JPH07277850A - Porous sintered body, article for power generation and production of porous sintered body - Google Patents

Abstract

PURPOSE:To control physical properties of a porous sintered body and to satisfy the various requirements for the porous sintered body by controlling the composition of the porous sintered body. CONSTITUTION:A porous sintered body consists of perovskite type multiple oxide (ABO3). One or more main metal atoms selected from the group consisting of rare earth atoms and yttrium are contained in the A site of the mutiple oxide, and manganese is contained in the B site of the multiple oxide. One or more substituted metal atoms selected from the group consisting of calcium, strontium, aluminum, cobalt, magnesium, nickel, chromium, copper, iron, titanium and zinc are contained in the multiple oxide. Near the surface of pores 2 of the porous sintered body, there exists a surface layer having a relatively high content of the substituted metal atoms. Inside the surface layer 4, there exists an inside layer 3 having relatively low content of the substituted metal atoms.

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 which can be suitably used in a solid oxide fuel cell and the like, and a method for producing the same.

[0002]

2. Description of the Related Art Solid oxide fuel cells (SOFC) are
Since it operates at a high temperature of 1000 ° C, the electrode reaction is extremely active and does not require any expensive precious metal catalyst such as platinum.
Since the polarization is small and the output voltage is relatively high, the energy conversion efficiency is significantly higher than that of other fuel cells. Furthermore, since the structural material is composed entirely of solid, it is stable and has a long life. In SOFC development projects, it is important to search for stable materials at high temperatures. As an air electrode material for SOFC, a lanthanum manganite sintered body is currently considered to be promising (Energy Engineering, 13, 2, 52-68).
P., 1990). 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. Especially, C on A site
A porous sintered body made of lanthanum manganite doped with a and Sr is regarded as a promising material for an air electrode including a self-supporting air cathode tube.

However, it has been found that such a porous sintered body has the following problems. That is, SOF
When a heating-cooling cycle is applied between the temperature of 900 to 1100 ° C., which is the power generation temperature of C, and the temperature of room temperature to 600 ° C., the air cathode tube made of the above-mentioned porous sintered body and other cells It was found that a crack was generated between the constituent materials of (1) and (4) and the unit cell was destroyed. Moreover, 100
Even when operated at 0 ° 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.

As a method for solving this problem, the applicant of the present invention has described in Japanese Patent Application No. 5-49314, A
A technique has been disclosed in which the dimensional shrinkage ratio is reduced by increasing the substitution amount of calcium and strontium in the porous sintered body made of lanthanum manganite doped with Ca and Sr at the site.

However, new problems have become clear in the course of further study by the present inventor. That is, when the substitution amount of calcium and strontium in the porous sintered body is increased, the average linear thermal expansion coefficient of the porous sintered body is increased, and the thermal expansion difference with the solid electrolyte membrane is increased. The possibility of cracks due to the difference in expansion increased. It was also found that the amount of creep or deformation due to heat increases at a high temperature of about 1000 ° C. As described above, it has been difficult to satisfy these various requirements for the heat resistant electrode by using the conventional porous sintered body.

An object of the present invention is to control the physical properties of the porous sintered body by controlling the composition of the porous sintered body so that various requirements for the porous sintered body can be satisfied. Is.

[0007]

The porous sintered body according to the present invention comprises a perovskite type complex oxide, and at least one selected from the group consisting of rare earth atoms and yttrium at the A site of the complex oxide. Of the complex oxide contains B at the B site, and the complex oxide contains calcium, strontium, aluminum, cobalt, magnesium, nickel, chromium, copper, iron, titanium and zinc. Containing one or more substituted metal atoms selected from the group consisting of, in the vicinity of the surface of the pores of the porous sintered body, there is a surface layer having a relatively high content of substituted metal atoms, Inside this surface layer,
It is characterized by the presence of an inner layer having a relatively low content of substituted metal atoms.

The present invention also relates to a power generation article having a heat resistant electrode made of the above-mentioned porous sintered body.

Further, the method for producing a porous sintered body according to the present invention is a porous sintered body material composed of a perovskite type complex oxide, wherein a rare earth atom and yttrium are added to the A site of the complex oxide. Producing a porous sintered body material containing one or more main metal atoms selected from the group consisting of manganese at the B site of the composite oxide,
This porous sintered material is used in a liquid containing a compound of one or more substituted metal atoms selected from the group consisting of calcium, strontium, aluminum, cobalt, magnesium, nickel, chromium, copper, iron, titanium and zinc. The liquid is adhered to the inside of the pores of the porous sintered body material, the compound is deposited in the pores, and then the porous sintered body material is heat treated to obtain the pores of the porous sintered body. A surface layer having a relatively high content of substituted metal atoms is formed in the vicinity of the surface.

