JPH11153564A - Carbon dioxide sensing element - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To improve the adhesion between a porous ceramic which is a carbon dioxide gas detection material and an electrode, to prevent peeling at an operating temperature of several hundred degrees Celsius, and to suppress the deterioration of performance over time. It is an object of the present invention to provide a carbon dioxide gas sensing element that can be made and has little variation in characteristics of each element. SOLUTION: The surface roughness Rmax of the surface of the carbon dioxide sensing porous ceramic 1 on which the electrode 52 is deposited and / or the minimum pitch adjacent to the uneven step is larger than the particle diameter constituting the electrode 52, and the uneven step is formed. Is formed so that the maximum pitch adjacent thereto is less than or equal to the film thickness of the electrode 52.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carbon dioxide sensing element using ceramics as a carbon dioxide sensing material.

[0002]

2. Description of the Related Art In recent years, various carbon dioxide sensing elements for measuring and controlling carbon dioxide in facility horticulture and various production facilities have been researched and developed.

As such a carbon dioxide gas detecting element, a solid electrolyte type element which takes out an electromotive force generated by a reaction between a solid electrolyte and carbon dioxide gas as an electric signal to detect a concentration, and a ceramic formed from a metal oxide are used. There is known an impedance change type that detects a change in impedance characteristics such as electric resistance and capacitance due to a reversible carbonate formation reaction between carbon dioxide and carbon dioxide.

In particular, the impedance-change type carbon dioxide sensing element is easy to manufacture because of its simple structure, and the detection circuit is simple, so that the entire apparatus can be easily reduced in size and cost. I can do it.

[0005] Each of these carbon dioxide sensing elements has a basic structure in which an electrode is bonded to a carbon dioxide sensing material.
Since the operating temperature is as high as 250 to 900 ° C., the adhesion between the ceramic and the electrode has a great influence on the characteristics of the carbon dioxide gas detecting element.

For example, as a solid electrolyte type carbon dioxide sensing element, Japanese Unexamined Patent Publication No. 4-309858 discloses a method of forming a reference electrode and a sensing electrode by performing vacuum deposition, sputtering, or plating of a noble metal or a conductive material of a noble metal. Is disclosed, and the operation temperature is described as 550 ° C.

As impedance-change type carbon dioxide sensing elements, those having various compositions are disclosed in JP-A-4-24548 and JP-A-6-317551, and silver paste is used as an electrode. It is formed by attaching and firing. Operating temperature is 300C ~ 90 each
0 ° C, 250 ° C to 800 ° C.

Hereinafter, a conventional impedance-variable carbon dioxide sensing element will be described with reference to the drawings.

FIG. 11 is a perspective view showing the configuration of a conventional impedance-variable carbon dioxide sensing element, and FIG. 12 is an enlarged view of a portion B in FIG. 11 and 12, 51
Is a porous ceramic for detecting a carbon dioxide gas of an impedance change type, 52 is one or more electrodes provided on the surface or inside of the porous ceramic for detecting a carbon dioxide gas 51, 53 is Al
A substrate formed of ₂ O ₃ or the like; 54, a platinum heater disposed on the substrate 53; 55, a lead wire connected to at least one surface or inside of the electrode 52; 56, a lead wire fixing material; In order to transmit a change in impedance from the detection porous ceramic 51, a wiring 58 disposed on the substrate 53 is a carbon dioxide detection porous ceramic 51.
This is a gap generated due to low adhesion between the surface of the electrode 52 and the electrode 52 or a partial breakage of the surface of the carbon dioxide sensing porous ceramic 51.

A method for manufacturing the conventional carbon dioxide sensing element shown in FIG. 11 will be described below. Carbon dioxide detection porous ceramic 5
1 is formed by firing one or more metal oxide raw materials. For the metal oxide raw material, after a commercially available metal oxide is dry- or wet-pulverized with a ball mill or the like, it is passed through a sieve or a binder is again mixed with a ball mill or the like, dried by a spray dry method, granulated, and granulated. Use a particle size distribution. Furthermore, after performing preliminary heat treatment such as calcination, after performing molding by various presses and the like, by performing mixing or kneading by adding ethyl cellulose, terpineol, etc., mixing and kneading and forming a paste by printing or punching,
It is fired to obtain a carbon dioxide sensing porous ceramic.

The electrode 52 is formed by spin-coating a paste, etching or screen printing, or by vapor deposition or sputtering. The pattern shape is selected from a circle, a polygon, a comb, and the like.

The platinum heater 54 and the wiring 57 are fixed by baking after forming a platinum paste or the like on the substrate 53 by screen printing or the like.

The carbon dioxide sensing porous ceramics 51 before the heat treatment, on which the electrodes 52 are applied and printed, are arranged on a substrate 53 and fired. Thus, the carbon dioxide sensing porous ceramic 51 having the electrode 52 also on the upper surface is fixed on the substrate 53.

The lead wire 55 is made of a bulk material Pt wire, Au
After immersing a wire, a Ni wire, or the like in the raw material paste of the lead wire fixing material 56, the wire and the Ni wire are adhered to the electrode 52 and fixed by firing. The lead wires 55 may be paste-printed by screen printing, and may be made of Pt, Au, RuO ₂ , Ag, C
u, CuO, Ni, etc. may be formed by vapor deposition or sputtering. At this time, the lead wire fixing material 56 is applied and baked so that the lead wire 55 is not broken due to a step between the carbon dioxide sensing porous ceramic 51 and the substrate 53 made of Al ₂ O ₃ or the like.

Through the above manufacturing steps, a conventional impedance-change-type carbon dioxide sensing element can be obtained.

In the above-mentioned conventional porous ceramics of the impedance-change type carbon dioxide gas detecting material, it is difficult to adhere electrodes to the surface thereof with good adhesiveness. Also, even if the electrode is relatively well adhered to the porous surface, the surface of the porous ceramic often has weak particles,
The electrode often breaks the bonding of the particles on the ceramic surface while keeping the part of the surface of the porous body in close contact by thermal stress generated at an operating temperature of several hundred degrees Celsius, and often causes separation.
Also, even when the adhesion between the porous ceramic surface and the electrode is good, the mechanical and / or
Alternatively, when thermal distortion is large, peeling is also likely to occur.

In any case, if a gap is formed at each interface, there is a problem that the performance of the carbon dioxide sensing element deteriorates with time and the accuracy of the element tends to be low because the characteristic of each element varies. doing.

As a study for solving such a problem, for example, Japanese Patent Application Laid-Open No. 55-24654 discloses a technique for improving the adhesion between a gas detection ceramic and an electrode. It discloses that a porous film is provided on the surface of an oxygen sensor using stabilized zirconia using the same stabilized zirconia using a special binder, and a Pt electrode is deposited thereon. Japanese Patent Laid-Open No. 5-180
Japanese Patent Publication No. 797 discloses that an oxygen concentration sensor is provided with a groove having a width substantially equal to the particle diameter of the second ceramic particles to be attached, on which a Pt electrode is attached.

