JP2003107043A - Oxygen pump and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that each of respective materials used is limited to a specific material because their coefficients of thermal expansion must be within mutually close ranges. SOLUTION: Since a metal foil is bonded to an oxygen ion-conductive substrate 2 via a conductive seal material 7 such as a sealing metal-paste burnt substance of the like, the damage of an oxygen pump element such as the exfoliation, the crack or the like of a seal part is not generated due to a thermal stress generated due to the difference in a coefficient of thermal expansion between the materials.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an oxygen pump.

[0002]

2. Description of the Related Art Conventionally, this kind of oxygen pump is as follows.

In Japanese Patent Application Laid-Open No. 2000-86204, FIG.
Are disclosed. Oxygen pump element 1
Is formed by forming a cathode electrode film 3 on one surface of an oxygen ion conductive substrate 2 and an anode electrode film 4 on the other surface. Insulating support material 5 at the end of oxygen ion conductive substrate 2
Are arranged, and the oxygen ion conductive substrate 2 and the connecting member 6 are hermetically sealed. At this time, the insulating support material 5 should have substantially the same thermal expansion coefficient as the thermal expansion coefficient of the oxygen ion conductive substrate 2 or the thermal expansion coefficient of the connecting member 6, and have substantially the same thermal expansion coefficient. Is these three
Means that the thermal expansion coefficient of the types of materials to match (20 to 5) within the x10 over ⁷ / ° C..

[0004] Further, the insulating support material 5 having a small Young's modulus is used.
Is allowed to have a larger coefficient of thermal expansion than the coefficient of thermal expansion of the oxygen ion conductive substrate 2 or the coefficient of thermal expansion of the connecting member 6, and conversely, the insulating support member 5 having a large Young's modulus It is required to have a coefficient of thermal expansion closer to the coefficient of thermal expansion of the ion-conductive substrate 2 or the coefficient of thermal expansion of the connecting member 6 ".

Further, as typical oxygen ion conductive materials, yttrium-doped zirconia (YSZ) and gadolinia-doped ceria (GDC) are disclosed. Further, a lithium aluminosilicate glass-based material is disclosed as the insulating support material 5 and lanthanum strontium chromite is disclosed as the connecting material 6.

[0006]

However, in the above-described conventional oxygen pump, the thermal expansion coefficients of the insulating support member 5, the oxygen ion conductive substrate 2 and the connecting member 6 are within a range close to each other. Therefore, there is a problem that each material is limited to a specific material. Further, since the connecting member 6 is a metal oxide-based material, in order to finish it in various shapes, a mold corresponding to the shape is required. Therefore, there has been a problem that the adaptability to the shape change is lacking and the manufacturing process is complicated.

[0007]

According to the present invention, there is provided an oxygen ion conductive substrate comprising a cathode electrode film formed on one surface of an oxygen ion conductive substrate and an anode electrode film formed on the other surface. A pump element and a metal foil having an opening, wherein the opening is disposed to face either the cathode electrode film or the anode electrode film, and the metal foil around the opening and the oxygen ion conductive film are formed. This is an oxygen pump in which a conductive sealing material is provided between substrates.

According to the above-mentioned invention, since the metal foil is used instead of the conventional connecting member, the degree of freedom in selecting the material is high. Further, since it is excellent in workability, it can respond to a shape change immediately, and the manufacturing process is simplified.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The oxygen pump according to the first aspect of the present invention has a configuration in which an oxygen ion conductive substrate is connected to a metal foil seal by a conductive seal material. Therefore, since a metal foil is used without using a special metal oxide material, the degree of freedom in selecting a material is high. Also, because it is excellent in workability,
The shape can be changed immediately, and the manufacturing process is simplified.

In the oxygen pump according to claim 2 of the present invention, one foil selected from nickel foil, iron-chromium alloy foil, titanium foil, gold foil and platinum foil is used as the metal foil. Since these metal foils have a smaller Young's modulus than the oxygen ion conductive substrate, the thermal stress of the metal foil portion generated due to the difference in thermal expansion coefficient between them is also small. Therefore, the sealing property between the oxygen ion conductive substrate and the metal foil is maintained even at a high temperature.

In the oxygen pump according to claim 3 of the present invention, the metal foil is an annealed foil. Therefore, since the processing strain in the metal foil is reduced, its Young's modulus can be reduced.

In the oxygen pump according to claim 4 of the present invention, the thickness of the metal foil is (5 to 50) μm. Therefore,
When strain occurs in a direction parallel to the surface of the metal foil, the stress generated by the metal foil can be reduced and practical physical strength can be ensured.

