JP2010277771A - Solid oxide fuel cell system and jointing material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solid oxide fuel cell (SOFC) system in which a gas tube for supplying gas to an electrode and unit cells are jointed for a long period with high airtightness and durability maintained, to provide a jointing material to be used for forming a jointing part having such a high airtightness and durability as above, and to provide a jointing method of the unit cells of the SOFC and the gas tube by using the above jointing material. <P>SOLUTION: The solid oxide fuel cell system 100 is provided with: an SOFC 10 having a fuel electrode 12, an air electrode 16, and a solid electrolyte 14; and a gas tube 20 which is jointed with the SOFC 10 and supplies gas. A jointing part 1 between the SOFC 10 and the gas tube 20 is formed of a jointing material composed of glass in which cristobalite crystal and/or leucite crystal are deposited in glass matrix. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a solid oxide fuel cell (SOFC) system, and more particularly, a joining material for joining a SOFC (single cell) and a gas pipe for supplying fuel gas or oxygen-containing gas to the SOFC, and The present invention relates to a bonding method using a bonding material, and an SOFC system including a connected SOFC and gas piping.

  A solid oxide fuel cell (hereinafter sometimes referred to simply as “SOFC”) is also called a third generation fuel cell, and has the following advantages over other fuel cells. There is. For example, in SOFC, since the operating temperature can be increased, a reaction accelerator (catalyst) is unnecessary, and the running cost is reduced. Further, by reusing the high-temperature exhaust gas (exhaust heat), the overall efficiency (total efficiency) can be increased. Furthermore, since the SOFC has a high output density, it can be miniaturized. From these facts, it is expected as a distributed power generation apparatus that replaces an internal combustion engine such as a steam turbine or a gas turbine.

As a basic structure (single cell), SOFC has a porous structure on one surface of a dense solid electrolyte (for example, a dense membrane layer) made of an oxygen ion conductor (typically an oxygen ion conductive ceramic body). An air electrode (cathode) is formed, and a fuel electrode (anode) having a porous structure is formed (for example, laminated) on the other surface. Fuel gas (typically H ₂ (hydrogen)) is supplied to the surface of the solid electrolyte on the side where the fuel electrode is formed, and O ₂ (oxygen) is supplied to the surface of the solid electrolyte on the side where the air electrode is formed. A gas containing (typically air) is supplied. Further, in order to supply such a gas to both electrodes of the SOFC, a gas pipe that connects the gas source and the SOFC and distributes the respective gases is connected to the SOFC.

  As a solid electrolyte for SOFC, a solid electrolyte made of a zirconia-based material (for example, yttria stabilized zirconia: YSZ) is widely used because of its high chemical stability and mechanical strength. As the solid electrolyte (layer) becomes thinner, the ion permeation rate increases and the battery performance such as charge / discharge characteristics is improved. As a result, in recent years, an anode-supported SOFC in which a solid electrolyte is formed in the form of a thin film on the surface of a porous substrate that functions as a fuel electrode for the purpose of thinning the solid electrolyte to improve the battery performance of the SOFC. Development is underway.

For example, a cermet of NiO and zirconia is often used as the fuel electrode, and an oxide having a perovskite structure such as LaCoO ₃ or LaMnO ₃ is often used as the air electrode. These SOFC constituent materials such as electrolyte materials and electrode materials take into consideration the temperature characteristics that the SOFC normally operates in a high temperature range of about 800 ° C. to 1200 ° C., and also provide chemical durability in an oxidizing / reducing atmosphere at high temperatures. Improvement and development of a more preferable SOFC component material are being promoted for the purpose of improving battery performance, with high electrical conductivity selected and also close thermal expansion coefficients.

  An example of the structure of an SOFC system provided with this kind of anode-supported SOFC is shown in FIGS. As schematically shown in FIGS. 1 and 2, the SOFC system 100 includes a porous fuel electrode 12 having a hollow box shape, and a dense solid electrolyte membrane 14 laminated on the outer surface of the fuel electrode 12. And an anode-supported SOFC 10 having a porous air electrode 16 laminated on the solid electrolyte membrane 14. The SOFC system 100 includes a gas pipe 20 for supplying fuel gas to the fuel electrode 12. Such a gas pipe 20 is provided on each of two opposing faces 13 and 15 of the outer surface of the hollow box-shaped fuel electrode 12 where the solid electrolyte membrane 14 and the air electrode 16 are not formed. One end of each of the two opposing surfaces 13 and 15 is bonded to each other (in FIG. 1 and FIG. 2, since two are connected to one opposing surface, a total of four). The gas pipe 20 is connected.

  The fuel gas supplied to the SOFC 10 flows into the hollow portion 11 (see FIG. 3) of the fuel electrode 12 through the gas tube 20 from the connection surface 13 of the fuel electrode 12 with the gas tube 20. The hollow portion 11 is, for example, a fuel gas flow path formed in parallel with the axial direction (gas flow direction) of the gas pipe 20 and has a hollow cylindrical shape (hollow shape) having a diameter approximately equal to the inner diameter of the gas pipe 20. Shaped fuel gas flow path. A part of the fuel gas supplied to the hollow portion 11 permeates (diffuses) through the porous fuel electrode 12 and contributes to charging / discharging in the SOFC 10, and the rest is a connection surface 15 with the other gas pipe 20. Is discharged through the gas pipe 20.

  The oxygen-containing gas (typically air) supplied to the air electrode 16 flows in the outer peripheral space of the SOFC 10 so as to contact the surface of the air electrode 16 opposite to the surface on the solid electrolyte membrane 14 side. Circulate. Further, the solid electrolyte membrane 14 and the air electrode 16 are formed on one of the surfaces different from the connection surfaces 13 and 15 of the fuel electrode 12 and include a set of SOFCs 10 (that is, single cells). It may be a configuration. Alternatively, as shown in FIGS. 1 and 2, the SOFC system 100 includes a solid electrolyte membrane 14 and an air electrode 16 on a pair of opposed surfaces of the fuel electrode 12 that are different from the connection surfaces 13 and 15. (That is, two solid electrolyte membranes 14 and two air electrodes 16 are formed on one fuel electrode), and two sets of SOFCs 10 (stacks).

  In recent years, SOFC has been put into practical use, and as a result of the improvement in SOFC battery performance (power generation performance) with the thinning of the solid electrolyte and the improvement of the SOFC constituent materials as described above, there has been no problem in the past. Has come to influence the operating characteristics of SOFC. The main thing of such an element can be caused by a gas leak in SOFC (for example, a gas leak at a junction between a single cell and a gas pipe or an interconnector connecting a single cell to a single cell). is there. For example, the fuel gas utilization efficiency is reduced due to such a gas leak, and local heat distribution unevenness occurs. An SOFC having such a structure that may cause a poor airtightness is not preferable for practical long-term use, and it is a major problem to prevent the occurrence of gas leakage and improve the airtightness (sealability) of the joint in the SOFC. It has become.

