JP2009152016A - Protection film coating method on interconnector for solid oxide fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for densely coating a protection film made from a conductive ceramic material on an interconnector for a solid oxide fuel cell made from a Cr-containing heat resistant alloy material. <P>SOLUTION: The coating method of the protection film made from the conductive ceramic material on the interconnector for the solid oxide fuel cell made from the Cr-containing heat resistant alloy material is that slurry prepared by adding low temperature sintering assistant to the conductive ceramic material is applied to the surface of the Cr-containing heat resistant alloy material, reduced at 700-900°C, and baked at 750-850°C in the air atmosphere. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for coating a protective film on an interconnector for a solid oxide fuel cell, and more specifically, to an interconnector for a solid oxide fuel cell configured using a heat-resistant alloy material containing Cr. The present invention relates to a method for coating a protective film made of a conductive ceramic material.

  A unit cell or cell of a solid oxide fuel cell (hereinafter abbreviated as “SOFC” where appropriate) uses an anode (fuel electrode) and a cathode (air electrode, oxygen as an oxidizing agent) with an electrolyte made of solid oxide sandwiched between them. If present, an oxygen electrode) is arranged and is composed of a cathode / electrolyte / anode three-layer unit. In the following, the case where air is flowed as the oxidant gas to the cathode side will be described, but the same applies to the case where oxygen-enriched air or oxygen is flowed.

  SOFC has the following features (1) to (5). (1) Since the electrochemical reaction at the electrode proceeds smoothly due to the high operating temperature, there is little energy loss and the power generation efficiency is high. (2) Since the exhaust heat temperature is high, it is possible to further increase the power generation efficiency by using multiple stages. (3) Since the operating temperature is high enough to reform a hydrocarbon fuel such as natural gas, the reforming reaction can be performed inside the battery. For this reason, the fuel processing system (reformer + shift converter) necessary for low-temperature operating fuel cells such as phosphoric acid type and polymer type can be greatly simplified. (4) Since CO can be involved in the power generation reaction, fuel can be diversified. (5) Since all members are made of solid, there is no problem of corrosion or electrolyte evaporation that occurs in phosphoric acid fuel cells or molten carbonate fuel cells.

As the electrolyte material, for example, a sheet-like sintered body such as yttria stabilized zirconia (YSZ) is used, and as the anode, a porous body such as a mixture of nickel and yttria stabilized zirconia (Ni / YSZ cermet) is used. For example, a porous body such as Sr-doped LaMnO ₃ is used as the cathode, and the cell is usually formed by baking the anode and the cathode on both surfaces of the electrolyte material.

During the operation, oxygen in the air introduced into the cathode becomes oxide ions (O ²⁻ ) at the cathode and reaches the anode through the electrolyte. Here, it reacts with the fuel introduced into the anode and emits electrons to generate electricity and reaction products such as water and carbon dioxide. Spent air at the cathode is discharged as cathode offgas, and spent fuel at the anode is discharged as anode offgas.

  By the way, a conventional SOFC has a high operating temperature of about 800 to 1000 ° C., but recently, an SOFC operating at a temperature of about 600 to 800 ° C., which is lower than that, for example, a temperature of about 750 ° C. is being developed. . FIG. 1 is a diagram for explaining an example of a flat SOFC cell and shows a cross-sectional view. As shown in FIG. 1, the cell 1 is configured with an electrolyte membrane 3 disposed on an anode 2 and a cathode 4 disposed on the electrolyte membrane 3.

For example, a zirconia-based or LaGaO ₃ -based electrolyte material is used as the solid oxide electrolyte, which is configured to be supported by a thick anode, and is called a support membrane type. In the support membrane type, the thickness of the electrolyte membrane can be reduced. The thickness of the membrane becomes, for example, about 10 μm, and it can be operated at a low or medium temperature of 600 to 800 ° C. For this reason, it is possible to use a heat-resistant alloy, such as stainless steel, as a constituent material for the interconnector or the like, and it has various advantages such as miniaturization.

