JPH06242067A - Limit current type oxygen sensor and manufacture thereof - Google Patents

Abstract

PURPOSE:To obtain a limit current type oxygen sensor which can be manufactured easily while ensuring long term reliability. CONSTITUTION:Platinun paste is screen printed at first on the opposite sides of a solid electrolyte substrate 1 and porous cathode and anode electrodes 2, 3 are formed oppositely. At the same time, an extention 2b is formed of the platinum paste from the cathode electrode 2 toward a corner part of the substrate 1. A paste composed of a mixture of crystallized glass and ceramic powder is then screen printed while covering the base end parts of the cathode electrode 2 and the extension 2b airtightly and subsequently fired to form a dome layer 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a limiting current type oxygen sensor which has a pair of electrodes arranged with a solid electrolyte substrate sandwiched therebetween and which detects the oxygen concentration in a gas by utilizing the limiting current characteristic, and the same. It relates to a manufacturing method.

[0002]

2. Description of the Related Art FIG. 7 is a sectional view showing an example of a conventional limiting current type oxygen sensor.

In the conventional limiting current type oxygen sensor,
A cathode electrode 42 and an anode electrode 43 are formed sandwiching a solid electrolyte substrate 41 made of stabilized zirconia. Each of these electrodes 42 and 43 is made of porous platinum, and gas can flow through the inside thereof. A cap 44 having a shape in which the lower end is opened is formed on the surface of the solid electrolyte substrate 41 on the cathode electrode 42 side.
Is provided with its lower end fixed to the substrate 41, whereby an internal space surrounded by the cap 44 and the substrate 41 is formed. The cathode electrode 42 is in contact with this internal space, and the anode electrode 43 is in contact with the external atmosphere.

The cap 44 is provided with one or a plurality of fine gas diffusion holes 44b so that the external atmosphere and the internal space communicate with each other through the gas diffusion holes 44b. Further, a heater 46 is provided on the outer surface of the cap 44, and when the heater 46 is energized, the heater 46 is resistively heated to heat the oxygen sensor. Further, the cathode electrode 42 and the anode electrode 43
A power source 49 is connected between the power source and the power source, and an ammeter 48 and a voltmeter 47 are connected to the power source 49 in series and in parallel, respectively.

In the conventional oxygen sensor having the structure described above, the oxygen sensor is heated to a high temperature by supplying electric power to the heater 46 to generate resistance heat, and at the same time, a predetermined voltage is provided between the cathode electrode 42 and the anode electrode 43 by the power source 49. Voltage (V) is applied. Then, due to the oxygen pumping action, oxygen molecules (O ₂ ) contained in the gas existing in the internal space surrounded by the solid electrolyte substrate 41 and the cap 44 obtain electrons through the cathode electrode 42, and oxygen is obtained. It becomes ions and enters the solid electrolyte substrate 41. The oxygen ions move in the substrate 41 in the thickness direction through the oxygen ion holes in the substrate 41. Then, the oxygen ions reach the anode electrode 43 to release electrons, and become oxygen molecules again to be released to the outside. Due to this movement of oxygen ions, a current (A) flows between the anode electrode 43 and the cathode electrode 42.

By the way, due to the movement of oxygen, the internal space of the oxygen sensor becomes a negative pressure, and the gas flows from the outside through the gas diffusion hole 44b. At this time, since the inflow amount of the gas is limited by the gas diffusion hole 44b, the current of the oxygen sensor-
In the voltage characteristics, a so-called flat region in which the current does not change even when the voltage applied between the cathode electrode 42 and the anode electrode 43 is increased is observed. This characteristic is called the limiting current characteristic, and the current at this time is called the limiting current.

The value of the limiting current of the limiting current type oxygen sensor is
If the shape of the gas diffusion hole, the temperature of the sensor during use, and the pressure of the atmosphere are constant, it depends on the oxygen concentration in the atmosphere. Therefore, if the relationship between the limiting current value and the oxygen concentration is obtained in advance, the oxygen concentration in the atmosphere of unknown oxygen concentration can be known by measuring the limiting current value.

[0008]

However, in the above-mentioned conventional limiting current type oxygen sensor, the cap 44 having the gas diffusion hole 44b is formed, and the cap 4 is formed.
4 needs to be bonded to the solid electrolyte substrate 41 provided with the electrodes 42 and 43, and there is a problem that the manufacturing is complicated and the manufacturing cost is high. Further, since the gas diffusion holes are formed by machining, there is a drawback that the variation of the limiting current characteristic is large. Furthermore, if foreign matter adheres to the gas diffusion holes, the flow of gas may be obstructed and the limiting current characteristics may change significantly. Therefore, the conventional limiting current type oxygen sensor is not sufficiently reliable when used for a long period of time.

