JP3236254B2 - Solid electrolyte type carbon dioxide sensor element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas sensor device using a solid electrolyte for measuring the concentration of carbon dioxide in an atmosphere, which is incorporated in an air purifying facility, an environmental measuring facility, and the like. The present invention relates to a solid oxide carbon dioxide sensor element in which the stability of the carbon dioxide sensor is improved and the stabilization time of the electromotive force is shortened.

[0002]

2. Description of the Related Art In recent years, there has been an increasing interest in environmental issues, and a sensor for measuring and controlling the concentration of carbon dioxide gas released into the atmosphere has attracted attention. Among such sensors, a solid electrolyte type carbon dioxide sensor element utilizing a change in electromotive force of the solid electrolyte is small, simple, and inexpensive, and therefore its practical application is eagerly desired.

At present, a solid electrolyte type carbon dioxide sensor element which is being considered for practical use includes a solid electrolyte layer which is an ion conductor, a working electrode layer containing an electron conductive material and an auxiliary electrode material, and a reference electrode layer containing an electron conductive material. And a heater for heating them.

[0004] This sensor element is usually 100 ° C to 600 ° C.
When it is heated and operated at a constant temperature of ℃ and left in an atmosphere containing carbon dioxide gas, a certain electromotive force according to the carbon dioxide gas concentration is generated between the working electrode layer and the reference electrode layer via the solid electrolyte layer. appear. When the concentration of carbon dioxide in the atmosphere left undisturbed, the dissociation equilibrium reaction between the auxiliary electrode substance and carbon dioxide contained in the working electrode layer progresses until equilibrium is reached, and the mobile ions of the solid electrolyte layer near the working electrode layer Changes occur in concentration.

Since this change in concentration appears as a change in electromotive force, the electromotive force at that time is measured with a voltmeter, and a calibration curve showing the correlation between the electromotive force and the carbon dioxide gas concentration is used. You can know the gas concentration.

In general, NASICON (Na _{1 + A} Zr ₂ Si _A P _3-A) is formed on the solid electrolyte layer of such a carbon dioxide gas sensor.
A cationic conductor such as O ₁₂ , where 0 ≦ A ≦ 3) and β-Al ₂ O ₃ is used.

The electron conductive substance contained in the working electrode layer is a substance necessary for detecting an electromotive force, and a noble metal material having excellent heat resistance and oxidation resistance such as gold and platinum is used.

The auxiliary electrode substance contained in the working electrode layer is a substance capable of causing an equilibrium reaction with carbon dioxide in an atmosphere containing carbon dioxide, and an alkali metal having a dissociation equilibrium with carbon dioxide. Carbonates and alkaline earth metal carbonates are used.

Further, as the electron conductive material contained in the reference electrode layer, the same material as the electron conductive material contained in the working electrode layer is used.

The solid electrolyte type carbon dioxide sensor that operates with the above configuration has an advantage that it can accurately measure the concentration of carbon dioxide contained in the atmosphere and can be made small and inexpensive, so that it has high versatility. Accepted as a sensor element.

[0011]

However, the solid electrolyte type carbon dioxide gas sensor using an alkali metal carbonate or an alkaline earth metal carbonate as the above-mentioned auxiliary electrode substance, in a state where the heating is interrupted and the operation is stopped. If left in an atmosphere with a high moisture concentration, such as a high humidity atmosphere or dew condensation atmosphere, when the operation is started again, the problem that the electromotive force is significantly reduced compared to the value before leaving the system. Had.

Further, while the time from the start of operation to the stabilization of the electromotive force is usually 6 to 8 hours, those which are left unheated in the above atmosphere are 20 to 8 hours.
There was also a problem that it took 40 hours.

These problems are factors that hinder the practical use of the solid electrolyte type carbon dioxide sensor. Therefore,
The electromotive force does not change even if it is left unheated for a long time in an atmosphere with a high moisture concentration such as high humidity or condensation, and the time from the start of operation until the electromotive force is stabilized It has been desired to develop a solid electrolyte type carbon dioxide sensor having a reduced length.

[0014]

The inventor of the present invention has conducted various studies to develop a solid electrolyte type carbon dioxide gas sensor having such characteristics. As a result, the auxiliary electrode material contained in the working electrode layer formed on the surface of the solid electrolyte layer has been obtained. However, by containing a rare earth element carbonate or a rare earth element carbonate and an alkali metal carbonate, the electromotive force can be reduced even when left unheated in an atmosphere having a high moisture concentration such as high humidity or condensation. The inventors have found that a solid electrolyte type carbon dioxide gas sensor having a value that is the same as before leaving the apparatus and that the time from the start of operation to stabilization of the electromotive force is within 2 hours can be obtained, and have come to propose the present invention.

