JPH1073558A - Manufacture of carbonic gas sensor and carbonic gas sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform the mass production of the sensors having the high detecting sensitivity and the quick detecting speed at a low cost simply by manufacturing the detecting part by using the powder, which is obtained by the drying and thermal decomposition of acetate solution and has the uniform composition and the particle diameter in the specified range. SOLUTION: A carbonic gas sensor is constituted of a carbonic-gas detecting part 1, energizing electrodes 2a and 2b and lead wires 3a and 3b. Then, at first, the acetate such as barium acetate, copper acetate and cerium acetate is mixed and dissolved into the solvent such as water acetate aqueous solution and alcohol. Then, this acetate solution is agitated by using a hot stirrer or the like and heated and dried. The solvent is evaporated, and mixed powder is obtained. Then, the powder undergoes thermal decomposition. At this time, the average particle diameter is set at 0.1-0.5μm. Then, after the mixed powder is crushed, the power is formed into the specified shape such as a plate shape and comb shape, heated and sintered. Thus, the detecting part 1 is formed. In this way, the raw-material powder having the quick detecting speed and the high detecting speed is formed, molded and sintered. Thus, the detecting part 1 can be manufactured simply in the free shapes.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a carbon dioxide gas sensor using a mixture of a carbonate and a non-composite metal oxide, and a carbon dioxide gas sensor.

[0002]

2. Description of the Related Art In recent years, environmental measurement, horticulture, production equipment, etc.
Sensor is used to detect the concentration of carbon dioxide
It has been. The carbon dioxide sensor uses infrared detection.
Using an electrolytic solution, heat conduction,
Some of these types of charcoal are commercially available.
The acid gas sensors are both large and cost-effective to manufacture.
High. Therefore, NaCO as an electrode auxiliary material_ThreeWhen
Alkaline ion conductive solid electrolyte such as NASICON
Used, using Li ion conductor, K _TwoCO_Three
CO such as_Three ^2-Using ionic conductors, hydroxide aptamers
Various detection methods, such as those that use the resistance value of
Research and development of a new type of carbon dioxide sensor
You.

Further, as one of the carbon dioxide sensors capable of miniaturizing the apparatus, a sintered body of a mixture of a metal oxide and a carbonate is combined with a pair of electrodes to form a sintered body. Non-composite metal oxide (containing 1 metal element)
There is one that detects the concentration of carbon dioxide from a change in electrical characteristics such as impedance and capacitance between electrodes due to a reversible carbonate formation reaction between the oxide of the type and carbon dioxide.

For example, JP-A-4-24548 describes "a carbon dioxide sensor using the change in capacitance of a mixture of a perovskite-type metal oxide and a non-composite metal oxide". Carbon dioxide sensors using rare earth oxides, which are a kind of composite metal oxides, are disclosed. In addition, the applicant of the present application also filed Japanese Patent Application No. 6-182.
261 filed an application for "a carbon dioxide sensor using a mixture of non-composite metal oxides."

[0005] These carbon dioxide sensors are all Cu
Non-composite metal oxides such as O and perovskite oxides such as BaTiO ₃ or various metal oxides are used as raw materials, mixed and pulverized at a predetermined mixing ratio, formed into a plate or the like, and then heat-treated. On the surface of the sintered carbon dioxide detector,
It has a configuration in which a pair of electrodes are formed.

Various additives mixed with a metal oxide have also been studied to improve the ability to detect carbon dioxide. For example, Japanese Patent Application Laid-Open No. 5-142180 proposes a noble metal element such as Ag or a transition metal element. ing. In addition, the applicant of the present invention has also disclosed such an additive in Japanese Patent Application No. 6-31341.
0 proposed BaO and Japanese Patent Application No. 7-165053 proposed carbonates and the like.

[0007]

However, the conventional carbon dioxide sensor using a sintered body of a mixture of a metal oxide and a carbonate has a low detection sensitivity to carbon dioxide and a low speed of detecting carbon dioxide. There was a problem that.

The present invention solves the above-mentioned conventional problems. A carbon dioxide gas sensor having a high carbon dioxide gas detection sensitivity and a high detection speed can be easily manufactured, and high-quality and stable quality can be mass-produced at low cost. It is an object of the present invention to provide a method of manufacturing a carbon dioxide gas sensor capable of producing carbon dioxide gas and a carbon dioxide gas sensor manufactured using the manufacturing method, which has a high detection sensitivity and a high detection speed.

[0009]

In order to solve the above-mentioned problems, a method for manufacturing a carbon dioxide gas sensor according to the present invention comprises a mixing and dissolving step of mixing and dissolving an acetate in a solvent, and an acetate solution obtained by the mixing and dissolving step. And a pyrolysis step of pyrolyzing the mixed powder obtained in the drying step.

