JP2001302357A - Method of producing ceramic, ceramic, and sensor and catalyst using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of producing a porous ceramic by which the porous ceramic free from dispersion in the composition, excellent in crystallinity and suitable as a sensor or a catalyst can be easily obtained without firing at a high temperature. SOLUTION: The porous ceramic is obtained by dissolving a compound containing at least one metal element constituting the ceramic into water or an acid to obtain an aqueous solution, then adding a complexing agent, an alcohol having at least two hydroxyl groups and an oxidant into the solution, heating the resultant solution to obtain an organometallic compound and burning/sintering the organometal compound by heating it. As the compound containing the metal element, a compound containing a rare earth element, a transition element or an alkaline earth element is suitable. Citric acid, 1,2-dihydroxyethane and nitric acid are suitable as the complexing agent, the alcohol and the oxidant, respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a porous ceramic, a ceramic obtained by the method, and a sensor and a catalyst using the ceramic.

[0002]

2. Description of the Related Art Conventionally, as a method for producing ceramics, a dry method using powder as a raw material has been put to practical use as a method for mass production. In this method, using powders such as metal oxides and carbonates as starting materials, mixing, calcining, pulverizing,
It is manufactured through molding and firing processes.

[0003] In recent years, there have been proposed many methods for producing ceramics by a so-called wet method using a compound soluble in water or an organic solvent as a starting material. A mixed solution of a compound containing a ceramic component is prepared, and a precipitate obtained by adding a precipitant or the like thereto is used as a raw material, and then calcined, pulverized, molded, and manufactured through a process of firing. is there. Specifically, for example, there is a method in which a metal alkoxide is used as a starting material, and a precipitate obtained by hydrolyzing this solution is used as a starting material. Other methods include a solution polymerization method using citric acid and a diol.

Further, a method for producing ceramics by a vapor phase synthesis method such as a CVD method has been proposed.

[0005]

However, in the case of the ceramic production by the conventional dry method, expensive equipment such as a crusher and a firing furnace is required as a production equipment, and many steps are required until the ceramic is obtained. Since a long time is required after that, there is a problem in cost that further cost reduction is limited. In addition, when obtaining a composite oxide ceramic composed of two or more types of metal oxides, the starting material powder such as a metal oxide has a large particle size, so that uniform reaction cannot be achieved by firing, and microscopic There is a quality problem that a large variation in composition cannot be avoided.

In the case of producing a ceramic by a wet method, for example, in a method using a metal alkoxide as a starting material, the starting material is mixed in a solution state. Can be obtained. However, in the case of this method, in order to obtain a ceramic, it is necessary to bake the precipitate obtained by hydrolyzing the metal alkoxide at a high temperature, and there is a problem in cost as in the case of the dry method.

In the case of a solution polymerization method using citric acid and a diol, the polymerization product is an amorphous metal compound containing a large amount of organic components. For this reason, in order to obtain a ceramic having high crystallinity, it is necessary to bake the polymerization product at a high temperature, and there is a problem in cost as in the case of the dry method.

[0008] Further, the vapor phase synthesis method such as the CVD method can obtain a homogeneous ceramic, but the equipment to be used is expensive and the mass productivity is poor, and the organometallic material as a raw material is expensive. For example, the applicable range is limited.

Accordingly, an object of the present invention is to solve the above-mentioned problems, to suppress the composition variation by a simple method without high-temperature sintering, and to have excellent crystallinity and suitable for a sensor or a catalyst. An object of the present invention is to provide a method for manufacturing a porous ceramic. Also, the ceramic obtained thereby,
Another object of the present invention is to provide a sensor and a catalyst using the ceramic.

[0010]

In order to achieve the above object, a method of manufacturing a ceramic according to the present invention comprises dissolving a compound containing a metal element constituting a ceramic in water or an acid to form an aqueous solution. A complex forming agent, an alcohol having two or more hydroxyl groups, and an oxidizing agent, and heating to obtain an organometallic compound. The organometallic compound is further heated, burned, and sintered. And

Further, the ceramic of the present invention is obtained by adding a complex forming agent, an alcohol having at least two hydroxyl groups, and an oxidizing agent to an aqueous solution of a compound containing a metal element constituting the ceramic and heating the mixture. It is characterized by being.

