JP5269621B2 - Oxygen ion conduction module and conductive bonding material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an oxygen ion permeable module in which various constitutive members are joined while holding high airtightness even in a high operation temperature region and a joining part has good conductivity, to provide a conductive joining material used for forming the joining part, and to provide a method for joining constitutive members to each other by using the joining material. <P>SOLUTION: This oxygen ion conduction module 10 includes an oxygen ion conductive ceramic material 12. The oxygen ion conductive ceramic material 12 is joined to at least one ceramic connection member 18A, B. The joining part 20 between the oxygen ion conductive ceramic material 12 and the connection member 18A, B is formed in such a state that two following components (a), (b) coexist: (a) glass in which a cristobalite crystal and/or leucite crystal are precipitated in a glass matrix; and (b) a conductive substance having at least one kind of metal element. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to an oxygen ion conductive module that selectively transmits oxygen ions, and a conductive bonding material (seal material) for forming a bonding portion in the module.

A dense ceramic material made of oxygen ion conductor having oxygen ions (typically O ²⁻ ; also called oxide ions) is provided as a basic component of an oxygen ion conduction module (oxygen ion conduction device). Thus, oxygen can be selectively permeated and separated from the oxygen-containing gas (such as air) supplied to one surface to the other surface.

  A typical example of the oxygen ion conduction module is an oxygen separation device. Such an oxygen separation device includes an oxygen separation membrane element, and the oxygen separation membrane element is made of an oxygen separation membrane material formed by forming an oxygen ion conductor in a film shape (typically a porous substrate). ) Is provided. Such an oxygen separation device can be suitably used as an effective oxygen purification means replacing, for example, a cryogenic separation method or a PSA (Pressure Swing Adsorption) method. When constructing an oxygen separation device having such a configuration, the oxygen separation element is joined to various members and has a joint (seal) portion that can maintain high hermeticity even in a high temperature range (for example, 800 ° C. to 1000 ° C.). Need to be built. As a joining (seal) material for forming such a highly airtight joint, for example, a glass material or a metal material has been studied.

Alternatively, as a typical example of the oxygen ion conduction module, there is a solid oxide fuel cell (hereinafter, also simply referred to as “SOFC”). As a basic structure (single cell), SOFC has a porous air electrode (cathode) formed on one side of a dense solid electrolyte (eg, a dense membrane layer) made of an oxygen ion conductor, and the other side. A porous fuel electrode (anode) is formed. 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.

  The SOFC is typically operated as a stack in which a plurality of single cells are stacked to obtain a high voltage. In an SOFC having such a stack structure, an interconnector is used to connect single cells. The interconnector serves as a separator that separates the oxidizing gas (oxygen-containing gas such as air) and reducing gas (fuel gas such as hydrogen) at the same time as connecting the single cells physically and electrically. Also bears. The interconnector and the surface of the solid electrolyte facing the interconnector need to be joined (sealed) so as to ensure high airtightness even when operated in a high temperature range (usually 800 ° C. to 1200 ° C.). There is.

By the way, as a solid electrolyte for SOFC, a solid electrolyte made of a zirconia-based material (typically yttria-stabilized zirconia; YSZ) is widely used due to high chemical stability and mechanical strength.
In addition, the interconnector as described above has high chemical durability and conductivity in an oxidation-reduction atmosphere at such a high temperature, considering that the SOFC operates in the high temperature range as described above, and is similar to a solid electrolyte material. It is preferably formed from a material having properties such as having a thermal expansion coefficient. As such an interconnector material, a metal material (for example, a heat-resistant alloy or an Ag (silver) composite) or a ceramic material has been proposed. As such ceramic materials, various perovskite oxide materials have been proposed as shown in Patent Documents 1 to 9. For _{example, La 1-p A p CrO} 3 ( where, A is at least one selected from the group consisting from Mg, Ca, Sr, Ba, a 0 ≦ p <1.) Such as lanthanum chromite (LaCrO ₃ ) Perovskite type oxides of the system, or perovskite type oxides whose B sites are partially substituted (doped) with other elements (for example, Si, Ti, Co, Ni or Zr), and further MTiO ₃ (where M is at least one selected from the group consisting of Li, Ca, Cu, Sr, Ba, La, Ce, Pb, and Bi.) And the like, and titanate-based perovskite oxides.
In addition, the joining material between the solid electrolyte and the interconnector has a thermal expansion coefficient similar to that of the solid electrolyte material and the interconnector material, and has a high hermeticity even at the SOFC operating temperature or higher (sealing). Materials that can be made are preferred. For example, as shown in Patent Documents 10 to 16, a mixture of stabilized zirconia and glass, a mixture of a solid electrolyte material and an interconnector material, and a mixture of glass and metal have been proposed.

JP-A-8-55629 JP-A-8-83620 JP-A-8-190922 JP-A-10-125340 Japanese Patent Laid-Open No. 11-3720 JP 2003-288919 A JP 2003-331874 A JP 2006-310090 A JP 2007-39279 A JP-A-5-330935 JP-A-8-134434 JP-A-9-129251 Japanese Patent Laid-Open No. 11-154525 JP 2004-39573 A Special table 2008-527680 Special table 2008-529256

As described above, in the oxygen ion conduction module such as SOFC, the bonding material for bonding the members constituting the module to each other has a thermal expansion coefficient close to that of the material of the module component, A material that can be bonded (sealed) while maintaining high airtightness even at a temperature higher than the operating temperature of the module is preferable. However, the above-described materials have poor heat resistance due to elution under the above operating temperature range, etc., and have extremely low electrical conductivity. There was a limited problem.

