阅读说明：本技术 固体氧化物型燃料电池空气极用粉体及其制造方法 (Powder for air electrode of solid oxide fuel cell and method for producing same ) 是由 平田宜宽 米田稔 于 2019-08-05 设计创作，主要内容包括：一种固体氧化物型燃料电池空气极用粉体,其是具有用下述通式：A1-(1-x)A2-xBO-(3-δ)(其中,元素A1为选自由La、Sm构成的组中的至少一种,元素A2为选自由Ca、Sr、Ba构成的组中的至少一种,元素B为选自由Mn、Fe、Co、Ni构成的组中的至少一种,0＜x＜1,δ为氧缺位量)所表示的钙钛矿型晶体结构的金属复合氧化物的粉体,对于上述粉体,比表面积为20m～2/g以上,满足(微晶直径/比表面积换算粒径)≥0.3,并且除上述元素A1、上述元素A2、上述元素B及氧以外的元素M的含量以原子换算计为300ppm以下。(A powder for an air electrode of a solid oxide fuel cell, which has the following general formula: a1 1‑x A2 x BO 3‑δ (wherein, the element A1 is at least one selected from the group consisting of La and Sm, the element A2 is at least one selected from the group consisting of Ca, Sr and Ba, the element B is at least one selected from the group consisting of Mn, Fe, Co and Ni, 0 < x < 1, and delta is the oxygen vacancy amount)The powder of a metal composite oxide of (2), wherein the powder has a specific surface area of 20m 2 (crystallite diameter/specific surface area converted particle diameter) of not less than 0.3, and the content of an element M other than the element A1, the element A2, the element B, and oxygen is not more than 300ppm in terms of atoms.)

1. A powder for an air electrode of a solid oxide fuel cell, which is a powder of a metal composite oxide having a perovskite crystal structure represented by the following general formula:

A1_1-xA2_xBO_3-δ

wherein, the element A1 is at least one selected from the group consisting of La and Sm, the element A2 is at least one selected from the group consisting of Ca, Sr and Ba, the element B is at least one selected from the group consisting of Mn, Fe, Co and Ni, x is more than 0 and less than 1, and delta is the oxygen vacancy;

as for the powder, it is preferable that,

the specific surface area is 20m²The ratio of the carbon atoms to the carbon atoms is more than g,

satisfies (crystallite diameter/specific surface area converted particle diameter) of not less than 0.3

The content of the element M other than the element A1, the element A2, the element B and oxygen is 300ppm or less in terms of atoms.

2. The powder according to claim 1, wherein the powder satisfies (crystallite diameter/average particle diameter) 0.05 or more.

3. The powder according to claim 1 or 2, wherein the element A1 is La,

the element a2 is Sr,

the element B is at least 1 of Co and Fe.

4. A method for producing a powder for an air electrode of a solid oxide fuel cell, comprising the steps of:

a preparation step of preparing a metal composite oxide having a perovskite crystal structure represented by the following general formula:

A1_1-xA2_xBO_3-δ

wherein, the element A1 is at least one selected from the group consisting of La and Sm, the element A2 is at least one selected from the group consisting of Ca, Sr and Ba, the element B is at least one selected from the group consisting of Mn, Fe, Co and Ni, x is more than 0 and less than 1, and delta is the oxygen vacancy; and

a grinding step of grinding the metal composite oxide using alumina beads to obtain a specific surface area of 20m²A powder having a particle size of 0.3 or more (crystallite diameter/particle diameter converted to specific surface area).

5. The method for producing a powder according to claim 4, wherein a step of bringing the metal composite oxide to a specific surface area of 2m is provided before the pulverization step²More than or equal to g and less than 20m²A preliminary grinding step of grinding in the form of/g.

6. The method for producing a powder according to claim 4 or 5, wherein the preparation step includes a step of mixing a1 st compound containing the element A1, a2 nd compound containing the element A2, and A3 rd compound containing the element B, and heating the mixture at 1250 ℃ or higher to synthesize the metal composite oxide.

7. The method for producing a powder according to any one of claims 4 to 6, wherein the powder obtained by the pulverization step satisfies a requirement (crystallite diameter/average particle diameter) of 0.05 or more.

8. The method for producing a powder according to any one of claims 4 to 7, wherein the alumina beads have a purity of 99.9 mass% or more.

Technical Field

The present invention relates to a powder for an air electrode constituting a solid oxide fuel cell and a method for producing the same.

Background

In recent years, fuel cells have been attracting attention as clean energy sources. Among them, a Solid Oxide Fuel Cell (SOFC) using a solid oxide having ion conductivity as an electrolyte has excellent power generation efficiency. The SOFC has the working temperature as high as about 800-1000 ℃, and can also utilize heat extraction. Further, since SOFCs can use various fuels such as hydrocarbon and carbon monoxide gas, they can be expected to be widely and effectively used from home to large-scale power generation. SOFCs typically have an air electrode (cathode), a fuel electrode (anode), and an electrolyte layer interposed therebetween.