In the method for producing a ceramic and the ceramic according to the present invention, the compound containing the metal element is a rare earth element (provided that the atomic numbers are 39 and 57 to 7 to 7).
1), a transition element (however, an element having an atomic number of 23 to 28) and an alkaline earth element (however, an atomic number of 1)
(2, 20, 38 and 56 elements) is an oxide or salt of at least one element selected from the group consisting of:

The complex forming agent is citric acid,
The alcohol having two or more hydroxyl groups is 1,2-dihydroxyethane, and the oxidizing agent is nitric acid.

The ceramic is porous and is a ceramic for a sensor.

In the case of a sensor ceramic, the compound containing the metal element includes at least a rare earth element (at least one of atomic numbers 39 and 57 to 71) and a transition element (atomic number 23). ~ 2
And at least one element selected from atomic numbers 12, 20, 38, and 56.

A sensor according to the present invention includes a pair of electrodes and a sensor material disposed between the electrodes, wherein the sensor material is the above ceramic.

Further, the ceramic is porous and is a catalyst ceramic.

In the case of a ceramic for a catalyst, the compound containing the metal element includes at least a rare earth element (at least one element of atomic numbers 39 and 57 to 71) and a transition element (atomic number 23 ~
At least one element of the above 28).

Further, the catalyst of the present invention is characterized in that the above ceramic is used as a catalyst material.

The compound containing a metal element used in the method for producing a ceramic according to the present invention is, for example, a compound containing a rare earth element, a compound containing a transition element, a compound containing an alkaline earth element, and the like. There is no particular limitation as long as it does.

The complexing agent used in the present invention can be applied to any organic acid having at least two acetyl groups and at least one hydroxyl group. It is more preferable to use citric acid, which reduces the reduction.

Examples of the alcohol having two or more hydroxyl groups include 1,2-dihydroxyethane, 1,3-dihydroxypropane, 1,2-dihydroxypropane, and 1,2-dihydroxypropane.
Examples thereof include dimethylhydroxypropane, 1,2,3-trihydroxypropane, and 1,2,3-trimethylhydroxypropane, and any alcohol having at least two hydroxyl groups on a hydrocarbon may be used. is not. However, among alcohols having two or more hydroxyl groups, alcohols having a small number of carbon atoms are preferable because the amount of residual carbon after ceramic formation is reduced, and for example, 1,2-dihydroxyethane is preferable.

The oxidizing agent to be added in the present invention includes
Nitric acid is preferred. The amount of addition is preferably such that the amount of excess nitric acid after dissolving the compound of the metal element constituting the ceramic becomes 0.2 mol / L or more.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION In the method for producing a ceramic according to the present invention, a compound containing a metal element constituting a ceramic is dissolved in water or an acid to form an aqueous solution. After mixing and heating an alcohol having a hydroxyl group and an oxidizing agent to obtain an organometallic compound, the organometallic compound is further heated, burned, and sintered. Further, the ceramic of the present invention,
It is characterized by being obtained by adding a complexing agent, an alcohol having two or more hydroxyl groups, and an oxidizing agent to an aqueous solution of a compound containing a metal element constituting ceramic and heating the mixture. The sensor and the catalyst of the present invention use the above-mentioned ceramic as a sensor material and a catalyst material, respectively.

Hereinafter, the method for producing a ceramic according to the present invention will be described.

First, a compound containing a metal element constituting the ceramic (for example, a compound containing a rare earth element, a compound containing a transition element, a compound containing an alkaline earth element, etc.)
Weigh to the desired ceramic composition. Thereafter, these compounds are mixed and dissolved by adding water. The amount of water to be added is not particularly limited. However, since it is necessary to evaporate and remove water in a subsequent step, it is preferable that the amount of water to be added is as small as possible within a range in which the compound containing the metal element can be dissolved. In the normal case, it is preferable to add water so that the metal ion concentration around 0.6 mol / L subsides. When the compound is hardly soluble in water, an acid such as nitric acid is added and dissolved while heating.

Then, after the compound containing the metal element is completely dissolved, nitric acid as an oxidizing agent is further added so as to have a solution concentration of 0.2 mol / L or more.

Next, a complex-forming agent is added to the obtained aqueous solution. The amount of the complexing agent to be added is not particularly limited as long as it is equal to or more than the number of moles of the ceramic expected to be formed, but is preferably 1 to 5 times the number of moles of the metal ions in the solution. Then, the mixture is stirred while heating to completely dissolve the complex forming agent. In this case, when the dissolution is extremely slow, a small amount of water can be added to accelerate the dissolution. It should be noted that there is no particular need to heat as long as it is easily dissolved.

