JP2015006961A - Method of producing calcium-containing complex oxide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of producing a calcium-containing complex oxide which is a single phase and has a homogeneous composition.SOLUTION: The method includes a step of mixing a calcium-containing compound, a transition metal element-containing compound, at least one selected from the group consisting of citric acid, maleic acid, formic acid, acetic acid, lactic acid and malic acid, and a solvent to prepare a solution or slurry, a spray drying step of applying a spray drying process to the obtained solution or slurry, and a burning step of burning a dry powder obtained by the spray drying process.

Description

  The present invention relates to a novel method for producing a complex oxide containing calcium and a transition metal element which has a single phase and a highly homogeneous composition.

Complex oxides containing calcium are widely developed as functional materials in the fields of fuel cells, superconductivity, thermoelectricity, catalysts, and the like.
For example, Ce _1-x Ca _x O _{2-δ, which} is a solid solution of calcia and ceria, is used as a solid electrolyte of a solid oxide fuel cell. Ca _1-x Bi _x MnO _{3 in} which part of Ca in CaMnO _{3 having} a perovskite structure is substituted with Bi element is used as an n-type thermoelectric conversion material, and Ca ₃ Co ₄ O ₉ is used as a p-type thermoelectric conversion material. Has been. Ca ₂ Fe ₂ O ₅ is useful as an active component of an oxidation catalyst or an exhaust gas purification catalyst, particularly a motorcycle exhaust gas purification catalyst or a combustion exhaust gas purification catalyst.

In Patent Document 1, SrCO ₃ , CaCO ₃ , M1 ₂ O ₃ (where M1 = Sm, Gd, Dy) and Mn ₂ O ₃ which are starting materials are blended so as to have a predetermined composition and mixed by a ball mill. The mixed powder was calcined at 1300 ° C. in the air for 5 hours, and then the obtained calcined powder was crushed and then molded at 50 MPa in the air at 1550 ° C. for 5 hours. It is described that single-phase (Ca _x Sr _1-xy M1 _y ) MnO ₃ was obtained by sintering.
However, this is considered to be that single-phase (Ca _x Sr _1-xy M1 _y ) MnO ₃ was obtained as a result of improving the adhesion between the calcined powders by forming the calcined powder into a compact. It is difficult to industrialize this method.

Patent Document 2 discloses a method for synthesizing a Bi (Pb) -Sr-Ca-Cu-O-based superconductor, in which a raw metal compound is partially reacted with citric acid to produce a partial citrate salt. The method of synthesizing the composite oxide by the slurry method characterized by firing is described. FIG. 2 and FIG. 2 show the Bi (Pb) -Sr— synthesized by the synthesis method of Example 1. The line analysis results for Bi element, Pb element, Sr element, Ca element and Cu element by EPMA of Ca—Cu—O based superconductor are listed. According to this, the variation in Ca element concentration is larger than the variation in each of Bi element, Pb element, Sr element, and Cu element, and it can be seen that the uniformity of Ca element is relatively poor. This is probably because calcium citrate produced by the reaction of calcium carbonate and citric acid is a poorly soluble salt in water.
Patent Document 3 describes a method for producing Ca ₂ Fe ₂ O _{5 by} a solid phase method and its catalytic activity.

Patent Document 1 JP 2003-142742 A Patent Document 2 JP 03-257004 A Patent Document 3 JP 2005-296880 A

As described above, the conventional calcium-containing composite oxide prepared by the solid phase method or the slurry method has a problem that the above-mentioned calcium-containing compound and the transition metal element-containing compound are not easily homogeneous in principle. Have.
Thus, an object of the present invention is a group consisting of citric acid, maleic acid, formic acid, acetic acid, lactic acid and malic acid, of a complex oxide containing calcium and a transition metal element having a single phase and a homogeneous composition. An object of the present invention is to provide a production method using at least one selected from the group consisting of a solvent and a solvent.

  The present inventor has diligently studied to achieve the above object, and as a result, a solution of a specific organic acid was used, and the above calcium-containing compound was reacted with the organic acid in the liquid to be almost completely dissolved as a complex compound. The inventors have found that a novel fine particle powder having a homogeneous composition can be obtained even at a micro level, which has not existed conventionally, by spray drying in the form of fine droplets, thereby completing the present invention.

The gist of the present invention is as follows.
[1] A solution or a mixture of a calcium-containing compound, a transition metal element-containing compound, citric acid, at least one selected from the group consisting of maleic acid, formic acid, acetic acid, lactic acid and malic acid, and a solvent. Preparing a slurry;
A method for producing a calcium-containing composite oxide, comprising: a spray drying step of spray drying the solution or slurry obtained in the step, and a firing step of firing the dried powder obtained in the step.
[2] The number of moles of organic acid used in the step of preparing the solution or slurry is 0.8 to 6 times the total number of moles of metal elements constituting the calcium-containing composite oxide [ [1] The method for producing a calcium-containing composite oxide according to [1].
[3] The above [1] or [2], wherein the molar ratio of (at least one selected from the group consisting of maleic acid, formic acid, acetic acid, lactic acid and malic acid / citric acid) is 0.1 to 90 A method for producing a calcium-containing composite oxide.
[4] The method for producing a calcium-containing composite oxide according to any one of [1] to [3], wherein malic acid or maleic acid is used.
[5] The calcium-containing composite oxide has a perovskite structure, a brown millerite structure, a layered perovskite structure, a fluorite structure, or a layered structure composed of a cadmium iodide structure and a rock salt structure in a single phase. The method for producing a calcium-containing composite oxide according to any one of [1] to [4] above.
[6] Any one of [1] to [5] above, wherein the transition metal element-containing compound is a compound containing any element of Groups 7 to 9 of the periodic table or any element of a lanthanoid element. A method for producing the calcium-containing composite oxide according to claim 1.
[7] The calcium-containing material according to any one of [1] to [6], wherein the transition metal element-containing compound is an iron-containing compound, a cobalt-containing compound, a manganese-containing compound, a cerium-containing compound, or a nickel-containing compound. A method for producing a composite oxide.
[8] The method for producing a calcium-containing composite oxide according to any one of [1] to [7], wherein the solvent is water.
[9] The method for producing a calcium-containing composite oxide according to any one of the above [1] to [8], wherein the calcium-containing compound is one or more selected from the group consisting of calcium carbonate and calcium bicarbonate.
[10] The method for producing a calcium-containing composite oxide according to any one of [1] to [9] above, wherein a temperature for preparing the solution or slurry in the step of preparing the solution or slurry is 30 to 100 ° C. .
[11] The calcium according to any one of the above [1] to [10], wherein the baking temperature in the main baking step is 550 to 1300 ° C. when the baking step includes a rough baking step and a main baking step. A method for producing a composite oxide.
[12] Any of the above [1] to [11], wherein the calcium-containing composite oxide is represented by any one of the following formulas (1), (2), (3), or (4): 2. A method for producing a calcium-containing composite oxide according to item 1.
Ce _1-x Ca _x O _2-δ (1)
(0 <x ≦ 0.5, 0 <δ ≦ 0.25)
Ca _1-x Bi _x MnO ₃ (2)
(0 ≦ x ≦ 0.2)
Ca ₂ M ¹ ₂ O ₅ (3)
(M ¹ is Fe, Co, or Ni.)
Ca ₃ M ² ₄ O ₉ (4)
(M ² is Fe, Co, or Ni.)

