JP5401847B2 - Composite ceramic powder, method for producing the same, and solid oxide fuel cell - Google Patents

Description

  The present invention relates to a composite ceramic powder, a method for producing the same, and a solid oxide fuel cell (SOFC), and more specifically, containing zirconia particles and nickel oxide particles, and particle distribution and composition control. The present invention relates to a composite ceramic powder having excellent properties, a method for producing the same, and a solid oxide fuel cell using the composite ceramic powder as an electrode material.

Conventionally, as a method for producing a composite ceramic powder containing a plurality of types of oxides, usually, a plurality of types of oxide powders are pulverized and pulverized using a ball mill, an automatic mortar, or the like. A method of stirring and mixing while crushing and crushing to obtain a composite ceramic powder is common.
In addition, an alkali solution is added to a solution containing a plurality of types of metal ions to form a neutralized precipitate, and then the neutralized precipitate is fired to generate an oxide to obtain a composite ceramic powder. A settling method is also known.

By the way, the composite ceramic powder obtained by various conventional methods is a composite powder in which a plurality of types of primary oxide particles are aggregated and mixed nonuniformly, or a plurality of types of oxides. There was a problem that each primary particle aggregated into a coarse composite powder. Therefore, when such a composite powder is used as a catalyst or an electrode for a fuel cell, there is a problem that the characteristics cannot be sufficiently exhibited.
In order to solve these problems, various methods for producing composite ceramic powders have been proposed so far.

In one of these methods, an oxide powder having oxygen ion conductivity made of yttria-stabilized zirconia (YSZ) or samaria-doped ceria is immersed in a solution containing nickel ions or cobalt ions, and then dried. Next, heat treatment is performed to hold nickel oxide or cobalt oxide on the surface of the oxide powder having oxygen ion conductivity, and the oxide powder is further mixed with nickel or cobalt oxide powder as a raw material. A method for forming powder has been proposed (Patent Document 1).
On the other hand, a mist pyrolysis method is known as a method excellent in oxide uniformity and composition control. For example, a solution containing yttria-stabilized zirconia particles and nickel acetate is misted and the mist is dried. A method has been proposed in which the composite particles in which the yttria-stabilized zirconia particles are unevenly distributed on the surface side of the nickel oxide particles are obtained by heating to a temperature higher than the thermal decomposition temperature of nickel acetate (Patent Document 2).
Japanese Patent No. 3565696 Japanese Patent No. 3193294

By the way, in the conventional method of mixing a plurality of kinds of oxide powders, these oxide powders can be mixed relatively uniformly by appropriately selecting the mixing method. Although it is possible to obtain a composite ceramic powder in which the powder is uniformly distributed, there is a problem that it is difficult to control the composition of these oxide powders themselves.
In addition, the conventional mist pyrolysis method certainly improves the uniformity of the distribution of multiple types of oxides and the controllability of the composition, but the primary particle size of the oxides in the obtained composite particles is small. Therefore, when this coarse composite particle is used as a catalyst or an electrode for a fuel cell, there is a problem that sufficient characteristics cannot be obtained.

In particular, in the field of solid oxide fuel cells, the fuel electrode has a role as a catalyst for reacting fuel gas and oxidant, and the reaction field in this electrode is the three-phase interface. It is said that it is. That is, in the nickel-yttria stabilized zirconia (Ni-YSZ) (fuel electrode) / yttria stabilized zirconia (electrolyte) system, the portion where nickel (Ni), yttria stabilized zirconia and fuel gas are all in contact is a three-phase interface. . Therefore, in order to improve the output characteristics of the solid oxide fuel cell, it is necessary to increase the amount of electrons generated by increasing the three-phase interface of the fuel electrode and to efficiently supply the generated electrons to the external circuit. .
Therefore, a composite ceramic powder having a more uniform particle size, excellent distribution and composition controllability, and having a larger number of three-phase interfaces, that is, a composite ceramic powder having a smaller primary particle size. Although it is required, the current situation is quite difficult.

  The present invention has been made to solve the above-mentioned problems, and is a composite ceramics excellent in the distribution and composition controllability of a plurality of types of oxide particles, having many three-phase interfaces, and excellent in electron conductivity. An object of the present invention is to provide a powder, a method for producing the same, and a solid oxide fuel cell.

As a result of intensive studies in order to solve the above-mentioned problems, the present inventors contain zirconia particles made of yttria-stabilized zirconia and nickel ions, and the dispersion average particle diameter of the zirconia particles is 20 nm or less. When the neutralized precipitate is formed by adding an acidic dispersion of zirconia to an alkaline solution, and this neutralized precipitate is heat-treated, it has excellent particle distribution and composition controllability, and has many three-phase interfaces. The present inventors have found that composite ceramic powder having excellent conductivity can be easily obtained, and have completed the present invention.