  When the SOFC cell is in operation, electric power is obtained by flowing air to the cathode side, flowing fuel to the anode side, and connecting both electrodes to an external load. Since a high voltage cannot be obtained with one cell, cells and cells are stacked by being alternately stacked via an interconnector. That is, in the flat SOFC stack, interconnectors and cells are alternately stacked for the purpose of electrically connecting adjacent cells and distributing, supplying, and discharging air and fuel to and from the cathode and anode, respectively. .

  FIG. 2 is a diagram for explaining a stacking example, that is, a configuration example of stacking support membrane type flat SOFC cells, and showing each member of the support membrane type flat SOFC stack at intervals to show the arrangement relationship. Yes. A case where three cells 1 and two interconnectors 5 between them are provided, and an interconnector 5 (this interconnector is also a frame) is provided on the upper surface of the upper cell and the lower surface of the lower cell, respectively. Show. The interconnector 5 is formed with a plurality of groove-like gas passages for supplying air and fuel to the cells. These are laminated by applying a load, for example.

  By the way, the interconnector is required to have many properties (1) to (8) below. (1) It is dense and does not permeate or leak gas. (2) High electronic conductivity. (3) Ion conductivity is small. (4) The material itself is chemically stable in both high-temperature oxidizing and reducing atmospheres. (5) Reaction with other members in contact such as two electrodes and excessive mutual diffusion do not occur. (6) The thermal expansion coefficient is consistent with other battery constituent materials. (7) The dimensional change due to the change in atmosphere is small. (8) It has sufficient strength.

  As such, the interconnector has many strict requirements, limiting its constituent materials. In order to satisfy these requirements as much as possible, a heat-resistant alloy containing Cr is used. Even in the case of SOFC with a low or medium operating temperature (about 600 to 850 ° C.), it is advantageous from the viewpoint of the above properties, performance, and cost to use a heat-resistant alloy containing Cr as a material for manifolds and interconnectors. It is.

  However, when a heat-resistant alloy containing Cr is used as the constituent material of the interconnector, it is common to form a chromium oxide film on the surface in an oxidizing atmosphere during operation of the SOFC. Since the chromium oxide film is not very conductive, the internal resistance of the SOFC cell stack increases when it is used as it is. Conventionally, it is effective to apply a protective film of a conductive material such as conductive ceramics or silver alloy on the surface of the Cr alloy as a means for preventing the generation of vapor species of chromium oxide which is the cause and preventing the internal resistance thereof. It is considered.

  FIG. 3 is a diagram for explaining the outline, and FIG. 3 (a) is a perspective view of the interconnector as shown in FIG. FIG. 3B is a side view when the conductive coating layer 6 is provided on the interconnector as shown in FIG. 3A (corresponding to FIG. 3C viewed from the left or right side), FIG. 3C is a side view on the side where a plurality of grooves for air circulation are provided, similarly provided with the conductive coating layer 6. As shown in FIGS. 3B to 3C, the surface of the heat-resistant alloy interconnector containing Cr is coated with a conductive material, that is, by providing a conductive protective film on the surface, the surface of the alloy is oxidized. Exposure to the surface of the physical scale layer, that is, the chromium oxide layer is avoided, and generation of vapor species of chromium oxide is prevented.

  By the way, in order to densely form conductive ceramics as a conductive material on the surface of a heat-resistant alloy containing Cr, it must be sintered at a high temperature of 1000 ° C. or higher. However, since there is no Cr-containing alloy at such a high temperature, a device for sintering at a lower temperature is required. In addition, an inexpensive method such as dipping is desired. Therefore, methods such as Non-Patent Documents 1 and 2 have been proposed.

In Non-Patent Document 1, the sintering temperature of Ce _0.9 Gd _0.1 O _1.95 is lowered by adding a sintering aid (Li) to Ce _0.9 Gd _0.1 O _1.95 (hereinafter abbreviated as “CGO” where appropriate). Has been successful. Specifically, when the CGO film is coated on the CGO dense body, 5 mol% of lithium nitrate (LiNO ₃ ) is added to the CGO, whereby the CGO sintering temperature for the CGO dense body is increased from 1200 ° C. The temperature is reduced to 800 ° C.