The present invention has been made in view of the above problems, and it is easy to manufacture, the product cost can be reduced, the variation in the characteristics is small, and the long-term reliability can be secured. An object of the present invention is to provide a sensor and a manufacturing method thereof.

[0010]

A limiting current type oxygen sensor according to the present invention includes a solid electrolyte substrate, first and second porous electrodes arranged with the solid electrolyte substrate interposed therebetween, and the first and second porous electrodes. A porous electrode extension extending from the porous electrode toward the edge of the substrate, and a dome layer that hermetically covers the first porous electrode and the base end of the electrode extension. It is characterized by having.

In the method for manufacturing a limiting current type oxygen sensor according to the present invention, a conductive paste is printed in a specific pattern on the first surface of a solid electrolyte substrate to form a first porous electrode and the first porous electrode. A porous electrode extension extending from the electrode toward the edge of the substrate is formed, and a conductive paste is printed on the second surface of the substrate in a specific pattern to form a second porous electrode. And a step of forming a dome layer that hermetically covers the base end portions of the first porous electrode and the electrode extension portion by printing.

[0012]

In the limiting current type oxygen sensor according to the present invention, the first and second porous electrodes are arranged with the solid electrolyte substrate sandwiched therebetween, and the edge of the substrate is separated from the first porous electrode. A porous electrode extension portion extending toward the portion is provided. In addition, a dome layer that hermetically covers the base end portions of the first porous electrode and the electrode extension portion is provided.

In the limiting current type oxygen sensor according to the present invention configured as described above, for example, it is assumed that the first porous electrode is a cathode electrode and the second porous electrode is an anode electrode. When a voltage is applied between the anode electrodes, oxygen molecules in the gas that have penetrated into the cathode electrodes acquire electrons and become oxygen ions, and move in the thickness direction of the solid electrolyte substrate. Then, when the oxygen ions reach the anode electrode, they emit electrons and become oxygen molecules, which are released into the atmosphere. This movement of oxygen reduces the pressure of the gas in the cathode electrode, resulting in
Fresh gas flows into the cathode electrode through the porous electrode extension. In this case, the inflow amount of gas is regulated by the base end portion of the electrode extension portion. That is, in the limiting current type oxygen sensor according to the present invention, the electrode extension portion base end portion of the portion covered with the dome layer corresponds to the gas diffusion hole in the conventional limiting current type oxygen sensor. The amount of inflow of gas is limited by the base end, and the limiting current characteristic can be obtained.

In the limiting current type oxygen sensor according to the present invention, as described above, the base end portion of the electrode extension portion is covered with the dome layer, and the gas is supplied to the porous electrode by the base end portion of the electrode extension portion. Since the inflow rate is limited to obtain the limiting current characteristic, the process of drilling fine holes by machining which is required when manufacturing the conventional limiting current type oxygen sensor is not necessary, and the manufacturing is easy. . Further, since the gas to be measured flows into the porous electrode through the surface of the electrode extension portion, even if foreign matter adheres to a part of the surface of the electrode extension portion, there is little fluctuation in the gas inflow amount, It is possible to avoid large fluctuations in the limiting current characteristic. Therefore, the limiting current type oxygen sensor according to the present invention has high reliability even when used for a long period of time.

On the other hand, in the method of the present invention, a conductive paste is printed on the solid electrolyte substrate to form the first and second porous electrodes and the porous electrode extension, and further the dome layer is formed by printing. Then, the limiting current type oxygen sensor having the above structure is manufactured. According to the method of the present invention, an oxygen sensor is manufactured by using a printing technique such as screen printing, so that machining or the like for forming a gas diffusion hole is unnecessary, and an oxygen sensor can be easily manufactured, The process can be easily automated, and variations in the limiting current characteristics can be suppressed.