[0010] With this structure, it is possible to mix and dissolve acetates which are easily soluble in water and have a low decomposition temperature and to mix them at a molecular level, whereby fine particles having a uniform composition distribution can be easily obtained, and particles obtained by thermal decomposition can be obtained. Suppress growth and reaction,
It is possible to obtain a powder composed of an oxide or a carbonate having a small composition, having a uniform composition and a small particle size, having a small number of different phases. Such a carbon dioxide sensor having a uniform composition and a small particle diameter, made of an oxide or a carbonate, can be used to produce the carbon dioxide sensor of the carbon dioxide sensor. It can be easily manufactured,
It is possible to provide a method for manufacturing a carbon dioxide sensor that can be mass-produced at a low cost with high quality and stable quality.

Further, the carbon dioxide gas sensor of the present invention is characterized in that an acetate solution obtained by mixing and dissolving an acetate in a solvent is dried to produce a mixed powder, and the mixed powder is thermally decomposed to obtain an oxide or carbonate. A carbon dioxide detection unit composed of (a) a sintered body obtained by pulverizing, molding, and sintering, or (b) a thick film formed by screen-printing a paste containing a mixed powder; and And an electrode disposed on the unit.

With this configuration, the composition distribution of oxides or carbonates constituting the carbon dioxide gas detecting portion is uniform, so that the sensitivity of detecting the carbon dioxide gas is high, and since the particle diameter is small, the number of interfaces for detecting the carbon dioxide gas can be reduced. It is possible to provide a carbon dioxide sensor having a large area and a high carbon dioxide gas detection speed due to rapid diffusion of carbon dioxide into the particles.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION According to the first aspect of the present invention, a mixed dissolving step of mixing and dissolving an acetate in a solvent, and drying an acetate solution obtained by the mixing and dissolving step to obtain a mixed powder A drying step, and a pyrolysis step of thermally decomposing the mixed powder obtained in the drying step, in order to produce a carbon dioxide gas detection unit having a high carbon dioxide gas detection speed and a high detection sensitivity. The raw material powder of the present invention can be provided.

As the acetate, barium acetate, strontium acetate, calcium acetate, copper acetate, nickel acetate,
Cobalt acetate, yttrium acetate, neodymium acetate, cerium acetate, lanthanum acetate, zirconium acetate, zinc acetate and the like are used.

As the solvent, water, an aqueous solution of acetic acid, alcohol or the like is used. The invention described in claim 2 of the present invention
The mixed powder pyrolyzed in the pyrolysis step has an average particle size of 0.05 μm to 0.6 μm.
m, preferably 0.1 μm to 0.5 μm, to improve the detection characteristics of the carbon dioxide sensor,
It is possible to prevent a decrease in the detection sensitivity in long-term use and to suppress a reaction between particles of the raw material powder that deteriorates the detection sensitivity.

As the average particle size of the mixed powder becomes smaller than 0.1 μm, the production becomes difficult due to the small particle size, and the detection sensitivity due to the reaction between the particles tends to deteriorate. As the particle size increases, the interface between particles decreases and the detection sensitivity tends to decrease.

According to a third aspect of the present invention, in the first aspect of the present invention, the acetate salt contains barium acetate, and the oxide or Compared to the case where the carbon dioxide gas detection section of the carbon dioxide gas sensor is manufactured from carbonate, the carbon dioxide gas detection sensitivity can be particularly improved.

According to a fourth aspect of the present invention, there is provided the invention as set forth in any one of the first to third aspects, wherein
In the case where the acetate contains cerium acetate and copper acetate, and when producing the carbon dioxide gas detection unit using various acetates, it is possible to produce a carbon dioxide gas sensor having particularly high carbon dioxide gas detection sensitivity. Has the effect of being able to.

According to a fifth aspect of the present invention, there is provided the method according to any one of the first to fourth aspects, wherein the mixed powder pyrolyzed in the pyrolysis step is pulverized into a predetermined shape. And a firing step of heating and sintering the molded article formed in the molding step, and detecting the carbon dioxide gas by molding and firing the mixed powder. It has the effect of being able to easily produce a carbon dioxide gas detection section with high sensitivity and high detection speed, and to be able to mass-produce a carbon dioxide gas sensor with high quality and stable quality at low cost.

According to a sixth aspect of the present invention, there is provided a paste according to any one of the first to fourth aspects, wherein the paste comprises a paste containing the mixed powder thermally decomposed in the pyrolysis step. A thick film forming step of forming a thick film by screen-printing the paste obtained by the paste making step on an insulating substrate to form a thick film. In addition to being able to form a carbon dioxide gas detection part with high speed and a simple and flexible shape, it is possible to mass-produce carbon dioxide gas sensors with high quality and stable quality at low cost. This has the effect that the detection sensitivity of carbon dioxide gas can be further improved as compared with the case of forming with.

According to a seventh aspect of the present invention, there is provided a sintered body obtained by the method for manufacturing a carbon dioxide sensor according to the fifth aspect or a thick film obtained by the method for manufacturing a carbon dioxide sensor according to the sixth aspect. A carbon dioxide gas detection unit comprising at least one of the carbon dioxide gas detection units and at least two energized electrodes disposed on the carbon dioxide gas detection unit, and has a high carbon dioxide gas detection sensitivity and a high detection speed. This has the effect that a quick carbon dioxide gas sensor can be provided.