The air electrode is formed of, for example, a metal composite oxide. The metal composite oxide is synthesized from a mixture of a plurality of raw materials by a citric acid method, a solid phase method, or the like. Patent document 1 teaches a method for synthesizing a metal composite oxide by using a citric acid method. Patent document 2 teaches a method for synthesizing a metal composite oxide by using a solid phase method.

The citric acid method has an advantage that a metal composite oxide having a uniform composition can be obtained on a microscopic level, and has problems of low yield and productivity. The solid phase method is one of industrially excellent production methods because of its simple production process, easy control of composition, and the like.

Documents of the prior art

Patent document

Patent document 1: japanese patent No. 5520210

Patent document 2: japanese laid-open patent publication No. 2009-035447

Disclosure of Invention

Problems to be solved by the invention

The powder for an air electrode is required to be fine (for example, 1 μm or less) in view of improvement of reaction efficiency. Therefore, the synthesized metal composite oxide is generally subjected to a pulverization step. In the pulverizing step, a medium-stirring type micro-pulverizer may be used. In such a micro-pulverizer, the metal composite oxide is pulverized by stirring the metal composite oxide together with a pulverizing medium and causing the metal composite oxide to collide with the pulverizing medium. In this case, impurities derived from the grinding medium may be mixed into the obtained powder. If the amount of impurities contained in the powder is large, the conductivity of the resulting air electrode may be reduced, and the power generation efficiency may be reduced.

However, the powder for an air electrode is also required to have high crystallinity. Therefore, the metal composite oxide is preferably synthesized at a higher temperature in the solid phase method. However, the highly crystalline metal composite oxide has high hardness, and the grinding medium is more easily abraded. That is, obtaining a powder having high crystallinity and reducing the amount of impurities contained in the powder are in a trade-off relationship.

Means for solving the problems

In view of the above, the present invention relates to a powder for an air electrode of a solid oxide fuel cell, having the following general formula:

A1_1-xA2_xBO_3-δ

(wherein, element A1 is at least one selected from the group consisting of La, Sm, element A2 is at least one selected from the group consisting of Ca, Sr, Ba, element B is at least one selected from the group consisting of Mn, Fe, Co, Ni, 0 < x < 1, delta is oxygen vacancy amount); the specific surface area of the powder was 20m²(ii)/g or more, satisfies the condition that (crystallite diameter/particle diameter converted to specific surface area) is not less than 0.3, and the content of the element M excluding the element A1, the element A2, the element B and oxygen is not more than 300ppm in terms of atoms.

In view of the above, the present invention relates to a method for producing a powder for an air electrode of a solid oxide fuel cell, including the steps of:

a preparation step of preparing a composition having the following general formula:

A1_1-xA2_xBO_3-δ

(wherein, element A1 is at least one selected from the group consisting of La, Sm, element A2 is at least one selected from the group consisting of Ca, Sr, Ba, element B is at least one selected from the group consisting of Mn, Fe, Co, Ni, 0 < x < 1, delta is oxygen vacancy amount); and a grinding step of grinding the metal composite oxide using alumina beads to obtain a specific surface area of 20m²A powder having a particle size of 0.3 or more (crystallite diameter/particle diameter converted to specific surface area).

Effects of the invention

The powder for an air electrode of the present invention is fine and has high crystallinity and a small amount of impurities.

The novel features of the present invention are set forth in the appended claims, and both the structure and content of the present invention will be better understood from the following detailed description, along with other objects and features of the present application.

Detailed Description

(powder for air electrode)

The powder for an air electrode according to an embodiment of the present invention has a structure represented by the following general formula (1):

A1_1-xA2_xBO_3-δ (1)

the metal composite oxide having a perovskite crystal structure is described.

The element a1 is at least one selected from the group consisting of La (lanthanum) and Sm (samarium). The element a2 is at least one selected from the group consisting of Ca (calcium), Sr (strontium), and Ba (barium). The element B is at least one selected from the group consisting of Mn (manganese), Fe (iron), Co (cobalt), and Ni (nickel). X is more than 0 and less than 1, and delta is the oxygen vacancy.

The element a1 preferably comprises La. The content of La in the element a1 may be 90 atomic% or more. Element a2 preferably contains Sr. The Sr content in the element a2 is preferably 90 atomic% or more. x is not particularly limited, but is more preferably 0.2. ltoreq. x.ltoreq.0.6, and still more preferably 0.3. ltoreq. x.ltoreq.0.5.

The element B preferably contains at least 1 of Co and Fe. The proportion of Co or Fe in the element B, or the total proportion thereof when Co and Fe are contained is preferably 90 atomic% or more. Among them, the element B preferably contains Co and Fe. Atomic ratio of Fe to Co: the Fe/Co ratio is preferably 2 to 6, more preferably 3 to 5.

