JP2006024436A - Solid electrolyte fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solid electrolyte fuel cell having a stable air electrode, and a wax material forming a joint part excellent in heat resistance, consequently, capable of maintaining a good power generating efficiency. <P>SOLUTION: The solid electrolyte fuel cell has a solid electrolyte layer 11 (made of ScSZ or the like), a fuel electrode 12 (made of Ni and ScSZ or the like), an air electrode 13, and joint part where at least a part of components are brazed. The air electrode 13 is made of an air electrode material shown by general formula: (A<SB>x</SB>B<SB>1-x</SB>)(C<SB>y</SB>D<SB>1-y</SB>)O<SB>3-δ</SB>, (wherein, A is La, Y, Sm, Gd, Pr, or Ca; B is Sr, Ba, or Ca; C is Mn, Co, Ni, or Ce; D is Fe or Mn; 0.4≤x≤1; 0≤y≤0.5), and at least a part of the joint part is made of a metallic wax material (containing 60 mass% or more of Ni). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a solid oxide fuel cell. More specifically, the present invention relates to a solid oxide fuel cell that has a stable air electrode and maintains good power generation efficiency even when brazing is performed in an atmosphere having a low oxygen partial pressure such as a vacuum atmosphere and an argon atmosphere. About. Further, as a brazing material used for brazing for forming a joint for the purpose of isolating a fuel gas flow path and a combustion-supporting gas flow path, a metal brazing material containing Ni having excellent heat resistance When is used, good power generation efficiency is maintained over a longer period.

  A flat plate type solid oxide fuel cell (hereinafter also referred to as “flat plate SOFC stack”) is formed by stacking a plurality of single cells (hereinafter also referred to as “SOFC”) using a separator. Is formed. In this flat plate type SOFC stack, a gas seal for isolating the flow path of the fuel gas supplied to the fuel electrode and the flow path of the combustion-supporting gas supplied to the air electrode is provided. The brazing material used for brazing is required to have heat resistance and the like. A glassy gas seal material may be used for the gas seal, and ceramic fiber may be used (for example, refer to Patent Document 1). In order to improve heat resistance, a metal brazing material mainly composed of silver, which is often used for brazing between metals, may be used.

  Further, in recent years, studies have been made to reduce the internal resistance by using a solid electrolyte layer made of yttria-stabilized zirconia or the like as thin a layer as possible to operate the SOFC in a relatively low temperature range of 800 ° C. or lower. In this case, the above-mentioned glassy gas sealing material and a metal brazing material mainly composed of silver can be used for the gas sealing. In addition, a metal separator rather than a ceramic separator can be used. In particular, if an inexpensive stainless steel separator can be used, the cost can be reduced.

JP-A-10-199554

  However, when a glassy sealing material is used as described in Patent Document 1, it may be damaged by thermal stress. Furthermore, there are cases where ceramic fibers cannot be sealed sufficiently airtight. Moreover, although the metal brazing material mainly composed of silver contains palladium, this palladium is expensive and disadvantageous in terms of cost. Furthermore, although the metal brazing material mainly composed of silver has sufficient heat resistance, it may be considered that the heat resistance is slightly insufficient at an operating temperature of 800 ° C. or higher where high output is expected.

  In addition to the heat resistance of the brazing material described above, it is necessary to study the composition of the air electrode in order to maintain good power generation efficiency. In other words, brazing using a metal brazing material having excellent heat resistance is generally performed in an atmosphere having a low oxygen partial pressure, but perovskite oxide, which is often used as an air electrode, is prone to oxygen deficiency and depends on the composition of the air electrode. May decompose in an atmosphere having a low oxygen partial pressure during brazing, and chemical stability may be insufficient. Thus, in the gas seal of the flat plate type SOFC stack, it is necessary to consider the composition of the air electrode in addition to the heat resistance of the brazing material.

  The present invention has been made in view of the above situation, and provides a solid oxide fuel cell having a stable air electrode even in an atmosphere having a low oxygen partial pressure during brazing and maintaining good power generation efficiency. For the purpose. Furthermore, by using a metal brazing material containing Ni, which has excellent heat resistance, as a brazing material that forms a joint for the purpose of isolating the flow path of the fuel gas and the flow path of the combustion-supporting gas, An object of the present invention is to provide a solid oxide fuel cell in which good power generation efficiency is maintained for a longer period of time.

The present invention is as follows.
1. The solid electrolyte layer 11, the fuel electrode 12 provided on one surface of the solid electrolyte layer 11, the air electrode 13 provided on the other surface of the solid electrolyte layer 11, and at least a part between the components are brazed. In the solid oxide fuel cell including the joint portion, the air electrode 13 has a general formula (A _x B _1-x ) (C _y D _1-y ) O _3-δ (where A is La, Y, At least one of Sm, Gd, Pr and Ca, B is at least one of Sr, Ba and Ca, C is at least one of Mn, Co, Ni and Ce, D is Fe and Mn And at least a part of the joint portion, which is made of an air electrode material represented by 0.4 ≦ x ≦ 1, 0 ≦ y ≦ 0.5, and 0 ≦ δ <1. Is made of a metal brazing material, and is a solid oxide fuel cell.
The “component” means the solid electrolyte layer 11, the fuel electrode 12 and the air electrode 13, and all other components constituting the solid electrolyte fuel cell.
2. The metal brazing material contains Ni and B or P, and when the metal brazing material is 100% by mass, the content of Ni is 60% by mass or more. A solid oxide fuel cell according to 1.
3. The metal brazing material further contains Cr. A solid oxide fuel cell according to 1.
4). The joint part joins a metal part and a ceramic part, and the metal brazing material further contains at least one of Ti and Zr, and when the metal brazing material is 100 mass%, the Ti The content of Ti in the case of containing only Zr, the content of Zr in the case of containing only Zr, or the total content in the case of containing Ti and Zr is 0.5 to 10% by mass, respectively. 2. above. Or 3. A solid oxide fuel cell according to 1.
5. The joining part joins one metal part and another metal part, and Cr is segregated in a portion adjacent to the joining part of each of the one metal part and the other metal part. 3. Or 4. A solid oxide fuel cell according to 1.
6). The joint part joins a metal part and a ceramic part, and at least one of the joint part and the vicinity of the interface between the joint part and the ceramic part has a metal contained in the metal brazing material and the 1. An oxide of at least one of the metals contained in the metal part is deposited. To 5. The solid oxide fuel cell according to any one of the above.
7). The junction 1 is formed in an atmosphere having an oxygen partial pressure of 10 to 10 ⁻¹⁵ Pa. To 6. The solid oxide fuel cell according to any one of the above.

The solid oxide fuel cell of the present invention includes a stable air electrode even in an atmosphere having a low oxygen partial pressure during brazing, and maintains good power generation efficiency.
In addition, when the metal brazing material contains Ni and B or P, and the metal brazing material is 100 mass%, when the Ni content is 60 mass% or more, a joint having excellent heat resistance is obtained. Even at an operating temperature of 800 ° C. or higher where high output is expected, good power generation efficiency can be maintained for a longer period of time.
Furthermore, when the metal brazing material further contains Cr, the heat resistance of the brazing material is further improved, and good power generation efficiency is maintained over a long period of time.
Further, when the joining portion joins the metal part and the ceramic part, the metal brazing material further contains at least one of Ti and Zr, and when the metal brazing material is 100% by mass, only Ti is contained. When the content of Ti when containing, the content of Zr when containing only Zr, or the total content when containing Ti and Zr is 0.5 to 10% by mass, the bonding strength is more And good power generation efficiency is maintained for a long time.
Furthermore, when the joining part joins one metal part and another metal part, and Cr is segregated in the part adjacent to each joining part of the one metal part and the other metal part, A joined portion having sufficient joining strength is formed, and good power generation efficiency is maintained for a long time.
Further, the joint part joins the metal part and the ceramic part, and is contained in the metal and the metal part contained in the metal brazing material in at least one of the joint part and the vicinity of the interface between the joint part and the ceramic part. Even when an oxide of at least one kind of metal among the metals to be produced is formed, a joined portion having sufficient joining strength is formed, and good power generation efficiency is maintained for a long time.
Furthermore, when the junction is formed in an atmosphere having an oxygen partial pressure of 10 to 10 ⁻¹⁵ Pa, the specific air electrode material used in the present invention is stable without being decomposed and has good power generation efficiency. Is maintained.

Hereinafter, the present invention will be described in detail with reference to FIGS.
The “solid oxide fuel cells 101 (see FIG. 10), 102 (see FIGS. 11 to 13), 103 (see FIGS. 14 to 16)” are formed by laminating a plurality of single cells. Each single cell includes a power generation layer. Each power generation layer includes a solid electrolyte layer 11, a fuel electrode 12 provided on one surface of the solid electrolyte layer 11, and an air electrode 13 provided on the other surface. Have In addition, each single cell, depending on the battery structure, includes a stacking separator 141 having a fuel gas passage 21 and a combustion-supporting gas passage 22, a fuel gas passage 21 and a combustion-supporting gas passage. The separators 16, 18, 19 for isolating the flow path 22 are stacked via intermediate separators 1441, 1442, 1443 arranged between the single cells.