[0013] In the oxygen pump according to claim 5 of the present invention, the conductive sealing material is a fired body of a sealing metal paste. Therefore, a sintered body can be formed in a predetermined shape.

In the oxygen pump according to claim 6 of the present invention, the metal paste for sealing is one paste selected from nickel paste, gold paste, silver-palladium paste and platinum paste. Stable in high-temperature oxidizing atmosphere.

In the oxygen pump according to claim 7 of the present invention, the main component of the metal foil and the sealing metal paste is the same metal. Therefore, the adhesion between them is excellent.

In the oxygen pump according to the present invention, the cathode electrode film or the anode electrode film facing the metal foil is connected to the conductive sealing material. Therefore, a metal foil can be used as a lead wire.

In the oxygen pump according to the ninth aspect of the present invention, the external lead wire is connected to the metal foil. Therefore,
External lead wires can be easily connected.

In the oxygen pump according to the tenth aspect of the present invention, the external lead wire is welded to the metal foil. Therefore,
External lead wires can be easily connected.

In the oxygen pump according to the present invention, the external lead wire and the metal foil are made of the same material. Therefore,
A highly reliable connection is obtained.

In the oxygen pump according to the twelfth aspect of the present invention, the material of the external lead wire and the metal foil is nickel. Therefore, a highly reliable connection can be obtained at a low cost.

According to a thirteenth aspect of the present invention, there is provided an oxygen pump comprising: a cathode electrode film formed on one surface of an oxygen ion conductive substrate and an anode electrode film formed on the other surface facing the cathode electrode film; It is manufactured by firing the sealing metal paste at a firing temperature lower than the electrode film forming temperature. Therefore, the sealing metal paste can be fired without deteriorating the cathode electrode film or the anode electrode film.

In the oxygen pump according to claim 14 of the present invention, the firing temperature of the sealing metal paste is (700 to 80).
0) ° C. Therefore. A stable oxygen pump can be obtained at an operating temperature of 600 ° C. or less.

[0023]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 is a sketch drawing showing the configuration of an oxygen pump 1 according to Embodiment 1 of the present invention.

The cathode electrode film 3 is formed on one surface of the oxygen ion conductive substrate 2 and the anode electrode film 4 is formed on the other surface.
Is formed to form the oxygen pump element 1. As the oxygen ion conductive substrate 2, yttrium-doped zirconia (YSZ) or samarium-doped ceria (SD
C) is used. Further, as the cathode electrode film 3 and the anode electrode film 4, a baked film such as platinum (Pt), silver (Ag), and a composite metal oxide (SSCO) composed of samarium strontium-cobalt, or a deposited film is used.

The oxygen pump of the present invention comprises an oxygen pump element 1
Is manufactured by bonding a metal foil 8 to the oxygen ion conductive substrate 2 via the conductive sealing material 7. At this time, the opening 81 provided in the metal foil 8 is arranged so as to face the cathode electrode film 3 or the anode electrode film 4. Further, the conductive sealing material 7 is arranged so as to be located in the peripheral portion of the opening 81 of the metal foil 8.

When a DC voltage is applied between the cathode and the anode by setting the cathode electrode film 3 to a negative potential and the anode electrode film 4 to a positive potential, oxygen molecules in the cathode-side external space are converted from the cathode electrode film 3 to oxygen ions as oxygen ions. It is taken in the ion conductive substrate 2 and reaches the anode electrode film 4. The oxygen ions that reach the anode electrode film 4 become oxygen molecules and dissipate in the external space on the anode side. By separating the cathode-side external space and the anode-side external space by the metal foil 8, oxygen can be transported from the cathode-side external space to the anode-side external space.

The oxygen pump element is (500-800) ° C.
Works with Since the thermal expansion coefficients of the oxygen ion conductive substrate 2, the conductive sealing material 7, the metal foil 8, and the like are different from each other, a thermal stress is generated in the sealing portion during operation. In the present invention, since a fired body of the sealing metal paste described later is used as the conductive sealing material 7, the thermal stress caused by the conductive sealing material 7 itself is small. This is because the fired body is porous, so that thermal expansion is absorbed in the voids, and the Young's modulus of the metal is small. A small Young's modulus of the metal means that the thermal stress caused by the metal foil 8 is also small. As the conductive sealing material 7, in addition to the fired body of the sealing metal paste, a fired body of the composite oxide-based paste can be used. However, the firing temperature of the composite oxide-based paste requires a high temperature of 1000 ° C. or higher. When the metal foil 8 is bonded via the conductive sealing material 7 after the preparation of the oxygen pump element 1, if the Pt fired film is used as the cathode electrode film, the electrode film is easily deteriorated.