Next, an alcohol having two or more hydroxyl groups is added. The amount of the alcohol is not particularly limited, but is preferably 1 to 0.5 times the number of moles of the complexing agent.

Next, the mixed solution thus obtained is heated to 150 ° C. or higher while stirring to evaporate water and concentrate. The heating temperature may be such that the solvent is evaporated and the mixed solution is concentrated, but the heating temperature is preferably from 200C to 250C. The viscosity of the mixed solution increases as the concentration proceeds.
Here, the solution volume of this mixed solution is ２〜 to 1 of the initial volume.
The heating temperature was increased from the point of time when the
Heat at a temperature between ℃ and 350 ° C.

In the process of concentrating the mixed solution, it is necessary to keep the mixed solution transparent. If an insoluble matter is formed and becomes opaque, nitric acid is appropriately added to dissolve the insoluble matter. When the heating and concentration are further continued, a film of the organometallic compound is generated on the surface of the mixed solution. Inside the organic metal compound film, gas is generated due to decomposition and / or evaporation of the solution and the organic metal compound, and generation of fine bubbles is confirmed on the surface of the mixed solution. If heating is further continued in this state, spontaneous ignition occurs inside the film of the organometallic compound and a sintering reaction occurs to produce ceramic powder.

In the method for producing a ceramic according to the present invention, a metal ion as a raw material is reacted in a solution state with a hydrogen ion of a hydroxyl group of a complexing agent, and further condensed with an acetyl group of the complexing agent and a hydroxyl group of an alcohol. Since an organometallic compound obtained by causing a polymerization reaction is used as a production intermediate, a uniform ceramic material can be synthesized at an atomic level. Since the obtained organometallic compound is highly viscous, further heating causes a large number of fine bubbles to be generated by the solution and gas generated by decomposition and evaporation of the organometallic compound, and self-burns into the organometallic compound. The reaction occurs as a sintering reaction, producing a ceramic. Therefore, a porous ceramic can be easily produced from a solution in one step without using a firing furnace.

Further, in the method for producing a ceramic according to the present invention, since the fine bubbles of the organometallic compound are instantaneously heated to a high temperature by a self-combustion reaction, it is possible to synthesize a crystalline ceramic having fine primary particles. In addition, surplus components such as organic substances are also removed by this combustion reaction, and high-purity ceramic can be manufactured in a short time.

The ceramics thus produced can be directly used for sensors, catalysts, etc., taking advantage of their porous nature.

[0035]

(Example 1) First, the ceramic of the present invention was
It was produced as follows.

That is, lanthanum oxide, which is an oxide of a rare earth element, and manganese nitrate hexahydrate, which is a salt of a transition element, were prepared as compounds containing a metal element constituting a ceramic. Thereafter, 32.582 g of lanthanum oxide and 57.408 g of manganese nitrate hexahydrate were collected in a 500 ml beaker, and 200 ml of distilled water was added. The above solution was heated and dissolved to obtain an aqueous solution.

Next, distilled water was added to the obtained aqueous solution to make a total volume of 350 ml, and then 42.02 g of citric acid as a complexing agent was added and dissolved by stirring. Thereafter, 11.669 g of 1,2-dihydroxyethane as an alcohol having two or more hydroxyl groups was added and mixed. afterwards,
Distilled water was added to make the total volume 400 ml, and while stirring, the heating temperature was raised to 250 ° C., and the mixed solution was concentrated.

Next, the mixed solution whose total amount was concentrated to 150 ml was transferred to a 300 ml porcelain evaporating dish, and the concentration of the mixed solution was further promoted at a temperature of 300 ° C. or higher. The liquid volume is 100m
At the time when the value became 1 or less, a sintering reaction by a self-combustion reaction occurred, and a powdery ceramic of a lanthanum-manganese composite oxide was obtained.

As a comparative example, a ceramic was obtained as follows.

That is, lanthanum chloride heptahydrate and manganese nitrate hexahydrate were prepared as compounds containing metal elements constituting the ceramic. Thereafter, 74.27 g of lanthanum chloride heptahydrate and 57.408 g of manganese nitrate hexahydrate
Was placed in a 500 ml beaker, 200 ml of distilled water was added, and the mixture was heated and dissolved on a hot plate at 200 ° C. with stirring to obtain an aqueous solution.

