JPH11326259A - Inorganic composition for carbon dioxide sensor, manufacture of carbon dioxide sensor and carbon dioxide sensor obtained by it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inorganic composition, for a carbon dioxide sensor, by which the detecting sensitivity of carbon dioxide gas at a low concentration is high and by which a capacitance value is stable. SOLUTION: An inorganic composition for a carbon dioxide sensor is an inorganic composition, for a carbon dioxide sensor, which contains CeO2 , BaCO3 and CuO. When CeO2 =A, BaCO3 =B and CuO=C, it has a constitution in which the molar % of A is adjusted to a range of 45<=A<=95, preferably 50<=A<=90 when CuO is set at A+B+C=10 molar %.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a monitor for air pollution in a living space such as a room or a car, a monitor for an air conditioning system, a carbon dioxide concentration control device for transporting and storing fresh foods, and a carbon dioxide concentration in a bio facility. The present invention relates to an inorganic composition for a carbon dioxide sensor used for a monitor system or the like, a method for producing a carbon dioxide sensor using the same, and a carbon dioxide sensor obtained by the method.

[0002]

2. Description of the Related Art In recent years, a carbon dioxide sensor for detecting a carbon dioxide concentration has been used in environmental measurement, facility horticulture, production equipment, and the like. As a carbon dioxide sensor, a measuring method using a detection method using infrared rays, a method using an electrolytic solution, and a method using heat conduction are commercially available, but are large in size and the manufacturing cost is high. For this reason, other methods are being considered,
A method using an alkali ion conductive solid electrolyte such as NASICON using NaCO ₃ as an electrode, a method using a Li ion conductor, a method using a CO ₃₂ -ion conductor such as K ₂ CO ₃ , resistance of hydroxyapatite Research and development of a new type of carbon dioxide sensor using various detection methods, such as a method using a value, has been conducted.

Further, as one of the carbon dioxide sensors capable of miniaturizing the apparatus, the carbon dioxide sensor has a structure in which a sintered body of a mixture of a metal oxide and a carbonate and the like and a pair of electrodes are combined to form a sintered body. There is a method of detecting the concentration of carbon dioxide by changing electrical characteristics such as impedance and capacitance between electrodes by a reversible carbonate formation reaction between the non-composite oxide and carbon dioxide.

For example, Japanese Patent Application Laid-Open No. 4-24548 discloses a "carbon dioxide sensor using a change in capacitance of a mixture of a perovskite-type metal oxide and a non-composite metal oxide". A carbon dioxide sensor using a mixture of non-composite metal oxides ”and JP-A-6-88800 disclose a“ carbon dioxide sensor using a rare earth oxide that is a kind of non-composite metal oxides ”.

[0005] These sensors are, for example, CuO, BaTi
It is manufactured using a commercially available raw material such as O ₃ or a raw material prepared by mixing and then heat treating a commercially available raw material. The raw materials to be used are mixed and pulverized so as to have a predetermined mixing ratio, and then molded and heat-treated to produce a carbon dioxide gas detecting portion main body made of a plate-like carbon dioxide gas sensing ceramic. Thereafter, in order to examine an electrical change accompanying a change in the concentration of carbon dioxide, an electrode portion for extracting an electric signal is manufactured, and a carbon dioxide sensor is obtained. The detection of carbon dioxide is performed by a change in capacitance or a change in impedance. In order to improve the detection performance of these carbon dioxide sensors, addition of a noble metal element or a transition metal element such as Ag is disclosed in JP-A-5-142180, and Ba is disclosed in Japanese Patent Application No. 6-313410.
The addition of O is proposed in Japanese Patent Application No. 7-165053.

[0006]

However, the conventional carbon dioxide gas sensor using a sintered body of a mixture of a non-composite metal oxide and a carbonate has a problem that the detection sensitivity to low-concentration carbon dioxide is small. Was. Also, there is a problem that the capacitance values of the individual carbon dioxide sensors vary widely.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and provides an inorganic composition for a carbon dioxide sensor having a high detection sensitivity for a low concentration of carbon dioxide and a stable capacitance value. It is an object of the present invention to provide an inorganic composition for a carbon dioxide sensor that can be mass-produced at high quality at low cost, a method for manufacturing a carbon dioxide sensor using the same, and a carbon dioxide sensor obtained by the method.