Incidentally, the smaller the porosity of the porous electrode (that is, the denser the structure), the better the adhesion between the porous electrode and the solid electrolyte substrate, but the impediment to the fluidity of gas in the electrode. To be done. Therefore, for example, the first porous electrode and the porous electrode extension have a two-layer structure,
The part in contact with the solid electrolyte substrate is formed of a conductive layer having a relatively low porosity, and when a conductive layer having a high porosity is formed on the lower conductive layer, good adhesion to the substrate and gas A porous electrode and an electrode extension having good fluidity can be obtained. Further, the first porous electrode is prepared by using a mixture of a plurality of kinds of conductive pastes having different porosities after firing instead of the porous electrode and the electrode extension portion having such a multilayer structure. Also, the electrode extension portion may be formed by printing. Also in this case, it is possible to obtain an electrode and an electrode extension that have good adhesion to the substrate and good gas flowability.

Further, the dome layer needs to cover the base end portions of the porous electrode and the electrode extension portion in an airtight manner, has good adhesion to the solid electrolyte substrate, and has the first feature. It is important not to impair the fluidity of gas in the porous electrode and the electrode extension. Therefore, the dome layer is formed by printing a paste in which crystallized glass and ceramic powder are mixed at a weight ratio of 1: 1 to 3: 1 (crystallized glass: ceramic powder). Preferably there is. That is, when the ratio of the crystallized glass to the ceramic powder is less than the above range, the adhesion between the dome layer and the solid electrolyte substrate deteriorates.
Further, when the ratio of the crystallized glass to the ceramic powder is higher than the above range, the glass penetrates into the porous electrode and the fluidity of gas in the porous electrode is hindered. In other words, by setting the ratio of the crystallized glass and the ceramic powder in the above range, the fluidity of the gas in the porous electrode is ensured and the adhesion of the dome layer to the solid electrolyte substrate is improved. be able to. Therefore, it is preferable that the dome layer is formed of a paste in which crystallized glass and ceramic powder are mixed in a weight ratio of 1: 1 to 3: 1.

[0018]

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

FIG. 1 is a plan view showing a limiting current type oxygen sensor according to an embodiment of the present invention, and FIG. 2 is a sectional view taken along line AA of FIG.

The solid electrolyte substrate 1 is formed by forming stabilized zirconia into a rectangular plate shape.
A cathode electrode 2 and an anode electrode 3 are formed in a substantially circular shape on the front surface and the back surface, respectively, and face each other across the substrate 1. Each of these electrodes 2 and 3 is made of porous platinum. In addition, lead wire attaching portions 2a and 3a are provided at corners of the substrate 1, and electrode extending portions 2b and 3b are provided from the cathode electrode 2 and the anode electrode 3 toward the lead wire attaching portions 2a and 3a, respectively. The electrodes 2 and 3 are extended, and the electrodes 2 and 3 are electrically connected to the lead wire attachment portions 2a and 3a, respectively, through the electrode extension portions 2b and 3b.

The dome layer 4 is formed in a substantially rectangular shape on the substrate 1 by airtightly covering the base end portions of the cathode electrode 2 and the electrode extension portion 2b, but is aligned with the lead wire attachment portion 2a. Triangular notches are provided at the corners. The dome layer 4 is made of, for example, glass mixed with ceramic powder.

On the dome layer 4, a heater 5 having a substantially ring shape is formed.
Is provided, and the heater 5 is electrically connected to the heater electrodes 5a and 5b also formed on the dome layer 4.

In the limiting current type oxygen sensor according to this embodiment having the above-mentioned structure, when a voltage is applied between the heater electrodes 5a and 5b, the heater 5 generates resistance heat and the sensor is heated to a high temperature. When a predetermined voltage is applied between the cathode electrode 2 and the anode electrode 3 in this state, the cathode electrode 2
Oxygen molecules contained in the gas inside the cathode electrode 2
The electrons are obtained through the above to become oxygen ions, and move in the thickness direction of the solid electrolyte substrate 1. Then, when the oxygen ions reach the anode electrode 3, they release electrons and become oxygen molecules again, and are released into the atmosphere. Due to the movement of oxygen, the inside of the cathode electrode 2 has a negative pressure, and new gas flows into the cathode electrode 2 through the electrode extension portion 2b. At this time, the inflow amount of gas is limited by the base end portion of the electrode extension portion 2b, and the limiting current characteristic is obtained as in the conventional limiting current type oxygen sensor.

