JP2015201440A - Composite oxide powder for fuel battery air electrode, manufacturing method for the same, fuel battery air electrode and fuel battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a composite oxide powder for a fuel battery air electrode that has excellent air permeability, provides uniform gas flow and forms many three-layer interfaces efficiently at a stage that a sintered body as an air electrode of a fuel battery is formed, thereby increasing the power generation efficiency and exerting high electrical conductivity, a manufacturing method for the composite oxide powder, and an air electrode and a fuel battery that use the composite oxide powder for a fuel battery air electrode.SOLUTION: To provide a composite oxide powder for a fuel battery air electrode that has excellent air permeability, provides uniform gas flow and forms many three-layer interfaces efficiently at a stage that a sintered body as an air electrode of a fuel battery is formed, thereby increasing the power generation efficiency and exerting high electrical conductivity, a manufacturing method for the composite oxide powder, and an air electrode and a fuel battery that use the composite oxide powder for a fuel battery air electrode. Composite oxide powder for a fuel battery air electrode is composite oxide represented by a general formula of ABO(A element is one or more elements selected from the group consisting of La, Sr and Ca, and B element is one or more elements selected from the group consisting of Mn, Co, Fe and Ni), and circularity ranges from not less than 1.0 to not more than 1.5.

Description

  The present invention relates to a composite oxide powder for a fuel cell air electrode, a method for producing the same, and the fuel cell, preferably used for an air electrode of a solid oxide fuel cell (may be described as “SOFC” in the present invention). The present invention relates to a fuel cell air electrode and a fuel cell using a composite oxide powder for an air electrode.

The SOFC air electrode will be briefly described with reference to a general SOFC as an example.
The SOFC is generally composed of a cell composed of a porous support tube, an air electrode, a solid electrolyte, a fuel electrode, and an interconnector. Then, air (oxygen) is allowed to flow through the air electrode layer, and fuel gas is allowed to flow toward the fuel electrode layer, thereby causing chemical combustion in the solid electrolyte layer and generating power between the air electrode and the fuel electrode. Is done.

In Patent Literature 1, as a material for the air electrode described above, 0.1 to 5 μm of fine powder 0.5 to 40 parts by weight is mixed with 100 parts by weight of coarse powder of particle size distribution 5 to 150 μm, It has been proposed that a LaSrMnO ₃ sintered body having air permeability, strength, and conductivity, which are necessary characteristics of an air electrode, can be obtained by molding and sintering.
Further, Patent Document 2 proposes a manufacturing method for spray-drying and firing a metal salt solution as a method for manufacturing coarse powder that is a material for an air electrode.

Japanese Patent Laid-Open No. 7-215764 JP 2012-138256 A

  As characteristics to be satisfied by the air electrode of the fuel cell, chemical stability, air permeability, conductivity, high catalytic action, mechanical characteristics, raw material cost, and the like can be considered. As a result of research and examination, the present inventors have come up with the idea that further improvement in air permeability and conductivity is essential.

The problems found by the present inventors will be specifically described.
The first problem is that the air electrode powder having a particle size of about 20 μm manufactured by a conventional technique such as a spray drying method of a molten metal salt solution is an aggregate of fine primary particles of submicron to several microns. The particle shape is uneven. For this reason, in the stage which became the sintered compact which is an air electrode, it is that the distribution of the hole required for ventilation | gas_flow becomes non-uniform | heterogenous. As a result of the non-uniform distribution of the pores, the gas flow between the particles in the air electrode becomes non-uniform. Furthermore, since the three-layer interface (where the air electrode, the electrolyte, and the gas phase are in contact with each other) that is a uniform pore between the particles and the electrolyte layer is not efficiently formed, power generation efficiency is reduced. It is to do.

  The second problem is that the coarse powder, which is a raw material of the air electrode manufactured by the conventional technique, has found that a large number of excessive pores exist inside the particles. Since there are a large number of the excess pores, even when the sintered body is the air electrode, the pores still exist, the current path is hindered, and the conductivity of the air electrode is reduced. is there.