  Here, various bonding materials that can be adapted to the objects to be bonded have been proposed as bonding materials for bonding portions in SOFC. For example, as shown in Patent Documents 1 to 4, as a material for joining a solid electrolyte and an interconnector (also referred to as a separator), a joining material mainly composed of stabilized zirconia, spinel, or the like, or stabilized zirconia A mixture of a ceramic body and glass or a mixture of metal and glass has been proposed. Patent Document 5 proposes a method of joining an insulating barrier layer made of amorphous ceramic between a metal frame constituting an SOFC and an electrolyte layer with a brazing material. Further, Patent Document 6 proposes a method of joining two alloy foil plates each having an electrode and a gas introduction / derivation hole and enclosing the entire cell. Patent Document 7 proposes a glass joined body that joins a joint between a solid electrolyte and an insulating member in a Na / S battery.

Japanese Patent Laid-Open No. 11-154525 JP 2004-39573 A Special table 2008-527680 Special table 2008-529256 JP 2005-190862 A Japanese Patent No. 4184139 JP-A-11-307118

  By the way, in a conventional SOFC provided with a solid electrolyte (for example, made of YSZ) having a thickness of 0.5 mm or more, for example, as a general method for joining the SOFC and a gas pipe, mainly the operating temperature of the SOFC ( For example, a glass or metal material that can have flexibility under a temperature of 700 ° C. to 1000 ° C. is used as a bonding material, and the bonding material is interposed between a gas pipe (for example, a dense tubular member made of YSZ) and the solid electrolyte. It was inserted, pressurized and joined (sealed). Alternatively, using such an electrolyte and a gas pipe being the same material, a slurry (paste-like composition) such as zirconia, which is the same material as the electrolyte and the gas pipe, is applied to the joint portion, Diffusion bonding was performed by firing.

On the other hand, since the anode supported SOFC as described above typically uses a solid electrolyte membrane having a thickness of 50 μm or less, the conventional pressure sealing method as described above is used to join the electrolyte membrane and the gas pipe. Then, there is a possibility that the strength of the joint portion cannot be obtained, which is not suitable. Further, since the fuel electrode (anode) is exposed to the reducing atmosphere by contact with the fuel gas, the pressure seal portion (joint portion) is caused by the generation of stress accompanying the volume change (typically expansion) of the fuel electrode. Since a load is easily applied, a gas leak may occur at such a joint. It is also difficult to diffusely bond the solid electrolyte membrane and the gas pipe through the same material because the solid electrolyte membrane is very thin.
Therefore, in an SOFC equipped with a solid electrolyte with a small film thickness, such as an anode-supported SOFC, the strength (durability) and airtightness that can sufficiently withstand practical use at the joint between the SOFC and the gas pipe ( It has been desired to form a joint that can realize (sealability).

  The present invention has been made in view of such a point, and the object thereof is to provide a gas pipe for supplying gas to an electrode and a single cell with high airtightness and durability over a long period of time even under a high operating temperature range. It is intended to provide a solid oxide fuel cell system that is held and joined over a wide area. Moreover, it is providing the joining material used in order to form the junction part which has such high airtightness and durability. It is another object of the present invention to provide a method for joining a single cell of SOFC and a gas pipe using such a joining material.

In order to achieve the above object, a fuel cell system provided by the present invention includes a solid oxide fuel cell (SOFC) including a fuel electrode (anode), an air electrode (cathode), and a solid electrolyte, and the solid material. A solid oxide fuel cell (SOFC) system comprising: a gas pipe joined to the oxide fuel cell to supply gas to the solid oxide fuel cell. In such a system, the joint between the solid oxide fuel cell and the gas pipe is formed by a joining material made of glass, characterized in that cristobalite crystals and / or leucite crystals are precipitated in a glass matrix. Has been. Here, “fuel cell (specifically, SOFC)” is a term including a single cell having a fuel electrode, an air electrode, and a solid electrolyte as constituent elements, and a so-called stack including a plurality of such single cells.
In the solid oxide fuel cell system according to the present invention, a cristobalite crystal (SiO ₂ ) and / or a leucite crystal (KAlSi ₂ O ₆ ) is precipitated in the glass matrix at the joint between the SOFC and the gas pipe. It is formed of a bonding material made of glass (hereinafter sometimes referred to as “crystal-containing glass”). Such a bonding material hardly flows in a temperature range of 800 ° C. or higher, for example, a temperature range of 800 ° C. to 1000 ° C. Therefore, according to the SOFC system, even if the use temperature of the SOFC reaches the temperature range, there is no possibility that the joint portion between the SOFC and the gas pipe is eluted. On the other hand, since the bonding material has flexibility in such a temperature range, the stress can be relieved even when a stress is generated in the bonded portion. Therefore, the SOFC system according to the present invention can realize a joint with improved mechanical strength.

In a preferable aspect of the solid oxide fuel cell system disclosed herein, the joint includes SiO ₂ , Al ₂ O ₃ , Na ₂ O, and K ₂ O as essential constituent elements, preferably additional constituent elements. As a crystal-containing glass containing at least one of MgO, CaO, and B ₂ O ₃ . Particularly preferably, the following composition with a mass ratio in terms of oxide:
SiO ₂ 60 to 75 wt%;
Al ₂ O ₃ 10~20% by weight;
Na ₂ O 3-15% by mass;
K ₂ O 5-15% by mass;
MgO 0 to 3% by mass;
CaO 0 to 3% by mass;
B ₂ O _{30 to} 3% by mass;
Is substantially composed of.
The joint portion having such a composition may have a thermal expansion coefficient that approximates the thermal expansion coefficient (thermal expansion coefficient) of the SOFC to be bonded (for example, the solid electrolyte of the SOFC) and the gas pipe. For this reason, the SOFC of the SOFC system disclosed here is repeatedly used in a high temperature range (for example, 700 ° C. to 1000 ° C.), and the temperature rise and fall between the use temperature range and the temperature when not used (room temperature) Even if it repeats, the leak of the gas from the said junction part (sealing part) can be prevented, and high airtightness can be maintained over a long period of time. Further, battery performance can be improved by preventing gas leakage. Therefore, the fuel cell system having such a configuration can realize a high-performance SOFC system having excellent heat resistance and battery characteristics.