In the present embodiment, the base end portion of the electrode extension portion 2b of the portion covered with the dome layer 4 corresponds to the gas diffusion hole in the conventional limiting current type oxygen sensor, and the dome layer is formed when the dome layer is formed. The limiting current characteristic of the sensor can be changed by changing the thickness, width or length of the base end portion of the electrode extension portion to be covered. In addition, since gas flows into the inside of the dome layer through the surface of the electrode extension portion of the portion exposed from the dome layer, even if foreign matter adheres to a part of the surface of the electrode extension portion 2b, the gas inflow amount Change is small. Therefore, the limiting current type oxygen sensor according to the present embodiment is highly reliable because the variation of the limiting current characteristic is suppressed even in the measurement over a long period of time. Further, in the present embodiment, unlike the conventional case, it is not necessary to form the gas diffusion hole by machining, so that the manufacturing is easy.

Next, a method of manufacturing the limiting current type oxygen sensor according to this embodiment will be described with reference to FIGS.

First, a platinum paste is screen-printed on both sides of a solid electrolyte substrate 1 made of stabilized zirconia, and then fired to form a cathode electrode 2, an anode electrode 3, and porous electrode extensions 2b and 3b having a porous structure. To form.

In this case, the cathode electrode 2 and the electrode extension portion 2b may be a single conductive layer, but have, for example, a two-layer structure of a lower electrode layer and an upper electrode layer, and the lower electrode layer is The upper electrode layer may be made of platinum having a relatively dense structure and excellent adhesion to the substrate 1, and the upper electrode layer may be made of platinum having high porosity and excellent gas flowability. Further, for example, the cathode electrode 2 and the electrode extension portion 2b are formed of a mixture of a conductive paste having a relatively high porosity after firing and a conductive paste having a relatively low porosity after firing. Good. By forming the cathode electrode 2 and the electrode extension 2b in this way, both the adhesion to the solid electrolyte substrate 1 and the fluidity of gas inside the solid electrolyte substrate 1 can be improved.

Next, a paste obtained by mixing crystallized glass and ceramic powder is screen-printed on the surface on the cathode electrode 2 side to cover the cathode electrode 2 and the base end portions of the electrode extension 2b. Then, the paste is fired to form the dome layer 4. In this case, the ratio of the crystallized glass and the ceramic powder in the paste is 1: 1 to 3: by weight.
It is preferably 1. As a result, it is possible to prevent the glass from entering the porous cathode electrode 2 and the electrode extension portion 2b, and to improve the adhesion between the dome layer 4 and the substrate 1.

Next, platinum paste is screen-printed on the dome layer 4 and then fired to form the heater 5 and the heater electrodes 5a and 5b. As a result, the oxygen sensor according to this example is completed.

As described above, the oxygen sensor according to the present embodiment has the electrodes 2 and 3 and the electrode extension 2 formed by screen printing.
b, 3b, the dome layer 4, the heater 5, etc. are formed,
It is easy to manufacture and the product cost can be reduced. Further, since the limiting current characteristic changes only by changing the ratio of covering the electrode extension portion 2b with the dome layer 4, it is possible to easily manufacture an oxygen sensor having a desired limiting current characteristic. Furthermore, since the limiting current type oxygen sensor according to the present embodiment is manufactured by using the screen printing technique, it is possible to suppress variations in products by automatic printing.

Next, the result of actually manufacturing the limiting current type oxygen sensor according to this embodiment and examining its characteristics will be described.

Example 1 First, as shown in FIG. 3, as a solid electrolyte substrate 11,
A zirconia substrate having a square shape with one side of 3 mm and a thickness of 0.14 mm was prepared. Next, a platinum paste is screen-printed on the upper surface of the substrate 11 and then fired to form a cathode electrode 12 having a porous structure with a diameter of 2 mm and a thickness of about 5 μm, and from this cathode electrode 12 toward the corner of the substrate. A porous electrode extension 12b was formed to extend. Similarly, a platinum paste is screen-printed on the lower surface of the substrate 1 and then fired to form a porous anode electrode 13 having a diameter of 2 mm and a thickness of about 5 μm and a substrate angle from the anode electrode 13. An extension portion (not shown) extending toward the portion was formed.

Next, a paste obtained by mixing crystallized glass and ceramic powder (steatite powder) in a weight ratio of 2: 1 was screen-printed on the surface of the cathode electrode 12 side,
Then, it was fired to form a dome layer 14 that covers the cathode electrode 12 and the base end of the electrode extension.

Next, a Pt paste was printed on the dome layer 14 and then fired to form a heater (not shown).

The limiting current characteristics of the limiting current type oxygen sensor manufactured as described above were examined. FIG. 4 is a graph showing the limiting current characteristics of the above oxygen sensor, with the horizontal axis representing the sensor voltage and the vertical axis representing the current value. As is clear from this graph, the oxygen sensor according to the present example had good limiting current characteristics and excellent responsiveness, thermal stability, and long-term reliability.

