JP2003194766A - Oxygen sensor and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that high strength in junction strength and high strength in solid electrolyte are required to the junction strength of solid electrolyte and a platinum electrode and strength in solid electrolyte, and reduction in the lamination count in the manufacture of a ceramic green sheet or that in the cracks of the ceramic green sheet itself, are required. <P>SOLUTION: In the oxygen sensor that comprises zirconia solid electrolyte while a porous electrode is formed against both the sides of the main surface, there are at least two peaks in the grain size of the crystal particle of zirconia for forming the solid electrolyte, the first peak ranges from 0.15 to 0.25 μm, the second peak ranges from 0.25 to 0.35 μm, and the difference of the two peaks ranges from 0.03 to 0.2 μm. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oxygen sensor for controlling the ratio of air to fuel in an internal combustion engine such as an automobile and a method for manufacturing the oxygen sensor.

[0002]

2. Description of the Related Art Currently, in internal combustion engines such as automobiles,
By detecting the oxygen concentration in the exhaust gas and controlling the supply amount of air and fuel supplied to the internal combustion engine based on the detected value, harmful substances such as CO and H from the internal combustion engine can be controlled.
A method of reducing C and NOx is adopted.

As an oxygen sensor for detecting such oxygen concentration, as shown in FIG. 3, a solid electrolyte 3 mainly containing zirconia having oxygen ion conductivity is provided with a ceramic porous layer 15 acting as a protective layer. And a measurement electrode 4 in contact with the outside air, a reference electrode 5 facing the air introduction hole 7, and a heater portion composed of a thin ceramic insulating layer 11 in which a heating element 13 made of Pt or the like is embedded in the solid electrolyte 3. An integrated oxygen sensor element has been proposed (JP-A-2-276857).

Further, as shown in FIG. 4, a sensor substrate 2 in which a measuring electrode 4 containing platinum as a main component and a reference electrode 5 are formed on a solid electrolyte 3 mainly containing zirconia having oxygen ion conductivity, The heater substrate 10 made of alumina having the heat generating portion 12 is arranged via a gap, and the porous ceramic layer 19 is arranged in the gap. In such an oxygen sensor 1, the heat generated by the heater is porous. The sensor substrate 2 is overheated through the ceramic layer 19.

This porous ceramic layer is used for the sensor substrate 2
It is manufactured by inserting a ceramic green sheet into the gap between the heater substrate 10 and the heater substrate 10 or filling a paste with the paste, and then simultaneously firing the sensor substrate 2, the heater substrate 10 and the porous ceramic layer 19 (Japanese Patent Application No. 4- 329352).

[0006]

However, in the above oxygen sensor, it is desired to improve the bonding strength between the solid electrolyte 3 and the measurement electrode 4 and the reference electrode 5 and to increase the strength of the solid electrolyte itself. Further, it is desired to reduce the number of laminations of the ceramic green sheets and the cracks in the ceramic green sheets themselves in the production of the ceramic green sheets forming the solid electrolyte 3.

As for the solid electrolyte 3, ceramic green sheets are laminated, and although the ceramic green sheets have been manufactured using resins such as acrylic and butyral, the coprecipitation raw material is used as the zirconia raw material used as the solid electrolyte 3. Since the raw material has a very small particle size and the drying shrinkage when forming the ceramic green sheet is large, cracks are likely to occur in the ceramic green sheet during drying. Therefore, the ceramic green sheet can be produced only when the thickness is 100 μm or less, and when the thickness is 100 μm or more, the ceramic green sheet is cracked.

[0008]

Means for Solving the Problems The present invention provides an oxygen sensor in which a porous electrode is formed so as to face both main surfaces of a zirconia solid electrolyte, and the particle size distribution of crystal particles of zirconia forming the solid electrolyte is Has at least two peaks with the first peak at 0.15-0.25 μm,
The second peak is at 0.25 to 0.35 μm, and 2
The difference between the two peaks is 0.03 to 0.2 μm.

Further, there is provided an oxygen sensor in which a porous electrode is formed so as to face both main surfaces of a zirconia solid electrolyte, wherein the first zirconia raw material has a specific surface area of 12 to 18 m ² / g and 20 to 80 mass%. , A ceramic green sheet made of a zirconia solid electrolyte prepared by mixing 80 to 20% by mass of a second zirconia raw material having a specific surface area of 3 to 10 m ² / g as a base material, and a porous electrode on the ceramic green sheet. It is characterized by including a step of forming.