In another preferable aspect of the solid oxide fuel cell system disclosed herein, the solid electrolyte and the gas pipe are made of a zirconia-based oxide. More preferably, the junction is formed so as to close the gap between the solid electrolyte and the gas pipe.
In the SOFC system having such a configuration, since the solid electrolyte and the gas pipe are made of the same material, the bonding material formed from the crystal-containing glass is used to provide higher airtightness and mechanical strength. Thus, the gas pipe and the SOFC can be joined. Further, typically, a joint is formed so as to close a gap between the dense solid electrolyte and the gas pipe, thereby connecting the SOFC and the gas pipe with high airtightness and mechanical strength. be able to. Therefore, the fuel cell system having such a configuration can realize a high-performance SOFC system having more excellent heat resistance and battery characteristics.

In a more preferable aspect of the solid oxide fuel cell system disclosed herein, the solid oxide fuel cell includes a fuel electrode and a film having a thickness of 100 μm or less formed on the surface of the fuel electrode. It has a laminated structure consisting of a solid electrolyte membrane supported by an electrode and an air electrode formed on the surface of the solid electrolyte membrane.
The bonding material made of crystal-containing glass disclosed here can be preferably applied to an SOFC having a multilayer structure including a thin-film solid electrolyte as described above (that is, an anode-supported SOFC). The SOFC and the gas pipe can be joined (sealed) with high airtightness and mechanical strength. Therefore, the SOFC system provided with such SOFC can realize a high-performance SOFC system having more excellent heat resistance and battery characteristics.

Moreover, this invention provides the bonding | jointing material which solves the said subject as another side surface. That is, it is a joining material for joining a solid oxide fuel cell and a gas pipe for supplying gas to the solid oxide fuel cell. The bonding material disclosed here includes SiO ₂ , Al ₂ O ₃ , Na ₂ O, and K ₂ O as essential constituent elements, and preferably at least one of MgO, CaO, and B ₂ O ₃ as additional constituent elements. It is formed from the crystal containing glass containing one. Particularly preferably, the following composition with a mass ratio in terms of oxide:
SiO ₂ 60 to 75 wt%;
Al ₂ O ₃ 10~20% by weight;
Na ₂ O 3-15% by mass;
K ₂ O 5-15% by mass;
MgO 0 to 3% by mass;
CaO 0 to 3% by mass;
B ₂ O _{30 to} 3% by mass;
The glass is substantially composed of a glass characterized in that cristobalite crystals and / or leucite crystals are precipitated in a matrix of the glass.
In a preferred embodiment, the paste is provided as a paste (slurry) bonding material (seal material) containing the crystal-containing glass as a main component.
By using the bonding material having such a configuration, the SOFC and the gas pipe can be bonded (sealed) with high airtightness and mechanical strength as described above, and excellent heat resistance and durability can be obtained. It is possible to provide a high-performance SOFC system including the above-described joint portion.

In one preferred embodiment of the bonding material described herein, are prepared as the coefficient of thermal expansion is ^{9 × 10 -6 / K~12 × 10} -6 / K.
Such a coefficient of thermal expansion (typically an average value between room temperature (25 ° C.) based on a general differential expansion method (TMA) and a temperature below the softening point of glass (for example, 450 ° C.)) is, for example, an electrode ( For example, it approximates the thermal expansion coefficient of a zirconia-based oxide (zirconia-based material) such as YSZ that can be suitably used as a fuel electrode material, a solid electrolyte material, or a gas pipe material. Therefore, by using the joining material having such a structure, the SOFC and the gas pipe can be joined (sealed) with higher airtightness and mechanical strength, and more excellent in heat resistance and durability. It is possible to provide a high-performance SOFC system provided with the above-described joint provided in the above.

The present invention also provides a method of joining a solid oxide fuel cell and a gas pipe for supplying gas to the solid oxide fuel cell. That is, any one of the bonding materials disclosed herein is prepared, the bonding material is applied to the connection portion between the solid oxide fuel cell and the gas pipe, and the applied bonding material is bonded to the bonding material. By firing at a temperature range in which the material does not flow out from the coated portion, a joint portion that blocks the gas flow composed of the joint material is formed at the connection portion between the solid oxide fuel cell and the gas pipe. .
Moreover, it is preferable to join the solid oxide fuel cell and the gas pipe so as to close a gap between the solid electrolyte and the gas pipe.
With the method having such a configuration, it is possible to provide a solid oxide fuel cell system that exhibits the above-described effects by firing the bonding material applied to the connection portion.
Therefore, as another aspect of the present invention, an SOFC (for example, a solid electrolyte made of zirconia-based oxide) and a gas pipe made of zirconia-based oxide, for example, using any of the bonding materials disclosed herein, A method for manufacturing an SOFC system, characterized in that bonding is performed by the above-described bonding method.

It is a perspective view showing typically one form of SOFC system provided with an anode support type solid oxide fuel cell (SOFC) and a gas pipe joined to the SOFC. It is a front view showing typically one form of SOFC system provided with anode supported SOFC and a gas pipe joined to SOFC. FIG. 3 is a cross-sectional view taken along line III-III in FIG. 2, schematically illustrating a configuration of a main part of the anode-supported SOFC system according to one embodiment. It is sectional drawing which shows typically the structure of the SOFC system provided with the anode support type SOFC which concerns on other embodiment, and the gas pipe joined to this SOFC. It is a perspective view showing typically one form of SOFC system provided with anode support type SOFC and a gas pipe joined to SOFC. It is sectional drawing which shows typically the structure of the joined body (sample) created in the Example.

  Hereinafter, preferred embodiments of the present invention will be described. In addition, matters other than the matters specifically mentioned in the present specification (for example, the method for preparing the crystal-containing glass constituting the bonding material) and the matters necessary for carrying out the present invention (the raw material powder mixing method and the single cell) And a stack construction method) can be grasped as a design matter of a person skilled in the art based on the prior art in this field. The present invention can be carried out based on the contents disclosed in this specification and common technical knowledge in the field.

  The solid oxide fuel cell system (SOFC system) according to the present invention has a joint between a solid oxide fuel cell (SOFC) constituting the system and a gas pipe for supplying gas to the SOFC. , Characterized in that it is formed by a bonding material comprising the above-mentioned crystal-containing glass in which cristobalite crystals and / or leucite crystals are precipitated in a glass matrix, and other constituents such as SOFC air electrode The composition and the shape of the gas pipe can be arbitrarily determined in light of various standards.