The present inventor was engaged in the research for preventing the dimensional shrinkage phenomenon due to the heat cycle, which will be described later.
In this process, it was attempted to treat the porous sintered body as follows. This process will be described with reference to FIGS. 1 and 2.

First, a porous sintered body material made of a perovskite type complex oxide is prepared. FIG. 1 is a cross-sectional view showing an example of the microstructure of this porous sintered body material, which is transcribed based on a scanning electron micrograph. Pores 2 are formed in the porous sintered body material 1.

Next, the porous sintered body material 1 is dipped in a liquid containing a specific additive metal compound, and this liquid is
The porous sintered body material 1 was made to adhere to the inside of the pores 2 to deposit this compound in the pores, and then the porous sintered body material 1 was heat treated. As a result, after the porous sintered body material 1 is heat-treated, as shown in FIG. 2, in the vicinity of the surface of the porous sintered body, the surface layer 4 in which the content ratio of the above-mentioned specific additive metal is relatively high. Was successfully formed. At the same time, the inner layer 3 having a relatively low content ratio of the substitution metal atom was formed inside the surface layer 4.

When various physical properties of such a porous sintered body are measured, the characteristics of the creep due to heat, the average linear thermal expansion coefficient and the like, which will be described later, are relatively influenced by the composition of the inner layer 3. It was found that the physical properties of the surface layer 4 covering the vicinity of the surface of the pores have a relatively strong influence on the dimensional shrinkage due to the heat cycle as will be described later. As a result, by controlling the composition of the porous sintered body,
It has become possible to control the physical properties of the porous sintered body so as to satisfy various requirements for the porous sintered body.

[0014]

EXAMPLE Next, the dimensional shrinkage phenomenon of the porous sintered body due to the heat cycle will be described. As described in Japanese Patent Application No. 5-49314, a researcher of the present applicant has proposed that a conventional lanthanum manganite porous sintered body is 900-1.
A heating-cooling cycle was run between 100 ° C and room temperature to 600 ° C to test its stability. In this lanthanum manganite, the B site is not particularly substituted, and is 10 mol% to 20 mol% of the A site.
Is replaced by calcium, or 10 mol% to 15 mol% of the A site is replaced by strontium.

As a result, it was found that the size of the above-mentioned porous sintered body shrank by 0.01 to 0.04% per thermal cycle. Moreover, the shrinkage due to this thermal cycle is
It was found that the heat treatment did not converge even after 100 heat cycles, and reached several percent after 100 heat cycles. When the air electrode contracts in this way, a crack is generated between the air electrode and other constituent materials of the unit cell, which causes destruction of the unit cell.

The present applicant has conducted research to solve this problem, and as a result, by setting the substitution amount of calcium and strontium at the A site to 25% or more, the thermal cycle between room temperature and 1000 ° C. It has been discovered that the dimensional shrinkage caused by the above can be suppressed to 0.01% or less per one thermal cycle. Moreover, by this, the temperature of 900 to 1100 ° C and the room temperature to 600 °
It was confirmed that no crack was generated between the porous sintered body and the other constituent materials even when the heating-cooling cycle was performed between the temperature and the temperature of C.

"Dimensional shrinkage rate per thermal cycle" refers to the average value of each dimensional shrinkage from the first thermal cycle to the 10th or 100th thermal cycle after the porous sintered body is manufactured. I shall.

In addition, the applicant of the present invention, the B site 35% by weight
It has been discovered that the dimensional shrinkage caused by the thermal cycle between room temperature and 1000 ° C. can be suppressed to 0.01% or less per the above thermal cycle by including the following predetermined substituted metal atom. .

However, if the content ratio of the substitution metal atom is increased in the porous sintered body, the average linear thermal expansion coefficient of the porous sintered body is increased as described above, and
It was also found that at high temperatures of about 000 ° C, the amount of creep or deformation due to heat increases.