In Non-Patent Document 2, when forming a film of Mn _1.5 Co _1.5 O ₄ on the surface of a ferritic stainless steel, a dense film can be formed by incorporating a reduction treatment. However, although Mn _1.5 Co _1.5 O ₄ film, which is an oxide film, is relatively dense, there are many pores in the film and it is not completely dense. It cannot be used.

“7th EUROPEAN SOLID OXIDE FUEL CELL FORUM, 3-7 July 2006, Abstract p.49: Low Temperature Constrained Sintering of COG Films for SOFC Applications, 1 outside Jason Nicholas” “Journal of the Electrochemical Society 2005 A1896 ～ A1901: Thermal Growth and Performance of Manganese Cobaltite Spinel Protection on FERRITIC STAINLESS STEEL SOFC INTERCONNECTS, YANG Zhenguo, 3 others, Available electronically August 8, 2005”

  The present invention has been made to solve the above-described problems related to interconnectors using a heat-resistant alloy as a constituent material, and is for a solid oxide fuel cell configured using a heat-resistant alloy material containing Cr. It is an object of the present invention to provide a method for densely coating a protective film made of a conductive ceramic material on an interconnector.

  The present invention relates to a method for coating a protective film made of a conductive ceramic material on a solid oxide fuel cell interconnector composed of a heat-resistant alloy material containing Cr, and the conductive ceramic material is sintered at a low temperature. A solid oxide characterized in that a slurry to which an auxiliary agent is added is applied to the surface of the heat-resistant alloy material containing Cr, followed by reduction treatment at 700 to 900 ° C., and then firing at 750 to 850 ° C. in an air atmosphere. A method for coating a protective film on an interconnector for a fuel cell.

According to the present invention, the following effects (1) to (3) can be obtained.
(1) A protective film made of a dense conductive ceramic material can be formed on the surface of a heat-resistant alloy material containing Cr.
(2) Since a conductive ceramic material having a large particle size can be used as the conductive ceramic material, the number of work steps can be reduced and mass production is easy.
(3) Since a conductive ceramic material having a large particle size can be used as the conductive ceramic material, the manufacturing cost can be significantly reduced.

  The present invention is a method for coating a protective film made of a conductive ceramic material on an interconnector for a solid oxide fuel cell configured using a heat-resistant alloy material containing Cr. And after apply | coating the slurry which added the low-temperature sintering auxiliary agent to the electrically conductive ceramic material on the surface of the heat-resistant alloy material containing Cr, a reduction process is performed at 700-900 degreeC, and it baked at 750-850 degreeC in an air atmosphere then It is characterized by doing.

As the heat-resistant alloy material containing Cr in the present invention, any heat-resistant alloy material containing Cr used as a solid oxide fuel cell interconnector can be used. For example, the following materials (1) to (3) may be mentioned, but the material is not limited thereto.
(1) C: 0.02% (mass%, the same applies hereinafter), Mn: 0.50%, Ni: 0.26%, Cr: 21.97%, Zr: 0.22%, La: 0.04 %, Si: 0.40%, Al: 0.21%, Fe: Balance (2) C: 0.03%, Mn: 0.47%, Ni: 0.26%, Cr: 22.14%, Zr: 0.20%, La: 0.04%, Si: 0.40%, Al: 0.21%, Fe: balance (3) C: 0.02%, Mn: 0.48%, Ni: 0.33%, Cr: 22.04%, Zr: 0.20%, La: 0.08%, Low Si, Low Al, Fe: Balance

Examples of the conductive ceramic material in the present invention include Mn _X Co _{3 -X} O ₄ (0 <x <3), Mn _X Fe _{3 -X} O ₄ (0 <x <3), Zn _X Mn _{3 -X} O ₄ (0 <x <3), using a _{Cu X Mn 3-X O 4} (0 <x <3) or _{Co X Fe 3-X O 4} (0 <x <3). Among these, examples of Mn _X Co _3-X O ₄ (0 <x <3) include MnCo ₂ O ₄ , Mn _1.5 Co _1.5 O ₄ , Mn ₂ CoO _4, etc., and Mn _X Fe _3-X O ₄ (0 <x <3) is exemplified by MnFe ₂ O _{4 and the} like, and Zn _X Mn _{3 -X} O ₄ (0 <x <3) is exemplified by ZnMn ₂ O ₄ and Cu. _{X Mn 3-X O 4 (} 0 <x <3) examples of include Cu _1.4 Mn _1.6 O ₄ and the _{like, Co X Fe 3-X O} 4 CoFe 2 examples of (0 <x <3) O ₄ etc. are mentioned. These are materials having the same crystal structure as spinel.