The bonding material disclosed here is a bonding material for bonding the SOFC and at least one gas pipe constituting the SOFC system to each other, and cristobalite (SiO ₂ ) crystals and / or leucite (KAlSi) in a glass matrix. ₂ O ₆ or 4SiO ₂ · Al ₂ O ₃ · K ₂ O) a glass composition (crystal-containing glass) having a composition capable of precipitating crystals.

First, the crystal-containing glass will be described.
When the SOFC system is used in a relatively high temperature range, for example, 700 ° C. to 1200 ° C., preferably 700 ° C. to 1000 ° C. (for example, 800 ° C. to 1000 ° C.), a crystal-containing glass suitable as a constituent component of the bonding material is A glass having a composition that hardly melts in a high temperature range is preferable. In this case, a desired high melting point (high softening point) can be realized by adding or increasing a component that increases the melting point (softening point) of the glass.
Such crystal-containing glass is preferably an oxide glass containing SiO ₂ , Al ₂ O ₃ , and K ₂ O as essential components. In addition to these essential components, various components (typically various oxide components) can be additionally contained depending on the purpose.
Moreover, the amount of cristobalite crystals and / or leucite crystals deposited can be appropriately adjusted depending on the content (composition ratio) of the essential constituents in the glass composition.
Is not particularly limited, the mass ratio of the oxide basis the total glass components (including cristobalite crystalline and / or leucite crystalline _portion), SiO 2: 60 to 75 _{wt%, Al} 2 O 3: _10~20 wt%, Na ₂ O: 3 to 15% by mass, K ₂ O: 5 to 15% by mass, MgO: 0 to 3% by mass, and CaO: 0 to 3% by mass (preferably 0.1 to 3% by mass) Is preferred.

SiO ₂ is a component constituting a cristobalite crystal and a leucite crystal, and is a main component constituting the skeleton of the glass layer (glass matrix) of the joint. If the SiO ₂ content is too high, the melting point (softening point) becomes too high, which is not preferable. On the other hand, if the SiO ₂ content is too low, the amount of cristobalite crystals and / or leucite crystals deposited is not preferred. In addition, water resistance and chemical resistance are reduced. Preferably SiO ₂ content of from 60 to 75% by weight of the total glass composition, and particularly preferably about 65 to 75 wt%.

Al ₂ O ₃ is a component constituting a leucite crystal, and is a component involved in adhesion stability by controlling the fluidity of glass. If the Al ₂ O ₃ content is too low, the adhesion stability is lowered, which may impair the formation of a glass layer (glass matrix) having a uniform thickness, and the amount of leucite crystal precipitation decreases, which is not preferable. On the other hand, when the Al ₂ O ₃ content is too high, there is a possibility to reduce the chemical resistance of the joint. It is preferable al ₂ O ₃ content is 10 to 20% by weight of the total glass composition.

K ₂ O is a component constituting the leucite crystal, and is a component that increases the coefficient of thermal expansion (thermal expansion coefficient) together with other alkali metal oxides (typically Na ₂ O). If the K ₂ O content is too low, the amount of leucite crystal precipitation is reduced, which is not preferable. Further, if the K ₂ O content and the Na ₂ O content are too low, the thermal expansion coefficient (thermal expansion coefficient) may be too low. On the other hand, if the K ₂ O content and the Na ₂ O content are too high, the thermal expansion coefficient (thermal expansion coefficient) becomes excessively high, which is not preferable. Preferably K ₂ O content is 5 to 15% by weight of the total glass composition, and particularly preferably about 9-11 wt%. Further, it is preferable (typically Na 2 _O) other alkali metal oxides is from 3 to 15 wt% content of the total glass composition. It is particularly preferable that the total of K ₂ O and Na ₂ O is 10 to 20% by mass of the entire glass composition.

  MgO and CaO, which are alkaline earth metal oxides, are optional additional components that can adjust the thermal expansion coefficient. CaO is a component that can increase the hardness of the glass layer (glass flux) and improve the wear resistance, and MgO is also a component that can adjust the viscosity during glass melting. Moreover, since a glass matrix is comprised by a multicomponent system by adding these components, chemical resistance can improve. The content of these oxides in the entire glass composition is preferably zero (no addition) or 3% by mass or less. For example, the total amount of MgO and CaO is preferably 2.5% by mass or less of the entire glass composition.

B ₂ O ₃ is also an optional additive component (may be 0% by mass). B ₂ O ₃ is considered to exhibit the same action as Al ₂ O ₃ in glass, and can contribute to the multi-componentization of the glass matrix. Moreover, it is a component which contributes to the improvement of the meltability at the time of bonding material preparation. On the other hand, too much of this component is not preferable because it causes a decrease in acid resistance. Content in the entire glass composition of B ₂ O ₃ is preferably about 0.1 to 3 wt%.

In addition to the oxide components described above, components that are not essential in the practice of the present invention (for example, ZnO, Li ₂ O, Bi ₂ O ₃ , SrO, SnO, SnO ₂ , CuO, Cu ₂ O, TiO ₂ , ZrO) ₂ , La ₂ O ₃ ) can be added according to various purposes.
Preferably, the above-mentioned components are blended so that the thermal expansion coefficient of the bonding material approximates the thermal expansion coefficient of the object to be bonded (for example, the gas electrode and the SOFC fuel electrode and / or the solid electrolyte). To prepare. For example, the gas pipe and the solid electrolyte are formed of a dense body of zirconia-based oxide such as YSZ, and the SOFC and the gas pipe are joined (sealed) so as to block between the dense gas pipe and the solid electrolyte. In this case, the thermal expansion coefficient is approximated to the thermal expansion coefficient of the zirconia-based oxide (from room temperature (25 ° C.) based on the differential expansion method (TMA) to (below the softening point of glass (for example, 450 ° C.)). The above-mentioned crystal-containing glass may be prepared by adjusting the composition so that the average value thereof is 9 × 10 ⁻⁶ / K to 12 × 10 ⁻⁶ / K.

Next, the manufacturing method of a joining material is demonstrated.
There is no particular limitation on the method for producing the bonding material having the above composition, and it is the same as that for producing a conventional crystal-containing glass (that is, a glass composition having a composition capable of depositing cristobalite crystals and / or leucite crystals). The method is used. Typically, compounds for obtaining various oxide components constituting the composition (for example, industrial products, reagents, various minerals containing oxides, carbonates, nitrates, complex oxides, etc., containing each component) Raw materials) and other additives as required are charged into a mixer such as a dry or wet ball mill at a predetermined blending ratio and mixed for several to several tens of hours. The admixture (powder) thus obtained is dried, placed in a refractory crucible, and heated and melted under suitable high temperature (typically 1000 ° C. to 1500 ° C.) conditions.