  The present invention has been made in view of such a point, and its main purpose is that various components are bonded while maintaining high airtightness over a long period of time even under a high operating temperature range. An oxygen ion conduction module having good conductivity is provided. It is another object of the present invention to provide a conductive bonding material used for forming a joint having such high airtightness and conductivity. Furthermore, it is another object to provide a method for joining constituent members of an oxygen ion conduction module using such a conductive joining material.

In order to achieve the above object, an oxygen ion conductive module provided by the present invention includes a ceramic material having oxygen ion conductivity, and the oxygen ion conductive ceramic material is bonded to at least one ceramic connecting member. doing. Moreover, in the oxygen ion conduction module, the joint between the oxygen ion conductive ceramic material and the connection member has the following two components:
(A). A glass characterized in that cristobalite crystals and / or leucite crystals are precipitated in a glass matrix; and (b). A metal compound (inorganic compound) such as a metal oxide having at least one metal element as a conductive substance capable of functioning the junction as an electron conduction path ;
Are formed together.

Here, the “oxygen ion conduction module” is a module (component, device) provided with a ceramic material having oxygen ion conductivity (oxygen ion conductor) as a basic constituent member, on one surface of the ceramic material. A module (configuration in which oxygen is selectively separated from the oxygen-containing gas in the process of supplying oxygen-containing gas (air, etc.) and permeating through the ceramic material, and only oxygen is permeated to the other surface of the ceramic material. Device).
In the oxygen ion conductive module according to the present invention, the joint between the oxygen ion conductive ceramic material and the connecting member is (a) a cristobalite crystal (SiO ₂ ) and / or a leucite crystal (KAlSi ₂ O ₆ ) in a glass matrix. Are deposited by mixing two components of glass (hereinafter referred to as “crystal-containing glass”) and (b) a conductive material having at least one metal element. Such a joint includes the above-mentioned component (a) (for example, the cristobalite and / or leucite fine crystals are precipitated in a dispersed state in the glass matrix), so that a temperature range of 800 ° C. or higher, for example, 800 ° C. to It is difficult to flow in a temperature range of 1000 ° C. Therefore, according to the oxygen ion conduction module, even when the operating temperature of the module reaches the above temperature range, there is no possibility that the joint portion between the oxygen ion conductive ceramic material and the connection member is eluted, and the mechanical strength is improved. Can be realized.

  In addition, since the joint portion contains the component (b) (for example, deposited and dispersed in the glass matrix in a conductive state), the joint portion has conductivity in the temperature range. Therefore, according to this oxygen ion conduction module, the junction between the oxygen ion conductive ceramic material and the connection member can function as an electron conduction path. That is, the oxygen ion conductive ceramic material and the connecting member can be joined without restricting the joining location and joining area, and the two members can be electrically connected to each other at the joining portion.

In a preferred embodiment of the oxygen ion conduction module disclosed herein, the glass mixed in the joint portion has the following composition at a mass ratio in terms of oxide:
SiO ₂ 60 to 75 wt%;
Al ₂ O ₃ 10-20% by mass;
Na ₂ O 3-10% by mass;
K ₂ O 5-15% by mass;
MgO 0 to 3% by mass;
CaO 0 to 3% by mass;
Is substantially composed of.
The joint where the crystal-containing glass having such a composition coexists has a thermal expansion coefficient that approximates the thermal expansion coefficient (thermal expansion coefficient) of the oxygen ion conductive ceramic material to be joined and the connection member. For this reason, the oxygen ion conduction module having the above-described configuration disclosed herein is repeatedly used in a high temperature range (for example, 800 ° C. to 1000 ° C.), and the temperature rises between the use temperature range and a temperature when not in use (room temperature). Even if the temperature and the temperature decrease are repeated, the leakage of gas from the joined portion (seal portion) between the oxygen ion conductive ceramic material and the connecting member can be prevented, and high airtightness can be maintained for a long time. Therefore, the oxygen ion conduction module having such a configuration can realize excellent heat resistance and durability.

In a more preferable aspect of the oxygen ion conduction module disclosed herein, the conductive material mixed in the joint is Cu (copper), Co (cobalt), Fe (iron), Ni (nickel), Cr (chromium). ), Ir (iridium), Sn (tin), and Nb (niobium), and a compound (for example, an oxide) containing at least one metal element selected from the group consisting of Nb (niobium).
In the oxygen ion conduction module having such a configuration, a metal compound (inorganic compound) such as a metal oxide containing a metal element as described above is mixed in the joint in the conductive state as the conductive substance. Thus, such a conductive substance has low reactivity with the mixed crystal-containing glass even in the high temperature range, and has good conductivity even in the high temperature range. Therefore, according to such an oxygen ion conductive module, the junction between the oxygen ion conductive ceramic material and the connecting member achieves excellent heat resistance and durability (long-term airtightness) without deterioration even in the high temperature range. At the same time, good conduction can be obtained between the oxygen ion conductive ceramic material and the connecting member as an excellent electron conduction path in the joint.