[0019]

However, the above-mentioned conventional ceramic gas detecting element having improved electrode adhesion has the following problems.

As described in JP-A-55-24654, a porous film is fired on a ceramic surface using a special binder, and a platinum electrode is formed by electroless plating or electrolytic plating. Depending on the degree, there was a problem that it could not be adhered all over.

Further, when grooves are provided on the surface of the porous ceramic as disclosed in JP-A-5-180797, there is a problem that the strength is significantly reduced.

The present invention solves the above-mentioned conventional problems, and comprises a porous ceramic which is a carbon dioxide sensing material, one or more electrodes provided on the surface of the porous ceramic, and / or the surface of the electrode. It is possible to improve the adhesion with the lead wire connected to the semiconductor device, obtain high reliability without deteriorating the performance over time due to the occurrence of peeling, etc., and greatly reduce the variation in the characteristics of each element. It is intended to provide a carbon dioxide sensing element.

[0023]

In order to solve the above-mentioned conventional problems, a carbon dioxide sensing element according to the present invention comprises a porous ceramic which is a carbon dioxide sensing material, and a ceramic provided on the surface or inside of the porous ceramic. One or more electrodes, a lead wire connected to the surface or inside of the electrode, a lead wire fixing material for connecting and fixing the electrode and the lead wire, a heater capable of heating the porous ceramic to an operating temperature, and A substrate on which a porous ceramic and the heater can be arranged;
A current-carrying wiring disposed on the substrate, wherein the surface roughness of the surface of the porous ceramic on which the electrode is applied, the surface roughness Rmax and / or the minimum adjacent roughness. The pitch is set to be equal to or larger than the particle diameter of the electrode, and the maximum pitch adjacent to the uneven step is set to be equal to or smaller than the film thickness of the electrode.

According to this structure, the adhesion between the porous ceramic and the electrode is improved, the peeling does not occur even at an operating temperature of 500 to 600 ° C., and the performance deterioration over time can be suppressed. It is possible to provide a carbon dioxide gas sensing element with less variation in characteristics.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION The invention according to claim 1 of the present invention relates to a porous ceramic which is a carbon dioxide sensing material, and one or more electrodes provided on or on the surface of the porous ceramic. A lead wire connected to the surface or inside of the electrode, a lead wire fixing material for connecting and fixing the electrode and the lead wire, a heater capable of heating the porous ceramic to an operating temperature, the porous ceramic and the heater A carbon dioxide sensing element, comprising: a substrate on which the electrodes can be disposed; and a current-carrying wiring disposed on the substrate, wherein the surface roughness Rmax of the surface of the porous ceramic on which the electrodes are applied is
And / or the minimum pitch adjacent to the uneven steps is equal to or larger than the particle diameter constituting the electrode, and the maximum pitch adjacent to the uneven steps is equal to or less than the film thickness of the electrode, Since the constituent particles of the electrode can be fitted all over the uneven portion of the porous ceramic surface, and the uneven portion is almost entirely covered by the film thickness of the electrode, it is used as a gas concentration detecting device. In a carbon dioxide gas concentration detecting device whose operating temperature is relatively high, the adhesion between the porous ceramic as a carbon dioxide gas detecting material and one or more electrodes can be remarkably improved. At the same time, it is possible to provide a carbon dioxide gas sensing element that does not cause separation even at a temperature and can suppress a deterioration in performance over time, and that has a small variation in characteristics of each element. To.

Here, the surface processing of the porous ceramic includes grinding using a grindstone, lap finishing using free abrasive grains,
Polishing using water-resistant abrasive paper is generally performed,
The surface may be chemically etched using an etching solution or an etching gas. A surface processing method such as ion milling or sand blasting is also used.

Here, when the minimum roughness adjacent to the surface roughness Rmax and the unevenness step is smaller than the particle diameter constituting the electrode,
The particles of the electrode cannot fit into the unevenness of the surface of the porous ceramic at all, and a gap is formed between the electrode and the surface of the porous ceramic, so that a good adhesion state cannot be obtained. Further, if the maximum pitch adjacent to the uneven step is larger than the film thickness of the electrode, the electrode cannot be in close contact with the entire uneven step, and a gap is formed after firing, and a good adhesion state cannot be obtained. If a gap is formed, in a carbon dioxide gas concentration detection device whose operating temperature is relatively high, thermal distortion due to the difference in the material of the porous ceramic and the electrode causes the position of the particles on the surface of the porous ceramic to be displaced. , Which tends to affect the impedance characteristics, which is not preferable.

The surface roughness Rmax and / or the minimum pitch adjacent to the unevenness is preferably 1 to 10 times, preferably 1 to 5 times the particle diameter of the electrode. As it becomes larger than 5 times, in order to cover all the uneven steps, it is necessary to increase the film thickness, and with the increase of the internal stress of the film, peeling or destruction of the porous surface tends to occur, which is not preferable. .

The maximum pitch of the uneven steps is preferably 1 to 0.1 times the film thickness of the electrode. As the size becomes smaller than 0.1 times, the electrode tends to be unable to cover the edge of the projection, which is not preferable.

According to a second aspect of the present invention, there is provided a porous ceramic which is a carbon dioxide sensing material, at least one electrode provided on or inside the porous ceramic, and a surface of the electrode. Or, a lead wire connected inside, a lead wire fixing material for connecting and fixing the electrode and the lead wire, a heater capable of heating the porous ceramic to an operating temperature, and a substrate on which the porous ceramic and the heater can be arranged And a wiring for energization disposed on the substrate, wherein the porous ceramic on which the electrode is to be adhered has SiO ₂ , Al ₂
An oxide layer containing at least one of O ₃ and ZrO ₂ is to be sintered, and SiO ₂ , Al ₂ O ₃ ,
ZrO ₂ is a material having no sensitivity to carbon dioxide gas, and since each material itself is easily sintered, it works as a binder for an inorganic material, and therefore, it is necessary to strengthen the surface of the porous ceramic. In addition, since the electrodes are firmly adhered to each other, the electrode has an effect of preventing separation of the electrodes due to breaking of the bonding of particles on the surface of the porous ceramic.

Here, the oxide layer is formed, for example, after spin-coating silica sol or alumina sol.
Firing at 0 ° C. to 900 ° C., SiO ₂ , Al ₂ O ₃ , Z
The paste is formed by preparing a paste containing rO ₂ as a main component and a glass component, and printing and firing. Further, it can be applied by vapor deposition or sputtering. When spin-coating or printing a sol or low-viscosity paste, it is desirable to form the paste only near the surface of the porous ceramic. If it penetrates into the inside, it becomes difficult for carbon dioxide gas to directly contact the particles of the porous ceramic, and the sensitivity tends to decrease, which is not preferable.