Specifically, as the metal composite oxide, lanthanum strontium cobalt ferrite (LSCF, La) can be mentioned_1-x1Sr_x1Co_{1- y1}Fe_y1O_3-δX1 < 0 and y1 < 1, and lanthanum strontium manganite (LSM and La)_1-x2Sr_x2MnO_3-δ0 < x2 < 1), lanthanum strontium cobaltite (LSC, La)_1-x3Sr_x3CoO_3-δX3 < 1 > 0), samarium strontium cobaltite (SSC, Sm)_1-x4Sr_x4CoO_3-δX4 < 1 > 0), lanthanum strontium calcium manganite (LSCM, La)_1-x5-y2Sr_x5Ca_y2MnO_3-δ0 < x5 < 1, 0 < y2 < 1), etc. Particularly, LSCF in which the element a1 is La, the element a2 is Sr, and the element B is Co and Fe is preferable from the viewpoint of electrical conductivity and thermal expansion coefficient.

The metal composite oxide occupies most of the powder for an air electrode (hereinafter, sometimes referred to as ABO powder) of the present embodiment. In other words, the amount of impurities (element M other than element a1, element a2, element B, and oxygen) contained in the ABO powder is very small. That is, in the ABO powder, the element M is 300ppm or less in atomic terms. The element M in the ABO powder is preferably 150ppm or less in atomic terms.

The ABO powder is obtained by, for example, pulverizing a metal composite oxide obtained by synthesizing a mixture of a plurality of raw materials. In this case, the element M is mainly derived from the use of a grinding medium in the grinding step. Examples of the main element M include Zr (zirconium), Al (aluminum), and Si (silicon).

Zr, Al, and Si exist in the ABO powder, for example, as oxides. These oxides generally have insulating properties and cause a decrease in conductivity. Therefore, in the present embodiment, the total amount of Zr, Al, and Si in the ABO powder may be 300ppm or less in atomic terms. This suppresses a decrease in the electric conductivity of the resulting air electrode. Therefore, the output density of the fuel cell is improved.

Here, it is considered that the alumina suppresses the sinterability. Therefore, when an air electrode is produced by sintering an ABO powder containing an oxide of Al (aluminum), the porosity of the resulting air electrode is likely to be improved. In consideration of this, Al (aluminum) may be contained as the element M. The content of Al (aluminum) in the ABO powder is preferably 1ppm or more in terms of atomic conversion. The proportion of Al in the element M may be 50 atomic% or more, or may be 65 atomic% or more. For example, when Al and Zr are contained as the element M, Al may be larger than Zr in atomic conversion.

Each element contained in the ABO powder was quantified by high-frequency inductively coupled plasma emission spectrometry (ICP emission spectrometry) in accordance with JIS K0116. The content of the element M is determined so that the atomic number of the element M is a ratio of the total atomic number of the element a1, the element a2, the element B, oxygen, and the element M.

The specific surface area of the ABO powder is 20m²More than g. If the specific surface area of the ABO powder is in this range, it can be said that the ABO powder is sufficiently reduced in size to a level suitable as a material for an air electrode. Therefore, the three-phase interface between the air (oxidizing agent) and the air electrode and the electrolyte becomes large, and the reactivity of the entire electrode increases. The specific surface area of the ABO powder is preferably 21m²More than g. The specific surface area of the ABO powder is preferably 40m²A ratio of 35m or less per gram²The ratio of the carbon atoms to the carbon atoms is less than g. If the specific surface area of the ABO powder is 40m²When the heat treatment is performed to form the air electrode, excessive sintering is easily suppressed. Therefore, the obtained air electrode is not excessively densified, and the air diffusibility is improved. Specific surface area in accordance with JIS Z8830: 2013, measured by the BET flow method.

Crystallinity of the ABO powder is evaluated by, for example, a crystallite diameter/specific surface area equivalent particle diameter (hereinafter referred to as crystallinity parameter P1). In addition, the units of both are unified in advance. The crystallinity parameter P1 is closer to 1, and it can be said that the crystallinity of the ABO powder is higher as the ABO powder is closer to a single crystal.

The ABO powder may include secondary particles in which particles are aggregated. The crystallinity parameter P1 is an index of the crystallinity of the ABO powder calculated by removing the influence of the secondary particles. When the ABO powder is assumed to be spherical, the specific surface area-converted particle diameter is the diameter of the sphere calculated from the specific surface area and the density of the ABO powder. The crystallite diameter represents the size of a single crystal calculated from the half width (half width) of the diffraction peak of an X-ray diffraction pattern. When the crystallinity parameter P1 is 1, the specific surface area equivalent particle diameter is the same as the crystallite diameter. In general, since the specific surface area-reduced particle diameter is larger than the crystallite diameter, the crystallinity parameter P1 is less than 1.

The ABO powder of the present embodiment satisfies the crystallinity parameter P1 of not less than 0.3. The crystallinity parameter P1 is preferably 0.35 or more, and more preferably 0.37 or more. When the crystallinity parameter P1 of the ABO powder is 0.3 or more, the crystallinity of the ABO powder is sufficiently high. Therefore, the air electrode formed of the ABO powder has excellent conductivity and reactivity.

