JP2009134982A - Method of manufacturing solid oxide fuel cell, and calcining tool used for the method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a calcining tool for an SOFC calcination, in which an electric resistance layer is hard to be formed on a surface of a fuel electrode at the time of calcination, in which one part of the calcining tool is hard to be fixed and residual, and which is high in heat resistance; and to provide a method of manufacturing an SOFC in which conductivity reduction at the time of calcination is suppressed by using such a calcining tool, and which is high in current collecting efficiency. <P>SOLUTION: In the manufacturing method of the solid oxide fuel cell 10 equipped with a porous base material constituting a fuel electrode 12, a solid electrolyte 14 arranged on the base material, and an air electrode 16 arranged on the solid electrolyte, as the calcining tool arranged in contact with the porous base material when at least the porous base material constituting the fuel electrode, the calcining tool made of ferrite shown by MFe<SB>2</SB>0<SB>4</SB>(M is one or more of elements selected from a group consisting of Mn, Fe, Ni, Mg, Zn, and Co) is used. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a solid oxide fuel cell (SOFC), and more particularly to a technique for firing a fuel electrode (anode) constituting the SOFC.

Solid oxide fuel cells (SOFCs), also called solid oxide fuel cells, have a high power generation efficiency among various types of fuel cells, and have a low environmental load, allowing the use of various fuels. Therefore, development as a power generation device is underway.
As shown in FIG. 1, the basic structure of the SOFC (single cell) 10 is a porous structure of an air electrode (cathode) on one surface of a dense solid electrolyte (eg, a dense membrane layer) 14 made of an oxide ion conductor. 16 is disposed, and a fuel electrode (anode) 12 having a porous structure is disposed on the other surface. A fuel gas (typically hydrogen) is supplied to the surface of the solid electrolyte 14 on the fuel electrode 12 side, and a gas containing oxygen (typically air) is supplied to the surface of the solid electrolyte 14 on the air electrode 16 side. Is supplied.
The SOFC (single cell) solid electrolyte is typically composed of a zirconia-based material such as yttria-stabilized zirconia (YSZ) or scandia-stabilized zirconia (SSZ). The fuel electrode is typically composed of a composite material (for example, Ni-YSZ or Ni-SSZ) made of mixed conductive ceramics such as nickel oxide (NiO) and stabilized zirconia (for example, YSZ or SSZ). . NiO becomes metallic Ni when used after the reduction treatment. The air electrode is made of a perovskite complex oxide material such as LaCoO ₃ or La (Sr) MnO ₃ that has excellent catalytic activity and mixed conductivity.
In addition, since only one single cell constituting the SOFC has a limited power generation amount, it is generally used as a stack in which a plurality of the single cell structures are stacked in order to obtain a desired power. In the SOFC having a stack structure, as shown in FIG. 2, a separator (also called an interconnector) 20 is used to isolate cells and collect current. As a separator forming material, lanthanum chromite-based oxides (for example, LaCrO ₃ , La _0.8 Ca _0.2 CrO ₃ ) are preferable examples.
In order to achieve high current collection efficiency, the separator 20 and the surface of the solid electrolyte 14 facing the separator 20 need to be closely joined (sealed) while ensuring high airtightness. .

  As the solid electrolyte becomes thinner, the oxide ion conduction speed increases and the power generation performance is improved. For this reason, as one form of industrially promising SOFC (single cell), there is a so-called anode supported cell in which a thin solid electrolyte membrane is formed on the surface of a porous substrate constituting a fuel electrode. . As shown in FIG. 1 described above, this type of SOFC first forms a porous fuel electrode (for example, Ni-YSZ or Ni-SSZ) 12 by sheet molding (extrusion molding) or press molding. Next, a membrane-like solid electrolyte 14 is formed on the surface of the fuel electrode 12 by a wet method such as screen printing or dip coating, and a porous air electrode 16 is formed on the surface by a wet method such as screen printing or dip coating. Form. Then, the SOFC (single cell) 10 composed of the sintered air electrode 16, fuel electrode 12, and solid electrolyte 14 is manufactured by simultaneous firing or sequential firing for each layer.