According to an eighth aspect of the present invention, in accordance with the seventh aspect of the present invention, a current-carrying electrode is provided on one surface of the carbon dioxide gas detecting portion, and at least one or more opposing electrodes are provided on a surface opposing the one surface. An electrode is provided, which has an effect that carbon dioxide gas detection sensitivity can be further improved.

Hereinafter, specific examples of the embodiments of the present invention will be described with reference to the drawings. (Embodiment 1) A method for manufacturing a carbon dioxide sensor according to a first embodiment of the present invention will be described below.

First, as a mixing and dissolving step, acetates weighed at a predetermined composition ratio are mixed and dissolved in a solvent.

Next, as a drying step, the acetate solution obtained in the mixing and dissolving step is heated and dried with stirring using a hot stirrer or the like to evaporate the solvent and obtain a mixed powder.

Next, as a thermal decomposition step, the mixed powder obtained in the drying step is heated in an electric furnace or the like to be thermally decomposed.
It is considered that each component in the mixed powder is changed to an oxide by the thermal decomposition. Further, in the thermal decomposition step, if necessary, heat treatment is performed in an atmosphere containing carbon dioxide gas to change oxides to carbonates.

Next, as a forming step, the mixed powder pyrolyzed in the pyrolysis step is pulverized and then formed into a predetermined shape such as a plate or a comb.

Next, as a firing step, the molded product molded in the molding step is heated and sintered to obtain a carbon dioxide gas detecting portion of the carbon dioxide gas sensor.

A carbon dioxide sensor can be obtained by forming at least two current-carrying electrodes on the carbon dioxide detection section by a known method.

As described above, according to the present embodiment, it is possible to provide a raw material powder for producing a carbon dioxide gas detecting portion having a high carbon dioxide gas detection speed and a high detection sensitivity.

Further, by shaping and firing this raw material powder, a carbon dioxide gas detecting section having a high carbon dioxide gas detection sensitivity and a high detection speed can be easily produced, and a high quality, stable quality carbon dioxide gas can be produced at low cost. Gas sensors can be mass-produced.

The method for manufacturing a carbon dioxide gas sensor according to the present embodiment may include a step of arranging a carbon dioxide gas detecting portion on an insulating substrate such as an alumina substrate and forming an electrode on the carbon dioxide gas detecting portion. Good.

Further, a step of arranging an electric heater for heating the carbon dioxide gas detecting portion to a predetermined temperature on such an insulating substrate, and a method of protecting a heat resistant material such as glass on the carbon dioxide gas detecting portion and the electric heater. A step of forming a layer may be provided. When the heat-resistant protective layer is formed on the carbon dioxide gas detector, the carbon dioxide gas detector is formed so that a part of the carbon dioxide gas detector is exposed to the outside so that the carbon dioxide gas can come into contact with the carbon dioxide gas detector. There is a need.

(Embodiment 2) A method of manufacturing a carbon dioxide sensor according to a second embodiment of the present invention will be described below.

In the method of manufacturing a carbon dioxide gas sensor according to the present embodiment, the mixing and dissolving step, the drying step, and the thermal decomposition step are all the same as those in the first embodiment, and a description thereof will be omitted.

After the pyrolysis step, as a paste preparation step, a paste for a carbon dioxide gas detection unit is prepared by mixing the mixed powder pyrolyzed in the pyrolysis step with a solvent such as terpineol, a vehicle, or a dispersant.

Next, as a thick film forming step, the paste for the carbon dioxide gas detection section obtained in the paste making step is screen-printed on an insulating substrate such as alumina to form a thick film, which is then subjected to carbon dioxide gas detection. Department.

A carbon dioxide sensor can be obtained by forming at least two current-carrying electrodes on the carbon dioxide detector by a known method.

As described above, according to the present embodiment, it is possible to provide a raw material powder for producing a carbon dioxide gas detection section having a high carbon dioxide gas detection speed and a high detection sensitivity.

Further, by using the raw material powder, a carbon dioxide gas detecting portion having a high carbon dioxide gas detection sensitivity and a high detection speed can be formed in a simple and flexible shape.
Carbon dioxide sensors can be mass-produced with high quality and stable quality at low cost.

Further, the carbon dioxide gas detection sensitivity can be further improved as compared with the case where the carbon dioxide gas detecting portion is formed of a sintered body.

In the method for manufacturing a carbon dioxide gas sensor according to the present embodiment, silica sol or the like may be added in order to improve the strength of the thick film when producing the paste for the carbon dioxide gas detecting portion.

In the method of manufacturing a carbon dioxide gas sensor according to the present embodiment, at least two electrodes are formed in advance on an insulating substrate such as an alumina substrate, and the carbon dioxide gas is formed so as to come into contact with these electrodes in the thick film forming step. A thick film may be formed by screen printing the paste for the detection unit.