  The present invention has been made under the above-described circumstances, and the problem to be solved is that the gas flow is uniform and the gas flow becomes uniform at the stage where the sintered body is the air electrode of the fuel cell. , A fuel cell air electrode composite oxide powder that is excellent in power generation efficiency and exhibits high conductivity by efficiently forming a large number of three-layer interfaces, and a method for producing the same, and the fuel cell air electrode composite oxide An object of the present invention is to provide a fuel cell air electrode and a fuel cell using a material powder.

In order to solve the above-mentioned problems, the present inventors have conducted intensive research.
Then, in order to realize the uniform gas flow in the air electrode, which is the first problem described above, it is thought that the roundness of the particles constituting the composite oxide powder for a fuel cell air electrode may be increased. did. That is, by increasing the roundness of the particles constituting the composite oxide powder for a fuel cell air electrode, when these particles are packed most closely, between the particles and between the particles and the electrolyte layer It is conceived that a large number of three-layer interfaces, which are uniform pores, are efficiently formed.
Moreover, in order to avoid the presence of excessive voids inside the particles in the air electrode raw material coarse powder, which is the second problem described above, the filling rate inside the particles may be 80% or more. It has been conceived.

That is, the first invention for solving the above-mentioned problem is
A composite oxide represented by the general formula ABO ₃ (where A element is one or more elements selected from La, Sr, and Ca, and B element is one or more elements selected from Mn, Co, Fe, and Ni) Element)
The composite oxide powder for a fuel cell air electrode has a roundness of 1.0 to 1.5.
The second invention is
A composite oxide represented by the general formula ABO ₃ (where A element is one or more elements selected from La, Sr, and Ca, and B element is one or more elements selected from Mn, Co, Fe, and Ni) Element)
The composite oxide powder for a fuel cell air electrode has a circularity of 1.0 or more and 1.5 or less.
The third invention is
The composite oxide powder for a fuel cell air electrode according to the first or second invention, wherein the BET value is 0.5 m ² / g or less.
The fourth invention is:
The composite oxide powder for a fuel cell air electrode according to any one of the first to third aspects, wherein the cumulative particle size D50 is 20 μm or more and 30 μm or less.
The fifth invention is:
A composite oxide represented by the general formula ABO ₃ (where A element is one or more elements selected from La, Sr, and Ca, and B element is one or more elements selected from Mn, Co, and Fe) Yes, and
A composite oxide powder for a fuel cell air electrode having a roundness of 1.0 to 1.5 and a cumulative particle size D50 of 20 μm to 30 μm.
The sixth invention is:
A composite oxide represented by the general formula ABO ₃ (where A element is one or more elements selected from La, Sr, and Ca, and B element is one or more elements selected from Mn, Co, and Fe) Yes, and
A composite oxide powder for a fuel cell air electrode, having a circularity of 1.0 to 1.5 and a cumulative particle size D50 of 20 μm to 30 μm.
The seventh invention
The composite oxide powder for a fuel cell air electrode according to the fifth or sixth invention, wherein the BET value is 0.5 m ² / g or less.
The eighth invention
The composite oxide powder for a fuel cell air electrode according to any one of the first to seventh inventions,
The composite oxide powder for a fuel cell air electrode is characterized in that the filling rate inside the particles contained in the powder is 80% or more.
The ninth invention
When the raw material slurry is spray-dried to obtain a granulated powder, and the granulated powder is fired and pulverized to obtain a composite oxide powder for a fuel cell air electrode, the solid content concentration of the powder in the raw material slurry is determined. A method for producing a composite oxide powder for a fuel cell air electrode, characterized in that it is 25% by mass or more, the cumulative particle diameter D50 of the raw slurry is 0.8 μm or more and 3.0 μm or less, and firing is performed in an open system. is there.
The tenth invention is
The method for producing a composite oxide powder for a fuel cell air electrode according to the ninth aspect, wherein the solid content concentration of the powder in the raw slurry is 50% by mass or more.
The eleventh invention is
A fuel cell air electrode comprising the composite oxide powder for a fuel cell air electrode according to any one of the first to eighth inventions.
The twelfth invention
A fuel cell comprising the composite oxide powder for a fuel cell air electrode according to any one of the first to eighth inventions.

  According to the present invention, since a large number of three-phase interfaces that are uniform pores can be generated between the composite oxide powder for a fuel cell air electrode and the electrolyte layer, an air electrode with high power generation efficiency can be manufactured. . Furthermore, according to the present invention, since the composite oxide powder for a fuel cell air electrode has high conductivity, an air electrode with high power generation efficiency can be manufactured.