[0008]

Carbon dioxide sensor for inorganic composition of the present invention SUMMARY OF THE INVENTION _is a CeO 2, BaCO _3, carbon dioxide sensor for inorganic composition containing CuO, CeO _2, B
The molar ratio of aCO ₃ and CuO is expressed as CeO ₂ = A, BaCO ₃
= B, CuO = C, and A, B, and C are controlled when A + B + C = 100 mol%.

With this configuration, it is possible to obtain a powder composed of oxides and carbonates having a uniform particle size and reactivity. By using a carbon dioxide gas detection unit of a carbon dioxide gas sensor made of a sintered body using a powder composed of oxides and carbonates having a uniform composition, a uniform particle size and reactivity,
In addition to providing a carbon dioxide gas sensor having high detection sensitivity for carbon dioxide gas and a stable capacitance value, it is possible to realize an inorganic composition for a carbon dioxide gas sensor that can be mass-produced at a low cost with high quality and stable quality.

The method of manufacturing a carbon dioxide gas sensor according to the present invention is characterized in that a mixture of CeO ₂ , BaCO ₃ , and CuO having a controlled molar ratio is used in an amount of 0.3 to 2.5 t / cm ² , preferably 0.5 to ² t. / Cm ^{2 at} a pressure of 750-1
A step of firing at a temperature of 100 ° C, preferably 850 to 1000 ° C.

As a result, the carbon dioxide gas detection sensitivity is high,
A method of manufacturing a carbon dioxide gas sensor capable of efficiently producing a carbon dioxide gas sensor having high quality, stable quality, and excellent mass productivity can be realized.

Further, the carbon dioxide gas sensor of the present invention is provided with a carbon dioxide gas detecting portion comprising a sintered body obtained by wet mixing, pulverizing, molding and firing powders of CeO ₂ , BaCO ₃ and CuO inorganic compositions having a predetermined composition ratio. And an electrode for extracting an electric signal of a capacitance value provided on the carbon dioxide gas detection unit.

With this configuration, the distribution of the inorganic composition constituting the carbon dioxide gas detecting section is uniform, so that the sensitivity of detecting the carbon dioxide gas is high. It is possible to provide a highly reliable carbon dioxide gas sensor having a uniform state and particle density and exhibiting a stable capacitance value and little variation in detection characteristics.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The inorganic composition for a carbon dioxide sensor according to the first aspect of the present invention comprises CeO ₂ , BaCO ₃ , CuO
An inorganic composition for a carbon dioxide sensor containing
The molar ratio of O ₂ , BaCO ₃ , and CuO is expressed as CeO ₂ = A, B
When aCO ₃ = B, CuO = C, and A + B + C = 100 mol%, the mol% of A is in the range of 45 ≦ A ≦ 95, preferably 50 ≦ A ≦ 90. Therefore, the carbon dioxide gas detection sensitivity is high and the capacitance value is stabilized.

Here, as A becomes smaller than 45, the capacitance value of the inorganic composition for a carbon dioxide sensor tends to become unstable, and as it becomes larger than 95, the carbon dioxide detection sensitivity tends to decrease. All of these are undesirable.

In the inorganic composition for a carbon dioxide gas sensor according to a second aspect of the present invention, in the invention according to the first aspect, the mole% of C is in the range of 1.5B ≦ C ≦ 2.5B with respect to B. Accordingly, in addition to the effect obtained by the first aspect of the present invention, there is an effect that the detection sensitivity of carbon dioxide gas can be improved, and in particular, the sensitivity characteristics can be stabilized.

Here, as the mole% of C becomes smaller than 1.5 times B, the detection sensitivity tends to decrease.
Since the sensitivity characteristic tends to become unstable as the ratio becomes larger than 2.5 times, both are not preferable.

According to a third aspect of the present invention, there is provided the inorganic composition for a carbon dioxide gas sensor according to any one of the first and _second aspects, wherein the inorganic composition contains CeO ₂ , BaCO ₃ , and CuO. The particle size of the raw material powder of the inorganic composition is a mixed powder composed of particles having a particle size of 0.1 μm or more and 2 μm or less, whereby the aggregation of the particles can be prevented and the variation in the detection characteristics is suppressed. Has the effect of being able to

Here, as the particle size of the raw material powder becomes smaller than 0.1 μm, the particles tend to agglomerate,
Since the composition distribution tends to increase as the particle size becomes larger than μm, the characteristics tend to vary.