That is, the present invention relates to a solid electrolyte type carbon dioxide sensor element comprising a solid electrolyte layer surface on which a working electrode layer containing an electron conductive material and an auxiliary electrode material and a reference electrode layer containing an electron conductive material are formed. A solid electrolyte type carbon dioxide sensor element, wherein the auxiliary electrode material of the working electrode layer contains a rare earth carbonate or further contains an alkali metal carbonate.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the structure of a solid oxide carbon dioxide sensor element of the present invention will be described in detail.

The auxiliary electrode material is a material capable of causing an equilibrium reaction with carbon dioxide in an atmosphere containing carbon dioxide. In the present invention, it is important that the auxiliary electrode material contains a carbonate of a rare earth element. When the auxiliary electrode material does not contain a carbonate of rare earth element, the value of the electromotive force drops significantly when left in a high-humidity environment compared to before leaving, and from the start of operation until the electromotive force is stabilized Time becomes longer.

As carbonates of rare earth elements, R ₂ O ₂ C
O ₃ , R ₂ O (CO ₃ ) ₂ and its hydrate (R ₂ O (CO ₃ )
₂ · xH ₂ O (x is greater than 0 any number)), R _A O
_L (CO ₃ ) _M (OH) _T (A, L, M, and T are arbitrary integers)
And the like. Here, R is a rare earth element, and La, Ce, P
r, Nd, Yb, Sm, Eu, Gd, Dy, Tm and the like can be mentioned.

Among the rare earth carbonates represented by the above general formula, R ₂ O ₂ CO ₃ , R ₂ O (CO ₃ ) ₂ and R ₂ CO ₅
Is preferred from the viewpoint of shortening the time from the start of operation of the solid electrolyte type carbon dioxide sensor element to the stabilization of the electromotive force. Particularly, the carbonate represented by R ₂ O ₂ CO ₃ is preferable. preferable.

Further, among the carbonates of rare earth elements,
Those in which the rare earth elements are La and Nd are particularly preferable in terms of shortening the time from the start of operation in a high humidity environment to the stabilization of the electromotive force.

In the present invention, the auxiliary electrode material only needs to contain a rare earth element carbonate, and the auxiliary electrode material may consist of only the rare earth element carbonate. In order to prevent a change in the electromotive force value after being left in a high humidity environment, the carbonate of the rare earth element contains 10 watts in the auxiliary electrode material.
t% or more, preferably 15 wt%.
It is preferable that the above is included.

When the auxiliary electrode material contains a compound other than a carbonate of a rare earth element as another auxiliary electrode material, a known auxiliary electrode such as an alkali metal carbonate or an alkaline earth metal carbonate may be used as the other auxiliary electrode material. Substances, and mixtures and solid solutions thereof can be used without any limitation.

Other auxiliary electrode materials include alkali metal carbonates, particularly Li ₂ CO ₃ and Na ₂ C, in view of shortening the time from the start of operation in a high humidity environment to the stabilization of the electromotive force.
It is preferred to use O ₃ . The content of the alkali metal carbonate in the auxiliary electrode material is not particularly limited, but is preferably 0.5 to 3 times in weight ratio to the rare earth carbonate.

As a method for producing an auxiliary electrode material containing a carbonate of a rare earth element, a known method can be used without any particular limitation. As an example of a typical production method, a method of heating a metal carbonate of a rare earth element in the air at 400 to 900 ° C., and a method of heating a metal carbonate of a rare earth element at 400 to 900 ° C.
Heating in a carbon dioxide atmosphere, after mixing a rare earth metal carbonate with another auxiliary electrode material,
A method of heating in the air at a temperature of up to 900 ° C., after mixing a metal carbonate of a rare earth element with another auxiliary electrode material,
A method of heating in a carbon dioxide atmosphere at 900 ° C. and a method of mixing a carbonate of a rare earth element with another auxiliary electrode material can be exemplified.

A general example of the above manufacturing method will be described below. Starting metal carbonate of rare earth element is 400
By heating in the air in a temperature range of up to 900 ° C., an auxiliary electrode substance containing a carbonate of a rare earth element can be obtained. At this time, by adjusting the heating temperature and the heating time, it is possible to obtain an auxiliary electrode material containing the above-mentioned carbonates of various rare earth elements alone or as a mixture of two or more thereof.