  Li compound is used as the low temperature sintering aid in the present invention. Examples of the Li compound include, but are not limited to, lithium oxide, lithium hydroxide, lithium nitrate, lithium carbonate, lithium acetate, and lithium halide. These Li compounds are reduced to Li by a reduction treatment described later, and serve to densely sinter the conductive ceramic material at a lower temperature than before when firing in an air atmosphere described later. The “low temperature” in the low temperature sintering aid means the low temperature in “at a lower temperature than in the past”.

  In the present invention, a slurry obtained by adding a low-temperature sintering aid to a conductive ceramic material is applied to the surface of a heat-resistant alloy material containing Cr, and then subjected to a reduction treatment in a temperature range of 700 to 900 ° C., and then in an air atmosphere Bake in the temperature range of 750-850 ° C.

  In the present invention, the amount of the low-temperature sintering aid added to the conductive ceramic material may be 3 mol% or more with respect to 100 mol% of the conductive ceramic material, and the range is preferably 3 to 8 mol%. It is a range.

  (1) First, a slurry containing a conductive ceramic material and a low-temperature sintering aid uses water or a mixed solvent of water and alcohol as a solvent, and the conductive ceramic material, low-temperature sintering aid, organic A binder and a dispersant are mixed and sufficiently stirred with a ball mill or the like to form a slurry.

  (2) Next, the slurry is applied to the surface of the heat-resistant alloy material containing Cr. This coating can be performed by a screen printing method, a dipping method, or the like.

  (3) Next, reduction treatment is performed at 700 to 900 ° C. The temperature of the reduction treatment is more preferably 750 to 850 ° C. The reducing atmosphere during the reduction treatment is a gas atmosphere containing hydrogen. A preferable example thereof is a nitrogen atmosphere containing hydrogen. Moreover, the time of a reduction process should just be the time which can fully reduce | restore the component in the surface of the heat-resistant alloy material containing Cr, and the slurry apply | coated on the surface, Preferably it is 12 to 24 hours. The Li compound that is a low-temperature sintering aid is reduced to Li by a reduction treatment.

  (4) Next, firing is performed at 750 to 850 ° C. in an air atmosphere. The firing time in the air atmosphere is 12 to 24 hours.

  In the present invention, a protective film made of a dense conductive ceramic material can be formed on the surface of the heat-resistant alloy material containing Cr, which is a constituent material of the SOFC interconnector, by the steps (1) to (4). it can.

  The interconnector thus constructed will be described with reference to FIG. 3. In FIG. 3, 5 is a “heat-resistant alloy material containing Cr”, 6 is a protective layer coated on the surface thereof, ie, a “protective layer made of a conductive ceramic material”. ". In FIGS. 3B to 3C, the protective layer is disposed on the lower surface of the interconnector. However, it can be disposed on either the side surface, the upper surface, or both as required. FIG. 3 shows an application example to a flat plate type SOFC interconnector, but the protective layer of the present invention is also applied to other types of SOFC interconnectors.

As described in Non-Patent Document 1, the CGO film was formed on the ceramic surface, and the CGO sintering temperature was successfully reduced by adding a sintering aid (Li) to CGO. As described above, when a Mn _1.5 Co _1.5 O ₄ film is formed on the surface of ferritic stainless steel, a dense film can be formed by incorporating a reduction treatment. In the present invention, a sintering aid (Li) and By using reduction treatment, a protective film made of a dense conductive ceramic material is formed on the surface of a heat-resistant alloy material containing Cr.