  According to the production method of the present invention, it is possible to obtain a composite oxide containing calcium and a transition metal element which is a single phase and has a highly homogeneous composition. In the calcium-containing composite oxide produced by the production method of the present invention, the elements constituting the composite oxide are homogeneously distributed in the particles, so that the original function of the composite oxide is sufficiently exhibited. It is expected.

It is a schematic diagram of a brown millelite type crystal structure. _{2 is} an X-ray diffraction pattern diagram of Ca _0.9 Bi _0.1 MnO ₃ produced in Example 1. FIG. 4 is an SEM photograph of Ca ₂ Fe ₂ O ₅ produced in Example 2 at a magnification of 3000 times. FIG. Is Ca mapping diagram by EDX of _Ca 2 _Fe 2 _{O 5} produced in Example 2. Is Fe mapping diagram by EDX of _Ca 2 _Fe 2 _{O 5} produced in Example 2. 4 is a SEM photograph of Ca ₂ Fe ₂ O ₅ produced in Comparative Example 2 with a magnification of 3000 times. FIG. Is Ca mapping diagram by EDX of _Ca 2 _Fe 2 _{O 5} prepared in Comparative Example 2. Is Fe mapping diagram by EDX of _Ca 2 _Fe 2 _{O 5} prepared in Comparative Example 2.

  The production method of the present invention preferably includes the step of preparing the solution or slurry, the spray drying step, and the firing step in this order.

<Step of preparing a solution or slurry>
The following calcium-containing compound and transition metal element-containing compound are used as the raw material compound of the production method of the present invention. Examples of the calcium-containing compound include calcium-containing oxides, hydroxides, nitrates, carbonates, hydrogencarbonates, acetates, and alkoxides.
Examples of the transition metal element-containing compound include oxides, hydroxides, nitrates, carbonates, bicarbonates, acetates, and alkoxides containing a transition metal element.
Here, the transition metal element is a transition metal element such as manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), lanthanum (La), cerium (Ce), gadolinium (Gd), One or more elements selected from lanthanoid elements such as samarium (Sm) and bismuth (Bi).

Especially, the case where a transition metal element contains cobalt (Co), ie, the case where a transition metal element containing compound contains a cobalt containing compound, is preferable. Further, it is also preferable when the transition metal element contains manganese (Mn), that is, when the transition metal element-containing compound contains a manganese-containing compound. Furthermore, it is also preferable when the transition metal element contains iron (Fe), that is, when the transition metal element-containing compound contains an iron-containing compound.
When the transition metal element-containing compound contains a cobalt-containing compound, when it contains an iron-containing compound, or when it contains a manganese-containing compound, calcium in the calcium-containing composite oxide produced by the production method of the present invention, This is because the homogeneity of transition metal elements such as cobalt, manganese and iron is high.

  The raw material compound such as a calcium-containing compound and a transition metal element-containing compound is one or more compounds selected from oxides, hydroxides, nitrates, carbonates, bicarbonates, acetates or alkoxides per element. Can be selected as the element source. Among the raw material compounds, transition metal element-containing compounds are preferably carbonates, hydroxides or oxides from the viewpoint of environmental aspects and availability, and citrates and the like because the raw material has high reactivity. The organic acid salt is also preferred. On the other hand, among the raw material compounds, the calcium-containing compound is preferably selected as an element source from any one or more compounds selected from the group consisting of calcium carbonate and calcium bicarbonate. In particular, calcium carbonate and calcium hydrogen carbonate are preferable because they are highly reactive with organic acids and produce soluble organic acid salts.

  In the step of preparing the solution or slurry in the present invention, a solution or slurry is prepared using a solvent. The solvent is not particularly limited as long as it can dissolve or disperse the above raw material compound, but from the viewpoint of safety, solubility, nonflammability and cost, a solvent mainly composed of water is preferable, and only water is used as the solvent. More preferably. As the cosolvent, alcohols, ketones, glycols and the like can be used. The content of the solvent in the solution or slurry is preferably 30 to 90% by mass, more preferably 40 to 80% by mass.

The above raw material compounds are weighed so that calcium and the transition metal element have the desired composition.
On the other hand, an aqueous solution of an organic acid is prepared in advance. As the organic acid, it is preferable to use citric acid in combination with at least one selected from the group consisting of maleic acid, formic acid, acetic acid, lactic acid and malic acid. Citric acid and maleic acid, from lactic acid or malic acid More preferred is at least one combination selected from the group consisting of Among these, a combination of citric acid and malic acid or a combination of citric acid and maleic acid is particularly preferable.

This is because citric acid and an organic acid other than the above citric acid can be used together so that the dissolution reaction (complex formation) can proceed more easily. In particular, as the organic acid other than citric acid, maleic acid, lactic acid The effect is remarkable when at least one selected from the group consisting of malic acid is used in combination. When citric acid and malic acid, or citric acid and maleic acid are used in combination, in addition to the effect of facilitating the dissolution reaction as described above, a solution or slurry in which the calcium-containing compound constituting the composite oxide is dissolved There is also an effect of stabilizing. That is, when citric acid is used alone, the dispersion liquid in which the calcium-containing compound is dispersed gradually forms a hardly soluble precipitate after the addition of citric acid, and solidifies, but citric acid and malic acid, or When citric acid and maleic acid are used in combination, it is stable in a solution or slurry state.
As citric acid, any of anhydrous citric acid, citric acid monohydrate, and a mixture of anhydrous citric acid and citric acid monohydrate can be used.