Although a part of the rare earth metal carbonate may remain as it is, the metal carbonate acts as an auxiliary electrode material and does not pose any problem for the effect of the present invention. Further, depending on the heating conditions, the metal carbonate of the rare earth element may become an oxide and be mixed, but this does not pose any problem to the manifestation of the effects of the present invention.

The above-mentioned production method is exactly the same as the above-mentioned production method except that a rare earth metal carbonate as a starting material is heated in a carbon dioxide atmosphere.

Next, a general example of the above manufacturing method will be described below. A raw material powder is obtained by mixing a metal carbonate of a rare earth element and another auxiliary electrode material such as an alkali metal carbonate with a ball mill, an automatic mortar or the like to obtain a raw material powder.
By heating in the air at a temperature of ° C., an auxiliary electrode material containing a carbonate of a rare earth element can be obtained. On this occasion,
By adjusting the heating temperature and the heating time, it is possible to obtain an auxiliary electrode material containing the above-mentioned carbonates of various rare earth elements alone or as a mixture of two or more thereof.

When an alkali metal carbonate is used as another auxiliary electrode material, depending on the heating conditions, a carbonate or oxide of a rare earth element and an alkali metal carbonate or an alkali metal released from the alkali metal carbonate form a solid solution or compound. It may be formed, but does not pose any problem to the manifestation of the effects of the present invention.

The above production method is exactly the same as the above production method except that a mixed powder of a rare earth metal carbonate and another auxiliary electrode material such as an alkali metal carbonate is heated in a carbon dioxide atmosphere. It is.

In the above production method, a rare earth element carbonate and another auxiliary electrode substance such as an alkali metal carbonate obtained by the above production method are mixed with a ball mill.
By mixing in an automatic mortar or the like, an auxiliary electrode material containing a carbonate of a rare earth element can be obtained.

In the present invention, the electron conductive material contained in the working electrode layer is a substance necessary for outputting an electromotive force of the sensor element, like the electron conductive material contained in the reference electrode layer described later, and is known in the art. Material is used without restriction. For example, noble metal elements such as platinum, gold, palladium, and silver and alloys thereof, or a mixture of two or more of the above noble metal elements are employed. In particular, platinum, gold, and mixtures and alloys thereof are resistant. It is suitable because of its excellent corrosiveness.

In the present invention, the structure of the working electrode layer including the electron conductive material and the auxiliary electrode material is not particularly limited. A typical structure is, for example, a structure in which an electron conductive material and an auxiliary electrode material are layered on the surface of a fixed electrolyte layer, a structure in which an auxiliary electrode material is dispersed in an electron conductive material of a working electrode layer, and a structure in which an electron conductive material is present. Structure in which part or all of the auxiliary electrode material layer formed on the surface of the solid electrolyte layer is coated, structure in which the auxiliary electrode material covers part or all of the electron conductive material layer formed on the solid electrolyte layer surface, etc. In particular, a structure in which the auxiliary electrode material is dispersed in the electron conductive material is preferable because the working electrode layer can be easily formed.

The content ratio of the electron conductive material and the auxiliary electrode material in the working electrode layer is not particularly limited, but the weight ratio of the auxiliary electrode material to the working electrode layer is 5% to 50%.
It is preferable that it is included because it is easy to stably output the electromotive force of the sensor element.

As a method for forming the working electrode layer, a known method is used without any particular limitation. For example, the method as described in the method for manufacturing the working electrode layer described above can be used.

In forming the working electrode layer,
When a method of baking paste by screen printing or the like is adopted, substances such as glass and ceramics derived from a binder may remain in the baked working electrode layer, but even if these substances are mixed in the working electrode layer. ,
The effect of the electron conductive material and the auxiliary electrode material remains unchanged.

The thickness of the working electrode layer is not particularly limited.
Generally, it is adopted from the range of 0.001 to 0.03 mm.

In the present invention, the electron conductive material contained in the reference electrode layer is a substance necessary for outputting an electromotive force of the sensor element, similarly to the above-described electron conductive material contained in the working electrode layer, and is known in the art. Material is used without restriction. For example, noble metal elements such as platinum, gold, palladium, and silver and alloys thereof, or a mixture of two or more of the above noble metal elements are employed. In particular, platinum, gold, and mixtures and alloys thereof are resistant. It is suitable because of its excellent corrosiveness.