That is, the composite ceramic powder of the present invention is a composite ceramic powder containing nickel oxide and zirconia, containing zirconia particles made of yttria-stabilized zirconia and nickel ions, and the zirconia particles A neutralized precipitate obtained by adding a zirconia acidic dispersion having a dispersion average particle diameter of 20 nm or less to an alkaline solution is heat-treated.

When heat treatment is performed at 600 ° C. for 6 hours, the crystallite diameter of the nickel oxide is preferably 9 nm or less, and the crystallite diameter of the yttria-stabilized zirconia is preferably 3.6 nm or less.

The method for producing a composite ceramic powder according to the present invention includes a zirconia acidic dispersion containing zirconia particles made of yttria-stabilized zirconia and nickel ions , wherein the zirconia particles have a dispersion average particle diameter of 20 nm or less. A neutralized precipitate is produced by adding to the solution, and then the neutralized precipitate is heat-treated at a temperature of 200 ° C. or higher to produce a powder containing nickel oxide and zirconia.

The ratio (M: Z) of the molar percentage (M) of the nickel ions and the molar percentage (Z) of the zirconia particles in the zirconia acidic dispersion is:
M: Z is preferably in the range of 90:10 to 10:90.

  The solid oxide fuel cell of the present invention is characterized in that the composite ceramic powder of the present invention is used as an electrode material.

According to the composite ceramic powder of the present invention , a zirconia acidic dispersion containing zirconia particles made of yttria-stabilized zirconia and nickel ions , wherein the zirconia particles have a dispersion average particle diameter of 20 nm or less is used as an alkaline solution. Since the neutralized precipitate obtained by the addition is heat-treated, the particle distribution in the powder composed of a plurality of types of oxide particles can be improved, and the composition controllability of the particles can be improved. Therefore, it is possible to provide a composite ceramic powder that is excellent in distribution and composition controllability of a plurality of types of oxide particles, has many three-phase interfaces, and is excellent in electronic conductivity.

According to the method for producing a composite ceramic powder of the present invention , a zirconia acidic dispersion containing zirconia particles made of yttria-stabilized zirconia and nickel ions , wherein the zirconia particles have a dispersion average particle diameter of 20 nm or less. Then, it is added to an alkaline solution to produce a neutralized precipitate, and then this neutralized precipitate is heat-treated at a temperature of 200 ° C. or higher, so that a composite ceramic powder containing nickel oxide and zirconia can be easily and It can be manufactured at low cost.

  According to the solid oxide fuel cell of the present invention, since the composite ceramic powder of the present invention is used as an electrode material, the amount of electrons generated can be increased. As a result, electrons can be efficiently supplied to an external circuit, and output characteristics can be improved.

BEST MODE FOR CARRYING OUT THE INVENTION The best mode for carrying out the composite ceramic powder of the present invention, the production method thereof, and the solid oxide fuel cell will be described.
This embodiment is specifically described for better understanding of the gist of the invention, and does not limit the present invention unless otherwise specified.

[Composite ceramic powder]
The composite ceramic powder of the present embodiment is a composite ceramic powder containing nickel oxide and zirconia, and an alkaline dispersion of zirconia acidic dispersion containing zirconia particles made of yttria-stabilized zirconia and nickel ions. It is a powder obtained by heat-treating a neutralized precipitate obtained by adding to a solution.
The dispersion average particle diameter of the zirconia particles in the zirconia acidic dispersion is preferably 20 nm or less.

  This composite ceramic powder is obtained by adding a zirconia acidic dispersion containing zirconia particles made of yttria-stabilized zirconia and nickel ions to an alkaline solution to form a neutralized precipitate, and then this neutralized precipitate. It is manufactured by heat-treating an object at a temperature of 200 ° C. or higher.

[Production method of composite ceramic powder]
Hereinafter, the method for producing the composite ceramic powder of the present embodiment will be described in detail.
"Preparation of zirconia acidic dispersion"
Nickel ions are added to the zirconia dispersion to produce a zirconia acidic dispersion.
The zirconia particles contained in this zirconia dispersion are yttria-stabilized zirconia particles.
The yttria-stabilized zirconia particles can be produced by a hydrothermal synthesis method or a firing method. For example, the following method is suitable (see Japanese Patent Application Laid-Open No. 2006-16236).

This method is a method of producing a metal oxide precursor by neutralizing a metal salt solution with a basic solution, and producing metal oxide nanoparticles from the metal oxide precursor. Where m is the valence of the metal ions or metal oxide ions, and n is the molar ratio of the hydroxyl groups in the basic solution, the m and n are represented by the following formula 0.5 <n <m (1)
In order to satisfy the above, a basic solution is added to the metal salt solution to partially neutralize the metal salt solution, then an inorganic salt is added to the partially neutralized solution to form a mixed solution, and the mixed solution is heated by a method of heating. is there.

  As this metal salt solution, an aqueous solution containing an yttrium (Y) salt and a zirconium (Zr) salt is preferably used.