Particularly, the solid electrolyte membrane of the solid oxide fuel cell is usually formed of 8 mol% yttria-stabilized zirconia, and the average coefficient of linear thermal expansion is 10.5.
Is a ~10.7 × 10 ^-6 / ° C, increasing the content of the substituted metal atom as described above, the average linear thermal expansion coefficient becomes 11.0 × 10 ^-6 / ° or more C, The conformity of the average linear thermal expansion coefficient deteriorates. Therefore, when the number of heat cycles increases, the amount of power generation may decrease due to the consistency of the average linear thermal expansion coefficient and the creep due to heat.

On the other hand, according to the present invention, the composite oxide is prepared by adding one or more substituted metal atoms selected from the group consisting of calcium, strontium, aluminum, cobalt, magnesium, nickel, chromium, copper, iron, titanium and zinc. And the total content of substituted metal atoms in the inner layer at each site is 5% or more, 2
If the content of the substituted metal atoms in the surface layer at each site is 25% or more (preferably 70% or less, more preferably 50% or less), the content of the substituted metal atoms in the surface layer is set to 0% or less. The dimensional shrinkage rate due to thermal cycling was significantly reduced. Moreover, the average coefficient of linear thermal expansion hardly increased, and creep due to heat could be prevented.

As a result, even if the power generator is repeatedly used, it is possible to prevent the power generation output from being reduced and the cell from being destroyed. Therefore, the life of the power generation article having the above-mentioned porous sintered body as a heat resistant electrode was remarkably improved. In particular, the most remarkable effect was confirmed in the solid oxide fuel cell.

The total content of substitution metal atoms at each site in the inner layer is 5% or more and 20% or less, and the total content of substitution metal atoms at each site in the surface layer is 25% or more. The reason why such a remarkable effect is obtained is considered as follows.

First, in this porous sintered body, the total content of substitutional metal atoms at each site in the surface layer is 25%.
As described above, the composition does not easily cause dimensional shrinkage due to the thermal cycle. And according to the research by the present inventor,
It is considered that the dimensional shrinkage due to this heat cycle occurs during the process in which the complex oxide absorbs and discharges oxygen in the air. If the absorption and discharge of this oxygen and the accompanying formation of a crystal lattice can be prevented, the heat cycle It is considered that the dimensional shrinkage due to

From this point of view, even if the entire porous sintered body is not made of a composition that does not easily cause dimensional shrinkage, the surface of the pores can be formed by such a material, so that By preventing the absorption and discharge of oxygen, it is possible to sufficiently prevent the dimensional shrinkage due to the heat cycle.

On the other hand, the composition of the matrix or the inner layer inside the surface layer is such that the total content of substitution metal atoms at each site is 5% or more and 20% or less. With the same composition, the average linear thermal expansion coefficient of the entire porous sintered body is substantially determined by the composition of this inner layer. Furthermore,
The porous sintered body having the composition of the inner layer is relatively excellent in heat resistance, and the heat resistance of the entire porous sintered body is strongly influenced by the inner layer. Therefore, even if the porous sintered body is held at a high temperature for a long time, there is little creep due to heat.

Further, in the porous sintered body of the present invention,
It is preferable to substitute the composite oxide with one or more substitution metal atoms selected from the group consisting of calcium, strontium, aluminum, cobalt, magnesium, nickel and chromium.

Further, in the composite oxide, it is substituted with one or more substituted metal atoms selected from the group consisting of aluminum, magnesium and nickel, and substituted with one or more substituted metal atoms selected from the group consisting of calcium and strontium. In addition, when the content ratio of the substituted metal atom is 25% or more in the entire porous sintered body, the dimensional shrinkage due to the heat cycle described above can be suppressed, but the amount of aluminum, magnesium, or nickel is contained. Only then, the electrical resistance of the electrode increases. Particularly, in the solid oxide fuel cell, the power generation output of the single cell is reduced.

However, in the composite oxide, substitution with one or more substitution metal atoms selected from the group consisting of aluminum, magnesium and nickel, and substitution with one or more substitution metal atoms selected from the group consisting of calcium and strontium. In this case, the total content of the substitution metal atoms in each site in the inner layer is 5% or more and 20% or less, and the total content of the substitution metal atoms in each surface layer is 25% or more (preferably Is 70% or less, and more preferably 50% or less), the overall electric resistance is reduced and the power generation output is improved.

In particular, in the composite oxide, when the composite oxide is replaced by one or more kinds of substitution metal atoms selected from the group consisting of calcium, strontium and cobalt, each of the substitution metal atoms in the surface layer is When the sum of the content ratios at the sites is 25% or more, the electron conductivity of the surface of the pores is improved, and as a result, the electron conductivity of the entire porous sintered body is remarkably improved.