Next, the obtained glass is crushed and subjected to crystallization heat treatment. For example, the glass powder is heated from room temperature to about 100 ° C. at a temperature rising rate of about 1 to 5 ° C./min, and kept in a temperature range of 800 ° C. to 1000 ° C. for about 30 minutes to 60 minutes. Cristobalite crystals and / or leucite crystals can be precipitated.
The crystal-containing glass thus obtained can be formed into a desired form by various methods. For example, a powdery glass composition (crystal-containing glass) having a desired average particle size (for example, 0.1 μm to 10 μm) can be obtained by pulverizing with a ball mill or appropriately sieving.

An appropriate amount of water is added to the powdery glass composition thus obtained and mixed using a ball mill similar to the above. Then, the powdery joining material which concerns on this invention can be obtained by implementing the drying process for predetermined time.
The powdery bonding material thus obtained is typically prepared in the form of a paste, like the conventional bonding material, and can be applied to the connection portion (bonded portion) to be bonded. For example, a paste can be prepared by mixing an appropriate binder or solvent with the obtained bonding material. In addition, the binder, solvent, and other components (for example, dispersant) used in the paste are not particularly limited, and can be appropriately selected from conventionally known ones in paste production.
For example, a suitable example of the binder includes cellulose or a derivative thereof. Specific examples include hydroxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxypropyl methyl cellulose, carboxymethyl cellulose, carboxyethyl cellulose, carboxyethyl methyl cellulose, cellulose, ethyl cellulose, methyl cellulose, ethyl hydroxyethyl cellulose, and salts thereof. It is preferable that a binder is contained in 5-20 mass% of the whole paste.

  Examples of the solvent that can be contained in the paste include ether solvents, ester solvents, ketone solvents, and other organic solvents. Preferable examples include ethylene glycol and diethylene glycol derivatives, high-boiling organic solvents such as toluene, xylene and terpineol, or combinations of two or more thereof. Although the content rate of the solvent in a paste is not specifically limited, About 1-40 mass% of the whole paste is preferable.

  The bonding material disclosed here can be used in the same manner as a conventional bonding material of this type. Specifically, the SOFC (for example, solid electrolyte and / or fuel electrode) to be joined and the part to be joined of the gas pipe are contacted and connected to each other, and a joining material prepared in a paste form is applied to the connected part. To do. Then, the coated material is dried at an appropriate temperature (typically 60 ° C. to 100 ° C., for example, 80 ° C. ± 10 ° C.). Next, a temperature range that is preferably equal to or higher than the operating temperature range of SOFC (for example, 700 ° C. to 1000 ° C. or higher temperature range, for example, 800 ° C. to 1200 ° C.), and the glass does not flow out. (For example, when the use temperature range is 700 ° C. to 1000 ° C., typically, it is 800 ° C. to 1200 ° C., and when the use temperature range is approximately 1200 ° C., it is typically fired at 1200 ° C. to 1300 ° C.). As a result, a joint portion (seal portion) that cuts off gas flow (that is, has no gas leak) at the connection (connection) portion between the SOFC and the gas pipe is formed. For example, the SOFC and the gas pipe are bonded by applying the bonding material so that a gap that may be generated between the dense solid electrolyte and the gas pipe in the SOFC is closed. In the joint formed in this way, gas (for example, fuel gas) flowing through the gas pipe is supplied to the SOFC without leaking. Further, such a bonding material exhibits flexibility in the operating temperature range of the SOFC, so that, for example, even when stress can be generated in the bonded portion due to reduction expansion associated with the contact with the fuel gas, the air tightness and durability of the bonded portion. Sex can be kept high.

The SOFC and gas pipe to which the bonding material disclosed herein can be preferably applied will be described.
Such a bonding material may be an SOFC having various structures (for example, a conventionally known flat plate type, cylindrical type, or a flat tubular type in which the peripheral side surface of the cylinder is vertically crushed). It can be preferably applied to the present invention and is not particularly limited to the shape or size of the SOFC. Such a bonding material can be preferably bonded even to a bonding target that is difficult to be bonded by pressure sealing or diffusion bonding due to, for example, insufficient strength. Therefore, for example, a thin film (for example, a film) The present invention can also be suitably applied to an anode-supported SOFC having a structure including a solid electrolyte formed in a thickness of 100 μm or less. The SOFC disclosed herein will be described in detail below using an anode-supported SOFC as an example, although it is not intended to limit the present invention.

The solid electrolyte provided in the SOFC disclosed herein is composed of a material that can form a dense layer having high oxygen ion conductivity and no gas permeability in both an oxidizing (air) atmosphere and a reducing (fuel gas) atmosphere. In particular, a solid electrolyte made of a zirconia-based oxide is preferable. As such a zirconia-based oxide, zirconia (YSZ) stabilized with yttria (Y ₂ O ₃ ) is typically used. Other examples include zirconia (CSZ) stabilized with calcia (CaO) and zirconia (SSZ) stabilized with scandia (Sc ₂ O ₃ ).

The fuel electrode and the air electrode provided in the SOFC disclosed here may be the same as those of the conventional SOFC, and are not particularly limited. For example, nickel (Ni) and YSZ cermets, ruthenium (Ru) and YSZ cermets, and the like are preferably used as the fuel electrode. As the air electrode, a lanthanum cobaltate (LaCoO ₃ ) -based or lanthanum manganate (LaMnO ₃ ) -based perovskite oxide is preferably employed. It is preferable to use a porous body made of these materials as a fuel electrode and an air electrode, respectively.

The manufacturing of the SOFC single cell and the stack disclosed herein may be based on the manufacturing of the conventional SOFC single cell and stack, and no special processing is required to construct the SOFC of the present invention. A solid electrolyte, a fuel electrode and an air electrode can be formed by various methods conventionally used.
For example, when an anode-supported SOFC is constructed, it is performed as follows. First, a fuel electrode that can function as a support base (support) is manufactured. First, a slurry-like molding material for a fuel electrode made of a predetermined cermet material (for example, a YSZ powder having an average particle diameter of about 0.1 μm to 10 μm, a NiO powder having an average particle diameter of about 1 μm to 10 μm, a binder, a dispersant, a solvent) Prepare. Next, using this molding material, a fuel electrode molded body is produced by, for example, extrusion molding. Here, the shape of the fuel electrode molded body may be a sheet shape (or flat plate shape), a hollow box shape having a hollow portion (gas flow path) for allowing fuel gas to flow into the fuel electrode, or a hollow flat shape. The shape (flat tubular shape) is preferable.