  These laminating separator 141, isolation separators 16, 18, 19, intermediate separators 1441, 1442, 1443, and other parts such as lid member 15 and bottom member 17 described later are all made of metal such as stainless steel. Is formed. In addition, in order to electrically insulate between the power generation layers of each single cell, the frame body 5 made of an insulating ceramic may be laminated at a predetermined portion in the lamination direction to prevent a short circuit. In this solid electrolyte fuel cell, the solid electrolyte layer and the separator, and other parts such as the separator, intermediate separator, frame, lid member, and bottom member are joined directly or indirectly by a metal brazing material, A junction is formed.

  The “solid electrolyte layer 11” has ion conductivity that can move a part of one of the fuel gas introduced into the fuel electrode or the combustion-supporting gas introduced into the air electrode during the operation of the battery as ions. Have Although what kind of ion can be conducted is not particularly limited, examples of the ion include oxygen ion and hydrogen ion. The “fuel electrode 12” is in contact with a fuel gas serving as a hydrogen source and functions as a negative electrode in the SOFC. Further, the “air electrode 13” is in contact with a combustion-supporting gas serving as an oxygen source and functions as a positive electrode in the SOFC.

The material used for forming the solid electrolyte layer 11 can be appropriately selected depending on the use conditions of the SOFC. Examples of this material include ZrO ₂ ceramics, LaGaO ₃ ceramics, BaCeO ₃ ceramics, SrCeO ₃ ceramics, SrZrO ₃ ceramics, and CaZrO ₃ ceramics. Among these materials, preferably ZrO ₂ based ceramic, Sc, Y and at least ZrO ₂ based ceramic is preferably stabilized by one of rare earth elements, stabilized ZrO ₂ based ceramic is particularly the Sc preferable.
The thickness of the solid electrolyte layer can be set to 5 to 100 μm, particularly 5 to 50 μm, and further 5 to 30 μm in consideration of electric resistance and strength.

The material used to form the fuel electrode 12 can also be appropriately selected depending on the use conditions of the SOFC. Examples of this material include metals such as Ni and Fe, and ZrO ₂ ceramics such as zirconia stabilized by at least one of Sc, Y and rare earth elements, CeO ₂ ceramics, and ceramics such as manganese oxides. And a mixture with at least one of them. Moreover, metals, such as Pt, Au, Ag, Pd, Ir, Ru, Rh, Ni, and Fe, are mentioned. These metals may be used alone or in an alloy of two or more metals. Furthermore, a mixture (including cermet) of these metals and / or alloys and at least one of each of the above ceramics may be mentioned. Moreover, the mixture of metal oxides, such as Ni and Fe, and at least 1 type of each of the said ceramic etc. are mentioned. Among these materials, a mixture of a metal such as Ni and Fe and at least one of each of the ceramics is preferable, and a mixture of Ni and Sc stabilized with a ZrO ₂ ceramic is particularly preferable.
The planar shape of the fuel electrode is not particularly limited, but is preferably the same shape as the solid electrolyte layer and the air electrode. The fuel electrode and the solid electrolyte layer are preferably laminated on the entire surface.

The air electrode 13 has a general formula (A _x B _1-x ) (C _y D _1-y ) O _3-δ (where A is at least one of La, Y, Sm, Gd, Pr and Ca, B is at least one of Sr, Ba and Ca, C is at least one of Mn, Co, Ni and Ce, D is at least one of Fe and Mn, and 0.4 ≦ x ≦ 1 , 0 ≦ y ≦ 0.5)). In addition, δ represents an oxygen excess amount or an oxygen deficiency amount, and is usually 0 ≦ δ <1, particularly 0 ≦ δ ≦ 0.1.

As A, La is often used, and as B, Sr or Ca, particularly Sr is often used. Furthermore, x is usually 0.5 ≦ x ≦ 0.8. Further, Co or Ni is often used as C, and Fe and Mn are used similarly as D. Furthermore, y is usually 0.2 ≦ y ≦ 0.4. As such (A _x B _1-x ) (C _y D _1-y ) O _3-δ- based composite oxide, for example, La _0.6 Sr _0.4 Co _0.2 Fe _0.8 O ₃ La _0.6 Sr _0.4 Co _0.2 Mn _0.8 O ₃ , La _0.6 Sr _0.4 Ni _0.2 Fe _0.8 O ₃ , La _0.5 Sr _0.5 FeO ₃ , _{La 0.7 Sr 0.3 MnO 3, La} 0.8 Sr 0.2 MnO 3 and the like.

  The planar shape of the air electrode is not particularly limited, but is preferably the same shape as the solid electrolyte layer and the fuel electrode. Further, the dimension in the planar direction can be the same as that of the solid electrolyte layer and the fuel electrode depending on the structure of the solid oxide fuel cell. Furthermore, when the isolation separator is joined to the peripheral edge of one surface of the solid electrolyte layer, the air electrode is formed smaller than the solid electrolyte layer and the fuel electrode. The air electrode and the solid electrolyte layer are preferably laminated on the entire surface.

  In the solid oxide fuel cell, it is not preferable that the power generation layer of each single cell is excessively thin from the viewpoint of strength. Moreover, it is not preferable to make the solid electrolyte layer thicker from the viewpoint of power generation performance. Therefore, it can be a fuel electrode support type, and in this fuel electrode support type, the fuel electrode is preferably 20 times or more thicker than the solid electrolyte layer. If it is less than 20 times, the mechanical strength of the power generation layer tends to be insufficient. The thickness of the fuel electrode is preferably 200 to 3000 μm, particularly 500 to 2000 μm. If it is less than 200 μm, it will not function effectively as a substrate, and if it exceeds 3000 μm, the power generation efficiency per volume tends to decrease. On the other hand, an air electrode support type can also be used as described below. In this case, the thickness of the fuel electrode is preferably 10 to 50 μm, particularly preferably 20 to 40 μm. If this thickness is 10 to 50 μm, it functions sufficiently as an electrode and does not need to be thicker than 50 μm.

  In the solid oxide fuel cell, the air electrode can also be formed as a substrate that supports the strength of the power generation layer. In the case of the air electrode support type, the thickness of the air electrode is preferably 20 times or more that of the solid electrolyte layer. If it is less than 20 times, the mechanical strength of the power generation layer tends to be insufficient. The thickness of the air electrode is preferably 200 to 3000 μm, particularly 500 to 2000 μm. If it is less than 200 μm, it will not function effectively as a substrate, and if it exceeds 3000 μm, the power generation efficiency per volume tends to decrease. On the other hand, in the case of the fuel electrode support type, the thickness of the air electrode is preferably 10 to 100 μm, particularly preferably 20 to 50 μm. When the thickness is less than 10 μm, the electrode may not function sufficiently, and when the thickness exceeds 100 μm, the solid electrolyte layer may be peeled off.

  The solid oxide fuel cell includes various types of “components”, and includes the “joint portion” (joint portion 81 that joins metal components, and a join portion 82 that joins metal components and ceramic components. ), As described above, in the solid oxide fuel cell, between the solid electrolyte layer 11 and the separators 16, 18, 19, and between the separators 16, 18, 19, intermediate separators 1441, 1442, 1443, frame 5, a part that directly or indirectly joins each of the other components such as the lid member 15 and the bottom member 17. Further, it is preferable that at least a part of the joints are formed of the “metal brazing material” and all the joints are formed of the metal brazing material. The metal brazing material has high heat resistance and can be a solid oxide fuel cell in which good power generation efficiency is maintained.

  The metal brazing material is not particularly limited, and a Ni-based metal brazing material (hereinafter referred to as “Ni-based brazing material”), an Ag-based metal brazing material (hereinafter referred to as “Ag-based brazing material”), and the like can be used. . As this metal brazing material, a Ni-based brazing material having better heat resistance is preferable. As this Ni-based brazing material, one containing Ni and B or P, and when the Ni-based brazing material is 100 mass%, a Ni content of 60 mass% or more can be used. The Ni content can be 70% by mass or more, and can be 80% by mass or more (when B is contained, it is usually 95% by mass or less, and when P is contained, it is usually 85 mass% or less). If the Ni content is 60% by mass or more, a sufficiently heat-resistant Ni-based brazing material can be obtained, and when the operating temperature is about 800 ° C, there is a portion where the temperature rises to near 900 ° C. However, it is possible to obtain a solid oxide fuel cell that can withstand even when operated at a higher temperature of 800 to 1000 ° C.

  The Ni-based brazing material contains B or P in addition to Ni. By containing B or P, the fluidity is improved, the metal parts and between the metal parts and the ceramic parts can be sufficiently adhered, and the bonding strength can be further increased. The content of B or P is not particularly limited, but when the metal brazing material is 100% by mass, in the case of B, 1 to 5% by mass, particularly 1.5 to 4% by mass, and further 2 to 3.5% by mass. %. If the content of B is 1 to 5% by mass, the flowability of the Ni-based brazing material can be sufficiently increased. Moreover, in the case of P, it can be 5-15 mass%, Especially 6.5-13.5 mass%, Furthermore, it can be 8-12 mass%. If the content of P is 5 to 15% by mass, the flowability of the Ni-based brazing material can be sufficiently increased.

  In addition to Ni and B or P, the Ni brazing material may further contain Cr. By containing an appropriate amount of Cr, the heat resistance of the Ni-based brazing material can be further increased. The content of Cr is not particularly limited, but can be 5 to 20% by mass, particularly 10 to 18% by mass, and further 12 to 16% by mass when the Ni brazing material is 100% by mass. If the content of Cr is 8 to 20% by mass, the heat resistance of the Ni-based brazing material can be sufficiently increased.