The manufacturing method of the present invention will be further described. First, a porous sintered body material is manufactured. At this stage, it is preferable to mix the raw material mixture of the composite oxide to produce a mixed powder, form the mixed powder, calcination the compact to produce a synthetic product, and pulverize the synthetic product. 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 16 ° C.
The temperature is preferably 00 ° C. Firing temperature 1300 °
If it is less than C, sintering is not completely completed. 1600 °
If it is higher than C, the structure of the sintered body becomes too dense.

After the porous sintered body material is prepared, it is immersed in a liquid containing the compound of the substituted metal atom so that the liquid adheres to the inside of the pores of the porous sintered body material. May be a liquid such as an aqueous solution, an alcohol solution, a colloidal solution, or the like that allows the compound to penetrate into the pores. In the liquid, in addition to the compound of the substituted metal atom,
You may contain the metal which comprises a porous sintered compact raw material, such as lanthanum and manganese.

At the stage of depositing this compound in the pores, the temperature is raised to dry the porous sintered body material,
It can be vacuum dried or freeze dried. Further, by supplying the alkali into the pores, the hydroxide of the metal can be precipitated and precipitated inside the pores.

Then, the porous sintered body material is heat-treated,
A surface layer having a relatively high content of substituted metal atoms is formed near the surface of the pores.
It is preferable to carry out at C to 1500 ° C., preferably for 4 to 8 hours.

The thickness of the surface layer is preferably 0.2 μm or more from the viewpoint of preventing absorption and discharge of oxygen on the surface of pores. Further, it is preferably 3 μm or less in view of the actual diffusion rate.

The composition of the preferable complex oxide will be illustrated. The A site of the composite oxide contains at least one metal atom selected from the group consisting of rare earths and yttrium, and the B site contains manganese.

First, in a preferred embodiment, the A site of the composite oxide contains at least one metal atom selected from the group consisting of calcium and strontium. This composite oxide preferably has a composition represented by the following general formula (I).

[0039]

[Formula 1] R _1-X A _X MnO ₃ (I)

Here, R and A occupy the A site of the composite oxide, and Mn occupies the B site of the composite oxide. R is at least one metal atom selected from the group consisting of rare earths and yttrium. A is one or more metals selected from the group consisting of calcium and strontium. x
Is the content ratio of this metal atom, x is 0.25 or more (preferably 0.70 or less, more preferably 0.50 or less) in the surface layer, and in the inner layer,
x is 0.05 to 0.20. Further, R is preferably lanthanum.

A composite oxide having the following composition of general formula (II) is preferred.

[0042]

[Formula 2] R _1-X A _X Mn _1-Z E _z O ₃ (II)

R has been described above. A is one or more first substituted metal atoms selected from the group consisting of calcium and strontium. E is contained in the B site,
It is one or more second substituted metal atoms selected from the group consisting of aluminum, cobalt, magnesium, nickel, chromium, copper, iron, titanium and zinc.

In the surface layer, (x + z) is 0.25
Or more (preferably 0.70 or less, more preferably 0.5
0 or less), and (x + z) is 0.
It is 05 to 0.20. Furthermore, in the inner layer, x
Is preferably 0.10 or more and z is preferably 0.10 or less from the viewpoint of ensuring the electric conductivity required as an electrode element. Further, R is preferably lanthanum.

In another preferred composition, the A site of the composite oxide contains two or more kinds of the main metal atoms, and one or more substituted metal atoms selected from the group consisting of calcium and strontium. It is contained. The composition of this composite oxide is preferably represented by the following general formula (III).

[0046]

[Formula 3] R _1-XY A _X D _Y MnO ₃ (III)

R, A and D occupy the A site of the composite oxide. A is one or more substituted metal atoms selected from the group consisting of calcium and strontium. R and D are the main metal atoms and are different from each other.

In the surface layer, x is 0.25 or more (preferably 0.70 or less, more preferably 0.50 or less).
In the inner layer, x is 0.05 to 0.20.

The "group consisting of rare earth atoms and yttrium" is a group consisting of cerium, yttrium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium and lutetium.