Also, a step of arranging an electric heater for heating the carbon dioxide gas detecting portion to a predetermined temperature on such an insulating substrate, and a method of protecting a heat resistant material such as glass on the carbon dioxide gas detecting portion and the electric heater. A step of forming a layer may be provided. When the heat-resistant protective layer is formed on the carbon dioxide gas detector, the carbon dioxide gas detector is formed so that a part of the carbon dioxide gas detector is exposed to the outside so that the carbon dioxide gas can come into contact with the carbon dioxide gas detector. There is a need.

(Embodiment 3) FIG. 1 is a sectional view of a carbon dioxide sensor according to a third embodiment of the present invention.

In FIG. 1, reference numeral 1 denotes a carbon dioxide gas detection unit;
Reference numerals a and 2b denote current-carrying electrodes, and reference numerals 3a and 3b denote lead wires.

The carbon dioxide sensor according to the present embodiment
The power supply apparatus includes a carbon dioxide gas detection unit 1, current-carrying electrodes 2a and 2b disposed on the carbon-gas detection unit 1, and lead wires 3a and 3b disposed on the current-carrying electrodes 2a and 2b.

The difference between the carbon dioxide sensor of the present embodiment and the conventional example is that the carbon dioxide detection unit 1 produces a mixed powder by drying an acetate solution obtained by mixing and dissolving acetate in a solvent at a predetermined composition ratio. Then, the powder is composed of a sintered body obtained by pulverizing, molding and firing a powder made of an oxide or a carbonate obtained by thermally decomposing this mixed powder.

The carbon dioxide sensor according to the present embodiment
It is obtained by the method for manufacturing a carbon dioxide sensor according to the first embodiment. The current-carrying electrodes 2a and 2b may be made of any material that has a small resistance and does not change at the operating temperature.
The paste may be formed by screen printing a paste containing any of t, Ag, RuO _{2, and the} like, followed by heat treatment. In addition, Pt, Ni, Au, or the like in a plate shape or a linear shape is used as the lead wires 3a and 3b.

The method of detecting the concentration of carbon dioxide using the carbon dioxide sensor having the above configuration is the same as that of the conventional example. For example, the carbon dioxide sensor according to the present embodiment is installed in an electric furnace or the like to measure the carbon dioxide concentration. It can be detected by measuring electrical characteristics such as impedance and capacitance between the lead wires 3a and 3b while passing the test gas.

As described above, according to the present embodiment, it is possible to provide a carbon dioxide gas sensor having a high carbon dioxide gas detection sensitivity and a high detection speed.

(Embodiment 4) FIG. 2 is a sectional view of a carbon dioxide sensor according to a fourth embodiment of the present invention, and FIG. 3 is an exploded perspective view of a main part of the carbon dioxide sensor according to the fourth embodiment of the present invention.

2 and 3, 2c and 2b are heater electrodes, 3c and 3d are lead wires, 4 is a carbon dioxide gas detecting portion, 5 is an insulating substrate, 6 is a counter electrode, 7 is a heater portion, 8
Reference numerals a and 8b denote protective layers, and current-carrying electrodes 2a and 2b and lead wires 3a and 3b are the same as those in the third embodiment.

The carbon dioxide sensor according to the present embodiment
An insulating substrate 5 such as alumina, current-carrying electrodes 2a and 2b disposed on the insulating substrate 5, lead wires 3a and 3b disposed on the current-carrying electrodes 2a and 2b, and current-carrying electrodes 2a and 2b. A carbon dioxide gas detector 4 disposed on the insulating substrate 5 so as to be in contact with the counter electrode 6 disposed on the carbon dioxide gas detector 4;
A heater electrode 2c, 2d disposed at a different position from the energizing electrodes 2a, 2b on the insulating substrate 5;
c, 2d, a heater section 7 disposed on the insulating substrate 5, lead wires 3c, 3d disposed on the heater electrodes 2c, 2d, a carbon dioxide gas detection section 4, and a counter electrode. 6 and protective layers 8a and 8b formed on heater section 7
And

The difference between the carbon dioxide sensor according to the present embodiment and the third embodiment is that the carbon dioxide sensor is different from the third embodiment in that the carbon dioxide sensor is provided together with the current-carrying electrodes 2a and 2b provided on the carbon dioxide gas detector 4.
b is provided with a counter electrode 6 disposed on a surface opposite to the surface on which b is disposed.

Further, the carbon dioxide detecting section in the present embodiment comprises a sintered body obtained by the method for manufacturing a carbon dioxide sensor according to the first embodiment, or a carbon dioxide sensor similar to the method for manufacturing a carbon dioxide sensor according to the second embodiment. Any of the thick films obtained by forming a paste for the gas detection unit on the insulating substrate 5 by screen printing or the like and then performing a heat treatment may be used.

