JP2024036893A - Method for producing perovskite oxide, method for producing perovskite oxide precursor, method for producing fuel cell - Google Patents

Abstract

[Problem] Sintering can be performed at a low temperature that suppresses the volatilization of the barium component, and a single-phase perovskite oxide can be easily obtained. A manufacturing method is provided in which the composition of perovskite oxide contained in a solid can be precisely controlled. [Solution] A raw material aqueous solution containing rare earth element ions, barium ions, and zirconium ions is prepared, and the amount of water is 0.5 to 20 times as large as the rare earth element ions, barium ions, and zirconium ions in the raw material aqueous solution. A precipitant containing ammonium oxide and ammonium hydrogen carbonate, in which the number of moles of ammonium hydrogen carbonate is 0.08 to 0.45 mole per mole of ammonium hydroxide, is added to the raw material aqueous solution to form a mixed solution. In this method, a perovskite oxide precursor is precipitated, and the perovskite oxide precursor is fired. [Selection diagram] None

Description

The present invention relates to a method for producing a perovskite oxide, a method for producing a perovskite oxide precursor, and a method for producing a fuel cell using the same.

A solid oxide fuel cell (SOFC) has a high operating temperature of 700°C to 1000°C. For this reason, solid oxide fuel cells (SOFCs) are required to have lower operating temperatures. Proton conducting ceramic fuel cells (PCFCs) using proton conductor electrolytes as electrolytes can have lower operating temperatures compared to solid oxide fuel cells using oxide ion conductors as electrolytes. Furthermore, proton conducting ceramic fuel cells (PCFCs) are expected to be a fuel cell that provides high energy efficiency.

Conventionally, perovskite oxides such as barium zirconate doped with rare earth elements have been used as proton conductor electrolytes for proton conductive ceramic fuel cells (PCFCs). As a method for producing a proton conductor electrolyte made of perovskite oxide, there are, for example, the following methods.

Patent Document 1 describes a method for producing yttrium-doped barium cerate-zirconate (BCZY). Specifically, a specimen with a predetermined composition was first calcined at approximately 1,300°C for approximately 10 hours to form a powder, and then the remolded specimen was calcined for a second time at approximately 1,400°C for approximately 10 hours. The baking results are listed. FIG. 2(a) shows the results measured after only the first calcination, and it is stated that an unreacted phase of barium source (BaCO ₃ ) remains. FIG. 2(b) shows the results of measurements taken after the secondary calcination, and states that all unreacted phases were removed.

Example 1 of Patent Document 2 describes the preparation of scandium-doped barium zirconate represented by BaZr _0.4 Sc _0.6 O _3-δ H _y . Specifically, a solid obtained by heat-treating a reaction solution containing a raw material mixture is heated, and after reaching 900°C, it is fired for 10 hours, then pulverized and formed into pellets, and heated to 1,600°C. It is described that a sintered body having a single perovskite structure was obtained by heat treatment for 24 hours.

Japanese Patent Application Publication No. 2018-190730 International Publication No. 2021/085366

JCPDS Ref. : Mather, G., Inst. De Ceramica y Vidrio, CSIC,Madrid, Spain; Antunes, I., Dept. of Materials and Ceramic Engineering, CICECO, Univ. of Aveiro, Portugal; Fagg, D., Nanotechnology Research Division, Center of Mechanical Technology and Automation, Univ. of Aveiro, Portugal. Private Communication (2012)）

A perovskite oxide conventionally used as a proton conductor electrolyte is barium zirconate doped with rare earth elements. When forming the electrolyte layer of a proton-conducting ceramic fuel cell (PCFC) containing this, an electrolyte material containing components corresponding to the composition of barium zirconate added with rare earth elements is molded into a predetermined shape and heated to 1,400°C. It is fired at higher temperatures. This is because barium zirconate added with rare earth elements has a property of being difficult to sinter.

However, the barium component in the rare earth element-added barium zirconate evaporates when the rare earth element-added barium zirconate reaches a high temperature of over 1,300°C. Therefore, in the conventional manufacturing method, the barium content changes between the electrolyte material before firing and the electrolyte layer made of the sintered body after firing. For this reason, it is difficult to control the composition of rare-earth element-added barium zirconate after firing depending on the ratio of elements used as raw materials for electrolyte materials, and rare-earth element-added barium zirconate having a desired composition is difficult to control. There were cases where it was not possible to obtain As a result, in proton conductive ceramic fuel cells that use barium zirconate added with rare earth elements as a proton conductor electrolyte, properties such as proton conductivity may be insufficient.

In addition, as a proton conductive ceramic fuel cell (PCFC), a cell member consisting of a laminated structure including an air electrode (positive electrode), a fuel electrode (negative electrode), and an electrolyte layer disposed between the air electrode and the fuel electrode There are some that have When the electrolyte layer of such a proton conducting ceramic fuel cell (PCFC) contains barium zirconate added with a rare earth element, it may be manufactured using the method shown below.

That is, a layer formed by molding an electrode material that will become an air electrode (positive electrode), a layer formed by molding an electrolyte material containing components corresponding to the composition of barium zirconate added with rare earth elements, and a fuel electrode (negative electrode). The layers formed by molding the electrode materials are laminated in this order to form a laminate. Thereafter, the laminate is fired to obtain a sintered body in which the air electrode, the electrolyte layer, and the fuel electrode are stacked.