Next, distilled water was added to the obtained aqueous solution to make a total volume of 350 ml, and then 42.02 g of citric acid was added and stirred to dissolve. Thereafter, 11.669 g of 1,2-dihydroxyethane was added and mixed. Thereafter, distilled water was added to make a total volume of 400 ml.
The temperature was raised to 50 ° C., and the concentration of the mixed solution was advanced.

Next, the mixed solution whose total amount was concentrated to 150 ml was transferred to a 300 ml porcelain evaporating dish, and the mixed solution was further concentrated at a temperature of 300 ° C. or higher to obtain a carbonized powdery ceramic.

The obtained ceramic was subjected to X-ray diffraction analysis. The results are shown in FIGS. FIG.
Is an X-ray diffraction chart of a ceramic obtained in an example of the present invention, and FIG. 2 is an X-ray diffraction chart of a ceramic of a comparative example. As shown in FIG. 1, the peak of the lanthanum-manganese composite oxide was recognized in the ceramics obtained in the examples of the present invention, and it was found that the ceramics having excellent crystallinity were synthesized. On the other hand, the ceramic of the comparative example has no X-ray diffraction peak and is amorphous.
No crystalline ceramic has been obtained.

With respect to the ceramics of Examples and Comparative Examples, the ignition loss at 1000 ° C. for 2 hours was measured. Table 1 shows the results.

[0045]

[Table 1]

As is clear from Table 1, in the present invention, since the organic component is burned off by the self-combustion reaction, the ignition loss is as small as 1.38 wt%. On the other hand, in the comparative example, since the self-combustion reaction does not occur, the ignition loss is as high as 14.2% by weight, and it can be seen that a large amount of residual organic components is contained.

FIGS. 3 and 4 show electron micrographs of the samples of Examples and Comparative Examples. FIG. 3 is an electron micrograph of a ceramic obtained in an example of the present invention, and FIG. 4 is an electron micrograph of a comparative example. Figures 3 and 4
As is clear from the comparison, the Example is a porous ceramic powder, whereas the Comparative Example has a large granular powder. This difference is considered to be because, in the present invention, a porous ceramic powder is obtained by sintering the organometallic compound having fine bubbles by a self-combustion reaction.

Next, the catalytic performances of the ceramics of the examples and comparative examples obtained as described above were compared. That is, when a CO gas was brought into contact with the obtained powdery ceramic and the ceramic was used as a CO oxidation reaction catalyst, the relationship between the temperature and the rate of change from CO to CO ₂ was determined.
FIG. 5 shows the results.

As is apparent from FIG. 5, the ceramic of the present invention has a higher conversion efficiency of CO into CO ₂ than the comparative example, and is excellent as a ceramic for a catalyst in a CO oxidation reaction. This is due to the fact that the powder produced in the present invention is crystalline and has a microscopic pore structure as compared with the comparative example, and has a large contact area with the reaction gas.

Example 2 First, a ceramic of the present invention was produced as follows.

That is, lanthanum oxide which is an oxide of a rare earth element, manganese nitrate hexahydrate which is a salt of a transition element, and strontium carbonate which is a salt of an alkaline earth element are used as a compound containing a metal element constituting a ceramic. Was prepared. Thereafter, 29.32 g of lanthanum oxide, 57.41 g of manganese nitrate hexahydrate and 2.74 g of strontium carbonate.
After dispensing 95 g into a 500 ml beaker, distilled water 200
Then, 60 ml of nitric acid having a concentration of 60% was added with stirring, and the mixture was heated on a hot plate at 200 ° C. to dissolve these compounds to obtain an aqueous solution.

Next, distilled water was added to the obtained aqueous solution to make a total volume of 350 ml, and then 42.02 g of citric acid as a complexing agent was added and dissolved by stirring. Thereafter, 11.669 g of 1,2-dihydroxyethane as an alcohol having two or more hydroxyl groups was added and mixed. afterwards,
Distilled water was added to make the total volume 400 ml, and while stirring, the heating temperature was raised to 250 ° C., and the mixed solution was concentrated.

Next, the mixed solution whose total amount was concentrated to 150 ml was transferred to a 300-ml porcelain evaporating dish, and further concentrated at a temperature of 300 ° C. or higher. The liquid volume is 100m
At the time point when the temperature became 1 or less, a sintering reaction by a self-combustion reaction occurred, and a powdery ceramic of a lanthanum manganese strontium composite oxide was obtained.