According to a third aspect of the present invention, there is provided a porous ceramic which is a carbon dioxide sensing material, at least one pair of electrodes provided on or inside the porous ceramic, and a surface of the electrode. Or a lead wire connected inside, a lead fixing material for connecting and fixing the electrode and the lead wire, a heater capable of heating the porous ceramic to an operating temperature, the carbon dioxide sensing porous ceramic and the heater A carbon dioxide sensing element comprising a substrate that can be arranged, and a wiring for energization arranged on the substrate, wherein the electrode and the lead wire fixing material are formed of the same material. Yes, a strong chemical bond is easily obtained by firing, and the linear thermal expansion coefficient of the material of the electrode and the material of the lead wire fixing material is the same. Because it can reduce the generation of thermal stress, it has a porous ceramic surface, the effect that it is possible to remarkably improve the adhesion between the deposited electrode.

According to a fourth aspect of the present invention, there is provided a porous ceramic which is a carbon dioxide sensing material, one or more electrodes provided on or inside the porous ceramic, and a surface of the electrode. Or, a lead wire connected inside, a lead wire fixing material for connecting and fixing the electrode and the lead wire, a heater capable of heating the porous ceramic to an operating temperature, and a substrate on which the porous ceramic and the heater can be arranged And a wire for energization disposed on the substrate, wherein the linear thermal expansion coefficient α of the porous ceramic, the linear thermal expansion coefficient β of the electrode, and the lead The linear thermal expansion coefficient γ of the wire fixing material is α
≧ β ≧ γ to reduce the difference in linear thermal expansion coefficient between the porous ceramic and the electrode, and between the contact surfaces of the electrode and the lead wire fixing material. Since the thermal stress can be reduced, the smaller the linear thermal expansion coefficient, the more the compressive stress indicates, and a force is applied in a direction that does not peel off from the object to be adhered. This has the effect that the adhesion to the deposited electrode can be significantly improved.

If α <β or β <γ, it is not preferable because the generated thermal stress acts in the direction of peeling off each other.

According to a fifth aspect of the present invention, in the first aspect of the present invention, the electrode includes a noble metal and / or a noble metal oxide and a glass component. A paste is formed by firing, and the electrode after firing has the glass component in an amount of 10 to 65 vol%, preferably 20 to 20 vol%.
６０60 vol%.
Since it contains a noble metal and / or a noble metal oxide, it can maintain good conductivity even at a relatively high operating temperature, and has an effect that a glass component firmly adheres to the porous ceramic.

Here, as the noble metal and / or noble metal oxide, any one or more of platinum, gold, ruthenium, rhodium, palladium, osmium, iridium and oxides thereof are used, and preferably platinum, gold, ruthenium, Ruthenium oxide or the like is used. Borosilicate glass or the like is used as the glass component.

Here, the paste can be formed by mixing a large amount of glass without separating it from the glass during firing in the order of platinum, gold, ruthenium, and ruthenium oxide. Also,
When ruthenium or ruthenium oxide is contained and borosilicate glass is the main component as the glass component, ruthenium or ruthenium oxide is precipitated at the grain boundaries of the sintered paste, and the amount of ruthenium or ruthenium oxide deposited can be increased over a wide range. Therefore, resistance pastes having various resistance values can be produced, and the amount of glass components can be used in a wider range than platinum and gold, which is preferable.

Here, the glass component content in the electrode is 20 v
As the amount becomes less than ol%, the noble metal component and the glass component separate during firing, making it difficult to form an electrode having a uniform composition, and causing the precious metal component to peel off or the electrode itself to have a variation in impedance. Absent. On the other hand, as the content exceeds 60% by volume, the stress of the glass itself increases, and the bonding of particles on the surface of the porous ceramic is broken, and the glass tends to be easily peeled, which is not preferable. This tendency becomes more remarkable as the glass component becomes less than 10% or more than 65% by volume, which is further undesirable.

According to a sixth aspect of the present invention, in the first aspect of the present invention, the electrode is formed of a noble metal and / or a noble metal oxide and a carbon dioxide gas sensing porous material. And a glass component containing at least one of the raw materials of the porous ceramic, which is formed by firing a paste containing the glass component. Since the raw material of at least one of the porous ceramics contained in the glass component can adhere to the porous ceramic with strong chemical affinity, the porous ceramic surface even at a relatively high operating temperature, This has the effect that the adhesion to the deposited electrode can be significantly improved. In addition, since it acts in the direction of reducing the difference in linear thermal expansion coefficient between the surface of the porous ceramic and the electrode, the thermal stress can be reduced, so that it has the effect of making it difficult to peel off.

According to a seventh aspect of the present invention, in the first aspect of the invention, there is provided a porous ceramic which is a carbon dioxide gas detecting material, and one of the porous ceramics provided on the surface or inside of the porous ceramic. The above electrode, a lead wire connected to the surface or inside of the electrode, a lead wire fixing material for connecting and fixing the electrode and the lead wire, a heater capable of heating the porous ceramic to an operating temperature, A carbon dioxide sensing element comprising: a porous ceramic, a substrate on which the heater can be disposed, and a current-carrying wiring disposed on the substrate, wherein the porous ceramic is CeO ₂ , Ba.
It contains a mixture of CO ₃ and CuO, has a surface roughness Rmax of 0.5 μm or more and 5 μm or less on the surface on which the electrode is applied, a pitch of adjacent uneven steps of 3 μm or more and 25 μm or less, and a particle diameter of the electrode. Since the mixture of CeO ₂ , BaCO ₃ , and CuO has a large change in electric capacity when carbon dioxide gas is introduced, a high-sensitivity sensing element can be obtained. Having.
Further, it has an effect that moisture resistance is far superior to that of a conventional solid electrolyte type carbon dioxide gas sensing element.

The surface roughness of the surface, the pitch of the uneven steps,
When the particle diameters of the electrodes fall within the above ranges, the adhesion between the porous ceramic and the electrode can be significantly improved.

Here, a mixture of CeO ₂ , BaCO ₃ , and CuO has a particle size of 0.05 to 1 μm and a peak having a particle size distribution of about 0.5 μm is easily available and easily processed.

It is not preferable to make Rmax smaller than 0.5 μm or to make the pitch of the uneven steps smaller than 3 μm because precision polishing or the like is required. On the other hand, if Rmax is larger than 5 μm, the strength of the porous ceramic decreases, and cracks easily occur on the surface of the porous ceramic due to the internal stress of the electrode. Also,
If the pitch of the uneven steps is larger than 25 μm, the adhesion between the electrode and the surface of the porous ceramic is significantly reduced, which is not preferable.