However, when manufacturing a proton conducting ceramic fuel cell (PCFC) using this method, there are the following disadvantages. That is, since it is necessary to sinter the laminate at a high temperature of 1,400°C or higher, the barium component from barium zirconate added with rare earth elements may volatilize as the laminate is sintered, and the electrolyte material and It may react with the electrode material that will become the air electrode (positive electrode) or the fuel electrode (negative electrode). As a result, a proton-conducting ceramic fuel cell having desired characteristics may not be obtained.

The present invention was made in view of the above circumstances, and it can be sintered at a low temperature that suppresses the volatilization of the barium component, it is easy to obtain a single-phase perovskite oxide, and the rare earth element component and barium used as raw materials can be easily obtained. It is an object of the present invention to provide a manufacturing method in which the composition of perovskite oxide contained in a sintered body after firing can be precisely controlled by changing the ratio of the components and the zirconium component.

In addition, the present invention can be sintered at a low temperature that suppresses volatilization of the barium component, and a single-phase perovskite oxide can be easily obtained. It is an object of the present invention to provide a method for manufacturing a perovskite oxide precursor that can accurately control the composition of the perovskite oxide contained in a subsequent sintered body, and a method for manufacturing a fuel cell using the same.

In order to solve the above problems, the present inventors focused on the coprecipitation method, which is one of the liquid phase methods, and conducted extensive studies as shown below.
The present inventors believe that if it is possible to produce a perovskite oxide precursor consisting of a precipitate with a uniform element distribution corresponding to the proportion of elements in the raw material aqueous solution using a coprecipitation method, then by firing this, the perovskite oxide precursor can be produced at a low temperature. It was believed that a single phase perovskite oxide that could be sintered and had the desired composition could be obtained.

More specifically, a perovskite oxide precursor containing a uniform element distribution in a predetermined ratio can be created by arranging each atom into a perovskite crystal structure with little thermal energy and forming a small-sized single-phase perovskite. It becomes oxide particles. Since small particles have a larger surface area than large particles, the contact area between the particles increases with less thermal energy, resulting in a sintered body. Therefore, a perovskite oxide precursor containing predetermined elements in a predetermined ratio with a uniform element distribution can be sintered at a low temperature, and volatilization of the barium component during sintering can be suppressed. Therefore, if the composition of the above-mentioned perovskite oxide precursor corresponds to the proportion of elements in the raw material aqueous solution, sintering of a single-phase perovskite oxide having a composition corresponding to the proportion of elements in the raw material aqueous solution is possible. I thought it would give me a body.

In the coprecipitation method, metal salts of multiple types of elements are precipitated simultaneously in a raw material solution in which multiple types of elements are dissolved, thereby obtaining a precipitate in which multiple types of elements are uniformly mixed. However, it has been difficult to simultaneously precipitate rare earth element components, barium components, and zirconium components in a raw material aqueous solution containing rare earth element ions, barium ions, and zirconium ions. For example, when ammonium hydroxide is added as a precipitant to an aqueous raw material solution, a rare earth element component and a zirconium component are precipitated simultaneously. However, even if ammonium hydroxide is added to the raw material aqueous solution, the barium component hardly precipitates and remains in the raw material aqueous solution.

Therefore, the present inventors focused on the property that a barium carbonate precipitate is generated by blowing carbon dioxide into an aqueous solution containing barium ions, and conducted extensive studies.
As a result, in order to precipitate the barium component together with the rare earth element component and zirconium component in the raw material aqueous solution, it was found that it is important to use a compound that becomes carbonate ions in the raw material aqueous solution as a precipitant. Obtained. Based on this knowledge, the present inventors conducted further studies. Then, by adding a precipitant containing ammonium hydroxide and ammonium hydrogen carbonate in a predetermined ratio to the raw material aqueous solution containing rare earth element ions, barium ions, and zirconium ions, rare earth element components and barium components are added. It has been found that it is possible to sufficiently precipitate the zirconium component and the zirconium component at the same time.

Furthermore, the present inventors confirmed that the obtained precipitate can be sintered at a low temperature that suppresses the volatilization of the barium component, and that it is easy to obtain a single-phase perovskite oxide. The present invention was conceived by confirming that the composition of the perovskite oxide contained in the sintered body was the same as the ratio of the rare earth element component, barium component, and zirconium component in the raw material aqueous solution.

That is, the present invention relates to the following matters.

[1] One or more rare earth element ions selected from scandium, yttrium, lanthanum, cerium, praseodymium, neodymium, samarium, eurobium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium; a raw material aqueous solution preparation step of preparing a raw material aqueous solution containing barium ions and zirconium ions;
Contains ammonium hydroxide and ammonium hydrogen carbonate in an amount of 0.5 to 20 times the total number of moles of rare earth element ions, barium ions, and zirconium ions in the raw material aqueous solution, and Precipitating a perovskite oxide precursor in the mixed solution by adding a precipitant containing 0.08 mol to 0.45 mol of ammonium hydrogen carbonate to the raw material aqueous solution to form a mixed solution. process and
A method for producing a perovskite oxide, comprising a firing step of producing a perovskite oxide by firing the perovskite oxide precursor.