  The total amount of citric acid used in the present invention and at least one selected from the group consisting of maleic acid, formic acid, acetic acid, lactic acid and malic acid forms a complex with the transition metal element constituting the composite oxide And it is preferable that it is more than the quantity which can fully melt | dissolve this. Specifically, the total amount of citric acid and at least one selected from the group consisting of maleic acid, formic acid, acetic acid, lactic acid and malic acid is the total number of moles of transition metal elements constituting the composite oxide The amount is preferably 0.8 to 6 times, and more preferably 0.5 to 1.1 times. If the amount is 0.8 times or more, it is preferable because the calcium-containing compound can be almost completely dissolved. If the amount is 6 times or less, the use cost of the organic acid can be reduced, and the amount of carbon dioxide generated during firing is small. This is preferable because an excessive decrease in the oxygen concentration accompanying the firing of the organic acid during firing can be suppressed.

Molar ratio of citric acid to at least one selected from the group consisting of maleic acid, formic acid, acetic acid, lactic acid and malic acid, ie (at least selected from the group consisting of maleic acid, formic acid, acetic acid, lactic acid and malic acid) The number of moles of one kind / (number of moles of citric acid) is preferably 0.1 to 90. This is because when the molar ratio is 0.1 to 90, the calcium-containing compound does not form a hardly soluble salt.
Among these, (at least one mole number selected from the group consisting of maleic acid, formic acid, acetic acid, lactic acid and malic acid) / (number of moles of citric acid) is more preferably 0.5-15. This is because when the molar ratio is 0.5 to 15, the calcium-containing compound exists stably in water.

  The calcium-containing compound constituting the composite oxide is dissolved into the solution using the above-described aqueous solution of organic acid. Other transition metal element-containing compounds constituting the composite oxide may or may not be dissolved in an aqueous solution of an organic acid. The apparatus for carrying out this dissolution reaction is not particularly limited. For example, the apparatus comprises a stirring means, a heating means, a raw material compound supply means, and an organic acid aqueous solution supply means, without causing the supplied raw material compound to precipitate. A tank-type reaction vessel that can be suspended and reacted with an organic acid in a suspended state is preferred. As the stirring means, any of ordinary stirrers such as a vertical stirrer, a propeller stirrer, a turbine stirrer and the like is preferably used. In the case of a small-scale reaction, a stirrer or a rotor may be installed in the flask type container.

  The contact method of each raw material compound of calcium-containing compound and other transition metal element-containing compound and the organic acid aqueous solution is not particularly limited, but the dissolution reaction is grasped as a solid-liquid heterophasic reaction in chemical engineering. The reaction is not particularly limited as long as the reaction is efficiently performed and a solution or slurry in which the calcium-containing compound is finally dissolved is obtained.

Usually, a method in which an organic acid aqueous solution is first charged in a reaction vessel and a raw material compound is added to the reaction vessel while stirring to react is preferable.
Alternatively, the slurry containing a part of the raw material compound and a part of the organic acid may be reacted first, then the remaining raw material compound may be added, and then the remaining organic acid may be added and reacted.
Raw material compounds such as calcium-containing compounds and transition metal element-containing compounds to be added may be added sequentially for each raw material compound, or the raw material compounds are mixed in advance and the mixed raw material compounds are supplied simultaneously. And may be reacted. Further, these supply methods may be combined.

The temperature at which the solution or slurry is prepared is preferable because the dissolution reaction of the calcium-containing compound is promoted by carrying out the heating under a certain degree of heating. The temperature for preparing the solution or slurry is preferably 30 to 100 ° C, more preferably 30 to 80 ° C, and particularly preferably 50 to 80 ° C. The reaction time may vary depending on the reaction temperature, organic acid concentration, type of organic acid or raw material compound, particle size, etc., but is usually 10 minutes to 10 hours, preferably 30 minutes to 5 hours, more preferably 1 to 1. About 3 hours.
In the production method of the present invention, the total content of metal elements composed of calcium and transition metal elements in the prepared solution or slurry is preferably 5 to 40% by mass, and more preferably 5 to 20% by mass.

<Spray drying process>
In the present invention, the solution or slurry in which the calcium-containing compound is dissolved is preferably dried using a spray dryer. Spray drying may be either hot spray drying or freeze spray drying. In the thermal spray drying, a solution or slurry in which the calcium-containing compound is almost completely dissolved in the organic acid aqueous solution is supplied to a drying apparatus such as a hot air dryer or a thermal spray dryer to perform drying. The solution supplied to the drying device becomes fine droplets in the device, which forms a fluidized bed with hot air for drying, and is dried in a very short time while being transported by the hot air to obtain a dry powder. As a result, it is considered that the homogeneity of calcium in the obtained dry powder becomes high.

  As a sprayer in the case of using a thermal spray dryer, one having a rotating disk, a two-fluid nozzle, a pressure nozzle, etc. can be appropriately employed. The hot air temperature for drying is 150 to 300 ° C. at the inlet and at the outlet. It is preferable that the temperature is about 100 to 150 ° C.

  Freeze spray drying is a method in which a solution or slurry in which the above calcium-containing compound is dissolved is frozen and dried under reduced pressure in a frozen state. When the solution or slurry in which the above calcium-containing compound is dissolved is sprayed into a cooling medium with a known spraying machine such as a spray, it freezes instantaneously and becomes frozen. The form of the nozzle of the sprayer is not particularly limited, and may be, for example, a 1 fluid nozzle or a 2 fluid nozzle. A cooling medium is not specifically limited, For example, liquid nitrogen, dry ice methanol, etc. can be used. By instantly freezing a solution or slurry in which a calcium-containing compound is dissolved, a large number of fine ice particles are generated in the frozen product. The ice sublimates and becomes a lyophilized product. The pressure during decompression is preferably 25 Pa or less. This is because if the pressure is 25 Pa or less, the ice particles in the frozen material are easily sublimated.

  According to such thermal spray drying and freeze spray drying, a solution or slurry in which a calcium-containing compound is dissolved by forming a homogeneous phase forms a minute droplet state, and each droplet is instantaneously or in a very short time. The dry powder (mixed powder) in which a solid phase having a homogeneous composition to a micro level is deposited is obtained by evaporating and removing moisture or sublimating and removing frozen ice.

<Baking process>
The spray-dried mixed powder is preferably transferred to a firing container and fired in a firing furnace. It is preferable that the firing step basically includes two firing steps having different firing temperatures for rough firing and main firing. However, preliminary firing may be further performed between rough firing and main firing, and the temperatures are sequentially increased. It may be a process consisting of only the main firing that is raised, that is, only one firing process. The material of the firing container is not particularly limited, and examples thereof include mullite and cordierite.
The firing furnace may be an electric or gas type shuttle kiln as a heat source, or may be a roller hearth kiln or a rotary kiln, and is not particularly limited.

