JPH0816668B2 - Manufacturing method of oxygen sensor - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an oxygen sensor capable of improving the bonding strength between a solid electrolyte and an electrode.

[0002]

2. Description of the Related Art Conventionally, as an example of a thin film gas sensor,
A thin film oxygen sensor using stabilized zirconia as a solid electrolyte having oxygen ion conductivity is known. The oxygen sensor is, for example, yttria-added stabilized zirconia (ZrO 2
_2-8mol% Y ₂ O ₃₎ as, zirconia (ZrO ₂₎
A few mol of an oxide such as yttria (Y ₂ O ₃ ), magnesia (MgO), or calcia (CaO), which is a stabilizer,
% To stabilize it as a solid electrolyte, which is usually formed on a porous alumina (Al ₂ O ₃ ) substrate by using a magnetron sputtering device or the like and porous platinum (Pt electrode layer, ZrO ₂ A solid electrolyte layer of 8 mol% and the like and a porous Pt electrode layer are sequentially laminated to be prepared.

In the oxygen sensor, when the solid electrolyte layer is kept at a constant temperature and a predetermined voltage is applied between both Pt electrode layers, it is taken into the solid electrolyte layer through the porous alumina substrate. Oxygen in the sample gas flows as ions in the solid electrolyte layer by the oxygen pumping action, and from the current value using the oxygen ions as carriers,
The configuration is such that the oxygen concentration in the sample gas is measured.

Since this oxygen sensor has excellent characteristics such as faster response speed, lower power consumption, and smaller size as compared with the conventional bulk type oxygen sensor, it prevents an oxygen deficiency accident in a closed room such as a basement. It is a sensor that is suitable for various purposes such as measuring oxygen concentration in molten steel, managing combustion in engines and boilers, and measuring pollution.

[0005]

By the way, when manufacturing the above-mentioned oxygen sensor, since the Pt electrode layer, the solid electrolyte layer, and the Pt electrode layer are simply sequentially laminated,
There is a drawback that the bonding strength between the Pt electrode layer and the solid electrolyte layer is very weak. When the bonding strength between the Pt electrode layer and the solid electrolyte layer is weak, the electric resistance at the interface between the Pt electrode layer and the solid electrolyte layer becomes very large, and the voltage applied to the solid electrolyte layer falls below a predetermined voltage. Will be lost. Therefore, the oxygen pumping action is not favorably performed in the solid electrolyte layer, and the sensitivity and responsiveness of the oxygen sensor are greatly reduced, which is the main factor of reduced reliability. The above phenomenon is particularly remarkable in the presence of a thermal cycle.

Therefore, as a method of improving the bonding strength, a method of roughening the surface to be sputtered to form irregularities to increase the contact area has been studied, but it is not sufficient to simply increase the contact area. The bonding strength between the Pt electrode layer and the solid electrolyte layer cannot be significantly increased, and it is not a fundamental solution.

Further, a method of reacting a laminate composed of a Pt electrode layer and a solid electrolyte layer at a high temperature of, for example, 1400 ° C. or higher to form a bonding layer at the interface between the Pt electrode layer and the solid electrolyte layer has been considered. . However, in this method, since the reaction temperature is very high, there is a risk that the Pt electrode layer and the solid electrolyte layer may be deteriorated, and the material used is limited from the viewpoint of heat resistance, so it is optimal. There are various drawbacks in that it becomes extremely difficult to select the material and the manufacturing cost is significantly increased.

The present invention has been made in view of the above circumstances and is capable of improving the bonding strength between an electrode and a solid electrolyte, and has high reliability, downsizing, low power consumption, and responsiveness. Acid with excellent characteristics such as
It is to provide an elementary sensor .

[0009]

In order to solve the above problems, the present invention adopts the following oxygen sensor manufacturing method. That is, in the method for producing an oxygen sensor according to claim 1, 0.05 to 5.0% by weight of trivalent or less metal is added.
The solid electrolyte layer is oxidized by firing and becomes a solid electrolyte layer.
0.05 to 5.0 for the elementary solid electrolyte layer and trivalent or lower metal
The electrode layer is added by weight% and is oxidized by firing.
And the element electrode layer that becomes
Form, characterized by the this <br/> for firing the laminate in an oxidizing atmosphere.