[2] The method for producing a perovskite oxide according to [1], wherein in the precipitation step, the pH of the mixed solution after precipitating the perovskite oxide precursor is set to 9.40 to 9.80.
[3] The method for producing a perovskite oxide according to [1], wherein the rare earth element is yttrium.
[4] The method for producing a perovskite oxide according to [1], wherein in the firing step, the perovskite oxide precursor is fired at a temperature of 900°C to 1300°C.

[5] One or more rare earth element ions selected from scandium, yttrium, lanthanum, cerium, praseodymium, neodymium, samarium, eurobium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium; a raw material aqueous solution preparation step of preparing a raw material aqueous solution containing barium ions and zirconium ions;
Contains ammonium hydroxide and ammonium hydrogen carbonate in an amount of 0.5 to 20 times the total number of moles of rare earth element ions, barium ions, and zirconium ions in the raw material aqueous solution, and Precipitating a perovskite oxide precursor in the mixed solution by adding a precipitant containing 0.08 mol to 0.45 mol of ammonium hydrogen carbonate to the raw material aqueous solution to form a mixed solution. A method for producing a perovskite oxide precursor, comprising the steps of:

[6] The method for producing a perovskite oxide precursor according to [5], wherein in the precipitation step, the pH of the mixed solution after precipitating the perovskite oxide precursor is set to 9.40 to 9.80. .
[7] The method for producing a perovskite oxide precursor according to [5], wherein the rare earth element is yttrium.

[8] A step of producing a perovskite oxide precursor by the method for producing a perovskite oxide precursor according to [5];
A method for manufacturing a fuel cell, comprising a firing step of forming and firing an electrolyte material containing the perovskite oxide precursor to form an electrolyte layer made of a sintered body containing a perovskite oxide.

[9] The method for manufacturing a fuel cell according to [8], wherein in the firing step, the electrolyte material is fired at a temperature of 900°C to 1300°C.

[10] The firing step forms a layer formed by molding the electrode material to become the first electrode, a layer formed by molding the electrolyte material, and a layer formed by molding the electrode material to become the second electrode, A laminate forming step of laminating layers in this order to form a laminate;
Manufacturing the fuel cell according to [8], comprising a laminate firing step of obtaining a sintered body in which the first electrode, the electrolyte layer, and the second electrode are stacked by firing the laminate. Method.

In the method for producing perovskite oxide of the present invention, a raw material aqueous solution containing rare earth element ions, barium ions, and zirconium ions is prepared, and the total molar amount of rare earth element ions, barium ions, and zirconium ions in the raw material aqueous solution is A precipitant containing ammonium hydroxide and ammonium hydrogen carbonate in an amount of 0.5 to 20 times the number, and the number of moles of ammonium hydrogen carbonate per mole of ammonium hydroxide is 0.08 mole to 0.45 mole. A perovskite oxide precursor is precipitated by adding it to a raw material aqueous solution to form a mixed solution, and this is fired to produce a perovskite oxide. The perovskite oxide precursor is a precipitate produced using a coprecipitation method and having a uniform element distribution corresponding to the ratio of rare earth element ions, barium ions, and zirconium ions in the raw material aqueous solution. Therefore, sintering can be performed at a low temperature that can suppress volatilization of the barium component. Further, the composition of the perovskite oxide after sintering can be controlled with high precision by adjusting the ratio of the rare earth element component, barium component, and zirconium component used as raw materials. Therefore, according to the method for producing a perovskite oxide of the present invention, a single-phase perovskite oxide having a desired composition can be easily obtained.

In the fuel cell manufacturing method of the present invention, an electrolyte material containing the above-mentioned perovskite oxide precursor is molded and fired to form an electrolyte layer made of a sintered body. Therefore, an electrolyte layer can be formed by sintering at a low temperature that can suppress volatilization of the barium component, and an electrolyte layer containing a single-phase perovskite oxide can be easily obtained.
In addition, in the fuel cell manufacturing method of the present invention, the electrolyte layer can be formed by sintering at a low temperature that suppresses volatilization of the barium component. It is possible to prevent the volatilized barium component from reacting with electrode materials and the like and deteriorating the characteristics of the fuel cell.

Furthermore, in the fuel cell manufacturing method of the present invention, the composition of the perovskite oxide contained in the electrolyte layer after firing can be controlled with high precision by changing the ratio of the rare earth element component, barium component, and zirconium component used as raw materials for the electrolyte layer. . Therefore, according to the method for manufacturing a fuel cell of the present invention, a fuel cell having desired characteristics can be easily obtained by having an electrolyte layer containing a perovskite oxide having a desired composition.

FIG. 1 is a flowchart for explaining an example of the method for manufacturing perovskite oxide of this embodiment. FIG. 2 is a graph showing the content (residual amount) of barium ions (Ba ²⁺ ) in the mixed solution after precipitating the perovskite oxide precursor in Example 1 and Comparative Examples 1 to 5. FIG. 3 is a graph showing the content (residual amount) of zirconium ions (Zr ⁴⁺ ) in the mixed solution after precipitating the perovskite oxide precursor in Example 1 and Comparative Examples 1 to 5. FIG. 4 shows the perovskite oxides of Example 1 and Comparative Examples 1 to 5, and the chemical composition of BaZr _0.9 Y _0.1 O _3-δ (BZY-10) described in Non-Patent Document 1. 3 is a chart showing the X-ray diffraction results of a perovskite oxide having the following composition.