The dispersion average particle diameter of the zirconia particles made of yttria-stabilized zirconia is preferably 20 nm or less.
The reason for this is that when the dispersion average particle diameter exceeds 20 nm, when added to the alkaline solution in the subsequent step, a non-uniform precipitate of zirconia particles and nickel is likely to be generated, resulting in poor distribution. This is because composite ceramic powder having a non-uniform composition may occur.
Here, the dispersion average particle diameter means that the particle size distribution in this dispersion is measured by optically measuring the speed at which particles in the dispersion are diffused by Brownian motion by the dynamic light scattering method. The particle diameter corresponding to the maximum value of.

Next, an acid such as hydrochloric acid, nitric acid, and acetic acid is added to the zirconia dispersion, and the pH (hydrogen ion concentration) of the dispersion is adjusted to 4 or less to obtain a zirconia acidic dispersion.
Here, the pH was set to 4 or lower when nickel hydroxide (Ni) chloride, nitrate, sulfate, acetate, etc. were mixed in an aqueous solution in the subsequent step, and precipitation of nickel hydroxide, etc. This is to prevent things from being generated.

  Next, an aqueous solution containing a salt of nickel chloride, nitrate, sulfate, acetate or the like is added to the zirconia acidic dispersion, and zirconia acidic dispersion in which zirconia particles made of yttria-stabilized zirconia and nickel ions coexist. Make a liquid.

The ratio (M: Z) of the molar percentage of nickel ions (M) and the molar percentage of zirconia particles (Z) in this acidic zirconia dispersion is:
M: Z = 90: 10-10: 90
Preferably, it is in the range of
M: Z = 80: 20 to 20:80
Range.

  By making the ratio (M: Z) within the above range, composite ceramic particles in which nickel oxide (NiO) particles are compounded in zirconia particles made of yttria-stabilized zirconia, or yttria stable in nickel oxide particles. Composite ceramic particles in which zirconia particles made of zirconia are combined can be freely controlled and produced.

  When this ratio (M: Z) is out of the above range, the exposure ratio of the minor component particles on the surface of the composite ceramic particle is remarkably reduced, and therefore the three-phase interface amount is greatly reduced, resulting in solids. Since the electrical characteristics as an electrode for an oxide fuel cell are also greatly deteriorated, it is not preferable.

  The total concentration of zirconia particles composed of yttria-stabilized zirconia and nickel ions in this acidic zirconia dispersion is not particularly limited, but from the viewpoint of productivity and handling properties, the total of zirconia particles and nickel ions is About 0.5 mass%-10 mass% are preferable.

"Neutralized precipitate formation"
The above zirconia acidic dispersion is added to the alkaline solution to produce a neutralized precipitate.
Examples of the alkaline solution include sodium hydroxide (NaOH), potassium hydroxide (KOH), sodium carbonate (Na ₂ CO ₃ ), potassium carbonate (K ₂ CO ₃ ), sodium hydrogen carbonate (NaHCO ₃ ), potassium hydrogen carbonate (KHCO). ₃ ), ammonium hydrogen carbonate (NH ₄ HCO ₃ ), ammonium carbonate ((NH ₄ ) ₂ CO ₃ ), aqueous ammonia (NH ₄ OH), an aqueous solution of water-soluble organic amines, and the like can be used.
The concentration in the alkaline solution is not particularly limited, but is preferably in the range of 0.1 mol% to 5 mol% from the viewpoint of productivity and handling.

The amount of the alkaline solution to which the above zirconia acidic dispersion is added is such that the pH of the solution after the neutralized precipitate is formed by adding the zirconia acidic dispersion is 6 or more. Adjust. The reason is that when the pH of the solution after generation is less than 6, that is, on the acidic side, the neutralization of nickel ions becomes insufficient and the uniformity of the composition of the resulting composite ceramic powder is reduced. .
About the temperature of each solution at the time of adding said zirconia acidic dispersion to an alkaline solution, normal temperature may be sufficient, More preferably, it is the range of 1 to 50 degreeC.

"Heat treatment of neutralized precipitate"
Impurity ions such as alkali ions and halogen ions are removed from the neutralized precipitate using a normal filtration and washing device, and then dried using a dryer.
Next, the obtained dried product is heat treated at a maximum holding temperature of 200 ° C. or higher, preferably 500 ° C. or higher and 1000 ° C. or lower in an air atmosphere using an electric furnace or the like, for example. A composite ceramic powder comprising zirconia particles comprising yttria-stabilized zirconia is prepared.

  Here, the reason for limiting the maximum holding temperature of the heat treatment to 200 ° C. or higher is that if the maximum holding temperature is lower than 200 ° C., the generation of nickel oxide particles becomes insufficient, and as a result, zirconia particles made of yttria-stabilized zirconia. This is because composite ceramic particles in which nickel oxide particles are composited or composite ceramic particles in which zirconia particles composed of yttria-stabilized zirconia are combined in nickel oxide particles cannot be freely controlled and produced. .