According to an eighth aspect of the present invention, in the seventh aspect, the electrode contains at least one of ruthenium oxide, platinum and gold, and a glass component. The paste is formed by firing, and the electrode after firing contains 10 to 65 vol%, preferably 30 to 45 vol%, of the glass component. Since ruthenium oxide, platinum, and gold have higher heat resistance at high operating temperatures and better moisture resistance than electrode materials that can contain glass components such as silver, palladium, and copper. This has the effect that the characteristics of the carbon dioxide sensing element are unlikely to deteriorate with time. Further, since the glass component is contained in the above range, the porous ceramic and the electrode have an effect of obtaining good adhesion without peeling off.

Here, the glass component content in the electrode is 30
vol%, ruthenium oxide, platinum,
One or more noble metal components of gold and the glass component are separated at the time of firing, making it difficult to form an electrode having a uniform composition. Also, the noble metal component peels off, and the electrode itself tends to have a variation in impedance. It is not preferable because it occurs. On the other hand, when the content is more than 45 vol%, the stress of the glass itself increases, and the bonding of the particles on the surface of the porous ceramic is broken, and the glass tends to be easily peeled. This tendency becomes more remarkable as the glass component becomes less than 10% or more than 65% by volume, which is further undesirable.

According to a ninth aspect of the present invention, in the ninth aspect, the electrode has a thickness of 10 to 50 μm.
m, preferably 10 to 25 μm, in addition to the effect of the invention according to claim 7,
Since the maximum pitch of the irregularities of the porous ceramic is smaller than the thickness of the electrode, it has the effect of significantly improving the adhesion.

Here, as the thickness of the electrode becomes thinner than 10 μm, it tends to become difficult to fill the uneven steps of the porous ceramic, and as the thickness becomes thicker than 25 μm, the thermal stress of the glass component increases. Therefore, it is not preferable because the surface of the porous ceramic tends to be easily broken. Further, as the thickness becomes larger than 50 μm, this tendency becomes more remarkable, so that it is not preferable.

According to a tenth aspect of the present invention, in the invention according to the seventh aspect, the paste material for forming the electrode contains CuO or Cu ₂ O as a glass component. With this, in addition to the effect of the invention according to claim 7, when the electrode paste material is fired, the porous ceramic surface and the electrode can be adhered with a particularly strong chemical bonding force. Has an action. In addition, the difference in linear thermal expansion coefficient between the porous ceramic and the electrode can be reduced, and CuO, C
u ₂ O has an effect which could strongly adhere more liable to partially sublimated diffused by heat treatment at 800 to 900 ° C..

The eleventh aspect of the present invention is the invention according to the seventh aspect, wherein the linear thermal expansion coefficient α of the porous ceramic, the linear thermal expansion coefficient β of the electrode, and the lead wire fixing material. Has a relationship of α ≧ β ≧ γ, and (α−β) and (α−γ) are each 5 × 10 ⁻⁶ (/ deg) or less. And the porous ceramic is made of CeO ₂ , BaCO ₃ , Cu
When a mixture of O is contained, the difference in linear thermal expansion coefficient between the porous ceramic and the electrode, and the contact surface between the electrode and the lead wire fixing material can be reduced, so that the thermal stress can be reduced. At the same time, the smaller the linear thermal expansion coefficient, the higher the compressive stress, so that a force is applied in a direction that does not peel off from the object to be attached, so that the adhesion between the porous ceramic surface and the attached electrode is Can be significantly improved.

Here, it is not preferable that α <β or β <γ because stress is generated in a direction in which each of them peels when heated to the operating temperature. Also, (α-β) and (α-γ)
Becomes larger than 5 × 10 ^-6 (/ deg), respectively.
An operating temperature of about 00 to 600 ° C. is not preferable because peeling easily occurs.

Hereinafter, an embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG. (Embodiment 1) FIG. 1 is a perspective view of a carbon dioxide sensing element according to Embodiment 1 of the present invention, and FIG. 2 is an enlarged view of a portion A in FIG.

1 and 2, reference numeral 1 denotes a porous ceramic which is a carbon dioxide gas detecting material, 6 denotes a surface roughness Rmax of the surface of the porous ceramic 1, and 7 denotes an adjacent surface unevenness step of the surface of the porous ceramic 1. The minimum pitch 8 is the maximum pitch adjacent to the uneven steps on the surface of the porous ceramic 1.

Electrode 52, substrate 53, platinum heater 54, lead wire 55, lead wire fixing material 56, wiring 57, gap 5
8 is the same as the conventional one, so the same reference numeral is assigned and the description is omitted.

The difference between the carbon dioxide sensing element of the present embodiment and the conventional one is that, in FIG.
Alternatively, the surface is processed so that the minimum pitch 7 adjacent to the uneven step is larger than the particle diameter constituting the electrode 52 and the maximum pitch 8 adjacent to the uneven step is smaller than the film thickness of the electrode 52. is there.

As a processing method, grinding using a grindstone, lapping using free abrasive grains, polishing using a water-resistant abrasive paper, and the like are common, but the surface is chemically etched using an etching solution or an etching gas. You may. In addition, mechanical processing methods such as ion milling and sandblasting are also used.

Thus, in the carbon dioxide gas concentration detecting device having a relatively high operating temperature as the gas concentration detecting device, the carbon dioxide gas detecting element shown in FIGS. It significantly improves the adhesion to one or more electrodes, prevents peeling even at an operating temperature of several hundred degrees Celsius, suppresses performance degradation over time, and has little variation in characteristics between elements. A gas sensing element can be provided.

(Embodiment 2) FIG. 3 is an end view of a portion of a carbon dioxide gas sensing element according to Embodiment 2 of the present invention where electrodes are attached.

In FIG. 3, reference numeral 51 denotes a carbon dioxide sensing porous ceramic, and reference numeral 10 denotes SiO ₂ , Al ₂ O ₃ , Z formed and sintered on the surface of the carbon dioxide sensing porous ceramic 51.
An oxide containing at least one kind of rO ₂ , 52 is an electrode. The oxide 10 is, for example, spin-coated with silica sol or alumina sol and then baked at 300 ° C. to 900 ° C. or printed and baked by preparing a paste containing SiO ₂ , Al ₂ O ₃ , ZrO ₂ as a main component and a glass component. May be. Further, it can be applied by vapor deposition or sputtering. When spin-coating or printing a sol or low-viscosity paste, it is desirable to form the paste only near the surface of the carbon dioxide sensing porous ceramic 51. When it penetrates into the inside, it becomes difficult for the carbon dioxide gas to directly contact the particles of the carbon dioxide detection porous ceramic 51,
The sensitivity decreases.

In a carbon dioxide gas concentration detector having a relatively high operating temperature as a gas concentration detector, the mechanical coupling of the particles on the surface of the carbon dioxide gas detecting porous ceramic 51 is strengthened, and the coupling of the particles on the surface is improved. Breakage and peeling can be prevented, and the adhesion to the deposited electrode can be significantly improved, so that high reliability can be obtained.

(Embodiment 3) FIG. 4 is a sectional view of a main part of a carbon dioxide sensing element according to Embodiment 3 of the present invention.