When firing a fuel electrode-supported cell as described above, typically, a thick fuel electrode 12 is disposed below and fired as shown in FIG. Conventionally, when firing in such a state, there has been a problem of high reactivity between the firing jig and the object to be fired (that is, the fuel electrode in the case of a fuel electrode-supported cell). That is, when forming a dense membrane-like solid electrolyte, it is necessary to fire the material to be fired in a high temperature range of about 1300 ° C. For this reason, baking jigs (setters, mesh sands, etc.) made of zirconia or alumina having high heat resistance are generally used.
However, these ceramic firing jigs easily react with the components of the fuel electrode, which is an object to be fired, in a firing temperature range of about 1300 ° C. For example, a maximum temperature of about 1300 ° C. with a fuel electrode made of a composite material (cermet) made of NiO and stabilized zirconia (YSZ, SSZ, etc.) and an alumina firing jig (setter, etc.) in contact with each other When firing is performed, NiO and alumina react, and as a result, the Ni component in the fuel electrode may be reduced. For example, as schematically shown in FIG. 2, in the portion (electric resistance layer) 13 where the Ni component on the surface of the fuel electrode 12 is reduced, the electrical resistance of the portion increases due to the reduction of the Ni component. Since it falls, it is not preferable. In this regard, Patent Document 1 describes a firing jig characterized in that the NiO content is 40 to 90% by mass of the whole. However, NiO is a relatively expensive raw material, and it is not preferable to use a setter with a high NiO content because it increases the manufacturing cost of SOFC (single cell).
In the case of a combination of the composite material (Ni-YSZ, Ni-SSZ, etc.) and a zirconia firing jig, the reaction with NiO as in the case of using an alumina firing jig can be suppressed, but zirconia. There is a problem that the baking jig is easily bonded firmly to the surface of the fuel electrode (to the extent that it cannot be removed by hand) by combining with the zirconia component of the fuel electrode. As schematically shown in FIG. 2, when a part of the firing jig (for example, setter fragments or mesh sand) 30 adheres and remains on the surface of the fuel electrode, the fuel electrode 12 and the separator 20 are closely bonded. In addition, there is a possibility that the conductivity (current collection efficiency) of the fuel electrode may be significantly lowered due to the adhesion of non-conductive zirconia. The high NiO-containing firing jig described in Patent Document 1 described above does not solve the problem related to sticking / remaining of the firing jig on the surface of the fuel electrode. In addition, as a prior art regarding a baking jig, patent documents 2-4 are mentioned, for example.

International Publication No. WO99 / 59936 Pamphlet Japanese Patent Publication No.62-27344 Japanese Patent Publication No.62-48159 JP-A-8-128788

  Therefore, the present invention was created to solve the above-described problems in firing the above-described SOFC (typically a fuel electrode-supported SOFC having a fuel electrode composed of NiO and a zirconia-based material). The object of the present invention is to form a highly resistant heat-resistant SOFC by which it is difficult to form an electric resistance layer on the surface of the fuel electrode during firing (more preferably, a part of the firing jig does not stick and remain as it is). It is to provide a baking jig for use. Another object of the present invention is to provide a method for producing an SOFC with good current collection efficiency by suppressing the decrease in conductivity during firing using such a firing jig.

In order to achieve the above object, according to the present invention, a solid oxide comprising a porous substrate constituting a fuel electrode, a solid electrolyte disposed on the substrate, and an air electrode disposed on the solid electrolyte. A method of manufacturing a fuel cell (also known as a solid electrolyte fuel cell) is provided.
The solid oxide fuel cell manufacturing method disclosed herein includes at least when the porous substrate constituting the fuel electrode is fired (including the case of sequential firing and the case of simultaneous firing). As a firing jig disposed in contact with the porous substrate, the following formula:
MFe ₂ O ₄
Where M is one or more elements selected from the group consisting of Mn, Fe, Ni, Mg, Zn and Co;
It is characterized by using a ferrite firing jig shown by the following.
In the present specification, the “firing jig” refers to a tool used when firing an object to be fired. For example, a setter (supporting member) used to hold the object to be fired in a predetermined state in a firing furnace, and sand (that is, a powdery firing jig used for preventing welding) is referred to herein. This is a typical example of a firing jig.

