JPH0816667B2 - 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,
An oxygen sensor using stabilized zirconia as an oxygen ion conductive solid electrolyte is known. This oxygen sensor is
For example yttria-stabilized zirconia (ZrO ₂ over 8
Stabilized by adding a few mol% of oxides such as yttria (Y ₂ O ₃ ), magnesia (MgO) and calcia (CaO) to zirconia (ZrO ₂ ), such as mol% Y ₂ O ₃ ). Which is used as a solid electrolyte,
A porous platinum (Pt) electrode layer is formed on a porous alumina (Al ₂ O ₃ ) substrate using a magnetron sputtering device or the like.
It is prepared by sequentially stacking a solid electrolyte layer of ZrO ₂ -8 mol% Y ₂ O _{3 and the} like and a porous Pt electrode layer.

In this 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 the oxygen concentration in the sample gas is measured from the current value using the oxygen ions as carriers.

Compared with the conventional bulk type oxygen sensor, this oxygen sensor has excellent characteristics such as quick response speed, low power consumption, and miniaturization, so that an oxygen deficiency accident in a closed room such as a basement. This sensor is suitable for various purposes such as prevention, measurement of oxygen concentration in molten steel, combustion control of engines and boilers, and pollution measurement.

[0005]

By the way, when the above oxygen sensor is manufactured, the Pt electrode layer, the solid electrolyte layer, and the Pt electrode layer are simply laminated in this order, so that P
There is a drawback that the bonding strength between the t 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. The above-mentioned phenomenon is remarkable especially in the presence of thermal cycles.

Therefore, as a method of improving the bonding strength, a method of forming unevenness on the surface to be sputtered to increase the contact area has been studied. However, simply increasing the contact area causes the solid state of the Pt electrode layer and the solid state. The bonding strength with the electrolyte layer cannot be significantly increased, which 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 a method for manufacturing an elementary sensor .

[0009]

[Means for Solving the Problems] To solve the above problems
The invention is as follows.Oxygen sensor manufacturing methodAdopted
Was. That is, according to claim 1.Oxygen sensor manufacturing method
Is a trivalent or lower metal or its oxide 0.05 to 1
Solid electrolyte layer containing 0.0% by weight and trivalent or lower metal
Or containing 0.05 to 10.0% by weight of its oxide
Laminate the electrode layers and place the resulting laminate in an oxidizing atmosphere.
And sinter to bond the solid electrolyte layer and the electrode layer.
It is characterized by that.

Further, in claim 2Oxygen sensor manufacturing method
Is according to claim 1.Oxygen sensorIn the manufacturing method of
The metal is a small amount selected from Cu, Bi, Zn and Cd.
It is characterized by containing at least one kind.

Here, when the addition amount of the metal or its oxide added to the solid electrolyte is below the lower limit value, the effect of addition as a metal oxide is not observed, and when the addition amount exceeds the upper limit value, these additions are not observed. The metal oxide is not suitable because it becomes a lattice defect in the solid electrolyte, impairs ionic conductivity, and reduces the sensitivity of the sensor. Therefore, the addition amount of the metal or its oxide is preferably within the above range.

Further, when the amount of the metal or its oxide added to the electrode is below the lower limit, the effect of addition as a metal oxide is not observed, and when the amount exceeds the upper limit, these metal oxides are oxidized. Since the material is a high resistance material, the resistance value of the electrode layer becomes large and it is not suitable as an electrode. Therefore, the addition amount of the metal or its oxide 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 affect the characteristics as a sensor. . Further, the metal oxide is an oxide of Cu, Bi, Zn, Cd described above, that is, copper oxide (CuO), cuprous oxide (Cu _2).
O), bismuth oxide (Bi ₂ O ₃ ), bismuth oxide (Bi
O (= Bi ₂ O ₃ + Bi)), zinc oxide (ZnO), cadmium oxide (CdO), nonstoichiometric cadmium oxide (CdO)
_x, where x <1.0) and combinations thereof, such as C
A eutectic of uO and Cu ₂ O and the like are also included.

The oxygen sensor according to claim 1 of the present invention is manufactured.
In the manufacturing method , the metal added to the solid electrolyte and the metal added to the electrode are oxidized and converted into metal oxides by firing in an oxidizing atmosphere. By interposing these metal oxides in both the solid electrolyte layer and the electrode layer,
The bonding strength at the interface between these layers is significantly improved.

A method of manufacturing the oxygen sensor according to claim 2
In the method , the metal is burned to form CuO, Cu ₂
O, Bi ₂ O ₃ , BiO (= Bi ₂ O ₃ + Bi), Zn
O, CdO, CdO _x (provided that x <1.0) or the like is changed to a metal oxide, and is interposed in the solid electrolyte and the electrode,
The bonding strength between the solid electrolyte and the electrode is significantly improved without impairing the characteristics of the solid electrolyte and the electrode.