According to a fourth aspect of the present invention, there is provided a method for producing a carbon dioxide gas sensor, wherein the inorganic composition for a carbon dioxide gas sensor according to any one of the first to third aspects is pulverized and then pulverized to 0.3 to 2.5.
t / cm ^2, preferably 0.5～2T / a molding process in which a pressure of cm ² molded into a predetermined shape, 750 to 1100 ° C. The molded product that is molded by the molding step, preferably 850 to
And a sintering step of sintering by heating at a temperature of 1000 ° C., thereby having an effect of stabilizing the capacitance value of the carbon dioxide gas sensor.

A carbon dioxide sensor according to a fifth aspect of the present invention uses the inorganic composition for a carbon dioxide sensor according to any one of the first to third aspects to detect a carbon dioxide gas formed by the method according to the fourth aspect. And an electrode for extracting an electric signal disposed on the carbon dioxide gas detecting section, whereby a carbon dioxide gas sensor having high detection sensitivity and little variation in detection characteristics can be obtained. Has an action.

Hereinafter, specific examples of the embodiments of the present invention will be described with reference to the drawings. Here, CeO ₂ , BaC
An inorganic composition for a carbon dioxide gas sensor containing O ₃ and CuO, wherein the molar ratio of CeO ₂ , BaCO ₃ , and CuO is Ce
O ₂ = A, BaCO ₃ = B, CuO = C, A + B + C
= 100 mol%, the mol% of A is 45 ≦ A ≦
95, preferably an inorganic composition for a carbon dioxide sensor in the range of 50 ≦ A ≦ 90. A method for manufacturing the carbon dioxide sensor configured as described above will be described below.

First, in a mixing and pulverizing step, CeO ₂ , BaCO ₃ , and CuO weighed at a predetermined composition ratio are wet-mixed using a ball mill or the like, pulverized, and dried using a drier or the like to obtain a mixed powder. .

Next, as a molding step, the mixed powder obtained in the mixing and pulverizing step is formed into a predetermined shape such as a plate shape or a comb shape by 0.5 mm.
Mold at a pressure in the range of ２2 t / cm ² .

Next, as a firing step, the molded part molded in the molding step is heated at a temperature of 850 to 1000 ° C. and sintered to obtain a detecting portion of the carbon dioxide gas sensor.

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

As described above, according to the present embodiment, it is possible to obtain a raw material powder for producing an inorganic composition for a carbon dioxide gas sensor having a high carbon dioxide gas detection sensitivity, a high detection speed, and a stable capacitance value. Can be.

By molding and firing the raw material powder, it is possible to easily produce a carbon dioxide gas detecting portion made of an inorganic composition for a carbon dioxide gas sensor having a high carbon dioxide gas detection sensitivity and a high detection speed, and to obtain a high quality carbon dioxide gas. It can be mass-produced at low cost with stable quality.

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

In FIG. 1, reference numeral 1 denotes a carbon dioxide gas detecting portion made of an inorganic composition for a carbon dioxide gas sensor, 2a and 2b denote electrodes,
a and 3b are lead wires.

The carbon dioxide sensor according to the present embodiment is
A carbon dioxide gas detecting section 1, electrodes 2a and 2b for extracting electric signals provided on the carbon dioxide detecting section 1, and lead wires 3a provided on the electrodes 2a and 2b for extracting electric signals;
3b.

Here, the oxides and carbonates of the raw material of the carbon dioxide gas detection unit 1 are wet-mixed and pulverized in a predetermined composition to form a mixed powder composed of particles having a raw material particle size of 0.1 μm or more and 2 μm or less. And a sintered body obtained by firing.

The carbon dioxide sensor in the present embodiment is
It can be obtained by the method for producing an inorganic composition for carbon dioxide gas in the first embodiment. The electrodes 2a and 2b may be made of any material that does not deteriorate at the operating temperature and has a small resistance.
The paste can be formed by screen printing a paste containing any of t, RuO ₂ , Ag 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. Can be detected by measuring the electrical characteristics of the 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, a high detection speed, and a stable capacitance value.