  Further, when the metal part and the ceramic part are joined using the Ni-based brazing material, the Ni-based brazing material may further contain at least one of Ti and Zr. When this Ni-based brazing material is 100% by mass, the content of Ti when only Ti is contained, the content of Zr when only Zr is contained, or when Ti and Zr are contained Each of the total contents can be 0.5 to 10% by mass, preferably 1 to 8% by mass. If these content is 0.5-10 mass%, joining strength can fully be improved.

  An Ag-based brazing material can also be used as the metal brazing material. This Ag-based brazing material usually contains Pd. When the total amount of Ag and Pd is 100% by mass, Pd is contained in an amount of 2 to 10% by mass, particularly 3 to 7% by mass. If the content of Pd is 2 to 10% by mass, an Ag-based brazing material excellent in oxidation resistance and the like can be obtained, and a joint portion having sufficient durability can be formed. Furthermore, the Ag-based brazing material flows sufficiently at the time of joining, and the sealing performance of the joined portion can be improved.

  The Ag-based brazing material may further contain Cu. The content of each of Ag, Pd and Cu when Cu is contained is not particularly limited, but when the total of Ag, Pd and Cu is 100% by mass, the content of Ag is 45 to 65% by mass. In particular, it is preferable that the content of Pd is 50 to 60% by mass, the content of Pd is 15 to 35% by mass, particularly 20 to 30% by mass, and the content of Cu is 10 to 30% by mass, and particularly 15 to 25% by mass. When Cu is contained, even if it contains a larger amount of Pd than an Ag-based brazing material that does not contain Cu, it has sufficient fluidity and maintains excellent sealing properties. The total of Ag and Cu is preferably 65% by mass or more, that is, if the Pd content is 35% by mass or less, the Ag-based brazing material flows sufficiently and improves the sealing performance of the joint. Can be made.

  The Ag-based brazing material may further contain Ti. By containing an appropriate amount of Ti, particularly high bonding strength can be obtained even when the bonding temperature is relatively low. The content of Ti is when the total of Ag, Pd and Ti is 100% by mass, or when Cu is contained, the total of Ag, Pd, Cu and Ti is 100% by mass. 0.05 to 10% by mass, particularly 0.05 to 8% by mass, and more preferably 0.05 to 6% by mass. When the Ti content is 0.05 to 10% by mass, a bonding portion having practically sufficient strength can be formed even if the bonding atmosphere is an atmosphere having a low oxygen partial pressure.

The thermal expansion coefficient of the Ni-based brazing material is (11-14) × 10 ⁻⁶ / ° C., although it depends on the composition. On the other hand, the thermal expansion coefficient of the Ag-based brazing material is usually (16 to 20) × 10 ⁻⁶ / ° C. Furthermore, the thermal expansion coefficient of stainless steel often used as a metal part is (12 to 17) × 10 ⁻⁶ / ° C., and the thermal expansion coefficient of ceramics such as ZrO ₂ and CeO ₂ used as ceramic parts is (10 to 11.5) × 10 ⁻⁶ / ° C. Thus, the difference between the thermal expansion coefficient of the Ni-based brazing material and the thermal expansion coefficient of each of the stainless steel and the ceramic is that the thermal expansion coefficient of the Ag-based brazing material and each of the thermal expansion coefficients of the stainless steel and the ceramic are Less than the difference. Therefore, when the Ni-based brazing material is used, the thermal stress is more easily relaxed, and a better bonded state is maintained.

  The Ni-based brazing material and the Ag-based brazing material may contain other metals in addition to the above-described various metals as long as the bonding strength, gas sealability, and the like are not deteriorated. Examples of such metals include Sn, In, and Nb. These other metals are 10 parts by mass or less, particularly 0.1 to 10 parts by mass, and further 0.5 to 5 parts by mass, when each of the Ni-based brazing material and the Ag-based brazing material is 100 parts by mass. It can be included.

The atmosphere during the bonding is not particularly limited as long as the atmosphere has a low oxygen partial pressure, and may be a vacuum atmosphere, a nitrogen atmosphere, an argon atmosphere, or the like. When the metal brazing material is used, the bonding atmosphere is preferably an atmosphere having a low oxygen partial pressure. With such a bonding atmosphere, the bonding strength can be greatly improved. On the other hand, it is preferable that the oxygen partial pressure of the bonding atmosphere is low enough not to decompose the air electrode. The oxygen partial pressure in the atmosphere during bonding is not particularly limited, but is preferably 10 to 10 ⁻¹⁵ Pa, particularly preferably 10 to 10 ⁻¹⁰ Pa. The solid electrolyte fuel cell of the present invention includes a stable air electrode that does not decompose during bonding in an atmosphere having a low oxygen partial pressure, and the oxygen partial pressure of the bonding atmosphere is 10 to 10 ⁻¹⁵ Pa. The effects and effects of the present invention are particularly remarkable.

  In the solid oxide fuel cell of the present invention, the metal parts include a separator 21 for laminating provided with a flow path 21 for introducing fuel gas into the fuel electrode 12 and a flow path 22 for introducing combustion-supporting gas into the air electrode 13. 141, an upper separator 142 having a flow path 22 for introducing a combustion-supporting gas into the air electrode 13, a lower separator 143 (see FIG. 10) having a flow path 21 for introducing a fuel gas into the fuel electrode 12. Are bonded to the respective solid electrolyte layers 11 of the adjacent power generation layers, and are provided with a flow path 21 for introducing fuel gas into the fuel electrode 12 of one power generation layer and the air electrode 13 of the other power generation layer. Isolation separators 16, 18, 19 (see FIGS. 12, 13, 15, 16) for forming a flow path 22 for introducing gas, and an intermediate separator 144 interposed between a plurality of stacked single cells 1442 and 1443 (see FIGS. 12 to 16), a lid member 15 (see FIGS. 11 to 16) forming the uppermost surface of the solid oxide fuel cell (another single cell is laminated on the upper surface of the uppermost single cell) In this case, it functions as an intermediate separator.), And a bottom member 17 (see FIGS. 11 to 16) that forms the bottom surface of the solid oxide fuel cell (with another single cell laminated on the lower surface of this single cell) In the case, it functions as an intermediate separator).

The metal which comprises a metal component is not specifically limited, Stainless steel, a nickel base alloy, a chromium base alloy etc. are mentioned. Examples of the stainless steel include ferritic stainless steel, martensitic stainless steel, and austenitic stainless steel. Examples of ferritic stainless steel include SUS430, SUS434, and SUS405. Examples of martensitic stainless steel include SUS403, SUS410, and SUS431. Examples of austenitic stainless steel include SUS201, SUS301, and SUS305. Further, examples of the nickel-based alloy include Inconel 600, Inconel 718, Incoloy 802, and the like. The chromium-based alloys, Ducrlloy CRF (94 wt% Cr-5 wt% Fe-1 _wt% Y 2 _{O 3),} and the like. These various metals can be selected according to the structure of the solid oxide fuel cell.

Moreover, as a ceramic component, the frame 5 (refer FIG. 12, 13, 15, 16) etc. which are arrange | positioned between the ceramic which forms the solid electrolyte layer 11, and at least one part of intermediate separator and isolation | separation separator, etc. are mentioned. It is done. The ceramic constituting the ceramic part is not particularly limited, and examples thereof include various ceramics used for forming the solid electrolyte layer. Further, MgO, MgAl ₂ O ₄ , ZrO _2, Al ₂ O ₃ , a mixture thereof, and the like that are often used as a frame body can be given. These ceramics can be selected depending on the structure of the solid oxide fuel cell.

  When a metal part and a metal part are joined using a Ni-based brazing material containing Cr, Cr segregates in a portion adjacent to the joint part of each metal part, and Cr segregation layers 9411 and 9412 (Example column) [2] Bonding layer (This bonding layer is formed between a metal and a metal or between a metal and a ceramic in the same manner as a bond between metal parts or between a metal part and a ceramic part in a solid oxide fuel cell. 3) in the evaluation of the composition, etc.) is formed. This confirms that the Ni-based brazing material and the respective metal parts are sufficiently in close contact with each other and a good joint having a high joint strength is formed. In addition, the part "adjacent" to the joint part of each metal part means the part to 100 micrometers in the thickness direction from the interface with the joint part of each metal part.

  Further, when the metal part and the ceramic part are joined using the Ni-based brazing material, the metal and the metal part contained in the metal brazing material at least one of the joint portion and the vicinity of the interface between the joint portion and the ceramic part. The metal oxide precipitate 942 is formed by depositing at least one metal oxide of the metals contained in the metal (FIG. 4 in [2] Evaluation of composition of bonding layer, etc. in the column of Examples). 6 and FIG. 6, the metal oxide precipitation portion 942 is precipitated in the bonding layer 93 and in the vicinity of the interface between the bonding layer 93 and the ceramic sintered body 92. The portion 942 may be deposited mainly only in the bonding layer 93 or may be deposited mainly only in the vicinity of the interface. The metal oxide precipitation portion 942 may be formed in a layer shape, or may be partially formed inside the joint and in the vicinity of the interface. This confirms that the Ni-based brazing material and the ceramic part are sufficiently in close contact with each other and a good joint having a high joint strength is formed. The “near the interface” between the joint and the ceramic part means a part from the interface between the joint and the ceramic part to 50 μm in the thickness direction of each of the joint and the ceramic part.

