JPH1073560A - Carbon dioxide gas sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a carbon dioxide gas sensor in which the output is settled in a short time, fluctuation of output is suppressed even after long term use and a solid electrolytic plate is prevented from being stripped from a metal carbonate layer. SOLUTION: The carbon dioxide gas sensor 1 incorporates a heating element 20 and comprises an alumina substrate 10 provided with a recess 14 in one major surface thereof, a reference electrode 30 formed on the bottom face of the recess a solid electrolytic element 40 mounted thereon, a grid-like detection electrode 50 formed on the surface thereof, and a metal carbonate layer 60 covering the detection electrode 50. The gap between the solid electrolytic element 40 and the circumferential wall of the recess is filled with a glass sealant 70.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to the for measuring the concentration of carbon dioxide in the gas phase (CO ₂ gas), carbon dioxide gas sensor using a solid electrolyte, and in particular carbon dioxide sensor of the concentration cell type. The carbon dioxide sensor of the present invention can be used for measurement of carbon dioxide concentration and concentration control based on the measurement result in a wide range of technical fields such as environmental control, medical technology, facility horticulture, and fermentation industry.

[0002]

2. Description of the Related Art A concentration cell type carbon dioxide sensor using a solid electrolyte element having sodium ion conductivity has been known. The basic configuration is such that a reference electrode and a detection electrode are provided on both sides of a solid electrolyte element which is an ion conductor, and the detection electrode is coated with sodium carbonate or the like.
When measuring the concentration of carbon dioxide using this conventional concentration cell type carbon dioxide sensor, the heater is heated to a constant temperature and the electromotive force generated between the detection electrode and the reference electrode is measured.

In this concentration cell type carbon dioxide gas sensor, in order to maintain the measurement accuracy and stability, it is necessary to have a structure in which the reference electrode side is shut off so as not to come into contact with the outside air or the gas to be measured. As having such a blocking structure,
For example, Japanese Unexamined Patent Publication No. 60-256043 discloses that a metal salt layer is formed by baking a part of the surface of a solid electrolyte on which a metal electrode is formed, and the remaining part of the surface is hermetically coated with a heat-resistant inorganic coating agent. The disclosed structure is disclosed. In Japanese Patent Application Laid-Open No. 5-80021, a sodium ion conductor having a reference electrode and a detection electrode formed on both surfaces is disposed on a ceramic substrate provided with a heater on the back surface, and the side surface is made of glass or the like. A structure sealed by covering with a cover is disclosed.

[0004]

However, in the conventional shut-off structure, since the shut-off member such as a coating agent or a cover is externally attached to the solid electrolyte element, an area where the shut-off member itself comes into contact with the outside air. Therefore, there is a possibility that cracks may occur in the blocking member, or separation may occur at the interface with the solid electrolyte due to long-term use under heating. Also,
Poor heat retention due to large area in contact with outside air,
The temperature stability of the solid electrolyte cannot be obtained. As a result, there is a problem that the output becomes unstable or fluctuates.

[0005] The metal carbonate provided on the sensing electrode generally has an anisotropic coefficient of thermal expansion and does not have high sinterability. Therefore, if the temperature increase and the temperature decrease are repeated many times, the bonds between the particles become weak, and minute cracks and the like are generated, so that the metal carbonate apparently expands. As a result, the contact state between the sensing electrode and the metal carbonate changes, the characteristics of the sensor become unstable, and when used for a long time, the metal carbonate peels off from the sensing electrode and loses its function as a sensor. There are also problems.

The present invention has been made to solve the above problems, and effectively shuts off the reference electrode side of an ion conductor made of a solid electrolyte from outside air or a test gas, enhances heat retention, and reduces output variations. It is an object of the present invention to provide a concentration cell type carbon dioxide gas sensor in which power consumption for heating is reduced and power consumption for heating is reduced.

[0007]

According to a first aspect of the present invention, there is provided a carbon dioxide gas sensor comprising a base including a heating element, a reference electrode, an ion conductor layer made of a solid electrolyte, a detection electrode, and a metal carbonate layer. Are formed in this order, and the ion conductor layer is disposed in a recess provided on one main surface of the base.

[0008] The invention according to a second aspect of the present invention relates to a carbon dioxide gas sensor.
A reference electrode, an ion conductor layer made of a solid electrolyte, a detection electrode, and a metal carbonate layer are formed in this order on a base body containing a heating element, and the ion conductor layer, the detection electrode, and the metal carbonate layer are formed in this order. The salt layer is disposed in a depression provided on one main surface of the base.

According to a third aspect of the present invention, there is provided a carbon dioxide gas sensor.
3. The carbon dioxide sensor according to claim 1, wherein a gap between the ion conductor layer and a peripheral wall of the recess is filled with a sealing material. 4. At this time, it is preferable that a distance between the ion conductor layer and the peripheral wall of the depression is in a range of 0.05 to 1.0 mm (claim 4).

According to a fifth aspect of the present invention, there is provided a carbon dioxide gas sensor.
The carbon dioxide sensor according to claim 3, wherein the sealing material is an amorphous glass or a crystallized glass. At this time, the amorphous glass is CaO—BaO
Is preferably -SiO ₂ based glass (claim 6). Further, the crystallized glass is made of SiO ₂ -BaO-A.
l is preferably ₂ O ₃ based crystallized glass (claim 7). Further, it is preferable that the sealing material contains 80% by volume or less of particles made of the same material as the solid electrolyte (claim 8). Further, it is preferable that an alkali metal component contained in the sealing material is not more than 5% by weight in terms of oxide (claim 9).

When both the amorphous glass and the crystallized glass are used in combination, it is preferable that the reference electrode is made of amorphous glass and the detection electrode is made of crystallized glass. The volume ratio of the amorphous glass is preferably 50 to 98% by volume, and the volume of the crystallized glass is preferably 50 to 2% by volume (claim 11). Furthermore, it is preferable that the softening point of the amorphous glass is higher than the softening point of the crystallized glass.

According to a thirteenth aspect of the present invention, there is provided the carbon dioxide sensor according to the first or second aspect, wherein the solid electrolyte is a Li ion conductive solid electrolyte. At this time, a particularly preferred solid electrolyte is one having LiSmSiO ₄ as a main crystal phase (claim 14). Moreover, other ones containing Al ₂ O ₃ to (claim 15) of the LiSmSiO ₄ wherein the solid electrolyte is a main crystalline phase, or those containing ZrO ₂ is a major crystalline phase in addition to the LiSmSiO ₄ (Claim 16) is preferred.