[0010]

1 is an exploded perspective view showing an example of the basic structure of an oxygen sensor of the present invention, and FIG. 2 is a perspective view and a sectional view thereof.

This oxygen sensor 1 is generally called a theoretical air-twisting ratio sensor (λ sensor) element. The sensor substrate 2 is made of a solid electrolyte 3 made of zirconia and having oxygen ion conductivity, and its tip is sealed. A reference electrode 5 that is a flat plate-shaped hollow body that is in contact with a reference gas such as air is deposited and formed inside the hollow body.

A measuring electrode 4 is formed outside the hollow body at a position facing the reference electrode 5 so as to come into contact with a measured gas such as exhaust gas. Both the reference electrode 5 and the measurement electrode 4 are porous platinum electrodes. In this case, a ceramic porous layer 15 is formed on the surface of the measurement electrode 4 as an electrode protection layer from the viewpoint of preventing poisoning of the measurement electrode 4 by exhaust gas.

As shown in FIG. 2, the sensor substrate 2 has a heater substrate 10 made of alumina in which a heating element 12 is embedded.
Is fixed.

In the oxygen sensor of the present invention, the material of the solid electrolyte 3 is made to have a specific surface area of 12 to 18 m ² / in order to increase the thickness of the ceramic green sheet and suppress the occurrence of cracks.
g of the first zirconia raw material 20 to 80% by mass, and a specific surface area of 3 to 10 m ² / g of the second zirconia raw material 80 to 20
It was prepared by mixing with% by mass. By adjusting the raw materials in this way, it was possible to prevent the occurrence of cracks in the tape when a tape having a thickness of 100 to 200 μm was formed.

The zirconia raw material having a large specific surface area has a very small particle diameter, and a large amount of solvent is required to disperse the raw material in the solvent. When the solvent is dried to obtain a ceramic green sheet, shrinkage occurs. The size of the ceramic green sheet becomes large and cracks are easily generated in the ceramic green sheet.
Further, the generation of cracks due to drying shrinkage was more remarkable as the thickness of the ceramic green sheet increased. On the other hand, as described above, the specific surface area is 1
By mixing ^{2 to} 18 m ² / g of zirconia raw material and 3 to 10 m ² / g of zirconia raw material, it is possible to reduce the drying shrinkage and prevent the occurrence of cracks in the ceramic green sheet. At the same time, it has become possible to form a ceramic green sheet having a thickness of about 50 μm in the past up to about 200 μm without cracks.

As a result, the solid electrolyte layer of the oxygen sensor, which has conventionally been required to be laminated in the form of 3 to 4 layers (not shown), is a solid electrolyte having a target thickness of 2 layers. The layers can now be processed.

Then, the crystal grain size of the fracture surface of the solid electrolyte 3 of the oxygen sensor 1 of the present invention thus produced was confirmed. As shown in FIG. 6, the grain size of the zirconia crystal grains forming the solid electrolyte 3 was confirmed. There are at least two distribution peaks, the first peak is at 0.15-0.25 μm, the second peak is at 0.25-0.35 μm, and the difference between the two peaks is 0.03. It was found to be 0.2 μm. Further, by adjusting the crystal grain size of the solid electrolyte 3 in this way, the four-point bending strength of the solid electrolyte 3 could be improved at the same time.

The zirconia raw material used in the present invention has a very large specific surface area as compared with general ceramics, so it is difficult to densify it during firing, and when sintering progresses from the surface of zirconia, bubbles remain at the grain boundaries. The bubbles tended to occur easily, and this bubble was a cause of lowering the porcelain strength of the solid electrolyte 3 made of zirconia. On the other hand, by blending the particle size of the zirconia raw material as in the present invention,
It is presumed that it became difficult for bubbles to remain between the crystal grains.