Hereinafter, the present invention will be described specifically by way of examples.
[1] Evaluation of air electrode material Experimental Examples 1-12 and Comparative Experimental Examples 1-2
In a solid electrolyte fuel cell, in order to prevent a reaction at the interface when forming an air electrode on one surface of a solid electrolyte layer, it is usually from samarium-doped ceria (SDC) such as Sm _0.2 Ce _0.8 O _2. An anti-reaction layer is provided. Simulating this, a disk-shaped SDC sintered body having a diameter of 20 mm and a thickness of 500 μm was produced, and then the surface was polished and smoothed. The air electrode material described in Table 1 at the center of the smooth surface A ceramic slurry containing 100 parts by mass, 5 parts by mass of ethyl cellulose as a binder and 30 parts by mass of butyl carbitol as a solvent was prepared, and this slurry was screen-printed to form a coating film. Subsequently, it was baked by heating for 60 minutes at the temperature shown in Table 1 in an air atmosphere to form a film having a diameter of 15 mm and a thickness of 30 μm (corresponding to an air electrode in a solid electrolyte fuel cell). Thereafter, heat treatment was performed at 1100 ° C. for 30 minutes in a vacuum atmosphere (pressure 1 Pa or less) similar to the heat treatment during brazing. Subsequently, each crystal phase of the air electrode material and the coating was confirmed by X-ray diffraction.

  According to the results in Table 1, in Experimental Examples 1 to 12 using the air electrode material represented by the above general formula, the crystal phase of the film after baking is a single phase of perovskite oxide and heated in a vacuum atmosphere. It turns out that it is stable. On the other hand, in Comparative Experimental Examples 1 and 2, it was confirmed that a part was decomposed.

[2] Evaluation of composition of bonding layer and the like (1) Joined material and metal brazing material As a joined material, a molded body 91 of SUS430 often used as a metal part in a solid electrolyte fuel cell, and a ceramic part A zirconia (YSZ) sintered body 92 stabilized with 8% by mass of yttria, which is often used, was used. A SUS430 molded body 91 having a size of 15 × 15 × 20 mm was used, and a surface of 15 × 15 mm was used as a bonding surface to prepare the bonded body 9. In addition, the YSZ sintered body 92 is formed by forming and firing raw material powders by a conventional method to form a 15 × 15 × 20 mm sufficiently densified rectangular parallelepiped sintered body, with a 15 × 15 mm surface as a bonding surface. Used to make the body 9. The metal brazing material is a paste obtained by passing powder through 250 mesh, (a) containing 89% by mass of Ni and 11% by mass of P, and (b) 82% by mass of Ni, 15% by mass. % Of Cr and 3% by weight of B, (c) 95% by weight of Ag and 5% by weight of Pd, and (d) 54% by weight of Ag, 25% by weight of Pd and It printed using what contains 21 mass% Cu, Then, it heat-processed and the joining layer 93 was formed.

(2) Brazing The SUS430 molded body 91 is vertically placed so that the 15 × 15 mm surface is the upper surface, and each of the paste-like metal brazing materials (a) to (d) is screen-printed on this surface to obtain a thickness. A 50 μm-thick coating film was formed, and the SUS430 molded body 91 or the YSZ sintered body 92 was placed on the coating film so that the 15 × 15 mm surfaces thereof were in contact with each other. Then, 500 g of tungsten as a main component (content: 95% by mass) is formed on the upper surface of the upper SUS430 molded body 91 or the YSZ sintered body 92 so that the respective members do not deviate from each other at the respective contact surfaces. A weight is placed, and this is housed in an atmosphere-controlled heat treatment furnace. Under a vacuum atmosphere (pressure 1 Pa or less), the optimum temperature for each brazing material is (a) 1000 ° C, (b) 1100 ° C, (c) 1050 ° C, (D) The bonded body 9 was manufactured by holding at 950 ° C. for 30 minutes and bonding. The temperature raising / lowering speed was 500 ° C./hour.

(3) Composition of bonding layer, etc. In the case of the metal brazing material (a) and (d) using the bonded body 9 prepared in the above (2), the cross section of the bonding layer 93 between the SUS430 molded bodies 91 is respectively shown. Observed with an X-ray microanalyzer. In the case of the metal brazing materials (b) and (c), the cross section of the bonding layer 93 between the SUS430 molded bodies 91 and between the SUS430 molded body 91 and the YSZ sintered body 92 is observed with an X-ray microanalyzer. did. Further, in the joined body using the metal brazing material (a), the joined body was heated at 800 ° C. for 100 hours, and then the cross section of the joining layer 93 and the like between the SUS430 molded bodies 91 was observed with an X-ray microanalyzer.

Hereinafter, the composition of each bonding layer and the like will be described with reference to FIGS.
According to FIG. 1, which is a schematic diagram of a cross section of the bonding layer 93 and the like between the SUS430 molded bodies 91 when the metal brazing material (a) is used, P is segregated at the center of the bonding layer 93 in the thickness direction. The formed P segregation layer 943 was confirmed. When this joined body 9 is heated at 800 ° C. for 100 hours, as shown in FIG. 2, (1) Ni contained in the metal brazing material diffuses on the interface side with the joining layer 93 of each SUS430 molded body 91. Fe diffusion layers 9441 and 9442 formed in this manner, and (2) Fe / Cr formed by diffusing Fe and Cr contained in SUS430 on the interface side with each SUS430 molded body 91. (3) P segregated material in which P contained in the metal brazing material is segregated in the bonding layer 93, the Ni diffusion layers 9441, 9442, and the Fe / Cr diffusion layers 9451, 9452. It was confirmed that 946 was scattered.

  Moreover, according to FIG. 3 which is a schematic diagram of a cross section of the bonding layer 93 and the like between the SUS430 molded bodies 91 when the metal brazing material (b) is used, (1) each SUS430 molded body 91 of the bonding layer 93 and Fe diffusion layers 9471 and 9472 formed by diffusing Fe contained in SUS430 on the interface side, and (2) the metal brazing material on the interface side with the bonding layer 93 of each SUS430 molded body 91 Cr segregation layers 9411 and 9412 formed by segregating Cr were confirmed. Further, according to FIG. 4 which is a schematic diagram of a cross section of the bonding layer 93 and the like between the SUS430 molded body 91 and the YSZ sintered body 92 when the metal brazing material (b) is used, (1) the bonding layer 93 Similarly, an Fe diffusion layer 9471 is formed on the interface side with the SUS430 molded body 91, and (2) SUS430 and a metal brazing material are formed in the inside of the joining layer 93 and in the vicinity of the interface between the YSZ sintered body 92 and the joining layer 93. And (3) Cr contained in the metal brazing material is present on the interface side with the bonding layer 93 of the SUS430 molded body 91. A Cr segregation layer 9411 formed by segregation was confirmed.

  Furthermore, according to FIG. 5 which is a schematic diagram of a cross section of the bonding layer 93 between the SUS430 molded bodies 91 when the metal brazing material (c) is used, the interface side of each SUS430 molded body 91 with the bonding layer 93 Further, Pd diffusion layers 9481 and 9482 formed by diffusing Pd contained in the metal brazing material were confirmed. Further, according to FIG. 6 which is a schematic diagram of a cross section of the bonding layer 93 and the like between the SUS430 molded body 91 and the YSZ sintered body 92 when the metal brazing material (c) is used, (1) the SUS430 molded body. Similarly, a Pd diffusion layer 9481 is formed on the interface side of the bonding layer 93 with 91, and (2) Cr oxide contained in SUS430 is formed in the vicinity of the interface between the YSZ sintered body 92 and the bonding layer 93. A metal oxide deposit 942 formed by precipitation was confirmed. Furthermore, according to FIG. 7 which is a schematic diagram of a cross section of the bonding layer 93 and the like between the SUS430 molded bodies 91 when the metal brazing material (d) is used, the interface side of each of the bonding layers 93 with the SUS430 molded bodies 91 In addition, Fe—Cu—Pd reaction layers 9491 and 9492 generated by the reaction of Fe, Cu, and Pd were confirmed.

[3] Evaluation of bonding strength between SUS430 and YSZ sintered body or MgO—MgAl ₂ O ₄ sintered body Experimental Examples 13 to 30 and Comparative Experimental Examples 3 to 4
The metal brazing material shown in Table 2 is a metal often used as a separator and the like, a YSZ sintered body often used as a solid electrolyte layer of SOFC, or MgO and MgAl often used as a frame. mixture of ₂ O ₄ (the sum of MgO and MgAl ₂ O ₄ is 100 mass%. containing 90% by weight of MgAl ₂ O ₄ of MgO and 10 wt%) was bonded to the, The joint strength was evaluated. As the metal, SUS430, which is a ferritic stainless steel, was used.

(1) To-be-joined material and metal brazing material A sheet having a thickness of 0.3 mm was used as SUS430, and it was cut into a size of 15 × 15 mm and used for preparing a test piece. In addition, the YSZ sintered body was formed by raw material powder by a conventional method and fired to obtain a 15 × 15 × 20 mm sufficiently densified rectangular parallelepiped sintered body, which was used for preparing a test piece. Furthermore, as the raw material powder of the MgO-MgAl ₂ O ₄ sintered body, a mixed powder of 90% by mass MgO powder and 10% by mass MgAl ₂ O ₄ powder is used, molded by a conventional method, and fired. 15 × 15 × 20 mm, a sufficiently dense rectangular parallelepiped sintered body, which was used for preparing a test piece. As the metal brazing material, a paste made of 250-mesh powder was used for preparing a test piece.