(Rough firing process)
In the rough firing step, an operation is performed in which the temperature of the firing furnace is increased to a target firing temperature, preferably 300 to 600 ° C., preferably at a rate of temperature increase of 20 to 200 ° C./hour. It is preferable to set the heating rate to 20 ° C./hour or more because the time to reach the target firing temperature is shortened and the productivity is improved.
In addition, it is preferable to set the rate of temperature increase to 200 ° C./hour or less because the chemical change of the reactants at each temperature sufficiently proceeds.
300-600 degreeC is preferable and the firing temperature at the time of rough baking has more preferable 350-550 degreeC. Setting the temperature to 300 ° C. or higher is preferable because the carbon component hardly remains. Moreover, since it becomes difficult to produce an impurity phase in the product after this baking by setting it as 600 degrees C or less, it is preferable.

  The firing time for the rough firing is preferably 4 to 24 hours, and more preferably 8 to 20 hours. By setting it as 4 hours or more, since a carbon component becomes difficult to remain, it is preferable. Moreover, even if it exceeds 24 hours, there is no change in the product, but the productivity decreases, so it is preferable to make it 24 hours or less. This rough calcination may be held at a constant temperature, for example, 400 ° C. for 8 hours, or may be increased from 300 ° C. to 400 ° C. at a rate of 20 ° C./hour.

  The atmosphere of the firing furnace at the time of rough firing is an oxygen-containing atmosphere, and is preferably in the air (in the air) or in an atmosphere having an oxygen concentration of 21% by volume or less. When the oxygen concentration exceeds 21% by volume, the carbon component in the raw material mixed powder burns, and as a result of partial oxidation reaction, the constituent elements of the product may be localized. It is preferable to make it.

  After roughly firing, the temperature is lowered to room temperature. The temperature lowering rate is preferably 40 to 200 ° C./hour. It is preferable that the temperature drop rate is 40 ° C./hour or more because productivity is improved. Further, it is preferable to set the temperature lowering rate to 200 ° C./hour or less because the possibility that the firing container to be used is broken due to thermal shock is reduced.

  Next, the oxide obtained in the rough firing step is crushed as necessary. Crushing is generally performed by a dry method using a pulverizer such as a cutter mill, a jet mill, or an atomizer. In addition, when not changing a baking container and not crushing, you may transfer to the following temporary baking process or the main baking process, without lowering temperature from a rough baking process.

(Preliminary firing process)
The coarsely fired powder fired in the coarse firing step is temporarily fired as necessary. In the pre-baking step, the temperature of the baking furnace is raised to the target pre-baking temperature at a temperature rising rate of 50 to 800 ° C./hour, preferably 50 to 400 ° C./hour. It is preferable to set the heating rate to 50 ° C./hour or more because the time to reach the target firing temperature is shortened and the productivity is improved. Further, it is preferable that the rate of temperature increase is 800 ° C./hour or less because the chemical change of the reactant at each temperature is sufficiently advanced.

500-800 degreeC is preferable and the temperature of temporary baking is more preferable 500-700 degreeC. A temperature of 500 ° C. or higher is preferable because no carbon component remains. Moreover, since it becomes difficult to sinter a sintered powder excessively when it is 800 degrees C or less, it is preferable.
The firing time is preferably 4 to 24 hours, and more preferably 8 to 20 hours. If it is 4 hours or longer, the carbon component hardly remains, which is preferable. Moreover, it is preferable that it is 24 hours or less because the product is not changed and the productivity is improved.

The atmosphere of the firing furnace at the time of temporary firing is preferably an oxygen-containing atmosphere similar to that during rough firing. After pre-baking for a predetermined time, the temperature is lowered to room temperature. The temperature lowering rate is preferably 40 to 200 ° C./hour. It is preferable that the temperature is 40 ° C./hour or more because productivity does not decrease. Moreover, since the possibility that the baking container to be used will break due to a thermal shock is reduced at 200 ° C./hour or less, it is preferable.
Next, the oxide obtained by calcination is crushed as necessary in the same manner as performed after the coarse calcination. Crushing is generally performed by a dry method using a pulverizer such as a cutter mill, a jet mill, or an atomizer.

(Main firing process)
The coarsely fired powder or the pre-fired powder is fired by the main firing process. The firing step of the present invention may be only one final firing step without performing the rough firing step and the preliminary firing step. In the main baking step, it is preferable to raise the temperature of the baking furnace to the target baking temperature at a temperature rising rate of 50 to 800 ° C./hour, preferably 50 to 400 ° C./hour. A temperature increase rate of 50 ° C./hour or more is preferable because the time to reach the target firing temperature is shortened and productivity is improved.
Further, when the rate of temperature rise is 800 ° C./hour or less, the chemical change of the reactant at each temperature does not proceed sufficiently, and the reactant does not reach the target firing temperature in a heterogeneous state. Therefore, it is preferable because no by-product is generated in the fired product.

The firing temperature in the main firing step is preferably 550 to 1300 ° C, and more preferably 750 to 1250 ° C. It is preferable that the temperature is 550 ° C. or higher and 1300 ° C. or lower because a target crystal phase is effectively generated.
The firing time is preferably 4 to 24 hours, and more preferably 5 to 20 hours. It is preferable that the reaction time is 4 hours or longer because a product having a single crystal phase can be obtained without mixing unreacted substances in the target oxide. Moreover, when it is 24 hours or less, there is no change in the product and productivity is not lowered, which is preferable.

The firing furnace atmosphere during the main firing is preferably an oxygen-containing atmosphere similar to that during rough firing or temporary firing. After performing the main firing, the temperature is lowered to room temperature. The temperature lowering rate is preferably 40 to 200 ° C./hour. It is preferable that the temperature is 40 ° C./hour or more because productivity does not decrease. Moreover, since the possibility that the baking container used by making it 200 degrees C / hr or less will be cracked by a thermal shock falls, it is preferable.
A baking process consists of a rough baking process and a main baking process, and the case where the baking temperature of a main baking process is 550-1300 degreeC is preferable, and 700-1300 degreeC is especially preferable. When the firing step includes a rough firing step and a main firing step, and the firing temperature in the main firing step is 550 to 1300 ° C., a composite oxide having a single crystal phase of interest and high homogeneity of constituent elements is obtained. Because.