  Next, a solid electrolyte material is prepared. That is, a predetermined material (for example, a YSZ powder having an average particle size of about 0.1 μm to 10 μm, a binder, a dispersant, and a solvent) is mixed to prepare a molding material for a slurry (paste) solid electrolyte. The solid electrolyte molding material is printed and molded on the fuel electrode molded body at a film thickness of 100 μm or less (typically 1 μm to 100 μm, preferably 10 μm to 100 μm, for example 10 μm to 50 μm). An electrolyte membrane is formed. The solid electrolyte membrane supported by the fuel electrode molded body is dried and then fired in the air at a firing temperature of 1200 ° C. to 1400 ° C. As a result, a fired body in which a dense solid electrolyte membrane is formed on the porous fuel electrode is obtained.

Next, an air electrode material is prepared. That is, a slurry-like molding material for an air electrode made of a predetermined material (for example, LaSrO ₃ powder having an average particle diameter of about 1 μm to 10 μm, a binder, a dispersant, and a solvent) is prepared. By printing and molding the molding material for an air electrode on the surface of the solid electrolyte membrane obtained after firing at a film thickness of 100 μm or less (typically 1 μm to 100 μm, preferably 10 μm to 100 μm, for example, 10 μm to 50 μm). An unfired air electrode layer (film) is formed. This is dried and then fired in the air at a firing temperature of 1000 ° C. to 1200 ° C. Thus, a porous air electrode is formed on the solid electrolyte membrane, and an anode-supported SOFC (single cell) having a laminated structure including the fuel electrode, the solid electrolyte membrane, and the air electrode is manufactured.

  A gas pipe joined to the SOFC to be connected to the SOFC as described above may be the same as a conventional gas pipe used for supplying gas to the SOFC, and is not particularly limited. For example, a gas pipe made of a dense body of zirconia-based oxide such as YSZ, which is the same material as the solid electrolyte, is easily joined to the solid electrolyte by the joining material, and can be suitably used. The shape and size of the gas pipe are appropriately set according to the size of the SOFC to be connected and the size of the joint portion.

  The method for manufacturing the gas pipe may be the same as the method for manufacturing a conventional gas pipe for supplying gas to the SOFC, and is not particularly limited. For example, a slurry-like molding material for a gas pipe made of a predetermined material (for example, a YSZ powder having an average particle diameter of about 0.1 μm to 10 μm, a binder, a dispersant, and a solvent) is prepared. Then, using this molding material, it is molded into a tube of a predetermined size by, for example, extrusion molding. The obtained molded body can be fired in an appropriate temperature range (for example, 1300 ° C. to 1600 ° C.) in the atmosphere to produce a tubular gas tube. Further, a commercially available gas pipe for SOFC may be used.

Then, the solid oxide fuel cell system according to the present invention can be manufactured by bonding and connecting the manufactured SOFC and the gas pipe using the bonding material disclosed herein.
A preferred example of the present invention applied to the SOFC system having the configuration shown in FIGS. 1 and 2 will be described below. 3 is a cross-sectional view taken along the line III-III in FIG. 2, and schematically shows a configuration of a main part of the SOFC system shown in FIG. 1 to which the present invention is applied. FIG. 4 is a cross-sectional view schematically showing an SOFC system 110 including an anode-supported SOFC 40 and a gas pipe 50 according to another embodiment. In these drawings, the same reference numerals are given to members / parts having the same action, but the dimensional relationships (length, width, thickness, etc.) in the drawings do not reflect actual dimensional relationships.

  In the SOFC system 100 having the configuration shown in FIGS. 1 and 2 as described above, the bonding material 1 made of the crystal-containing glass is connected to one connecting surface 13 of the fuel electrode 12 and a gas as shown in FIG. The end surface 21 of the tube 20 is brought into contact with each other, and the surfaces are provided so as to join each other. In addition to this, the bonding material 1 extends beyond the contact surface (bonding surface) between the connecting surface 13 and the end surface 21 of the gas pipe 20 to the end of the solid electrolyte membrane 14. The porous fuel electrode 12 portion (which is provided and can be exposed between the gas pipe 20 and the solid electrolyte membrane 14 by closing the gap between the dense gas pipe 20 and the dense solid electrolyte membrane 14 with the bonding material 1). It is preferably applied so as to cover the end portion). The same applies to the other connection surface 15 of the fuel electrode 12 and the end surface 23 of the gas pipe 20. By providing the bonding material 1 in this way, a gap that can be generated between the dense solid electrolyte membrane 14 and the gas pipe 20 (that is, a part of the porous fuel electrode 12 that can be exposed) is completely formed by the bonding material 1. The gas pipe 20 and the SOFC 10 can be joined and connected in such a state that the gas pipe 20 is blocked. Since the joint 1 formed by such joining has high hermeticity and strength, the SOFC system 100 is an SOFC with excellent battery performance that is preferably prevented from gas leakage and has high durability and battery characteristics. A system can be realized.

  As another preferred example of the SOFC system according to the present invention, as shown in FIG. 4, for example, an SOFC system 110 having a hollow box-shaped porous insulating support substrate may be used. This SOFC system 110 is an insulating support base material made of a porous material such as zirconia-based oxide or magnesia, for example, and has a hollow box-type support base material 30 provided with a flow path for flowing fuel gas. A fuel electrode layer 42 formed on a pair of opposing surfaces of the support substrate, a solid electrolyte membrane 44 laminated on the fuel electrode layer 42, and air laminated on the solid electrolyte membrane 44 And an SOFC 40 composed of the polar layer 46. Further, the SOFC system 110 includes a gas pipe 50 that is in contact with and joined to a pair of end surfaces of the support base material 30 of the SOFC 40. In the SOFC system 110 having such a configuration, as shown in FIG. 4, the bonding material 1 made of the crystal-containing glass is bonded to the contact surfaces of the gas pipe 50 and the end surface of the support base 30. To the end of the solid electrolyte membrane 44 beyond the contact surface (joint surface), and the gap between the dense gas pipe 50 and the dense solid electrolyte membrane 44 is blocked. The porous support base material 30 portion (typically the end portion) that can be exposed between the gas pipe 50 and the solid electrolyte membrane 44 and the porous fuel electrode layer 42 portion are applied. It is preferable. As a result, even in the SOFC system 110 in which the gas pipe 50 is connected to the support base material 30, a gap that may be generated between the gas pipe 50 and the solid electrolyte membrane 44 is completely closed by the bonding material 1. In such a state, the SOFC 40 and the gas pipe 50 can be joined and connected.