The crystallite diameter is not particularly limited, but is preferably 10nm or more. More preferably 15nm or more. The crystallite diameter is preferably 50nm or less. More preferably 20nm or less.

The crystallite diameter was calculated from the half-peak width of the diffraction line in the X-ray diffraction pattern of the ABO powder using the Scherrer's formula (Scherrer) below.

Crystallite diameter K x λ/β cos θ

Wherein the content of the first and second substances,

K-Scherrer constant (1)

λ ═ wavelength of X-rays (Cu — ka radiation))

Beta half peak width (radian unit)

Angle of Bragg (1/2 for diffraction angle 2 theta)

The specific surface area-equivalent particle diameter is not particularly limited, but is preferably 10nm or more. More preferably 15nm or more. The specific surface area-equivalent particle diameter is preferably 50nm or less, for example. More preferably 45nm or less.

The specific surface area-converted particle diameter is calculated from the specific surface area measured as described above using the following conversion formula. The theoretical density ρ is calculated by adding the true densities of the respective oxide components constituting the ABO powder according to the composition ratio.

S＝6/(ρ×d)

Wherein the content of the first and second substances,

specific surface area (S ═ S)

Rho is theoretical density of ABO powder

d is a specific surface area-converted particle diameter (unit μm)

In terms of easy improvement of conductivity, the ABO powder preferably has high crystallinity and high dispersibility (less aggregation of particles). Crystallinity and dispersibility of ABO powder can be evaluated by using a crystallite diameter/average particle diameter (hereinafter referred to as crystallinity parameter P2). This is because the crystallinity parameter P2 includes an influence of the secondary particles of the ABO powder. In addition, the units of both are unified in advance. The crystallinity parameter P2 is closer to 1, and it can be said that the crystallinity and dispersibility of the ABO powder are higher. Generally, the average particle size is larger than the crystallite diameter, and the crystallinity parameter P2 is lower than 1.

The ABO powder of the present embodiment preferably has a crystallinity parameter P2 of not less than 0.05. The crystallinity parameter P2 is more preferably 0.053 or more, and still more preferably 0.055 or more. When the crystallinity parameter P2 is 0.05 or more, the dispersibility and crystallinity of the particles constituting the ABO powder are sufficiently high. Further, there is not necessarily a correlation between the crystallinity parameters P1 and P2, and even when the ABO powder satisfies the crystallinity parameter P2. gtoreq.0.05, the crystallinity parameter P1 may be less than 0.3. In this case, crystallinity of the ABO powder is not sufficient.

The average particle diameter is not particularly limited, but is preferably 0.01 μm or more. More preferably 0.015 μm or more. The average particle diameter is preferably 1.5 μm or less. More preferably 1.25 μm or less.

The average particle diameter is a particle diameter at which a cumulative volume is 50% in a volume-based particle size distribution measured by a laser diffraction method (the same applies hereinafter).

(method for producing powder for air electrode)

The ABO powder is produced, for example, by a method including the steps of: a preparation step of preparing a metal composite oxide represented by the general formula (1); and pulverizing the metal composite oxide using alumina beads (hereinafter, sometimes referred to as alumina beads) to obtain a specific surface area of 20m²A step of pulverizing a powder having a crystallinity parameter P1 of not less than 0.3.

In general, when the metal composite oxide is pulverized so that its crystallinity parameter P1 satisfies the above condition, the specific surface area is 20m²The amount of impurities derived from the grinding medium contained in the obtained ground product increases up to/g. However, when alumina beads are used as the pulverization medium, the amount of impurities contained in the pulverized material is significantly reduced. The reason is not clear, but it is considered that: the alumina beads have such a hardness that they do not undergo significant chipping or cracking and remain deformed even when the metal composite oxide collides. For example, the hardness of the alumina beads may be smaller than that of the metal composite oxide.

The alumina beads are preferably alumina beads having a purity of 99.99 mass% or more (hereinafter, may be referred to as high-purity alumina beads) in terms of further reducing the amount of impurities.

(preparation Process)

A metal composite oxide having a perovskite crystal structure represented by the general formula (1) is prepared. The metal composite oxide is, for example, in the form of particles or blocks.

The metal composite oxide is obtained, for example, by using a mixture of a1 st compound containing the element a1, a2 nd compound containing the element a2, and A3 rd compound containing the element B, and by using a solid phase method. In the solid phase method, the mixture is heated at an elevated temperature.

The 1 st compound may be appropriately selected depending on the kind of at least one element a1 selected from the group consisting of La and Sm. The compound 1 may be, for example, lanthanum carbonate (La)₂(CO₃)₃) Lanthanum hydroxide (La (OH)₃) Lanthanum oxide (La)₂O₃)、Samarium carbonate (Sm)₂(CO₃)₃) Samarium hydroxide (Sm (OH)₃) Samarium oxide (Sm)₂O₃) And the like.