It is the figure which described typically the case where the air electrode was seen from the top and the case where the cross section was seen. It is the SEM image and cross-sectional image of the complex oxide powder for fuel cell air electrodes which concern on an Example.

The composite oxide powder for a fuel cell air electrode according to the present invention (hereinafter sometimes abbreviated as “powder” in the present specification) and the particles constituting the powder will be described.
The composite oxide powder for a fuel cell air electrode according to the present invention is a composite oxide represented by the general formula ABO ₃ (provided that the A element is one or more elements selected from La, Sr, and Ca, and the B element) Is one or more elements selected from Mn, Co, Fe, and Ni).
The particles constituting the powder are spherical particles having a cumulative particle diameter D50 of 20 μm or more and 30 μm or less. The degree of sphere in the spherical particles is 1.0 or more and 1.5 or less when expressed in roundness, and 1.0 or more and 1.5 or less when expressed in circularity.
And the BET value of the said particle | grain is 0.5 m < ² > / g or less, and the porosity inside a particle | grain is 20 mass% or less (namely, the filling factor inside a particle | grain is 80% or more).

  In the air electrode of a fuel cell, oxygen moves through the air holes in the air electrode, comes into contact with the electrolyte, receives electrons and becomes oxygen ions, and the reaction proceeds. Here, the reaction proceeds at a so-called three-phase interface in which three phases of an air electrode, an electrolyte, and a gas phase are in contact. Here, the present inventors have studied to increase the power generation efficiency of the fuel cell by increasing the number of the three-layer interfaces. The inventors have conceived that the particles constituting the air electrode only have to have high roundness (circularity).

The configuration will be described with reference to the drawings.
FIG. 1 is a diagram schematically illustrating a portion of an air electrode where a particle constituting the air electrode is in contact with an electrolyte, when viewed from above and when viewed from a cross section.
That is, when the particles constituting the air electrode have a spherical shape with high roundness (circularity), the particles are uniformly present in a finely packed shape as shown in (A). Then, as shown in (B), vacancies are uniformly vacant between the particles, and the flow of oxygen becomes uniform, and at the same time, a large number of three-layer interfaces are efficiently formed, thereby increasing the power generation efficiency.
On the other hand, when the shape of the particles constituting the air electrode is, for example, a rectangular parallelepiped other than a sphere, a portion where no void exists and a large void depending on the manner of contact between the particles as shown in (C) Are formed in excess. As a result, as shown in (D), as the oxygen flow becomes non-uniform, the three-phase interface is reduced and the power generation efficiency is reduced.

According to the study by the present inventors, when the roundness or circularity is less than 1.5, the power generation efficiency is maintained. This is considered to be because the shape of the particles was not greatly deformed from the spherical shape.
When the particles were spherical and the BET value was less than 0.5 m ² / g, the power generation efficiency was maintained. This is presumably because the pores of the air electrode were uniformly generated because the shape of the particle surface was not uneven but smooth.
On the other hand, the electrical conductivity was maintained when the filling rate inside the particles was 80% or more. This is presumably because there were no vacancies inside the particles and the current path was good.

Hereinafter, the method for producing a composite oxide powder for a fuel cell air electrode according to the present invention will be described in detail.
(1) Wet pulverization As a raw material of the composite oxide powder for a fuel cell air electrode according to the present invention, a raw material slurry is obtained by using water insoluble salts of element A and element B. This is because the granulated powder is produced by spray drying in the subsequent step.
The raw material salt of element A and element B can be used without particular limitation as long as it is an insoluble salt in water, but it is a salt from which elements other than the composite oxide are eliminated as a gas in the calcination step. This is desirable from the viewpoint of reducing impurities. Specifically, oxides and carbonates of element A and element B are preferable examples. In addition, what is necessary is just to select a raw material so that it may become 100 ppm or less by weight about the impurity in each raw material salt.
Specifically, predetermined amounts of the A element raw material and the B element raw material are weighed and mixed with pure water to obtain a slurry. If the solid content concentration of the powder in the raw material slurry is 25% by mass or more, a composite oxide powder for a fuel cell air electrode having good characteristics could be obtained. Furthermore, from the viewpoint of drying efficiency, the solid content concentration of the powder in the raw slurry is desirably 40% by mass or more. However, when the solid content concentration of the powder in the raw material slurry is 50% by mass or more, the viscosity of the slurry becomes high and it becomes difficult to pulverize the raw material. Therefore, when the solid content concentration of the powder in the raw slurry is 50% by mass or more, it is desirable to add a dispersant to the raw slurry. As the dispersant, ammonium polyacrylate or the like can be preferably used.