Example 2 First, as shown in FIG. 5, a Pt paste (U-3401; N) was formed on the upper surface of a solid electrolyte substrate 21 made of zirconia having a side of 3 mm and a thickness of 0.14 mm. (E-Chemcat Co., Ltd.) was screen-printed with a desired pattern of the cathode electrode and the electrode extension, and then fired to form a lower electrode layer 27 having a thickness of about 3 μm.
Then, the Pt paste (# 5
542; manufactured by ESL Co., Ltd.) was screen-printed and then fired to obtain a cathode electrode 22 and an electrode extension 22b having a diameter of 2 mm and a thickness (including the lower electrode layer 27) of about 5 μm.

Next, Pt paste (U-3401) is screen-printed on the back side of the substrate 21 and then fired to form an anode electrode 23 having a diameter of 2 mm and a thickness of about 3 μm.
Further, an electrode extension portion (not shown) extending from the anode electrode 23 toward the corner portion of the substrate was formed.

Next, a paste obtained by mixing crystallized glass and ceramic is screen-printed so as to cover the base ends of the cathode electrode 22 and the electrode extension 22b,
Then, the dome layer 24 was formed by firing. Then, a Pt paste was screen-printed on the dome layer 24 in a heater pattern and then fired to form a heater 26.

In the limiting current type oxygen sensor manufactured as described above, oxygen (O ₂ ) in the gas to be measured is mainly passed through the upper layer portion of the electrode extending portion 22b as indicated by the arrow in the figure. It flows into the upper layer portion of the cathode electrode 22, becomes oxygen ions in the cathode electrode 22, and moves the substrate 21 in the thickness direction. When it reaches the anode electrode 23, it becomes oxygen molecules again and is released into the atmosphere.

The limiting characteristics of the limiting current type oxygen sensor of this example were examined. As a result, the oxygen sensor of the present example has a good limiting current characteristic that is substantially the same as the limiting current characteristic of the limiting current type oxygen sensor of Example 1, and responsiveness, thermal stability, and long-term reliability. Was also excellent. In addition, in this embodiment, the cathode electrode 22 has a two-layer structure including a lower electrode layer having a relatively dense structure and good adhesion to the solid electrolyte, and an upper electrode layer having a porous structure. Both the adhesion to the electrolyte substrate and the fluidity of the gas in the cathode electrode are good.

Example 3 A limiting current type oxygen sensor was manufactured in the same manner as in Example 2 described above. However, for the cathode electrode, the first Pt paste (U-3401) was screen-printed and then dried (that is, without firing), and then the second Pt paste ( # 5542) was screen-printed and then fired to form a two-layer structure. In this case, the thickness of the first Pt paste after drying is about 4 μm, and the thickness of the cathode electrode and the electrode extension after firing is about 5 μm.

The limiting current characteristics of the limiting current type oxygen sensor manufactured as described above were examined. As a result, like Example 2, it had good limiting current characteristics and was excellent in responsiveness, thermal stability, and long-term reliability. did it.

Example 4 First, as shown in FIG. 6, a Pt paste was screen-printed on the upper surface of a solid electrolyte substrate 31 made of zirconia with a side of 3 mm and a thickness of 0.14 mm.
Then, it was fired to form a cathode electrode 32 having a diameter of 2 mm and a thickness of about 3 μm, and an electrode extension 32b extending from the cathode electrode 32 toward the corner of the substrate. This Pt
The paste is a mixture of Pt paste (U-3401) having a small porosity after firing and a relatively dense structure and Pt paste (# 5542) having a high porosity after firing.

Next, Pt paste (U-3401) is screen-printed on the back side of the substrate 31 and then baked to form an anode electrode 33 having a diameter of 2 mm and a thickness of about 3 μm.
Further, an electrode extension portion (not shown) extending from the anode electrode 33 toward the corner portion of the substrate was formed.

Next, a paste in which crystallized glass and ceramic are mixed is printed so as to cover the base ends of the cathode electrode 32 and the electrode extension portion 32b, and then the paste is fired to form the dome layer 34. . Then, a Pt paste was screen-printed on the dome layer 34 and then fired to form a heater (not shown).

In the limiting current oxygen sensor manufactured as described above, oxygen molecules (O ₂ ) in the gas to be measured enter the cathode electrode 32 through the electrode extending portion 32b as shown by the arrow in the figure. Then, it becomes oxygen ions and moves in the thickness direction of the substrate 1, and when they reach the anode electrode 33, they become oxygen molecules again and are released into the atmosphere.