As a method for forming the above-mentioned reference electrode layer, a known method is used without any particular limitation. For example, a method in which the above-described electron conductive material is used alone or mixed and then kneaded with a solvent and a binder to form a paste, and the paste is printed on a solid electrolyte surface by a screen printing method or the like and baked. For example, a method of forming by a thin film forming technique such as is preferred. When a method of baking the paste by screen printing or the like is employed during the formation of the reference electrode layer, substances such as glass and ceramics derived from a binder may remain on the reference electrode layer. Even if the substance is mixed in the reference electrode layer, the function of the reference electrode layer is not impaired.

Although the thickness of the reference electrode layer is not particularly limited,
Generally, it is adopted from the range of 0.001 to 0.03 mm.

In the present invention, the arrangement of the working electrode layer and the reference electrode layer is not particularly limited as long as the working electrode layer and the reference electrode layer are in contact with the solid electrolyte layer. For example, a structure in which a working electrode layer is formed on one surface of a solid electrolyte layer and a reference electrode layer is formed on the other surface, and both the working electrode layer and the reference electrode layer are fixed on one surface of the solid electrolyte layer. May have a structure formed at a distance of.

In the present invention, a known solid electrolyte is used for the solid electrolyte layer without any limitation. For example, N
ASICON, β-Al ₂ O _{3 and the} like.

As a method for forming the solid electrolyte layer, a known method is employed without any particular limitation. As a typical forming method,
After sintering the solid electrolyte synthesis raw material, molding and heating, a method of sintering after molding the solid electrolyte synthesis raw material, and kneading the solid electrolyte synthesis raw material with a solvent and a binder to form a paste, A method in which the paste is printed on a ceramic or glass substrate by a screen printing method or the like and printed is used.

Although the thickness of the solid electrolyte layer is not particularly limited, it is generally adopted in the range of 0.02 mm to 2.0 mm.

The solid electrolyte type carbon dioxide sensor element is usually used by heating to a constant temperature of 100 ° C. to 600 ° C. in order to cause a dissociation equilibrium reaction between the auxiliary electrode substance and carbon dioxide. As a method for heating the sensor element, heating from a heat source external to the sensor element may be used, or a ceramic or glass substrate on which a heater is formed is joined to the sensor element, and a DC or AC voltage is applied to the heater. May be heated. The mounting position of the heater joined to the sensor element is not particularly limited as long as it does not hinder the operation of the sensor element, such as on the reference electrode layer.

[0046]

According to the solid electrolyte type carbon dioxide sensor element of the present invention, by using a carbonate of a rare earth element as an auxiliary electrode material of the working electrode layer, the solid oxide carbon dioxide sensor element can be exposed to dew condensation or high humidity atmosphere in a non-heated state for a long time. The value of the electromotive force remains unchanged even before being left, and the time from the start of operation until the electromotive force is stabilized can be made within 2 hours. Further, when a material containing a carbonate of a rare earth element and an alkali metal carbonate is used, it can be stabilized within one hour. Such a stabilization time is shorter than the normal stabilization time of 6 to 8 hours.

Therefore, the present invention has great technical significance in that carbon dioxide can be measured reliably and quickly over a long period of time under any environment.

[0048]

EXAMPLES The present invention will be described specifically with reference to the following examples, but the present invention is not limited to these examples.

(1) Water resistance test Immediately after the solid electrolyte type carbon dioxide sensor elements of Examples and Comparative Examples were prepared, they were placed in a chamber in which the concentration of carbon dioxide gas could be freely controlled, and a DC voltage was applied from a power source to a heater. The device was heated to 450 ° C.

With the temperature of the sensor element maintained at 450 ° C., the concentrations of carbon dioxide in the chamber were set to 350 ppm and 1000 ppm, and the electromotive force at each concentration was measured and used as the initial electromotive force. 350 ppm
And the difference between the electromotive force at 1000 ppm and the electromotive force at 1000 ppm was determined as the initial sensitivity.

After measuring the initial electromotive force and sensitivity, the sensor element was taken out of the chamber, placed in a thermostat maintained at a temperature of 60 ° C. and a humidity of 90%, and left standing for 7 days without heating. did.

After the standing, it was taken out of the thermostat, and the electromotive force and the sensitivity were measured in the same manner as the method for measuring the initial electromotive force and the sensitivity, which were defined as the electromotive force and the sensitivity after the water resistance test.

The difference between the electromotive force and the sensitivity at the initial stage after the water resistance test and the difference between the sensitivities were determined, and changes in the electromotive force and the sensitivity after being left for a long time in an atmosphere of dew condensation or high humidity without heating were observed. .