Next, the oxide obtained by the main firing is crushed in the same manner as performed after the rough firing. Crushing is generally performed by a dry method using a pulverizer such as a cutter mill, a jet mill, or an atomizer. The volume average particle size of the powder after pulverization is preferably 1 to 50 μm. More preferably, it is 1-20 micrometers.
Thereafter, it may be further pulverized in a wet manner to adjust the particle size as necessary. In addition, you may continue this baking without lowering to room temperature after completion | finish of said rough baking. That is, two steps of rough firing and main firing may be performed continuously.

The composition of the calcium-containing composite oxide produced by the production method according to the present invention is not particularly limited. Examples thereof include CaMnO ₃ , CaCoO ₃ , CaFeO ₃ , Ca ₂ MnO ₄ , Ca ₂ Fe ₂ O ₅ , Ce _0.8 Ca _0.2 O _{2 -δ} , and Ca ₃ Co ₄ O ₉ . Further, it may be a compound obtained by substituting a part of Ca or a part of the transition metal element of the above compound with another element (hereinafter also referred to as a substitute), and the oxygen atom constituting the composite oxide is It may be present in excess or deficient.

The composition of the calcium-containing composite oxide is preferably Ca ₃ Co ₄ O ₉ , which is a calcium-containing composite oxide in which the transition metal element contains cobalt, or a substituted product thereof. In addition, CaMnO ₃ which is a calcium-containing composite oxide containing manganese as a transition metal element or a substituted product thereof is also preferable. This is because when the transition metal element is cobalt or manganese, the calcium in the calcium-containing composite oxide produced by the production method of the present invention and the transition metal element such as cobalt or manganese are highly homogeneous. is there.
The calcium-containing composite oxide obtained by the production method according to the present invention preferably has a composition represented by any of the following formulas (1), (2), (3), or (4). .
Ce _1-x Ca _x O _2-δ (1)
(It is preferable that 0 <x ≦ 0.5 and 0 <δ ≦ 0.25, and more preferably 0.1 ≦ x ≦ 0.3 and 0.005 ≦ δ ≦ 0.15.)
Ca _1-x Bi _x MnO ₃ (2)
(0 ≦ x ≦ 0.2 is preferable, and 0.1 ≦ x ≦ 0.15 is more preferable.)
Ca ₂ M ¹ ₂ O ₅ (3)
(M ¹ is Fe, Co, or Ni.)
Ca ₃ M ² ₄ O ₉ (4)
(M ² is Fe, Co, or Ni.)

  The crystal structure of the calcium-containing composite oxide produced by the production method according to the present invention is not particularly limited. Among these, the perovskite structure, the brown millerite structure, the layered perovskite structure, the fluorite structure, or the cadmium iodide type What has the layer structure which consists of a structure and a rock salt type structure in a single phase is preferable.

Here, whether or not the calcium-containing composite oxide has a single-phase crystal structure is determined by analyzing the crystal phase of the calcium-containing composite oxide powder by X-ray diffraction measurement. It can be determined by whether or not the diffraction peak based on the diffraction peak can be detected together with the diffraction peak based on the target crystal phase.
The layered perovskite structure is a layered structure in which layers composed of a perovskite structure represented by the composition formula A ₂ BO ₄ and ABO ₃ and layers composed of a rock salt structure represented by AO are alternately laminated. That means.

The brown millerite structure is compositionally represented by ABO _{2.5 in} which the oxygen site of ABO ₃ is partially lost. As shown in FIG. 1, metal ion B exists at the center and oxygen is present at each vertex. Metal ions A are present in some of the interlocutors composed of a distorted octahedron in which ions are present and a distorted tetrahedron in which metal ions B are present in the center and oxygen ions are present at each vertex. The crystal structure characterized by The reason why the above crystal structure is preferable is that when a calcium-containing composite oxide is produced by the production method of the present invention, it is easy to obtain a calcium-containing composite oxide having a single phase, that is, a single crystal phase.

  Examples of the present invention (Examples 1 to 4) will be described below in comparison with comparative examples (Comparative Examples 1 to 3). However, these examples are examples of embodiments of the present invention, and the present invention is not construed as being limited to these examples. Hereinafter, “%” means “mass (or weight)%” unless otherwise specified.

[Example 1]
(1) Each raw material was weighed so as to form Ca _0.9 Bi _0.1 MnO ₃ .
That is, 17.73 g of calcium carbonate (CaCO ₃ ) (Ca content 39.98%) as a Ca source and 4.59 g of bismuth oxide (Bi ₂ O ₃ ) (Bi content 89.49%) as a Bi source , 24.19 g of manganese carbonate (MnCO ₃ ) (Mn content: 44.62%) as an Mn source (measured so that Ca: Bi: Mn is 0.9: 0.1: 1 by atomic ratio) did.
Next, 150 mL of pure water was added to a 500 mL beaker, and weighed bismuth oxide was added and dispersed at room temperature while stirring with a magnetic stirrer.

(2) To the bismuth oxide slurry prepared in (1) above, 4.13 g of citric acid monohydrate with an equivalent mole of Bi contained in bismuth oxide was added and reacted at room temperature for 10 hours. I let you.
(3) Weighed calcium carbonate and manganese carbonate were added to the slurry prepared in (2) above and dispersed at room temperature with stirring.
(4) With respect to 16.69 g of malic acid and the number of moles of Ca and Mn contained in the raw material compound, respectively, as a total of 1/3 times the mole of Ca and Mn contained in the raw material compound 45.42 g of citric acid monohydrate was added as a total of 2/3 times and 1/2 times moles respectively, heated to 50 ° C., and reacted at that temperature for 2 hours to obtain a slurry.
The total number of moles of Ca, Bi and Mn, which are metal elements contained in the mixture of raw material compounds, is 0.393 mol, and malic acid (0.124 mol) and citric acid (0.236) used for dissolving the raw material compounds. Mol) was 0.360 mol. That is, (total number of moles of organic acid) / (total number of moles of metal elements) was 0.92, and (number of moles of malic acid) / (number of moles of citric acid) was 0.53. It was.

(5) After completion of the reaction, the resulting slurry was sprayed into liquid nitrogen with a spray bottle and dried with a freeze dryer to obtain a dry powder of a complex organic acid salt as an intermediate product. In addition, as a freeze dryer, the DRC-1100 type | mold square dry chamber and FDU-2100 type freeze dryer by EYELA are used, Drying start temperature: -30 degreeC, Drying end temperature: 25 degreeC, Operation time: Drying was performed under conditions of 18 hours.