Further, it is preferable that R is lanthanum, and in this case, D is praseodymium, neodymium, samarium, dysprosium, gadolinium,
It is preferably selected from the group consisting of yttrium. In this case, further, the replacement ratio y by D is
It is preferable that 1 to 80% of A site is 20 to 20%
It is more preferably 50%. Further, the proportion of lanthanum at the A site (1-x-y) is preferably 1% to 76%.

The composition of the composite oxide is preferably represented by the following general formula (IV).

[0052]

[Formula 4] La _1-XY A _X D _Y Mn _1-z E _z O ₃ (IV)

R and D are the main metal atoms. A is
It is the first substituted metal atom. E is the second substituted metal atom.

In the surface layer, (x + z) is 0.25
Or more (preferably 0.70 or less, more preferably 0.5
0 or less), and (x + z) is 0.
It is 05 to 0.20. Furthermore, in the inner layer, x
Is preferably 0.10 or more and z is preferably 0.10 or less from the viewpoint of ensuring the electric conductivity required as an electrode element.

Further, it is preferable that R is lanthanum, and in this case, D is praseodymium, neodymium, samarium, dysprosium, gadolinium,
It is preferably selected from the group consisting of yttrium. In this case, further, the replacement ratio y by D is
It is preferable that 1 to 80% of A site is 20 to 20%
It is more preferably 50%. Further, the proportion of lanthanum at the A site (1-x-y) is preferably 1% to 76%.

Since the complex oxide can have a non-stoichiometric composition, the composition variation of the complex oxide due to some impurities inevitably mixed in the process for producing the porous sintered body is
Permissible. Further, in each of the above general formulas, a general formula of stoichiometric composition is shown, but a complex oxide having a non-stoichiometric composition can be used.

The porous sintered body of the present invention has a temperature of 900 °
It can be preferably used as a heat-resistant electrode operated at a temperature of C to 1100 ° C. Such heat-resistant electrodes include electrode materials used in nuclear fusion reactors, MHD power generation, and the like.

Further, the porous sintered body of the present invention is SOFC
It can be used particularly preferably as an air electrode material for the. Furthermore,
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, any of the above-mentioned cylindrical shapes is particularly preferable because thermal stress is less likely to be applied and gas sealing is easy.

The porosity of the porous sintered body is preferably 5 to 40%. When this is used as an air electrode material for SOFC, the porosity is preferably 15 to 40%, and more preferably 25 to 35%. In this case, by setting the porosity of the air electrode to 15% or more, the gas diffusion resistance is reduced, and by setting the porosity to 40% or less, it is possible to secure some strength.

Hereinafter, more specific experimental results will be described. (Production of Porous Sintered Material) First, La _0.80 Sr _0.20
A porous sintered body material made of MnO ₃ and having a porosity of 25% was produced. Each powder of La ₂ O ₃ , SrCO ₃ , and Mn ₃ O ₄ was used, and a predetermined amount of starting material powder was weighed and mixed so that the composition ratio was obtained. This mixed powder was subjected to 1 tf / cm ² by a cold isostatic press method.
Molding was performed under the pressure of 1 to prepare a molded body. This molded body was heat-treated in the air at 1500 ° C. for 15 hours to _obtain La _0.80 Sr.
A composite oxide having a composition of _0.20 MnO ₃ was synthesized.

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 , and a length of 100 m.
m, a width of 100 mm, and a thickness of 10 mm were produced, and this flat plate-shaped body was fired at 1300 ° C to 1600 ° C for 5 hours. From this flat plate-shaped sintered body, length 30 mm, width 30
A porous sintered body material having a thickness of 3 mm and a thickness of 3 mm was cut out.

(Production of Sample Nos. 1 to 8) Each aqueous solution shown in Table 1 was produced. Distilled water was used as the solvent, and the solutes shown in Table 1 were dissolved at the ratios shown in Table 1.

[0063]

[Table 1]

Next, the above-mentioned porous sintered body material is immersed in each aqueous solution for 5 minutes to allow the aqueous solution to penetrate into the open pores of the porous sintered body material, and then the porous sintered body material is heated to 120 °. It was dried in the air of C to precipitate solute crystals inside the pores. Then, the porous sintered body material was heat-treated in air at 1400 ° C. for 4 hours to produce a porous sintered body in which each metal atom was diffused on the surface of the pores.