  In this method, the dried product before the heat treatment is a state in which zirconia particles made of fine yttria-stabilized zirconia having a nanometer size and precursor particles of nickel oxide are uniformly mixed, and distributed uniformly. The zirconia particles prevent nickel oxide from fusing and prevent grain growth during heat treatment. Therefore, there is no possibility of generating coarse nickel oxide particles in the composite ceramic powder by heat treatment, and it is possible to produce a composite ceramic powder having a fine particle size together with zirconia particles made of yttria-stabilized zirconia and nickel oxide particles. .

[Solid oxide fuel cell]
The solid oxide fuel cell of this embodiment uses the composite ceramic powder as an electrode material for the fuel electrode. Since this electrode material can increase the amount of generated electrons, electrons can be efficiently supplied to an external circuit, and output characteristics can be improved.

  As a method for producing a fuel electrode of a solid oxide fuel cell using the above composite ceramic powder, a generally used method may be used. For example, the above composite ceramic powder, polyethylene glycol, polyvinyl butyral After the paste obtained by mixing with a binder such as yttria-stabilized zirconia is applied to the surface of a solid electrolyte substrate by a printing method or the like to form a film, it is 1200 ° C to 1500 ° C in an air atmosphere. And a method of firing at a temperature within the range.

  The above composite ceramic powder suppresses nickel fusion and grain growth even when the reduction metallization treatment of nickel oxide is performed in a reducing atmosphere during power generation of the solid oxide fuel cell. it can. Therefore, it is possible to provide a solid oxide fuel cell having a fuel electrode with a large amount of three-phase interface and excellent electronic conductivity.

FIG. 1 is a schematic diagram showing an electrochemical characteristic evaluation apparatus, which is an apparatus for measuring the electric characteristics of the fuel electrode of the solid oxide fuel cell.
In the figure, 1 is an electrolyte such as yttria-stabilized zirconia, 2 is a reference electrode made of platinum (Pt), and 3 is made of La _0.8 Sr _0.2 MnO ₃ (LSM) formed on the upper surface of the electrolyte 1. The air electrode 4 is a fuel electrode made of nickel oxide-yttria stabilized zirconia or the like formed on the lower surface of the reference electrode 2, 5 is a platinum net disposed on each of the air electrode 3 and the fuel electrode 4, and 6 is a glass seal. , 7 and 8 are coaxially disposed alumina tubes having different diameters, 9 is a platinum wire, 10 is dry air, and 11 is a humidified hydrogen gas having a composition of 3% H ₂ O-97% H ₂ .

  Here, in order to measure the electrode reaction resistance of the fuel electrode 4 of the solid oxide fuel cell, the air electrode 3 and the platinum net 5 are sequentially attached to the upper surface of the electrolyte 1, and the fuel electrode 4 is mounted on the lower surface of the reference electrode 2. And the platinum net 5 are sequentially attached, the dry air 10 is supplied to the air electrode 3, the humidified hydrogen gas 11 is supplied to the fuel electrode 4, and the fuel electrode 4 and the reference electrode 2 in the temperature range of 600 ° C to 800 ° C are supplied. The AC impedance is measured using the air electrode 3 as a counter electrode.

  As described above, according to the composite ceramic powder of the present embodiment, both zirconia particles made of yttria-stabilized zirconia and nickel oxide particles can be made into particles having a fine particle size. The distribution can be improved, and the composition controllability of the particles can be improved. Therefore, a composite ceramic powder excellent in the distribution and composition controllability of a plurality of types of oxide particles such as zirconia particles made of yttria-stabilized zirconia and nickel oxide particles, and having many three-phase interfaces and excellent electronic conductivity. Can be provided.

  According to the method for producing a composite ceramic powder of the present embodiment, a zirconia acidic dispersion containing zirconia particles made of yttria-stabilized zirconia and nickel ions is added to an alkaline solution to produce a neutralized precipitate. Then, since the neutralized precipitate is heat-treated at a temperature of 200 ° C. or higher, a composite ceramic powder having a fine particle size containing nickel oxide particles and zirconia particles made of yttria-stabilized zirconia, It can be produced easily and inexpensively.

  According to the solid oxide fuel cell of the present embodiment, since the composite ceramic powder of the present embodiment is used as the electrode material of the fuel electrode, the amount of electrons generated in the fuel electrode can be increased. As a result, electrons can be efficiently supplied to an external circuit, and output characteristics can be improved.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention concretely, this invention is not limited by these Examples.