In the production method of the present invention having the above-described configuration, the above-mentioned ferrite firing is performed when firing a porous substrate (for example, a composite material formed of NiO powder and stabilized zirconia powder) having at least a composition constituting the fuel electrode. Use a jig.
As a result, even when firing is performed in a high temperature range (for example, about 1300 ° C.), firing jigs such as setters and mesh sands are difficult to adhere to the fuel electrode. Even if a part of the firing jig adheres (residual) to the fuel electrode due to some physical cause, since the jig itself is made of ferrite and has conductivity, the conductivity of the fuel electrode ( A decrease in current collection efficiency can be suppressed. Further, when the porous base material constituting the fuel electrode has a composition containing NiO, the reduction of NiO from the base material (fuel electrode) during firing is suppressed, and the electric resistance layer 13 as described above (FIG. 2). Generation can be suppressed. Even when a part of NiO reacts with the firing jig during firing, the product (for example, NiFe ₂ O ₄ ) has a relatively high conductivity, so that the conductivity of the cell itself is significantly reduced. Can be deterred.
Therefore, according to the manufacturing method of the present invention disclosed herein, an SOFC (typically a fuel electrode-supported cell) having a fuel electrode with good current collection efficiency by preventing the decrease in conductivity due to the above-described sticking. Can be manufactured. For example, as an example of a solid oxide fuel cell obtained by the manufacturing method of the present invention, MFe ₂ O ₄ (where M is one selected from the group consisting of Mn, Fe, Ni, Mg, Zn and Co). Or a solid oxide characterized in that ferrite represented by two or more elements, for example, NiFe ₂ O ₄ , is attached to at least a part (for example, a part of the bottom surface of a cell (typically a fuel electrode)). Examples include physical fuel cells.

Preferably, as the firing jig, a firing jig made of ferrite containing at least Mn as M in the above formula is used. A firing jig made of ferrite containing manganese (typically manganese ferrite: MnFe ₂ O ₄ ) is excellent in heat resistance and chemical stability. For example, a firing jig made of manganese ferrite is used as a setter or filler. By doing so, the occurrence of strong sticking (for example, sticking that cannot be easily removed manually) can be prevented at a higher level, and an SOFC having a fuel electrode with excellent conductivity can be manufactured.

Moreover, in order to implement | achieve the said objective, this invention provides the baking jig for using in the baking process of the manufacturing method of this invention disclosed here. That is, the SOFC manufacturing firing jig disclosed here is disposed on a porous base material (for example, a composite material formed of NiO powder and stabilized zirconia powder) constituting the fuel electrode. A firing jig for manufacturing a solid oxide fuel cell (typically a fuel electrode-supported SOFC) including a solid electrolyte and an air electrode disposed on the solid electrolyte.
The firing jig disclosed here has the following formula:
MFe ₂ O ₄
Where M is one or more elements selected from the group consisting of Mn, Fe, Ni, Mg, Zn and Co;
It is comprised by the ferrite shown by this.

The firing jig disclosed here (for example, a setter or a mesh) is difficult to adhere to the fuel electrode during firing. Even if a part of the firing jig adheres (residual) to the fuel electrode due to some physical cause, since the jig itself is made of ferrite and has conductivity, the conductivity of the fuel electrode ( A decrease in current collection efficiency can be suppressed. Further, when the porous substrate constituting the fuel electrode has a composition containing NiO, the decrease in NiO from the substrate (fuel electrode) is suppressed, and the electric resistance layer 13 (FIG. 2) as described above is generated. Can be suppressed. For example, as an example of a solid oxide fuel cell obtained by firing using the firing jig of the present invention, MFe ₂ O ₄ (where M is a group consisting of Mn, Fe, Ni, Mg, Zn and Co). Ferrite represented by one or more elements selected from, for example, NiFe ₂ O ₄ , is attached to at least a part (for example, part of the bottom surface of a cell (typically a fuel electrode)). And a solid oxide fuel cell.
By using the firing jig disclosed here, a fuel electrode-supported SOFC having excellent conductivity can be stably produced (fired). A firing jig made of manganese-based ferrite (for example, MnFe ₂ O ₄ ) having excellent heat resistance and chemical stability is particularly preferable.

  Hereinafter, preferred embodiments of the present invention will be described. Note that matters other than the matters specifically mentioned in the present specification (for example, the composition of the firing jig) and matters necessary for the implementation of the present invention (for example, a general construction process of the fuel electrode-supported SOFC) Can be understood as a design matter of those skilled in the art based on the prior art in the field. The present invention can be carried out based on the contents disclosed in this specification and common technical knowledge in the field.