The heater section 7 can be formed by a method of screen-printing a paste containing Pt or RuO ₂ and then performing a heat treatment. Further, the heater electrodes 2c,
2d, the counter electrode 6 has the same shape as the conducting electrodes 2a and 2b.
The paste can be formed by screen printing a paste containing any of u, Pt, Ag, RuO _{2, and the} like, followed by heat treatment. The lead wires 3c and 3d are formed in a plate-like or linear shape like the lead wires 3a and 3b.
t, Ni, Au or the like is used, and heat-resistant glass or the like is used for the protective layers 8a and 8b.

Further, the current-carrying electrodes 2a and 2b of the carbon dioxide gas sensor according to the present embodiment may be arranged in a substantially square shape and opposed to each other, but as shown in FIG. It may be done. However, the current-carrying electrodes 2a, 2
A part of b needs to have a structure that overlaps with the counter electrode 6 via the carbon dioxide gas detector 4.

The method of detecting the concentration of carbon dioxide using the carbon dioxide sensor having the above configuration is the same as that of the conventional example. A predetermined voltage is applied between the lead wires 3a and 3b, and the heater section 7 is applied.
Is heated, and while the carbon dioxide gas detecting section 4 is heated to a predetermined temperature, a test gas whose carbon dioxide gas concentration is to be measured is ventilated or placed under the atmosphere of the test gas.
The carbon dioxide concentration can be detected by measuring electrical characteristics such as impedance and capacitance between a and 3b.

As described above, according to the present embodiment, it is possible to provide a carbon dioxide gas sensor having a high carbon dioxide gas detection sensitivity and a high detection speed, and to provide a carbon dioxide gas sensor as compared with the case where no counter electrode is formed. Can be further improved.

In the carbon dioxide gas sensor according to the present embodiment, the heater, the heater electrode, and the protective layer may not be provided. If there is no heater, the electric furnace may be the same as in the third embodiment. The carbon dioxide gas can be detected by a method in which a test gas is ventilated into an electric furnace while the carbon dioxide gas sensor is heated to a predetermined temperature.

Further, as shown in the present embodiment, when the protective layer is provided on the carbon dioxide gas detecting portion, the carbon dioxide gas detecting portion is provided so that the carbon dioxide gas can be brought into contact with the carbon dioxide gas detecting portion. Must be arranged so that a part of it is exposed to the outside.

Further, the heater section shown in the present embodiment may be provided on any surface of the insulating substrate on the same side as the energizing electrode or on the opposite side.

The insulating substrate of the carbon dioxide sensor according to the present embodiment may be any substrate as long as it has at least an insulating surface, a high strength, and can withstand a heat treatment temperature or an operating temperature during manufacturing. A material having an insulating film formed on the surface may be used.

[0065]

Next, the present invention will be described in more detail with reference to examples and the like.

Example 1 Commercially available barium acetate (Ba)
(CH ₃ COO) _2), cerium acetate (Ce (CH ₃ CO
O) ₃ .H ₂ O), copper acetate (Cu (CH ₃ COO) ₂ .H ₂
O) was weighed so that the total amount was 5 g at a molar ratio of 20:45:35, and then all acetates were dissolved in 50 ml of pure water.

Next, this acetate solution was heated and dried with stirring using a hot stirrer, and the obtained mixed powder was transferred to a vessel for heat treatment, and heated at 300 ° C. in an electric furnace at 300 ° C.
Heated for hours to pyrolyze.

Next, the thermally decomposed mixed powder was pulverized in a mortar, and the pulverized material was formed into a disk having a diameter of 10 mm and a thickness of 0.4 mm using a press machine. It was fired at 800 ° C. for 0.5 hour to obtain a sintered body.

The obtained sintered body was used as a carbon dioxide gas detecting section.
A commercially available platinum paste was applied as a circular electrode on both surfaces of the carbon dioxide gas detecting section, and then a platinum wire was attached as a lead wire to the applied portion, followed by heat treatment at 800 ° C. for 10 minutes.

The carbon dioxide sensor of the first embodiment was manufactured as described above. (Example 2) A disk having a diameter of 10 mm and a thickness of 0.4 mm was molded in the same manner as in the first example, and the obtained molded product was fired at 900 ° C for 0.5 hour in an electric furnace to obtain a sintered body. Obtained. Electrodes and lead wires were formed on the sintered body in the same manner as in the first embodiment.

The carbon dioxide sensor manufactured as described above was used as the second embodiment. Comparative Example 1 Commercially available barium carbonate, cerium oxide, and copper oxide were weighed at a molar ratio of 20:45:35 so that the total amount was 1 g, and then mixed and pulverized in a mortar. Was formed into a disk having a diameter of 10 mm and a thickness of 0.4 mm, and the obtained molded product was fired in an electric furnace at 800 ° C. for 0.5 hour to obtain a sintered body.

The obtained sintered body was used as a carbon dioxide gas detecting section.
A commercially available platinum paste was applied as a circular electrode on both surfaces of the carbon dioxide gas detecting section, and then a platinum wire was attached as a lead wire to the applied portion, followed by heat treatment at 800 ° C. for 10 minutes.