In addition, any one of the oxygen ion conduction modules disclosed herein suitably functions as a solid oxide fuel cell (hereinafter sometimes simply referred to as “SOFC”).
That is, in the oxygen ion conductive module that functions as an SOFC, the oxygen ion conductive ceramic material is a zirconia-based (eg, yttria stabilized zirconia (YSZ)) solid electrolyte. The ceramic connecting member is made of an perovskite oxide (for example, lanthanum (La) or lanthanum chromite oxide in which a part of chromium (Cr) is substituted or not substituted with an alkaline earth metal). It is a connector. Furthermore, the conductive bonding material for bonding the oxygen ion conductive ceramic material and the connecting member functions as the interconnector.
In the oxygen ion conductive module having such a function, the oxygen ion conductive ceramic material as a solid electrolyte in a high temperature range of 800 ° C. to 1200 ° C. (preferably 800 ° C. to 1000 ° C.), which is a preferable use temperature range of the SOFC. In addition to the heat resistance and durability as described above, the joint between the connecting member and the connecting member as the interconnector has excellent conductivity and acts as a part of the interconnector. Therefore, according to such an oxygen ion conduction module, it is possible to provide a suitable SOFC excellent in heat resistance, durability, and conductivity by forming the joining portion without restricting the joining location and joining area. .

In a further preferred aspect of the oxygen ion conduction module disclosed herein, the electrical conductivity of the joint at a temperature of 900 ° C. is 0.01 S / cm to 1.5 S / cm.
By providing a joint having such conductivity, an oxygen ion conduction module that exhibits good conductivity even when used in a high temperature range of about 900 ° C. can be provided.

In a further preferred embodiment of the oxygen ion-conducting device disclosed herein, wherein the thermal expansion coefficient of the bonding portion is ^{9 × 10 -6 / K~14 × 10} -6 / K.
Such a thermal expansion coefficient (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, from zirconia-based materials such as YSZ. It approximates the thermal expansion coefficient of a connecting member made of an oxygen ion conductive ceramic material and a perovskite oxide (for example, lanthanum chromite oxide). Thereby, the oxygen ion conduction module which is excellent in the heat resistance of the junction part (seal part), durability, and electroconductivity can be provided.

This invention provides the joining material which solves the said subject as another side surface. That is, the bonding material is a conductive bonding material for bonding the oxygen ion conductive ceramic material constituting the oxygen ion conductive module and at least one ceramic connecting member. The conductive bonding material disclosed herein includes SiO ₂ , Al ₂ O ₃ , Na ₂ O, and K ₂ O as essential constituent components, preferably at least one of MgO and CaO as additional constituent components. A glass containing a cristobalite crystal and / or a leucite crystal precipitated in a glass matrix and a conductive substance are formed in a mixed manner. Particularly preferably,
(A) The following composition in mass ratio in terms of oxide:
SiO ₂ 60 to 75 wt%;
Al ₂ O ₃ 10-20% by mass;
Na ₂ O 3-10% by mass;
K ₂ O 5-15% by mass;
MgO 0 to 3% by mass;
CaO 0 to 3% by mass;
A glass substantially composed of: cristobalite crystals and / or leucite crystals precipitated in a matrix of the glass; and (b). A conductive material containing at least one kind of metal element is mixed.
Here, in a preferred embodiment of the conductive bonding material, a paste-like (also referred to as slurry) bonding material (sealing material) containing as a main component a bonding material material containing the components (a) and (b). ).
By using the bonding material having such a configuration, the oxygen ion conductive ceramic material and the connecting member can be bonded in a state having good conductivity as described above, and mechanical strength, heat resistance and It is possible to provide an oxygen ion conduction module provided with the above-described joint having excellent durability.

In a preferable aspect of the conductive bonding material disclosed herein, the conductive material includes at least one metal selected from the group consisting of Cu, Co, Fe, Ni, Cr, Ir, Sn, and Nb. A compound.
In the conductive bonding material having such a structure, the substance (compound) containing the metal as described above is mixed in the crystal-containing glass in a conductive state, so that the crystal-containing glass ( The oxygen ion conductive ceramic material and the connecting member can be bonded in a state of low reactivity with the component (a)) and good conductivity. This makes it possible to provide a suitable oxygen ion conduction module provided with the junction as an excellent electron conduction path in the high temperature range. In particular, a compound containing copper (Cu) or cobalt (Co) as a metal component is preferable.

In a preferred embodiment of the conductive bonding material disclosed herein, the content of the conductive material is 10% by mass to 90% in terms of 100% by mass of the conductive bonding material in terms of metal element oxide. % By mass.
The conductive bonding material having such a composition can achieve both bonding performance and conductive performance. Thus, in this aspect, it is possible to provide a more preferable oxygen ion conduction module provided with a joint having improved conductivity in addition to the joining performance.