The SOFC production method of the present invention is a method characterized by the structure (composition) of a firing jig used when at least the porous substrate constituting the fuel electrode is fired. There is no particular limitation. Typically, the firing jig disclosed herein includes a solid electrolyte (typically a solid electrolyte formed in a film shape) disposed (formed) on a porous substrate constituting a fuel electrode. It is used in the process of firing the whole substrate.
For example, the shape and composition of the fuel electrode (anode), the air electrode (cathode), and the solid electrolyte may be arbitrarily selected according to various standards as long as they constitute a SOFC (typically a fuel electrode-supported SOFC). Can be determined. In addition, an SOFC stack formed by stacking a plurality of the cells together with the separators by using the SOFC manufactured by the manufacturing method disclosed herein (for example, a fuel electrode supported SOFC) as a single cell is constructed by various methods similar to the conventional one. be able to.

Solid electrolyte (typically a solid electrolyte membrane having a thickness of 1 mm or less (particularly 0.1 mm or less)) provided in an SOFC (typically a fuel electrode-supported SOFC) that can be produced by the production method disclosed herein As such, a zirconia-based solid electrolyte is suitable. For example, a suitable example is zirconia (YSZ) stabilized with yttria (Y ₂ O ₃ ). Other suitable zirconia-based solid electrolytes include zirconia (CSZ) stabilized with calcia (CaO), zirconia (SSZ) stabilized with scandia (Sc ₂ O ₃ ), and the like.

  The fuel electrode provided in the SOFC (typically fuel electrode supported SOFC) that can be manufactured by the manufacturing method disclosed herein is formed from a material containing a zirconia component in consideration of the problems and effects of the present invention. Those containing NiO are particularly preferable. For example, a fuel electrode (porous substrate) formed from a mixed material composed of stabilized zirconia such as YSZ and SSZ and NiO is preferable. Further, the shape of the fuel electrode is not particularly limited, and it may be typically formed on a porous substrate having a thickness of 10 mm or less (particularly 2 mm or less).

The air electrode provided in the SOFC manufactured by the manufacturing method disclosed here (typically a fuel electrode-supported SOFC) is not particularly limited, and the material constituting the air electrode of the conventional SOFC is appropriately selected and used. Thus, an air electrode having a desired shape (for example, a film-like air electrode having a thickness of 1 mm to 10 mm or less (particularly 0.1 mm or less)) can be formed. Preferred examples of the air electrode constituent material include perovskite oxides such as lanthanum cobaltate (LaCoO ₃ ) and lanthanum manganate (La _1-x Sr _x MnO ₃ ; where 0 ≦ x <1). . Although the number of oxygen atoms is represented as 3 in the above formula, the number of oxygen atoms may actually be 3 or less (typically less than 3) in the composition ratio.

Using the various materials as described above, a target SOFC, for example, a fuel electrode-supported SOFC, can be manufactured by the same steps as in the prior art.
For example, NiO powder (typically average particle diameter of 1 μm to 10 μm) of about 30 to 70% by mass (typically 100% by mass) and stabilized zirconia such as YSZ and SSZ of about 70 to 30% by mass Powder (typically an average particle size of 0.1 μm to 10 μm) is mixed with a suitable solvent (water, etc.), a binder (methylcellulose, polyvinyl alcohol, etc.) and the like to prepare a slurry-like or paste-like material. A porous substrate (fuel electrode support) having a desired shape can be formed by using the mixed material by various molding methods (for example, sheet molding or other extrusion molding methods).
Next, the porous substrate (fuel electrode material) is baked (calcined) in an appropriate temperature range (about 1000 to 1200 ° C.) under atmospheric conditions, or dip on the surface without firing (calcination). Solid electrolyte materials such as YSZ and SSZ (for example, a slurry-like preparation containing a stabilized zirconia powder having an average particle size of 0.1 μm to 10 μm, a solvent such as water, and a binder such as methylcellulose) by coating or screen printing. To form a solid electrolyte membrane. Next, the porous substrate on which the solid electrolyte membrane is formed is fired in an appropriate temperature range (about 1300 to 1500 ° C.) under atmospheric conditions.
Thereafter, an air electrode forming material such as a lanthanum manganate-based oxide (for example, a perovskite oxide powder having an average particle size of 0.1 μm to 10 μm is formed on the fired solid electrolyte membrane by dip coating or screen printing. A slurry-like preparation containing a solvent such as water and a binder such as methylcellulose is applied to form an air electrode. And the porous base material (fuel electrode base material) with a solid electrolyte membrane in which this air electrode was formed is baked by a suitable temperature range (about 1000-1200 degreeC) under atmospheric conditions. In addition, you may perform a baking process at once, after forming both a solid electrolyte membrane and an air electrode.