The carbon dioxide sensor manufactured as described above was used as a first comparative example. (Comparative Example 2) After forming a disk having a diameter of 10 mm and a thickness of 0.4 mm in the same manner as in the first comparative example, the obtained molded product was fired at 900 ° C for 0.5 hour in an electric furnace to obtain a sintered body. Obtained. Electrodes and lead wires were formed on the sintered body in the same manner as in the first comparative example.

The carbon dioxide sensor manufactured as described above was used as a second comparative example. (Evaluation Example 1) In order to compare the performances of the carbon dioxide gas sensors in the first embodiment, the second embodiment, the first comparative example, and the second comparative example, the following sensitivity tests were performed on the carbon dioxide concentration.

Each of the carbon dioxide sensors was placed in an electric furnace controlled at 550 ° C., and dried air was passed through the electric furnace and dry air containing 2% carbon dioxide was passed through the electric furnace.
Each impedance analyzer (4192, manufactured by YHP)
Using A), the capacitance component between the lead wires at a frequency of 10 kHz was measured by the two-terminal method. The measurement of the capacitance component is as follows:
Dry air or dry air containing carbon dioxide gas was passed through the electric furnace until the value reached a substantially constant value. When the value reached the constant value, the capacity component was determined.

From the capacity component C1 when dry air is passed through the electric furnace and the capacity component C2 when dry air containing 2% carbon dioxide gas is passed, the following relational expression (Equation 1) is obtained.

[0077]

(Equation 1)

From the above, the detection sensitivity of carbon dioxide gas was determined.
From the relational expression shown in (Equation 1), it can be said that the larger the value of the detection sensitivity is, the better the detection sensitivity of the carbon dioxide gas is. In addition, 90% of the time required from the time when dry air or dry air containing carbon dioxide gas is ventilated into the electric furnace to the time when the value of the capacity component becomes 90% of the finally constant capacity component is detected. The time was determined for each carbon dioxide sensor.

The detection sensitivity determined as described above and 9
The 0% detection time is summarized (Table 1).

[0080]

[Table 1]

The cerium acetate and copper acetate used in the first and second embodiments were converted into their respective oxides by heat treatment.
Barium acetate is considered to have been converted to barium oxide by heat treatment. However, comparing the results of the first embodiment and the first comparative example, and the second embodiment and the second comparative example, it was found that oxide and carbonate were used as starting materials. The detection sensitivity is higher and the 90% detection time is shorter when a mixed powder obtained from an aqueous solution of acetate is heat-treated as in the first and second embodiments than when a salt is used. Became clear. Further, the firing temperature for obtaining the sintered body serving as the carbon dioxide gas detecting portion is set at 900 ° C. to 8 from the comparison between the first embodiment and the second embodiment.
It was found that 00 ° C. improved the detection sensitivity and the detection speed.

Although not shown in (Table 1), the first
It is also clear that the load required to break the carbon dioxide detector of the example is about three times that of the first comparative example.
It has been found that the carbon dioxide gas sensors in the first and second embodiments also have improved mechanical strength.

(Evaluation Example 2) In the method for producing a carbon dioxide sensor of the present invention, the average particle size of the powder obtained by drying the nitrate solution was determined as follows.

A commercially available barium acetate (Ba (CH ₃ CO
O) ₂ ), cerium acetate (Ce (CH ₃ COO) ₃ .H
₂ O), copper acetate _{(Cu (CH 3 COO) 2} · H 2 O) was dissolved alone in pure water, respectively, dried and heated with stirring on a hot stirrer, mixed powder obtained was It was transferred to a heat treatment container and heated in an electric furnace at 300 ° C. for 2 hours to be thermally decomposed. Further, only the powder obtained from the barium acetate aqueous solution was further subjected to carbonation treatment in a mixed gas stream comprising 5% carbon dioxide gas and dry air.

For each of the barium carbonate, cerium oxide, and copper oxide thus obtained, the average particle size was determined using a laser diffraction / scattering type particle size distribution analyzer (manufactured by Horiba, Ltd.).

The average particle size of barium carbonate, cerium oxide and copper oxide used in the first comparative example and the second comparative example was determined in the same manner.

The average particle sizes are shown in Table 2 below.

[0088]

[Table 2]

As is clear from Table 2, the barium carbonate, cerium oxide, and cerium oxide obtained from acetate by the method of manufacturing the carbon dioxide gas sensor of the present invention are different from the commercially available barium carbonate, cerium oxide, and copper oxide. It became clear that all of the copper oxides had smaller average particle diameters. When the carbon dioxide gas detection unit is manufactured by firing, the smaller the particle diameter of the starting oxide or carbonate, the higher the detection sensitivity and the faster the detection speed. It is also considered that such a small average particle diameter of the particles serving as the raw material is one of the factors that make the characteristics of the carbon dioxide sensor according to the present invention excellent.

(Evaluation Example 3) After leaving the carbon dioxide sensors of the first embodiment and the first comparative example in an electric furnace adjusted to 550 ° C. for 1000 hours, the carbon dioxide sensor was evaluated in the same manner as in (Evaluation Example 1). Was determined.