In FIG. 4, reference numeral 11 denotes a lead wire fixing material made of the same material as the electrodes. After the lead wire 55 is dipped in the same paste as the paste forming the electrode,
And fired.

Since the generation of thermal stress can be reduced by using the same electrode and lead wire fixing material as described above, in a carbon dioxide gas concentration detecting device whose operating temperature is relatively high as a gas concentration detecting device. It becomes difficult for the lead wire fixing material and the electrode to peel off.

(Embodiment 4) FIG. 5 is a sectional view of a main part of a carbon dioxide sensing element according to Embodiment 4 of the present invention.

In FIG. 5, 51 is a carbon dioxide sensing porous ceramic, 52 is one or more electrodes provided on the surface or inside of the porous ceramic 51, and 56 is a lead wire fixing material. The method for manufacturing the carbon dioxide gas sensing element is the same as the conventional one. The carbon dioxide sensing element in the present embodiment is different from the conventional carbon dioxide sensing element in that the linear thermal expansion coefficient α of the carbon dioxide sensing porous ceramic 51, the linear thermal expansion coefficient β of the electrode 52, and the linear thermal expansion of the lead wire fixing material 56. That is, the coefficients γ are formed such that α ≧ β ≧ γ. In order to prevent separation of the carbon dioxide sensing porous ceramic 51 and the electrode 52, β is preferably equal to or smaller than α, and γ is preferably equal to or smaller than β. This is because the smaller the linear thermal expansion coefficient, the higher the compressive stress, so that a force is applied in such a direction that the linear thermal expansion coefficient does not peel off from the object to be adhered. However, if the difference between α and γ is too large, peeling will occur, so that 2γ ≧ α ≧ γ is desirable.

(Embodiment 5) FIG. 6 is a cross-sectional view of a portion of a carbon dioxide sensing element according to Embodiment 5 of the present invention on which electrodes are adhered on a porous ceramic surface.

In FIG. 6, reference numeral 51 denotes a carbon dioxide sensing porous ceramic which is a carbon dioxide sensing material, and reference numeral 15 denotes one or more electrodes provided on the surface or inside of the carbon dioxide sensing porous ceramic 51.

The electrode 15 is made of one or more of noble metals of gold, platinum, ruthenium and ruthenium oxide.
A paste containing borosilicate glass as a glass component is printed and fired for use. Of these materials, platinum,
Gold, ruthenium, and ruthenium oxide can be mixed into a large amount of glass to form a paste without being separated from glass during firing. In addition, a paste containing ruthenium or ruthenium oxide as a main component and borosilicate glass as a glass component is particularly useful as a heat-resistant resistor paste because ruthenium and ruthenium oxide are precipitated at the grain boundaries of glass particles. Yes, glass components can be mixed and kneaded in a wider range than platinum and gold. When the glass volume is less than 10 vol% with respect to the total electrode volume, the noble metal of gold, platinum, ruthenium, and ruthenium oxide in the paste and the glass are easily separated at the time of firing, and it is difficult to form an electrode having a uniform composition. The noble metal portion peels off, and the electrode itself has a variation in impedance. On the other hand, when it is close to 70 vol%, the bond of the particles on the surface of the porous ceramic is broken by the stress of the glass itself, and peeling is likely to occur. More preferably, 20 to 60
vol%.

[0068]

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

Example 1 Commercially available cerium oxide (CeO)
₂ ), barium carbonate (BaCO ₃ ), cuprous oxide (Cu
O) was weighed at a molar ratio of 5: 2: 3 so that the total amount was 100 g, and ethanol or isopropanol was added to 80 m.
In addition, wet pulverization was performed using zirconia balls in a planetary separation type ball mill.

Next, the powder was dried in an oven, a rotary evaporator or the like to obtain a powder. This is mesh 100μ
m, and sieved with a mesh of 50 μm.

A predetermined amount of this raw material is weighed, placed in a mold, subjected to uniaxial dry molding at a press pressure of about 0.5 ton / cm ² , taken out of the mold, and placed in an electric furnace in an air oven.
It baked at 0 degreeC-900 degreeC for about 5 hours. Both surfaces of the obtained fired body are polished with water-resistant abrasive paper having a mesh of number 1000 or lap-finished with GC abrasive grains of number 1000 to achieve a thickness of 0.1 mm.
The porous ceramic 1 was adjusted to 5 mm.

The surface roughness Rmax was 3 to 5 μm.
m, the minimum pitch adjacent to the uneven step was 2 to 5 μm, and the maximum pitch adjacent to the uneven step was within 5 to 20 μm.

A platinum paste is formed on a substrate 53 made of Al ₂ O ₃ or the like by screen printing or the like, fired and fixed to obtain a wiring 57 for transmitting a signal of the platinum heater 54 and the porous ceramic 1. Was.

Next, a paste obtained by mixing and kneading commercially available ruthenium oxide and borosilicate glass was applied to both polished surfaces of the porous ceramic 1 by screen printing.
It was dried at 0 ° C. for about 30 minutes. The carbon dioxide sensing porous ceramic 5 before the heat treatment, on which the electrode 52 is applied and printed,
1 was placed on a substrate 53 and fired. Here firing is
The temperature was raised from room temperature to 850 ° C. at a rate of 45 ° C./min.
After holding the temperature for 60 minutes, the temperature was lowered at a rate of 60 ° C./minute. Thereby, the porous ceramic 1 and the electrode 52 are connected to the Al ₂ O ₃ substrate 5.
3 fixed on.

Here, the heater 54 is arranged so as to surround the bulky Kanthal wire around the porous ceramic 1,
You may comprise so that it may be opposingly arranged planarly.

The particle sizes of commercially available ruthenium oxide and glass which are the raw materials of the electrode 52 are 0.1 to 0.5 μm and 1 to 1.5 μm, respectively. The surface roughness Rmax6 of the surface of the porous ceramic 1 or the minimum pitch 7 adjacent to the uneven step is larger than the particle diameter of the material of the electrode 52, and the film thickness of the electrode 52 is larger than the maximum pitch 8 adjacent to the uneven step. Because
The electrode 52 fits well into the irregularities on the surface of the porous ceramic 1. The thickness of the electrode 52 need not be larger than the maximum pitch 8 adjacent to the uneven step on the surface of the porous ceramic 1. If it is too large, the electrode 52 itself will peel off due to stress. Practically 10 to 50 μm
Is good. Preferably it is 10 to 25 μm.

Next, the Pt of about 0.1 mm of the bulk material is used.
After the wire is dipped in a platinum paste, which is a lead wire fixing material 56, the wire is brought into close contact with the electrode 52 and fired.
It was set to 5. The firing conditions are as follows: the temperature is raised from room temperature to 900 ° C. at a rate of 45 ° C./min, held for 10 minutes, and then lowered at 60 ° C./min.