A stack can be manufactured by joining an appropriate separator to the fuel electrode-supported SOFC (single cell) manufactured as described above. As the separator (interconnector) for constructing the SOFC stack, a lanthanum chromite oxide that physically cuts off oxygen supply gas (for example, air) and fuel gas and has electronic conductivity is preferably used. For example, an oxide represented by the general formula: La _(1-x) Ma _(x) Cr _(1-y) Mb _(y) O ₃ can be used. Ma and Mb in the formula are the same or different one or more alkaline earth metals, and x and y are 0 ≦ x <1 and 0 ≦ y <1, respectively. Preferable examples include LaCrO ₃ or an oxide in which Ma or Mb is calcium (lanthanum calcia chromite), for example, La _0.8 Ca _0.2 CrO ₃ . Although the number of oxygen atoms is represented as 3 in the above formula, the number of oxygen atoms may actually be 3 or less (typically less than 3) in the composition ratio.

A separator having a predetermined shape can be produced by the same method as described above. For example, a molded body formed by extrusion molding or the like using a predetermined material (for example, a molding material containing a lanthanum chromite oxide powder having an average particle size of about 0.1 μm to 10 μm, a solvent such as water, and a binder such as methyl cellulose) Can be produced in an appropriate temperature range (for example, 1300 to 1600 ° C.) under atmospheric conditions to produce a separator having a predetermined shape.
Then, an SOFC stack can be manufactured by bonding the produced separator to a single cell using an appropriate bonding material.
Note that the above-described series of SOFC single cell and stack manufacturing processes are merely examples, and do not limit the present invention. In the SOFC manufacturing method of the present invention, various materials and processes used / implemented in the conventional SOFC manufacturing method can be applied as they are or while being appropriately changed. The conventional method can be applied as it is except for the use of a firing jig described later.

Next, the firing jig for manufacturing SOFC according to the present invention will be described in detail. The firing jig disclosed here is characterized by being formed of ferrite (that is, ceramics mainly composed of iron oxide). A ferrite having a spinel crystal structure is preferred. Table 1 lists ferrites having preferred spinel crystal structures.
As shown in Table 1, ferrite has a low electrical resistivity (Ω · m) and a high melting point of 1500 ° C. or higher, and is used when firing an SOFC (typically a fuel electrode-supported SOFC). It is suitable as a component of the firing jig. Manganese ferrite (MnFe ₂ O ₄ , Mn _0.6 Zn _0.4 Fe ₂ O _4, etc.) and nickel ferrite (NiFe ₂ O _4, etc.) are preferable, particularly high heat resistance and structurally stable. Manganese ferrite is preferred.

  By firing using a firing jig such as a setter composed of spinel type crystal structure as listed in Table 1 or a mesh sand, the used firing jig on the SOFC side to be fired Prevents a part from sticking (strongly sticking to the extent that it cannot be removed by hand), and a part of a small amount of firing jig to stick (typically easily removable by hand) Even in the state of being attached, the decrease in conductivity (current collection efficiency) in the fuel electrode of the SOFC can be suppressed due to the property of high conductivity (low electrical resistivity). Further, even when the fuel electrode contains NiO, the reactivity between the ferrite and the Ni component is extremely low, so that the reduction of the Ni component in the fuel electrode can be prevented.

  The form of the firing jig is not particularly limited, and can be determined according to the form of SOFC (single cell) to be fired, the shape of the firing furnace, and the like. Typically, according to the present invention, there is provided a mesh sand and a setter which are firing jigs for SOFC production used when producing (firing) SOFC. The average particle size of the mesh is not particularly limited, but a mesh (powder-like firing jig) made of ferrite powder having an average particle size of about 1 μm to 1000 μm (particularly 5 μm to 500 μm) is preferable. In addition, a firing jig characterized in that ferrite mesh sand is adhered (coated) to the surface of a ferrite setter having a predetermined shape is also a preferred embodiment. Further, in the case of a firing jig having a predetermined shape such as a setter, it is preferable that the porosity based on the mercury intrusion method is about 10 to 60%. If the porosity is larger than 60%, the mechanical strength is lowered, which is not preferable. If it is too small, there is a possibility that efficient burnout of a binder or the like may be hindered during firing, which is not preferable. Moreover, it also increases the weight of the jig itself.