Here, a method for measuring the crystal grain size of the solid electrolyte 3 will be described. First, the solid electrolyte 3 was fractured, and a cross-section was taken of an electron microscope (SEM) photograph at a magnification of 20000. The electron microscope photograph was image-analyzed to measure the grain size distribution of zirconia. The crystal grain size was calculated by converting the crystal grain size into a circle equivalent diameter and calculating 0.001.
The evaluation was performed in μm unit, and the data was counted until the number exceeded 1000. Further, the pitch (interval) of particle diameters in data processing is preferably 0.01 to 0.04 μm. Arranging with a pitch smaller than 0.01 μm is not preferable because the variation of the crystal grain size distribution becomes large and the distribution cannot be confirmed. In addition, when the data is summarized at a pitch exceeding 0.04 μm, the crystal grain size distribution becomes rough, and it may not be possible to separately confirm the grain size distribution using zirconia raw materials having different raw material grain sizes.

The oxygen sensor of the present invention may have the structure shown in FIGS. 3 and 4, or the air-fuel ratio sensor 1 shown in FIG. 5 may be used. This air-fuel ratio sensor 1
Has a small hole called a diffusion hole 20 for taking in exhaust gas in the plate-shaped solid electrolyte 3, and when a pair of platinum electrodes composed of a measurement electrode 4 and a reference electrode 5 are formed on both surfaces thereof. At the same time, a pumping cell in which the space 16 is formed by the solid electrolyte 3 is formed. Further, it has a structure in which a pair of measurement electrodes 4 and reference electrodes 5 called sensing cells are formed on both surfaces of the solid electrolyte 3 formed with the space 16 interposed therebetween. At this time, the reference electrode is brought into contact with the atmosphere through the air introduction hole. The above-mentioned space may be filled with a porous ceramic in order to provide the strength of the cell.

On the other hand, the heater substrate 10 of the oxygen sensor 1 is
It has the same flat plate shape as the sensor substrate 2 described above, and contains W, Mo, Re in a ceramic insulator 11 containing alumina as a main component.
A heating element 12 made of, for example, is buried. In the present invention, in order to efficiently overheat the sensor substrate 2, the distance from the heating element 12 to the surface of the heater substrate 10 in contact with the sensor substrate 2 is preferably 200 to 600 μm. If this distance is less than 200 μm, the heat resistance of the heater substrate 10 deteriorates. Further, if this distance exceeds 600 μm, the heat transfer from the heater substrate 10 to the sensor substrate 2 deteriorates, and as a result, the gas responsiveness of the sensor substrate 2 deteriorates. Heater substrate 1 in contact with sensor substrate 2 from heating element 12
The distance to the 0 surface is particularly preferably 300 to 400 μm.

The thickness of the heater substrate 10 is 0.7.
˜2 mm, especially 1 to 1.5 mm is preferable from the viewpoint of strength. If the thickness of the heater substrate 10 is less than 0.7 mm, the strength of the substrate is low, and if it exceeds 2 mm, the heater substrate 10 and the sensor substrate 2 adjacent thereto are heated, and a large amount of electricity is required, which is not preferable.

Further, another oxygen sensor 1 structure of the present invention is a lean burn sensor having a pumping cell in which a pair of electrodes and a small hole 8 for taking in exhaust gas are formed on both surfaces of a solid electrolyte 3. The structure is also included.

Next, the constituent elements of the sensor substrate 2 will be described.

According to the oxygen sensor 1 of the present invention, the surface of the measuring electrode 4 which is in direct contact with the exhaust gas has a function of protecting the measuring electrode 4 from poisonous substances in the exhaust gas, and the other is the air-fuel ratio sensor. For the purpose of controlling the amount of gas diffusion into the space surrounded by the solid electrolyte 3, a ceramic porous layer made of zirconia, alumina, γ-alumina, spinel, etc. having a thickness of 10 to 800 μm and a porosity of 10 to 50%. Stratum 15
Is provided. If the thickness of the ceramic porous layer 15 is less than 10 μm or the porosity exceeds 50%, the electrode poisoning substances P, Si, etc. easily reach the measurement electrode 4 and the electrode performance deteriorates. On the other hand, if the thickness of the ceramic porous layer 15 exceeds 800 μm or the porosity becomes less than 10%, the diffusion rate of gas in the ceramic porous layer 15 becomes slow and the gas responsiveness of the oxygen sensor 1 deteriorates. . Particularly, the thickness of the ceramic porous layer 15 is preferably 100 to 500 μm, though it depends on the porosity.