As a comparative example, a ceramic was obtained as follows.

That is, lanthanum chloride heptahydrate, manganese nitrate hexahydrate, and strontium carbonate were prepared as compounds containing metal elements constituting the ceramic.
Thereafter, 44.15 g of lanthanum chloride heptahydrate, 57.41 g of manganese nitrate hexahydrate, and 2.95 g of strontium carbonate were dispensed into a 500 ml beaker, and distilled water 200
Then, the mixture was heated and dissolved on a hot plate at 200 ° C. with stirring to obtain an aqueous solution.

Next, distilled water was added to the obtained aqueous solution to make the total volume 350 ml, and then 42.02 g of citric acid was added and stirred to dissolve. Thereafter, 11.669 g of 1,2-dihydroxyethane was added and mixed. Thereafter, distilled water was added to make a total volume of 400 ml.
The temperature was raised to 50 ° C., and the concentration of the mixed solution was advanced.

Next, the mixed solution whose total amount was concentrated to 150 ml was transferred to a 300 ml porcelain evaporating dish, and the mixed solution was further concentrated at a temperature of 300 ° C. or higher to obtain a carbonized powdery ceramic.

The obtained ceramic was subjected to X-ray diffraction analysis. As a result, in the ceramics obtained in the examples of the present invention, the peak of the lanthanum manganese strontium composite oxide was recognized, and ceramics having excellent crystallinity were synthesized. On the other hand, the ceramic of the comparative example did not show an X-ray diffraction peak, was amorphous, and could not obtain a crystalline ceramic.

For the ceramics of the examples and comparative examples, the ignition loss at 1000 ° C. for 2 hours was measured. Table 2 shows the results.

[0060]

[Table 2]

As is evident from Table 2, in the present invention, since the organic component is burned off by the self-combustion reaction, the ignition loss is small. On the other hand, in the comparative example, since the self-combustion reaction does not occur, the ignition loss is large, and it can be seen that the residual organic content is very large.

FIGS. 6 and 7 show electron micrographs of the samples of Examples and Comparative Examples. FIG. 6 is an electron micrograph of a ceramic obtained in an example of the present invention, and FIG. 7 is an electron micrograph of a comparative example. 6 and 7
As is clear from the comparison, the Example is a porous ceramic powder, whereas the Comparative Example has a large granular powder.

Next, humidity sensors were manufactured using the ceramics of the examples and comparative examples obtained as described above.

That is, the obtained powdery ceramic 1
0 g was taken in a 100 ml beaker, 50 ml of distilled water and 10 ml of a 10% aqueous solution of polyvinyl alcohol were added, and the mixture was stirred and mixed to prepare a slurry.

Next, the obtained slurry was applied on a pair of opposing comb electrodes on an alumina substrate,
Baking for 2 hours at 800 ° C for 2 hours,
The humidity sensor 1 shown in FIG. 8 was manufactured. In FIG.
Reference numeral 2 denotes an alumina substrate, 3 denotes a comb-shaped electrode formed by baking Ag / Pd, and 4 denotes a ceramic for a humidity sensor formed by baking ceramic slurry.

Next, the response characteristics of the obtained humidity sensor were measured as follows. That is, the humidity sensor was placed in a tank maintained at a temperature of 30 ° C. and a relative humidity of 100%, and the change over time in the resistance value of the sensor due to the formation of dew on the sensor surface was determined. FIG. 9 shows the result. In FIG. 9, the horizontal axis represents the elapsed time immediately after the humidity sensor was placed in the tank.

As is apparent from FIG. 9, the humidity sensor of the present invention has a large resistance change in a short time as compared with the comparative example, and has a high sensitivity to humidity. . This is due to the fact that the powdery ceramic produced in the present invention is crystalline, has a microscopic pore structure as compared with the comparative example, and has a large contact area with water vapor.

[0068]

As is apparent from the above description, according to the method for producing a ceramic of the present invention, expensive equipment is not required, and high-temperature sintering is not required, as compared with a conventional method for producing a ceramic. A powdery ceramic can be obtained in a short time by a simple method. The obtained ceramic is a porous ceramic with reduced composition variation and excellent crystallinity.

Accordingly, the ceramic of the present invention is particularly suitable as a ceramic for a sensor or a catalyst. By using this ceramic, a sensor or a catalyst having excellent characteristics can be easily obtained. Furthermore, by performing molding and sintering, it can be applied to ordinary electronic ceramics and structural materials, and can be applied to a wide range of fields such as architecture, vehicles, electronic devices, and electric machines.