Wet grinding is performed with a bead mill. The material of the grinding media can be used without limitation as long as it has high mechanical strength. Specifically, Zr beads having high strength are preferable. Further, Zr has a larger allowable range even when contamination occurs, compared to an element such as Fe. Therefore, Zr beads are preferable from the viewpoint of contamination. It is preferable that the bead diameter is φ2.0 mm or less because the grinding efficiency can be secured.
The raw slurry after the wet pulverization is preferable if the cumulative particle diameter D50 is less than 5 μm, since no different phases other than the composite oxide phase represented by the general formula ABO ₃ are generated in the firing described later. If D50 of the particle size distribution of the raw material slurry is 5.0 μm or less, the composition deviation due to the site in the granulated product is small, so the generation of heterogeneous phases is suppressed and the particle shape distortion is reduced. The cumulative particle size D50 is preferably as small as possible, but if the particle size is 0.8 μm or more, the increase in contamination can be suppressed. From this viewpoint, D50 is preferably 0.8 μm or more and 3.0 μm or less. Furthermore, from the viewpoint of increasing the filling rate inside the particles constituting the powder according to the present invention described above, it is more preferable that 0.8 ≦ D50 <1.2 μm and a particle size distribution of a single distribution.

(2) Drying and granulation The raw material slurry after the wet pulverization is dried and granulated.
Spray drying is suitable for drying the raw slurry and granulating it into a spherical shape. And it is preferable to use a spray dryer from a viewpoint of obtaining spherical granulated powder. There are nozzle type and disk type, but the particle type is large to obtain spherical particles, and the disk type is preferable, and the higher the rotation speed of the atomizer disk in the spray dryer, the more the slurry is sheared and granulated. Since the operation is uniform, the shape of the particles tends to be spherical without distortion.
The number of revolutions of the atomizer disk is preferably 20000 rpm or more, although it depends on the speed at which the slurry is supplied, the air flow rate of the dryer, and the chamber capacity. The hot air temperature for drying is desirably a temperature at which moisture does not remain in the granulated particles after spray drying. Specifically, the inlet temperature is preferably 150 to 200 ° C., and the outlet temperature is preferably 60 ° C. or higher.
The feed rate of the raw slurry varies depending on the capacity of the apparatus. For example, in the case of an apparatus having a drying chamber capacity of about 1 m ³ , the shape of the granulated particles can be maintained and the productivity can be secured by setting the feed rate of the raw slurry to 5 to 30 kg / h. To preferred.

(3) Firing The firing temperature of the granulated particles is 1200 ° C. to 1600 from the viewpoint of increasing the filling rate inside the particles constituting the composite oxide powder for a fuel cell air electrode and increasing the conductivity of the particles. ° C is desirable. In particular, the firing temperature is preferably 1300 ° C. or higher from the viewpoint of increasing the electrical conductivity. Further, it is preferable that the firing temperature is 1500 ° C. or lower because the granulated product after firing is easy to be pulverized.
During firing, the rate of temperature rise is preferably 10 ° C./min or less, and the atmosphere may be air. Then, the inside of the furnace and the firing container is opened, and the temperature is raised while removing the gas components generated from the raw material salts of the A element and B element. In the present invention, the open system refers to a reaction system in which the inside of the furnace or the baking vessel is not sealed and the atmosphere gas can flow in and out.
This is because, when the granulated product is fired in a closed system in which the inflow and outflow of gas are blocked, the gas component generated from the raw material is filled in the system, and as a result, the particle grows while breaking its shape, so that the particle shape is This is because it may be distorted. On the other hand, if the granulated product is calcined in an open system, the particles constituting the composite oxide powder for a fuel cell air electrode will not grow while breaking the spherical shape or forming irregularities on the surface. Because.