As mentioned above, although preferred embodiment of the SOFC system based on this invention was shown and demonstrated to FIGS. 1-4, it is not limited to these. Another preferred example of the SOFC system may be a SOFC system 120 having a fuel electrode 62 having a flat rectangular tube shape, as shown in FIG. In such a system 120, the entire interior of the rectangular cylindrical fuel electrode 62 is a fuel gas flow channel 61, and a gas pipe 70 is joined to the fuel electrode 62 in accordance with the shape of the flow channel 61. Such a configuration in which the fuel gas supplied from the gas pipe 70 can flow through the entire interior of the fuel electrode 62 is preferable because the contact efficiency between the fuel gas and the fuel electrode 62 is improved.
Further, as shown in FIG. 5, a solid electrolyte membrane 64 formed in a predetermined area on one or two surfaces (typically a pair of surfaces facing each other) of one fuel electrode 62 and the solid electrolyte By arranging a plurality of laminated bodies (typically rectangular shapes) composed of air electrodes 66 laminated on the membrane 64 so as to be parallel to the axial direction (gas flow direction) of the gas pipe 70, The SOFC system 120 including a stack in which a plurality of SOFCs 60 are arranged in parallel with the fuel gas flow direction is preferably provided.

  Hereinafter, examples related to the present invention will be described with reference to FIG. 6, but the present invention is not intended to be limited to those shown in the following examples.

<Production of anode supported SOFC (single cell)>
3-8 mol% yttria stabilized zirconia (YSZ) powder (average particle size: about 1 μm) and nickel oxide (NiO) powder common binder (here, polyvinyl alcohol (PVA) was used), and solvent (here. Then, water was added and kneaded. Next, the kneaded product (slurry or paste-like fuel electrode molding material) was subjected to sheet molding to obtain a disk-shaped fuel electrode molded body having a diameter of about 20 mm and a thickness of about 1 mm.
Next, the same binder, dispersant and solvent as above were added to 3-8 mol% YSZ powder (average particle size: about 1 μm) and kneaded. Next, this kneaded product (a paste-form molding material for a solid electrolyte membrane) was printed and formed on the fuel electrode molded body into a disk shape having a diameter of 16 mm and a thickness of 10 μm to 30 μm. The unfired laminate comprising the fuel electrode compact and the solid electrolyte membrane supported on the compact was dried and then fired in the air at a firing temperature of 1200 ° C to 1400 ° C.
Next, a general binder (here, ethyl cellulose was used) and a solvent (here, terpineol was used) were added to and kneaded with LaSrO ₃ powder (average particle size: about 1 μm). Next, this kneaded product (a paste-like molding material for an air electrode) was printed and formed on the solid electrolyte membrane into a disk shape having a diameter of 13 mm and a thickness of 10 μm to 30 μm. Subsequently, it baked in air | atmosphere at the calcination temperature of 1000 to 1200 degreeC. In this manner, an anode supported SOFC 80 composed of the fuel electrode 82, the solid electrolyte membrane 84, and the air electrode 86 as shown in FIG.

<Production of gas pipe>
The same binder, dispersant, and solvent as above were added to 3-8 mol% YSZ powder (average particle size: about 1 μm) and kneaded to prepare a slurry or paste-like molding material for a gas pipe. Next, the molding material was molded into a tubular shape by extrusion molding or the like. The obtained molded body was fired at 1300 ° C. to 1600 ° C. in the atmosphere to produce two tubular gas pipes 92 and 94 (see FIG. 6).

<Production of paste-like bonding material>
SiO ₂ powder, Al ₂ O ₃ powder, Na ₂ CO ₃ powder, K ₂ CO ₃ powder, MgCO ₃ powder, CaCO ₃ powder and B ₂ O ₃ powder having an average particle diameter of about 1 μm to 10 μm are respectively mixing ratio, i.e. _SiO 2 in terms of oxide; 60 to 75 _{wt%, Al} 2 O 3; _{10~20 wt%,} Na 2 O; 3 to 15 _{wt%, K} 2 O 3; _5~15 wt%, MgO 0 to 3% by mass; CaO; 0 to 3% by mass; B ₂ O ₃ ; 0 to 3% by mass; mixed raw material powders having different compositions of a total of six types of crystals (samples 1 to 6). Prepared. The composition of the crystal-containing glass according to each sample 1 to 6 is shown in Table 1.
Subsequently, the raw material powders according to Samples 1 to 6 were melted in a temperature range of 1000 ° C. to 1500 ° C. (here, 1450 ° C.) to form glass. Thereafter, glass other than sample 6 was pulverized, and crystallization heat treatment was performed in a temperature range of 800 ° C. to 1000 ° C. (here, 850 ° C.) for 30 minutes to 60 minutes. Thereby, in samples 1 to 5, cristobalite crystals and / or leucite crystals were precipitated so as to be dispersed in the glass matrix. Thereafter, the obtained crystal-containing glass was pulverized and classified to obtain a powdery crystal-containing glass having an average particle diameter of about 2 μm. Note that, as described above, the sample 6 is a glass having the same composition as the sample 2 and obtained without performing the crystallization heat treatment.
Next, 40 parts by mass of glass powder (samples 1 to 6) were mixed with 3 parts by mass of a general binder (here, ethyl cellulose was used) and 47 parts by mass of a solvent (here, terpineol was used). A total of six types of paste-like bonding materials corresponding to samples 1 to 6 in Table 1 were produced.

<Joint treatment>
The above 6 types of pastes (Samples 1 to 6) were each used as a bonding material for bonding treatment. Specifically, as shown in FIG. 6, gas pipes 92 and 94 are arranged on both sides of the anode-supported SOFC 80 produced as described above, and the solid electrolyte membrane 84 and the gas in the SOFC 80 sandwiched between the gas pipes 92 and 94. The joining material (each sample 1-6) was apply | coated so that the clearance gap between each with the pipes 92 and 94 might be plugged up. After drying this at 80 degreeC, it hold | maintained (baking) for 1 hour in the temperature range of 800 to 1000 degreeC in air | atmosphere. Thereby, gas pipes 92 and 94 and SOFC80 were joined.
Here, in the above samples 1 to 5, the elution of the joint portion 96 was not observed after cooling at room temperature. However, in sample 6 which is a bonding material not subjected to crystallization heat treatment, elution at the bonding portion 96 was observed.

