JPH09264866A - Carbon dioxide sensor and manufacturing method thereof - Google Patents

Abstract

(57) Abstract: An object of the present invention is to reduce the sensitivity deterioration of a carbon dioxide gas sensor composed of a carbonate, a non-composite oxide, and a perovskite type compound, increase the strength, and downsize the entire sensor. SOLUTION: Ceramics containing one or more of carbonate, complex metal oxide, and non-complex metal oxide are formed as a carbon dioxide detecting body 4 on the surface of a substrate 2 heated by a heater 1. Since the silica gel is added by the sol, when the silica gel is added, the silica sol solution and the carbon dioxide gas detecting body 4 are added.
If you use a solution mixed with the solution of the metal salt of the component of
Characteristic deterioration due to silica gel can be suppressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thick film type carbon dioxide gas sensor for detecting the concentration of carbon dioxide gas comprising a ceramic compound of carbonate, composite metal oxide, and non-composite metal oxide, and a method for producing the same. .

[0002]

2. Description of the Related Art In recent years, carbon dioxide gas sensors for detecting carbon dioxide concentration have been used in environmental measurement, horticulture, production equipment and the like. As a carbon dioxide gas sensor, a measuring method using a detection method using infrared rays, a method using an electrolytic solution, and a method using heat conduction is commercially available, but it is large and the manufacturing cost is high. For this reason, other methods are being considered,
A method of using an alkali ion conductive solid electrolyte such as NASICON with NaCO ₃ as an electrode, a method of using a Li ion conductor, a method of using a CO ₃ ²⁻ ion conductor such as K ₂ CO ₃ and a method of using hydroxyapatite Methods such as using resistance have been studied. In addition, a carbon dioxide gas sensor that detects the carbon dioxide concentration by changing the electrical characteristics by a reversible carbonate formation reaction between a non-composite oxide and carbon dioxide has attracted attention because it can downsize the device. JP-A-4-2454
No. 8 discloses "a carbon dioxide gas sensor using a change in capacitance of a mixture of a perovskite type metal oxide and a non-composite type metal oxide which is an oxide composed of one kind of metal." No. 6-182261, "Carbon dioxide gas sensor using a mixture of non-composite metal oxides" is disclosed in JP-A-6-8.
8800 discloses "a carbon dioxide gas sensor using a rare earth oxide which is one of non-composite oxides." To improve the detection ability of these carbon dioxide gas sensors
No. 42180 proposes addition of a noble metal element such as Ag and a transition metal element, Japanese Patent Application No. 6-313410 proposes addition of BaO, and Japanese Patent Application No. 7-165053 proposes addition of carbonate.

[0003]

However, the carbon dioxide gas sensor using the above-mentioned conventional carbonates, non-composite oxides, and perovskite-type compounds deteriorates in the heat treatment temperature condition where the strength is sufficient, and the sensitivity is expressed. The heat treatment at temperature has a problem that the strength of the ceramic is weak and cannot be put to practical use, and the size cannot be reduced.

An object of the present invention is to solve the above problems and to suppress the deterioration of the sensitivity of a carbon dioxide gas sensor composed of a carbonate, a non-composite oxide and a perovskite type compound to increase the strength and to downsize the entire sensor.

[0005]

In order to solve this problem, the present invention prepares a paste of a carbonate, a non-composite metal oxide or a perovskite metal oxide on a substrate having a heater portion on the front surface or the back surface. The paste and the electrode portion are screen-printed so as to have a predetermined structure and heat-treated to form a small carbon dioxide gas sensor. The raw material used for the paste should have a small particle size. Further, by mixing a silica sol solution with this paste to deposit silica gel having high strength and binding the raw materials, the strength can be increased even under a low temperature heat treatment condition. When the sensitivity does not appear due to the addition of the silica sol solution, the sensitivity is exhibited by using a sol solution containing silica mixed with a solution containing one or more metal salts of the constituents. When the sensitivity is greatly deteriorated, the carbon dioxide sensor is prepared without mixing the sol solution containing silica, and then the carbon dioxide sensor is immersed in the sol solution solution containing silica to add the sol solution containing silica to improve the strength.