As the conductive sealing material 7, a fired body of a sealing metal paste is desirable. Nickel paste, gold paste, silver-palladium paste, platinum paste, or the like is used as the metal paste for sealing. The fired bodies of these pastes are excellent in that they are stable in a high-temperature oxidizing atmosphere. In addition, since these pastes are widely used industrially, they can be easily obtained, and firing conditions have been established. Therefore, a stable fired body can be obtained. Thermal expansion coefficients of these sintered bodies, it [(90 to 140) x10 over ⁷ / ° C.] and equal to or at least a single metal, or is believed to be smaller than that. On the other hand,
The thermal expansion coefficient of the oxygen ion conductive substrate 2 is (100 to 1).
20) x10 is in the range of over ⁷ / ° C., not necessarily a thermal expansion coefficient close to that of the metal sintered body. However, since the Young's modulus of these fired bodies is at least one order of magnitude smaller than that of the oxygen ion conductive substrate 2, even if a thermal stress is generated in these fired bodies due to a difference in thermal expansion coefficient between the two, the stress is reduced by oxygen ion It is not large enough to cause cracks in the conductive substrate 2. Furthermore, since these fired bodies show elasticity compared to the brittle oxygen ion conductive substrate 2, they are also excellent in that they can withstand large strains.

The metal foil 8 is preferably one foil selected from nickel foil, iron-chromium alloy foil, titanium foil, gold foil and platinum foil. The metal foil 8 is essentially desirable in that it has a smaller Young's modulus than the oxygen-ion conductive substrate 2. However, in the present invention, the metal foil 8 has a foil-like shape, and thus is caused by thermal distortion. Stress can be reduced. It is more preferable that the coefficient of thermal expansion of the metal foil 8 be as close as possible to that of the oxygen ion conductive substrate 2. Iron Kuromu alloy foil, titanium foil and platinum foil in addition to that it is small Young's modulus, the thermal expansion coefficient (85 to 120) x10 ^-7
/ ° C., which is superior to that of the oxygen ion conductive substrate 2.

The metal foil 8 may be manufactured by rolling a thick metal plate. In this case, processing strain remains in the metal foil 8 and is hardened. This is substantially the same as increasing the Young's modulus. Since the residual processing strain can be removed by annealing, it is preferable to use an annealed metal foil 8. The thickness of the metal foil is (5-50) μ
m is desirable. When the thickness is 5 μm or less, the physical strength becomes too small and is not practical. Also, 50μ
If the thickness is more than m, the thermal stress increases, and the conductive sealing material is easily peeled off at 7 parts.

It is desirable that the metal foil 8 and the main component of the sealing metal paste be the same metal. When bonding the metal foil 8 to the oxygen ion conductive substrate 2, after printing and drying a metal paste for sealing in a predetermined shape on the metal foil 8, the oxygen ion conductive substrate 2 is laminated thereon and fired in the air. Thus, the metal foil 8 can be bonded to the oxygen ion conductive substrate 2 via the fired body 7 of the metal paste. At this time, since the main components of the metal foil 8 and the sintered body 7 of the metal paste are the same, the adhesion between them is excellent.

It is preferable that the conductive sealing material 7 is electrically connected to the cathode electrode film 3 or the anode electrode film 4 facing the metal foil 8. Since the metal foil 9 is electrically connected to one of the electrode films, the metal foil 8 can also function as a lead wire. However, enlarging the shape of the metal foil 8 is not preferable because it lowers the manufacturing efficiency. Therefore, the function of the metal foil 8 as a lead wire is limited in terms of the length of the wiring. In such a case, the metal foil 8
It is preferable that an external lead wire is connected to the external power supply. Since the length of the external lead wire can be arbitrarily adjusted, the length of the wiring is not limited. As a method of connecting the external lead wire to the metal foil 8, there are a brazing method, a welding method, a physical caulking method, and the like. The welding method is excellent in workability and reliability. At the time of welding, it is most preferable that the external lead wire and the metal foil 8 are made of the same material. In particular, when the material of the external lead wire and the metal foil 8 is nickel, which is inexpensive, the nickel foil having a thickness of (10 to 20) μm and the nickel wire having a diameter of about 0.1φ are used industrially. It is low-priced.

The metal foil 9 is interposed via the conductive sealing material 7.
Is bonded to the oxygen ion conductive substrate 2, a conductive sealing material 7 is formed on the cathode electrode film 3 or the anode electrode film 4.
May be formed.