Hereinafter, the present invention will be described in more detail based on experimental examples, but the present invention is not limited to the experimental examples. Here, as a representative example, an experimental example using MnCo ₂ O ₄ as a conductive ceramic material and an experimental example using CoFe ₂ O ₄ are described.

<Experimental example 1: conductive ceramic material = MnCo ₂ O ₄ >
<(1) Preparation of conductive ceramic material slurry>
An oily slurry of conductive ceramic material: MnCo ₂ O ₄ was prepared. MnCo of ₂ O ₄ powder (d50 = 1 [mu] m, a specific surface area ^{= 2.3m 2 / g), LiNO} 3, an organic binder, dispersing agent, ethanol were mixed, stirred for 10 days at a bench ball mill, oily MnCo ₂ O ₄ A slurry was prepared. As the MnCo ₂ O ₄ oily slurry, various oily slurries were prepared in which the addition ratio of LiNO ₃ to MnCo ₂ O ₄ was changed.

MnCo ₂ O ₄ is a conductive ceramic material, and LiNO ₃ is a low temperature sintering aid. Among these, the specific surface area of MnCo ₂ O ₄ powder is 2.3 m ² / g, whereas the specific surface area of CGO powder of Non-Patent Document 1 is 30-35 m ² / g, and MnCo ₂ O ₄ The particle size of the powder is much larger than that of CGO powder.

<(2) Application of conductive ceramic material slurry to interconnector material>
Heat-resistant alloy material containing Cr [manufactured by Hitachi Metals, Ltd., ZMG (registered trademark) 232L. Composition: C = 0.02% (mass%, the same applies hereinafter), Mn = 0.48%, Ni = 0.3%, Cr = 22.04%, Zr = 0.20%, La = 0.08% , Si = trace, Al = trace, Fe = balance]. The surface dimension of each plate is 1 cm × 1 cm (= 1 cm ² ).

For each of these plates, an oily slurry prepared in the above-mentioned <(1) Preparation of conductive ceramic material slurry> with a different addition ratio of LiNO ₃ to MnCo ₂ O ₄ was applied to the surface by screech printing. . After the application, it was dried in a thermostatic bath where the solvent, ethanol, was kept at around 100 ° C. In this way, each sample was prepared by coating and drying slurry with different addition ratios of LiNO ₃ to MnCo ₂ O ₄ for each plate.

<(3) Reduction treatment>
<(2) Application of slurry of conductive ceramic material to interconnector material> Each sample obtained in an electric furnace contains nitrogen atmosphere containing hydrogen [N ₂ 96% to H ₂ 4% (capacity%)] Atmosphere)] at 800 ° C. for 20 hours. In this process, LiNO ₃ is reduced to Li. Since Li ^{+ in} LiNO ₃ is monovalent, the mol% as LiNO ₃ is the same in Li.

<(4) Firing treatment>
<(3) Reduction treatment> Each sample after was fired in an electric furnace in an air atmosphere at 800 ° C. for 12 to 24 hours.

<Observation 1 of each prepared sample by SEM>
About each sample produced at the process of (1)-(4) above, the surface and the cross section were observed by SEM (scanning electron microscope). As a result, it was found that a dense MnCo ₂ O ₄ film was formed on the surface of each plate. FIG. 4 is an SEM photograph of a surface and a cross section of a sample (calcination treatment time in air atmosphere = 20 hours) with an addition amount of LiNO ₃ to MnCo ₂ O ₄ as an example. In FIG. 4, the left figure is a surface SEM photograph (magnification = 5000 times), and the right figure is a cross-sectional SEM photograph (magnification = 3500 times).

The left figure is the surface of the protective film (that is, the surface of the protective film having a thickness in the right figure SEM photograph. In the right figure SEM photograph, the upper layer having a thickness of about 2.1 cm is a resin layer. ). As shown in the left figure, the particle diameters of the MnCo ₂ O ₄ particles are uniform, and the particles are evenly or almost uniformly distributed. The right figure is a cross-sectional SEM photograph, but as shown in the right figure, the protective film is formed homogeneously or almost uniformly.