Further, a sol solution containing silica and a solution of a metal salt of a ceramic component of the detection body are mixed and made into a paste to be screen-printed to form a detection section body to improve the strength.

According to the present invention, it is possible to suppress deterioration of sensitivity of a carbon dioxide gas sensor made of a carbonate, a non-composite oxide, and a perovskite type compound, increase the strength, and downsize the entire sensor.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The invention according to claim 1 of the present invention comprises a carbonate, a complex metal oxide,
A ceramic layer containing at least one non-composite metal oxide is formed, a pair of electrodes is formed on the ceramic layer, and the ceramic layer and the electrode part are formed on a substrate heated by a heater. The carbon dioxide gas sensor is characterized in that it has a thin shape and a small size, and at the same time, it has an effect that productivity can be improved and manufacturing cost can be reduced because it can be produced by screen printing.

The invention according to claim 2 of the present invention is characterized in that a ceramic is formed as a carbon dioxide detection body on the surface of a substrate heated by a heater, and the carbon dioxide detection body contains silica gel. The carbon dioxide sensor according to 1, wherein the silica sol solution added to the ceramic is silica gel, which has the effect of increasing the strength of the carbon dioxide detecting body.

The invention according to claim 3 of the present invention is the carbon dioxide gas sensor according to any one of claims 1 and 2, characterized in that an alkali metal carbonate is contained as the carbonate. This has the effect that the sensor can be efficiently manufactured.

The invention according to claim 4 of the present invention is the carbon dioxide gas sensor according to any one of claims 1 and 2, characterized in that the carbonate contains an alkaline earth metal carbonate. It has an effect that a small sensor having a large size can be efficiently manufactured.

The invention according to claim 5 of the present invention comprises lithium carbonate as a carbonate.
The carbon dioxide sensor according to any one of 2 and 3 has an effect that a small sensor having high sensitivity can be efficiently produced.

The invention according to claim 6 of the present invention comprises barium carbonate as a carbonate.
The carbon dioxide sensor according to any one of 2, 4 and 4 has an effect that a small sensor having high sensitivity can be efficiently produced.

The invention according to claim 7 of the present invention is the carbon dioxide gas sensor according to any one of claims 1 and 2, characterized in that it contains a perovskite type oxide as the composite metal oxide, and is small in size with high sensitivity. This has the effect that the sensor can be efficiently manufactured.

The invention according to claim 8 of the present invention is the carbon dioxide sensor according to any one of claims 1, 2, and 7, characterized in that barium titanate is contained as a composite metal oxide, and it has high sensitivity. It has an effect that a small sensor can be efficiently manufactured.

The invention according to claim 9 of the present invention is one of cerium oxide and copper oxide as the non-composite metal oxide.
3. The method according to claim 1, further comprising one or more species.
The carbon dioxide gas sensor described above has an effect that a small sensor having high sensitivity can be efficiently produced.

The invention according to claim 10 of the present invention is the carbon dioxide sensor according to claim 9, characterized in that the average particle diameter of the copper oxide is 1 μm or less. It has the effect that it can be improved.

According to an eleventh aspect of the present invention, an electrode is formed on the surface of a substrate heated by a heater, and a ceramic layer of a carbon dioxide detecting body is formed on the electrode.
A pair of electrodes is formed on the ceramic layer, and the pair of electrodes is formed on the ceramic layer.
The carbon dioxide sensor according to any one of 8, 9, 10
Since the electrodes face each other, the area of the electrodes is increased, and a large capacitance can be obtained.

According to a twelfth aspect of the present invention, the ceramic layer of the carbon dioxide detecting body is formed on the surface of the substrate heated by the heater, and the pair of electrodes is formed on the ceramic layer. Claims 1 and 2, characterized in that
The carbon dioxide gas sensor according to any one of 3, 4, 5, 6, 7, 8, 9, and 10 has an effect that the sensor can be efficiently prepared by forming the electrode only on the surface.