By this heat treatment, the lead wire 55 could be fixed to the electrode 52 using the lead wire fixing material 56.

Through the above manufacturing steps, the carbon dioxide sensing element of the present invention shown in FIG. 1 was obtained. The carbon dioxide sensing element was formed by changing the polishing conditions of the porous ceramic surface and the like, and the value of the surface finish and the value of the gap at the contact interface with the electrode were summarized in (Table 1).

[0080]

[Table 1]

According to (Table 1), the gap between the contact interfaces is generated unless Rmax and the minimum pitch of the uneven steps are not larger than the particle diameter of the electrode, and the maximum pitch of the uneven steps is not larger than the film thickness of the electrode. It can be seen that a gap at the contact interface occurs.

(Example 2) As a porous ceramic, C was used.
A fired body containing a mixture of eO ₂ , BaCO ₃ , and CuO will be described. (Table 2) shows CeO ₂ , BaCO ₃ , Cu
Various sols are applied to the surface of the fired body containing the mixture of O
The transverse rupture strength of a material coated to a thickness of ５5 μm and fired at 600 to 800 ° C. was determined by a calculation formula (Equation 1) as a three-point bending strength using a three-point supporting jig.

[0083]

(Equation 1)

The results are summarized in (Table 2).

[0085]

[Table 2]

As can be seen from (Table 2), the coated or printed silica sol, alumina sol, zirconia sol, or glass paste has a high surface bending strength and enhanced mechanical bonding of particles. Recognize.

FIG. 7 shows a porous ceramic for detecting carbon dioxide gas.
For those coated and not coated with sol,
It is a graph which shows the time-dependent change of the capacity value at the time of continuous heating at an operating temperature. According to the results, the capacitance value of the material coated with the sol of silica, alumina or zirconia is not deteriorated as compared with the case of not coating. This indicates that the porous ceramic and the electrode are firmly adhered.

Example 3 A fired body containing, for example, a mixture of CeO ₂ , BaCO ₃ , and CuO as a porous ceramic will be described. FIG. 8 is a graph showing the change over time of the capacitance value when the electrode of the carbon dioxide gas sensing element and the lead wire fixing material are changed and when the heating is continuously performed at the operating temperature.
According to this, it is understood that the change over time is smaller when the same material is used for the electrode and the lead wire fixing material.

Table 3 shows CeO ₂ , BaCO ₃ , Cu
This is the linear thermal expansion coefficient of the fired body containing the mixture of O, the electrode, and the lead wire fixing material from room temperature to around the operating temperature.

[0090]

[Table 3]

Referring to the values in Table 3 and FIG. 8, it is clear that when the combination is made so that α ≧ β ≧ γ as much as possible, the change with time in the capacitance value is small and the porous ceramic and the electrode are firmly connected. It can be seen that it is closely adhered to.

Example 4 A fired body containing, for example, a mixture of CeO ₂ , BaCO ₃ , and CuO as a porous ceramic will be described. (Table 4) shows the contact interface when a noble metal paste containing any one of platinum, gold, and ruthenium oxide is used as an electrode and mixed and kneaded with a glass component such as borosilicate glass. 5 shows the maximum gap and the peeling state that have occurred.

[0093]

[Table 4]

[0094] According to Table 4, when the volume ratio of glass is 10 to 65 vol%, no peeling occurs. In addition, preferably, the maximum gap at the contact interface is 25 μm to 60 vol%, which is 1.0 μm or less, and good adhesion is obtained.

Example 5 A fired body containing, for example, a mixture of CeO ₂ , BaCO ₃ , and CuO as a porous ceramic will be described. FIG. 9 shows that the electrode is mixed with CuO, one of the constituent materials of the carbon dioxide sensing porous ceramic.
It is a graph which shows the time-dependent change of the capacity value at the time of kneading.
According to this, it was found that the change over time was smaller when CuO was mixed and kneaded with the glass component of the electrode material. That is, CuO in the electrode is changed to CuO on the surface of the porous ceramic.
Chemically reacts with, indicating that they are tightly adhered.

(Example 6) A fired body containing, for example, a mixture of CeO ₂ , BaCO ₃ , and CuO as a porous ceramic will be described. FIG. 10 shows Embodiment 6 of the present invention.
It is a perspective view which shows the carbon dioxide detection element by using. First, commercially available CeO ₂ , BaCO ₃ , and CuO were respectively added to 7: 1: 2.
100 g was weighed so that the molar ratio was as follows. To this was added 100 ml of a solvent such as ethanol or isopropanol, and wet grinding was performed using a zirconia ball of 2 mm in a planetary separation type ball mill. Thereafter, the powder was dried in an oven, a rotary evaporator or the like to obtain a powder. This was sieved with a mesh of 100 μm and a mesh of 50 μm to granulate. 2 g of the granulated material is weighed and is
And subjected to uniaxial dry molding at a press pressure of about 1 ton / cm ² , taken out of the mold, and placed in an electric furnace for 80 hours.
It baked in air at 0 degreeC-900 degreeC for about 5 hours. After firing, use a water-resistant abrasive paper with a mesh size of 1000
The surface of No. 0 was polished on both sides to a thickness of 0.5 mm. Thus, the porous ceramic 1 was obtained.

By the above operation, the surface roughness Rmax of the surface of the porous ceramic 1 is 3 to 5 μm, the minimum pitch adjacent to the uneven surface is 2 to 5 μm, and the maximum pitch adjacent to the uneven surface is 5 to 20 μm. It could be processed to be within the range.

The platinum heater 54 and the wiring 57 were obtained by forming a platinum paste on the substrate 53 by screen printing or the like, and sintering and fixing the paste.

Next, a paste obtained by mixing and kneading commercially available ruthenium oxide and borosilicate glass was applied to both polished surfaces of the polished porous ceramic 1 by screen printing, and dried at 120 ° C. for about 30 minutes. This was placed on a substrate 53 and fixed by firing. The firing conditions were as follows: the temperature was raised from room temperature to 850 ° C. at a rate of 45 ° C./min, held for 10 minutes, and then lowered at 60 ° C./min. Thus, the porous ceramic 1 and the electrode 52 were fixed on the substrate 53.

As the electrode material, a conductive paste obtained by mixing platinum or gold and a glass component and having a glass volume of 10 to 65 vol% with respect to the total volume of the fired electrode is used. Further, the porous ceramic 1 and the electrode 52 could be contacted with good adhesion.

Further, CuO which is one of the constituent materials of the porous ceramic 1 is added to the glass component of the material of the electrode 52 by 10 V.
ol%, mixing and kneading, and the rate of temperature rise from room temperature to 45 ° C
/ Min after heating to 950 ° C for 10 minutes.
When sintering was performed under sintering conditions in which the temperature was lowered in minutes, it chemically reacted with the surface of the porous ceramic 1 and could be firmly adhered. Other porous ceramic components such as CeO ₂ and B
It was found that even if aCO ₃ was mixed, the adhesion did not improve, but rather worsened.