  Separately, a slurry using water in which calcium carbonate is dispersed as a medium is prepared, and when the mixture of citric acid monohydrate and malic acid is added thereto, the calcium carbonate remains in a slurry state even after being left overnight. It was confirmed that it existed stably. However, when only citric acid was used instead of the mixture of citric acid and malic acid, a hardly soluble precipitate was formed and solidified immediately after the addition of citric acid.

(6) (Coarse firing, main firing)
The dry powder obtained in (5) was baked at 400 ° C. for 10 hours in the air in an electric furnace to decompose the remaining carbon (coarse calcination). The temperature increase rate from room temperature to 400 ° C. was 133 ° C./hour, and the temperature decrease rate from 400 ° C. to room temperature was 100 ° C./hour.

The obtained coarsely fired powder was fired at 850 ° C. for 6 hours in the air in an electric furnace to obtain the target Ca _0.9 Bi _0.1 MnO ₃ powder (main firing). The temperature increase rate from room temperature to 700 ° C. was 175 ° C./hour, the temperature increase time to 850 ° C. was 100 ° C./hour, and the temperature decrease rate from 850 ° C. to room temperature was 100 ° C./hour. 4 g of the obtained fired powder was crushed in a mortar to obtain a crushed powder.

(7) (Component analysis)
(Particle size distribution measurement)
A sample was prepared by dispersing a small amount of sample in ion-exchanged water as follows. As a dispersing agent, an aqueous solution having a concentration of 0.24% by weight using sodium diphosphate decahydrate manufactured by Wako Pure Chemical Industries, Ltd. is used, so that the total amount becomes 10 ml from about 0.001 g of the sample and the dispersion. A dispersion was prepared. Immediately before the measurement, ultrasonic treatment with an output of 30 W was performed for 180 seconds.
As a result, the volume average particle size (D50) of the obtained crushed powder was 11.5 μm.

(X-ray diffraction measurement)
The crystal phase of the pulverized powder was analyzed by X-ray diffraction measurement.
The X-ray diffractometer used was RINT2200V manufactured by Rigaku Corporation. The measurement conditions were a CuKα ray as a radiation source, a tube voltage of 40 kV, a tube current of 40 mA, and a scan speed of 2 ° / min.
FIG. 2 shows the measured X-ray diffraction pattern. It can be seen from FIG. 2 that Ca _0.9 Bi _0.1 MnO _{3 produced} has a single-phase perovskite structure.

[Example 2]
(1) Each raw material was weighed so as to form Ca ₂ Fe ₂ O ₅ .
That is, 22.13 g of calcium carbonate (CaCO ₃ ) (Ca content 39.98%) as a Ca source and an iron citrate aqueous solution (Fe (C ₆ H ₅ O ₇ ) aq) (Fe content 8. 01.3%, citric acid content 46.31%) 153.88 g (at an atomic ratio such that Ca: Fe is 1: 1) was weighed.
Next, 130 mL of pure water was added to a 500 mL beaker equipped with a temperature controller and a stirrer, and weighed calcium carbonate was added and dispersed at room temperature with stirring.
(2) The amount of malic acid used was added as 0.073 mol of 1/3 times the mol of Ca contained in the raw material compound, and then the above iron citrate aqueous solution was added and heated to 50 ° C., The mixture was reacted at that temperature for 2 hours to obtain a slurry.
The amount of citric acid monohydrate used is usually 0.368 mol as a total of 2/3 times the same number of moles of Ca atom and Fe atom contained in the raw material compound, respectively. However, since the content of citrate ions in the weighed 153.88 g of the iron citrate aqueous solution was an excess of 0.377 mol, citric acid monohydrate was not added.

The total number of moles of Ca and Fe, which are metal elements contained in the mixture of raw material compounds, is 0.440 moles, and malic acid (0.074 moles) and citrate ions (0.377 moles) used to dissolve the raw material compounds. ) In total was 0.451 mol. That is, (total number of moles of organic acid) / (total number of moles of metal elements) was 1.0, and (number of moles of malic acid) / (number of moles of citric acid) was 0.2. It was.
After completion of the reaction, the resulting slurry was dried with a freeze dryer under the same conditions as in Example 1 to obtain a dry powder of a complex organic acid salt as an intermediate product.

(3) (Coarse firing, main firing)
The obtained dry powder was baked in the electric furnace at 400 ° C. for 10 hours in the air to decompose the remaining carbon (coarse calcination). The temperature increase rate from room temperature to 400 ° C. and the temperature decrease rate from 400 ° C. to room temperature were the same as in Example 1.

The obtained coarsely fired powder was fired at 1100 ° C. for 6 hours in the air in an electric furnace to obtain the target Ca ₂ Fe ₂ O ₅ powder (main firing). The temperature increase rate from room temperature to 700 ° C is 175 ° C / hour, the temperature increase rate from 700 to 1000 ° C is 100 ° C / hour, and the temperature increase rate to 1100 ° C is 67 ° C / hour, from 1100 ° C to room temperature. The temperature lowering rate was set to 100 ° C./hour. The obtained fired powder was crushed in a mortar to obtain a crushed powder.

(4) (Component analysis)
(Particle size distribution measurement)
Next, as in Example 1, the particle size distribution of the obtained crushed powder was measured. As a result, the obtained ground powder had a volume average particle size (D50) of 8.3 μm.
(X-ray diffraction measurement)
The crystal phase of the crushed powder was analyzed by X-ray diffraction measurement in the same manner as in Example 1. As a result, it was found that the produced Ca ₂ Fe ₂ O ₅ has a single-phase brown millerite structure.
(SEM and EDX analysis)
The crushed powder was analyzed in the same manner as in Example 1 using a scanning electron microscope (SEM) and an energy dispersive X-ray spectrometer (EDX) attached thereto.

FIG. 3 is an SEM photograph (magnification × 3000) of the powder. 4 and 5 are mapping diagrams of Ca and Fe by EDX. From this, the Ca and Fe in _Ca 2 _Fe 2 _{O 5} prepared is homogeneously distributed in comparison with Ca and Fe in _Ca 2 _Fe 2 _{O 5} produced in the solid phase method described below Comparative Example 2 It was confirmed that

Example 3
(1) (Preparation and dispersion of raw material compounds)
Each raw material was weighed so as to form Ca _0.1 Ce _0.9 O _1.95 .
That is, 3.75 g of calcium carbonate (CaCO ₃ ) (Ca content 39.98%) as a Ca source and cerium carbonate (Ce ₂ (CO ₃ ) ₃ ) (Ce content 41.44%) as a Ce source. 75 g (at an atomic ratio such that Ca: Ce is 0.1: 0.9) was weighed.
Next, 150 mL of pure water was added to a 500 mL beaker equipped with a temperature controller and a stirrer, and weighed calcium carbonate and cerium carbonate were added and dispersed at room temperature with stirring.