According to a thirteenth aspect of the present invention, the ceramic layer of the carbon dioxide detecting body is formed on the surface of the substrate heated by the heater, and between the substrate and the ceramic layer,
A pair of electrodes are formed, and any one of claims 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 is formed.
The carbon dioxide sensor described above has an effect that the deterioration of the electrode is suppressed by covering the electrode portion and that the sensor can be efficiently manufactured.

According to a fourteenth aspect of the present invention, the ceramic layer of the carbon dioxide sensing body is formed on the surface of the substrate heated by the heater, and one or more electrodes are provided on one side of the ceramic layer, and 7. One or more electrodes are formed on the surface,
The carbon dioxide gas sensor according to any one of 7, 8, 9, 10 has an effect that two or more signals can be taken out and an abnormality of the sensor can be detected early by comparing these signals.

A fifteenth aspect of the present invention is a carbon dioxide gas sensor characterized in that a heater layer is formed on the surface of the substrate opposite to the ceramic layer, and warms the entire back surface of the detection portion. This has the effect of improving the temperature unevenness of the detection unit and improving the sensitivity variation.

According to a sixteenth aspect of the present invention, there is provided a carbon dioxide gas sensor characterized in that a heater layer and a ceramic layer of a carbon dioxide gas detection body are formed on the surface of the substrate, and one side is screen-printed. The gathering of the parts has an effect that the sensor can be efficiently manufactured.

The invention according to claim 17 of the present invention is characterized in that the heater layer, the carbon dioxide gas detecting main body, and the electrode layer formed on the substrate are formed by screen printing using a paste of each material. It is a method of manufacturing a carbon dioxide sensor, and has an effect that a small sensor can be efficiently produced by screen printing.

In the eighteenth aspect of the present invention, the heat treatment temperature at the time of manufacturing the carbon dioxide sensor comprising the heater layer formed on the substrate, the carbon dioxide sensing body, and the electrode layer is set to 90.
This is a method of manufacturing a carbon dioxide gas sensor, which is characterized in that the temperature is 0 ° C. or lower, and the sensitivity of the sensor can be prevented from deteriorating by making it at a low temperature.

According to a nineteenth aspect of the present invention, a sol solution of silica is mixed with a ceramic used for a carbon dioxide sensing body formed on the substrate to prepare a paste,
This is a method of manufacturing a carbon dioxide gas sensor characterized by screen-printing thereafter, and has the effect of increasing the strength of the sensor detection unit and being able to screen-print to efficiently produce a small sensor.

According to a twentieth aspect of the present invention, a carbon dioxide gas sensor comprising a heater layer formed on the substrate, a carbon dioxide gas sensing body, and an electrode layer is prepared, dipped in a silica sol solution, and dried. It is a method of manufacturing a carbon dioxide gas sensor characterized by heat treatment, and has an effect that the strength of the sensor detection portion can be improved without degrading the sensor sensitivity.

According to a twenty-first aspect of the present invention, the silica sol solution according to the nineteenth and twentieth aspects is a sol of silica in which one or more metal salts of the material used for the carbon dioxide sensing body are dissolved. A method of manufacturing a carbon dioxide gas sensor, characterized by using a solution containing, to prevent deterioration of sensor sensitivity due to mixing of sol solution of silica by mixing sensor sol component of sensor with silica sol in the solution. You can

According to a twenty-second aspect of the present invention, a sol solution containing silica in which a metal salt of a material used for a carbon dioxide detecting body is dissolved is made into a paste and screen-printed on a substrate. It is a characteristic carbon dioxide sensor manufacturing method, in which the viscosity of a solution in which all of the sensor detection component components are mixed with a silica sol solution is adjusted to a paste, and the strength of the carbon dioxide detection body is improved by heat treatment after screen printing. improves. Further, it has the effect that the characteristics can be improved by making the components fine.