"Example 1"
To 50 g of a 10 mol% yttria-stabilized zirconia (10YSZ) dispersion having a dispersion average particle diameter of 7.5 nm (solid content concentration of 10YSZ: 8.4 mass%, pH: 4.6), nickel nitrate hexahydrate (Ni A nickel nitrate aqueous solution obtained by dissolving 30.82 g of (NO ₃ ) ₂ · 6H ₂ O) in 650 g of dilute nitric acid having a pH of 3.3 is added and stirred, and the nickel ion-containing 10 mol% yttria stabilized zirconia (Ni-10YSZ) acidic dispersion (PH: 3.95) was prepared (dispersion A-1).

Next, 4.19 g of ammonium hydrogen carbonate (NH ₄ HCO ₃ ) was dissolved in 133 g of distilled water to prepare an aqueous ammonium hydrogen carbonate solution (basic aqueous carbonate solution) (aqueous solution B-1).
Subsequently, this dispersion A-1 was dripped at the aqueous solution B-1, and the neutralization deposit was obtained. Here, a 25 mass% aqueous ammonia solution was dropped into the aqueous solution B-1 simultaneously with the dispersion A-1, and the pH of the aqueous solution B-1 was maintained at 8.

Next, the neutralized precipitate thus obtained was washed with water four times by a suction filtration washing device to remove impurity ions, followed by solvent substitution with ethanol, and then dried in a dryer at 80 ° C. for 24 hours. . Next, the obtained dried product was pulverized in a mortar and heat-treated in an electric furnace to obtain a composite powder A-1 of nickel oxide-yttria stabilized zirconia (NiO-YSZ).
The masses of Ni, Y, and Zr in this composite powder A-1 were measured by fluorescent X-ray analysis, and the mass ratio of nickel oxide (NiO) and yttria stabilized zirconia (YSZ) was calculated based on the measurement results. . As a result, the mass ratio (NiO: YSZ) was 65:35.

FIG. 2 is a transmission electron microscope (TEM) image showing the composite powder A-1.
According to this figure, it can be seen that yttria-stabilized zirconia particles are combined and integrated in the nickel oxide particles.
In addition, in order to evaluate the uniformity of the composite powder A-1, the heat treatment was performed at 600 ° C. for 6 hours and at 800 ° C. for 6 hours. The crystallite size of yttria stabilized zirconia was measured. The results are shown in Table 1.

  Next, 1.5 g of the mixed powder obtained by heat-treating the above composite powder A-1 at 1000 ° C. for 6 hours was mixed with 0.5 g of polyethylene glycol (molecular weight: 400) and 10 g of ethanol by a ball mill. The mixed solution was heated to 80 ° C. to evaporate and remove ethanol to prepare a nickel oxide-yttria stabilized zirconia paste. Next, this paste was applied by screen printing onto an 8 mol% yttria-stabilized zirconia (8YSZ) substrate having a thickness of 300 μm, and then fired at 1300 ° C. for 2 hours to form a fuel electrode on the 8YSZ substrate.

Next, 1.5 g of La _0.8 Sr _0.2 MnO ₃ (LSM) powder was mixed with 0.5 g of polyethylene glycol (molecular weight: 400) and 10 g of ethanol in a ball mill, and then this mixed solution was mixed at 80 ° C. To remove the ethanol by evaporation to prepare an LSM paste. Next, this LSM paste was applied by screen printing onto an 8 mol% yttria-stabilized zirconia (8YSZ) substrate having a thickness of 300 μm and then baked at 1100 ° C. for 2 hours to form an air electrode on the 8YSZ substrate. Further, a platinum wire was wound around the side surface of the 8YSZ substrate to form a reference electrode.

Next, the electrode reaction resistance of the fuel electrode was measured using the electrochemical property evaluation apparatus shown in FIG. Here, dry air is supplied to the air electrode and the reference electrode, and humidified hydrogen gas having a composition of 3% H ₂ O-97% H ₂ is supplied to the fuel electrode at a flow rate of 50 mL / min. The electrode reaction resistance of the fuel electrode was evaluated by measuring the AC impedance between the reference electrode and the fuel electrode. The measurement temperature was 600 ° C. and 800 ° C., and the measurement frequency was 10 kHz to 0.1 Hz. The measurement results are shown in Table 1.
Further, when the surface of the fuel electrode was analyzed by TEM-EDX, it was confirmed that Ni, Y, and Zr were composite particles in which Ni, Y, and Zr were uniformly distributed at a high density.

"Example 2"
To 50 g of a 10 mol% yttria-stabilized zirconia (10YSZ) dispersion having a dispersion average particle diameter of 7.5 nm (solid content concentration of 10YSZ: 8.4 mass%, pH: 4.6), nickel nitrate hexahydrate (Ni A nickel nitrate aqueous solution in which 13.50 g of (NO ₃ ) ₂ · 6H ₂ O) is dissolved in 650 g of dilute nitric acid having a pH of 3.3 is added and stirred, and a nickel ion-containing 10 mol% yttria-stabilized zirconia (Ni-10YSZ) acidic dispersion (PH: 3.95) was prepared (dispersion A-2).