The 2 nd compound may be appropriately selected according to the kind of at least one element a2 selected from the group consisting of Ca, Sr, and Ba. The compound No. 2 includes, for example, strontium carbonate (SrCO)₃) Strontium hydroxide (Sr (OH))₂) Calcium carbonate (CaCO)₃) Calcium hydroxide (Ca (OH)₂) Barium carbonate (BaCO)₃) Barium hydroxide (Ba (OH)₂) And the like.

The 3 rd compound may be appropriately selected according to the kind of at least one element B selected from the group consisting of Mn, Fe, Co, and Ni. Examples of the compound No. 3 include manganese oxide (Mn)₃O₄) Manganese carbonate (MnCO)₃) Iron oxide (Fe)₂O₃) Cobalt oxide (Co)₃O₄) Cobalt carbonate (CoCO)₃) Nickel oxide (NiO), nickel carbonate (NiCO)₃) And the like.

The heating temperature is not particularly limited, and is preferably 1250 ℃ or higher from the viewpoint of promoting diffusion of each element. More preferably 1300 ℃ or higher, and still more preferably 1400 ℃ or higher. When the mixture is heated at a high temperature in this manner, the crystallinity of the obtained metal composite oxide is improved, and the hardness is likely to be increased. According to the present embodiment, even when the metal composite oxide having high hardness is pulverized, the amount of impurities mixed in can be reduced. Further, according to the present embodiment, the crystallinity of the metal composite oxide is easily maintained.

The obtained metal composite oxide may be crushed before being subjected to the pulverization step. In this way, the metal composite oxide is easily pulverized by the alumina beads in the pulverizing step. The metal composite oxide may be, for example, a metal composite oxide having a specific surface area of 0.2m²/g～1m²Crushing in a manner of/g.

The crushing method is not particularly limited, and may be appropriately selected from crushers such as a coarse crusher, an intermediate crusher, a fine crusher, and an attritor. The crushing may be performed using a crusher, a chopper, a mortar, a cracker (Raikai mixers), or the like.

(Pre-pulverization step)

After the preparation step and before the pulverization step, the method may further comprise bringing the metal composite oxide to a specific surface area of 2m²More than or equal to g and less than 20m²A preliminary grinding step of grinding in the form of/g. This makes it easier to pulverize the metal composite oxide by the alumina beads. The metal composite oxide to be subjected to the preliminary pulverization step may be pulverized as described above. By pulverizing the metal composite oxide in stages, the efficiency of pulverization by the alumina beads is improved. If the efficiency of pulverization is improved, the amount of impurities is further reduced.

The method of preliminary pulverization is not particularly limited, and may be appropriately selected from the above-mentioned pulverizers, for example. The preliminary pulverization may be carried out by using a roll mill, a jet mill, a hammer mill, a tumbling mill, a planetary mill, or the like. In the pre-pulverization, a pulverization medium may also be used. When the specific surface area is in the above range, impurities derived from the pulverization medium are less likely to be generated. The pulverization medium used for the preliminary pulverization may be alumina beads, or may be another known pulverization medium. The pulverizing time is not particularly limited as long as the specific surface area is 2m²More than or equal to g and less than 20m²The form of/g may be set as appropriate.

(grinding step)

The obtained metal composite oxide or a pre-pulverized material thereof was pulverized using alumina beads to obtain a specific surface area of 20m²More than g and satisfies the crystallinity parameter P1 is more than or equal to 0.3. The ABO powder obtained preferably further satisfies the crystallinity parameter P2 of not less than 0.05. According to this embodiment, an ABO powder satisfying both the crystallinity parameter P1 of not less than 0.3 and the crystallinity parameter P2 of not less than 0.05 can be obtained.

The pulverization method is carried out by a medium-stirring type micro-pulverizer (e.g., a planetary mill) using alumina beads. The pulverization may be carried out in a wet manner or in a dry manner. In the case of wet pulverization, the source of the pulverization is reducedThe medium may also be deionized water from the viewpoint of impurity amount. The pulverization time is not particularly limited as long as the specific surface area of the obtained ABO powder is 20m²The ratio of the amount of the acid to the amount of the acid is set as appropriate. From the viewpoint of reducing the amount of impurities, the pulverization time may be 40m in terms of the specific surface area of the ABO powder²The ratio/g is appropriately set as follows.

The average particle diameter of the alumina beads is not particularly limited, and may be, for example, 0.3mm to 1.5mm, or may be 0.5mm to 1 mm.

The present invention will be specifically described below with reference to examples thereof. However, this embodiment does not limit the present invention.

First, a method of measuring or calculating each physical property value will be described.

(a) Specific surface area

The measurement was carried out by the BET flow method using a specific surface area measuring apparatus (Mountech Co., Ltd., manufactured by Ltd., Macsorb HM-1220). As the adsorption gas, pure nitrogen was used and the temperature was maintained at 230 ℃ for 30 minutes.

(b) Average particle diameter (D50)

The measurement was carried out under the following conditions using a laser diffraction-scattering particle size distribution measuring apparatus (MT-3300 EXII, manufactured by MicrotracBEL Corp.).