When the solid electrolyte is a Li ion conductive solid electrolyte, the metal carbonate layer is formed of lithium carbonate (Li ₂ CO ₃ ) or lithium carbonate and an alkaline earth metal carbonate (eg, CaCO _3). , BaCO _3, etc.) as a main component (claim 17). further,
At this time, it is preferable that at least a portion of the reference electrode in contact with the ion conductor layer is made of Au (claim 18).

According to a nineteenth aspect of the present invention, there is provided the carbon dioxide sensor according to the first or second aspect, wherein the solid electrolyte is a Na ion conductive solid electrolyte. At this time, a particularly preferred solid electrolyte is NASICON (Na _{1 + X} Zr ₂ Si _X
P _{3 −X} O ₁₂ , 0 ≦ X ≦ 3) is the main crystal phase. Further, it is preferable that the solid electrolyte contains ZrO ₂ in addition to the NASICON which is a main crystal phase (Claim 21).

When the solid electrolyte is a Na ion conductive solid electrolyte, the metal carbonate layer is made of lithium carbonate (Li ₂ CO ₃ ) or lithium carbonate and an alkaline earth metal carbonate (eg, CaCO _3). , BaCO _3, etc.) as a main component (claim 22). further,
At this time, it is preferable that at least a portion of the reference electrode in contact with the ion conductor layer is made of Pt (claim 23).

According to a twenty-fourth aspect of the present invention, there is provided the carbon dioxide gas sensor according to the first or second aspect, wherein the detection electrode is made of Au. Further, the invention according to a carbon dioxide sensor of claim 25 is as follows:
2. The carbon dioxide sensor according to claim 1, wherein a surface of the ion conductor layer on the side of the detection electrode is flush with one main surface of the base. 3.

According to a twenty-sixth aspect of the present invention, there is provided the carbon dioxide gas sensor according to the first or second aspect, wherein the heating element is viewed from a direction perpendicular to the one main surface of the base. When the area occupied by the effective heat generating portion is 1, the area of the ion conductor layer is 0.05 to 1.30.
It is characterized by being.

According to a twenty-seventh aspect of the present invention, there is provided the carbon dioxide gas sensor according to the first or second aspect, wherein each wiring led out to the surface or side surface of the base from the heating element, the reference electrode, and the detection electrode. It is characterized in that it is indirectly attached to the pedestal via an end and a conductive connecting member. At this time, when viewed from a direction perpendicular to the one main surface of the base, the occupied area of the effective heat generating portion of the heat generating body is 1
It is preferable that the area of the substrate is 1.1 to 3.

According to a twenty-ninth aspect of the present invention, there is provided the carbon dioxide gas sensor according to the first or second aspect, wherein the open porosity of the solid electrolyte is 15% or less on a volume basis. . The invention according to claim 30 is the carbon dioxide sensor according to claim 1 or 2, wherein a metal net is provided in the metal carbonate layer.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As described above, a carbon dioxide sensor (hereinafter, also simply referred to as a "sensor") according to the present invention comprises a base having a heating element built therein, a reference electrode, an ion conductor layer made of a solid electrolyte, A detection electrode and a metal carbonate layer are formed in this order, and the ion conductor layer, or a depression portion in which the detection electrode and the metal carbonate layer are provided on one main surface of the base in addition to the ion conductor layer; Is a basic configuration.

When this sensor is placed in a measurement gas atmosphere and the heating element is energized, the following reactions occur at the reference electrode and the detection electrode. Detecting electrode _{side: M 2 CO 3 ← → 2M} + + (1/2) O 2 + 2
e ⁻ + O ₂ reference electrode side: 2M ⁺ + (1/2) O ₂ + 2e ⁻ ← → M ₂ O In the above formula, M is an alkali metal. as a result,
Since an electromotive force that changes linearly according to the logarithmic value of the carbon dioxide partial pressure in the measurement atmosphere is generated between the detection electrode and the reference electrode, the measurement of the electromotive force allows the measurement of the carbon dioxide gas in the atmosphere. The concentration can be measured.

The above-mentioned "substrate" serves as a support constituting the outer shape of the sensor, supports the overall mechanical strength, and has excellent electrical insulation and heat resistance. Desirably, for example, those made of ceramics such as alumina having relatively high rigidity and excellent insulation properties are preferable. The base is flat, rod-shaped, cylindrical,
Various shapes such as a cylindrical shape can be used, but the shape is not particularly limited to these.

Further, in the present invention, a depression is provided on one main surface of the base, which serves as a carbon dioxide gas detection site.
This recess has a shape and size capable of accommodating the ion conductor layer composed of the solid electrolyte with a certain interval, and is formed so that its depth is substantially the same as the thickness of the ion conductor layer. Have been. The reference electrode and the ion conductor layer are accommodated in the recess and sealed with a sealing material, so that the reference electrode and the ion conductor layer are buried in the base body, thereby shutting off the outside air (test gas). In addition to ensuring the heat resistance, the heat retention is also excellent. In addition, with the structure having the recessed portion as described above, the amount of the sealing material to be filled can be reduced and the exposed area can be reduced, so that cracking failure and deterioration of the sealing portion can be suppressed. . Further, since the portion to be filled is the recessed portion, it is possible to use a sealing material having high fluidity at the time of filling.

As the above-mentioned "heating element", a planar heater or the like capable of heating the entire solid electrolyte constituting the ion conductor layer to a temperature in the range of about 200 to 800 ° C. and holding the same uniformly is preferably used. be able to. For example, a substrate in which a heating element made of platinum or the like is provided on one surface of or inside a substrate made of ceramic such as alumina and at a portion corresponding to the position where the recess is formed. In addition, as the heating element, platinum, rhodium, a platinum-rhodium alloy, a nickel-chromium alloy, tungsten, molybdenum, or the like is formed on one side of a sheet made of an insulating material by a sputtering method, an evaporation method, a plating method, a paste baking method, or the like. Formed in a long strip shape, and an insulating material can be laminated thereon.

The above-mentioned "reference electrode" can be formed by printing a conductor paste, for example, a commercially available gold paste on one surface of an ion conductor layer made of a solid electrolyte, and baking the paste at a temperature of about 900 ° C. for 10 minutes. . Further, this reference electrode may be formed using platinum, may be formed by a vapor deposition method, a sputtering method, or the like in addition to a printing method, or may be formed in a thick film by a coating and baking method.