<Observation of each produced sample by SEM 2>
For each sample prepared in the above steps (1) to (4) were observed for differences due to the addition amount whether the LiNO ₃ (low temperature sintering aid) for MnCo ₂ O ₄ (conductive ceramic material). FIG. 5 shows a surface SEM photograph (magnification = 300 times) and a cross-sectional SEM photograph (magnification = 3500 times) of a sample having 2 mol%, 3 mol%, and 5 mol% of LiNO ₃ added. is there.

In the left figure in FIG. 5, the lower photograph is a cross-sectional SEM photograph of a sample having a LiNO ₃ addition amount of 2 mol%, and in the middle figure (center figure) in FIG. 5, the lower photograph is a LiNO ₃ addition amount of 3 mol%. The cross-sectional SEM photograph of the sample, and the lower photograph in the right figure in FIG. 5, is a cross-sectional SEM photograph of the sample with the LiNO ₃ addition amount of 5 mol%. Further, the upper photographs in the left, middle, and right diagrams in FIG. 5 are surface SEM photographs of the protective film.

As shown in FIG. 5, comparatively large pores are observed in the cross section in the sample with the LiNO ₃ addition amount of 2 mol%. In the sample with 3 mol% of LiNO ₃ added, pores are sparsely observed in the cross section, but it can be seen that the sample is dense as a whole. In the sample with the added amount of LiNO ₃ of 5 mol%, pores are not observed in the cross section, and it can be seen that the sample is dense and homogeneous as a whole. From this, it is understood that the desired protective film can be formed if the added amount of LiNO ₃ is 3 mol% or more.

<Observation of each produced sample by SEM 3>
Of the steps (1) to (4), the results of the ball mill time in <(1) Preparation of conductive ceramic material slurry> were observed.

The stirring time in the table-top ball mill in <(1) Preparation of conductive ceramic material slurry> is set to 1 day and 4 days, and the addition amount of LiNO ₃ is set to 5 mol%. Except for this point, the steps (1) to (4) above Each sample was prepared in the same manner as above. The sample in which the stirring time in the table-top ball mill was 10 days was prepared in the above-mentioned <(1) Preparation of conductive ceramic material slurry>. About each of these samples, the surface and the cross section were observed by SEM.

  FIG. 6 is an SEM photograph of the surface and cross section of each sample. Of these, the upper, left, middle, and right photographs are the surface SEM photographs (magnification = 300 times), and the lower, middle, and right pictures are the cross-sectional SEM photographs (magnification =). 3500 times).

  As shown in the left figure in FIG. 6, in the sample in which the stirring time in the table ball mill is 1 day, relatively large holes are observed in the cross section and relatively large particles are observed on the surface. In addition, in the sample with a stirring time of 4 days on the table ball mill, the cross section has fewer large holes than the cross section of the sample with the stirring time of 1 day, but the surface is the same as the sample with the stirring time of 1 day. Relatively large particles are observed.

  In contrast, in the sample with a stirring time of 10 days, no pores are observed in the cross section, and it can be seen that the sample is dense and uniform as a whole. In addition, only a few relatively large particles are observed on the surface. From this, it is understood that the stirring time in the ball mill at the time of producing the conductive ceramic material slurry may be about 10 hours or more.

<Experimental example 2: conductive ceramic material = CoFe ₂ O ₄ >
CoFe ₂ O ₄ powder (d50 = 1 μm, specific surface area = 2.5 m ² / g) was used as the conductive ceramic material, and <(1) Preparation of conductive ceramic material slurry> to <( 4) Each sample with LiNO ₃ addition amount of 2 mol%, 3 mol%, and 5 mol% was prepared in the same manner as in the firing treatment>, and the surface and the cross section thereof were observed with an SEM (scanning electron microscope). As a result, the same tendency as in the case of MnCo ₂ O ₄ in Experimental Example 1 is shown. When the addition amount of LiNO ₃ is 3 mol% or more, the particle diameter of CoFe ₂ O ₄ is uniform, and the protective film is homogeneous or almost homogeneous. It was found that it was formed.