Embodiments of the present invention will be described below with reference to FIGS. (Embodiment 1) FIG. 1 is a sectional view of a carbon dioxide sensor according to a first embodiment of the present invention, showing an electrode according to claim 11. Since the electrode 3 and the electrode 5 face each other, the area is the largest and the detection signal can be large.

There is a heater 1 on the back surface of the ceramic substrate 2 having high strength, and the entire substrate 2 can be heated by passing an electric current. When the heater 1 is formed on the same surface as the carbon dioxide detection body 4, the heater 1 is formed on a side slightly apart from the carbon dioxide detection body 4, and there is a temperature difference between a portion near the heater 1 and a portion far from the carbon dioxide detection body 4. Although it occurs, the work on only one side is performed, and the efficiency of producing the carbon dioxide sensor is improved.

The carbon dioxide detecting body 4 is sandwiched between the electrodes 3 and 5, and terminals are connected to the electrodes 3 and 5 to draw out a signal and measure the carbon dioxide concentration.

By forming the heater 1, the electrodes 3 and 5, and the carbon dioxide detecting body 4 by screen printing, a small carbon dioxide sensor can be efficiently produced.

The carbon dioxide detecting body 4 is made of ceramics containing at least one of carbonate, complex metal oxide, and non-compound metal oxide, and particularly Li ₂ CO ₃ , BaC.
The sensitivity of the carbon dioxide sensor in which O ₃ , CeO ₂ , and CuO are mixed is excellent. Sensitivity is deteriorated and strength is not improved simply by pasting and screen-printing these constituent components. Sensitivity deterioration is thought to be due to the fact that the particles do not come into contact with pressure in screen printing and the electrical contact is large due to the loose contact between particles.
By reducing the particle size of the component and increasing the contact with other components, it is possible to reduce the electric resistance and suppress the sensitivity deterioration. The smaller the particle size of the component of the carbon dioxide detecting body 4, the more the contact portion of each component increases and the better the sensitivity. Further, strength can be improved by using a sol solution of silica. When the sol solution of silica is dried, it becomes silica gel even at room temperature and has an adhesive force. The carbon dioxide sensor of the present embodiment loses sensitivity when heat-treated at high temperature, but the strength can be improved even if heat-treated at low temperature by making silica sol into silica gel and adhering each component. However, silica gel has a strong insulating property, and as the amount increases, the strength increases but the sensitivity deteriorates. Therefore, a part of the constituent components of the carbon dioxide detection body 4 is mixed with the silica sol solution to modify the silica sol solution, and the constituent components are deposited on or inside the silica gel to suppress the insulating property and to improve the sensitivity. Deterioration can be suppressed. Also, a sol solution of silica,
Alternatively, the strength can be improved without breaking the contact between the particles by immersing the sensor in a sol solution of silica in which a part of the constituent components of the carbon dioxide detecting main body 4 is mixed, and drying and then heat-treating. Further, the strength can be improved by preparing a paste containing the sol solution containing silica and the constituents of the carbon dioxide gas detecting main body 4 and by screen printing to form the carbon dioxide gas detecting main body 4.

(Embodiment 2) FIG. 2 is a sectional view of a carbon dioxide sensor according to a second embodiment of the present invention, showing an electrode according to claim 12.

In FIG. 2, the electrodes 3 and 5 are formed on the carbon dioxide detecting body 4, and the work efficiency at the time of screen printing is improved. Since the detection signal is mainly based on the sensing of carbon dioxide on the surface of the carbon dioxide sensing body 4, the response is improved. Since a large signal can be obtained, it is preferable that the electrodes 3 and 5 have a comb shape.

(Embodiment 3) FIG. 3 is a sectional view of a carbon dioxide sensor according to a third embodiment of the present invention, showing an electrode according to claim 13.

In FIG. 3, electrodes 3 and 5 are formed between the substrate 2 and the carbon dioxide detection body 4, and the electrodes 2 and 5 are protected by the substrate 2 and the carbon dioxide detection body 4. Therefore, the deterioration of the electrodes 3 and 5 can be suppressed.