Subsequently, according to Example 1, 4.19 g of ammonium hydrogen carbonate (NH ₄ HCO ₃ ) was dissolved in 133 g of distilled water to prepare an aqueous ammonium hydrogen carbonate solution (basic aqueous carbonate solution) (aqueous solution B-1).
Subsequently, this dispersion A-2 was dripped at the aqueous solution B-1, and the neutralization deposit was obtained. Here, a 25 mass% aqueous ammonia solution was dropped into the aqueous solution B-1 simultaneously with the dispersion A-2, and the pH of the aqueous solution B-1 was maintained at 8.

Next, the neutralized precipitate thus obtained was washed with water four times by a suction filtration washing device to remove impurity ions, followed by solvent substitution with ethanol, and then dried in a dryer at 80 ° C. for 24 hours. . Next, the obtained dried product was pulverized in a mortar and heat-treated in an electric furnace to obtain a nickel oxide-yttria stabilized zirconia composite powder A-2.
The masses of Ni, Y and Zr in the composite powder A-2 were measured by fluorescent X-ray analysis, and the mass ratio of nickel oxide (NiO) and yttria stabilized zirconia (YSZ) was calculated based on the measurement results. . As a result, the mass ratio (NiO: YSZ) was 45:55.

  In addition, in order to evaluate the uniformity of the composite powder A-2, the heat treatment conditions were set at two temperatures of 600 ° C. for 6 hours and 800 ° C. for 6 hours. The crystallite size of yttria stabilized zirconia was measured. The results are shown in Table 1.

  Next, 1.5 g of the mixed powder obtained by heat-treating the above composite powder A-2 at 1000 ° C. for 6 hours was mixed with 0.5 g of polyethylene glycol (molecular weight: 400) and 10 g of ethanol by a ball mill. The mixed solution was heated to 80 ° C. to evaporate and remove ethanol to prepare a nickel oxide-yttria stabilized zirconia paste. Next, this paste was applied by screen printing onto an 8 mol% yttria-stabilized zirconia (8YSZ) substrate having a thickness of 300 μm, and then fired at 1300 ° C. for 2 hours to form a fuel electrode on the 8YSZ substrate.

Next, 1.5 g of La _0.8 Sr _0.2 MnO ₃ (LSM) powder was mixed with 0.5 g of polyethylene glycol (molecular weight: 400) and 10 g of ethanol in a ball mill, and then this mixed solution was mixed at 80 ° C. To remove the ethanol by evaporation to prepare an LSM paste. Next, this LSM paste was applied by screen printing onto an 8 mol% yttria-stabilized zirconia (8YSZ) substrate having a thickness of 300 μm and then baked at 1100 ° C. for 2 hours to form an air electrode on the 8YSZ substrate. Further, a platinum wire was wound around the side surface of the 8YSZ substrate to form a reference electrode.

Next, the electrode reaction resistance of the fuel electrode was measured using the electrochemical property evaluation apparatus shown in FIG. Here, dry air is supplied to the air electrode and the reference electrode, and humidified hydrogen gas having a composition of 3% H ₂ O-97% H ₂ is supplied to the fuel electrode at a flow rate of 50 mL / min. The electrode reaction resistance of the fuel electrode was evaluated by measuring the AC impedance between the reference electrode and the fuel electrode. The measurement temperature was 600 ° C. and 800 ° C., and the measurement frequency was 10 kHz to 0.1 Hz. The measurement results are shown in Table 1.
Further, when the surface of the fuel electrode was analyzed by TEM-EDX, it was confirmed that Ni, Y, and Zr were composite particles in which Ni, Y, and Zr were uniformly distributed at a high density.

"Example 3"
To 50 g of a 10 mol% yttria-stabilized zirconia (10YSZ) dispersion having a dispersion average particle diameter of 7.5 nm (solid content concentration of 10YSZ: 8.4 mass%, pH: 4.6), nickel nitrate hexahydrate (Ni An aqueous nickel nitrate solution prepared by dissolving 75.00 g of (NO ₃ ) ₂ · 6H ₂ O in 650 g of dilute nitric acid having a pH of 3.3 is added and stirred, and a nickel ion-containing 10 mol% yttria-stabilized zirconia (Ni-10YSZ) acidic dispersion (PH: 3.95) was prepared (dispersion A-3).

Subsequently, according to Example 1, 4.19 g of ammonium hydrogen carbonate (NH ₄ HCO ₃ ) was dissolved in 133 g of distilled water to prepare an aqueous ammonium hydrogen carbonate solution (basic aqueous carbonate solution) (aqueous solution B-1).
Subsequently, this dispersion A-3 was dripped at the aqueous solution B-1, and the neutralization deposit was obtained. Here, a 25 mass% aqueous ammonia solution was dropped into the aqueous solution B-1 simultaneously with the dispersion A-3, and the pH of the aqueous solution B-1 was maintained at 8.