(2) Brazing (Preparation of joined body)
Each of the paste-like metal brazing materials shown in Table 2 was screen-printed on both surfaces of the SUS430 sheet to form a coating film having a thickness of 50 μm. On the other hand, the YSZ sintered body or the MgO—MgAl ₂ O ₄ sintered body is placed vertically so that the 15 × 15 mm surface is the upper surface, and one surface of the SUS430 sheet having a coating film formed on both surfaces is placed on this surface. Then, another YSZ sintered body or MgO—MgAl ₂ O ₄ sintered body was placed on the other surface of the SUS430 sheet such that the 15 × 15 mm surface thereof was in contact therewith. Then, 500 g of tungsten as a main component (content: 95 mass) is formed on the upper surface of the upper YSZ sintered body or MgO—MgAl ₂ O ₄ sintered body so that the respective members do not deviate from each other at the respective contact surfaces. %) Was placed in an atmosphere-controlled heat treatment furnace, and joined in a vacuum atmosphere (pressure 1 Pa or less) at the temperature shown in Table 2 for 30 minutes to produce a joined body. The temperature raising / lowering speed was 500 ° C./hour. In Comparative Experimental Examples 3 and 4, a crystallized glass paste is applied to both surfaces of SUS430 to be bonded to the YSZ sintered body or MgO-MgAl ₂ O ₄ sintered body, and the heat treatment furnace is used in an atmospheric atmosphere. A joined body was fabricated in the same manner as in the experimental example except that it was housed, held at 1000 ° C. for 1 hour and heat-treated. In Comparative Examples 3 and 4, the temperature raising / lowering rate was 200 ° C./hour.

(3) Measurement of joint strength The joined body produced in (2) above was cut in a direction perpendicular to the respective joining surfaces of each joined body, and four pieces having dimensions of 7.5 × 7.5 × 40 mm were obtained. The rod-shaped body. Then, the side surface of the rod-shaped body was polished according to JIS R 1624 to obtain a 6 × 6 × 40 mm test piece, and the bonding strength was measured by a four-point bending method. The results are also shown in Table 2 as average values of four test pieces.

According to the results of Table 2, it can be seen that in Experimental Examples 13 to 30, the bonding strength is 71 to 221 MPa, which is sufficiently higher than the bonding strength 28 to 31 MPa of Comparative Experimental Examples 3 to 4. Further, in Experimental Examples 15 to 18 in which the metal brazing material contains 0.5 to 10.0% by mass of Ti, the bonding strength is larger as 136 to 201 MPa, and the metal brazing material is 2.0 to 5.0% by mass. In Experimental Examples 16 to 17 containing Ti, the bonding strength is particularly large as 197 to 201 MPa. Furthermore, also in Experimental Examples 20 to 21 in which the metal brazing material contains 2.0 to 5.0% by mass of Zr, the bonding strength is greatly improved to 162 to 186 MPa as in the case of containing Ti. In addition, according to Experimental Examples 22 to 24, in the case of the YSZ sintered body, the joining strength is further improved by adding Ti to the metal brazing material as in the case of the MgO—MgAl ₂ O ₄ sintered body. Furthermore, also in Experimental Examples 25 to 30 using an Ag-based brazing material, the bonding strength is further improved by containing 2.0 to 5.0% by mass of Ti.

[4] Evaluation of heat resistance Experimental examples 31 to 35
Metal brazing materials listed in Table 3 were used to join metals often used as SOFC separators and the like, and the joining strength was evaluated. As the metal, a molded body and a sheet of SUS430, which is a ferritic stainless steel, were used. Further, the heat resistance of the metal brazing material (represented as “deterioration distance” in Table 3) was evaluated based on the distance from the surface of the crack generated in the bonding layer when the bonded body was heated at 800 ° C. for 1000 hours in an air atmosphere. .

(1) Material to be joined, metal brazing material and brazing A SUS430 molded body having a size of 15 × 15 × 20 mm and a SUS430 sheet having a thickness of 0.3 mm were used for preparing test pieces. Further, as the metal brazing material, a paste obtained by passing a powder through 250 mesh was used. Moreover, it brazed by the following method.
The SUS430 molded body was placed vertically so that the 15 × 15 mm surface was the upper surface, and each of the paste-like metal brazing materials was screen-printed to form a coating film having a thickness of 50 μm. Thereafter, a SUS430 sheet of 15 × 15 × 0.3 mm was placed on the coating film, and each paste-like metal brazing material was screen printed on the sheet to form a coating film having a thickness of 50 μm. . Subsequently, the SUS430 molded body was placed on this coating film so that the 15 × 15 mm surface thereof was in contact therewith. In order to prevent the respective members from being displaced from each other at the respective contact surfaces, a weight having 500 g of tungsten as a main component (content: 95 mass%) is placed on the upper surface of the upper SUS430 molded body. It accommodated in the controlled heat processing furnace, it hold | maintained for 30 minutes at the temperature of Table 3 in a vacuum atmosphere (pressure 1 Pa or less), and the joined body 9 (refer FIG. 8) was produced. The temperature raising / lowering speed was 500 ° C./hour.

(2) Measurement of bonding strength The bonded body 9 produced in the above (1) was cut in a direction perpendicular to the respective bonded surfaces of each bonded body, and 4 having dimensions of 7.5 × 7.5 × 40 mm. A rod-shaped body of books was used. Then, the side surface of the rod-shaped body was polished according to JIS R 1624 to obtain a 6 × 6 × 40 mm test piece, and the bonding strength was measured by a four-point bending method. The results are also shown in Table 3 as an average value of four test pieces.

(3) Evaluation of degradation distance The joined body 9 (see FIG. 8) produced in the same manner as in the above (1) was cut in the direction perpendicular to the respective joining surfaces of each joined body 9 to obtain 7.5 × Four rods having dimensions of 7.5 × 40 mm were obtained. Then, the side surface of the rod-shaped body was polished according to JIS R 1624 to obtain a 6 × 6 × 40 mm rod-shaped body. Next, this rod-shaped body was placed in a heat treatment furnace and heated at 800 ° C. for 1000 hours in an air atmosphere. Thereafter, each rod-shaped body was immersed in a liquid epoxy resin contained in a container, and then the epoxy resin was cured to coat the entire peripheral surface of each rod-shaped body with the epoxy resin. Thereafter, each rod-like body is cut in the length direction, the cross section is mirror-polished, and this polished surface is observed with an optical microscope equipped with a scaled eyepiece, and the length of the crack from the end of the bonding layer 93 ( (Deterioration distance) was measured (see FIG. 9). The results are also shown in Table 3.

  According to the results in Table 3, the bonding strength was sufficient in each of the Ni-based brazing materials of Experimental Examples 31 to 33 and the Ag-based brazing materials of Experimental Examples 34 to 35. On the other hand, the deterioration distance was 15 to 30 μm for the Ni-based brazing materials of Experimental Examples 31 to 33, and 105 to 330 μm for the Ag-based brazing materials of Experimental Examples 34 to 35, and there was a large difference. Thus, the Ni-based brazing material has particularly high heat resistance, and good power generation efficiency is maintained even at an operating temperature of 800 ° C. or higher where high output is expected.

[5] Solid electrolyte fuel cell Example 1 (a fuel cell including a separator having flow paths for fuel gas and combustion-supporting gas and having two power generation layers laminated)
(1) Fuel Cell Structure FIG. 10 schematically shows a cross section of a flat plate SOFC stack 101 in which two power generation layers are stacked.
The flat plate type SOFC stack 101 has a structure in which two power generation layers are stacked via a stacking separator 141. Each power generation layer is made of zirconia stabilized with Sc (ScSZ) and has a solid electrolyte layer 11 with a thickness of 200 μm, and a fuel electrode made of Ni and ScSZ with a thickness of 30 μm. 12 and an air electrode 13 made of La _0.8 Sr _0.2 MnO ₃ and having a thickness of 30 μm. The solid electrolyte layer 11, the fuel electrode 12, and the air electrode 13 are all square in shape, the solid electrolyte layer 11 has a larger area than the fuel electrode 12 and the air electrode 13, and the fuel electrode 12 and the air electrode 13 are the same size. And it is provided in the position which opposes.

  The two power generation layers are stacked via a stacking separator 141 made of SUS430. A fuel gas channel 21 is formed on the upper surface of the laminating separator 141, and a combustion-supporting gas channel 22 is formed on the lower surface. Further, an upper separator 142 made of SUS430 is disposed above the upper power generation layer, and a flow-supporting gas passage 22 is formed on the lower surface thereof. Further, a lower separator 143 made of SUS430 is disposed below the lower power generation layer, and a fuel gas passage 21 is formed on the upper surface thereof.

  Further, the periphery of the solid electrolyte layer 11 of the upper power generation layer, the periphery of each of the upper separator 142 and the stacking separator 141, the periphery of the solid electrolyte layer 11 of the lower power generation layer, the lower separator 143 and the stacking separator 141 The peripheral edges are joined to form a joint 82. As the metal brazing material, the Ni-based brazing material of Experimental Example 16 among the specific metal brazing materials described in [2] above was used, and was joined at 1100 ° C. in a vacuum atmosphere as in Experimental Example 16.