The present invention also provides a method for joining an oxygen ion conductive ceramic material constituting an oxygen ion conductive module and at least one ceramic connecting member.
That is, the method provided by the present invention provides any one of the conductive bonding materials disclosed herein, and a bonding portion between the oxygen ion conductive ceramic material and the connection member. And the applied conductive bonding material is baked in a temperature range of 1000 ° C. or higher, whereby the conductive bonding is performed at the connection portion between the oxygen ion conductive ceramic material and the connection member. Forming a joint for blocking gas flow made of a material.
In the method having such a configuration, an oxygen ion conduction module having the above-described effects can be provided by firing the conductive bonding material applied to the connection portion in a high temperature range of 1000 ° C. or higher.
Accordingly, the present invention provides, as another aspect, an oxygen ion conductive ceramic material (for example, zirconia-based material) and at least one ceramic (for example, lanthanum chromite-based perovskite-type oxidation) using the conductive bonding material disclosed herein. The manufacturing method of the oxygen ion conduction module characterized by joining the connection member made from a thing) by the said joining method. Here, the firing temperature of the conductive bonding material is preferably equal to or higher than the operating temperature range (for example, 800 ° C. to 1000 ° C.) of the oxygen ion conduction module.

It is sectional drawing which shows typically flat type SOFC (single cell) as a typical example. It is a perspective view which shows typically the structure of the conjugate | zygote (sample) produced in one Example.

  Hereinafter, preferred embodiments of the present invention will be described. In addition, matters other than matters specifically mentioned in the present specification (for example, a method for preparing a glass component constituting a conductive bonding material) and matters necessary for carrying out the present invention (a method for mixing raw material powders and ceramics) Can be understood as a design matter of those skilled in the art based on the prior art in this field. The present invention can be carried out on the basis of the contents first disclosed in the present invention and common technical knowledge in the field.

  In the oxygen ion conduction module of the present invention, the joint between the oxygen ion conductive ceramic material and the ceramic connecting member constituting the module is (a) cristobalite crystal and / or leucite crystal is precipitated in the glass matrix. It is characterized by being formed by a mixed material of the above-mentioned crystal-containing glass and (b) a conductive substance, and other components such as an oxygen ion conductive ceramic material and a ceramic connecting member The shape and composition can be arbitrarily determined in light of various criteria. For example, in an oxygen separation device which is a typical example of such an oxygen ion conduction module, an oxygen ion conductive ceramic material which is a perovskite oxide is formed into a film shape and acts as an oxygen separation membrane material, and is similar to the membrane material. A porous connecting member mainly composed of magnesia, zirconia, silicon nitride, silicon carbide or the like is formed in a cylindrical shape and can act as a base material for the oxygen separation membrane material. Alternatively, in a fuel cell (typically SOFC) which is another typical example of the oxygen conduction module, an oxygen ion conductive ceramic material formed in a predetermined shape as a solid electrolyte is joined to a connecting member as an interconnector. By doing so, a stack can be configured.

The conductive bonding material disclosed herein is a conductive bonding material for bonding the oxygen ion conductive ceramic material constituting the oxygen ion conductive module and at least one ceramic connecting member to each other as described above. , (a) cristobalite in the glass matrix (SiO ₂₎ crystals and / or leucite (KAlSi ₂ O ₆ or _{4SiO 2 · Al 2 O 3 ·} K 2 O) glass composition having a composition crystals can precipitate (crystals containing Glass) and (b) a conductive material.

First, the crystal-containing glass that is the component (a) will be described.
When an oxygen ion conduction module typified by an oxygen separator or SOFC is used in a relatively high temperature range, for example, 800 to 1200 ° C., preferably 800 to 1000 ° C. (for example, 900 to 1000 ° C.), the component (a) As such, a glass having a composition that hardly melts in the 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 component (a) 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 10% 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%.

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, if the Al ₂ O ₃ content is too high, the chemical resistance of the joint may be lowered. 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. The K ₂ O content is preferably 5 to 15% by mass of the entire glass composition, and particularly preferably about 7 to 10%. Further, it is preferable (typically Na 2 _O) other alkali metal oxides is 3-10 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 additives 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% by mass or less of the entire glass composition.

In addition to the above-described oxide components, components that are not essential in the practice of the present invention (for example, B ₂ O ₃ , ZnO, Li ₂ O, Bi ₂ O ₃ , SrO, SnO, SnO ₂ , CuO, Cu ₂ O). , it can be added according to the _{TiO 2, ZrO 2, La 2} O 3) a variety of purposes.
Preferably, the thermal expansion coefficient of the glass constituting the joint between the oxygen ion conductive ceramic material and the connecting member in the oxygen ion conductive module approximates the thermal expansion coefficient of the oxygen ion conductive ceramic material and the connecting member. The above-mentioned components are mixed to prepare crystal-containing glass (component (a)). For example, when the oxygen ion conductive ceramic material is a zirconia material such as YSZ and the connecting member is a perovskite oxide such as a lanthanum chromite oxide, it is formed by approximating these thermal expansion coefficients. Thermal expansion coefficient (average value between room temperature (25 ° C.) based on differential expansion method (TMA) to glass softening point (for example, 450 ° C.)) of 9 × 10 ⁻⁶ / K to 14 × The crystal-containing glass may be prepared by adjusting the composition so as to be 10 ⁻⁶ / K.