Next, the neutralized precipitate thus obtained was washed with water four times by a suction filtration washing device to remove impurity ions, followed by solvent substitution with ethanol, and then dried in a dryer at 80 ° C. for 24 hours. . Next, the obtained dried product was pulverized in a mortar and heat-treated in an electric furnace to obtain a composite powder A-3 of nickel oxide-yttria stabilized zirconia (NiO-YSZ).
The masses of Ni, Y and Zr in the composite powder A-3 were measured by fluorescent X-ray analysis, and the mass ratio of nickel oxide (NiO) and yttria stabilized zirconia (YSZ) was calculated based on the measurement results. . As a result, the mass ratio (NiO: YSZ) was 82:18.

  Further, in order to evaluate the uniformity of the composite powder A-3, the heat treatment conditions were 600 ° C. for 6 hours and 800 ° C. for 6 hours, and nickel oxide of each composite powder. The crystallite size of yttria stabilized zirconia was measured. The results are shown in Table 1.

  Next, 1.5 g of the mixed powder obtained by heat treating the composite powder A-3 at 1000 ° C. for 6 hours was mixed with 0.5 g of polyethylene glycol (molecular weight: 400) and 10 g of ethanol by a ball mill, The mixed solution was heated to 80 ° C. to evaporate and remove ethanol to prepare a nickel oxide-yttria stabilized zirconia paste. Next, this paste was applied by screen printing onto an 8 mol% yttria-stabilized zirconia (8YSZ) substrate having a thickness of 300 μm, and then fired at 1300 ° C. for 2 hours to form a fuel electrode on the 8YSZ substrate.

Next, 1.5 g of La _0.8 Sr _0.2 MnO ₃ (LSM) powder was mixed with 0.5 g of polyethylene glycol (molecular weight: 400) and 10 g of ethanol in a ball mill, and then this mixed solution was mixed at 80 ° C. To remove the ethanol by evaporation to prepare an LSM paste. Next, this LSM paste was applied by screen printing onto an 8 mol% yttria-stabilized zirconia (8YSZ) substrate having a thickness of 300 μm and then baked at 1100 ° C. for 2 hours to form an air electrode on the 8YSZ substrate. Further, a platinum wire was wound around the side surface of the 8YSZ substrate to form a reference electrode.

Next, the electrode reaction resistance of the fuel electrode was measured using the electrochemical property evaluation apparatus shown in FIG. Here, dry air is supplied to the air electrode and the reference electrode, and humidified hydrogen gas having a composition of 3% H ₂ O-97% H ₂ is supplied to the fuel electrode at a flow rate of 50 mL / min. The electrode reaction resistance of the fuel electrode was evaluated by measuring the AC impedance between the reference electrode and the fuel electrode. The measurement temperature was 600 ° C. and 800 ° C., and the measurement frequency was 10 kHz to 0.1 Hz. The measurement results are shown in Table 1.
Further, when the surface of the fuel electrode was analyzed by TEM-EDX, it was confirmed that Ni, Y, and Zr were composite particles in which Ni, Y, and Zr were uniformly distributed at a high density.

"Comparative example"
8.4 g of 10 mol% yttria-stabilized zirconia powder TZ-10Y (manufactured by Tosoh Corporation) was added to 41.6 g of dilute nitric acid having a pH of 3.3 and dispersed using an ultrasonic homogenizer to prepare a dispersion. The dispersion average particle diameter of the yttria-stabilized zirconia powder in this dispersion was 120 nm.
Next, an aqueous nickel nitrate solution prepared by dissolving 30.82 g of nickel nitrate hexahydrate (Ni (NO ₃ ) ₂ .6H ₂ O) in 650 g of dilute nitric acid having a pH of 3.3 was added to this dispersion, followed by stirring. A 10 mol% yttria-stabilized zirconia (Ni-10YSZ) acidic dispersion (pH: 3.95) was prepared (dispersion A-4).

Subsequently, according to Example 1, 4.19 g of ammonium hydrogen carbonate (NH ₄ HCO ₃ ) was dissolved in 133 g of distilled water to prepare an aqueous ammonium hydrogen carbonate solution (basic aqueous carbonate solution) (aqueous solution B-1).
Subsequently, this dispersion A-4 was dripped at the aqueous solution B-1, and the neutralization deposit was obtained. Here, a 25 mass% aqueous ammonia solution was dropped into the aqueous solution B-1 simultaneously with the dispersion A-4, and the pH of the aqueous solution B-1 was maintained at 8.