The electrode 52 was formed to have a thickness of 10 to 50 μm. The particle sizes of commercially available ruthenium oxide and glass were 0.1 to 0.5 μm and 1 to 1.5 μm, respectively. The surface roughness Rmax of the surface of the porous ceramic 1 or the minimum pitch adjacent to the uneven step is larger than the particle diameter of the material of the electrode 52, and the film thickness of the electrode 52 is larger than the maximum pitch adjacent to the uneven step. The electrode 52 fits well into the irregularities on the surface of the porous ceramic 1. Electrode 52
Is not necessarily larger than the maximum pitch adjacent to the uneven steps on the surface of the porous ceramic 1.
It has been confirmed that, if it is too large, peeling occurs due to the stress of the electrode itself.

Next, a Pt wire having a diameter of 0.1 mm of the bulk material is dipped in a ruthenium oxide paste, which is the same lead wire fixing material 56 as the material of the electrode 52, and then closely adhered to the electrode 52 and baked. The wire 55 was used. The firing conditions were as follows: the temperature was raised from room temperature to 900 ° C. at a rate of 45 ° C./min, held for 10 minutes, and then lowered at 60 ° C./min.

By this heat treatment, the lead wire fixing material 56
, The lead wire 55 can be fixed to the electrode 52. And the lead wire 55 and the lead wire fixing material 56 were obtained.

The thermal expansion coefficient α of the porous ceramic 1 formed as described above ranges from room temperature to 550 ° C., which is the operating temperature.
Up to 8.5 to 9.5 × 10 ⁻⁶ . On the other hand, commercially available noble metal pastes of platinum, gold, and ruthenium oxide are 3.0.
２20.0 × 10 ⁻⁶ , but β and γ are 3.0 × 10
It was found that, when it was smaller than ⁻⁶ or exceeded 15.0 × 10 ⁻⁶ , the carbon dioxide sensing porous ceramic 51 and the electrode 52 were easily peeled off. In the present invention, (α−
(β) and (α-γ) were 5 × 10 ⁻⁶ and good adhesion was confirmed, but (α-β) and (α-γ) were 3.0 × 1 each.
Be in the range of about 0 ^-6 it has been found to be more preferable.

[0106]

According to the invention as set forth in claim 1 of the present invention, the constituent particles of the electrode can be fitted all over the uneven portion of the porous ceramic surface, and the uneven portion can be inserted. Since the most part can be covered by the thickness of the electrode, in a carbon dioxide gas concentration detecting device whose operating temperature is relatively high, the constituent particles of the electrode without any gaps in the uneven shape of the porous ceramic surface which is a carbon dioxide gas detecting material. Can be attached, so that the adhesion can be significantly improved. In addition, it is possible to provide a carbon dioxide sensing element that has high reliability without peeling even at an operating temperature and has a uniform contact area for each carbon dioxide sensing element, so that there is little characteristic variation among the elements. Can be.

According to the second aspect of the present invention,
Since SiO ₂ , AlO ₃ , and ZrO ₂ serve as binders for inorganic materials, the surface of the porous ceramic can be strengthened, and the electrodes are firmly adhered to each other. It is possible to prevent the electrode from being separated due to the destruction.

According to the third aspect of the present invention,
A strong chemical bond is easily obtained by firing, and the linear thermal expansion coefficient of the material of the electrode and the lead wire fixing material becomes the same, so that the generation of thermal stress can be reduced even at a relatively high operating temperature. In addition, the adhesion between the porous ceramic surface and the deposited electrode can be significantly improved.

According to the invention described in claim 4 of the present invention,
Since the difference in linear thermal expansion coefficient between each contact surface between the porous ceramic and the electrode, and between the electrode and the lead wire fixing material can be reduced, the thermal stress can be reduced, and the linear thermal expansion coefficient is small. Since the surface shows relatively compressive stress, a force is applied in a direction in which the porous ceramic surface is not peeled off from the object to be adhered, so that the adhesion between the porous ceramic surface and the electrode to be adhered can be significantly improved. .

According to the fifth aspect of the present invention,
In addition to the effect of the invention according to any one of claims 1 to 4, the electrode contains a noble metal and / or a noble metal oxide, so that it can maintain good conductivity even at a relatively high operating temperature. As well as being firmly adhered to the porous ceramic by the glass component.

According to the invention described in claim 6 of the present invention,
In addition to the effects of the invention according to any one of claims 1 to 5, the porous ceramic surface and the electrode may be made of at least one kind of raw material of the porous ceramic contained in a glass component. With a strong chemical affinity, significantly improving the adhesion between the porous ceramic surface and the deposited electrode even at relatively high operating temperatures, and the effect of thermal stress. Since the adhesion between the electrode and the surface of the porous ceramic can be obtained, the heat resistance is increased and the change with time is reduced.

According to the seventh aspect of the present invention,
In addition to the effects of the invention described in claim 1, CeO ₂ , Ba
By containing a mixture of CO ₃ and CuO, a sensing element having high sensitivity to carbon dioxide gas can be obtained, and the adhesion between the porous ceramic and the electrode can be significantly increased.

According to the invention described in claim 8 of the present invention,
In addition to the effects of the invention described in claim 7, the electrode materials such as ruthenium oxide, platinum, and gold are more excellent in heat resistance and moisture resistance at operating temperatures than silver, palladium, copper, and the like. Since the surface of the porous ceramic and the electrode can be brought into close contact with each other without peeling or destruction, a stable carbon dioxide sensing element with little change over time can be obtained.

According to the ninth aspect of the present invention,
In addition to the effect of the invention according to claim 7, since the maximum pitch of the irregularities of the porous ceramic is smaller than the thickness of the electrode, the adhesion can be significantly improved.

According to the tenth aspect of the present invention, in addition to the effect of the seventh aspect, when the electrode paste material is fired, the surface of the porous ceramic and the electrode are particularly It is possible to make close contact with a strong chemical bonding force and to reduce the difference in linear thermal expansion coefficient between the porous ceramic and the electrode. CuO or C
Since u ₂ O is partially sublimated and easily diffused by the heat treatment, it can be adhered more strongly.

According to the eleventh aspect of the present invention, in addition to the effects of the seventh aspect, each contact between the porous ceramic and the electrode, and between the electrode and the lead wire fixing material. The difference in coefficient of linear thermal expansion between the surfaces can be reduced, so that the thermal stress can be reduced. Because force is applied in the direction,
The adhesion between the porous ceramic surface and the deposited electrode can be significantly improved.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a carbon dioxide sensing element according to a first embodiment of the present invention.

FIG. 2 is an enlarged view of a portion A in FIG.

FIG. 3 is an end view of a portion of a carbon dioxide gas sensing element according to a second embodiment of the present invention where electrodes are attached.