  EXAMPLES Examples relating to the present invention will be described below, but the present invention is not intended to be limited to those shown in the following examples.

<Fabrication of fuel electrode compact>
A zirconia powder (average particle size: about 0.6 μm) stabilized with 3 to 8 mol% scandia and a nickel oxide powder (average particle size: about 3 μm) were combined with SSZ: NiO = 6: 4 (mass ratio). Mixed. Then, a general binder (here, polybutyl alcohol was used), a plasticizer (here, dibutyl phthalate was used) and a solvent (here, water was used) were added to the mixed powder. Kneaded thoroughly. Next, sheet molding (extrusion molding) was performed using this kneaded product, and a sheet-like molded body of 300 mm × 1000 mm × thickness 1 mm was obtained. After drying, the sheet-like molded body was punched out to obtain a circular fuel electrode molded body having a diameter of 30 mm.

<Production of firing jig>
An MnFe ₂ O ₄ powder (purity 99.9% or more, average particle size: about 10 μm) is added with a binder (here, polyvinyl alcohol (PVA) is used) and granulated to have an average particle size of about 80 μm. MnFe ₂ O ₄ powder was prepared. Next, this granulated powder was used and pressed into a circular shape having a diameter of 50 mm and a thickness of 5 mm by pressing at a pressure of 150 MPa. The compact was fired at 1400 ° C. for 6 hours in an air atmosphere to obtain a manganese ferrite sintered body having a dense structure with a porosity of about 30% based on the mercury intrusion method.
Further, the surface of the sintered body was mechanically polished to form a disc (setter) having a thickness of 3 mm. In this example, the MnFe ₂ O ₄ powder (purity 99.9% or more, average particle size: about 10 μm) was further applied to the surface of the disc as a filler. The amount of mesh sand applied was approximately 300 mg / cm ² . The manganese ferrite-made mesh sand coating disk member was used as a firing jig according to Example 1.

Further, as Comparative Example 1, the same disk-shaped alumina setter as in Example 1 was prepared from alumina powder (purity 99.9% or more, average particle size: about 10 μm) by the same treatment as in Example 1 above. A porosity based on the mercury intrusion method: about 30%) was produced. Further, the alumina powder was applied as a sand to the surface of the disk. The amount of mesh sand applied was approximately 300 mg / cm ² . The alumina mesh sand coating disk member was used as a firing jig according to Comparative Example 1.
Further, as Comparative Example 2, the same treatment as in Example 1 and Comparative Example 1 was performed, and the same as Example 1 and Comparative Example 1 from zirconia powder (purity 99.9% or more, average particle size: about 10 μm). A disk-shaped zirconia setter (porosity based on mercury intrusion method: about 30%) was produced. Further, the zirconia powder was applied as a sand to the surface of the disk. The amount of mesh sand applied was approximately 300 mg / cm ² . Such a zirconia-made mesh sand coated disc member was used as a firing jig according to Comparative Example 2.

<Fabrication of electrode and measurement of conductivity>
The fuel electrode molded body was placed on the upper surface of three types of disc-shaped firing jigs (Example 1, Comparative Example 1 and Comparative Example 2) having different compositions produced as described above. And it baked at 1300 degreeC for 2 hours in air | atmosphere atmosphere.
After the firing step, the surface of the obtained sintered body (fuel electrode) was observed. In the case of using the firing jig of Example 1 (manganese ferrite firing jig) and Comparative Example 1 (alumina firing jig), a small amount of fine sand adhered to the surface of the sintered body. The degree of adhesion was at a level that could be easily removed by hand. On the other hand, when the firing jig of Comparative Example 2 (zirconia firing jig) was used, a large amount of sand was firmly fixed to the surface of the sintered body and could not be removed by hand. It was. When the firing jig of Example 1 is used, a part of NiO of the fuel electrode reacts with the firing jig to generate NiFe ₂ O ₄ and adheres to a part of the bottom surface of the fuel electrode. It was. However, since the firing jig itself has high conductivity and is reduced to Ni and Fe-based metals, it does not cause the electric resistance of the fuel electrode.