(4) Granulation By pulverizing the granulated product after firing, the composite oxide powder for a fuel cell air electrode according to the present invention is obtained. Care should be taken not to impair the spherical shape of the particles during the pulverization.
From this viewpoint, a sample mill, a Henschel mixer, a pin mill, or the like is used for the granulation, and the granulation is performed under conditions that do not impair the particle spherical shape. Specifically, for example, if a Henschel mixer having a capacity of 20 L is used, the rotational speed is preferably 2100 rpm or less. This is because if the rotation speed is 2100 rpm or less, the spherical shape of the particles is not impaired.
As described above, the powder according to the present invention can be obtained.

Hereinafter, the evaluation method of the composite oxide powder for a fuel cell air electrode according to the present invention will be described in detail.
(5) Roundness / Circularity of Particles The roundness / circularity of the particles constituting the composite oxide powder for a fuel cell air electrode according to the present invention can be determined using an SEM image of the particles obtained from image analysis software (for example, Measurement and evaluation can be performed using Image-Pro Plus 7.0J, manufactured by Roper Industries, USA.
here,
Roundness = L ^ 2 / (S * 4π)
Circularity = (R ^ 2 / S) * (π / 4)
(However, L: circumference length, S: area of target particle by image analysis, R: maximum ferret diameter).
In both roundness and circularity, the closer the value is to 1, the more spherical it is, and the larger the value, the more irregular it is.
In addition, if the magnification of 1000 times is used for the SEM image, about 50 particles are selected, the average value of L, S, and R values is obtained, and further, the roundness and circularity values are obtained. good.

(6) Filling rate inside the particles SEM image analysis was used to measure the filling rate inside the particles constituting the composite oxide powder for a fuel cell air electrode according to the present invention.
<1> The powder according to Examples 1 to 3 is dispersed in a thermosetting resin, and the resin is thermoset. The heat-cured resin was cut using a cross section polisher to expose the cross section of the particles constituting the powder.
<2> Take an SEM image of the exposed particle cross section. The photographed SEM image was analyzed using image analysis software (for example, Nippon Roper Image-Pro Plus 7.0J), and the filling rate inside the particles was measured. Then, from the difference in contrast between the particle portion and the pore portion, the filling ratio inside the particle = (particle portion area−pore portion area) / (particle portion area) was defined.
In addition, what is necessary is just to obtain | require an average value by analyzing about 50 particle | grains using a 1000 times magnification SEM image.

(7) Conductivity The conductivity of the composite oxide powder for fuel cell air electrode according to the present invention is measured by pelletizing the powder and conducting by using a resistivity meter (MCP-T610 manufactured by Mitsubishi Analytech Co., Ltd.). The rate can be measured.
Specifically, the pellet according to the present invention is pressed using a pellet forming press to form a pellet. The molded pellets are heated from 25 ° C. to 1150 ° C. at 5 ° C./min, held at 1150 ° C. for 4 hours, and then naturally cooled to obtain pellets for conductivity measurement.
Using a resistivity meter, the terminal was applied to the central portion of the pellet cylinder for measuring conductivity, and the conductivity (S / cm) was measured. The measurement was performed about 10 times to obtain an average value, and the average value was taken as a measurement value.

Hereinafter, the present invention will be described more specifically with reference to examples.
(Example 1)
(1) Preparation of raw material slurry A bead mill (capacity: 1.2 liters) was used for preparation of the raw material slurry.
_{<1> La x Sr y Ca} z Mn w O 3 ( where, x = 0.49, y = 0.24 , z = 0.25, w = 1.03) for the powder production with the composition, La the ₂ O _{3 2966g, 1360g} of SrCO _3, the CaCO ₃ 938 g, the MnCO ₃ 4723g, pure water 4280G, a dispersant ammonium polyacrylate to 500g weighed.
<2> 3100 g of ZrO ₂ beads having a diameter of 1.75 mm are charged in a bead mill vessel.
<3> Pure water and a dispersant are put into a buffer tank and mixed to obtain a dispersant aqueous solution. And the said dispersing agent aqueous solution is circulated to a bead mill using a pump.
<4> While stirring the dispersant aqueous solution in the buffer tank at 400 rpm, the above-mentioned weighed La ₂ O ₃ , SrCO ₃ , CaCO ₃ , and MnCO ₃ are put therein.
<5> The bead mill was rotated at 1000 rpm, and La ₂ O ₃ , SrCO ₃ , CaCO ₃ , and MnCO ₃ charged were pulverized for 80 minutes to prepare a raw material slurry.
The obtained raw material slurry had a single particle size distribution and a cumulative particle size D50 of 1.17 μm.