For each example, the porous sintered body was cut, the cut surface was polished, and a microstructure photograph of the polished surface was taken by a scanning electron microscope photograph. Here, sample number 3 in Table 1
3 shows a scanning electron micrograph of the cross section in the case of FIG.
Shown in. 1 is a cross-sectional view for explaining the microstructure of the cross section of the porous sintered body material corresponding to the microstructure of FIG. 3, and FIG. 2 is for explaining the microstructure of FIG. 4 is a cross-sectional view and corresponds to the state of each pore, surface layer, and inner layer in FIG. 3. As can be seen from FIG. 2 and FIG. 3, each metal atom diffuses on the peripheral surface of the pore 2, and the surface layer 4 in which the content ratio of these metal atoms is larger than the average substitution metal atom is near the surface of the pore 2. Has been formed.

The inventor of the present invention has made the EPM of the porous sintered body of each sample number around the surface layer 4 in which the metal is diffused.
Line analysis was performed by A, and the thickness and average composition of the surface layer 4 were measured. The results are shown in Table 2.

[0067]

[Table 2]

As can be seen from Table 2, in sample numbers 1 to 8, the thickness of the surface layer is in the range of 0.2 to 2.1 μm. The total content of the substituted metal atoms was 26% in Sample No. 1, 26% in Sample No. 2, 27% in Sample No. 3, and 29% in Sample No. 4. And sample number 5
In sample No. 6 and 3 in Sample No. 6
It was 0%, 31% in the sample number 7, and 33% in the sample number 8.

(Production of Sample Nos. 9 to 15) As described in the above section (Production of Porous Sintered Material),
Sample No. 9 was manufactured. Further, similarly to this, Table 3
A porous sintered body having each composition shown in was produced. A porous sintered body of each composition was manufactured by changing the mixing ratio of the raw material powders.

[0070]

[Table 3]

(Method for measuring characteristics of porous sintered body) Table 2,
The following measurements were performed for each porous sintered body in Table 3.
First, the electrical conductivity of each sample number at 1000 ° C. was evaluated. This measurement was performed in the air at 1000 ° C. by the DC four-terminal method. For each sample number, 2
The average coefficient of linear thermal expansion between 5 ° C and 1000 ° C was measured.

Next, each sample was heated to 600 ° C. at a rate of 200 ° C./hour in the atmosphere, and then heat cycled between 600 ° C. and 1000 ° C. at a temperature increase / decrease rate of 200 ° C./hour for 10 times. And cooled to room temperature. At this time, in each heat cycle, a constant temperature was maintained for 30 minutes at 600 ° C. and 1000 ° C., respectively. Then, the dimension of each sample was measured using a micrometer, and the dimensional shrinkage before and after the thermal cycle was calculated.

The creep of each sample number is 1000 °
Measured at C. For each sample number, a test cell was manufactured, and after the initial thermal cycle was performed 10 times,
Also, the amount of power generation (W / cm ² ) was measured after the heat cycle was performed 100 times.

First, 8 mol yttria-stabilized zirconia powder was sprayed by a plasma spraying method on the surface of each plate-shaped sample number having dimensions of 30 mm in length, 30 mm in width, and 3 mm in thickness, and the thickness was 50 μm and the area was 9 square cm. A solid electrolyte membrane was formed. Next, a platinum paste was screen-printed on this solid electrolyte membrane and heat-treated in air at 1000 ° C. for 60 minutes to form a platinum fuel electrode.

When measuring the amount of power generation, the device schematically shown in FIG. 4 was used. The alumina base 15 was installed in the silica glass tube 12, and the unit cell 16 was fixed to the alumina base 15. A glass seal 20 hermetically seals between the side surface of the unit cell 16 and the alumina base 15. A mesh 17 made of platinum is brought into contact with each of the air electrode side and the fuel electrode side of the unit cell 16, and the mesh 17 is connected to a platinum lead wire 18
Connected to. Install the alumina pipe 13 on the air electrode side,
The open end of the alumina pipe 13 was opposed to the air electrode.
Further, the alumina pipe 14 was installed on the fuel electrode side, and the open end of the alumina pipe 14 was opposed to the fuel electrode.

As the fuel gas, hydrogen at 1 atm was flown to the platinum fuel electrode side at a flow rate of 2 liters per minute as shown by arrow B.
Air of 1 atm as an oxidizing gas was flowed to the air electrode side (the porous sintered body side) at a flow rate of 2 liters per minute as shown by arrow A. The temperature around the unit cell was controlled by the heater 11.