(2) Operation of fuel cell In this solid electrolyte fuel cell, each solid electrolyte layer of the two power generation layers is formed of ScSZ having an ionic conductivity approximately twice that of YSZ, and is about 750 ° C. The current can be taken out stably even at the operating temperature of. Therefore, it is possible to use a separator made of stainless steel such as SUS430 instead of ceramic, and the solid electrolyte layer and the separator can be firmly bonded by the Ni brazing material. And it is thought that the compressive stress remains in each joint part, and the tough stack structure which can endure various external forces can be formed.

Example 2 (External manifold type fuel cell having two stacked single cells and using a fuel electrode as a substrate)
(1) Structure of fuel cell (a) Power generation layer and various separators The appearance of a flat-plate SOFC stack 102 having another structure different from the fuel cell of Example 1 in which two power generation layers are stacked is shown in FIG. Illustrated by diagram. 12 is a schematic diagram of the AA cross section in FIG. 11, and FIG. 13 is a schematic diagram of the BB cross section in FIG.
In the flat plate type SOFC stack 102, two single cells are stacked via an intermediate separator 1441. The power generation layer included in each single cell is made of the same material as the fuel cell of Example 1, has a square planar shape, and has a fuel electrode 12 with a thickness of 1000 μm as a substrate. The surface of the fuel electrode 12 is made of the same material as that of the fuel cell of Example 1, and the solid electrolyte layer 11 having the same shape and size in the planar direction as the fuel electrode 12 and a thickness of 30 μm is formed. . Further, the surface of the solid electrolyte layer 11 is made of the same material as that of the fuel cell of Example 1, has the same planar shape as the solid electrolyte layer 11, has a smaller dimension than the solid electrolyte layer 11, and has a thickness of A 30 μm air electrode 13 is formed.

The upper unit cell includes a nickel felt layer 3 disposed on the upper surface of the intermediate separator 1441, a fuel electrode 12 serving as a substrate, a solid electrolyte layer 11, an air electrode 13, an Inconel fiber mesh layer 4, and a lid member 15 in this order. . Further, the cover member 15 surrounds the peripheral surface of the Inconel fiber mesh layer 4, the lower surface is bonded to the solid electrolyte layer 11, and the upper surface is made of an MgO—MgAl ₂ O ₄ sintered body made of an insulating ceramic. And the upper single cell isolation separator 16. On the other hand, the lower unit cell includes a nickel felt layer 3 disposed on the upper surface of the bottom member 17, a fuel electrode 12 serving as a substrate, a solid electrolyte layer 11, an air electrode 13, and an Inconel fiber mesh layer 4 in this order. Further, it has a lower single cell isolation separator 18 that surrounds the peripheral surface of the Inconel fiber mesh layer 4, whose lower surface is bonded to the solid electrolyte layer 11, and whose upper surface is bonded to the intermediate separator 1441 through the frame 5.

  The lid member 15, the upper unit cell isolation separator 16, the intermediate separator 1441, the lower unit cell isolation separator 18, and the bottom member 17 are all formed of SUS430. Further, the upper single cell isolation separator 16 and the intermediate separator 1441, and the lower single cell isolation separator 18 and the bottom member 17 are each Ni-based in the experimental example 31 of the specific metal brazing material described in [4] above. A brazing material is used and bonded at 1100 ° C. in a vacuum atmosphere in the same manner as in Experimental Example 31 to form a bonded portion 81. Further, the lid member 15 and the upper single cell isolation separator 16, and the intermediate separator 1441 and the lower single cell isolation separator 18 are respectively joined via the frame 5, and in this case, in each of the above [2] Of the specific metal brazing materials described, the Ni-based brazing material of Experimental Example 16 is used and bonded at 1100 ° C. in a vacuum atmosphere in the same manner as in Experimental Example 16 to form a bonding portion 82.

(B) Fuel gas introduction pipe or discharge pipe and combustion-supporting gas introduction pipe or discharge pipe In the upper single cell, the space formed between the upper single cell isolation separator 16 and the intermediate separator 1441 A fuel gas introduction pipe 71 for introducing fuel gas into the fuel electrode 12 of the cell is opened (see FIG. 12). Further, a fuel gas discharge pipe 72 for discharging fuel gas from the fuel electrode 12 of the upper unit cell is opened at a position diagonal to the opening of the fuel gas introduction pipe 71 in this space (FIG. 13). reference). Further, a through hole 161 for introducing a combustion-supporting gas into the air electrode 13 of the upper unit cell is provided on one side surface of the upper unit cell isolation separator 16 (see FIG. 12). In the diagonal direction on the side surface side, there are provided through holes 162 for discharging the combustion-supporting gas from the air electrode 13 of the upper unit cell (see FIG. 13). These through holes 161 and 162 are communicated with spaces formed between the lid member 15 and the upper unit cell isolation separator 16, respectively, and each space is used to introduce a combustion-supporting gas. A combustion-supporting gas introduction pipe 73 (see FIG. 12) or a combustion-supporting gas discharge pipe 74 (see FIG. 13) for exhaust is opened.

On the other hand, in the lower unit cell, a fuel gas introduction pipe 71 for introducing fuel gas into the fuel electrode 12 of the lower unit cell is opened in a space formed between the lower unit cell isolation separator 18 and the bottom member 17. (See FIG. 12). Further, a fuel gas discharge pipe 72 for discharging fuel gas from the fuel electrode 12 of the lower single cell is opened at a position diagonal to the opening of the fuel gas introduction pipe 71 in this space (FIG. 13). reference). Furthermore, a through-hole 181 for introducing a combustion-supporting gas into the air electrode 13 of the lower unit cell is provided on one side surface of the lower unit cell isolation separator 18 (see FIG. 12). In the diagonal direction on the side surface side, a through hole 182 for discharging the combustion-supporting gas from the air electrode 13 of the lower single cell is provided (see FIG. 13). These through-holes 181 and 182 communicate with spaces formed between the intermediate separator 1441 and the lower single cell isolation separator 18, respectively. A combustion-supporting gas introduction pipe 73 (see FIG. 12) or a combustion-supporting gas discharge pipe 74 (see FIG. 13) for discharging is opened.
In the fuel cell of Example 2, when another unit cell is further stacked on the upper surface of the upper unit cell, the lid member functions as an intermediate separator. Further, when another unit cell is further laminated on the lower surface of the lower unit cell, the bottom member functions as an intermediate separator.

  In addition, each pipe for introducing or discharging fuel gas or combustion-supporting gas into each of the upper unit cell and the lower unit cell has a structure in which a side pipe is attached to the main unit, and the upper power generation layer and Fuel gas or combustion-supporting gas is simultaneously introduced into and discharged from the lower power generation layer. Further, in the case of the second embodiment, the fuel gas introduction pipe and the fuel gas discharge pipe, and the fuel support gas introduction pipe and the fuel support gas discharge pipe are respectively circulated in the diagonal direction. It is attached to such a position. Thereby, the fuel electrode and fuel gas of each of the upper power generation layer and the lower power generation layer, and the air electrode and the combustion-supporting gas can be efficiently brought into contact with each other.

(2) Extraction of power from the fuel cell In this flat plate type SOFC stack, the fuel electrode 12 of the upper single cell is electrically connected to the intermediate separator 1441 through the nickel felt 3. Further, the intermediate separator 1441 is electrically connected to the air electrode 13 of the lower single cell via the Inconel fiber mesh 4. Thus, the upper unit cell and the lower unit cell are connected in series. Further, the stack is heated to a predetermined operating temperature, a fuel gas such as hydrogen is introduced into the fuel gas introduction pipe 71 and brought into contact with the fuel electrode, and a combustion support gas such as air is supplied into the combustion support gas introduction pipe 73. When it is introduced and brought into contact with the air electrode, an electromotive force is generated between the fuel electrode and the air electrode, and this power can be taken out to function as a power generator. Electric power is taken out to the bottom member 17 via the nickel felt 3 disposed on the lower surface of the lower unit cell on the fuel electrode side, and the Inconel fiber mesh 4 disposed on the upper surface of the upper unit cell on the air electrode side. Thus, the lid member 15 can take out the electric power of the entire stack between the lid member 15 and the bottom member 17.

(3) Operation of the fuel cell In this solid oxide fuel cell, the two power generation layers are each of the anode support type. In this structure, current can be taken out even at an operating temperature of about 750 ° C. Therefore, the lid member, various separators, and the bottom member can be formed of stainless steel such as SUS430 instead of ceramic. In each of the upper unit cell and the lower unit cell, the solid electrolyte layer and the separator are made of the Ni-based brazing material of Experimental Example 16 among the specific metal brazing materials described in [2] above. In the same manner as above, bonding is performed at 1100 ° C. in a vacuum atmosphere, and a bonding portion 82 is formed.

  Further, the upper single cell isolation separator 16, one surface of the frame 5 made of insulating ceramic, the other surface of the frame 5 and the lid member 15, the lower single cell isolation separator 18, and a frame made of insulating ceramic. 5 and the other surface of the frame 5 and the intermediate separator 1441 also use the Ni-based brazing material of Experimental Example 16 out of the specific metal brazing material described in [2] above. Bonding is performed at 1100 ° C. in an atmosphere to form a bonding portion 82. Further, the upper single cell isolation separator 16 and the intermediate separator 1441, and the lower single cell isolation separator 18 and the bottom member 17 are made of the Ni-based solder of Experimental Example 31 among the specific metal brazing materials described in [4] above. In the same manner as in Experimental Example 31, the materials were joined at 1100 ° C. in a vacuum atmosphere, and it was considered that compressive stress remained at each joint, and a tough stack structure capable of withstanding various external forces was formed. Can be formed.