(2) Drying and granulation A spray dryer was used for spray drying.
<1> Pure water was added to the raw material slurry, and the solid content concentration of the powder in the raw material slurry was adjusted to 63% by mass.
<2> Spray drying of the raw material slurry was carried out at a spray dryer disk rotation speed of 25000 rpm, a hot air temperature for drying at an inlet temperature of 150 ° C., an outlet temperature of 75 ° C., and a raw material slurry supply rate of 9 kg / h. Grains were obtained.
The obtained granulated product had a cumulative particle size D50 of 39 μm.

(3) Firing A crucible was used for firing.
<1> 230 g of the granulated product was charged into a cylindrical crucible (diameter 12 cm, height 5 cm). And after raising the temperature from 25 ° C. to 1300 ° C. at 4.25 ° C./min, further raising the temperature from 1300 ° C. to 1450 ° C. at 1.5 ° C./min, and then holding at 1450 ° C. for 4 hours, The temperature dropped naturally.

(4) Granulation A Henschel mixer was used for granulation.
<1> 2000 g of the calcined powder was charged into a Henschel mixer.
The rotational speed was set to 1400 rpm and pulverization was performed for 60 seconds to obtain a composite oxide powder for a fuel cell air electrode according to Example 1.
Table 1 shows the composition of the powder according to Example 1 and the firing temperature.

  Table 2 shows the D50 particle diameter, roundness, circularity, BET value, filling rate inside the particles, and conductivity of the powders constituting the powder according to Example 1 obtained. In addition, FIG. 2 shows a 1000 times SEM image of the particles and a 1000 times SEM image of the cross section of the particles.

(Example 2)
Example 2 was carried out in the same manner as in Example 1 except that the firing temperature was 1300 ° C., the heating rate was 6.66 ° C./min from 800 ° C. to 3.33 ° C./min from 800 ° C. to 1300 ° C. A composite oxide powder for a fuel cell air electrode was obtained.
Table 1 shows the composition of the powder according to Example 2 and the firing temperature.
Table 2 shows the D50 particle size, roundness, circularity, BET value, filling rate inside the particles, and electrical conductivity of the powder constituting the powder according to Example 2 obtained. In addition, FIG. 2 shows a 1000 times SEM image of the particles and a 1000 times SEM image of the cross section of the particles.

(Example 3)
The composition of the _{powder, La x Sr y Co v Fe} u O 3 ( where, x = 0.61, y = 0.41 , v = 0.20, u = 0.79) to have a composition of the raw material A slurry was prepared, the firing temperature was set to 1300 ° C., the rate of temperature increase was 6.66 ° C./min from 800 ° C., and 3.33 ° C./min from 800 ° C. to 1300 ° C. Thus, a composite oxide powder for a fuel cell air electrode according to Example 3 was obtained.
At this time, Co ₃ O ₄ was used as the Co raw material, and Fe ₂ O ₃ was used as the Fe raw material.
Table 1 shows the composition of the powder according to Example 3 and the firing temperature.
Table 2 shows the cumulative particle diameter D50, roundness, circularity, BET value, filling rate inside the particles, and electrical conductivity of the powder constituting the powder according to Example 3 obtained. .

Example 4
Pure water is added to the raw slurry, the solid content concentration of the powder in the raw slurry is adjusted to 25% by mass, the firing temperature is 1350 ° C., the heating rate is 6.66 ° C./min up to 800 ° C., and from 800 ° C. to 1350 ° C. A composite oxide powder for a fuel cell air electrode according to Example 4 was obtained in the same manner as in Example 1, except that the temperature was 3.33 ° C./min.
Table 1 shows the composition of the powder according to Example 4 and the firing temperature.
Table 2 shows the cumulative particle diameter D50, roundness, circularity, BET value, filling rate inside the particles, and electrical conductivity of the powder constituting the powder according to Example 4 obtained. .