[0010] In the method of manufacturing the oxygen sensor of claim 2, in the manufacturing method of the oxygen sensor according to claim 1,
The metal is characterized by containing at least one selected from Cu, Bi, Zn and Cd.

Here, when the amount of the metal added to the solid electrolyte layer is less than the lower limit value, the effect of addition as a metal oxide is not observed, and when it exceeds the upper limit value, these metal oxides are oxidized. It is unsuitable because the substance becomes a lattice defect in the solid electrolyte, impairs ionic conductivity, and reduces the sensitivity of the sensor. Therefore, the amount of metal added is preferably within the above range.

When the amount of the metal added to the elementary electrode layer is less than the lower limit value, the effect of addition as a metal oxide is not observed, and when it exceeds the upper limit value, these metal oxides are not added. Since it is a high resistance material, the resistance value of the electrode layer becomes large and it is not suitable as an electrode. Therefore, the amount of metal added is preferably within the above range.

It is desirable that the metal contains at least one of Cu, Bi, Zn and Cd, which is a metal that is well compatible with both the solid electrolyte and the electrode and does not adversely affect these characteristics.

[0014]

In the method of manufacturing an oxygen sensor according to claim 1 of the present invention, the metal added to the solid electrolyte layer is in an oxidizing atmosphere.
Metallic acid that is oxidized by firing in an atmosphere
To a solid electrolyte layer containing a compound. Also, the element electrode
The metal added to the layers should be calcined in an oxidizing atmosphere.
Electrode layer containing metal oxide that is oxidized by
Changes to. And these metal oxides are solid electrolytes
Since it exists in both the layer and the electrode layer, the metal
The bond strength at the interface between these two layers is greatly improved through the oxide.
Go up.

Further, in the oxygen sensor manufacturing method according to claim 2, the metal is burned to form copper oxide (Cu).
O), cuprous oxide (Cu ₂ O), bismuth oxide (Bi ₂ O ₃
Or BiO (= Bi ₂ O ₃ + Bi)), zinc oxide (Zn
O), cadmium oxide (CdO or CdO _x (however, x
<1.0)) and other metal oxides, which intervene in the solid electrolyte and the electrode and significantly improve the bonding strength between the solid electrolyte and the electrode.

Here, the elemental solid electrolyte layer is oxidized by firing to become a solid electrolyte layer. For example, the solid electrolyte layer is yttria-added stabilized zirconia (ZrO ₂ -8 mol% Y ₂ O ₃ ). In the case of, the solid electrolyte layer is a mixture of zirconium (Zr) -16 mol% yttrium (Y) containing 0.05 to 5.0% by weight of a metal having a valence of 3 or less such as Cu, Bi, Zn and Cd. It is composed of This elemental solid electrolyte layer is fired in an oxidizing atmosphere to give, for example, Zr-16 mol.
% Y is oxidized to ZrO ₂ -8 mol% Y ₂ O ₃ , and
The added Cu is oxidized to CuO or Cu ₂ O, B
i is Bi ₂ O ₃ or BiO (= Bi ₂ O ₃ + Bi), and Z
n is ZnO, Cd is CdO or CdO _x (where x <
1.0), and these metal oxides are Zr
O uniformly dispersed in _2-8 mol% Y in ₂ O _3.

The elemental electrode layer is oxidized by firing to become an electrode layer. For example, Cu, Bi, Z
It is composed of a porous Pt electrode layer containing 0.05 to 5.0% by weight of a metal having a valence of 3 or less such as n and Cd. By firing this element electrode layer in an oxidizing atmosphere,
For example, the added Cu is oxidized to CuO or Cu.
₂ O, Bi is Bi ₂ O ₃ or BiO (= Bi ₂ O ₃ + B
In i), Zn is ZnO, Cd is CdO or CdO _x.
(However, x <1.0), and these metal oxides are uniformly dispersed in the Pt electrode layer.

[0018]

Embodiments of the present invention will be described below. (Example 1) As shown in FIG. 1, using a magnetron sputtering device, a porous elemental Pt electrode layer 2, Cu and Cu containing 1% by weight each of Cu and Bi was formed on a porous alumina substrate 1. Zr-1 containing 1 wt% of Bi each
6 mol% Y element solid electrolyte layer 3, Cu and Bi
The porous elemental Pt electrode layers 4 containing 1 wt% of each of the above were sequentially laminated. Next, the laminated body 5 N ₂ over 21 to 10
A thin film oxygen sensor (thin film gas sensor) 6 was obtained by baking at 1200 ° C. for 3 hours in an oxidizing atmosphere of 0% O ₂ .