Next, the component (b) constituting the conductive bonding material will be described.
The conductive material as the constituent component (b) does not easily react with the crystal-containing glass under the use temperature range (800 ° C. to 1200 ° C.) of the oxygen ion conduction module, and exhibits conductivity under the temperature range. What has (that is, what can exist in the state which has electroconductivity in this temperature range) is preferable. As such a conductive substance, for example, a metal compound (one type or two or more types) containing a metal element (one type or two or more types) such as Cu, Co, Fe, Ni, Cr, Ir, Sn, or Nb is used. May be included). Among those exemplified above, a more preferable metal component (metal element) is Cu or Co.
Further, the content of the conductive material is not particularly limited as long as it has the bonding ability required for the bonding material (that is, depending on the content of the glass component), but the metal constituting the conductive material. In terms of element oxide, about 10% by mass to 90% by mass when the total mass of the conductive bonding material is 100% by mass is preferable. For example, according to the bonding material containing the conductive material at such a content rate, preferably, the bonding portion having a conductivity of 0.01 S / cm to 1.5 S / cm under a temperature condition of 900 ° C. Can be formed.

There is no particular limitation on the method for producing the conductive bonding material having the above composition, and a conventional crystal-containing glass (that is, a glass composition having a composition capable of depositing cristobalite crystals and / or leucite crystals) is produced. A similar 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 obtained admixture (powder) 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, cristobalite is heated in the glass matrix by heating the glass powder from room temperature to about 100 ° C. at a heating rate of about 1 to 5 ° C./min and holding it in the temperature range of 800 to 1000 ° C. for about 30 to 60 minutes. Crystals and / or leucite crystals can be precipitated.
The leucite-containing glass thus obtained can be formed into a desired form by various methods. For example, a powdery glass composition (component (a)) 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.

To the powdery glass composition thus obtained, the conductive material as the component (b) is added at a blending ratio determined according to the desired conductivity, and then an appropriate amount of water is added to the above. Mix using the same ball mill. Thereafter, by carrying out a drying treatment for a predetermined time, the powdery conductive bonding material according to the present invention can be obtained.
The conductive bonding material of the powdery body thus obtained is typically prepared in the form of a paste, like the conventional bonding material, and is connected to the connection portion between the oxygen ion conductive ceramic material and the connection member. Can be applied. For example, a paste can be prepared by mixing an appropriate binder or solvent with the obtained conductive 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 conductive bonding material disclosed here can be used in the same manner as the conventional bonding material of this type. Specifically, the oxygen ion conductive ceramic material to be bonded and the bonded portion of the connecting member are contacted and connected to each other, and a conductive bonding material prepared in a paste form is applied to the connected portion. Then, the coated material made of the conductive bonding material is dried at an appropriate temperature (typically 60 to 100 ° C.), and then the temperature range of 1000 ° C. or higher, preferably the operating temperature range of the oxygen ion conduction module (for example, 800 ° C.). A temperature range higher than ˜1000 ° C. or higher, typically 800 ° C. to 1200 ° C., where glass does not flow out (for example, when the use temperature range is up to about 1000 ° C., typically Specifically, when the operating temperature range is approximately 1200 ° C to 1000 ° C to 1200 ° C, the firing is typically performed at 1200 ° C to 1300 ° C. This forms a joint (seal part) that blocks gas flow (that is, there is no gas leak) at the connection part between the oxygen ion conductive ceramic material and the connection member. Since this junction has good conductivity in the above temperature range, it can function as an electron conduction path between the oxygen ion conductive ceramic material and the connection member. That is, by using such a conductive bonding material, the oxygen ion conductive ceramic material and the connecting member are bonded without limiting the location and the bonding area to be bonded, and conduction between the two members is achieved at the bonded portion. Can do.

An oxygen ion conduction module having a joint formed by using the conductive joint material as described above will be described in detail by taking as an example a case where the module functions as an SOFC.
In such SOFC, the joint (sealing part) between the zirconia solid electrolyte (oxygen ion conductive ceramic material) and the interconnector (connecting member) made of lanthanum chromite oxide is used for the crystal-containing glass and the conductive substance. It is characterized by being formed by mixing. The shape and composition of other components such as the fuel electrode (anode) and the air electrode (cathode) can be arbitrarily determined in light of various standards.

As a solid electrolyte for constructing the SOFC disclosed herein, a dense layer having high oxygen ion conductivity and no gas permeability can be formed in both an oxidizing (air) atmosphere and a reducing (fuel gas) atmosphere. Consists of materials. As this suitable material, a zirconia-based solid electrolyte is used. Typically, zirconia (YSZ) stabilized with yttria (Y ₂ O ₃ ) is used. Other suitable zirconia-based solid electrolytes include zirconia (CSZ) stabilized with calcia (CaO), zirconia (SSZ) stabilized with scandia (Sc ₂ O ₃ ), and the like.