The reference electrode 5 and the measuring electrode 4 deposited on the surface of the solid electrolyte 3 are both made of platinum or an alloy of platinum and one kind selected from the group of rhodium, palladium, ruthenium and gold. To be Further, the purpose of preventing the grain growth of the metal in the reference electrode 5 and the measurement electrode 4 during the sensor operation, and the purpose of increasing the contact point of the so-called three-phase interface between the metal particles, the solid electrolyte 3, and the gas, which are responsible for the responsiveness. so,
1 to 50% by volume, particularly 10 to 3% by volume of the above-mentioned solid electrolyte
You may mix in the said electrode in the ratio of 30 volume%.

The shape of the electrodes may be square or elliptical. The thickness of the electrode is 3 to 20 μm.
m, especially 5 to 10 μm is preferable.

A heating element 12 embedded in the heater substrate 10.
Is preferably composed of one or more of W, Mo and Re from the viewpoint of heat resistance and manufacturing cost. The composition of the heating element 12 may be appropriately selected depending on the heating capacity and the temperature rising rate. In this case, it is preferable to control the resistance ratio between the heating element 12 and the lead portion 13 in the range of 9: 1 to 7: 3 at room temperature. As the structure of the heating element 12, it is possible to use either a structure folded back to the left or the right or a structure folded back in the longitudinal direction.

The heater substrate 10 contains alumina as a main component, and Mg, Ca, and Si may be added in a total amount of 1 to 10% by weight for the purpose of improving sinterability.
K or the like migrates and deteriorates the electric insulation of the heater substrate, so it is necessary to control the content to 0.1% by weight or less.

Next, a method of manufacturing the oxygen sensor 1 of the present invention will be described by taking the method of manufacturing the oxygen sensor 1 of FIG. 3 as an example.

First, a method for manufacturing the hollow flat sensor substrate 2 with one end sealed as shown in FIG. 1 will be described in detail with reference to FIG. A ceramic green sheet made of zirconia is a doctor blade method, extrusion molding, or hydrostatic molding (rubber press) by appropriately adding a molding organic binder to a ceramic solid electrolyte powder having oxygen ion conductivity such as zirconia. Alternatively, it is produced by a known method such as press forming.

At this time, the solid electrolyte powder used is zirconia powder, and Y ₂ O ₃ and Yb ₂ O ₃ , Sc ₂ O ₃ , Sm ₂ O ₃ , Nd ₂ O ₃ and Dy are used as stabilizers. ₂
A mixed powder in which a rare earth oxide powder such as O ₃ is added in an amount of 1 to 30 mol%, preferably 3 to 15 mol% in terms of oxide, or a coprecipitated raw material powder of zirconia and the above stabilizer is used. . Further, it is also possible to use a ZrO ₂ powder in which 1 to 20 atomic% of Zr in ZrO ₂ is replaced with Ce, or a coprecipitation raw material. Further, for the purpose of improving the sinterability, Al ₂ O ₃ or SiO ₂ can be added to the solid electrolyte powder in an amount of 5% by mass or less, particularly 2% by weight or less. Here, the grain distribution state of zirconia for forming the ceramic green sheet into a pressure film and suppressing cracks will be described. The specific surface area of the first zirconia is 12 to 18
80 used as the specific surface area of 20 to 80 wt% second zirconia 3 to 10 m ² / g, using those m ² / g
A ceramic green sheet is obtained by mixing 20% by mass to prepare a slurry. Further, the ceramic green sheets are laminated to form a sheet having an appropriate thickness.

Next, on both surfaces of the above-mentioned ceramic green sheet, patterns to serve as the measurement electrode 4 and the reference electrode 5, respectively, are formed by using a conductive paste containing platinum, for example, by a slurry dip method, screen printing, pad printing, roll. After forming by transfer, although omitted in FIG. 5,
In order to protect the surface of the measurement electrode 4 that is in direct contact with the exhaust gas, a ceramic porous layer 15 made of zirconia, alumina, γ-alumina, spinel, etc. is similarly formed by the slurry dip method, screen printing, pad printing,
It is formed by roll transfer.

Thereafter, the ceramic green sheets on which the measurement electrodes 4 and the reference electrodes 5 are printed are interleaved with an adhesive such as an acrylic resin or an organic solvent according to FIG. 2 or by a roller or the like. A laminate of sensing element substrates is produced by mechanically adhering while applying pressure.