FIG. 2 is a diagram showing the limiting current characteristics of the oxygen sensor 6. Here, the magnitude of the current obtained when the oxygen sensor 6 was heated to 300 ° C. and the magnitude of the voltage applied between the Pt electrode layers 2 and 4 was changed was plotted.
From FIG. 2, it is clear that the oxygen sensor 6 exhibits a good limiting current characteristic.

(Example 2) Using a magnetron sputtering apparatus, a porous elemental Pt electrode layer 12 containing 2 wt% of Cu and a Zr-16 mol% containing 2 wt% of Cu on a porous alumina substrate 1. Elementary solid electrolyte layer 13 made of Y, C
A porous elemental Pt electrode layer 14 containing 2 parts by weight of u was sequentially laminated. Next, this laminated body 15 was calcined for 3 hours at 1200 ° C. in an oxidizing atmosphere consisting N ₂ over 21-100% O _2, and an oxygen sensor (thin-film gas sensor) 16 of the thin film type. It was clear that this oxygen sensor 16 also exhibits a good limiting current characteristic like the oxygen sensor 6.

(Example 3) Using a magnetron sputtering apparatus, a porous elemental Pt electrode layer 22 containing 2% by weight of Bi and a Zr-16 mol% containing 2% by weight of Bi on a porous alumina substrate 1. Elementary solid electrolyte layer 23 made of Y, B
Porous elemental Pt electrode layers 24 containing 2% by weight of i were sequentially laminated. Next, the laminated body 25 N ₂ over twenty-one to one hundred% O ₂
Was fired at 1200 ° C. for 3 hours in an oxidizing atmosphere consisting of to obtain a thin film oxygen sensor (thin film gas sensor) 26. It was apparent that this oxygen sensor 26 also exhibits a good limiting current characteristic, like the oxygen sensors 6 and 16.

Table 1 compares the bonding strengths of the oxygen sensors of Examples 1 to 3 and the oxygen sensor of the conventional example. Here, in the oxygen sensors of Examples 1 to 3,
The bonding strength was evaluated by cutting the laminate on the substrate into a grid pattern to prepare 10 test pieces each having a size of 2 × 2 mm, and attaching tapes to the Pt electrode layers of these test pieces, and then again The tape was peeled off, and the number of test pieces in which 90% or more of the Pt electrode layer remained was determined. On the other hand, conventional oxygen
The sensor is zirconia of the material described in "Prior Art".
Platinum is formed on both sides of the ion conductor 20 to be porous.
Laminated anode electrode 21 and cathode electrode 22
In addition, the cathode electrode 2 of the zirconia ion conductor 20
There is a gas diffusion hole 24A on the second side through the sealing glass 23.
The cap 24 that is attached to the
Data 25 is laminated (see FIG. 3).
The bonding strength of conventional oxygen sensors was evaluated using the above-mentioned example.
Like the oxygen sensors 1 and 2, the zirconia ion conductor
Anode electrode 21 located on the lower side of 20
Cut into 10 pieces of 2 x 2 mm size,
After applying the tape to the Pt electrode layer of these test pieces,
The tape was peeled off again, and 90% or more of the Pt electrode layer remained.
It was carried out by determining the number of test pieces that are present.

[0023]

[Table 1]

From Table 1, it is clear that the oxygen sensors of Examples 1 to 3 have a greatly improved bonding strength between the Pt electrode layer and the solid electrolyte layer as compared with the oxygen sensors of the conventional examples.