As an interconnector (separator) for constructing the SOFC disclosed herein, a lanthanum chromite-based perovskite oxide that physically shuts off an oxygen supply gas (for example, air) and a fuel gas and has electronic conductivity (Lantan chromite oxide) is used.
Such a lanthanum chromite oxide is represented by a general formula: La _(1-x) Ma _(x) Cr _(1-y) Mb _(y) O ₃ , and Ma and Mb in the formula are the same or different from each other. 1 or 2 or more types of alkaline earth metals, and x and y are 0 ≦ x <1 and 0 ≦ y <1, respectively. That is, the lanthanum chromite oxide may be lanthanum or a lanthanum oxide in which a part of chromium is substituted with an alkaline earth metal. Preferable examples include LaCrO ₃ or an oxide (lanthanum calcia chromite) in which Ma or Mb is calcium (Ca), such as La _0.8 Ca _0.2 CrO ₃ . In the above general formula, the number of oxygen atoms is shown to be 3, but in actuality, the number of oxygen atoms in the composition ratio may be 3 or less (typically less than 3).

The fuel electrode and 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. Porous bodies made of these materials are used as a fuel electrode and an air electrode, respectively.

The manufacturing of the SOFC single cell and the stack thereof may be in accordance with 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, an air electrode, a fuel electrode, and a separator can be formed by various methods conventionally used.
For example, a YSZ molded body formed by extrusion molding or the like using a molding material made of a predetermined material (for example, a YSZ powder having an average particle diameter of about 0.1 to 10 μm, a binder such as methyl cellulose, a solvent such as water) is subjected to atmospheric conditions. It calcinates in a suitable temperature range (for example, 1300-1600 degreeC) below, and produces the solid electrolyte of a predetermined shape (for example, plate shape or tubular shape).
A slurry for forming an air electrode made of a predetermined material (for example, the perovskite oxide powder having an average particle size of about 0.1 μm to 10 μm, a binder such as methyl cellulose, a solvent such as water) is applied to one surface of the solid electrolyte. Then, a porous film-like air electrode is formed by firing in an appropriate temperature range (for example, 1300 to 1500 ° C.) under atmospheric conditions.
Next, a fuel electrode is formed on the other surface of the solid electrolyte (surface not forming the air electrode) by an appropriate method using an atmospheric pressure plasma spraying method, a low pressure plasma spraying method, or the like. For example, the porous membrane fuel electrode made of the cermet material is formed by spraying the raw material powder melted by the plasma onto the surface of the solid electrolyte.

  Further, an interconnector having a predetermined shape can be produced by the same method as that for the solid electrolyte. For example, a molded body formed by extrusion molding or the like using a molding material made of a predetermined material (for example, a lanthanum chromite oxide powder having an average particle diameter of about 0.1 μm to 10 μm, a binder such as methyl cellulose, a solvent such as water) Firing is performed in an appropriate temperature range (for example, 1300 to 1600 ° C.) under atmospheric conditions to produce a separator having a predetermined shape (for example, a plate or a tube).

Then, by using the conductive bonding material according to the present invention, by joining the produced interconnector to a solid electrolyte, a single cell and a stack of SOFC, which is a typical example of the oxygen ion conduction module according to the present invention, are obtained. Can be manufactured. For example, as schematically shown in FIG. 1, as a typical example of SOFC, an air electrode 14 is provided on one surface of a plate-shaped solid electrolyte (that is, an oxygen ion conductive ceramic material) 12, and a fuel electrode 16 is provided on the other surface. Can be provided, and a fuel cell (SOFC) 10 including interconnectors (that is, connection members) 18A and 18B joined to the solid electrolyte 12 via a joint (joining material) 20 can be provided. An oxygen supply gas (typically air) flow path 2 is formed between the air electrode 14 and the air electrode side separator 18A, and a fuel gas is provided between the fuel electrode 16 and the fuel electrode side interconnector 18B. A (hydrogen supply gas) flow path 4 is formed.
Note that the SOFC disclosed here is a single cell constituting the SOFC (for example, a single cell constituting unit including an interconnector previously joined to a solid electrolyte) or a single cell constituting the SOFC (typically Can include a SOFC stack in which a plurality of interconnectors in a state of being joined to a solid electrolyte that constitutes the single cell are stacked.

  EXAMPLES Examples relating to the present invention will be described below, but the present invention is not intended to be limited to those shown in the following examples. In the following examples, since the main purpose is to evaluate the performance of the bonding material provided by the present invention, a specimen including a solid electrolyte and a member corresponding to a separator was produced instead of the actual SOFC.

<Preparation of YSZ solid electrolyte>
A general binder (here, polyvinyl alcohol (PVA) was used) and a solvent (here, water) were added to 3-8 mol% Y-stabilized zirconia powder (average particle size: about 1 μm) and kneaded. Subsequently, this kneaded product was press-molded to obtain a plate-shaped molded body having a length of about 30 mm × width of 30 mm × thickness of about 3 mm. And this molded object was baked at 1400-1600 degreeC (here maximum baking temperature: about 1400 degreeC) in air | atmosphere. After firing, the surface of the fired product was polished to produce a thin plate-like solid electrolyte 32 (FIG. 2) made of YSZ having a desired external dimension (length 30 mm × width 30 mm × thickness 1 mm).