The "ion conductor layer" is composed of a solid electrolyte. The solid electrolyte is preferably one having a conductive species of either an alkali metal ion or an alkaline earth metal ion, and more preferably a lithium ion or a sodium ion. As a solid electrolyte using lithium ions as a conductive species, for example, LISICON (Lithium Super Ionic)
Conductor), LiAlSiO _4, LiLnSiO ₄
(Ln; lanthanide element such as Sm, La, Nd, etc.), Li _3.6 Si _0.6 P _0.4 O ₄ and LiTi ₂ (PO ₄ )
₃ or the like can be used. Of these, LiLnSiO ₄ is particularly preferable, and S is used as a lanthanide element.
When m is selected, that is, LiSmSiO ₄ is used as the main crystal phase. In the above-mentioned lithium ion conductive solid electrolyte, in addition to the main crystal phase, Al ₂
O ₃ or ZrO ₂ may be contained. This is because by containing these, the mechanical strength of the solid electrolyte itself is improved, and a sensor which is less affected by humidity is obtained as a characteristic of the sensor.

On the other hand, examples of solid electrolytes using sodium ions as conductive species include, for example, Na _{1 + X} Zr ₂ Si _X P _{3 -X} O ₁₂ (0 ≦ X ≦ 3), and beta alumina ( Na ₂ O · nAl ₂ O ₃ , 5 ≦ n ≦ 11) or the like is used, but NaAlSi ₃ O ₁₀ , NaAlSi ₄ O
₁₀ mag can also be used. Among them, NASICON (particularly, X = 2 in the above general formula) is used as the main crystal phase. The sodium ion conductive solid electrolyte may contain ZrO ₂ in addition to the main crystal phase. This is because, by containing these, changes in sensor output due to humidity, that is, humidity dependency can be reduced.

The humidity dependency also changes depending on the amount of open pores in the ion conductor layer made of these solid electrolytes. The smaller the amount of open pores, the more the humidity dependency can be reduced. Specifically, the open porosity is 15 by volume.
%, Preferably 10% or less.
Or less, particularly preferably 2% or less. Further, the total pore volume of the open pores is 0.05 cc / g or less, especially 0.03 c / g.
It is preferably at most c / g. These pore characteristics can be measured using, for example, a mercury intrusion type pore distribution measuring device (porosimeter).

The "detection electrode" is formed by printing a conductive paste on the surface of the solid electrolyte or by sputtering or vapor-depositing a conductive material, and has a mesh shape (net shape) having openings. A film formed as a film is preferred. In this way, the metal carbonate layer and the ion conductor layer can be in close contact with each other at the opening of the detection electrode, so that the metal carbonate layer is securely and firmly joined to the solid electrolyte that is the ion conductor layer. The fabricated sensor can be manufactured.

The above-mentioned "metal carbonate layer" can be formed using an alkali metal or alkaline earth metal carbonate such as lithium carbonate, sodium carbonate and calcium carbonate. Specifically, if necessary, these carbonates are replaced with water,
It is appropriately mixed with a solvent such as alcohol and an organic binder to form a paste or a solution, and then applied to the surface of the ion conductor layer on which the detection electrodes are formed or arranged, dried, and fired at a required temperature. Can be formed.

In order to prevent peeling of the metal carbonate layer due to repeated use of heating and cooling for a long period of time, a metal mesh is arranged and fixed on the detection electrode, and the metal mesh is embedded so that the metal mesh is embedded. It is preferable to form a salt layer. The material of the metal net is preferably made of a noble metal such as Au or Pt. The metal mesh does not necessarily need to be in contact with the detection electrode, but is desirably fixed to a part of the solid electrolyte element or the base. The shape such as the opening width and the wire diameter of the metal mesh is not particularly limited, and a commercially available metal mesh can be used as appropriate.

As the above “sealing material”, amorphous glass or crystallized glass can be preferably used. Further, as the amorphous glass, in particular, CaO—BaO—SiO
_As the crystallized glass, SiO ₂ —Ba is used as the crystallized glass.
O-Al ₂ O ₃ based crystallized glass can be preferably used. These include the above-mentioned oxide components as essential components, but may contain other components within a range that does not significantly affect the softening point, the thermal expansion characteristics, and the like.
At this time, each glass contains 80 vol% or less of particles made of the same material as the solid electrolyte (particularly, 10 to 80% when the solid electrolyte is a Li ion conductive solid electrolyte).
% By volume) is more preferable. This is because, by containing in the above range, the difference in thermal expansion between the sealing material and the solid electrolyte is reduced, and there is an effect of preventing the sealing portion from being cracked or peeled off. It is particularly preferable that the content of the alkali metal component (for example, Na or K) contained in each of the glasses is 5% by weight or less in terms of oxide. If the content exceeds 5% by weight, the alkali metal component in the glass reacts with the solid electrolyte or the metal carbonate to affect the durability of the sensor.

When the above glass is used as a sealing material, both amorphous glass and crystallized glass can be used in combination. In this case, of the gap between the ion conductor layer and the peripheral wall of the depression, the portion on the reference electrode formation side as viewed in the depth direction of the depression is sealed with amorphous glass, and the portion on the detection electrode formation side is crystallized. It is preferable to seal with glass frit, but it is preferable that at least a portion of the gap where a wiring for a detection electrode derived from a detection electrode described later is formed is sealed with crystallized glass. This is to prevent disconnection of the wiring due to softening / flow of the sealing material due to heat treatment at the time of forming the detection electrode and the wiring for the detection electrode. The volume ratio of the two glasses is 50% when the total is 100% by volume.
９８98% by volume and crystallized glass can be preferably used in the range of 50５０2% by volume. When the amount of the amorphous glass is less than the above range, the airtightness for blocking the reference electrode from the outside air or the test gas is likely to be insufficient. This is because the heat treatment causes the sealing material to flow easily, which causes electrical conduction failure of the detection electrode.

Further, in the above case, the softening points of the amorphous glass and the crystallized glass are higher than the temperature (350 to 500 ° C.) heated by the heating element when the sensor is used. Preferably, the softening point of the glass is higher than the softening point of the crystallized glass. This is to prevent the flow of the sealing material during the use of the sensor and the flow of the amorphous glass during the firing treatment of the crystallized glass, and to secure sufficient airtightness and electrical conduction of the electrodes.

In the carbon dioxide gas sensor according to the present invention, the surface of the ion conductor layer on the side of the detection electrode is preferably on the same plane as one main surface of the substrate provided with the depressions. It is also preferable that the upper surface of the sealing material filled around is also on the same plane as above. With this configuration, the formation of the detection electrode and the formation of the wiring for the detection electrode can be simultaneously performed by the thick film method, so that there is an advantage that the productivity is excellent and the production becomes easy.

The carbon dioxide sensor of the present invention is usually used for measurement in a form where it is fixed to a pedestal at a connection portion with a lead wire and further covered with a protective cap having a ventilation hole. During measurement, it is necessary to keep the temperature in a certain temperature range.However, if the base and the pedestal are directly fixed, there is a loss due to the transmission of heat from the base to the pedestal and the protective cap. Disadvantageous. In addition, the heat loss tends to increase as the volume of the base itself increases.