(2) (Intermediate product and drying)
Included in the raw material slurry aqueous solution is 272.34 g of malic acid as a total of 1/3 times mole and 6 times mole of Ca atom and Ce atom contained in the raw material compound, respectively, and in the raw material compound. Then, 5.24 g of citric acid monohydrate having a molar ratio of 2/3 to the number of moles of Ca atoms to be added was heated to 55 ° C. and reacted at that temperature for 2 hours to obtain a slurry.
The total number of moles of Ca and Ce, which are metal elements contained in the mixture of raw material compounds, is 0.374 mol, and malic acid (2.03 mol) and citric acid (0.025 mol) used for dissolving the raw material compounds The total number of moles was 2.055 moles. That is, (total number of moles of organic acid) / (total number of moles of metal elements) was 5.5, and (number of moles of malic acid) / (number of moles of citric acid) was 81.2. It was.
After completion of the reaction, the obtained slurry was dried with a spray drier under the same conditions as in Example 1 to obtain a dry powder of a complex organic acid salt as an intermediate product.

(3) (Coarse firing, main firing)
The obtained dry powder was baked in the electric furnace at 400 ° C. for 10 hours in the air to decompose the remaining carbon (coarse calcination). The temperature increase rate from room temperature to 400 ° C. and the temperature decrease rate from 400 ° C. to room temperature were the same as in Example 1.

The obtained coarsely fired powder was fired at 600 ° C. for 6 hours in the air in an electric furnace to obtain a target Ca _0.1 Ce _0.9 O _1.95 powder (main firing). The temperature increase rate from room temperature to 600 ° C. was 150 ° C./hour, and the temperature decrease rate from 600 ° C. to room temperature was 100 ° C./hour. The obtained fired powder was crushed in a mortar to obtain a crushed powder.

(4) (Component analysis)
(Particle size distribution measurement)
Next, as in Example 1, the particle size distribution of the obtained crushed powder was measured. As a result, the volume average particle diameter (D50) of the obtained crushed powder was 6.8 μm.
(X-ray diffraction measurement)
The crystal phase of the crushed powder was analyzed by X-ray diffraction measurement in the same manner as in Example 1. As a result, it was found that the produced Ca _0.1 Ce _0.9 O _1.95 has a single-phase fluorite structure.

Example 4
A pulverized powder of Ce _0.9 Ca _0.1 O _1.95 was obtained in the same manner as in Example 3 except that 235.80 g of maleic acid was used instead of 272.34 g of malic acid.
The total number of moles of the metal elements was 0.374 mol as in Example 3, and the total number of moles of maleic acid and citric acid used was 2.055 mol. Therefore, (total number of moles of organic acid) / (total number of moles of metal elements) was 5.5, and (number of moles of maleic acid) / (number of moles of citric acid) was 81.2.
Next, as in Example 1, the particle size distribution of the obtained crushed powder was measured. As a result, the obtained ground powder had a volume average particle size (D50) of 7.2 μm.
The crystal phase of the crushed powder was analyzed by X-ray diffraction measurement in the same manner as in Example 1. As a result, it was found that the produced Ca _0.1 Ce _0.9 O _1.95 has a single-phase fluorite structure.

[Comparative Example 1]
(1) (Preparation and dispersion of raw material compounds)
Each raw material was weighed so as to form Ca _0.9 Bi _0.1 MnO ₃ .
That is, 5.91 g of calcium carbonate (CaCO ₃ ) (Ca content 39.98%) as a Ca source and 1.53 g of bismuth oxide (Bi ₂ O ₃ ) (Bi content 89.49%) as a Bi source , 8.06 g of manganese carbonate (MnCO ₃ ) (Mn content: 44.62%) as an Mn source (at an atomic ratio, Ca: Bi: Mn is 0.9: 0.1: 1) is weighed did.
(2) Mixing of raw material compounds Weighed calcium carbonate, bismuth oxide and manganese carbonate were transferred to a 0.08 L container, 100 g of zirconia balls having a diameter of 5 mm as a grinding medium and AK-225AE (Asahi Glass Co., Ltd.) as a grinding medium. Ball milling was carried out for 20 hours together with 50 mL of fluorine solvent name).
(3) (Coarse firing, main firing)
The obtained pulverized powder was roughly baked in an electric furnace in the atmosphere, and then baked. The firing conditions (baking temperature, firing time, heating rate, and cooling rate) during rough firing or main firing were the same as in Example 1. As a result, Ca _0.9 Bi _0.1 MnO ₃ was obtained as a fired powder.
The obtained fired powder was crushed in a mortar to obtain a crushed powder.
Next, as in Example 1, the particle size distribution of the obtained crushed powder was measured. As a result, the obtained crushed powder had a volume average particle size (D50) of 10.5 μm.

(4) (Component analysis)
(X-ray diffraction measurement)
The crystal phase of the crushed powder was analyzed by X-ray diffraction measurement in the same manner as in Example 1. As a result, it was confirmed that the produced Ca _0.9 Bi _0.1 MnO ₃ contained a phase corresponding to a brown millerite structure in addition to a crystal phase having a perovskite structure.

[Comparative Example 2]
(1) (Preparation of raw material compounds)
Each raw material was weighed so as to form Ca ₂ Fe ₂ O ₅ .
That is, 7.38 g of calcium carbonate (CaCO ₃ ) (Ca content 39.98%) as a Ca source and 17.21 g (atoms) of iron oxide (Fe ₂ O ₃ ) (Fe content 23.88%) as an Fe source The ratio of Ca: Fe was 1: 1).
(2) Mixing of raw material compounds Weighed calcium carbonate and iron oxide were transferred to a 0.08 L container, and ball milled for 20 hours with 100 g of zirconia balls having a diameter of 5 mm as a grinding medium and 60 mL of AK-225AE as a grinding medium.
(3) (Coarse firing, main firing)
The obtained pulverized powder was roughly baked in an electric furnace in the atmosphere, and then baked. The firing conditions (baking temperature, firing time, heating rate, and cooling rate) during the rough firing or main firing were the same as in Example 2. As a result, Ca ₂ Fe ₂ O ₅ was obtained as a fired powder. The obtained fired powder was crushed in a mortar to obtain a crushed powder.
Next, as in Example 1, the particle size distribution of the obtained crushed powder was measured. As a result, the obtained ground powder had a volume average particle size (D50) of 9.5 μm.