The firing of the sensing element substrate is carried out in the air or an inert gas atmosphere at a temperature range of 1300 ° C. to 1500 ° C. for 1 to 10 hours. At this time, in order to suppress warpage of the sensor substrate 2 during firing, the amount of warpage can be reduced by placing a smooth substrate such as alumina as a weight on the laminate.

Next, a method of manufacturing the heater substrate 10 shown in FIG. 5 will be described.

A ceramic green sheet of alumina is produced by adding a molding organic binder to alumina powder by a well-known method such as a doctor blade method, extrusion molding, hydrostatic molding (rubber press) or press molding. . At this time, as the alumina powder, alumina, as a main component, is used for the purpose of improving sinterability.
A powder to which i is added in a total amount of 1 to 10% by weight is preferably used.

On one surface of the above-mentioned ceramic green sheet, a conductive paste containing W, Mo, Re or the like is used to form a heating element pattern by a slurry dip method, screen printing, pad printing or roll transfer. The heater substrate 1 is formed by adhering the ceramic green sheets with an adhesive such as a solvent interposed therebetween, or by mechanically adhering them while applying pressure with a roller or the like.
A laminated body of 0 is manufactured according to FIG. At this time, the heating element 12
It is important that the printing is performed so that the S1 / a ratio becomes a predetermined ratio after firing as described above.

The heating of the heater substrate 10 is performed in a temperature range of 1400 ° C. to 1600 ° C. for 5 to 10 hours in a reducing gas atmosphere such as forming containing hydrogen and the like from the viewpoint of preventing the heating element 12 from being oxidized. At this time, the heater substrate 1 during firing
In order to suppress the warp of 0, the amount of warp can be reduced by placing a smooth substrate such as alumina as a weight on the laminated body so as to apply a weight.

The present invention can be applied to a wide range air-fuel ratio sensor as described above. As shown in FIG. 5, the sensor substrate 2 of the air-fuel ratio sensor is a slurry dip method or a screen using a conductive paste containing platinum for the measurement electrode 4 and the inner electrode 5 as pumping electrodes on both sides of the above-mentioned ceramic green sheet. It is formed by printing, pad printing, and roll transfer. Further, a conductive electrode containing platinum is also used on both sides of the other ceramic green sheet to measure the electrode 4 by slurry dip method, screen printing, pad printing or roll transfer.
And the reference electrode 5 is formed. Then, after forming the ceramic porous layer 15 on the surface of the measurement electrode 4 (omitted in FIG. 5), a zirconia spacer is inserted as shown in FIG. Stack green sheets. At this time, the lamination can be performed by interposing an adhesive such as an acrylic resin or an organic solvent between the ceramic green sheets for adhesion, or mechanically adhering while applying pressure with a roller or the like. The firing is performed in the air or in an inert gas atmosphere at 1300 ° C. to 1 in the same manner as the theoretical air-fuel ratio sensor.
It is carried out in the temperature range of 500 ° C. for 1 to 10 hours.

The diffusion holes for introducing the exhaust gas may be formed at the time of forming the laminated body before firing, or may be formed by ultrasonic processing or laser processing after firing. The size of this hole is 0.1 depending on the thickness of the solid electrolyte 3.
A size of ˜0.5 mm, especially 0.2 to 0.4 mm is preferred.

After that, the heater substrate 10 prepared separately is used.
Then, the sensor substrate 2 is fixed and the oxygen sensor 1 is manufactured.

[0043]

EXAMPLE 1 An example of the present invention will be described by taking the stoichiometric air-fuel ratio sensor shown in FIGS. 1 and 2 as an example.

Commercially available alumina powder containing 5% by weight of Si, Mg and Ca, and 5 mol% Y ₂ O ₃ containing 0.1% by weight of Si.
Containing zirconia powder, platinum powder containing 30% by volume of zirconia powder consisting of 8 mol% yttria, and W
Each powder was prepared.

First, an acrylic resin solution was added to zirconia powder containing 5 mol% Y ₂ O ₃ to prepare a slurry,
A ceramic green sheet made of zirconia having a thickness of 0.2 mm after sintering was prepared by the doctor blade method. At this time, the material of the solid electrolyte 3 is set to have a specific surface area of the first zirconia powder of 15 m ² / g, a compounding amount of 50% by mass, and a specific surface area of the second zirconia powder of 5 m.
^A ceramic green sheet was prepared by a doctor blade method by preparing a slurry with a compounding amount of ² / g and a blending amount of 50% by mass. After that, platinum containing zirconia powder is screen-printed on both sides of the ceramic green sheet to prepare the measurement electrode 4 and the reference electrode 5, and then a spacer made of zirconia is inserted as shown in FIG. A laminate of sensing element substrates was prepared with the agent.