First, immediately after the unit cell was manufactured, the amount of power generation was measured and displayed at the "initial" locations in Tables 4 and 5. Next, Tables 4 and 5 show the amounts of power generation after the above-mentioned heat cycle was applied 10 times and 100 times, respectively. These values were compared with the initial power generation amount and the decrease in power generation amount was measured to evaluate the life of the single cell. The amount of power generation per unit area was calculated from the power generation current when the power generation voltage was 0.7V. Table 4 shows sample numbers 9 to 15 of Comparative Example.
The measurement results are shown in Table 5, and Table 5 shows sample numbers 1 to 1 of the present invention.
8 shows the measurement results of 8.

[0078]

[Table 4]

[0079]

[Table 5]

Samples Nos. 9 and 10 had a large dimensional shrinkage due to the heat cycle, so the initial power generation amount was. 021W / cm
^Although it is ² , the power generation amount decreases in 10 cycles and it is destroyed in 100 cycles. Sample number 11 is A site 3
This is an example in which 0% is replaced by strontium, and the dimensional shrinkage due to the thermal cycle is suppressed by this, but the average linear thermal expansion coefficient greatly exceeds 11.0 × 10 ^-6 / ° C, and the creep is Since it becomes large, it is destroyed after 10 cycles. Further, since the electric conductivity of the air electrode is also small, the amount of power generation in the initial stage is also small.

Sample No. 12 is an example in which 10% of the B site was replaced with cobalt, but the average linear thermal expansion coefficient and the creep characteristics were also deteriorated, and as a result, the power generation amount decreased after 100 cycles. To be Sample No. 13 is an example in which 10% of the B site was replaced with nickel, but since the electric conductivity was small, the initial power generation amount was low,
Moreover, since the creep characteristic is deteriorated, the amount of power generation is decreased after 100 cycles.

Sample No. 14 is an example in which 10% of the B site was replaced with aluminum. However, since the electric conductivity was small, the initial power generation amount was low, and the average linear thermal expansion coefficient and creep characteristics were low. Is deteriorated, so it is destroyed after 100 cycles. Sample No. 15 is an example in which 10% of the B site was replaced with magnesium, but the electrical conductivity was low, so the initial amount of power generation was low, and the average linear thermal expansion coefficient and creep characteristics were poor. Therefore, it is destroyed after 100 cycles.

Sample Nos. 1, 2, and 3 are in the inner layer,
In this example, the A site is replaced by calcium in addition to strontium. According to these examples,
First, since the electric conductivity of the porous sintered body is improved (that is, the electric resistance is lowered), the initial power generation amount is improved to 0.27 W / cm ² . Moreover, the dimensional shrinkage due to the heat cycle is largely suppressed, the average linear thermal expansion coefficient hardly increases, and the creep characteristics are good, so that the power generation amount does not decrease even after 100 cycles.

Sample No. 4 is an example in which 29% of A sites in the inner layer are replaced by strontium. Also in this example, it is possible to obtain substantially the same operational effects as the sample numbers 1, 2, and 3.

Sample Nos. 5, 6, 7, and 8 are examples in which the B site is replaced by magnesium, cobalt, nickel, and aluminum in the inner layer. In each of the examples, the dimensional shrinkage due to the heat cycle is significantly suppressed as compared with the sample numbers 9 and 10. Moreover, the average coefficient of linear thermal expansion is almost the same as that of sample numbers 9 and 10, and the creep characteristics are not deteriorated. Therefore, the amount of power generation hardly decreases even after 100 cycles.

In particular, in comparison with Sample Nos. 13, 14, and 15 substituted with nickel, aluminum, or magnesium, in each of these comparative examples, the initial electric power generation amount decreased due to the increase in electric resistance. Even if the same substituted metal atom is used, according to the sample numbers 5, 7, and 8, the electrical resistance of the porous sintered body is much smaller, and is almost the same as the sample numbers 9 and 10. Therefore,
When these substituted metal atoms are used, the electric conductivity is improved and the power generation amount is increased.

Furthermore, the present inventors have used metal alkoxides, hydroxide sol colloids, oxalates, carbonates, and metal fine particle colloids as the solutes of the aqueous solutions shown in Table 1 in the above-mentioned porous sintered body, An experiment was conducted. As a result, as described above, as described above, it is possible to obtain the effects of reducing the dimensional shrinkage due to the heat cycle, improving the creep characteristics, and reducing the average linear thermal expansion coefficient.