Measurement mode: MT-3300

Refractive index of particle: 2.40

Solvent refractive index: 1.333

(c) Quantitative analysis of elements

An ICP emission spectrometer (manufactured by Hitachi High-Tech Science Corporation, SPS3100-24HV) was used.

(d) Crystallite diameter

A diffraction pattern was obtained under the following conditions using an X-ray diffraction apparatus (manufactured by Rigaku Corporation, RINT TTRIII, radiation source CuK. alpha., monochromator, tube voltage 50kV, current 300mA, long slit PSA200 (total length 200mm, design opening angle 0.057 degrees)).

The determination method comprises the following steps: parallel method (continuous)

Scanning speed: 5 degree/min

Sampling width: 0.04 degree

2 θ: 20 to 60 DEG

The crystallite diameter was calculated from the half-peak width of the diffraction line corresponding to the (024) plane of the perovskite phase in the obtained diffraction pattern using the scherrer equation.

Crystallite diameter K x λ/β cos θ

Wherein the content of the first and second substances,

K-Scherrer constant (1)

λ ═ wavelength of X-rays (Cu — ka radiation))

Beta half peak width (radian unit)

Angle of Bragg (1/2 for diffraction angle 2 theta)

(e) Specific surface area converted particle diameter

From the specific surface area measured in (a), the specific surface area-converted particle diameter was calculated using the following conversion formula. As La_0.6Sr_0.4Co_0.2Fe_0.8O_3-δAs rho (density of sample powder) of the metal composite oxide, 5.79g/cm was used³(theoretical Density) as La_0.6Sr_0.4CoO_3-δThe rho (density of sample powder) of the metal composite oxide was 6.14g/cm³(theoretical density).

S＝6/(ρ×d)

Wherein the content of the first and second substances,

specific surface area (S ═ S)

Rho is the density of the sample powder

d is a specific surface area-converted particle diameter

[ example 1]

(1) Preparation procedure

Lanthanum carbonate (La) was weighed₂(CO₃)₃73.96g, manufactured by Wako pure chemical industries, Ltd.), strontium carbonate (SrCO₃31.80g of cobalt oxide (Co), Wako pure chemical industries, Ltd₃O₄8.64g of Wako pure chemical industries, Ltd.), and iron oxide (Fe)₂O₃34.40 manufactured by Wako pure chemical industries, Ltd.)g, and the resulting mixture was put into a 500mL resin container (pot).

150mL of zirconia beads having a diameter of 1.5mm and 250mL of deionized water were put into the above resin vessel, and wet-mixed by a planetary ball mill (P-5, manufactured by Fritsch Co., Ltd.) at 180rpm for 5 minutes. Subsequently, the beads were removed, and heating was performed at 150 ℃ to obtain a raw material mixture from which moisture was removed.

The above raw material mixture was put in a crucible made of alumina, and the crucible was placed in an electric furnace (SB-2025, made by MOTOYAMA corporation), and heated at 1400 ℃ for 2 hours. Thereafter, the resulting mixture was crushed in an agate mortar and passed through a sieve having a mesh of 500. mu.m, thereby obtaining particles.

Using an X-ray diffraction apparatus, the above particles were identified as having a composition represented by the formula: la_0.6Sr_0.4Co_0.2Fe_0.8O_3-δLSCF of the perovskite structure shown.

The specific surface area of the particles was 0.35m²(ii)/g, the average particle diameter thereof is 11 μm.

(2) Preliminary grinding step

The particles were pulverized using a supersonic jet pulverizer (Nippon Pneumatic Mfg. Co., Ltd., manufactured by Ltd., PJM-200SP) at a pulverizing pressure of 0.6MPa and an input speed of 50 g/min to obtain a pre-pulverized product.

The preliminary pulverized material was subjected to ICP emission spectrometry, whereby the Zr content was 33ppm and the Al content was 8 ppm. The specific surface area of the pre-pulverized material was 2.5m²(iv)/g, its average particle diameter is 1.8. mu.m.

(3) Grinding process

100g of the pre-ground material was weighed and placed in a resin container (capacity 500 mL). 165mL of alumina beads (TB-05, purity 99.99% by mass or more, manufactured by DAMING chemical Co., Ltd.) having a diameter of 0.5mm and 150mL of deionized water (wet grinding solvent) were placed in the above resin vessel, and wet grinding was carried out at 240rpm for 240 minutes by a planetary ball mill (P-5, manufactured by Fritsch). Thereafter, the beads were removed, and heating was performed at 110 ℃.

ABO powder X using an X-ray diffraction apparatus1 was identified as having the compositional formula: la_0.6Sr_0.4Co_0.2Fe_0.8O_3-δLSCF of the perovskite structure shown.

When the ABO powder X1 was subjected to ICP emission spectrometry, Zr and Al were contained as the element M, and the content of Zr was 25ppm in atomic terms and the content of Al was 51ppm in atomic terms.

