25 degreeC-1000 degreeC of a binding body.

FIG. 2 shows the content ratio x of the first metal atom and R constituting R and the porous calcination of the porous sintered body composed of the composite oxide having the composition of R _{1 -X} Ca _X MnO _3. It is a graph which shows the relationship with the electrical conductivity of the bound body at 1000 degreeC.

FIG. 3 shows a nickel _- based porous sintered body composed of a composite oxide having a composition of Nd _0.85 Ca _0.15 Mn _1-Z Ni _z O ₃ system and Y _0.85 Ca _0.15 Mn _1-Z Ni _z O ₃ system. 2 is a graph showing the relationship between the content ratio z of the porous sintered body and the electric conductivity of the porous sintered body at 1000 ° C.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location H01M 8/12 9444-4K

Claims (13)

[Claims] 1. A porous sintered body composed of a complex oxide having a perovskite structure, wherein the B site of the complex oxide contains a manganese atom, and the A site of the complex oxide contains praseodymium and neodymium. , Samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, yttrium, ytterbium and lutetium, containing at least one first metal atom at room temperature and 100.
A dimensional shrinkage caused by a heat cycle between 0 ° C. and 0.01% or less per heat cycle, the porous sintered body. 2. The porous sintered body according to claim 1, wherein the A site is occupied by the first metal atom. 3. The A site comprises the first metal atom,
The porous sintered body according to claim 1, characterized in that it is occupied by one or more second metal atoms selected from the group consisting of calcium and strontium. 4. The porous sintered body according to claim 3, wherein the content ratio of the second metal atom in the A site is 5% or less. 5. The porous sintered body according to claim 3, wherein the content ratio of the second metal atom in the A site is 10% or more and 70% or less. 6. The porous sintered body according to claim 5, wherein the content ratio of the second metal atom in the A site is 25% or more and 60% or less. 7. The content ratio of the second metal atom in the A site is 5% or more and 25% or less, and aluminum, cobalt, copper, magnesium, chromium, nickel,
The porous calcination according to claim 3, wherein one or more third metal atoms selected from the group consisting of iron, titanium and zinc occupy 2% or more and 20% or less of the B site. Union. 8. The content of the second metal atom in the A site is 25% or more and 60% or less and is selected from the group consisting of aluminum, cobalt, copper, magnesium, chromium, nickel, iron, titanium and zinc. 2% or more, 20% or more of the B site of one or more selected third metal atoms
The porous sintered body according to claim 3, characterized by occupying the following. 9. The first metal atom is selected from the group consisting of praseodymium, neodymium, samarium, europium, gadolinium, terbium and dysprosium.
1 or more metal atoms, Claim 1
8. The porous sintered body according to any one of items 8. 10. The first metal atom is one or more metal atoms selected from the group consisting of holmium, erbium, thulium, yttrium, ytterbium, and lutetium, wherein the first metal atom is one or more. The porous sintered body according to any one of items. 11. A heat-resistant electrode comprising the porous sintered body according to any one of claims 1 to 10. 12. A solid oxide fuel cell, comprising an air electrode made of the porous sintered body according to any one of claims 1 to 10. 13. The solid oxide fuel cell according to claim 12, wherein the air electrode is a self-supporting air electrode.