As a result, the detection sensitivity of the carbon dioxide sensor of the first comparative example was 12% as compared with that before leaving for 1000 hours.
On the other hand, the carbon dioxide gas sensor of the first embodiment has a very small reduction in detection sensitivity of 4%, and the carbon dioxide gas sensor of the present invention has improved durability and life characteristics as compared with the conventional example. did.

To improve such durability and life characteristics,
As described in (Evaluation Example 1), the mechanical strength of the carbon dioxide gas detection unit is improved, and as described in (Evaluation Example 2), the average particle diameter of the raw material constituting the carbon dioxide gas detection unit is small. And good adhesion to the electrodes.

(Experimental Example 1) Barium acetate as material 1
Any one of strontium acetate and calcium acetate
And the material 2 is copper acetate, nickel acetate, cobalt acetate, yttrium acetate, or zinc acetate, and the material 3 is cerium acetate, lanthanum acetate, zirconium acetate, or neodymium acetate. One of the acetates is selected, and seven kinds of acetates prepared by dissolving material 1, material 2, and material 3 in pure water at a molar ratio of 20:35:45 are used in the same manner as in the first embodiment. Was manufactured.

Further, as the material 1, any one of barium carbonate, strontium carbonate and calcium carbonate is used, and as the material 2, any one of copper oxide, nickel oxide, cobalt oxide, yttrium oxide and zinc oxide is used. Oxides, cerium oxide, lanthanum oxide,
An oxide selected from zirconium oxide and neodymium oxide is selected, and the molar ratio of material 1, material 2, and material 3 is 2
Seven types of carbon dioxide sensors were manufactured in the same manner as in the first comparative example using the mixed powder mixed at 0:35:45.

With respect to the obtained 14 types of carbon dioxide sensors, the detection sensitivity of carbon dioxide was determined in the same manner as in (Evaluation Example 1).

Table 3 shows that each of the components constituting the carbon dioxide gas sensing portion selected as the material 1, material 2, and material 3 of the carbon dioxide gas sensor and acetate were prepared in the same manner as in the first embodiment of the present invention. The detection sensitivity of the carbon dioxide gas sensor thus obtained was represented as sensitivity A, and the detection sensitivity of a carbon dioxide gas sensor produced from commercially available carbonates and oxides in the same manner as in the first comparative example was represented as sensitivity B.

[0097]

[Table 3]

From the comparison of the sensitivity A and the sensitivity B shown in Table 3, even if the components constituting the carbon dioxide sensor of the carbon dioxide sensor are the same, the carbon dioxide sensor manufactured by the method for manufacturing the carbon dioxide sensor of the present invention. It was clarified that the detection sensitivity was higher in any of the components than in the carbon dioxide gas sensor manufactured using commercially available carbonates and oxides.

Among the carbon dioxide gas sensors produced from acetate in the same manner as in the first embodiment of the present invention, the improvement of the detection sensitivity is particularly effective for the carbon dioxide gas sensor containing barium carbonate as one of the constituent components. In particular, the carbon dioxide gas sensor composed of barium carbonate, copper oxide and cerium oxide (a carbon dioxide gas sensor made from barium acetate, copper acetate and cerium acetate as a starting material) has the highest detection sensitivity in the sensitivity test under the same conditions. Was found to have.

Example 3 A carbon dioxide sensor having the same configuration as the carbon dioxide sensor shown in FIGS. 2 and 4 in the second embodiment was manufactured as follows.

First, similarly to the first embodiment, commercially available barium acetate (Ba (CH ₃ COO) ₂ ), cerium acetate (Ce (CH ₃ COO) ₃ .H ₂ O), copper acetate (Cu (C
H ₃ COO) ₂ .H ₂ O) was dissolved in pure water at a molar ratio of 20:45:35, and an acetate solution was dried and heat-treated. 6.5 g of a mixed powder, 1.4 g of terpineol, and 1.4 g of terpineol Then, 1.4 g of a vehicle prepared by mixing 9: 1 with ethyl cellulose and 0.7 g of a dispersant were mixed to prepare a paste for a carbon dioxide gas detecting portion.

Next, gold paste was screen-printed at two places on a 2 mm × 3 mm × 0.3 mm alumina substrate 5 and then heat-treated at 800 ° C. for 10 minutes to form heater electrodes 2 c and 2 d for voltage application. did. Next, the heater electrode 2
After the RuO ₂ paste is screen-printed so as to come into contact with both of the electrodes c and 2d and then heat-treated at 800 ° C. for 10 minutes to form the heater section 7, the heater electrodes 2 c and 2 d are formed with gold as lead wires 3 c and 3 d. Wires were arranged.