Therefore, according to the present invention, in the carbon dioxide gas sensor having the above-described basic configuration, the dimensions of the substrate other than the detection site are reduced as much as possible, and the surface or side surface of the substrate is separated from the heating element, the reference electrode and the detection electrode. It is preferable to indirectly attach the respective wiring ends and the pedestal led out to the base via a conductive connecting member. In this case, the sensor is held in a suspended state from the pedestal and the protective cap by the connecting member, and the escape of heat from the sensor to the pedestal and the like is mostly due to heat radiation, so that heat loss is small. This is very effective in reducing power consumption. At this time, at least a connecting portion of the connecting member with each of the wiring ends of the base has a diameter of 0.05 to 1.0 mm or a metal wire having a cross-sectional area corresponding thereto, for example, a platinum wire or a stainless steel wire. And the like.
Further, when viewed from a direction perpendicular to the one main surface of the base, it is preferable that the area of the base is 1.1 to 3 when the occupied area of the effective heat generating portion of the heat generating element is 1. . If it is less than 1.1, the heating element may be exposed, and if it exceeds 3, the effect of reducing the heat loss cannot be largely obtained.

[0038]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the drawings. The carbon dioxide sensor of the present invention is not necessarily limited to the one obtained by the structure and the manufacturing method described herein.

Example 1 FIG. 1 is a front view of a carbon dioxide sensor according to Example 1, and FIG.
FIG. 2 is a cross-sectional view schematically showing a cross section taken along line AA ′ of FIG. 1. FIG. 3 is a cross-sectional view schematically showing a cross section taken along line BB ′ of FIG. 1, but the terminal pin side is omitted. The carbon dioxide sensor 1 of this embodiment has a heating element 20 inside.
And a base 10 made of an alumina substrate having a depression 14 on one main surface 15, and the depression 1
4, a reference electrode 30 formed on the bottom surface, a solid electrolyte element 40 mounted thereon, a grid-like detection electrode 50 formed on the surface thereof, and a metal carbonate provided so as to cover the detection electrode 50. The layer 60 has a basic configuration. Furthermore, in order to prevent contact between the reference electrode 30 and the test gas, a sealing material 70 filled around the solid electrolyte element 40 is connected to the reference electrode 30 and the detection electrode 50, respectively. Terminal pins 81 and 82 and terminal pins 83 and 84 for the heating element for supplying electricity to the heating element 20 are provided, respectively.

The above carbon dioxide sensor was manufactured as follows. First, a substrate 10 made of alumina ceramic having a heating element built therein is manufactured by a green sheet laminating method. As shown in FIG. 1, the base 10 has a three-layer structure, and a heating element 20 made of Pt is formed between the first layer 11 and the second layer 12. Further, a part of the third layer 13 is removed by punching or the like, and the third layer 13 is laminated on the second layer to have a depth corresponding to the thickness of the third layer (0.25 mm in this embodiment). The recess 14 is formed. Further, between the second layer and the third layer, a reference electrode wiring 31 made of Pt for electrically connecting the reference electrode 30 and the output terminal pin 81 is formed.

Next, as the solid electrolyte element 40, 900
° C. 5 The Al ₂ O ₃ powder synthesized LiSmSiO ₄ powder
0% by weight, mixed and molded.
2.5 × 2.5 × 0.25m thick, fired at 50 ° C
m of a plate-shaped sintered body was prepared. Then, an Au paste serving as a reference electrode is applied to one surface of the plate-shaped solid electrolyte element 40, and an end of the reference electrode wiring 31 led to the recess 14 overlaps with the Au paste application portion. This is heat-treated at 1030 ° C. with the solid electrolyte element 40 and the substrate 1 interposed via the reference electrode 30.
0 was adhered.

Next, in the gap formed between the solid electrolyte element 40 and the peripheral wall of the concave portion 14, Ca
O: 14% by weight, BaO: 25% by weight, SiO ₂ : 45
% By weight, B ₂ O ₃ : 7% by weight, Al ₂ O ₃ : 6% by weight, Zn
O: amorphous glass having 2% by weight (coefficient of thermal expansion: 66)
(× 10 ⁻⁷ / ° C.) and a mixture obtained by adding 50% by volume of LiSmSiO ₄ powder to the powder is filled up to 80% of the depth of the depression.
Heat treatment was performed at 1000 ° C. to fuse the glass. Further, SiO ₂ : 42% by weight, BaO: 16% by weight, A
l ₂ O ₃ : 15% by weight, ZnO: 10% by weight, CaO: 9
Wt%, MgO: 3 wt%, ZrO _2: 3 by weight%, Na ₂
O: filled with powder for crystallized glass having 2% by weight and 93
Heat treatment was performed at 0 ° C. to crystallize. At this time, the crystallized glass is filled with the exposed upper surface after the heat treatment.
The amount was adjusted so as to be flush with one main surface or slightly convex. By this sealing step, the reference electrode 30 is cut off from the outside and the solid electrolyte element 4
0 was firmly fixed to the substrate 10.

Next, an Au paste for forming a detection electrode is applied on the solid electrolyte element 40, and a detection electrode 50 is formed by a thick film method. This detection electrode was formed into a mesh by performing screen printing using an appropriate opening pattern. If the surface of the solid electrolyte on the sensing electrode side is on the same plane as one main surface of the base or the exposed surface of the sealing material, it may be performed as it is, but if there is a step or unevenness in the sealing material part, The Au paste may be applied after smoothing by grinding or the like. At this time, the detection electrode wiring 51 was also printed using the same paste, and then baked at a predetermined temperature. The sensing electrode wiring 51 is provided in the third layer of the base, and the via 5 is filled with a conductor.
2 (0.625 mm in diameter), is led to a wiring (not shown) on the second layer, and is connected to an output terminal pin 82.

Next, the lithium carbonate powder was made into a paste, applied to a thickness of about 0.3 mm so as to cover the solid electrolyte element 40 and the sensing electrode 50, and heat-treated at 550 ° C. to form the metal carbonate layer 60. It was formed to be an element of a carbon dioxide sensor. Finally, as shown in FIG. 4, the obtained sensor element is fixed to the pedestal 90, and the output terminal pins 81, 8
2 and the heating element terminal pins 83 and 84, lead wires 91, 92, 93 and 94, respectively, and a protective cap 96 having an air hole 95. Was sealed with an inorganic adhesive 97.

Example 2 FIG. 5 is a cross-sectional view schematically showing the structure of a carbon dioxide sensor according to Example 2 (the terminal pin side is omitted). The carbon dioxide sensor 2 according to the present embodiment is different from the carbon dioxide sensor according to the first embodiment in that the base 10 has a four-layer structure and a recess 14 is formed between the third layer and the fourth layer.
In this embodiment, both the solid electrolyte element 40 and the metal carbonate layer 60 are surrounded. In this embodiment, the detection electrode 50 and the detection electrode wiring 51 are connected by an Au wire 54. In other respects, a carbon dioxide sensor 2 was obtained in the same manner as in Example 1.