The specific surface area of ABO powder X1 was 21.5m²In terms of a/g, the mean particle diameter is 0.29. mu.m, and the crystallite diameter is 17 nm.

[ example 2]

ABO powder X2 was obtained in the same manner as in example 1, except that the pulverization time in the pulverization step (3) was changed to 695 minutes.

Using an X-ray diffraction apparatus, ABO powder X2 was identified as having a composition formula: la_0.6Sr_0.4Co_0.2Fe_0.8O_3-δLSCF of the perovskite structure shown.

When the ABO powder X2 was subjected to ICP emission spectrometry, Zr and Al were contained as the element M, and the content of Zr was 32ppm in atomic terms and the content of Al was 101ppm in atomic terms.

The specific surface area of ABO powder X2 was 31.9m²In terms of a/g, the mean particle diameter is 0.26. mu.m, and the crystallite diameter is 15 nm.

[ example 3]

(1) Preparation procedure

Lanthanum carbonate (La) was weighed₂(CO₃)₃75.04g, manufactured by Wako pure chemical industries, Ltd.), strontium carbonate (SrCO₃31.94g of Wako pure chemical industries, Ltd.), and cobalt oxide (Co)₃O₄And Wako pure chemical industries, Ltd.) 43.02g was charged into a 500mL resin container.

150mL of zirconia beads having a diameter of 1.5mm and 250mL of deionized water were put into the above resin vessel, and wet-mixed at 180rpm for 5 minutes by a planetary ball mill (P-5, manufactured by Fritsch). Subsequently, the beads were removed, and heating was performed at 150 ℃ to obtain a raw material mixture from which moisture was removed.

The raw material mixture was put into a crucible made of alumina, and the crucible was placed in an electric furnace (SB-2025, made by MOTOYAMA corporation), and heated at 1300 ℃ for 2 hours. Thereafter, the resulting mixture was crushed in an agate mortar and passed through a sieve having a mesh of 500. mu.m, thereby obtaining particles.

Using an X-ray diffraction apparatus, the above particles were identified as having a composition represented by the formula: la_0.6Sr_0.4CoO_3-δLSC of perovskite structure is shown.

The specific surface area of the particles was 0.15m²(iv)/g, the average particle diameter thereof is 16 μm.

(2) Preliminary grinding step

The particles were pulverized using a supersonic jet pulverizer (Nippon Pneumatic Mfg. Co., Ltd., manufactured by Ltd., PJM-200SP) at a pulverizing pressure of 0.6MPa and an input speed of 50 g/min to obtain a pre-pulverized product.

The preliminary pulverized material was subjected to ICP emission spectrometry, whereby the Zr content was 34ppm and the Al content was 10 ppm. The specific surface area of the pre-pulverized material was 3.0m²(iv)/g, its average particle diameter is 2.0. mu.m.

(3) Grinding process

100g of the pre-ground material was weighed and placed in a resin container (capacity 500 mL). 165mL of alumina beads (TB-05, purity 99.99% by mass or more, manufactured by DAMING chemical Co., Ltd.) having a diameter of 0.5mm and 150mL of deionized water (wet grinding solvent) were charged into the above resin vessel, and wet grinding was carried out at 240rpm for 220 minutes by a planetary ball mill (P-5, manufactured by Fritsch). Thereafter, the beads were removed, and heating was performed at 110 ℃.

ABO powder X3 was identified as having the compositional formula La by X-ray diffraction apparatus_0.6Sr_0.4CoO_3-δLSC of perovskite structure is shown.

When the ABO powder X3 was subjected to ICP emission spectrometry, Zr and Al were contained as the element M, and the content of Zr was 34ppm in atomic terms and the content of Al was 64ppm in atomic terms.

The specific surface area of ABO powder X3 was 20.9m²A mean particle diameter of 0.26 μm/g,the crystallite diameter was 16 nm.

Comparative example 1

In the grinding step (3), ABO powder Y1 was obtained in the same manner as in example 1, except that zirconia beads (YTZ, manufactured by Nikkato Corporation) having a diameter of 0.5mm were used instead of the high-purity alumina beads, the rotation speed was set to 210rpm, and the grinding time was set to 160 minutes.

ABO powder Y1 was identified as having the composition formula La by X-ray diffraction apparatus_0.6Sr_0.4Co_0.2Fe_0.8O_3-δLSCF of the perovskite structure shown.

When the ABO powder Y1 was subjected to ICP emission spectrometry, the element M contained Zr and Al, and the content of Zr was 2920ppm in terms of atoms and the content of Al was 32ppm in terms of atoms.

The specific surface area of ABO powder Y1 was 21.1m²In terms of a/g, the mean particle diameter is 0.30. mu.m, and the crystallite diameter is 15 nm.

Comparative example 2

In the grinding step (3), ABO powder Y2 was obtained in the same manner as in example 1, except that zirconia beads (YTZ, manufactured by Nikkato Corporation) having a diameter of 1mm were used instead of the high-purity alumina beads, and the rotation speed was set to 210rpm and the grinding time was set to 160 minutes.