(Embodiment 4) FIG. 4 is a sectional view of a carbon dioxide sensor according to a fourth embodiment of the present invention, showing an electrode according to claim 14.

FIG. 4 shows that two or more electrodes 5 and 6 are formed on the opposite surface of the electrode 3 formed on one side of the carbon dioxide detecting body 4, and the combination of the electrodes 3 and 5 and the electrodes 3 and 6. The two signals can be extracted, and by comparing these signals, the abnormality of the electrodes 3, 5 and 6 and the abnormality of the carbon dioxide detecting body 4 can be discriminated, and the reliability is increased. It is the same even if the positions of the electrodes are changed.

According to the present invention, since the carbon dioxide detecting body 4 is screen-printed on the substrate 2 having high strength, it can be put to practical use even when the strength of the carbon dioxide detecting body 4 is insufficient. The sensitivity of the carbon dioxide sensor produced by screen printing is deteriorated as compared with that of the carbon dioxide sensor produced in a disk shape. This carbon dioxide detection body 4
When the raw material particle size of the component is smaller, the mixing is better and the contact portion of each component increases, so that the deterioration of the sensitivity can be suppressed. Also, by mixing a sol solution containing silica with the paste of the component of the carbon dioxide sensing body 4, the adhesive strength is improved by gelation of silica sol even under low temperature heat treatment conditions. The sensitivity of the carbon dioxide sensor may deteriorate due to the insulating property of silica gel. However, by mixing a solution containing one or more of the components of the carbon dioxide sensing main body 4 in this sol solution of silica, the carbon dioxide on the surface or inside of the silica gel is reduced. The components of the gas detection body 4 are deposited to weaken the insulation and suppress sensitivity deterioration. The same effect can be obtained by immersing the prepared carbon dioxide gas sensor in a sol solution of silica or a mixed solution of silica sol and a detection component and adding silica instead of mixing with the paste. In this case, the heat treatment of the carbon dioxide detection body 4 has been completed, and silica does not enter the sintered portion of each component and is deposited around it, so that the sensitivity is less deteriorated.

Further, by mixing the silica sol solution and the solution of the metal salt of the ceramic constituent component of the carbon dioxide detecting body 4 to prepare the carbon dioxide detecting body 4, the constituent components can be made into fine particles and the characteristics can be improved. The strength can be improved by silica gel.

[0043]

Next, specific examples of the present invention will be described.

Example 1 Commercially available BaCO ₃ , CeO ₂ and CuO were weighed in a molar ratio of 6:63:31, mixed and pulverized in a mortar, and then 7 g of this mixed raw material and 30
% Sol solution containing 0.5% silica, terpineol 1.
2 g, 1.2 g of a vehicle prepared by mixing terpineol and ethyl cellulose in a ratio of 1: 1 and 0.2 g of a dispersant are mixed to prepare a paste for a carbon dioxide detecting body. Since the contact portion of the particles affects the characteristics, it is desirable that the material particle size of the carbon dioxide sensing body is small.

A heater is prepared on a substrate of alumina ceramic having a size of 2 mm × 3 mm × 0.3 mm. The heater is made by screen printing Pt or RuO ₂ paste. Although it may be created on either the front or back surface of the ceramic substrate, if it is created on the front surface, screen printing will be done only on the same surface, which improves workability. Temperature variations in the gas detection body occur. On the other hand, when the heater is formed on the back surface, workability is deteriorated, but since the heater can be uniformly formed on the back surface, the temperature distribution is improved. Since the carbon dioxide sensor body has a heater, the carbon dioxide sensor can be made smaller and the amount of electricity required for heating can be reduced. It is sufficient that the substrate has high strength and can withstand the heat treatment temperature at the time of producing the carbon dioxide sensor and the operating temperature of the carbon dioxide sensor. If it is electrically conductive, insulation treatment is required.