Hereinafter, the method for producing a perovskite oxide, the method for producing a perovskite oxide precursor, and the method for producing a fuel cell according to the present invention will be explained in detail. Note that the present invention is not limited only to the embodiments shown below.

"Method for producing perovskite oxide"
FIG. 1 is a flowchart for explaining an example of the method for manufacturing perovskite oxide of this embodiment. As shown in FIG. 1, the method for producing perovskite oxide of this embodiment includes a raw material aqueous solution preparation step S1, a precipitation step S2, and a firing step S3.

(perovskite oxide)
The perovskite oxide manufactured using the manufacturing method of this embodiment is barium zirconate doped with a rare earth element represented by the following formula (1).
Ba _1-a Zr _1-x M _x O _3-δ (1)
(M in formula (1) is scandium (Sc), yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), eurobium (Eu), One or more rare earths selected from gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu) It is an element.a<1, 0<x<1, δ<3)

Perovskite is a general term for compounds with a crystal structure in which large metal atoms are arranged at the A site and small metal atoms are arranged at the B site. In the perovskite oxide represented by formula (1), barium ions with a large ionic radius are arranged at the A site, and zirconium ions and rare earth element ions, which have a small ionic radius compared to the barium ions, are arranged at the B site. In the above formula (1), a is a value that provides a non-stoichiometric composition in which barium (Ba) can stably exist as a perovskite phase. δ is the amount of oxygen vacancies corresponding to the amount of oxygen released from the perovskite phase in order to maintain electronic neutrality when substituting atoms with a valence of +3 or less. The properties of the perovskite oxide represented by formula (1) vary depending on the type and amount of rare earth element ions arranged at the B site.

In the perovskite oxide produced using the production method of the present embodiment, a in formula (1) is preferably 0.2 or less, more preferably 0.15 or less. Furthermore, x in formula (1) is preferably from 0.01 to 0.99, more preferably from 0.05 to 0.95.
Preferred perovskite oxides produced using the production method of this embodiment include, specifically, BaZr _0.9 Y _0.1 O _3-δ (BZY-10), BaZr ₀ containing yttrium as a rare earth element. _.95 Y _0.05 O _3-δ (BZY-5), BaZr _0.85 Y _0.15 O _3-δ (BZY-15), BaZr _0.8 Y _0.2 O _3-δ (BZY-20 ), etc.

(Raw material aqueous solution preparation step S1)
In the raw material aqueous solution preparation step S1 in the manufacturing method of this embodiment, a raw material aqueous solution containing rare earth element ions, barium ions, and zirconium ions is prepared.
Rare earth element ions include scandium (Sc), yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm), eurobium (Eu), and gadolinium (Gd). , terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu). be. The rare earth element ions are appropriately determined depending on the characteristics required of the electrolyte layer containing the perovskite oxide manufactured using the manufacturing method of this embodiment.

The above rare earth elements all have an outer electron configuration of s ² p ⁶ and have very similar chemical behavior. Therefore, by adding the precipitating agent described later to the raw material aqueous solution at a predetermined ratio, the above-mentioned rare earth element ions are sufficiently precipitated together with the barium component and the zirconium component, and are dissolved in the raw material aqueous solution. It is difficult to leave a residue.

In this embodiment, among the above-mentioned rare earth element ions, one or more selected from yttrium ions, cerium ions, and ytterbium ions are preferable. This is because when these rare earth element ions are included as rare earth element ions, the electrolyte layer containing the perovskite oxide obtained by the manufacturing method of this embodiment has excellent characteristics.
It is particularly preferable that the rare earth element ions include yttrium ions. This is because when the rare earth element ions include yttrium ions, the electrolyte layer containing the perovskite oxide obtained by the manufacturing method of this embodiment has more excellent characteristics.

The raw material aqueous solution containing rare earth element ions, barium ions, and zirconium ions is, for example, an aqueous solution containing rare earth element ions at a predetermined concentration, an aqueous solution containing barium ions at a predetermined concentration, and an aqueous solution containing barium ions at a predetermined concentration. It can be prepared by preparing an aqueous solution containing zirconium ions and mixing these aqueous solutions at a predetermined ratio. As a result, a raw material aqueous solution is obtained in which the proportions of the rare earth element component, barium component, and zirconium component correspond to the composition of the target perovskite oxide.

As the aqueous solution containing rare earth element ions, the aqueous solution containing barium ions, and the aqueous solution containing zirconium ions used when preparing the raw material aqueous solution, aqueous solutions of salts such as nitrates, chlorides, and sulfates should be used, respectively. I can do it. In this embodiment, it is preferable that at least one of the aqueous solution containing rare earth element ions, the aqueous solution containing barium ions, and the aqueous solution containing zirconium ions is a nitrate aqueous solution, and all of them are nitrate aqueous solutions. It is more preferable. Since nitrates have good solubility in water, raw material aqueous solutions can be easily prepared. Further, the nitrate can be easily removed from the perovskite oxide precursor described later by performing heat treatment such as the firing step S3, and does not remain as an impurity component.