[0036]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The first embodiment of the present invention will be described below with reference to the first embodiment.
This will be described in detail with reference to Comparative Examples 1 to 10.

(Examples 1 to 15 and Comparative Examples 1 to 10) Barium carbonate, cerium oxide and copper oxide of analytical grade purity were weighed so that the total amount was 100 g in the composition ratio of (Table 1), and then the container was prepared. The mixture was added to 80 ml of ethanol, mixed and pulverized using a ball mill, and dried at 80 to 13 using a drier.
The mixed powder obtained by drying at 0 ° C. was pressed with a press machine at a pressure of 0.5 t / cm ² at a diameter of 20 mm and a thickness of 0.5 m.
m was molded into a disk shape. The obtained molded body was fired in an electric furnace at 850 ° C. for 5 hours. A commercially available ruthenium oxide paste of analytical grade purity was applied in a circular shape on both surfaces of the fired sample, and heat-treated at 900 ° C. for 10 minutes to produce an electrode portion. Using a cutting machine, this sample was 1.6 mm × 1.1.
It was cut into a size of 5 mm × 0.5 mm, and a platinum wire was attached to both surfaces of the ruthenium oxide electrode using a commercially available ruthenium oxide paste of analytical grade purity to form a lead wire, which was then heat-treated at 850 ° C. for 10 minutes.

The carbon dioxide sensors manufactured as described above were referred to as first to fifteenth examples and first to tenth comparative examples.

(Comparative Example 11) As in the first embodiment,
Barium carbonate, cerium oxide, and copper oxide having a commercial analytical purity were weighed at a composition ratio of 70:10:20 so that the total amount was 100 g, then transferred to a container, mixed and pulverized using a ball mill, and the resulting mixture was obtained. The powder was placed in a 0.
It was molded into a disk having a diameter of 20 mm and a thickness of 0.5 mm under a pressure of 5 t / cm ² . The obtained molded body was fired in an electric furnace at 850 ° C. for 5 hours. An electrode was formed on this sintered body in the same manner as in the first embodiment, cut, and a lead wire was formed.

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

Each of the carbon dioxide sensors was placed in an electric furnace adjusted to 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)
(A type), the capacitance component between the lead wires at a frequency of 10 kHz was measured by a two-terminal method. The capacitance component, dry air or dry air containing 2% carbon dioxide gas was passed through the electric furnace until the value reached a substantially constant value, and the capacitance component was determined when the value reached the constant value.

The detection state of the carbon dioxide gas is based on the capacitance value (C _air ) of the sample heated to the measurement temperature measured in a state where the air is introduced, and the air inlet adjusted to the carbon dioxide gas concentration of 2%. It is captured by the change in the capacitance value (C _2% ) when the measurement is performed. The sensitivity is defined by the following equation.

Sensitivity = | 10 × Log (C _2% / C _air ) | [dB] The larger the numerical value, the better the sensitivity. When the sensitivity is 0, it indicates that the capacitance value does not show a change with respect to an increase in the concentration of carbon dioxide, and no carbon dioxide is detected. The sensitivity characteristics 10 of Examples 1 to 15 and Comparative Examples 1 to 5 are shown in (Table 1).

[0044]

[Table 1]

As is clear from Table 1, in this example, the sensitivity was 5 dB or more, and at that time, the composition ratio of CeO ₂ was found to be in the range of 50 to 90.

It is considered that one of the reasons for the high detection sensitivity is that the characteristic of cerium oxide having a catalytic action in the inorganic composition for a carbon dioxide sensor works most effectively in this range. .

(Evaluation Example 2) In order to compare the performances of the carbon dioxide gas sensors in the fifth to eighth and eleventh embodiments and the sixth to tenth comparative examples, 100 sensors were manufactured and measured in the same manner as in (Evaluation Example 1). The average value of the sensitivity characteristics and the standard deviation of each were calculated from the measured sensitivity characteristics, and the range of sensitivity variation is shown in Table 2. In addition, the fifth to eighth and eleventh embodiments and the sixth embodiment
In order to compare the detection speeds of the carbon dioxide gas sensors of Comparative Examples 10 to 10, when the carbon dioxide gas concentration was changed, the time required for the characteristic change amount to become 90% of the total change amount was defined as "90% detection time" ( The results are shown in Table 2).