(2) Measurement of electromotive force stabilization time The sensor element was placed in a constant temperature bath maintained at a temperature of 60 ° C. and a humidity of 90%, and left standing for 7 days without heating.

Immediately after the sensor element was taken out of the thermostat, the sensor element was placed in a chamber in which the concentration of carbon dioxide was maintained at 350 ppm, and a DC voltage was applied from a power source to a heater to heat the sensor element to 450 ° C. The time from the start of heating until the value of the electromotive force of the sensor element was stabilized in the range of ± 4 mV was measured, and this was defined as the stabilization time of the sensor element.

Examples 1 to 4 Elements having a cross-sectional structure as shown in FIG. 1 were manufactured as solid electrolyte type carbon dioxide sensors. In this solid electrolyte type gas sensor element, a working electrode layer 1 is formed on one surface of a solid electrolyte layer 2 and a reference electrode layer 3 is formed on the other surface, and a ceramic plate 4 is bonded on the reference electrode layer 3 with an adhesive 5. ing. Further, a heater 6 is formed on the surface of the ceramic plate 4 opposite to the surface to which the reference electrode layer 3 is bonded, and receives power from a power supply 7. Further, lead wires are drawn out from the working electrode layer 1 and the reference electrode layer 3, and connected to a voltmeter 8 to measure the electromotive force.

The solid electrolyte powder for forming the solid electrolyte layer is formed by converting zirconium silicate and sodium phosphate to Na
₃ Zr ₂ SiPO ₁₂ was mixed to give a composition of 1100
It was obtained by baking for 6 hours in an air atmosphere at a temperature of ° C.

The solid electrolyte layer 2 was formed into a disk-shaped pellet by uniaxially molding the above-mentioned solid electrolyte powder and then sintering at 1200 ° C. in an air atmosphere for 10 hours.

The auxiliary electrode material containing the rare earth element carbonate is La ₂ (CO ₃ ) _3, which is a metal carbonate of the rare earth element.
Alternatively, it was obtained by firing Nd ₂ (CO ₃ ) ₃ in the air at 700 ° C. for 30 minutes. Table 1 shows the composition of the obtained auxiliary electrode material by X-ray diffraction and X-ray fluorescence analysis.

The working electrode layer was kneaded with terpineol in which 5% by weight of ethylcellulose was dissolved, and a gold powder as an electron conductive material and an auxiliary electrode material at a ratio shown in Table 1 to form a paste. One side was formed by screen printing, drying, and baking in the air at 630 ° C. for 30 minutes. Thus, a working electrode layer having a thickness of 0.015 mm was obtained.

The reference electrode layer is formed by kneading gold powder as an electron conductive material and terpineol in which 5% by weight of ethyl cellulose is dissolved to form a paste, which is the opposite of the solid electrolyte layer opposite to the surface on which the working electrode layer is formed. It was formed by screen printing, drying, and baking for 30 minutes in the air at 650 ° C. on the surface. Thus, a reference electrode layer having a thickness of 0.015 mm was obtained.

On the above-mentioned reference electrode layer, an alumina substrate mounted with a platinum heater formed by a screen printing method using a commercially available platinum paste is made of glass so that the surface on which the heater is not formed becomes a bonding surface. Bonded with adhesive.

A water resistance test and a measurement of an electromotive force stabilization time were performed on the solid electrolyte type carbon dioxide sensor element manufactured by the above method.

Table 2 shows the results.

Examples 5 to 10 La ₂ (CO ₃ ) ₃ or Nd ₂ (CO ₃ ) ₃ and Li ₂ CO ₃ or Na ₂ CO ₃ were mixed and pulverized in an automatic mortar.
Except for using an auxiliary electrode substance containing a carbonate of a rare earth element obtained by baking for 30 minutes in the atmosphere of 00 ° C.,
A solid electrolyte type carbon dioxide sensor element was manufactured in the same manner as in Example 1. Table 1 shows the composition of the obtained auxiliary electrode material by X-ray diffraction and X-ray fluorescence analysis.

A water resistance test and a measurement of an electromotive force stabilization time were performed on the manufactured sensor element, and the results are shown in Table 2.