(Precipitation step S2)
Next, a precipitant is added to the raw material aqueous solution to form a mixed solution, thereby precipitating the perovskite oxide precursor in the mixed solution.
In the precipitation step S2 in the production method of the present embodiment, a precipitant is used as a precipitant to reduce the total number of moles (hereinafter sometimes referred to as "total number of moles") of rare earth element ions, barium ions, and zirconium ions in the raw material aqueous solution to zero. One containing ammonium hydroxide and ammonium hydrogen carbonate in an amount of 5 to 20 times, and the number of moles of ammonium hydrogen carbonate per mole of ammonium hydroxide is 0.08 to 0.45 mole. As a result, the rare earth element component, barium component, and zirconium component contained in the raw material aqueous solution are precipitated simultaneously, resulting in precipitation having a uniform element distribution corresponding to the ratio of rare earth element ions, barium ions, and zirconium ions in the raw material aqueous solution. A perovskite oxide precursor is obtained.

In the precipitation step S2, the higher the content of ammonium hydroxide used as a precipitant and the lower the content of ammonium hydrogen carbonate used as a precipitant, the higher the pH of the mixed solution after precipitating the perovskite oxide precursor. On the contrary, the lower the content of ammonium hydroxide and the higher the content of ammonium hydrogen carbonate used as a precipitant, the lower the pH of the mixed solution after precipitating the perovskite oxide precursor.

The higher the pH, the more easily the zirconium component contained in the raw material aqueous solution precipitates. In this embodiment, a precipitant containing ammonium hydroxide in an amount of 0.5 times or more the total number of moles is used. Therefore, the pH of the raw material aqueous solution becomes sufficiently high, and the rare earth element component and zirconium component contained in the raw material aqueous solution can be sufficiently precipitated. In order to further reduce the amount of zirconium component remaining dissolved in the raw material aqueous solution after precipitating the perovskite oxide precursor, the content of ammonium hydroxide is preferably 5 times or more of the total number of moles, More preferably, it is 7 times or more.

The content of ammonium hydroxide contained in the precipitant is 20 times or less of the total number of moles. Therefore, in the raw material aqueous solution, the concentration of ammonium ions (NH ⁴⁺ ) derived from containing ammonium hydroxide does not become too high. Therefore, the reaction between ammonium ions and hydrogen carbonate ions (HCO ₃ ⁻ ) does not inhibit the generation of hydrogen carbonate ions from ammonium hydrogen carbonate, and the concentration of carbonate ions generated from hydrogen carbonate ions can be maintained. . As a result, the barium component contained in the raw material aqueous solution can be sufficiently precipitated together with the rare earth element component and zirconium component contained in the raw material aqueous solution. The content of ammonium hydroxide is preferably 18 times or less, more preferably 15 times or less of the total number of moles, since the concentration of carbonate ions can be more easily ensured.

Further, the content of ammonium hydrogen carbonate contained in the precipitant is 0.08 mol or more per 1 mol of ammonium hydroxide. Therefore, a sufficient carbonate ion concentration in the raw material aqueous solution can be ensured, and the barium component contained in the raw material aqueous solution can be sufficiently precipitated together with the rare earth element component and zirconium component contained in the raw material aqueous solution. Since the barium component remaining in a dissolved state in the raw material aqueous solution after precipitating the perovskite oxide precursor can be further reduced, the content of ammonium hydrogen carbonate is 0.09 per mole of ammonium hydroxide. It is preferably mol or more, more preferably 0.10 mol or more.

Further, the content of ammonium hydrogen carbonate contained in the precipitant is 0.45 mol or less per 1 mol of ammonium hydroxide. Therefore, the pH of the raw material aqueous solution becomes sufficiently high, and the rare earth element component and zirconium component contained in the raw material aqueous solution can be sufficiently precipitated. Since the zirconium component remaining in a dissolved state in the raw material aqueous solution after precipitating the perovskite oxide precursor can be further reduced, the content of ammonium hydrogen carbonate is 0.40 per mole of ammonium hydroxide. The amount is preferably at most mol, more preferably at most 0.35 mol.

In the precipitation step S2 in the production method of the present embodiment, it is preferable that the pH of the mixed solution after precipitating the perovskite oxide precursor is 9.40 to 9.80. When the pH of the above mixed solution is 9.40 or higher, the zirconium component contained in the raw material aqueous solution can be sufficiently precipitated together with the rare earth element component and barium component contained in the raw material aqueous solution, and the perovskite oxide precursor can be precipitated. The amount of zirconium component remaining in a dissolved state in the raw material aqueous solution after precipitation can be further reduced. More preferably, the pH of the mixed solution after precipitating the perovskite oxide precursor is 9.45 or higher. When the pH of the mixed solution after precipitating the perovskite oxide precursor is 9.80 or less, ammonium hydrogen carbonate can be sufficiently contained in the raw material aqueous solution after precipitating the perovskite oxide precursor. Furthermore, the barium component remaining in the dissolved state can be further reduced. More preferably, the pH of the mixed solution after precipitating the perovskite oxide precursor is 9.75 or less.

In the precipitation step S2 in the production method of the present embodiment, a perovskite oxide in which a rare earth element component, a barium component, and a zirconium component are uniformly dispersed is used as a precipitant, along with ammonium hydroxide and ammonium hydrogen carbonate, if necessary. Other precipitants may be used as long as the precursor can be obtained.
Examples of other precipitants include sodium hydroxide and diethanolamine.