Using an X-ray diffraction apparatus, ABO powder Y2 was identified as having a composition formula: la_0.6Sr_0.4Co_0.2Fe_0.8O_3-δLSCF of the perovskite structure shown.

When the ABO powder Y2 was subjected to ICP emission spectrometry, the element M contained Zr and Al, and the content of Zr was 3080ppm in atomic terms and the content of Al was 30ppm in atomic terms.

The specific surface area of ABO powder Y2 was 22m²In terms of a/g, the mean particle diameter is 0.37. mu.m, and the crystallite diameter is 17 nm.

Comparative example 3

Particles were obtained by preparing a raw material mixture in the same manner as in example 1.

The obtained particles were subjected to the pulverization step (3) without going through the preliminary pulverization step (2).

In the grinding step (3), ABO powder Y3 was obtained in the same manner as in example 1, except that zirconia beads having a diameter of 1mm ((Nikkato Corporation, YTZ) were used instead of the high-purity alumina beads, and the rotation speed was set to 210rpm and the grinding time was set to 120 minutes.

Using an X-ray diffraction apparatus, ABO powder Y3 was identified as having a composition formula: la_0.6Sr_0.4Co_0.2Fe_0.8O_3-δLSCF of the perovskite structure shown.

When the ABO powder Y3 was subjected to ICP emission spectrometry, Zr and Al were contained as the element M, and the content of Zr was 3650ppm in atomic terms and the content of Al was 30ppm in atomic terms.

The specific surface area of ABO powder Y3 was 18.5m²In terms of a/g, the mean particle diameter is 0.44. mu.m, and the crystallite diameter is 19 nm.

Comparative example 4

Particles were obtained in the same manner as in example 1, except that the heating temperature in the preparation step (1) was set to 1200 ℃.

The particles were identified as having the composition formula La by an X-ray diffraction apparatus_0.6Sr_0.4Co_0.2Fe_0.8O_3-δLSCF of the perovskite structure shown.

The specific surface area of the particles was 0.75m²/g。

In the grinding step (3), wet grinding was performed in the same manner as in comparative example 3 except that the grinding time was set to 115 minutes, thereby obtaining ABO powder Y4.

ABO powder Y4 was identified as having the composition formula La by X-ray diffraction apparatus_0.6Sr_0.4Co_0.2Fe_0.8O_3-δLSCF of the perovskite structure shown.

When the ABO powder Y4 was subjected to ICP emission spectrometry, the element M contained Zr and Al, and the content of Zr was 2870ppm in atomic terms and the content of Al was 35ppm in atomic terms.

The specific surface area of ABO powder Y4 was 17.6m²In terms of a/g, the mean particle diameter is 0.25. mu.m, and the crystallite diameter is 10 nm.

The crystallinity parameters P1 and P2 of the ABO powders X1 to X3 and Y1 to Y4 obtained in examples 1 to 3 and comparative examples 1 to 4 were calculated. The results are shown in table 1.

TABLE 1

As is clear from Table 1, the ABO powders X1 to X3 obtained in examples 1 to 3 had a specific surface area of 20m²A content of the element M is 300ppm or less in terms of atom while satisfying a crystallinity parameter P1 of 0.3 or more and a crystallinity parameter P2 of 0.05 or more.

On the other hand, the ABO powders Y1 to Y3 obtained in comparative examples 1 to 3 had a crystallinity parameter P1 of 0.3 or more, but the content of the element M was significantly increased as compared with the ABO powders X1 to X3. This is presumably because the high heating temperature in the preparation step (1) improves the crystallinity, but the pulverization is carried out to a specific surface area of 20m²As a result, the amount of impurities derived from the grinding medium increases. The ABO powder Y4 of comparative example 4 had a large content of the element M and a small crystallinity parameter P1. This is presumably caused by the low heating temperature in the preparation step (1) and the absence of the preliminary pulverization step.

In contrast to ABO powders Y2 and Y3 of comparative examples 2 and 3, which had the crystallinity parameter P1 approximately equal to ABO powder X1, the crystallinity parameter P2 was smaller than ABO powder X1. This result shows that the grinding step (3) was not effectively performed in comparative example 2 using zirconia beads having a diameter of 1mm and comparative example 3 in which the preliminary grinding step was not performed. That is, in comparative examples 2 and 3, it is considered that only the surface of the particles was selectively pulverized to generate fine particles and the specific surface area was increased, while the matrix portion of the particles or the secondary particles were not pulverized.

Industrial applicability

The powder for an air electrode of the present invention is fine, has high crystallinity, and has a small amount of impurities, and therefore is useful as a material for an air electrode of a solid oxide fuel cell.

The present invention has been described in relation to presently preferred embodiments, and such disclosure is not to be interpreted as limiting. Various modifications and alterations will become apparent to those skilled in the art from this disclosure. It is therefore intended that the following appended claims be interpreted as including all such alterations and modifications as fall within the true spirit and scope of the invention.