Example 11 La ₂ (CO ₃ ) ₃ and Nd ₂ (CO ₃ ) ₃ were mixed and pulverized in an automatic mortar, and calcined in the air at 700 ° C. for 30 minutes to effect carbonation of rare earth elements. A solid electrolyte type carbon dioxide sensor element was manufactured in the same manner as in Example 1 except that an auxiliary electrode material containing a substance was used. Table 1 shows the composition of the obtained auxiliary electrode material by X-ray diffraction and X-ray fluorescence analysis.

A water resistance test and a measurement of an electromotive force stabilization time were performed on the manufactured sensor element, and the results are shown in Table 2.

Example 12 The same as Example 1 except that an auxiliary electrode material containing a carbonate of rare earth element obtained by calcining La ₂ (CO ₃ ) ₃ in air at 650 ° C. for 10 minutes was used. A solid electrolyte type carbon dioxide sensor element was fabricated by a simple method. Table 1 shows the composition of the obtained auxiliary electrode material by X-ray diffraction and X-ray fluorescence analysis.
It was shown to.

A water resistance test and a measurement of an electromotive force stabilization time were performed on the manufactured sensor element, and the results are shown in Table 2.

Example 13 The same procedure as in Example 1 was carried out except that an auxiliary electrode material containing a carbonate of a rare earth element obtained by calcining La ₂ (CO ₃ ) ₃ in air at 900 ° C. for 20 minutes was used. A solid electrolyte type carbon dioxide sensor element was fabricated by a simple method. Table 1 shows the composition of the obtained auxiliary electrode material by X-ray diffraction and X-ray fluorescence analysis.
It was shown to.

A water resistance test and measurement of an electromotive force stabilization time were performed on the manufactured sensor element, and the results are shown in Table 2.

Example 14 La ₂ (CO ₃ ) ₃ and Li ₂ CO ₃ were mixed and pulverized in an automatic mortar and baked for 10 minutes in the air at 650 ° C. to obtain a carbonate of rare earth element. A solid electrolyte type carbon dioxide sensor element was produced in the same manner as in Example 1 except that an auxiliary electrode material containing was used. X of the obtained auxiliary electrode material
Table 1 shows the compositions obtained by X-ray diffraction and X-ray fluorescence analysis.

A water resistance test and measurement of an electromotive force stabilization time were performed on the manufactured sensor element, and the results are shown in Table 2.

Example 15 La ₂ (CO ₃ ) ₃ and Li ₂ CO ₃ were mixed and pulverized in an automatic mortar and baked in the air at 900 ° C. for 20 minutes to obtain a carbonate of rare earth element. A solid electrolyte type carbon dioxide sensor element was produced in the same manner as in Example 1 except that an auxiliary electrode material containing was used. X of the obtained auxiliary electrode material
Table 1 shows the compositions obtained by X-ray diffraction and X-ray fluorescence analysis.

A water resistance test and measurement of an electromotive force stabilization time were performed on the manufactured sensor element, and the results are shown in Table 2.

Comparative Examples 1 to 5 In the solid electrolyte type carbon dioxide sensor elements of Comparative Examples 1 to 5, all parts except the working electrode layer were manufactured in the same manner as in Examples 1 to 15.

The working electrode layers of Comparative Examples 1 to 5 were prepared by kneading terpineol in which 5% by weight of ethylcellulose was dissolved with gold powder as an electron conductive material and auxiliary electrode materials shown in Table 1 to obtain a paste. One side of the electrolyte layer was formed by screen printing, drying and baking for 30 minutes in the air at 650 ° C.

The Li ₂ CO ₃ contained in Comparative Examples 1 to 5
For Na ₂ CO ₃ , the reagent raw materials were used as they were.

A water resistance test and measurement of an electromotive force stabilization time were performed on the manufactured sensor element, and the results are shown in Table 2.

[0081]

[Table 1]

[0082]

[Table 2]

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a typical embodiment of a solid oxide carbon dioxide sensor element.

[Explanation of symbols]

 1. Working electrode layer 2. Solid electrolyte layer 3. 3. Reference electrode layer Ceramic plate 5. Adhesive 6. Heater 7. Power supply 8. voltmeter

Claims (2)

(57) [Claims] 1. A solid electrolyte type carbon dioxide sensor element comprising a working electrode layer containing an electron conducting material and an auxiliary electrode material and a reference electrode layer containing an electron conducting material formed on the surface of a solid electrolyte layer. A solid electrolyte type carbon dioxide sensor element, wherein the auxiliary electrode material contains a carbonate of a rare earth element. 2. The solid oxide carbon dioxide sensor element according to claim 1, wherein the auxiliary electrode material contains a carbonate of a rare earth element and an alkali metal carbonate.