In the case of manufacturing the oxygen pump of the present invention, it is preferable to form the oxygen pump element 1 and then bond the metal foil 8 to the oxygen ion conductive substrate 2 via the conductive sealing material 7. At this time, it is desirable to form the conductive sealing material 7 by firing the sealing metal paste at a firing temperature lower than the temperature at which the cathode electrode film 3 and the anode electrode film 4 are formed. In the operation of the oxygen pump, the performance of the oxygen pump element is the most important. When the oxygen ion conductive substrate 2 of a certain material is used, the performance of the oxygen
And the anode electrode film 4. Usually, a porous fired Pt is used as the cathode electrode film 3 and the anode electrode film 4.
Although an electrode film is often used, the firing temperature is (800 to
1000) ° C. In order to form the conductive sealing material 7 without lowering the porosity of the fired Pt electrode film, it is preferable to fire the sealing metal paste at (700 to 800) ° C. The firing temperature of the sealing metal paste can be adjusted to (700 to 800) ° C. by appropriately selecting the melting point of the glass component added in a small amount in the paste. When the firing temperature of the sealing metal paste is higher than those of the cathode electrode film 3 and the anode electrode film 4,
Porosity tends to decrease due to thermal aggregation.

[0036]

In the present invention, as described above, according to the present invention, the oxygen-ion conductive substrate, even if the thermal expansion coefficient between the sintered body and a metal foil material of the sealing metal paste (10 to 40) x10 ^-7 different, There is no breakage of the oxygen pump element such as peeling or cracking of the seal portion.

Further, according to the present invention, the conductive sealing material is stable in a high-temperature oxidizing atmosphere, and the stress generated in the conductive sealing material due to thermal strain can be reduced.

In the present invention, a metal foil can be used as an external lead.

Further, according to the present invention, a conductive sealing material can be formed without reducing the porosity of the electrode film.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of an oxygen pump according to a first embodiment of the present invention.

FIG. 2 is a sectional view of a conventional oxygen pump.

[Explanation of symbols]

1 Oxygen pump element 2 Oxygen ion conductive substrate 3 Cathode electrode film 4 Anode electrode film 7 Conductive sealing material 8 Metal foil 81 Opening provided in metal foil 8

   ────────────────────────────────────────────────── ─── Continuation of front page    (72) Inventor Naoko Ikukawa             Matsushita Electric, 1006 Kadoma, Kazuma, Osaka             Sangyo Co., Ltd.

Claims (14)

[Claims] An oxygen pump element having a cathode electrode film formed on one surface of an oxygen ion conductive substrate and an anode electrode film formed on the other surface thereof, and a metal foil having an opening; An opening was disposed facing either one of the cathode electrode film and the anode electrode film, and a conductive sealing material was disposed between the metal foil and the oxygen ion conductive substrate around the opening. Oxygen pump. 2. The oxygen pump according to claim 1, wherein the metal foil is one foil selected from a nickel foil, an iron-chromium alloy foil, a titanium foil, a gold foil and a platinum foil. 3. The oxygen pump according to claim 2, wherein the metal foil is an annealed foil. 4. The oxygen pump according to claim 2, wherein the thickness of the metal foil is (5 to 50) μm. 5. The oxygen pump according to claim 1, wherein the conductive sealing material is a sintered body of a sealing metal paste. 6. The sealing metal paste is one paste selected from a nickel paste, a gold paste, a silver-palladium paste, and a platinum paste.
An oxygen pump as described. 7. The oxygen pump according to claim 5, wherein the main component of the metal foil and the metal paste for sealing is the same metal. 8. The oxygen pump according to claim 1, wherein the cathode electrode film or the anode electrode film facing the metal foil and the conductive sealing material are electrically connected. 9. The oxygen pump according to claim 8, wherein the external lead wire is connected to the metal foil. 10. The oxygen pump according to claim 9, wherein the external lead wire is welded to the metal foil. 11. The oxygen pump according to claim 10, wherein the external lead wire and the metal foil are made of the same material. 12. The oxygen pump according to claim 11, wherein the material of the external lead wire and the metal foil is nickel. 13. A firing temperature lower than the formation temperature of the cathode electrode film and the anode electrode film after forming the cathode electrode film on one surface of the oxygen ion conductive substrate and the anode electrode film on the other surface. A method of manufacturing an oxygen pump for firing a metal paste for sealing by using the above method. 14. The method for manufacturing an oxygen pump according to claim 13, wherein the firing temperature of the sealing metal paste is (700 to 800) ° C.