A Pt paste is screen-printed on this alumina ceramic substrate and heat-treated to form an electrode. A paste for a carbon dioxide detection body is screen-printed on the Pt electrode, dried, and then heat-treated at 800 ° C. for 5 hours.
Then, Pt east is screen-printed on the carbon dioxide detection body and heat-treated to form an electrode, and a carbon dioxide sensor is prepared. The two electrodes of Pt are opposed to each other with the ceramic layer of the carbon dioxide sensing body interposed therebetween. The electrode is A
It is sufficient that u, Ag, RuO ₂ , copper oxide or the like is made into a paste and can be screen-printed, and has a low resistance at the operating temperature of the carbon dioxide sensor. Although the electrode described above has the shape shown in FIG. 1, the electrode may have the shape shown in FIGS. 2 to 4.

An electric current was passed through the heater of this carbon dioxide sensor to adjust the temperature of the carbon dioxide detecting body to 550 ° C., and the sensitivity to carbon dioxide was measured. The sensitivity was measured by a two-terminal method using an impedance analyzer 4192A manufactured by YHP, and dry air and carbon dioxide gas diluted with dry air were used as sample gas.

The state of detection of carbon dioxide gas is based on the capacity value (C ₀ ) of the sample heated to the measurement temperature, which was measured in the state where air was introduced, and the air adjusted to a carbon dioxide concentration of 2% was introduced. It can be grasped by the change of the capacitance value (C _2% ) when measured by. The sensitivity is defined by the following formula.

Sensitivity = | 10 × Log (C _2% / C ₀ ) | [dB] When the sensitivity is 0, it means that the capacitance value does not change with the increase of the carbon dioxide concentration, and the carbon dioxide is detected. You're not doing it.

For sensitivity comparison, a mixed raw material having the same composition was molded into a disk shape having a diameter of 10 mm and a thickness of 0.4 mm,
It baked at 800 degreeC in the electric furnace for 5 hours. A Pt electrode was attached to the obtained sample to make a carbon dioxide sensor.

This disk-shaped carbon dioxide sensor has weak strength and is easily cracked. When baked at 1000 ° C. or higher, the strength is sufficient but sensitivity is not expressed, and heat treatment at 900 ° C. or lower is desirable. On the other hand, by subjecting a substrate with high strength to screen printing to form a thick film, most of the strength depends on the substrate, so that it has strength even when heat-treated at a temperature of 900 ° C. or less at which sensitivity is expressed, and should be put to practical use. Will be able to. Further, by adding a silica sol solution to the paste, the strength of the carbon dioxide detecting body is improved, and the reliability is further increased.

Similarly, the sensitivity of the samples prepared by changing the addition amount of the silica sol solution and the samples prepared by changing the components is shown in (Table 1).

Further, the sensitivity of the sensor shown in Example 2 to be described later in which the silica sol solution and the component of the carbon dioxide gas detecting main body were mixed with 1% of silica was 4.1, and the sensitivity of the sensor was 4.1. An improvement effect can be seen as compared with the sensitivity of 0.7 when sol alone is added.

[0054]

[Table 1]

When the carbon dioxide detecting body is scratched, it becomes more difficult to scratch as the amount of silica added increases, and the strength increases but the sensitivity deteriorates. Further, although the screen-printed sample exhibits the sensitivity, the sensitivity is lower than that of the disc-shaped sample (standard product).

The sensitivity of a sample prepared in the same manner by changing the average particle diameter of CuO without adding silica sol is shown in (Table 2).

[0057]

[Table 2]

When the average particle diameter of CuO is 1 μm or less, the sensitivity is improved and the effect can be seen. CuO seems to be related to the impedance of the carbon dioxide sensing body, and is considered to reduce the electric resistance to improve the impedance and facilitate the expression of sensitivity.

Example 2 Commercially available BaCO ₃ , CeO ₂ and CuO were weighed in a molar ratio of 6:63:31, mixed and ground in a mortar, and then 7.0 g of this mixed raw material and terpineol 1 0.1 g, 1.1 g of a vehicle prepared by mixing terpineol and ethyl cellulose in a ratio of 1: 1 and 0.8 g of a dispersant are mixed to prepare a paste for a carbon dioxide detecting body.