<Production of interconnector equivalent member>
A general binder (here, polyvinyl alcohol (PVA) was used) and a solvent (here, water) were added to La _0.8 Ca _0.2 CrO ₃ powder (average particle size: about 1 μm) and kneaded. did. Subsequently, this kneaded product was press-molded to obtain a plate-shaped molded body having a length of about 30 mm × width of 30 mm × thickness of about 3 mm. And this molded object was baked at 1400-1600 degreeC (here maximum baking temperature: about 1400 degreeC) in air | atmosphere. After firing, the surface of the fired product was polished to produce a thin plate member 38 (FIG. 2) made of lanthanum calcia chromite having a desired external dimension (length 30 mm × width 30 mm × thickness 1 mm).

<Preparation of paste-like conductive bonding material>
SiO ₂ powder, Al ₂ O ₃ powder, Na ₂ CO ₃ powder, K ₂ CO ₃ powder, MgCO ₃ powder, and CaCO ₃ powder having an average particle diameter of about 1 to 10 μm are respectively mixed with the following blending ratios, that is, oxides. 60-75 _{wt%, Al 2 O 3;;} SiO 2 in terms of 10 to 20 _wt%, Na 2 O; _{3~10 wt%, K} 2 O 3; _5~15 wt%, MgO; 0 to 3 wt% ; CaO; mixed at 0 to 3% by mass to prepare a raw material powder of the crystal-containing glass of the component (a).
Next, the raw material powder was melted in a temperature range of 1000 to 1500 ° C. (here, 1450 ° C.) to form glass. Thereafter, the glass was pulverized and subjected to a crystallization heat treatment in a temperature range of 800 to 1000 ° C. (here, 850 ° C.) for 30 to 60 minutes. As a result, 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.

Next, copper oxide (manufactured by Wako Pure Chemical Industries, Ltd.) and cobalt oxide (manufactured by Wako Pure Chemical Industries, Ltd.) are prepared as metal oxides, and the metal oxides are contained at the contents shown in Table 1 below. And a total of 10 types of samples (Samples 1 to 10) were prepared. Further, a commercially available heat-resistant glass (Corning heat-resistant glass (registered trademark:. PYREX) hereinafter referred to as "Pyrex glass") was prepared, the copper oxide and cobalt oxide in such a Pyrex glass content shown in Table 1 Each was blended to prepare two types of samples (Samples 12 and 13). For comparison, a sample (sample 11) made of the crystal-containing glass not containing the metal compound was prepared. The “content ratio” in Table 1 is the content ratio of the conductive substance contained in the bonding material, and the content ratio in terms of metal oxide relative to the total amount of raw material powder constituting the conductive bonding material (that is, metal Content ratio as an oxide) (that is, mass ratio [%] of copper oxide (or cobalt oxide ) to the total amount) .

  Next, in Samples 1 to 13, 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) with respect to 40 parts by mass of each sample. A total of 13 types of paste-like bonding materials corresponding to samples 1 to 13 in Table 1 were produced.

<Joint treatment>
The above 13 types of pastes were used as bonding materials for bonding treatment. Specifically, as shown in FIG. 2, the paste-like bonding material 40 is applied and bonded to two opposite side portions of the thin plate-like separator-equivalent member 38 having the same shape as the produced thin plate-like solid electrolyte 32. . And after drying at 80 degreeC, it baked at 1000-1100 degreeC temperature range (here 1050 degreeC) in air | atmosphere for 1 hour.
As a result, when any sample paste is used, the firing is completed without causing the joining material to flow out, and the joining portion 40 is formed at a pair of side portions facing each other between the two members 32 and 38 bonded together. A specimen (joined body) 30 was obtained (FIG. 2).
Here, in the samples 1 to 11, the elution of the joint portion 40 was not observed after cooling at room temperature.
Here, the thermal expansion coefficient (however, an average value between room temperature (25 ° C.) and 450 ° C. based on the differential expansion method (TMA)) obtained using the pastes of samples 1 to 10 is any Was also in the range of 9 × 10 ⁻⁶ / K to 14 × 10 ⁻⁶ / K. The YSZ solid electrolyte used here had a thermal expansion coefficient of 10.2 × 10 ⁻⁶ / K under the same conditions. 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 40 was performed on a total of 13 types (samples 1 to 13) of the specimens (joints) 30 constructed as described above. Specifically, a gas pipe (not shown) was sealed with an epoxy resin in an opening where the joint 40 of the specimen (joint) 30 was not formed. Then, air is supplied from the gas pipe to the hollow portion 35 between the members 32 and 38 of the specimen 30 under a pressure of 0.2 MPa, and the specimen 30 is submerged in the water in that state, and whether or not bubbles are generated in the water. Was examined visually.
As a result, no leakage of gas (air) was observed for Samples 1 to 10 composed of crystal-containing glass as a glass component and a conductive material, and Sample 11 composed only of crystal-containing glass. On the other hand, in Samples 12 and 13 containing Pyrex glass as a glass component, bubble generation from the surface of the joint 40, that is, gas (air) leakage was observed.