[0048]

[Table 2]

As is clear from Table 2, in the composition of the inorganic composition for a carbon dioxide gas sensor as in this example, 1.
In the range of 5B ≦ C ≦ 2.5B, the variation in sensitivity is small when the detection sensitivity is 5 dB or more. However, it is clear that the detection sensitivity is reduced and the variation is increased when the sensitivity exceeds this range.

It was also found that the same applies to the 90% detection time. This is, for C <1.5B,
It is considered that the detection mechanism is slowed down due to excessive barium carbonate. When C> 2.5B, it is considered that the detection sensitivity is lowered due to an excessively small amount of barium carbonate, and the resistance of the inorganic composition for a carbon dioxide gas sensor is decreased due to an excessive amount of copper oxide, which makes the characteristics unstable.

(Evaluation Example 3) 100 carbon dioxide sensors of the fifth embodiment and the eleventh comparative example were manufactured, respectively (Evaluation Example 1).
The capacitance value in air was measured in the same manner as described above. In addition, the particle size of each raw material powder is measured using a particle size distribution analyzer (H
The laser diffraction / scattering type particle size distribution measuring apparatus (LA-700, manufactured by ORIBA) was used. The respective standard deviations were calculated from the measured capacitance values, and the range of variation of the capacitance values and the particle size distribution of the raw materials were summarized in (Table 3).

[0052]

[Table 3]

As apparent from Table 3, the eleventh comparative example in which the dry mixing was performed showed that the capacitance value distribution range was 30%.
In the fifth embodiment in which the wet mixing was performed, the range was 8.3%, which was smaller than that in the case where the ratio exceeded 8.3%. In addition, the particle size distribution of the raw material is also wide in the eleventh comparative example as 1.8 to 12 μm,
In the first example, it was clarified that the particles were composed of 0.1 to 2 μm particles. This is considered to be because the properties of the sintered body are stabilized because the raw material is uniformly pulverized by performing the wet mixing, and the composition distribution in the raw material becomes very uniform due to the small particles. The diffusion of carbon dioxide gas is also considered to be one of the factors that increase the detection sensitivity because the diffusion speed is high and constant because the grain boundaries in the carbon dioxide gas detection unit are uniform.

The sensitivity characteristics of the fifth embodiment and the eleventh comparative example were measured in a more practical carbon dioxide gas concentration region. The carbon dioxide gas concentration was set to Air to 5000 ppm.

Air to 5 of the fifth embodiment and the eleventh comparative example
The sensitivity characteristics at 000 ppm are shown in FIG.

As apparent from FIG. 2, the sensitivity in the concentration range of 500 to 3000 ppm is low in the eleventh comparative example in which the dry mixing is performed, whereas the sensitivity in the concentration range of 500 to 3000 ppm is low in the fifth embodiment in which the wet mixing is performed. It turned out that it shows about twice the sensitivity.

This is also considered to be due to the fact that the effective particle surface area of the carbon dioxide gas detection part is larger than in the prior art due to the reduced particle size of the raw material, so that high sensitivity is exhibited even when the carbon dioxide gas concentration is low. Can be

(Evaluation Example 4) Fifth Embodiment and First and Eleventh Embodiments
After leaving each of the carbon dioxide sensors of the comparative examples in a thermo-hygrostat adjusted to 85 ° C. and 90% Rh for 1000 hours, the detection sensitivity of the carbon dioxide gas was determined in the same manner as in (Evaluation Example 1). These values are summarized in (Table 4).

As a result, in the carbon dioxide gas sensors of the first and eleventh comparative examples, the detection sensitivity was reduced by 18.4% and 16.3% as compared with that before leaving for 1000 hours.
In the carbon dioxide gas sensor of the embodiment, the decrease in the detection sensitivity is 5.1%.
It was found that the carbon dioxide sensor of the present invention was improved in moisture resistance as compared with the conventional example.

(Evaluation Example 5) Fifth Embodiment and First and Eleventh Embodiments
After leaving each of the carbon dioxide sensors of the comparative examples in an electric furnace adjusted to 550 ° C. for 1000 hours, the detection sensitivity of carbon dioxide was determined in the same manner as in (Evaluation Example 1).

These values are summarized in (Table 4).