Next, the sintered bodies obtained using the firing jigs of the examples and comparative examples were subjected to reduction treatment at 800 ° C. for 1 hour in a reducing atmosphere containing 4 mol% of hydrogen gas (the balance being nitrogen gas). . As a result, a fuel electrode composed of reduced nickel and stabilized zirconia was obtained.
The conductivity (S / cm) was measured for each obtained fuel electrode (sample) by a general direct current four-terminal method. Measurements were made at a total of 10 points with different electrode attachment positions for each sample, and the average, minimum and maximum values are shown in Table 2.

As shown in Table 2, when the manganese ferrite firing jig of Example 1 was used, the conductivity was higher than others. This prevents the electrical resistance layer (see FIG. 2 described above) from being formed on the fuel electrode by firing using the firing jig of Example 1, and also suppresses the sticking of the firing jig. However, even if a part of the firing jig (eg, sand) remains attached, the jig itself has high conductivity, so that the electrical performance of the fuel electrode is not deteriorated.
On the other hand, in the fuel electrode fired using the firing jig of Comparative Example 1 which is an alumina firing jig, the electrical conductivity was significantly reduced. This indicates the result that NiO in the fuel electrode reacts with alumina and the Ni component is lost from the fuel electrode. In addition, in the fuel electrode fired using the firing jig of Comparative Example 2 which is a zirconia firing jig, the average conductivity is fired using the firing jig of Comparative Example 1 which is an alumina firing jig. Although it was better than the case, the range between the minimum value and the maximum value of conductivity is wide. Furthermore, the lowest conductivity and a low conductivity close to it were measured at many measurement points. This indicates that the non-conductive zirconia fixing part forms a spot-like electric resistance part in the fuel electrode by fixing the zirconia firing jig to the surface of the fuel electrode.

As is clear from the above test results, by using the firing jig of the present invention made of ferrite, a fuel electrode with high conductivity (that is, good current collection efficiency) can be manufactured (fired). Then, by using the fuel electrode fired using the firing jig of the present invention, an SOFC with high current collection efficiency and excellent electrical characteristics (typically a fuel electrode-supported SOFC) can be produced. . Further, as is apparent from the description of the above examples, as one aspect of the SOFC produced by the production method of the present invention, MFe ₂ O ₄ (M is Mn, Fe, Ni, Mg) , One or more elements selected from the group consisting of Zn and Co), such as NiFe ₂ O ₄ or MnFe ₂ O _4, are attached to the SOFC (typically Can provide a fuel electrode-supported SOFC).

It is sectional drawing which shows typically a typical fuel electrode support type SOFC (single cell). Furthermore, it is sectional drawing which shows typically a fuel electrode support type SOFC provided with a separator.

Explanation of symbols

10 SOFC
12 Fuel electrode 13 Electrical resistance layer 14 Solid electrolyte 16 Air electrode 20 Separator 30 Eye sand

Claims (4)

A method for producing a solid oxide fuel cell comprising a porous substrate constituting a fuel electrode, a solid electrolyte disposed on the substrate, and an air electrode disposed on the solid electrolyte,
As a firing jig disposed in contact with the porous substrate when the porous substrate constituting at least the fuel electrode is fired, the following formula:
MFe ₂ O ₄
Where M is one or more elements selected from the group consisting of Mn, Fe, Ni, Mg, Zn and Co;
A method for producing a solid oxide fuel cell, comprising using a firing jig made of ferrite as shown in FIG.   The manufacturing method according to claim 1, wherein a firing jig made of ferrite containing Mn as M in the formula is used as the firing jig. A solid oxide fuel cell having the following formula:
MFe ₂ O ₄
Where M is one or more elements selected from the group consisting of Mn, Fe, Ni, Mg, Zn and Co;
A solid oxide fuel cell, characterized in that at least a part of the ferrite shown in FIG. Firing jig for manufacturing a solid oxide fuel cell comprising a porous substrate constituting a fuel electrode, a solid electrolyte disposed on the substrate, and an air electrode disposed on the solid electrolyte And the following formula:
MFe ₂ O ₄
Where M is one or more elements selected from the group consisting of Mn, Fe, Ni, Mg, Zn and Co;
A firing jig for producing a solid oxide fuel cell, characterized in that it is composed of the ferrite shown in FIG.

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