(Example 5)
A raw material slurry is prepared so that the composition of the powder has a composition of La _x Ni _t Fe _u O ₃ (where x = 0.99, t = 0.61, u = 0.40), and into the raw material slurry For a fuel cell air electrode according to Example 5 except that pure water was added, the solid content concentration of the powder in the raw slurry was adjusted to 57 mass%, and the firing temperature was 1430 ° C. A composite oxide powder was obtained.
At this time, NiO was used as the Ni raw material.
Table 1 shows the composition of the powder according to Example 5 and the firing temperature.
Table 2 shows the cumulative particle diameter D50, roundness, circularity, BET value, filling rate inside the particles, and the electrical conductivity of the powder constituting the powder according to Example 5 obtained. .

(Example 6)
Raw material so that the composition of the powder has a composition of La _x Sr _y Ni _t Fe _u O ₃ (where x = 0.50, y = 0.50, t = 0.20, u = 0.81) A slurry was prepared, pure water was added to the raw slurry, the solid content concentration of the powder in the raw slurry was adjusted to 57% by mass, and the firing temperature was 1400 ° C. A composite oxide powder for a fuel cell air electrode according to No. 6 was obtained.
At this time, NiO was used as the Ni raw material.
Table 1 shows the composition of the powder according to Example 6 and the firing temperature.
Table 2 shows the cumulative particle diameter D50, roundness, circularity, BET value, filling rate inside the particles, and electrical conductivity of the powder constituting the powder according to Example 6 obtained. .

(Comparative Example 1)
A composite oxide powder for a fuel cell air electrode according to Comparative Example 1 was obtained in the same manner as in Example 1, except that a cylindrical crucible was covered and fired in a sealed state.
The accumulated particle size D50 of the obtained granulated product according to Comparative Example 1 was 33.0 μm.
Table 1 shows the composition of the powder according to Comparative Example 1 and the firing temperature.
Table 2 shows the D50, roundness, circularity, BET value, and conductivity of the powder constituting the powder of Comparative Example 1 obtained.
In Comparative Example 1, since firing was not performed in an open system, the gas components generated from the raw material salts of element A and element B remained in the crucible without being removed. As a result, since particle growth did not occur uniformly at each part in one particle, the shape of the particle became distorted, and roundness and circularity were considered to be higher than 1.5. .

(Comparative Example 2)
(1) Preparation of Raw Material Slurry A raw material slurry was prepared in the same manner as in Example 1 except that the pulverization time was 5 minutes in the preparation of the raw material slurry.
The obtained raw material slurry had a double particle size distribution and a cumulative particle size D50 of 5.0 μm.
Pure water was added to the raw material slurry, and the solid content concentration of the powder in the raw material slurry was adjusted to 57% by mass. And the complex oxide powder for fuel cell air electrodes which concerns on the comparative example 2 was obtained like Example 1 except the calcination temperature having been 1300 degreeC. And when the complex oxide powder for fuel cell air electrodes according to Comparative Example 2 was observed, it was found that a different phase other than the ABO ₃ phase was also generated, and it was not a single phase of the ABO ₃ phase. .
The cumulative particle diameter D50 of the granulated product according to Comparative Example 2 obtained was 26.0 μm.
Table 1 shows the composition of the powder according to Comparative Example 2 described above and the firing temperature.
Table 2 shows D50 of the particles constituting the powder according to Comparative Example 2 obtained.
The roundness, circularity, BET value, packing density, and conductivity of the powder were not measured because the composite oxide powder for fuel cell air electrode according to Comparative Example 2 was not single-phased.
The powder became a single phase because the D50 of the particle size distribution of the raw slurry was 5.0 μm or more, so that the compositional deviation due to the site in the granulated product increased and a heterogeneous phase was generated. Conceivable.

(Comparative Example 3)
A raw material slurry was prepared and spray-dried in the same manner as in Example 1 except that the solid content concentration of the powder in the raw material slurry was 24% by mass, and a granulated product according to Comparative Example 3 was obtained.
The obtained granulated product according to Comparative Example 3 was a product in which the shape of some of the particles was distorted and did not maintain a spherical shape. Therefore, the test was terminated.
The shape of the granulated particles was distorted because the solid content concentration of the powder in the raw slurry was set low, resulting in increased evaporation of water from the droplets, and the granulated product could not maintain a spherical shape. This is considered to be the reason.