-Evaluation of electromotive force value- Four carbon dioxide gas sensors of Examples 1 and 2 obtained as described above were prepared and placed in a chamber in an atmosphere adjusted to a predetermined carbon dioxide gas concentration. Then, each lead wire was connected to a voltmeter and a heating power supply. Then, the heating element was energized to set the surface temperature of the base to 450 ° C., and changes in the electromotive force of the carbon dioxide sensor at various carbon dioxide concentrations were measured. FIGS. 7 and 8 show the results of plotting the electromotive force value at each carbon dioxide concentration against the logarithm of the carbon dioxide concentration.

As a comparative example corresponding to the conventional type, a flat substrate 10 having no depression was used, and the detection electrode 5 was used.
0 and the wiring for the detection electrode (not shown) are connected to the Au wire 54.
And a carbon dioxide gas sensor 3 was produced in the same manner as in Example 1 except that the solid electrolyte element 40 and the periphery of the metal carbonate layer 60 were sealed with an inorganic adhesive 75. The change in the electromotive force was measured. A sectional view of the carbon dioxide sensor of this comparative example is shown in FIG. 6 (terminal pin side is omitted), and a change in electromotive force with respect to the carbon dioxide concentration is shown in FIG.

According to FIG. 7 to FIG.
In the range of -5000 ppm, it was confirmed that there was a good linear relationship between the electromotive force and the carbon dioxide concentration in any of the carbon dioxide sensors according to the Nernst equation.
However, in the carbon dioxide gas sensors of Example 1 (FIG. 7) and Example 2 (FIG. 8), the variation of the electromotive force between the sensors was greatly reduced as compared with the comparative example (FIG. 9), and the depressions in the base body. It has been confirmed that by providing a portion and forming an ion conductor layer therein, variation in output is reduced.

Embodiment 3 In the carbon dioxide gas sensor having the structure of Embodiment 1, the gap between the solid electrolyte element 40 and the solid electrolyte element 40 is changed between 0.01 and 2.0 mm by changing the size of the concave portion 14 of the base. The changed sensor was manufactured, and the occurrence rate of the defect of the seal portion was investigated. In addition, the output characteristics of the sensor in which no defect was found in the seal portion were measured, and the linear gradient (corresponding to so-called sensitivity) of the change in the electromotive force with respect to the carbon dioxide concentration was examined. Table 1 shows the results.

[0050]

[Table 1]

From the results shown in Table 1, when the gap between the solid electrolyte element and the peripheral wall of the depression is small, the filling is insufficient and cracks are generated due to insufficient sealing material.
It was confirmed that as the gap increased, the linear gradient decreased. This is considered to be because if the gap is large, a large amount of sealing material is required, and the temperature of the solid electrolyte element is not stably maintained.

Example 4 In the carbon dioxide gas sensor having the structure of Example 1, the amount of LiSmSiO ₄ powder added to the CaO—BaO—SiO ₂ -based amorphous glass powder used as the sealing material 70 was set to 0 to 100. The rate of occurrence of defects in the seal portion when changed within the range of volume% was investigated. Table 2 shows the results.

[0053]

[Table 2]

From the results shown in Table 2, when the addition amount of the LiSmSiO ₄ powder is in the range of 10 to 80% by volume, the occurrence rate of defects is low, 30 to 70% by volume, and more preferably 40 to 70% by volume.
It turned out that it is particularly good if it is 50% by volume.

Example 5 In the carbon dioxide sensor having the structure of Example 1, when the volume ratio between the crystallized glass and the amorphous glass used as the sealing material 70 is changed, the sensing electrode 50 and the sensing electrode are used. The rate of occurrence of continuity failure with the terminal pins 82 connected to the wiring,
And the incidence of defective seals was investigated. Table 3 shows the results.

[0056]

[Table 3]

From the results shown in Table 3, the crystallized glass content was 2% by volume.
It has been confirmed that when the amount is less than the above, the rate of occurrence of poor conductivity of the electrode, which is considered to be caused by the flow of the seal portion, increases.

Example 6 In the carbon dioxide sensor having the structure of Example 1, the ratio between the area of the heating element and the area of the solid electrolyte element is changed so that measurement can be performed after the heating element is energized. The time until was investigated. By changing the formation pattern of the heating element 20 built in the base 10, the occupation of the effective heating section of the heating element pattern when viewed from a direction perpendicular to one main surface of the base where the recess is provided. The area of the solid electrolyte element 40 when the area was set to 1 (hereinafter referred to as element area ratio) was changed in the range of 0.05 to 200. Table 4 shows the results.
Shown in

[0059]

[Table 4]

From the results in Table 4, it was found that when the element area ratio was larger than 130, it took too much time until the measurement became possible. It is preferable that the element area ratio is small, since the rise time can be shortened. However, if the area ratio of the solid electrolyte element is too small, the escape of heat from the heating element increases, and the power consumption of the heating element increases. The element area ratio is preferably about 30 to 80.

Seventh Embodiment A seventh embodiment is a modification of the carbon dioxide sensor of the first embodiment. The basic configuration of the carbon dioxide gas sensor according to the seventh embodiment including the base 10, the reference electrode 30, the solid electrolyte element 40, the detection electrode 50, the metal carbonate layer 60, the sealing material 70, and the like is the same as that of the first embodiment. The total length of the base body and the form of the output terminal pin and the heating element terminal pin are different from those of the first embodiment, and the method of attaching to the pedestal 90 is different. FIG. 10 is a front view showing a state in which the carbon dioxide sensor according to the seventh embodiment is attached to the pedestal 90. The base 10 of the carbon dioxide sensor is 5 mm long.
The width was 4 mm, and the middle part of each terminal pin side was about 10 m without changing the size of the detection site of the carbon dioxide sensor of Example 1.
m. In addition, pedestal 9
Reference numeral 0 denotes output pins 85 and 86 (length 15 mm) and heater pins 87 and 88 (length 22 mm) made of stainless steel (SUS304) having a cross section of 0.5 mm × 0.2 mm and made of stainless steel (SUS304).
Are provided so as to penetrate vertically in parallel with each other, and one end thereof protrudes in the same manner as the output terminal pin and the heating element terminal pin of the carbon dioxide gas sensor of Example 1, where the lead wires 91, 92, and
93 and 94 are connected.