Note that when a compound containing sodium such as sodium hydroxide is used as another precipitant, sodium ions may be contained in the perovskite oxide precursor that is the precipitate. Sodium ions contained in the perovskite oxide precursor may inhibit the sinterability of the perovskite oxide precursor. In addition, when sintering is performed to produce an electrolyte layer containing perovskite oxide and at the same time sintering is performed to produce a member other than an electrolyte layer that is integrated with the electrolyte layer, such as an electrode, the perovskite oxide precursor Sodium ions volatilized from the reactor may react with members such as electrodes, causing deterioration of the members such as electrodes. Furthermore, if sodium ions contained in the perovskite oxide precursor remain in the perovskite oxide after sintering, the proton conductivity of the electrolyte layer containing the perovskite oxide may be reduced. Moreover, the sodium ions contained in the perovskite oxide precursor are extremely difficult to remove. Therefore, it is preferable not to use a compound containing sodium as the other precipitant.

Furthermore, when an organic compound such as diethanolamine is used as another precipitant, the perovskite oxide precursor that is the precipitate may contain the organic compound or a substance derived from the organic compound. When this perovskite oxide precursor is fired, a perovskite oxide containing an impurity phase may be generated. Therefore, it is preferable not to use organic compounds as other precipitants.

In the precipitation step S2 in the production method of this embodiment, when adding a precipitant to the raw material aqueous solution to form a mixed solution, it is preferable to add the precipitant while stirring the raw material aqueous solution by a known method.
The precipitant may be added in its entirety to the raw material aqueous solution at once, or may be added in small amounts in multiple portions, depending on the ratio of rare earth element ions, barium ions, and zirconium ions in the raw material aqueous solution. Since it is easier to obtain a precipitate having a more uniform element distribution than adding a precipitate, it is preferable to add small amounts in multiple portions.
Further, ammonium hydroxide and ammonium hydrogen carbonate as precipitants may be mixed at any concentration and ratio and then added to the raw material aqueous solution, or may be added separately. When ammonium hydroxide and ammonium hydrogen carbonate are added separately to the raw material aqueous solution, either ammonium hydroxide or ammonium hydrogen carbonate may be added first.

(Firing process S3)
Next, the perovskite oxide precursor precipitated in the precipitation step S2 is fired. It is preferable that the perovskite oxide precursor is collected from the raw material aqueous solution, crushed, and dried by a known method, such as a method of filtering the raw material aqueous solution using a filter, before firing.
Conventionally known methods can be used as the crushing method and the drying method.

As a method for firing the perovskite oxide precursor, for example, after performing a first firing step of holding at a temperature of 400 to 1000°C in an air atmosphere for 0 to 10 hours, the perovskite oxide precursor is heated to a temperature of 900 to 1300°C in an air atmosphere. A method of carrying out a second firing step in which the temperature is maintained for more than 0 hours to less than 10 hours can be used.

By performing the first firing step, organic substances contained in the perovskite oxide precursor can be removed. As the organic substance contained in the perovskite oxide precursor, for example, in the raw material aqueous solution preparation step S1 mentioned above, one of an aqueous solution containing rare earth element ions, an aqueous solution containing barium ions, and an aqueous solution containing zirconium ions is used. One or more of them include nitrogen oxides caused by using a nitrate aqueous solution. In the first firing step, it is more preferable to hold the temperature at 500 to 900°C for 0 to 5 hours. The first firing step is a step that is performed as necessary, and does not need to be performed.

The second firing step is performed at a temperature higher than the first firing step. It is preferable that the temperature in the second firing step is 900° C. or higher because a sintered body of perovskite oxide having clear crystallinity can be obtained. The temperature in the second firing step is preferably 1000° C. or higher because the holding time in the second firing step can be reduced and productivity can be improved.

The barium component contained in the perovskite oxide precursor volatilizes when the temperature of the perovskite oxide precursor reaches a high temperature of over 1,300°C. However, the perovskite oxide precursor manufactured by the manufacturing method of this embodiment can be sintered at low temperatures, and a single-phase perovskite oxide can be easily obtained. Therefore, the firing temperature in the second firing step can be lowered to a temperature at which the barium component is difficult to volatilize. When the temperature in the second firing step is 1300° C. or lower, preferably 1200° C. or lower, the barium component contained in the perovskite oxide precursor can be effectively prevented from volatilizing during firing. As a result, the composition of the perovskite oxide obtained after firing can be precisely controlled by the ratio of the rare earth element component, barium component, and zirconium component in the raw material aqueous solution used as the raw material for the perovskite oxide precursor.

It is preferable that the time to be maintained within the above temperature range in the second firing step is longer than 0 hours because a sintered body containing a perovskite oxide having clear crystallinity can be obtained. The holding time in the second firing step is more preferably 0.5 hours or more. When the time for maintaining the temperature within the above temperature range is 10 hours or less, productivity is improved and it is possible to more effectively prevent the barium component contained in the perovskite oxide precursor from volatilizing during firing. The holding time in the second firing step is more preferably 9.5 hours or less.
By performing the above steps, a perovskite oxide is obtained.

[Method for producing perovskite oxide precursor, method for producing fuel cell]
The method for manufacturing a fuel cell according to the present embodiment includes the steps of manufacturing a perovskite oxide precursor by the method for manufacturing a perovskite oxide precursor according to the present embodiment, and molding and baking an electrolyte material containing the perovskite oxide precursor. This includes a firing step of forming an electrolyte layer made of a sintered body containing perovskite oxide.
In the fuel cell manufacturing method of this embodiment, steps other than the step of manufacturing the perovskite oxide precursor and the firing step can be performed using known methods.
The method for producing a perovskite oxide precursor according to the present embodiment includes the raw material aqueous solution preparation step S1 and the precipitation step S2 in the method for producing a perovskite oxide according to the present embodiment described above.