(Summary)
In Examples 1 to 6, D50 of the particles constituting the powder was 20.6 to 29.0 μm, the roundness was 1.19 to 1.35, the circularity was 1.12 to 1.23, and the BET value was 0.1. A composite oxide powder for a fuel cell air electrode satisfying the requirements of the present invention of 078 to 0.304 m ² / g could be obtained. Therefore, if an SOFC air electrode is manufactured using these powders, the flow of gas in the air electrode can be made uniform, and between the particles constituting the powder and between the particles and the electrolyte layer. It is considered that a large number of three-layer interfaces, which are uniform pores, are efficiently formed.

  Moreover, in Examples 1-6, the composite oxide powder for fuel cell air electrodes which satisfy | fills the requirements of this invention that the filling rate of particle | grain inside was 81.2 to 99.3% could be obtained. All of these powders exhibited high conductivity of 47.6 to 171.0 S / cm.

  As described above, according to the present invention, a large number of three-phase interfaces that are uniform pores can be generated between the composite oxide powder for a fuel cell air electrode and the electrolyte layer, and the conductivity of the powder is high. It is considered that an air electrode with high power generation efficiency can be manufactured.

Claims (12)

A composite oxide represented by the general formula ABO ₃ (where A element is one or more elements selected from La, Sr, and Ca, and B element is one or more elements selected from Mn, Co, Fe, and Ni) Element)
A composite oxide powder for a fuel cell air electrode, wherein the roundness is 1.0 or more and 1.5 or less. A composite oxide represented by the general formula ABO ₃ (where A element is one or more elements selected from La, Sr, and Ca, and B element is one or more elements selected from Mn, Co, Fe, and Ni) Element)
A composite oxide powder for a fuel cell air electrode, having a circularity of 1.0 to 1.5. The composite oxide powder for a fuel cell air electrode according to claim 1 or 2, wherein a BET value is 0.5 m ² / g or less.   4. The composite oxide powder for a fuel cell air electrode according to claim 1, wherein the cumulative particle diameter D50 is 20 μm or more and 30 μm or less. A composite oxide represented by the general formula ABO ₃ (where A element is one or more elements selected from La, Sr, and Ca, and B element is one or more elements selected from Mn, Co, and Fe) Yes, and
A composite oxide powder for a fuel cell air electrode, having a roundness of 1.0 to 1.5 and a cumulative particle size D50 of 20 μm to 30 μm. A composite oxide represented by the general formula ABO ₃ (where A element is one or more elements selected from La, Sr, and Ca, and B element is one or more elements selected from Mn, Co, and Fe) Yes, and
A composite oxide powder for a fuel cell air electrode, having a circularity of 1.0 to 1.5 and a cumulative particle size D50 of 20 μm to 30 μm. BET value is 0.5 m < ² > / g or less, The complex oxide powder for fuel cell air electrodes of Claim 5 or 6 characterized by the above-mentioned. A composite oxide powder for a fuel cell air electrode according to any one of claims 1 to 7,
A composite oxide powder for a fuel cell air electrode, wherein a filling ratio of particles inside the powder is 80% or more.   When the raw material slurry is spray-dried to obtain a granulated powder, and the granulated powder is fired and pulverized to obtain a composite oxide powder for a fuel cell air electrode, the solid content concentration of the powder in the raw material slurry is determined. A method for producing a composite oxide powder for a fuel cell air electrode, characterized in that it is 25% by mass or more, the cumulative particle diameter D50 of the raw slurry is 0.8 μm or more and 3.0 μm or less, and firing is performed in an open system.   The method for producing a composite oxide powder for a fuel cell air electrode according to claim 9, wherein the solid content concentration of the powder in the raw slurry is 50 mass% or more.   A fuel cell air electrode comprising the composite oxide powder for a fuel cell air electrode according to any one of claims 1 to 8.   A fuel cell comprising the composite oxide powder for a fuel cell air electrode according to any one of claims 1 to 8.