The tip 87 of the heater pins 87, 88
a, 88a are Pt wires 8 having a diameter of 0.1 mm and a length of 3 mm.
One end of each of 9a and 89b is joined by resistance welding, and each Pt
One side of the base of the carbon dioxide sensor is joined to the other end of the wire by baking Au paste. Similar Pt wires 89c and 89d are also joined to predetermined locations 87b and 88b of the heater pins 87 and 88 by resistance welding, and the other end of the Pt wires is led out of the inside of the base to the side of the base. The end of the heating element wiring is joined by baking Au paste. Further, output pins 85 and 86
0.1mm in diameter and 3mm in length at the ends 85a and 86a
One end of each of the Pt wires 89e and 89f is joined by resistance welding, and the other end is joined to each end of the detection electrode wiring and the reference electrode wiring by baking Au paste. Note that the reference electrode wiring is led out to the surface side from the side surface of the base, and is arranged on the same plane as the end of the detection electrode wiring. As described above, the carbon dioxide sensor of this embodiment is held on the pedestal so as to float in the air via only six Pt lines.

The carbon dioxide sensor attached to the pedestal as described above was further covered with the same protective cap as in Example 1, and a heating test was conducted by energizing the heating element. The power consumption when the set temperature of the detection part was set to 450 ° C. was compared with that of the above-described first embodiment.
Was 2.3 to 2.4 W, whereas in the present embodiment, it was significantly reduced to 1.3 to 1.4 W.

Example 8 Heat generation when viewed from a direction perpendicular to one main surface of the substrate by changing only the length of the substrate while keeping the heating element in the same size and shape as in Example 1. Example 7 except that the ratio of the area of the base to the area occupied by the effective heat generating portion of the body was changed.
In the same manner as in the above, a carbon dioxide sensor was produced. FIG. 11 shows the result of examining the power consumption when these sensors are heated to a constant temperature. In the figure, the power consumption at that time is plotted with the length of the base of each sensor assuming that the length of the base of the carbon dioxide gas sensor of Example 1 is 100 on the horizontal axis. As is apparent from this result, the power consumption decreases as the length of the base becomes shorter, that is, as the area of the base with respect to the area occupied by the effective heat generating portion of the heat generator is smaller.

Example 9 As the solid electrolyte element 40 in Example 1, LiSmSiO ₄ obtained by heat treatment at 900 ° C. in an alumina crucible was used.
The composite is pulverized using an alumina ball mill and an alumina spheroid. The pulverized product is subjected to die press molding, and then subjected to cold isostatic press (CIP) molding, at 1050 to 1200 ° C.
And a plate-shaped sintered body was prepared. When the composition of the pulverized product was analyzed by fluorescent X-ray analysis, it was confirmed that the pulverized product contained 20% by weight of Al ₂ O ₃ . A carbon dioxide sensor was produced in the same manner as in Example 1 except that these sintered bodies were used as the solid electrolyte element 40.

Example 10 As the solid electrolyte element 40 in Example 1, LiSmSiO ₄ obtained by heat treatment at 900 ° C. in an alumina crucible was used.
The composite was crushed in an agate mortar, and
ZrO ₂ powder containing mol% of Y ₂ O ₃ was added and mixed so that the ratio in the whole sintered body was 20% by weight. After this is press-molded in a mold, cold isostatic pressing (CIP)
It was molded and fired at two temperatures of 1000 ° C. and 1100 ° C. to prepare a flat sintered body. A carbon dioxide sensor was produced in the same manner as in Example 1 except that these sintered bodies were used as the solid electrolyte element 40.

Example 11 As the solid electrolyte element 40 in Example 1, Na ₃ Zr ₂ Si obtained by heat treatment at 1200 ° C. in an alumina crucible was used.
The ₂ PO ₁₂ Synthesis was pulverized in an agate mortar, after the pulverized product was mold press molding, and molded cold isostatic pressing (CIP), flat and fired at two temperatures of 1220 ° C. and 1270 ° C. Was prepared. Further, Na ₃ Zr ₂ Si ₂ PO ₁₂ powder is added to the amorphous glass powder serving as the sealing material 70, and the metal carbonate layer 60 is mixed with lithium carbonate powder and calcium carbonate powder (weight ratio: 5: 5). 9) 4
It was formed by heat treatment at 80 ° C. Except for these points, a carbon dioxide sensor was manufactured in the same manner as in Example 1.

The open porosity, total pore volume, and bulk specific gravity of the solid electrolyte element 40 used in each of the carbon dioxide sensors manufactured in Examples 9 to 11 were measured using a mercury intrusion porosimeter. Table 5 shows the results. Further, the influence of humidity on the output (electromotive force) when each carbon dioxide sensor was used continuously for a long period was also investigated. Each carbon dioxide sensor was placed in the atmosphere, and each lead wire was connected to a voltmeter and a heating power source. The heating element was energized to continuously operate the substrate at a surface temperature of 450 ° C. After 24 days, the electromotive force of the carbon dioxide sensor was measured when the relative humidity was 0% and 90% under a constant carbon dioxide concentration (500 ppm). The results are shown in Table 6 together with the results obtained at the initial stage before the continuous operation.

[0069]

[Table 5]

[0070]

[Table 6]

From the results of Tables 5 and 6, it can be seen that when the open porosity of the solid electrolyte element is small, the solid electrolyte element is less susceptible to the influence of humidity and the fluctuation of the electromotive force value is reduced. In particular, when the open porosity is 15% or less on a volume basis, the relative humidity is 0%.
And the difference between the electromotive force values of 90% and 6% at the beginning,
Even after 24 days, the output was small and stable at 7 mV or less, indicating that it was possible to measure the concentration of carbon dioxide with little influence of humidity over a long period of time. In addition,
At this time, the total pore volume of the solid electrolyte element was 0.05 cc.
/ G or less. Further, the above tendency is observed even when the material of the solid electrolyte element is LiSmSiO ₄ -based Na ₃ Zr ₂
The same was true for the Si ₂ PO ₁₂ system.

Embodiment 12 FIG. 12 is a sectional view schematically showing a cross section of a carbon dioxide sensor according to another embodiment of the present invention. The difference from the carbon dioxide sensor of the first embodiment shown in FIG.
0, the solid electrolyte element 40, the sensing electrode 50, and the metal carbonate layer 60 are provided in this order so as to fit inside the recess 14, and the upper surface of the metal carbonate layer 60 is
5 is substantially the same as that of FIG.
Further, the carbon dioxide gas sensor of this embodiment is different from the sensor of the first embodiment also in that a metal net 65 is embedded in the metal carbonate layer 60. The other points are almost the same as those of the carbon dioxide gas sensor of the first embodiment, and the description of the same components will be omitted.