Example 3 (Internal manifold type fuel cell having three stacked single cells and using a fuel electrode as a substrate)
(1) Structure of fuel cell (a) Power generation layer and various separators The appearance of the flat plate SOFC stack 103 having another structure different from the fuel cells of Examples 1 and 2 in which three power generation layers are stacked. FIG. 14 is a perspective view. 15 is a schematic diagram of the AA cross section in FIG. 14, and FIG. 16 is a schematic diagram of the BB cross section in FIG.
In the flat plate type SOFC stack 103, three single cells are stacked via intermediate separators 1442 and 1443. The power generation layer included in each single cell is made of the same material as the fuel cell of Example 1, has a square planar shape, and has a fuel electrode 12 with a thickness of 1000 μm as a substrate. The surface of the fuel electrode 12 is made of the same material as that of the fuel cell of Example 1, and the solid electrolyte layer 11 having the same shape and size in the planar direction as the fuel electrode 12 and a thickness of 30 μm is formed. . Further, the surface of the solid electrolyte layer 11 is made of the same material as that of the fuel cell of Example 1, has the same planar shape as the solid electrolyte layer 11, has a smaller dimension than the solid electrolyte layer 11, and has a thickness of A 30 μm air electrode 13 is formed.

The upper unit cell includes a nickel felt layer 3 disposed on the upper surface of the intermediate separator 1442, a fuel electrode 12 serving as a substrate, a solid electrolyte layer 11, an air electrode 13, an Inconel fiber mesh layer 4, and a lid member 15 in this order. . Further, the lid member is connected to the solid electrolyte layer 11 and the metal frame body 62 through the frame body 5 and the metal frame body 61 which are made of an MgO—MgAl ₂ O ₄ sintered body whose upper surface is an insulating ceramic. 15 has an isolation separator 16 for the upper single cell joined to 15.
The intermediate single cell includes a nickel felt layer 3 disposed on the upper surface of the intermediate separator 1443, a fuel electrode 12 serving as a substrate, a solid electrolyte layer 11, an air electrode 13, and an Inconel fiber mesh layer 4 in this order. Further, the intermediate separator is interposed through the frame 5 and the metal frame 63 made of the MgO—MgAl ₂ O ₄ sintered body whose lower surface is joined to the solid electrolyte layer 11 and the metal frame 64 and whose upper surface is an insulating ceramic. The intermediate single cell isolation separator 19 is joined to 1442.
The lower unit cell includes a nickel felt layer 3 disposed on the upper surface of the bottom member 17, a fuel electrode 12 serving as a substrate, a solid electrolyte layer 11, an air electrode 13, and an Inconel fiber mesh layer 4 in this order. Further, the lower single cell isolation separator 18 has a lower surface joined to the solid electrolyte layer 11 and the metal frame 66, and an upper surface joined to the intermediate separator 1443 via the frame 5 and the metal frame 65.

  Lid member 15, upper unit cell isolation separator 16, lower unit cell isolation separator 18, intermediate unit cell isolation separator 19, intermediate separators 1442, 1443, metal frame bodies 61, 62, 63, 64, 65, 66, and All the bottom members 17 are made of SUS430. Furthermore, the lid member 15 and the metal frame 61, the upper single cell isolation separator 16 and the metal frame 62, the metal frame 62 and the intermediate separator 1442, the intermediate separator 1442 and the metal frame 63, for the intermediate single cell Isolation separator 19 and metal frame 64, metal frame 64 and intermediate separator 1443, intermediate separator 1443 and metal frame 65, lower unit cell isolation separator 18 and metal frame 66, and metal frame 66 And the bottom member 17, each using the Ni-based brazing material of Experimental Example 31 of the specific metal brazing material described in [4] above, and joined at 1100 ° C. in a vacuum atmosphere as in Experimental Example 31, A joining portion 81 is formed. The metal frame 61 and the upper single cell isolation separator 16, the metal frame 63 and the intermediate single cell isolation separator 19, and the metal frame 65 and the lower single cell isolation separator 18 are the frame 5. In this case, the Ni-based brazing material of Experimental Example 16 among the specific metal brazing materials described in [2] above is used, and in a vacuum atmosphere as in Experimental Example 16, Bonding is performed at 1100 ° C. to form a bonding portion 82.

(B) Fuel gas introduction pipe or discharge pipe and combustion-supporting gas introduction pipe or discharge pipe In the upper single cell, the space formed between the upper single cell isolation separator 16 and the intermediate separator 1442 is not A fuel gas introduction pipe 71 for introducing fuel gas into the fuel electrode 12 of the cell is opened (see FIG. 15). Further, a fuel gas discharge pipe 72 for discharging the fuel gas from the fuel electrode 12 of the upper single cell is opened on the side of the space facing the opening of the fuel gas introduction pipe 71 (see FIG. 15). . Further, in the space formed between the lid member 15 and the upper unit cell isolation separator 16, a support gas introducing pipe 73 for introducing the support gas into the air electrode 13 of the upper unit cell is opened. (See FIG. 16). Further, a combustion-supporting gas discharge pipe 74 for discharging combustion-supporting gas from the air electrode 13 of the upper unit cell is opened on the side of the space facing the opening of the combustion-supporting gas introduction pipe 73. (See FIG. 16).

  Further, in the intermediate unit single cell, a fuel gas introduction for introducing the fuel gas into the fuel electrode 12 of the intermediate unit single cell is provided in the space formed between the intermediate unit single cell isolation separator 19 and the intermediate separator 1443. The tube 71 is open (see FIG. 15). Further, a fuel gas discharge pipe 72 for discharging the fuel gas from the fuel electrode 12 of the upper single cell is opened on the side of the space facing the opening of the fuel gas introduction pipe 71 (see FIG. 15). . Further, in the space formed between the intermediate separator 1442 and the isolation separator 19 for the intermediate unit single cell, the combustion supporting gas introduction pipe 73 for introducing the combustion supporting gas into the air electrode 13 of the intermediate unit single cell. Is open (see FIG. 16). Further, a combustion-supporting gas discharge pipe 74 for discharging combustion-supporting gas from the air electrode 13 of the upper unit cell is opened on the side of the space facing the opening of the combustion-supporting gas introduction pipe 73. (See FIG. 16).

Further, in the lower unit cell, a fuel gas introduction pipe 71 for introducing the fuel gas into the fuel electrode 12 of the lower unit cell is formed in a space formed between the lower unit cell isolation separator 18 and the bottom member 17. Open (see FIG. 15). A fuel gas discharge pipe 72 for discharging fuel gas from the fuel electrode 12 of the lower single cell is opened on the side of the space facing the opening of the fuel gas introduction pipe 71 (see FIG. 15). . Further, in the space formed between the intermediate separator 1443 and the lower single cell isolation separator 18, a support gas introduction pipe 73 for introducing the support gas into the air electrode 13 of the lower unit cell is opened. (See FIG. 16). Further, a combustion-supporting gas discharge pipe 74 for discharging combustion-supporting gas from the air electrode 13 of the lower unit cell is opened on the side of the space facing the opening of the combustion-supporting gas introduction pipe 73. (See FIG. 16).
In the fuel cell of Example 3, when another unit cell is further stacked on the upper surface of the upper unit cell, the lid member functions as an intermediate separator. Furthermore, when another unit cell is laminated on the lower surface of the lower unit cell, the bottom member functions as an intermediate separator.

  In addition, each pipe for introducing or discharging fuel gas or combustion-supporting gas into each of the upper unit cell, middle unit cell and lower unit cell has a structure in which a side tube is attached to the main tube. The fuel gas or the combustion-supporting gas is simultaneously introduced into and discharged from the upper power generation layer, the middle power generation layer, and the lower power generation layer. Further, in the case of the fifth embodiment, the fuel gas introduction pipe and the fuel gas discharge pipe, and the fuel support gas introduction pipe and the fuel support gas discharge pipe are respectively circulated in the opposing direction. It is attached to such a position. Thereby, each fuel electrode of each of the upper power generation layer, the middle power generation layer, and the lower power generation layer can be efficiently brought into contact with the fuel gas, and the air electrode and the combustion-supporting gas.

(2) Extraction of power from the fuel cell In this flat plate type SOFC stack, the fuel electrode 12 of the upper single cell is electrically connected to the intermediate separator 1442 through the nickel felt 3. The intermediate separator 1442 is electrically connected to the air electrode 13 of the intermediate unit single cell via the Inconel fiber mesh 4. Furthermore, the fuel electrode 12 of the intermediate unit single cell is electrically connected to the intermediate separator 1443 through the nickel felt 3. Further, the intermediate separator 1443 is electrically connected to the air electrode 13 of the lower single cell via the Inconel fiber mesh 4. In this way, the upper unit cell, the middle unit cell, and the lower unit cell are each connected in series. Further, the stack is heated to a predetermined operating temperature, a fuel gas such as hydrogen is introduced into the fuel gas introduction pipe 71 and brought into contact with the fuel electrode 12, and a combustion-supporting gas such as air is introduced into the combustion-supporting gas introduction pipe 73. Is introduced and brought into contact with the air electrode 13, an electromotive force is generated between the fuel electrode 12 and the air electrode 13, and the electric power can be taken out to function as a power generator. Electric power is taken out to the bottom member 17 via the nickel felt 3 disposed on the lower surface of the lower unit cell on the fuel electrode side, and the Inconel fiber mesh 4 disposed on the upper surface of the upper unit cell on the air electrode side. Thus, the lid member 15 can take out the electric power of the entire stack between the lid member 15 and the bottom member 17.