[0088]

As described above, according to the present invention, the physical properties of the porous sintered body can be controlled by controlling the composition of the porous sintered body, and various requirements for the porous sintered body can be controlled. Can be satisfied.

[Brief description of drawings]

FIG. 1 is a cross-sectional view for explaining a microstructure of ceramics in a porous sintered body material.

FIG. 2 is a cross-sectional view for explaining a state in which a substitution metal atom is diffused near the surface of pores 2 of a porous sintered body to form a surface layer 4 having a relatively large substitution metal atom content rate. .

FIG. 3 is a scanning electron micrograph showing a ceramic structure of a porous sintered body produced in an example of the present invention.

FIG. 4 is a cross-sectional view schematically showing a device for power generation test of a single cell used in an example of the present invention.

[Explanation of sign]

1 Porous sintered body material 2 Porosity 3 Inner layer
4 Surface layer 16 Test cell A Direction of flowing oxidizing gas B Direction of flowing fuel gas

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication H01M 4/88 T

Claims (10)

[Claims] 1. A porous sintered body composed of a perovskite type complex oxide, wherein the A site of the complex oxide contains one or more main metal atoms selected from the group consisting of rare earth atoms and yttrium. And the manganese is contained in the B site of the complex oxide, and the complex oxide is selected from the group consisting of calcium, strontium, aluminum, cobalt, magnesium, nickel, chromium, copper, iron, titanium and zinc. One or more selected substitution metal atoms are contained, and in the vicinity of the surface of the pores of the porous sintered body, a surface layer having a relatively high content ratio of the substitution metal atoms is present, and this surface A porous sintered body, wherein an inner layer having a relatively low content ratio of the substituted metal atom is present inside the layer. 2. The total content of the substituted metal atoms in each site in the inner layer is 5% or more and 20% or less, and the total content of the substituted metal atoms in each site in the surface layer is Is 25% or more, the porous sintered body according to claim 1. 3. The A site of the composite oxide contains one or more substituted metal atoms selected from the group consisting of calcium and strontium, and the B site of the composite oxide is occupied by manganese. The porous sintered body according to claim 2, characterized in that 4. The A site of the composite oxide contains one or more first substitution metal atoms selected from the group consisting of calcium and strontium, and the B site of the composite oxide contains aluminum, The porous sintered body according to claim 2, wherein the porous sintered body contains at least one second substituted metal atom selected from the group consisting of cobalt, magnesium, nickel, chromium, copper, iron, titanium and zinc. body. 5. The A site of the composite oxide contains two or more kinds of the main metal atoms and one or more substituted metal atoms selected from the group consisting of calcium and strontium. The porous sintered body according to claim 2, which is characterized. 6. The A site of the composite oxide contains two or more kinds of the main metal atoms, and contains one or more first substituted metal atoms selected from the group consisting of calcium and strontium. And that the B site of the composite oxide contains at least one second substituted metal atom selected from the group consisting of aluminum, cobalt, magnesium, nickel, chromium, copper, iron, titanium and zinc. The porous sintered body according to claim 2, which is characterized. 7. The content ratio of one or more substitutional metal atoms selected from the group consisting of calcium, strontium, aluminum, cobalt, magnesium, nickel and chromium in the surface layer is relatively large. Item 7. A porous sintered body according to any one of items 1 to 6. 8. A power-generating article having a heat-resistant electrode made of the porous sintered body according to claim 1. 9. The power generation article according to claim 8, wherein the power generation article is a solid oxide fuel cell, and the heat-resistant electrode is an air electrode of the solid electrolyte fuel cell. 10. A porous sintered body material comprising a perovskite type complex oxide, wherein at least one main metal atom selected from the group consisting of rare earth atoms and yttrium is present at the A site of the complex oxide. A porous sintered body material containing B, which contains manganese at the B site of the composite oxide, is manufactured, and the porous sintered body material is used to produce calcium, strontium, aluminum, cobalt, magnesium, nickel, Chromium, copper, iron, titanium and zinc are immersed in a liquid containing a compound of one or more substituted metal atoms selected from the group consisting of zinc and the liquid is made to adhere to the inside of the pores of the porous sintered body material. By depositing this compound in the pores and then heat-treating this porous sintered body material, in the vicinity of the surface of the pores of the porous sintered body,
A method for producing a porous sintered body, which comprises forming a surface layer having a relatively high content ratio of the substituted metal atom.