Next, Pt paste was screen-printed at two places on the alumina substrate 5 and then heat-treated at 800 ° C. for 10 minutes to form two current-carrying electrodes 2a and 2b. The paste for the carbon dioxide gas detector is screen-printed so as to be in contact with both of the current-carrying electrodes 2a and 2b, dried and then dried.
A heat treatment was performed at 30 ° C. for 30 minutes to form a carbon dioxide gas detection unit 4.
Thereafter, a Pt paste is screen-printed on the carbon dioxide gas detection unit 4 and then heat-treated at 800 ° C. for 10 minutes to form the counter electrode 6, and then lead wires 3 a and 3 b are formed on both the current-carrying electrodes 2 a and 2 b as gold. The wires were provided to obtain the carbon dioxide sensor of the third embodiment.

(Comparative Example 3) Except that the carbon dioxide gas detector 4 was produced using a mixed powder obtained by mixing and pulverizing commercially available barium carbonate, cerium oxide and copper oxide at a molar ratio of 20:45:35. Thus, a carbon dioxide gas sensor was manufactured in the same manner as in the third example, and this was used as a third comparative example.

(Evaluation Example 4) A voltage was applied to the heater portion of the carbon dioxide gas sensor of the third embodiment and the third comparative example, and the temperature of the carbon dioxide gas detection portion was adjusted to 550 ° C., as in (Evaluation Example 1). The detection sensitivity of each carbon dioxide sensor was determined by various methods.

The results are shown in (Table 4).

[0107]

[Table 4]

As is evident from Table 4, when the carbon dioxide gas detecting section is produced from the paste containing the constituents by screen printing, the acetate solution is dried and heat-treated as in the third embodiment. It has been found that the use of the obtained mixed powder has a higher detection sensitivity than the use of carbonates and oxides. Further, the third embodiment has a higher detection sensitivity under the same conditions as compared with the first embodiment, and forms the carbon dioxide gas detecting portion using the carbon dioxide gas detecting portion paste as in the third embodiment. It was also clarified that the carbon dioxide sensor that was used had better detection sensitivity.

[0109]

As described above, according to the method for manufacturing a carbon dioxide gas sensor of the present invention, it is possible to provide a raw material powder for producing a carbon dioxide gas detecting portion having a high carbon dioxide gas detection speed and a high detection sensitivity. At the same time, by molding and firing this raw material powder, the carbon dioxide gas detection unit has a high sensitivity for detecting carbon dioxide gas, and a carbon dioxide gas detection unit having a high detection speed can be manufactured in a simple and free shape, so that the capability of detecting carbon dioxide gas is high. In addition, an excellent effect that a carbon dioxide sensor that can be miniaturized can be manufactured with high mass productivity can be obtained.

Further, according to the carbon dioxide sensor of the present invention,
An excellent effect of being able to provide a carbon dioxide sensor having a high carbon dioxide gas detection sensitivity and a high detection speed and improving the durability of the carbon dioxide gas sensor is obtained.

[Brief description of the drawings]

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

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

FIG. 3 is an exploded perspective view of a main part of a carbon dioxide sensor according to a fourth embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Carbon dioxide gas detection part 2a, 2b Current supply electrode 2c, 2d Heater electrode 3a, 3b, 3c, 3d Lead wire 4 Carbon dioxide gas detection part 5 Insulating substrate 6 Counter electrode 7 Heater part 8a, 8b Protective layer

Claims (8)

[Claims] 1. A mixing and dissolving step of mixing and dissolving an acetate in a solvent, a drying step of drying an acetate solution obtained by the mixing and dissolving step to obtain a mixed powder, and a mixing and dissolving step obtained by the drying step. A method for producing a carbon dioxide sensor, comprising: a pyrolysis step of pyrolyzing a powder. 2. The method according to claim 1, wherein the average particle diameter of the mixed powder pyrolyzed in the pyrolysis step is 0.05 μm to 0.6 μm, preferably 0.1 μm to 0.5 μm. A method for producing the carbon dioxide sensor according to the above. 3. The method for manufacturing a carbon dioxide sensor according to claim 1, wherein the acetate contains barium acetate. 4. The method according to claim 1, wherein the acetate contains cerium acetate and copper acetate. 5. A molding step of pulverizing the mixed powder pyrolyzed in the pyrolysis step and then molding it into a predetermined shape, and a baking step of heating and sintering the molded article formed in the molding step. 5. The method for manufacturing a carbon dioxide gas sensor according to claim 1, further comprising: 6. A paste producing step for producing a paste containing the mixed powder thermally decomposed in the thermal decomposing step, and a screen printing of the paste obtained in the paste producing step on an insulating substrate. The method for producing a carbon dioxide sensor according to any one of claims 1 to 4, further comprising a thick film forming step of forming a film. 7. A carbon dioxide gas detecting section comprising one of the sintered body obtained by the method for manufacturing a carbon dioxide sensor according to claim 5 and the thick film obtained by the method for manufacturing a carbon dioxide sensor according to claim 6. And a carbon dioxide gas sensor comprising: at least two current-carrying electrodes disposed on the carbon dioxide gas detection unit. 8. The apparatus according to claim 7, wherein said energizing electrode is provided on one surface of said carbon dioxide gas detecting portion, and at least one or more counter electrodes are provided on a surface facing said one surface. Carbon dioxide sensor.