Here, the coefficient of thermal expansion of the joint portion 96 obtained using the paste-like joining materials of Samples 1 to 6 (however, an average value between room temperature (25 ° C.) and 450 ° C. based on the differential expansion method (TMA)) ) Was measured. For joints 96 according to the sample 1-4, as shown in Table 1, were in the range of either ^{9 × 10 -6 / K~12 × 10} -6 / K. Further, a dense and crack-free joint surface was observed. On the other hand, the thermal expansion coefficient of the joint portion 96 obtained using the sample 5 exceeded 12 × 10 ⁻⁶ / K. Further, the thermal expansion coefficient of the joint portion 96 obtained using the sample 6 was lower than 9 × 10 ⁻⁶ / K. Moreover, about the samples 5 and 6, the crack was observed in the surface in any junction part.
The thermal expansion coefficient of the YSZ solid electrolyte membrane 84 and the YSZ gas pipes 92 and 94 used here under the same conditions was 10.2 × 10 ⁻⁶ / K. The thermal expansion coefficient of the thin plate interconnector equivalent member made of the lanthanum calcia chromite used here was 9.7 × 10 ⁻⁶ / K.

<Gas leak test>
Next, a leak test for confirming the presence or absence of a gas leak from the joint portion 96 of the specimen of the SOFC system in which the gas pipes 92 and 94 and the SOFC 80 are joined using the total of six types (samples 1 to 6) constructed as described above. Went. Specifically, first, the sample of the SOFC system provided with the sample 1 is heated to 800 ° C., and the hydrogen-containing gas (hydrogen) from the gas tube 94 side toward the fuel electrode 82 under such temperature conditions. The fuel electrode 82 was reduced by supplying (H ₂ ) gas 3% by volume and nitrogen (N ₂ ) gas 97% by volume) for 1 hour. Next, air is supplied from the gas pipe 92 side to the specimen at a flow rate of 100 mL / min under a pressure of 0.2 Pa, and helium (He) gas as a fuel gas is supplied from the gas pipe 94 side under a pressure of 0.2 Pa. The sample was supplied at a flow rate of 100 mL / min. Gas chromatography to measure the composition of the He gas from the fuel electrode 82 side (i.e. the gas pipe 94 side) from the amount of N ₂ gas contained in the He gas, N ₂ in the air from the joint 96 leaks Evaluated whether or not. A leak test was conducted in the same manner for Samples 2-6.
The evaluation results of gas leak are shown in Table 1. In Table 1, those having a leak rate of N ₂ gas (volume content of N ₂ gas contained in He exhaust gas) of 1% or less are indicated as “none” and have practical airtightness It was. As shown in Table 1, it was found that the gas leakage was preferably prevented in the joint portion 96 obtained using the samples 1 to 4, and the gas tightness was excellent.

  As described above, according to the present embodiment, using a bonding material made of crystal-containing glass, the SOFC and the gas pipe are sealed between the zirconia-based solid electrolyte membrane and the gas pipe made of the same material as the electrolyte membrane. By joining and connecting, it was possible to join (that is, form a joint) while ensuring sufficient airtightness without causing gas leakage. Therefore, a suitable SOFC (single cell, stack) system having excellent mechanical strength and airtightness can be provided.

1 Bonding material (bonding part)
10 Solid oxide fuel cell (SOFC)
12 Fuel Electrode 14 Solid Electrolyte Membrane 16 Air Electrode 20 Gas Pipe 30 Support Base 40 Solid Oxide Fuel Cell (SOFC)
42 Fuel Electrode Layer 44 Solid Electrolyte Membrane 46 Air Electrode Layer 50 Gas Pipe 60 Solid Oxide Fuel Cell (SOFC)
62 Fuel electrode 64 Solid electrolyte membrane 66 Air electrode 70 Gas pipe 80 Solid oxide fuel cell (SOFC)
82 Fuel Electrode 84 Solid Electrolyte Membrane 86 Air Electrode 92,94 Gas Pipe 96 Junction 100,110,120 Solid Oxide Fuel Cell System

Claims (9)

A solid oxide fuel cell comprising a fuel electrode, an air electrode, and a solid electrolyte;
A gas pipe joined to the solid oxide fuel cell to supply gas to the solid oxide fuel cell;
A solid oxide fuel cell system comprising:
The joint between the solid oxide fuel cell and the gas pipe is formed by a joining material made of glass, characterized in that cristobalite crystals and / or leucite crystals are precipitated in a glass matrix. Solid oxide fuel cell system. The joint is
The following composition in mass ratio in terms of oxide:
SiO ₂ 60 to 75 wt%;
Al ₂ O ₃ 10~20% by weight;
Na ₂ O 3-15% by mass;
K ₂ O 5-15% by mass;
MgO 0 to 3% by mass;
CaO 0 to 3% by mass;
B ₂ O _{30 to} 3% by mass;
The solid oxide fuel cell system according to claim 1, substantially consisting of:   The solid oxide fuel cell system according to claim 1 or 2, wherein the solid electrolyte and the gas pipe are made of a zirconia-based oxide.   The solid oxide fuel cell system according to any one of claims 1 to 3, wherein the joint is formed so as to close a gap between the solid electrolyte and the gas pipe.   The solid oxide fuel cell includes a fuel electrode, a solid electrolyte membrane formed on the surface of the fuel electrode with a film thickness of 100 μm or less and supported by the fuel electrode, and formed on the surface of the solid electrolyte membrane. The solid oxide fuel cell system according to any one of claims 1 to 4, further comprising a laminated structure including a formed air electrode layer. A joining material for joining a solid oxide fuel cell and a gas pipe for supplying gas to the solid oxide fuel cell,
The following composition in mass ratio in terms of oxide:
SiO ₂ 60 to 75 wt%;
Al ₂ O ₃ 10~20% by weight;
Na ₂ O 3-15% by mass;
K ₂ O 5-15% by mass;
MgO 0 to 3% by mass;
CaO 0 to 3% by mass;
B ₂ O _{30 to} 3% by mass;
A bonding material comprising a glass substantially composed of the above, wherein cristobalite crystals and / or leucite crystals are precipitated in a matrix of the glass. As the bonding material, the thermal expansion coefficient is adjusted so that it would be ^{9 × 10 -6 / K~12 × 10} -6 / K, the bonding material according to claim 6. A joining method for joining a solid oxide fuel cell and a gas pipe for supplying gas to the solid oxide fuel cell,
Preparing a bonding material according to claim 6 or 7, and applying the bonding material to a connecting portion between a solid oxide fuel cell and a gas pipe;
By firing the applied bonding material in a temperature range in which the bonding material does not flow out of the applied portion, a gas made of the bonding material at the connection portion between the solid oxide fuel cell and the gas pipe Forming a junction that blocks distribution;
Including the method.   The joining method according to claim 8, wherein the solid oxide fuel cell and the gas pipe are joined so as to close a gap between the solid electrolyte and the gas pipe.

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