A carbon dioxide sensor is prepared in the same manner as in Example 1 using a ceramic substrate. Apply the sol solution containing silica for the cover to the heater and the electrode, and apply at 700 ° C for 5
Heat-treat for minutes.

Commercially available Cu (NO ₃ ) ₂ was added to 10 g of ethanol.
A sol solution containing a solution of 7.6 g of 3H ₂ O (10 g) and a commercially available organic solvent-based silica (SiO ₂ content of 30
%) 5 g, and the carbon dioxide sensor is immersed in the solution. After confirming that bubbles are not generated while shaking the solution occasionally, the carbon dioxide sensor is taken out and heat treatment is performed at 700 ° C. for 5 minutes. The weight increase after immersion measured using the disk product was 4%. It is thought that there is a similar weight increase.

The solution mixed with the sol solution of silica is Ce
(NO ₃₎ in an alcohol solution of ₃ · 6H ₂ O, may be a combination of an aqueous solution containing sol solution and Ba ions of soluble silica.

Although the workability is deteriorated, by immersing the heat-treated sample in a sol solution of silica, silica can be added without breaking the sintered portion of the raw material, and deterioration of sensitivity can be suppressed.

The sensitivity of the sample measured in the same manner as in Example 1 is 5.7 dB, which is a good sensitivity as compared with the similar addition amount shown in (Table 1).

Further, various compositions and components can be dealt with by changing the mixing component and concentration of silica in the sol solution according to the components and composition of the carbon dioxide detecting body.

Example 3 An aqueous solution prepared so that the Ba, Ce and Cu components have a molar ratio of Ba: Ce: Cu = 6: 63: 31 and a sol solution of acidic silica were mixed with B
The a, Ce, and Cu components are mixed so that the weight calculated as BaO, CeO ₂ , and CuO and the weight of silica are 1: 1 and heated and dried with stirring. 7.0 g of this mixed raw material, 1.1 g of terpineol, 1.1 g of a vehicle prepared by mixing terpineol and ethyl cellulose in a ratio of 1: 1 and 0.8 g of a surfactant were mixed to prepare a paste for a carbon dioxide sensing body. To do.

Using this paste, a ceramic substrate is screen-printed to prepare a carbon dioxide gas sensor in the same manner as in Example 1. For carbonation of the constituents, heat treatment may be performed in a gas containing carbon dioxide. The strength of the carbon dioxide detection body is strong and suitable for practical use.

The sensitivity of the sample measured in the same manner as in Example 1 is 6.1 dB, which is a good sensitivity. By this method, the carbon dioxide sensing body can be formed on the ceramic substrate without degrading the sensitivity.

Further, by changing the mixed components of silica in the sol solution, it is possible to easily prepare a sensor with an arbitrary composition and components.

[0070]

INDUSTRIAL APPLICABILITY The present invention can improve strength and make the carbon dioxide sensor thinner and smaller than conventional ones, and at the same time, it can be produced by screen printing to improve productivity and reduce manufacturing cost. It is a target. In addition, it is possible to improve the deterioration of sensitivity associated with screen printing.

[Brief description of drawings]

FIG. 1 is a sectional view of a carbon dioxide sensor according to a first embodiment of the present invention.

FIG. 2 is a sectional view of a carbon dioxide sensor according to a second embodiment of the present invention.

FIG. 3 is a sectional view of a carbon dioxide sensor according to a third embodiment of the present invention.

FIG. 4 is a sectional view of a carbon dioxide sensor according to a fourth embodiment of the present invention.