(Fuel cell)
The fuel cell manufactured using the manufacturing method of this embodiment is a proton conducting ceramic fuel cell (PCFC), and the perovskite oxide precursor manufactured using the manufacturing method of this embodiment is used as an electrolyte material forming an electrolyte layer. It uses an electrolyte material containing. Therefore, other than the electrolyte material forming the electrolyte layer, conventionally known materials can be used.
The fuel cell manufactured using the manufacturing method of this embodiment includes, for example, an air electrode (positive electrode) as a first electrode, a fuel electrode (negative electrode) as a second electrode, and a space between the air electrode and the fuel electrode. Examples include cell members having a laminated structure including an electrolyte layer disposed in the cell member. The cell member may have only one layer of a laminated structure, or may have a plurality of layers.

As the air electrode material forming the air electrode (positive electrode), a known material used as an air electrode material of a proton-conducting ceramic fuel cell can be used, and a material containing an electrode material and an electrolyte material can be used. is preferred. Examples of electrode materials that can be used as air electrode materials include La _0.6 Ba _0.4 CoO _3-δ , La _0.8 Sr _0.2 FeO _3-δ , La _0.6 Sr _0.4 Co _{0. 2} Fe _0.8 O _3-δ , La _0.7-0.8 Sr _0.2-0.3 Mn _1.02-1.05 O _3-δ , La ₂ Zr ₂ O ₇ , La _5.5 Examples include one or more composite metal oxides selected from WO _12-δ and the like. As the electrolyte material that can be used as the air electrode material, known electrolyte materials used in proton-conducting ceramic fuel cells can be used, and preferably include a perovskite oxide precursor produced by the production method of the present embodiment. .

As the fuel electrode material forming the fuel electrode (negative electrode), a known material used as a fuel electrode material of a proton-conducting ceramic fuel cell can be used, and a material containing an electrode material and an electrolyte material can be used. is preferred. Examples of electrode materials that can be used as fuel electrode materials include Ni and/or Ni-containing oxides. As the electrolyte material that can be used as the fuel electrode material, known electrolyte materials used in proton-conducting ceramic fuel cells can be used, and preferably include the perovskite oxide precursor produced by the production method of the present embodiment. .
The air electrode (positive electrode) and the fuel electrode (negative electrode) may be made of the same material, or may be made of different materials.

The electrolyte material forming the electrolyte layer may be only the perovskite oxide precursor manufactured by the manufacturing method of this embodiment, or may be any other known material used for the electrolyte layer of a proton-conducting ceramic fuel cell. May contain. Known materials include, for example, electrolytes such as strontium zirconate doped with rare earth elements.

The air electrode material, fuel electrode material, and electrolyte material used in the manufacturing method of this embodiment each contain known additives such as a sintering aid such as an oxide containing a transition metal element, if necessary. It's okay.

The fuel cell manufactured using the manufacturing method of this embodiment may have other layers in addition to the air electrode, fuel electrode, and electrolyte layer. Other layers include, for example, an intermediate layer consisting of Gd _0.1 Ce _0.9 O ₂ , BaZr _0.1 Ce _0.7 Y _0.1 Yb _0.1 O _3-δ , Ni, Ag, Au, Examples include a current collector layer made of Pt.
In the fuel cell manufactured using the manufacturing method of this embodiment, a laminated structure having an air electrode, an electrolyte layer, and a fuel electrode is sealed with a sealing material whose main component is vermiculite, which is a silicate mineral, or glass. may have been done.

In the firing step in the fuel cell manufacturing method of this embodiment, an electrolyte material containing a perovskite oxide precursor is shaped and fired to form an electrolyte layer made of a sintered body containing a perovskite oxide.
The perovskite oxide precursor contained in the electrolyte material is preferably collected from the raw material aqueous solution, crushed, and dried by a known method, such as a method of filtering the raw material aqueous solution using a filter, before molding. .
Conventionally known methods can be used as the crushing method and the drying method.

In the firing step in this embodiment, at the same time as firing for manufacturing an electrolyte layer containing perovskite oxide, members that are not an electrolyte layer but are integrated with the electrolyte layer, such as an air electrode and/or a fuel electrode, are fired. Firing may also be performed to produce.
Specifically, when manufacturing a fuel cell including a stacked structure having an air electrode, an electrolyte layer, and a fuel electrode using the fuel cell manufacturing method of this embodiment, a simultaneous firing method is used in the firing process. It may be manufactured or may be manufactured using a sequential firing method. The co-firing method is a method in which materials forming the air electrode, electrolyte layer, and fuel electrode are laminated and then fired all at once to produce a laminated structure. The sequential firing method is a method in which firing is performed each time the air electrode, electrolyte layer, and fuel electrode layers are formed. The simultaneous firing method is preferable because it can efficiently produce a laminated structure with fewer work steps than the sequential firing method.

When a simultaneous firing method is used in the firing process of this embodiment, a layer formed by molding an electrode material to become an air electrode (positive electrode), a layer formed by molding an electrolyte material, and an electrode material to become a fuel electrode (negative electrode) The air electrode (positive electrode), the electrolyte layer, and the fuel electrode (negative electrode) are laminated by a laminate forming process in which the layers formed by molding are laminated in this order to form a laminate, and the laminate is fired. and a laminate firing step to obtain a sintered body.