[Brief description of the drawings]

FIG. 1 is an X-ray diffraction chart of a lanthanum-manganese composite oxide ceramic obtained in an example of the present invention.

FIG. 2 is an X-ray diffraction chart of a lanthanum-manganese composite oxide ceramic obtained in a comparative example.

FIG. 3 is an electron micrograph of a lanthanum manganese composite oxide ceramic obtained in an example of the present invention.

FIG. 4 is an electron micrograph of a lanthanum manganese composite oxide ceramic obtained in a comparative example.

FIG. 5 is a characteristic diagram comparing the catalytic activity of a lanthanum manganese composite oxide ceramic obtained in Examples and Comparative Examples of the present invention for CO oxidation reaction.

FIG. 6 is an electron micrograph of a lanthanum manganese strontium composite oxide ceramic obtained in an example of the present invention.

FIG. 7 is an electron micrograph of a lanthanum manganese strontium composite oxide ceramic obtained in a comparative example.

FIG. 8 is a perspective view showing an example of a humidity sensor.

FIG. 9 is a characteristic diagram comparing sensitivity of a lanthanum manganese strontium composite oxide ceramic obtained as an example of the present invention and a comparative example as a humidity sensor.

[Explanation of symbols]

 1 Humidity sensor 2 Alumina substrate 3 Comb electrode 4 Ceramic

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Claims (12)

[Claims] 1. A compound containing a metal element constituting a ceramic is dissolved in water or an acid to form an aqueous solution. A complex forming agent, an alcohol having two or more hydroxyl groups, and an oxidizing agent are added to the aqueous solution. A method for producing a ceramic, characterized in that after heating to obtain an organometallic compound, the organometallic compound is further heated, burned and sintered. 2. The compound containing a metal element includes a rare earth element (provided that the element has an atomic number of 39 and 57 to 71),
Transition element (however, an element having an atomic number of 23 to 28) and alkaline earth element (however, an atomic number of 12, 20, 38)
And 56 elements), oxides or salts of at least one element selected from the group consisting of:
A method for producing a ceramic according to claim 1. 3. The method according to claim 1, wherein the complexing agent is citric acid, the alcohol having two or more hydroxyl groups is 1,2-dihydroxyethane, and the oxidizing agent is nitric acid. 3. The method for producing a ceramic according to item 1. 4. A solution obtained by adding a complex forming agent, an alcohol having two or more hydroxyl groups, and an oxidizing agent to an aqueous solution of a compound containing a metal element constituting a ceramic, and heating the solution. Yes, ceramic. 5. The compound containing a metal element includes a rare earth element (provided that the element has an atomic number of 39 and 57 to 71),
Transition element (however, an element having an atomic number of 23 to 28) and alkaline earth element (however, an atomic number of 12, 20, 38)
And 56 elements), oxides or salts of at least one element selected from the group consisting of:
The ceramic according to claim 4. 6. The method according to claim 4, wherein the complexing agent is citric acid, the alcohol having two or more hydroxyl groups is 1,2-dihydroxyethane, and the oxidizing agent is nitric acid. The ceramic according to claim 1. 7. The sensor according to claim 4, wherein the ceramic is porous and ceramic for a sensor.
7. The ceramic according to any one of 6. 8. The compound containing a metal element may be at least a rare earth element (provided that atomic numbers 39 and 57 to 71
At least one of the above), transition elements (provided that
At least one element of atomic numbers 23 to 28) and alkaline earth elements (provided that atomic numbers 12, 20,
The ceramic according to claim 7, wherein the ceramic comprises at least one of 38 and 56). 9. A sensor comprising a pair of electrodes and a sensor material disposed between the electrodes, wherein the sensor material is the ceramic according to claim 7 or 8. 10. The ceramic according to claim 4, wherein the ceramic is porous and is a catalyst ceramic.
The ceramic according to any one of the above. 11. The compound containing a metal element may be at least a rare earth element (provided that atomic numbers 39 and 57 to 7
11. The ceramic according to claim 10, wherein the ceramic includes at least one element selected from the group consisting of at least one element selected from the group consisting of at least one element selected from the group consisting of at least one element selected from atomic numbers 23 to 28. 12. A catalyst, wherein the ceramic according to claim 10 or 11 is used as a catalyst material.