The substrate 10 of the carbon dioxide gas sensor of this embodiment has a four-layer structure, and the third and fourth layers, some of which are removed by punching or the like, are laminated on the second layer to form a two-layer structure. The recessed portion 14 having a depth corresponding to the thickness of the recess 14 is formed. The solid electrolyte element 40 was prepared as follows. Mix the starting material mixture in an alumina crucible for 90
LiSmSiO ₄ synthesized by heat treatment at 0 ° C.
The powder is pulverized with an alumina ball mill and cobblestone, a molding aid is added to the obtained powder, and a metal mold is press-molded and cold isostatically pressed (CIP).
For 3 hours to obtain a flat sintered body. In addition, when the chemical composition of this sintered body was examined by X-ray fluorescence analysis, it was found that 20% by weight of Al ₂ O ₃ was contained. This Al ₂ O ₃ component is
It is presumed that it was mixed due to wear during pulverization.

A carbon dioxide gas sensor was manufactured in the same procedure as in Example 1 using the above-described substrate 10 and sintered body. However, after the Au paste for forming the detection electrode is applied, a 55 mesh Au net (wire diameter: 0.12 mm) serving as the metal net 65 is placed on the Au paste, and the Au electrode is simultaneously baked on the solid electrolyte element. The net was also fixed. Further, a paste of lithium carbonate was applied from above the Au net and heat-treated at 550 ° C. to form a structure in which the Au net was embedded in a metal carbonate layer made of lithium carbonate.

Example 13 A carbon dioxide gas sensor was manufactured in the same manner as in Example 1 except that the metal net 65 was disposed in the metal carbonate layer 60 in the same manner as in Example 12.

An on / off cycle test (hereinafter, also simply referred to as “on / off test”) of the heating element was performed on the carbon dioxide gas sensors obtained in Examples 12 and 13, and The presence or absence of peeling and the fluctuation of sensor output characteristics were examined. In the on / off test, the heating element was energized for 55 minutes, and then the energization was stopped for 5 minutes as one cycle. This cycle was repeated continuously, and the appearance was visually inspected every predetermined number of cycles. In addition to examining the presence or absence of peeling of the metal carbonate layer, the sensor sensitivity and electromotive force were also measured. The sensitivity of the sensor is
It was represented by a linear gradient (mV / decade) of the change in electromotive force when the concentration of carbon dioxide in the test gas changed 10 times. Further, the fluctuation of the electromotive force is caused when the carbon dioxide gas concentration is 10%.
The electromotive force at 00 ppm was measured. FIG. 13 shows a change in the sensitivity of the sensor, and FIG. 14 shows a change in the electromotive force.

In the appearance inspection, peeling of the metal carbonate layer was not observed in both Examples 12 and 13 up to 150 cycles. However, in Example 13, 20
Peeling was observed in the metal carbonate layer at the time of 0 cycles, whereas in Example 12, no peeling of the metal carbonate layer was observed even after 500 cycles. From this, it was confirmed that the effect of preventing peeling of the metal carbonate layer was obtained by adopting a structure in which the metal carbonate layer was accommodated in the depression of the base. Also, the sensitivity and electromotive force of the sensor
It was recognized that Example 12 had higher stability with respect to the number of cycles than Example 13.

[0078]

According to the carbon dioxide sensor of the present invention, a concave portion is provided on a portion of the main surface of the base where the ion conductor layer is to be mounted, and an ion conductor layer made of a solid electrolyte or an ion conductor layer is provided therein. It is mounted so that the laminated portion from the body layer to the metal carbonate layer is fitted. Further, a predetermined sealing material made of amorphous glass or crystallized glass is filled in a gap between the ion conductor layer and the depression. Therefore, the reference electrode side of the ion conductor layer made of the solid electrolyte is completely sealed and is shielded from the outside air or the test gas.
In addition, since a small gap between the ion conductor layer and the recess is cut off from the outside air or the like, the area where the sealing material is exposed is extremely small, and the amount of the sealing material used is small.

Further, in the carbon dioxide gas sensor of the present invention, since the surface of the ion conductor layer on the side of the detection electrode is flush with one main surface of the base, the detection electrode can be easily formed by the thick film method. , Making the production simple. Further, the distance between the sensing electrode side of the ion conductor layer and the peripheral wall of the depression is set to 0.05 to
By setting the thickness within the range of 1.0 mm, heat loss from the heating element can be suppressed low, and the output characteristics of the sensor, that is, the output voltage gradient (mV / de) with respect to the concentration of carbon dioxide gas.
) can be kept high. If the distance is less than 0.05 mm, the sealing material may not be completely filled, and it may not be possible to secure the cutoff between the reference electrode and the outside air. If the interval is larger than 1.0 mm, the output voltage gradient decreases sharply. It is conceivable to increase the output voltage gradient by increasing the heating temperature of the heating element, but this method is not efficient.

In the present invention, amorphous glass is used as a sealing material. A glass powder of a predetermined composition is made into a slurry or paste, injected into a gap around the ion conductor layer, dried, heated to the softening point of the glass to melt the glass, and the molten glass is poured over the entire gap. This completes the sealing. A part of the amorphous glass can be used instead of the crystallized glass. Since the crystallized glass precipitates a crystal phase under a predetermined heat treatment after melting, it does not soften during the subsequent baking of the detection electrode, and has the effect of preventing the occurrence of wiring continuity failure.

Further, by fixing the sensor in a suspended manner on the pedestal using a thin Pt wire or the like, the power consumption of the heating element can be reduced, and an energy saving type carbon dioxide sensor can be obtained. At this time, the effect is further enhanced by increasing the ratio of the occupied area of the effective heating portion of the heating element to the entire base of the sensor. Further, in the case of the above-mentioned suspension type, it is possible to provide a sensor that can endure a strong external force, vibration and the like. further,
By arranging a metal network in the part of the metal carbonate layer,
Separation from the detection electrode does not occur even when heating and cooling are repeated, and the durability can be improved.

The above-mentioned carbon dioxide sensor is, for example,
It is particularly useful as a sensor used for air-conditioning equipment such as an automatic ventilator, for promoting growth of crops in house cultivation, and for managing freshness during transport and storage of crops.

[Brief description of the drawings]

FIG. 1 is a front view of a carbon dioxide sensor according to a first embodiment.

FIG. 2 is a sectional view taken along line A-A 'of FIG.

FIG. 3 is a sectional view taken along line B-B 'of FIG.

FIG. 4 is a partial cross-sectional view showing a state where a pedestal and a protective cap are attached to the carbon dioxide sensor of Example 1.

FIG. 5 is a sectional view of a carbon dioxide sensor according to a second embodiment.

FIG. 6 is a cross-sectional view of a carbon dioxide sensor of a comparative example.