[0062]

[Table 4]

As a result, in the carbon dioxide gas sensors of the first and eleventh comparative examples, the detection sensitivity was reduced by 13.4% and 10.6% as compared with that before leaving for 1000 hours.
In the carbon dioxide sensor of the embodiment, the decrease in the detection sensitivity is 2.9%.
And extremely small, the carbon dioxide sensor of the present invention is durable,
It was also found that the life characteristics were improved as compared with the conventional example.

As described above, in order to improve the moisture resistance of (Evaluation Example 4), the durability and the life characteristics of (Evaluation Example 5), cracks are formed in the carbon dioxide gas detecting portion because the particles are composed of particles having uniform reactivity. This is considered to be due to the fact that the adhesiveness between the carbon dioxide gas detecting portion and the electrode is improved due to the fact that the carbon dioxide gas is less affected by moisture and heat and the particle state is constant.

[0065]

As described above, according to the present invention, the following excellent effects can be realized.

According to the inorganic composition for a carbon dioxide sensor of the first aspect of the present invention, a carbon dioxide gas sensor having high sensitivity for detecting carbon dioxide and having a stable capacitance value is provided, and high quality, stable quality and low cost are provided. Thus, an inorganic composition for a carbon dioxide gas sensor that can be mass-produced can be realized.

According to the inorganic composition for a carbon dioxide sensor according to the second aspect of the present invention, in addition to the effects obtained by the first aspect, the detection sensitivity of the carbon dioxide gas is improved, and particularly the sensitivity characteristics are stabilized. The effect that it can be obtained is obtained.

According to the inorganic composition for a carbon dioxide sensor of the third aspect of the present invention, in addition to the invention of any one of the first and second aspects of the present invention, aggregation of particles can be prevented. In addition, the effect of suppressing variations in detection characteristics can be obtained.

According to the method for producing an inorganic composition for a carbon dioxide gas sensor according to the fourth aspect of the present invention, a carbon dioxide gas sensor having high sensitivity for detecting carbon dioxide, high quality, stable quality and excellent mass productivity can be efficiently produced. A method of manufacturing a carbon dioxide sensor that can be produced can be realized.

According to the carbon dioxide sensor according to the fifth aspect of the present invention, since the distribution of the inorganic composition constituting the carbon dioxide sensing portion is uniform, a highly reliable carbon dioxide sensor having little variation in detection characteristics is provided. An excellent effect of being able to provide and improving the reliability of the carbon dioxide sensor is obtained.

[Brief description of the 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 characteristic comparison diagram in a third evaluation example of the present invention.

[Explanation of symbols]

 1 Carbon dioxide detector 2a, 2b Electrode 3a, 3b Lead wire

Claims (5)

[Claims] An inorganic composition for a carbon dioxide sensor containing CeO ₂ , BaCO ₃ , and CuO, wherein the inorganic composition is CeO ₂ , BaC
The molar ratios of O ₃ and CuO are expressed as CeO ₂ = A, BaCO ₃ =
B, when CuO = C and A + B + C = 100 mol%, the mol% of A is 45 ≦ A ≦ 95, preferably 50
An inorganic composition for a carbon dioxide gas sensor, wherein satisfies the range of ≦ A ≦ 90. 2. The inorganic composition for a carbon dioxide sensor according to claim 1, wherein, in the molar ratio B + C, the molar percentage of C is in the range of 1.5B ≦ C ≦ 2.5B with respect to B. 3. The raw material powder of the inorganic composition for a carbon dioxide gas sensor containing CeO ₂ , BaCO ₃ , and CuO has a particle size of 0.1.
The inorganic composition for a carbon dioxide sensor according to any one of claims 1 and 2, wherein the inorganic composition is at least 1 micron and at most 2 microns. 4. An inorganic composition for a carbon dioxide sensor according to claim 1, wherein said inorganic composition is 0.3 to 2.5 t / c.
m ² , preferably a molding step of molding into a predetermined shape at a pressure of 0.5 to ² t / cm ² , and a molded article molded in the molding step is 750 to 1100 ° C., preferably 850 to 100 ° C.
A firing step of sintering by heating at a temperature of 0 ° C. 5. A carbon dioxide gas detecting section formed by the method according to claim 4 using the carbon dioxide sensor inorganic composition according to any one of claims 1 to 3, and provided in the carbon dioxide gas detecting section. And an electrode for extracting an electric signal.