The limiting current characteristics of the limiting current type oxygen sensor of this example were examined. As a result, the oxygen sensor of this embodiment also
Like the limiting current type oxygen sensor of Example 1, it had good limiting current characteristics, and was excellent in responsiveness, thermal stability, and long-term reliability.

[0048]

As described above, according to the present invention, the first and second porous electrodes are arranged with the solid electrolyte substrate sandwiched therebetween, and the edge of the substrate is separated from the first porous electrode. A porous electrode extending portion extending toward the portion is provided, and the base end portions of the first porous electrode and the electrode extending portion are airtightly covered by a dome layer. The amount of gas flowing into the first porous electrode is limited by the base end portion of the electrode extension portion, and the limiting current characteristic can be obtained. Therefore, the limiting current type oxygen sensor according to the present invention does not require mechanical processing for forming the gas diffusion holes as in the conventional case, and is easy to manufacture. Further, the limiting current type oxygen sensor according to the present invention also has an effect that the long-term reliability is higher than that of the conventional limiting current type oxygen sensor.

On the other hand, according to the method of the present invention, by printing the conductive paste, the first and second porous electrodes and the porous material extending from the first porous electrode toward the edge of the solid electrolyte substrate. Since the electrode extending portion is formed and the dome layer covering the first porous electrode and the base end portion of the electrode extending portion is formed by printing, the limiting current type oxygen sensor having the above structure can be easily formed. It can be manufactured. In addition, the manufacturing process can be easily automated, and variations in the limiting current characteristics can be suppressed.

[Brief description of drawings]

FIG. 1 is a plan view showing a limiting current type oxygen sensor according to an embodiment of the present invention.

FIG. 2 is a sectional view taken along the line AA of FIG.

FIG. 3 is a cross-sectional view showing a limiting current type oxygen sensor according to a first embodiment.

FIG. 4 is a graph showing the result of examining the limiting current characteristic of the same.

FIG. 5 is a cross-sectional view showing a limiting current type oxygen sensor according to a second embodiment.

FIG. 6 is a sectional view showing a limiting current type oxygen sensor according to a fourth embodiment.

FIG. 7 is a cross-sectional view showing an example of a conventional limiting current type oxygen sensor.

[Explanation of symbols]

 1, 11, 21, 31, 41; Solid electrolyte substrate 2, 12, 22, 32, 42; Cathode electrode 2b, 3b, 12b, 22b, 32b; Electrode extension part 3, 13, 23, 33, 43; Anode Electrodes 4, 14, 24, 34; Dome layers 5, 26, 46; Heater 44; Cap 44b; Gas diffusion hole

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Issei Ishibashi 1-5-1 Kiba, Koto-ku, Tokyo Fujikura Ltd. (72) Inventor Yoshinori Kato 1-1-5 Kiba, Koto-ku, Tokyo Shares Inside Fujikura

Claims (5)

[Claims] 1. A solid electrolyte substrate, first and second porous electrodes arranged with the solid electrolyte substrate sandwiched therebetween, and extending from the first porous electrode toward an edge portion of the substrate. A limiting current type oxygen sensor comprising: a porous electrode extension portion; and a dome layer that hermetically covers the first porous electrode and the base end portion of the electrode extension portion. 2. The first surface of the solid electrolyte substrate is printed with a conductive paste in a specific pattern to extend from the first porous electrode and the first porous electrode toward the edge of the substrate. Forming a porous electrode extending portion for forming the second electrode of the substrate.
Print the conductive paste on the surface of the
And a step of forming a dome layer for airtightly covering the base end portions of the first porous electrode and the electrode extension by printing. Limiting current type oxygen sensor manufacturing method. 3. The limiting current according to claim 2, wherein the first porous electrode and the electrode extension portion are formed by stacking a plurality of conductive layers having different porosities. Method of manufacturing oxygen sensor. 4. The first porous electrode and the electrode extension portion are formed by printing a mixture of a plurality of kinds of conductive pastes having different porosities after firing. The method for manufacturing a limiting current type oxygen sensor according to claim 2. 5. The dome layer comprises crystallized glass and ceramic powder in a weight ratio of 1: 1 to 3: 1 (crystallized glass:
5. The method for producing a limiting current type oxygen sensor according to claim 2, wherein the paste is formed by mixing and mixing in a ratio of ceramic powder) to form a paste.