<Conductivity measurement>
Next, the powdery samples 1 to 13 were each press-molded into a cylindrical shape having a diameter of 3 mm and a height of 20 mm, and these were fired at 900 ° C. to 1100 ° C. to obtain 13 fired bodies corresponding to the samples 1 to 13. Kinds were made. First, after applying a platinum paste serving as an electrode on the surface of the sample 1, a platinum wire for connecting a current terminal and a voltage terminal was attached to the electrode portion, and baked at 850 to 1100 ° C. for 10 to 60 minutes. Conductivity [S / cm] was determined by a DC four-terminal method in an apparatus adjustable to temperature. The conductivity in Samples 2 to 13 was also determined in the same manner as described above. Table 1 shows the measurement results of conductivity under a constant temperature condition (900 ° C.).
As a result, conductivity was recognized in all of Samples 1 to 10 and Samples 12 and 13 containing the conductive substance. Moreover, about the samples 1-10, it was confirmed that electrical conductivity also rises as the content rate of a copper oxide or a cobalt oxide becomes large. From this result, when using a conductive bonding material having a low content of conductive material, the thickness of the bonding portion 40 is arbitrarily changed according to the magnitude of the conductivity, and the power generation resistance of the cell is not adversely affected. It can be suitably used by adjusting the conductivity to the extent.

  As described above, according to the present embodiment, the zirconia solid electrolyte and the interconnector made of the lanthanum chromite oxide are joined while ensuring sufficient airtightness without causing gas leakage (that is, the joining portion is formed). In addition, conductivity can be imparted to the joint. For this reason, it is possible to provide a suitable SOFC (single cell, stack) having excellent mechanical strength and airtightness, and having good conductivity in which the joint portion can act as a part of the interconnector.

2 Oxygen supply gas channel 4 Fuel gas channel 10 SOFC
12 Solid Electrolyte 14 Air Electrode 16 Fuel Electrode 18A, 18B Separator 20 Bonding Material (Junction)
30 Joint (Specimen)
32 Solid electrolyte 35 Hollow part 38 Separator equivalent member 40 Joining material (joining part)

Claims (8)

An oxygen ion conduction module comprising a ceramic material having oxygen ion conductivity,
The oxygen ion conductive ceramic material is bonded to at least one ceramic connecting member,
The joint between the oxygen ion conductive ceramic material and the connecting member has the following two components:
(A). A glass characterized in that cristobalite crystals and / or leucite crystals are precipitated in a glass matrix; and (b). Conductive metal oxide having at least one metal element selected from the group consisting of Cu, Co, Fe, Ni, Cr, Ir, Sn, and Nb as a conductive substance capable of causing the junction to function as an electron conduction path ;
There are formed in a mixed manner,
The content rate of the said conductive metal oxide is an oxygen ion conduction module which is 10 mass%-90 mass% by the oxide conversion of the said metal element by making the total amount of the said glass and conductive metal oxide into 100 mass% . The glass mixed in 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 mass;
Na ₂ O 3-10% by mass;
K ₂ O 5-15% by mass;
MgO 0 to 3% by mass;
CaO 0 to 3% by mass;
The oxygen ion conduction module according to claim 1, substantially consisting of: The oxygen ion conduction module according to claim 1 or 2 , wherein the electrical conductivity of the joint at a temperature of 900 ° C is 0.01 S / cm to 1.5 S / cm. Thermal expansion coefficient of the joining portion is ^{9 × 10 -6 / K~14 × 10} -6 / K, the oxygen ion-conducting device according to any one of claims 1-3. A conductive bonding material for bonding an oxygen ion conductive ceramic material constituting an oxygen ion conductive module and at least one ceramic connecting member, the following two components:
(A). The following composition in mass ratio in terms of oxide:
SiO ₂ 60 to 75 wt%;
Al ₂ O ₃ 10-20% by mass;
Na ₂ O 3-10% by mass;
K ₂ O 5-15% by mass;
MgO 0 to 3% by mass;
CaO 0 to 3% by mass;
A glass substantially composed of: cristobalite crystals and / or leucite crystals precipitated in a matrix of the glass; and (b). A conductive substance that can function a junction between the oxygen ion conductive ceramic material and the ceramic connecting member as an electron conduction path is selected from the group consisting of Cu, Co, Fe, Ni, Cr, Ir, Sn, and Nb. conductive metal oxides containing at least one metal element is formed by a mixture is,
The content rate of the said electroconductive substance is an electroconductive joining material which is 10 mass%-90 mass% by the oxide conversion of the said metal element by making the total amount of an electroconductive joining material into 100 mass% . The conductive bonding material according to claim 5 , wherein the conductive substance is a conductive metal oxide containing Cu or Co as a metal element. A method of joining an oxygen ion conductive ceramic material constituting an oxygen ion conductive module and at least one ceramic connecting member,
Preparing the conductive bonding material according to claim 5 or 6 , and applying the bonding material to a connection portion between the oxygen ion conductive ceramic material and the connection member;
By firing the applied conductive bonding material in a temperature range of 1000 ° C. or higher, the gas flow composed of the conductive bonding material is blocked at the connection portion between the oxygen ion conductive ceramic material and the connection member. Forming a joining part,
Including the method. The oxygen ion conduction module according to any one of claims 1 to 4 ,
The oxygen ion conductive ceramic material is a zirconia solid electrolyte,
The ceramic connecting member is an interconnector made of a perovskite oxide,
An oxygen ion conduction module functioning as a solid oxide fuel cell, wherein the conductive bonding material for bonding the oxygen ion conductive ceramic material and the connection member acts as the interconnector.

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