After that, the laminated body was fired in the atmosphere at 1500 ° C. for 1 hour to prepare a sensor substrate 2. At this time, smooth alumina substrates having different weights were placed on the laminate and fired. The warpage of the sensor substrate 2 was measured using a surface roughness meter.

In this experiment, for the sake of comparison, the same measurement was carried out for an oxygen sensor integrated with a commercially available heater.

At this time, as shown in Table 1, a difference in bending strength was found depending on the peak state of the particle size distribution. Also, by blending zirconia raw materials with different specific surface areas, it was possible to increase the thickness of the ceramic green sheet and suppress cracks.

[0049]

[Table 1]

[0050]

According to the present invention, in an oxygen sensor made of a zirconia solid electrolyte and having porous electrodes formed so as to face each other on both sides of its main surface, the particle size of the zirconia crystal particles forming the solid electrolyte is large. There are at least two distribution peaks, and the first peak is 0.15-0.25 μm
And the second peak is 0.25 to 0.35 μm, and the difference between the two peaks is 0.03 to 0.2 μm, the bonding strength between the solid electrolyte and the platinum electrode and the strength of the solid electrolyte. On the other hand, high bonding strength and high strength of the solid electrolyte can be achieved.

Further, there is provided an oxygen sensor comprising a zirconia solid electrolyte, in which porous electrodes are formed so as to face each other on both sides of the main surface thereof, wherein the ceramic green sheet made of the zirconia solid electrolyte is used as a base material. In the oxygen sensor that is processed and adhered to the sheet,
The ceramic green sheet has a specific surface area of 12 to 18
20-80 mass% of the first zirconia raw material of m ² / g,
Second zirconia raw material 80 having a specific surface area of 3 to 10 m ² / g
It is possible to reduce the number of times the ceramic green sheets are laminated and to reduce cracks in the ceramic green sheets themselves by mixing the ceramic green sheets with 20 to 20% by mass.

[Brief description of drawings]

FIG. 1 is an exploded perspective view showing an oxygen sensor of the present invention.

FIG. 2A is a perspective view of an oxygen sensor of the present invention,
(B) is the EE sectional drawing, and (c) is the FF.
FIG.

FIG. 3 is a sectional view showing another embodiment of the oxygen sensor of the present invention.

FIG. 4 is a sectional view showing another embodiment of the oxygen sensor of the present invention.

FIG. 5 is an exploded perspective view showing another embodiment of the oxygen sensor of the present invention.

FIG. 6 is a graph showing the particle size distribution of the solid electrolyte used in the oxygen sensor of the present invention.

[Explanation of symbols]

1: Oxygen sensor 2: Sensor board 3: Solid electrolyte 4: Measuring electrode 5: Reference electrode 6: Electrode extraction part 7: Air chamber 8: Air introduction hole 9: Electrode pad 10: heater element substrate 11: Ceramic insulator 12: Heating element 13: Electrode lead-out part 14: Electrode pad 15: Diffusion rate controlling layer

Claims (2)

[Claims] 1. An oxygen sensor in which a porous electrode is formed so as to face both main surfaces of a zirconia solid electrolyte, and the particle size distribution of zirconia crystal particles forming the solid electrolyte has at least two peaks, The first peak is 0.1
5 to 0.25 μm, the second peak is 0.25 to
0.35 μm, and the difference between the two peaks is 0.03
An oxygen sensor having a thickness of about 0.2 μm. 2. An oxygen sensor in which a porous electrode is formed so as to face both main surfaces of a zirconia solid electrolyte, the first zirconia raw material 20 having a specific surface area of 12 to 18 m ² / g.
-80 mass% and a second zirconia raw material having a specific surface area of 3 to 10 m ² / g of 80 to 20 mass% are mixed, and a ceramic green sheet made of a zirconia solid electrolyte is used as a base material on the ceramic green sheet. A method of manufacturing an oxygen sensor, comprising the step of forming a porous electrode on the substrate.