FIG. 7 is an SEM photograph of the surface and cross section of a sample (calcination treatment time in air atmosphere = 20 hours) with an addition amount of LiNO ₃ to CoFe ₂ O ₄ as an example. In FIG. 7, the left figure is a surface SEM photograph (magnification = 300 times), and the right figure is a cross-sectional SEM photograph (magnification = 3500 times).

The left figure shows the surface of the protective film in the right SEM photograph (that is, the surface of the protective film having a thickness. In the right SEM picture, the upper layer having a thickness of about 2 cm is a resin layer). It corresponds to the enlarged one. As shown in the left figure, the particle diameters of CoFe ₂ O ₄ particles are uniform, and the particles are evenly or almost uniformly distributed. The right figure is a cross-sectional SEM photograph. As shown in the right figure, the protective film is formed homogeneously or almost uniformly.

The figure explaining the example of an aspect of a support membrane type flat SOFC cell The figure which shows the structural example which laminates the support membrane type flat SOFC cell The figure explaining the aspect which provides the protective film of electroconductive materials, such as electroconductive ceramics, on the Cr alloy surface <SEM photograph of the surface and cross section of the sample in <SEM observation 1 of each sample produced in Experimental Example 1> Surface SEM photograph and cross-sectional SEM photograph (drawing substitute photograph) of the sample in <SEM observation 2 of each sample prepared in Experimental Example 1> Surface SEM photograph and cross-sectional SEM photograph (drawing substitute photograph) of the sample in <SEM observation 3 of each sample produced in Experimental Example 1> Surface SEM photograph and cross-sectional SEM photograph (drawing substitute photograph) of the sample in <Observation of sample produced in Experimental Example 2 by SEM>

Explanation of symbols

1 cell 2 anode (fuel electrode)
3 Electrolyte membrane 4 Cathode (air electrode)
5 Interconnector 6 Conductive material coating layer

Claims (9)

  A method of coating a protective film made of a conductive ceramic material on a solid oxide fuel cell interconnector composed of a heat-resistant alloy material containing Cr, wherein a low-temperature sintering aid is added to the conductive ceramic material After the applied slurry is applied to the surface of the heat-resistant alloy material containing Cr, reduction treatment is performed at 700 to 900 ° C., and then firing is performed at 750 to 850 ° C. in an air atmosphere. Coating method of protective film for interconnector. 2. The conductive ceramic material according to claim 1, wherein the conductive ceramic material is MnCo ₂ O ₄ , Mn _1.5 Co _1.5 O ₄ , CoMn ₂ O ₄ , MnFe ₂ O ₄ , ZnMn ₂ O ₄ , Cu _1.4 Mn _1.6 O ₄ or CoFe ₂ O ₄ . A method of coating a protective film on an interconnector for a solid oxide fuel cell.   2. The method of coating a protective film on an interconnector for a solid oxide fuel cell according to claim 1, wherein the low-temperature sintering aid is a Li compound.   4. The method for coating a protective film on an interconnector for a solid oxide fuel cell according to claim 3, wherein the Li compound is lithium oxide, lithium hydroxide, lithium nitrate, lithium carbonate, lithium acetate or lithium halide. .   2. The solid oxide fuel cell according to claim 1, wherein the amount of the low-temperature sintering aid added to the conductive ceramic material is 3 to 8 mol% with respect to 100 mol% of the conductive ceramic material. Coating method of protective film for interconnector.   2. The method for coating a protective film on an interconnector for a solid oxide fuel cell according to claim 1, wherein the reducing atmosphere of the reduction treatment is a hydrogen-containing nitrogen atmosphere.   The method for coating a protective film on an interconnector for a solid oxide fuel cell according to claim 1, wherein the reducing atmosphere temperature of the reduction treatment is 750 to 850 ° C.   2. The method of coating a protective film on a solid oxide fuel cell interconnector according to claim 1, wherein the reduction treatment time is 12 to 24 hours. The method for coating a protective film on an interconnector for a solid oxide fuel cell according to claim 1, wherein the firing time in the air atmosphere is 12 to 24 hours.

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