(3) Operation of the fuel cell In this solid electrolyte fuel cell, the three power generation layers are each of the fuel electrode support type, and in this structure, current can be taken out even at an operating temperature of about 750 ° C. Therefore, the lid member, various separators, the metal frame, and the bottom member can be formed of stainless steel such as SUS430 instead of ceramic. In each of the upper unit cell, the middle unit cell, and the lower unit cell, the solid electrolyte layer and the separator are made of the Ni-based brazing material of Experimental Example 16 among the specific metal brazing materials described in [2] above. In the same manner as in Experimental Example 16, the bonding portion 82 is formed by bonding at 1100 ° C. in a vacuum atmosphere.

  Further, the upper unit cell isolation separator 16, one side of the frame 5 made of insulating ceramic, the other side of the frame 5, a metal frame 61, the middle unit cell isolation separator 19, and an insulating ceramic. One surface of the frame 5 and the other surface of the frame 5 and the metal frame 63 and the lower single cell isolation separator 18, one surface of the frame 5 made of insulating ceramic, and the other surface of the frame 5 and the metal frame The body 65 also uses the Ni-based brazing material of Experimental Example 16 among the specific metal brazing materials described in [2] above, and is joined at 1100 ° C. in a vacuum atmosphere in the same manner as in Experimental Example 16. Is formed. Also, the lid member 15 and the metal frame 61, the upper single cell separator 16 and the metal frame 62, the metal frame 62 and the intermediate separator 1442, the intermediate separator 1442 and the metal frame 63, the intermediate unit cell Isolation separator 19 and metal frame 64, metal frame 64 and intermediate separator 1443, intermediate separator 1443 and metal frame 65, lower single cell isolation separator 19 and metal frame 66, and metal frame 66 and the bottom member 17 are bonded to each other at 1100 ° C. in a vacuum atmosphere using the Ni-based brazing material of Experimental Example 31 among the specific metal brazing materials described in [4] above. It is considered that compressive stress remains at each joint, and a tough stack structure that can withstand various external forces can be formed.

  Further, when power is generated using the solid electrolyte fuel cells of Example 1, Example 2 and Example 3, fuel gas is introduced to the fuel electrode side, and combustion-supporting gas is introduced to the air electrode side. As fuel gas, hydrogen, hydrocarbon as a hydrogen source, mixed gas of hydrogen and hydrocarbon, fuel gas obtained by passing these gases through water at a predetermined temperature and humidified, and fuel obtained by mixing these gases with water vapor Gas etc. are mentioned. The hydrocarbon is not particularly limited, and examples thereof include natural gas, naphtha, and coal gasification gas. Further, the main components are saturated hydrocarbons having 1 to 10, preferably 1 to 7, more preferably 1 to 4 carbon atoms such as methane, ethane, propane, butane and pentane, and unsaturated hydrocarbons such as ethylene and propylene. Those having a saturated hydrocarbon as a main component are more preferable. These fuel gas may use only 1 type and can also use 2 or more types together. Moreover, you may contain inert gas, such as nitrogen and argon of 50 volume% or less.

  Examples of the combustion-supporting gas include a mixed gas of oxygen and another gas. The mixed gas may contain 80% by volume or less of an inert gas such as nitrogen and argon. Among these combustion-supporting gases, air (containing about 80% by volume of nitrogen) is preferable because it is safe and inexpensive.

  The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the present invention depending on the purpose, application, and the like. For example, the planar shape of the power generation layer or the like can be a rectangle, a circle, an ellipse, or the like, and a solid oxide fuel cell having a similar planar shape can be obtained.

It is a schematic diagram which shows the cross section of a junction part etc. at the time of joining between SUS430 molded objects using Ni type | system | group brazing material. It is a schematic diagram which shows cross sections, such as a junction part, after joining between SUS430 molded objects using a Ni-type brazing material, and heating at 800 degreeC for 100 hours. It is a schematic diagram which shows cross sections, such as a junction part at the time of joining between SUS430 molded objects using the Ni-type brazing material containing Cr. It is a schematic diagram which shows the cross section of a junction part etc. at the time of joining a SUS430 molded object and a YSZ sintered compact using the Ni-type brazing material containing Cr. It is a schematic diagram which shows cross sections, such as a junction part at the time of joining between SUS430 molded objects using Ag type brazing material. It is a schematic diagram which shows cross sections, such as a junction part at the time of joining a SUS430 molded object and a YSZ sintered compact using Ag type brazing material. It is a schematic diagram which shows cross sections, such as a junction part at the time of joining between SUS430 molded objects using the Ag type brazing material containing Cu. It is a schematic diagram which shows the cross section of the joined body which joined between the SUS430 molded objects using Ni type brazing material or Ag type brazing material. It is a schematic diagram which shows the cross section after heating the joined body of FIG. 8 at 800 degreeC for 1000 hours. 1 is a schematic diagram showing a cross section of a solid oxide fuel cell 101 of Example 1. FIG. 3 is a perspective view showing an appearance of a solid oxide fuel cell 102 of Example 2. FIG. It is a schematic diagram which shows the AA cross section of the solid oxide fuel cell 102 of FIG. It is a schematic diagram which shows the BB cross section of the solid oxide fuel cell 102 of FIG. 6 is a perspective view showing a solid oxide fuel cell 103 of Example 3. FIG. It is a schematic diagram which shows the AA cross section of the solid electrolyte form fuel cell 103 of FIG. It is a schematic diagram which shows the BB cross section of the solid oxide fuel cell 103 of FIG.

Explanation of symbols

  101, 102, 103; flat plate SOFC stack, 11; solid electrolyte layer, 12; fuel electrode, 13; air electrode, 141; separator for lamination, 142; upper separator, 143; lower separator, 1441, 1442, 1443; Separator, 15; Lid member, 16; Separation separator for upper unit cell, 161, 162; Through hole, 17; Bottom member, 18; Separation separator for lower unit cell, 181 and 182; Through hole, 19; Isolation separator, 21; fuel gas flow path, 22; combustion-supporting gas flow path, 3; nickel felt layer, 4; Inconel fiber mesh layer, 5; frame, 61, 62, 63, 64, 65, 66 Metal frame, 71; fuel gas introduction pipe, 72; fuel gas exhaust pipe, 73; support gas introduction pipe, 74; support gas exhaust pipe, 81; joining between metal parts 82; Joint between metal part and ceramic part; 9; Bonded body; 91; Metal sheet or metal molded body; 92; Ceramic sintered body; 93; Bonded layer; 931; 9411, 9412; Cr segregation layer, 942; metal oxide precipitation portion, 943; P segregation layer, 9441, 9442; Ni diffusion layer, 9451, 9552; Fe / Cr diffusion layer, 946; P segregation material, 9471, 9472; Fe diffusion layer, 9481, 9482; Pd diffusion layer, 9491, 9492; Fe-Cu-Pd reaction layer.

Claims (7)

The solid electrolyte layer 11, the fuel electrode 12 provided on one surface of the solid electrolyte layer 11, the air electrode 13 provided on the other surface of the solid electrolyte layer 11, and at least a part between the components are brazed. In a solid oxide fuel cell comprising a joining portion,
The air electrode 13 has a general formula (A _x B _1-x ) (C _y D _1-y ) O _3-δ (where A is at least one of La, Y, Sm, Gd, Pr, and Ca) , B is at least one of Sr, Ba and Ca, C is at least one of Mn, Co, Ni and Ce, D is at least one of Fe and Mn, 0.4 ≦ x ≦ 1, 0 ≦ y ≦ 0.5, 0 ≦ δ <1)), and at least a part of the joint is formed of a metal brazing material. Solid electrolyte fuel cell.   2. The solid electrolyte fuel according to claim 1, wherein the metal brazing material contains Ni and B or P, and the content of Ni is 60% by mass or more when the metal brazing material is 100% by mass. battery.   The solid electrolyte fuel cell according to claim 2, wherein the metal brazing material further contains Cr.   The joint part joins a metal part and a ceramic part, and the metal brazing material further contains at least one of Ti and Zr, and when the metal brazing material is 100 mass%, the Ti The content of Ti in the case of containing only Zr, the content of Zr in the case of containing only Zr, or the total content in the case of containing Ti and Zr is 0.5 to 10% by mass, respectively. The solid oxide fuel cell according to claim 2 or 3.   The joint part joins one metal part and another metal part, and Cr is segregated in a portion adjacent to the joint part of each of the one metal part and the other metal part. Item 5. The solid electrolyte fuel cell according to Item 3 or 4.   The joint part joins a metal part and a ceramic part, and at least one of the joint part and the vicinity of the interface between the joint part and the ceramic part has a metal contained in the metal brazing material and the The solid oxide fuel cell according to any one of claims 1 to 5, wherein an oxide of at least one of the metals contained in the metal part is deposited. The solid electrolyte fuel cell according to claim 1, wherein the joint is formed in an atmosphere having an oxygen partial pressure of 10 to 10 ⁻¹⁵ Pa.

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