[Explanation of symbols]

 1 heater 2 substrate 3 electrode 4 carbon dioxide detection body 5 electrode 6 electrode

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shinji Morimoto 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (22)

[Claims] 1. A ceramic layer containing at least one kind of carbonate, complex metal oxide, and non-complex metal oxide is formed as a carbon dioxide sensing body, and a pair of electrodes is formed on the ceramic layer. A carbon dioxide sensor having a structure in which the electrode part and the electrode part are formed on a substrate heated by a heater. 2. A carbon dioxide sensor according to claim 1, wherein ceramics are formed as a carbon dioxide detecting body on the surface of the substrate heated by the heater, and the carbon dioxide detecting body contains silica gel. 3. The carbon dioxide gas sensor according to claim 1, wherein the carbonate contains an alkali metal carbonate. 4. The carbon dioxide gas sensor according to claim 1, wherein the carbonate contains an alkaline earth metal carbonate. 5. The carbon dioxide gas sensor according to claim 1, which contains lithium carbonate as a carbonate. 6. The carbon dioxide gas sensor according to claim 1, wherein barium carbonate is contained as the carbonate. 7. The carbon dioxide gas sensor according to claim 1, which contains a perovskite type oxide as the composite metal oxide. 8. The carbon dioxide gas sensor according to claim 1, wherein barium titanate is included as the composite metal oxide. 9. The carbon dioxide gas sensor according to claim 1, wherein the non-composite metal oxide contains at least one of cerium oxide and copper oxide. 10. The carbon dioxide sensor according to claim 9, wherein the average particle diameter of the copper oxide is 1 μm or less. 11. An electrode is formed on the surface of a substrate heated by a heater, a ceramic layer of a carbon dioxide sensing body is formed on the electrode, and a pair of electrodes is formed on the ceramic layer. Claims 1 and 2, characterized in that
The carbon dioxide gas sensor according to any one of 3, 4, 5, 6, 7, 8, 9, and 10. 12. A ceramic layer of a carbon dioxide detecting body is formed on a surface of a substrate heated by a heater, and a pair of electrodes is formed on the ceramic layer. 3, 4, 5, 6, 7, 8, 9, 10
The carbon dioxide sensor according to any one of 1. 13. A ceramic layer of a carbon dioxide detecting body is formed on the surface of a substrate heated by a heater, and a pair of electrodes is formed between the substrate and the ceramic layer. 1, 2, 3, 4, 5, 6, 7, 8,
The carbon dioxide sensor according to any one of 9, 10 and 10. 14. A ceramic layer of a carbon dioxide detecting body is formed on the surface of a substrate heated by a heater, and one or more electrodes are formed on one side of the ceramic layer and one or more electrodes are formed on the opposite side. Claims 1 and 2, characterized in that
The carbon dioxide gas sensor according to any one of 3, 4, 5, 6, 7, 8, 9, and 10. 15. A carbon dioxide sensor, wherein a heater layer is formed on a surface of the substrate opposite to the ceramic layer. 16. A carbon dioxide gas sensor, characterized in that a heater layer and a ceramic layer of a carbon dioxide gas detection body are formed on the surface of the substrate. 17. A method for manufacturing a carbon dioxide gas sensor, characterized in that the heater layer, the carbon dioxide gas sensing body, and the electrode layer formed on the substrate are formed by screen printing using a paste of each material. 18. A method of manufacturing a carbon dioxide gas sensor, wherein a heat treatment temperature at the time of manufacturing a carbon dioxide gas sensor including a heater layer, a carbon dioxide gas detection body, and an electrode layer formed on the substrate is set to 900 ° C. or lower. 19. A method for producing a carbon dioxide gas sensor, characterized in that a ceramic sol formed on the substrate is mixed with a silica sol solution to form a paste, and then screen printing is performed. 20. A carbon dioxide gas sensor comprising a heater layer formed on the substrate, a carbon dioxide gas sensing body, and an electrode layer, prepared, immersed in a sol solution of silica, dried and heat treated. Production method. 21. The silica sol solution according to claim 19, wherein a solution containing a silica sol in which one or more metal salts of the material used for the carbon dioxide sensing body is dissolved is used. Method for manufacturing carbon dioxide sensor. 22. A sol solution containing silica in which a metal salt of a material used for a carbon dioxide detecting body is dissolved is formed into a paste,
A method for manufacturing a carbon dioxide sensor, which comprises screen-printing on a substrate.