FIG. 4 is a sectional view of a main part of a carbon dioxide sensing element according to a third embodiment of the present invention.

FIG. 5 is a sectional view of a main part of a carbon dioxide sensing element according to a fourth embodiment of the present invention.

FIG. 6 is a cross-sectional view of a portion of a carbon dioxide sensing element according to a fifth embodiment of the present invention, on which electrodes are attached on the surface of a porous ceramic.

FIG. 7 is a graph showing the change over time of the capacitance value when the porous ceramic surface is continuously heated at the operating temperature with and without the sol coating.

FIG. 8 is a graph showing the change over time of the capacitance value when continuously heated at the operating temperature when the electrode of the carbon dioxide sensing porous ceramic element and the lead wire fixing material are changed.

FIG. 9 is a graph showing the change over time of the capacitance value when CuO, which is one of the constituent materials of the carbon dioxide sensing porous ceramic, is mixed and kneaded in the electrode.

FIG. 10 is a perspective view showing a carbon dioxide sensing element according to Embodiment 6 of the present invention.

FIG. 11 is a perspective view showing a configuration of a conventional impedance change type carbon dioxide gas detecting element.

FIG. 12 is an enlarged view of a portion B in FIG. 11;

[Explanation of symbols]

 Reference Signs List 1 Porous ceramic 6 Surface roughness Rmax 7 Minimum pitch adjacent to uneven step 8 Maximum pitch adjacent to uneven step 10 Oxide 11 Lead wire fixing material 15 Electrode 51 Carbon dioxide sensing porous ceramic 52 Electrode 53 Substrate 54 Platinum heater 55 Lead wire 56 Lead wire fixing material 57 Wiring 58 Gap α Linear thermal expansion coefficient of carbon dioxide sensing porous ceramic β Linear thermal expansion coefficient of electrode γ Linear thermal expansion coefficient of lead wire fixing material

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Shogo Matsubara 1006 Kazuma Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd.

Claims (11)

[Claims] 1. A porous ceramic as a carbon dioxide sensing material, one or more electrodes provided on or on the surface of the porous ceramic, and a lead wire connected to the surface or on the inside of the electrode. A lead wire fixing material for connecting and fixing the electrode and the lead wire, a heater capable of heating the porous ceramic to an operating temperature, a substrate on which the porous ceramic and the heater can be arranged, and a power supply arranged on the substrate And a wiring for use in the carbon dioxide gas detection element, wherein the electrode has a surface roughness Rmax of the surface of the porous ceramic on which the electrode is adhered and / or an adjacent minimum pitch of the uneven steps constitutes the electrode. A carbon dioxide gas detecting element, wherein the maximum pitch adjacent to the uneven step is equal to or less than the thickness of the electrode. 2. A porous ceramic which is a carbon dioxide sensing material, one or more electrodes provided on or on the surface of the porous ceramic, and a lead wire connected to the surface or on the inside of the electrode. A lead wire fixing material for connecting and fixing the electrode and the lead wire, a heater capable of heating the porous ceramic to an operating temperature, a substrate on which the porous ceramic and the heater can be arranged, and a power supply arranged on the substrate A sensing layer comprising: an oxide layer containing at least one of SiO ₂ , Al ₂ O ₃ , and ZrO _{2 on} a surface of the porous ceramic on which the electrode is adhered. A carbon dioxide sensing element characterized by being sintered. 3. A porous ceramic which is a carbon dioxide detecting material, one or more electrodes provided on or on the surface of the porous ceramic, and a lead wire connected to the surface or on the inside of the electrode. A lead wire fixing material for connecting and fixing the electrode and the lead wire, a heater capable of heating the porous ceramic to an operating temperature, a substrate on which the carbon dioxide sensing porous ceramic and the heater can be arranged, and an arrangement on the substrate And a wiring for energization, wherein the electrode and the lead wire fixing material are formed of the same material. 4. A porous ceramic serving as a carbon dioxide sensing material, one or more electrodes provided on or on the surface of the porous ceramic, and a lead wire connected to the surface or on the inside of the electrode. A lead wire fixing material for connecting and fixing the electrode and the lead wire, a heater capable of heating the porous ceramic to an operating temperature, a substrate on which the porous ceramic and the heater can be arranged, and a power supply arranged on the substrate A wire for thermal expansion, comprising: a linear thermal expansion coefficient α of the porous ceramic; a linear thermal expansion coefficient β of the electrode; and a linear thermal expansion coefficient γ of the lead wire fixing material. Have a relationship of α ≧ β ≧ γ. 5. The electrode is formed by firing a paste containing a noble metal and / or a noble metal oxide and a glass component, and the fired electrode contains 10 to 65 vol of the glass component.
The carbon dioxide sensing element according to any one of claims 1 to 4, wherein the content is preferably 20 to 60 vol%. 6. The electrode is formed by firing a paste containing a noble metal and / or a noble metal oxide and a glass component containing at least one of raw materials of the carbon dioxide sensing porous ceramic. The carbon dioxide sensing element according to any one of claims 1 to 5, wherein: 7. A porous ceramic material for detecting carbon dioxide gas.
Provided on the surface or inside of the porous ceramic
One or more electrodes, on or in the electrodes
Connect the connected lead wire, the electrode and the lead wire
Lead wire fixing material to be fixed, and the porous ceramic
A heater capable of heating to an operating temperature, and the porous ceramic
And a substrate on which the heater can be disposed, and a substrate disposed on the substrate.
Carbon dioxide sensing element with
And the porous ceramic is CeO _Two, BaCO_Three, Cu
Surface roughness of a surface containing a mixture of O and on which the electrode is deposited
Rmax is not less than 0.5 μm and not more than 5 μm.
The switch is 3 μm or more and 25 μm or less,
Characterized in that the diameter is 0.05 μm or more and less than 3 μm.
The carbon dioxide sensing element according to claim 1. 8. The electrode is formed by firing a paste containing at least one of ruthenium oxide, platinum, and gold and a glass component, and the electrode after firing has a glass component of 10 to 10%. 65 vol%, preferably 30 to 45 vol
The carbon dioxide sensing element according to claim 7, wherein the carbon dioxide sensing element is contained. 9. The carbon dioxide sensing element according to claim 7, wherein said electrode has a thickness of 10 to 50 μm, preferably 10 to 25 μm. 10. The carbon dioxide sensing element according to claim 7, wherein the paste material for forming the electrode contains CuO or Cu ₂ O as a glass component. 11. The coefficient of linear thermal expansion α of the porous ceramic
And the linear thermal expansion coefficient β of the electrode and the linear thermal expansion coefficient γ of the lead wire fixing material have a relationship of α ≧ β ≧ γ, and (α−β) and (α− γ) is 5 × 10
The carbon dioxide sensing element according to claim 7, wherein the temperature is ^-6 (/ deg) or less.