FIG. 7 is a graph showing a relationship between a carbon dioxide gas concentration and an electromotive force in Example 1.

FIG. 8 is a graph showing a relationship between a carbon dioxide gas concentration and an electromotive force in Example 2.

FIG. 9 is a graph showing a relationship between a carbon dioxide gas concentration and an electromotive force in a comparative example.

FIG. 10 is a front view of a carbon dioxide sensor according to a seventh embodiment.

FIG. 11 is a graph showing a change in power consumption when the length of the base is changed.

FIG. 12 is a sectional view of a carbon dioxide sensor according to a twelfth embodiment.

FIG. 13 is a graph showing a change in sensitivity of the carbon dioxide sensor by an on / off test.

FIG. 14 is a graph showing a change in electromotive force of the carbon dioxide sensor by an on / off test.

[Explanation of symbols]

 10; base 14; depression 20; heating element 30; reference electrode 31; reference electrode wiring 40; solid electrolyte element 50; detection electrode 51; detection electrode wiring 60; metal carbonate layer 65; metal mesh body 70; Material 81, 82; Terminal pin for output 83, 84; Terminal pin for heating element

 ────────────────────────────────────────────────── ─── Continued from the front page (72) Inventor Masatoshi Ueki 14-18 Takatsuji-cho, Mizuho-ku, Nagoya-shi, Aichi Japan Special Ceramics Co., Ltd.

Claims (30)

[Claims] 1. A base having a built-in heating element, a reference electrode,
An ion conductor layer made of a solid electrolyte, a detection electrode, and a metal carbonate layer are formed in this order, and the ion conductor layer is arranged in a depression provided on one main surface of the base. Carbon dioxide sensor characterized by the above-mentioned. 2. A base including a heating element, a reference electrode,
An ion conductor layer made of a solid electrolyte, a detection electrode, and a metal carbonate layer are formed in this order, and the ion conductor layer, the detection electrode, and the metal carbonate layer are provided on one main surface of the base. A carbon dioxide sensor, wherein the carbon dioxide sensor is disposed in a recessed portion. 3. The carbon dioxide sensor according to claim 1, wherein a gap between the ion conductor layer and the peripheral wall of the recess is filled with a sealing material. 4. The carbon dioxide sensor according to claim 3, wherein a distance between the ion conductor layer and a peripheral wall of the recess is 0.05 to 1.0 mm. 5. The carbon dioxide sensor according to claim 3, wherein the sealing material is amorphous glass or crystallized glass. 6. The amorphous glass is made of CaO—BaO—S.
carbon dioxide sensor according to claim 5 which is iO ₂ based glass. 7. The crystallized glass is SiO ₂ —BaO—
Al ₂ O ₃ based carbon dioxide sensor according to claim 5 which is a crystallized glass. 8. The carbon dioxide sensor according to claim 5, wherein the sealing material contains 80% by volume or less of particles made of the same material as the solid electrolyte. 9. The carbon dioxide sensor according to claim 5, wherein an alkali metal component contained in the sealing material is 5% by weight or less in terms of oxide. 10. The sealing material according to claim 5, wherein the reference electrode is made of amorphous glass and the detection electrode is made of crystallized glass.
2. The carbon dioxide sensor according to 1. 11. The carbon dioxide sensor according to claim 10, wherein the volume ratio of the sealing material is 50 to 98% by volume of the amorphous glass and 50 to 2% by volume of the crystallized glass. 12. The carbon dioxide sensor according to claim 10, wherein the softening point of the amorphous glass is higher than the softening point of the crystallized glass. 13. The carbon dioxide sensor according to claim 1, wherein the solid electrolyte is a Li ion conductive solid electrolyte. 14. The carbon dioxide sensor according to claim 13, wherein the solid electrolyte has LiSmSiO ₄ as a main crystal phase. 15. The method according to claim 14, wherein the solid electrolyte is LiSm having a main crystal phase.
Carbon dioxide sensor according to claim 13 containing in addition to Al ₂ O ₃ of SiO _4. 16. The method according to claim 16, wherein the solid electrolyte is LiSm having a main crystal phase.
Carbon dioxide sensor according to claim 13 containing ZrO ₂ in addition to SiO _4. 17. The carbon dioxide sensor according to claim 13, wherein the metal carbonate layer contains lithium carbonate or lithium carbonate and an alkaline earth metal carbonate as main components. 18. The method according to claim 1, wherein at least a portion of the reference electrode which is in contact with the ion conductor layer is made of Au.
4. The carbon dioxide gas sensor according to 3. 19. The carbon dioxide sensor according to claim 1, wherein the solid electrolyte is a Na ion conductive solid electrolyte. 20. The method according to claim 19, wherein the solid electrolyte is NASICON (N
_{a 1 + X Zr 2 Si X} P 3 _{over X O 12, 0 ≦ X ≦} 3) a carbon dioxide sensor according to claim 19, the main crystalline phase. 21. The NASI in which the solid electrolyte has a main crystal phase.
_{CON (Na 1 + X Zr 2} Si X P 3 _{over X O 12, 0 ≦ X ≦} 3) in addition to carbon dioxide sensor according to claim 19 containing ZrO ₂ in. 22. The carbon dioxide sensor according to claim 19, wherein the metal carbonate layer contains lithium carbonate or lithium carbonate and an alkaline earth metal carbonate as main components. 23. The reference electrode according to claim 1, wherein at least a portion of the reference electrode that is in contact with the ion conductor layer is made of Pt.
10. The carbon dioxide sensor according to 9. 24. The carbon dioxide sensor according to claim 1, wherein the detection electrode is made of Au. 25. The carbon dioxide sensor according to claim 1, wherein the surface of the ion conductor layer on the side of the detection electrode is on the same plane as the one main surface of the base. 26. An ionic conductor layer having an area occupied by 0.05 when an occupied area of an effective heat generating portion of the heat generating element is 1 when viewed from a direction perpendicular to the one main surface of the base.
The carbon dioxide sensor according to claim 1 or 2, wherein the carbon dioxide sensor has a value of 1.30. 27. The semiconductor device according to claim 1, wherein each of the wiring ends extending from the heating element, the reference electrode, and the detection electrode to the surface or the side surface of the base is indirectly attached to the pedestal via a conductive connection member. 3. The carbon dioxide sensor according to 2. 28. When viewed from a direction perpendicular to the one main surface of the base, an area of the base is 1.1 to 3 when an occupied area of an effective heat generating portion of the heat generating element is 1. The carbon dioxide sensor according to claim 1, 2 or 27. 29. The carbon dioxide sensor according to claim 1, wherein an open porosity of the solid electrolyte is 15% or less. 30. The carbon dioxide sensor according to claim 1, wherein a metal net is provided in the metal carbonate layer.