As described above, according to the method of manufacturing the oxygen sensor 6 (16, 26) of the above embodiment, Cu and Bi are contained.
Alternatively, one of Cu and Bi is 0.05 to
Elementary Pt electrode layer 2 (12, 22) containing 5.0% by weight
And one of Cu and Bi or Cu and Bi
Zr-16 mol containing 0.05 to 5.0% by weight of seeds
% Solid Y electrolyte layer 3 (13, 23), and Cu
And Bi or Cu and Bi to 0.
Elementary Pt electrode layer 4 (14,2) containing 05 to 5.0 wt%
4) is laminated, and the obtained laminated body 5 (15, 25) is fired in an oxidizing atmosphere to obtain a solid electrolyte layer 3 (13,
23) as the solid electrolyte layer and the elemental Pt electrode layer 2 (12, 2).
2) and the elemental Pt electrode layer 4 (14, 24) are changed to Pt electrode layers, and the solid electrolyte layer and the electrode layer are bonded to each other. Therefore, metal oxides such as CuO and Bi ₂ O ₃ are added. By interposing it in both the solid electrolyte layer and the electrode layer, the bonding strength at the interface between these layers can be greatly improved. Therefore, the reliability of the thin-film oxygen sensor such as sensitivity and responsiveness, electrical characteristics such as long-term life characteristics, and the like can be significantly improved.

As described above, it is possible to provide a thin film type oxygen sensor having excellent characteristics such as high reliability, downsizing, low power consumption, improved responsiveness, and low cost.

[0027]

As described in detail above, claim 1
The method for manufacturing an oxygen sensor of
0.05 to 5.0 wt% is addedElementary solid electrolyte layer
And 0.05 to 5.0% by weight of trivalent or less metal is added
BecomeElementary electrode layerAnd are laminated, and the resulting laminate is placed in an oxidizing atmosphere.
Since it was decided to fire in air, the solid electrolyte and
The joint strength at the interface with the pole can be significantly improved.
It Therefore, the oxygen sensor's sensitivity, responsiveness, etc.
Greatly improve reliability such as characteristics and long-term life characteristics
Can be.

[0028] In the method of manufacturing the oxygen sensor of claim 2, in the manufacturing method of the oxygen sensor according to claim 1,
Since the metal contains at least one selected from Cu, Bi, Zn, and Cd, the bonding strength at the interface between the solid electrolyte and the electrode is not impaired without impairing the characteristics of the solid electrolyte and the electrode. Can be significantly improved. Thus, the sensitivity of the oxygen sensor, the electrical characteristics such as responsiveness, can greatly improve the reliability of such long-life characteristics may.

As described above, an acid having excellent characteristics such as high reliability, downsizing, low power consumption, improved responsiveness, and low cost.
It becomes possible to provide an elementary sensor .

[Brief description of drawings]

FIG. 1 is a front sectional view showing an oxygen sensor which is an embodiment of the oxygen sensor of the present invention.

FIG. 2 is a diagram showing a limiting current characteristic of an oxygen sensor which is an embodiment of the oxygen sensor of the present invention.

FIG. 3 is a diagram showing a conventional oxygen sensor compared with the oxygen sensors of Examples 1 to 3 in the experimental example of Table 1.

[Explanation of symbols]

6, 16, 26 ... Oxygen sensor, 1 ... Substrate, 2, 4, 1
2, 14, 22, 24 ... (Elementary) Pt electrode layer , 3, 13,
23 ... (Elementary) solid electrolyte layer

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Issei Ishibashi 1-5-1, Kiba, Koto-ku, Tokyo Within Fujikura Electric Wire Co., Ltd. (72) Inventor Yoshinori Kato 1-5-1, Kiba, Koto-ku, Tokyo Fujikura Electric Wire Co., Ltd. (56) Reference JP-A-2-167461 (JP, A)

Claims (2)

[Claims] 1. A solid electrolyte, in which electrodes are laminated on both surfaces, is provided on a porous substrate, and the oxygen concentration in a sample gas, which is limitedly taken into the solid electrolyte through the porous substrate, is measured. A method for manufacturing an oxygen sensor, wherein an oxygen current is measured by an oxygen pumping action of a solid electrolyte, wherein 0.05 to 5.0% by weight of a metal having a valence of 3 or less is added,
Elementary solid that is oxidized to form a solid electrolyte layer
The electrolyte layer and trivalent or lower metal are added in an amount of 0.05 to 5.0% by weight and baked.
An elemental electrode layer which is oxidized by forming the electrode layer and
A method for manufacturing an oxygen sensor, characterized in that a laminated body is formed by laminating the laminated bodies, and the laminated body is fired in an oxidizing atmosphere. 2. The metal is copper (Cu) or bismuth (B).
2. At least one selected from i), zinc (Zn), and cadmium (Cd) is contained.
A method for manufacturing the oxygen sensor described above.