[0016]

Embodiments of the present invention will be described below. (Example 1) As shown in FIG. 1, using a magnetron sputtering apparatus, a porous Pt electrode layer 2 containing Cu and Bi in an amount of 2 wt% each, CuO and BiO were formed on a porous alumina substrate 1. Zr containing 2 wt% each
O ₂ over 8mol% Y ₂ O ₃ made of a solid electrolyte layer 3, Cu
, And porous Pt electrode layers 4 containing 2 wt% of Bi each were sequentially laminated. Next, the laminated body 5 N ₂ over 21
110 in an oxidizing atmosphere consisting of ~ 100% O _2.
The thin film was baked at 0 ° C. for 2 hours to obtain a thin film oxygen sensor (thin film gas sensor) 6. FIG. 2 is a diagram showing the limiting current characteristics of the oxygen sensor 6. Here, the oxygen sensor 6 is set to 300 ° C.
The magnitude of the electric current obtained when the magnitude of the voltage applied between the Pt electrode layers 2 and 4 was changed by heating to a graph was plotted. From FIG. 2, it is clear that the oxygen sensor 6 exhibits good limiting current characteristics.

(Example 2) Using a magnetron sputtering apparatus, a porous Pt electrode layer 12 containing CuO and Bi ₂ O _{3 in an amount} of 3% by weight, Cu and B on a substrate 1 respectively.
ZrO ₂ -8 mol% Y ₂ containing 1% by weight of each i
The solid electrolyte layer 13 made of O _3, the CuO and Bi ₂ O ₃ were sequentially stacked Pt electrode layer 14 of a porous, including one by each 3 percent by weight. Next, the laminated body 15 N ₂ over 21 to 1
1200 ° C in an oxidizing atmosphere consisting of 00% O ₂
The thin film oxygen sensor 16 was baked for 3 hours. It was clear that this oxygen sensor 16 also exhibits a good limiting current characteristic like the oxygen sensor 6.

Table 1 compares the bonding strengths of the oxygen sensors of Examples 1 and 2 and the conventional oxygen sensor. Here, the evaluation of the bonding strength in the oxygen sensors of Examples 1 and 2 was performed by cutting the laminate on the substrate into a grid pattern to prepare 10 test pieces each having a size of 2 × 2 mm. After the tape was attached to the Pt electrode layer of the test piece of No. 3, the tape was peeled off again, 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.

[0019]

[Table 1]

From Table 1, it is clear that the oxygen sensors of Examples 1 and 2 have a greatly improved bonding strength between the Pt electrode layer and the solid electrolyte layer as compared with the conventional oxygen sensors.

As described above, according to the method of manufacturing the oxygen sensor 6 (16) of the above embodiment, Cu and Bi or C are used.
P containing 0.05 to 10.0% by weight of uO and Bi ₂ O ₃
t electrode layer 2 (12) and Cu and Bi or CuO and Bi
And ₂ O ₃ solid electrolyte layer 3 containing 0.05 to 10.0 wt% (13), Pt electrode layer 4 of Cu and Bi, or CuO and Bi ₂ O ₃ containing 0.05 to 10.0 wt% (1
4) is laminated, and the obtained laminated body 5 (15) is fired in an oxidizing atmosphere to bond the solid electrolyte layer 3 (13) and the electrode layers 2, 4 (12, 14). Therefore, CuO and Bi ₂ O ₃ are present in both the solid electrolyte layer 3 (13) and the electrode layers 2, 4 (12, 14), and the bonding strength at the interface between these layers can be significantly 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 features such as high reliability, downsizing, low power consumption, improved responsiveness, and low cost.

[0023]

As described in detail above, according to the oxygen sensor of claim 1, a solid electrolyte layer containing 0.05 to 10.0% by weight of a trivalent or lower metal or its oxide, Trivalent or less metal or its oxide 0.05-1
Since the electrode layer containing 0.0 wt% is laminated and the obtained laminate is fired in an oxidizing atmosphere to bond the solid electrolyte layer and the electrode layer, the solid electrolyte and the electrode It is possible to greatly improve the bonding strength at the interface with. Therefore, it is possible to significantly improve the reliability of the oxygen sensor such as sensitivity, responsiveness and other electrical characteristics, and long-term life characteristics.

According to the method of manufacturing an oxygen sensor of claim 2, in the oxygen sensor of claim 1, the metal contains at least one selected from Cu, Bi, Zn and Cd. Therefore, the bonding strength at the interface between the solid electrolyte and the electrode can be significantly improved without impairing the characteristics of the solid electrolyte and the electrode. Therefore, it is possible to significantly improve the reliability of the oxygen sensor such as the sensitivity, the responsiveness, and other electrical characteristics, the long-term life characteristic, and the like.

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 shows the oxygen of Examples 1 and 2 in the experimental example of Table 1.
The figure which shows the conventional oxygen sensor compared with a sensor.

[Explanation of symbols]

6, 16 ... Oxygen sensor , 1 ... Substrate, 2, 4, 12, 14
... Pt electrode layer, 3, 13 ... 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. An electrode is laminated on both sides on a porous substrate.
And a porous solid electrolyte is provided in the solid electrolyte.
Oxygen concentration in the sample gas taken in restrictively through the substrate
The oxygen pumping action of the solid electrolyte
Oxygen sensor manufacturing method for measuring oxygen current
And a trivalent or lower metal or oxide thereof is added in an amount of 0.05 to 10.0.
A solid electrolyte layer containing wt% and an electrode layer containing 0.05 to 10.0 wt% of a trivalent or lower metal or its oxide are laminated, and the obtained laminate is fired in an oxidizing atmosphere, A method for manufacturing an oxygen sensor, comprising joining the solid electrolyte layer and the electrode layer. 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.