Next, the neutralized precipitate thus obtained was washed with water four times by a suction filtration washing device to remove impurity ions, followed by solvent substitution with ethanol, and then dried in a dryer at 80 ° C. for 24 hours. . Next, the obtained dried product was pulverized in a mortar and heat-treated in an electric furnace to obtain a composite powder A-4 of nickel oxide-yttria stabilized zirconia (NiO-YSZ).
The masses of Ni, Y and Zr in the composite powder A-4 were measured by fluorescent X-ray analysis, and the mass ratio of nickel oxide (NiO) and yttria stabilized zirconia (YSZ) was calculated based on the measurement results. . As a result, the mass ratio (NiO: YSZ) was 65:35.

  In addition, in order to evaluate the uniformity of the composite powder A-4, the heat treatment conditions were set at two temperatures of 600 ° C. for 6 hours and 800 ° C. for 6 hours. The crystallite size of yttria stabilized zirconia was measured. The results are shown in Table 1.

  Next, 1.5 g of the mixed powder obtained by heat-treating the above composite powder A-4 at 1000 ° C. for 6 hours was mixed with 0.5 g of polyethylene glycol (molecular weight: 400) and 10 g of ethanol by a ball mill. The mixed solution was heated to 80 ° C. to evaporate and remove ethanol to prepare a nickel oxide-yttria stabilized zirconia paste. Next, this paste was applied by screen printing onto an 8 mol% yttria-stabilized zirconia (8YSZ) substrate having a thickness of 300 μm, and then fired at 1300 ° C. for 2 hours to form a fuel electrode on the 8YSZ substrate.

Next, 1.5 g of La _0.8 Sr _0.2 MnO ₃ (LSM) powder was mixed with 0.5 g of polyethylene glycol (molecular weight: 400) and 10 g of ethanol in a ball mill, and then this mixed solution was mixed at 80 ° C. To remove the ethanol by evaporation to prepare an LSM paste. Next, this LSM paste was applied by screen printing onto an 8 mol% yttria-stabilized zirconia (8YSZ) substrate having a thickness of 300 μm and then baked at 1100 ° C. for 2 hours to form an air electrode on the 8YSZ substrate. Further, a platinum wire was wound around the side surface of the 8YSZ substrate to form a reference electrode.

Next, the electrode reaction resistance of the fuel electrode was measured using the electrochemical property evaluation apparatus shown in FIG. Here, dry air is supplied to the air electrode and the reference electrode, and humidified hydrogen gas having a composition of 3% H ₂ O-97% H ₂ is supplied to the fuel electrode at a flow rate of 50 mL / min. The electrode reaction resistance of the fuel electrode was evaluated by measuring the AC impedance between the reference electrode and the fuel electrode. The measurement temperature was 600 ° C. and 800 ° C., and the measurement frequency was 10 kHz to 0.1 Hz. The measurement results are shown in Table 1.

  The composite ceramic powder of the present invention is produced by adding a zirconia acidic dispersion containing zirconia particles made of yttria-stabilized zirconia and nickel ions to an alkaline solution to produce a neutralized precipitate. Is a composite ceramic powder containing nickel oxide and zirconia that is excellent in the distribution and composition controllability of multiple types of oxide particles, has many three-phase interfaces, and has excellent electronic conductivity. Therefore, the applicability is also great in the solid oxide fuel cell and various industrial fields related thereto.

It is a schematic diagram which shows the electrochemical property evaluation apparatus for evaluating the fuel electrode of the solid oxide fuel cell of one Embodiment of this invention. It is a transmission electron microscope (TEM) image which shows the nickel oxide yttria stabilized zirconia composite particle of one Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electrolyte 2 Reference electrode 3 Air electrode 4 Fuel electrode 5 Platinum net 6 Glass seal 7, 8 Alumina tube 9 Platinum wire 10 Dry air 11 Humidified hydrogen gas

Claims (5)

A composite ceramic powder containing nickel oxide and zirconia,
A neutralized precipitate obtained by adding a zirconia acidic dispersion containing zirconia particles composed of yttria-stabilized zirconia and nickel ions and having a dispersion average particle diameter of 20 nm or less to an alkaline solution. A composite ceramic powder obtained by heat treatment. The crystallite diameter of the nickel oxide when heat-treated at 600 ° C for 6 hours is 9 nm or less, and the crystallite diameter of the yttria-stabilized zirconia is 3.6 nm or less. The composite ceramic powder described. A zirconia acidic dispersion containing zirconia particles composed of yttria-stabilized zirconia and nickel ions and having a dispersion average particle diameter of 20 nm or less is added to an alkaline solution to form a neutralized precipitate. Then, this neutralized precipitate is heat-treated at a temperature of 200 ° C. or higher to produce a powder containing nickel oxide and zirconia, and a method for producing a composite ceramic powder. The ratio (M: Z) of the molar percentage (M) of the nickel ions and the molar percentage (Z) of the zirconia particles in the zirconia acidic dispersion is:
The method for producing a composite ceramic powder according to claim 3, wherein M: Z is in the range of 90:10 to 10:90.   A solid oxide fuel cell comprising the composite ceramic powder according to claim 1 or 2 as an electrode material.