(4) (Component analysis)
(X-ray diffraction measurement)
The crystal phase of the crushed powder was analyzed by X-ray diffraction measurement in the same manner as in Example 1. As a result, the produced Ca ₂ Fe ₂ O ₅ contained Fe ₂ O ₃ and other impurity phases in addition to the crystal phase having a brown millerite structure.
(SEM and EDX analysis)
The pulverized powder was analyzed in the same manner as in Example 2 using a scanning electron microscope (SEM) and an energy dispersive X-ray spectrometer (EDX) attached thereto.

FIG. 6 is an SEM photograph (magnification × 3000) of the powder. 7 and 8 are mapping diagrams of Ca and Fe by EDX. In the mapping diagrams of FIG. 7 and FIG. 8, the location where Ca and Fe are segregated can be confirmed even when the unevenness of the measurement sample is taken into consideration. Therefore, Ca and Fe in _Ca 2 _Fe 2 _{O 5} produced, compared to non-homogeneously distributed Ca and Fe in _Ca 2 _Fe 2 _{O 5} produced by the method according to the present invention of Example 2 I understand that.

[Comparative Example 3]
(1) (Preparation of raw material compounds)
Each raw material was weighed so as to form Ce _0.9 Ca _0.1 O _1.95 .
That is, calcium carbonate (CaCO ₃ ) (Ca content 39.98%) 0.62 g as a Ca source, and cerium carbonate (Ce ₂ (CO ₃ ) ₃ ) (Ce content 41.44%) as a Ce source 18. 96 g (at an atomic ratio such that Ca: Ce is 0.1: 0.9) was weighed.
(2) Mixing of raw material compounds Weighed calcium carbonate and cerium carbonate were transferred to a 0.08 L container, and ball milled for 20 hours with 100 g of zirconia balls having a diameter of 5 mm as a grinding medium and 60 mL of AK-225AE as a grinding medium.
(3) (Coarse firing, main firing)
The obtained pulverized powder was roughly baked in an electric furnace in the atmosphere, and then baked. The firing conditions (baking temperature, firing time, heating rate, and cooling rate) during rough firing or main firing were the same as in Example 3. As a result, Ce _0.9 Ca _0.1 O _1.95 was obtained as a fired powder. The obtained fired powder was crushed in a mortar to obtain a crushed powder.
Next, as in Example 1, the particle size distribution of the obtained crushed powder was measured. As a result, the obtained ground powder had a volume average particle size (D50) of 8.3 μm.

(4) (Component analysis)
(X-ray diffraction measurement)
The crystal phase of the crushed powder was analyzed by X-ray diffraction measurement in the same manner as in Example 1. As a result, it was confirmed that the produced Ca _0.1 Ce _0.9 O _1.95 contained an impurity phase corresponding to CaCO ₃ in addition to the crystal phase having a fluorite structure.

  The calcium-containing composite oxide obtained by the production method of the present invention is a single phase and has a feature that the homogeneity of the constituent elements is higher than that by the conventional solid phase method or slurry method. Therefore, the function inherent to the composite oxide can be sufficiently exerted, and its industrial applicability is great.

Claims (12)

A solution or slurry is prepared by mixing a calcium-containing compound, a transition metal element-containing compound, citric acid, at least one selected from the group consisting of maleic acid, formic acid, acetic acid, lactic acid and malic acid, and a solvent. The process of
A method for producing a calcium-containing composite oxide, comprising: a spray drying step of spray drying the solution or slurry obtained in the step, and a firing step of firing the dried powder obtained in the step.   The number of moles of organic acid used in the step of preparing the solution or slurry is 0.8 to 6 times the total number of moles of metal elements constituting the calcium-containing composite oxide. A method for producing a calcium-containing composite oxide.   The calcium-containing composite oxide according to claim 1 or 2, wherein the molar ratio of (at least one selected from the group consisting of maleic acid, formic acid, acetic acid, lactic acid and malic acid / citric acid) is 0.1 to 90. Production method.   The method for producing a calcium-containing composite oxide according to any one of claims 1 to 3, wherein malic acid or maleic acid is used.   The calcium-containing composite oxide has a perovskite structure, a brown millerite structure, a layered perovskite structure, a fluorite structure, or a layered structure composed of a cadmium iodide structure and a rock salt structure in a single phase. The manufacturing method of the calcium containing complex oxide of any one of 1-4.   The calcium-containing composite according to any one of claims 1 to 5, wherein the transition metal element-containing compound is a compound containing any element of Groups 7 to 9 of the periodic table or any element of a lanthanoid element. Production method of oxide.   The method for producing a calcium-containing composite oxide according to any one of claims 1 to 6, wherein the transition metal element-containing compound is an iron-containing compound, a cobalt-containing compound, a manganese-containing compound, a cerium-containing compound, or a nickel-containing compound. .   The said solvent is water, The manufacturing method of the calcium containing complex oxide of any one of Claims 1-7.   The method for producing a calcium-containing composite oxide according to any one of claims 1 to 8, wherein the calcium-containing compound is one or more selected from the group consisting of calcium carbonate and calcium hydrogen carbonate.   The method for producing a calcium-containing composite oxide according to any one of claims 1 to 9, wherein a temperature for preparing the solution or slurry in the step of preparing the solution or slurry is 30 to 100 ° C.   When the said baking process consists of a rough baking process and a main baking process, the baking temperature in a main baking process is 550-1300 degreeC, The manufacture of the calcium containing complex oxide of any one of Claims 1-10. Method. The calcium according to any one of claims 1 to 11, wherein the calcium-containing composite oxide is represented by any of the following formula (1), formula (2), formula (3), or formula (4). A method for producing a composite oxide.
Ce _1-x Ca _x O _2-δ (1)
(0 <x ≦ 0.5, 0 <δ ≦ 0.25)
Ca _1-x Bi _x MnO ₃ (2)
(0 ≦ x ≦ 0.2)
Ca ₂ M ¹ ₂ O ₅ (3)
(M ¹ is Fe, Co, or Ni.)
Ca ₃ M ² ₄ O ₉ (4)
(M ² is Fe, Co, or Ni.)

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