In the case of manufacturing using the simultaneous firing method, the method for firing the laminate is, for example, after performing the first firing step, similar to the firing step S3 in the method for manufacturing perovskite oxide of the present embodiment described above. A method of performing a second firing step, etc. can be used.

In the case of manufacturing using the sequential firing method, the method for firing the electrolyte material containing the shaped perovskite oxide precursor includes, for example, the same firing step S3 in the perovskite oxide manufacturing method of the present embodiment as described above. A method such as performing a second firing step after performing the first firing step can be used. This makes it possible to form an electrolyte layer containing perovskite oxide.

When manufacturing using the sequential firing method, the conventional method for firing the layer formed by molding the electrode material to become the air electrode (positive electrode) and the layer formed by molding the electrode material to become the fuel electrode (negative electrode) is A known firing method can be used.
By performing the above steps, a proton conductive ceramic fuel cell (PCFC) having an electrolyte layer containing a perovskite oxide manufactured by the manufacturing method of this embodiment is obtained.

Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited to the specific embodiments described above, and within the scope of the gist of the present invention described within the scope of the claims. Various modifications and changes are possible.

Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples. Note that the present invention is not limited to the following examples.

"Example 1"
(Raw material aqueous solution preparation step S1)
19.0068 g of barium nitrate was dissolved in 1 L of distilled water to obtain an aqueous barium nitrate solution with a concentration of 0.07521 mol·L. Further, 29.0005 g of zirconium nitrate oxide dihydrate was dissolved in 2 L of distilled water to obtain an aqueous zirconium nitrate solution having a concentration of 0.05389 mol·L. Further, 8.3577 g of yttrium nitrate hexahydrate was dissolved in 1 L of distilled water to prepare an aqueous yttrium nitrate solution having a concentration of 0.02167 mol·L.

The concentration of each nitrate aqueous solution was measured and determined using a high-frequency inductively coupled plasma emission spectrometer (ICP) device (trade name: SPS3500, manufactured by Hitachi High-Tech Science).
201.5 mL of barium nitrate aqueous solution, 253.5 mL of zirconium nitrate aqueous solution, and 70 mL of yttrium nitrate aqueous solution were mixed, and stirred for 5 minutes at 600 rpm using a stirrer, and the ratio of yttrium component, barium component, and zirconium component was determined to be the desired amount. A raw material aqueous solution corresponding to the composition of perovskite oxide (BaZr _0.9 Y _0.1 O _3-δ ) was prepared.

(Precipitation step S2)
As precipitants, an aqueous ammonium hydrogen carbonate solution with a concentration of 2.11 mol/L and an aqueous ammonium hydroxide solution with a concentration of 14.8 mol/L were prepared.
Then, while stirring the raw material aqueous solution at 600 rpm using a stirrer, 15 mL of ammonium hydrogen carbonate aqueous solution is added to the raw material aqueous solution, followed by 20 mL of ammonium hydroxide aqueous solution to form a mixed solution, and the mixture is maintained at 90° C. for 45 minutes. This precipitated the perovskite oxide precursor. The aqueous ammonium hydrogen carbonate solution and the aqueous ammonium hydrogen carbonate solution were each added drop by drop using a dropper.

As shown in Table 1, the amount of ammonium hydrogen carbonate used as a precipitant was set to be one times the total number of moles of yttrium ions, barium ions, and zirconium ions in the raw material aqueous solution. Further, the amount of ammonium hydroxide used as a precipitant was 10 times the total number of moles. Therefore, the number of moles of ammonium hydrogen carbonate per mole of ammonium hydroxide is 0.10 mole.

The pH of the mixed solution after precipitating the perovskite oxide precursor was measured by the method shown below. As a result, the pH of the mixed solution was 9.72. The results are shown in Table 1.
(pH measurement)
The pH of the mixed solution after precipitating the perovskite oxide precursor as a test specimen was measured at 30° C. while stirring at 600 rpm using a stirrer.
A glass electrode type hydrogen ion concentration indicator (manufactured by TOADKK TOADKK, Model IM-22P, No. SS994) was used to measure the pH. Before measurement, calibration was performed using the method shown below. First, calibration was performed using a neutral phosphate pH standard solution (pH=6.86 at 25°C). Next, it was calibrated using a phthalate pH standard solution (pH=4.01 at 25°C). Thereafter, it was calibrated using a borate pH standard solution (pH=9.18 at 25°C). After the calibration was completed, the tip of the sensor was washed with distilled water and used for measurement.

In addition, the contents (residual amounts) of yttrium ions (Y ³⁺ ), barium ions (Ba ²⁺ ), and zirconium ions (Zr ⁴⁺ ) contained in the mixed solution after precipitating the perovskite oxide precursor are shown below. It was measured by the method. As a result, yttrium ions and zirconium ions were below the detection limit. The detection limit for barium ions is 4×10 ⁻¹⁰ mol/L, the detection limit for zirconium ions is 5×10 ⁻⁹ mol/L, and the detection limit for yttrium ions is 2×10 ⁻⁹ mol/L.
Regarding barium ions, the ratio to the amount of barium ions used as a raw material in the raw material aqueous solution (the content of Ba ions remaining in the mixed solution (%) = {the amount of ions in the mixed solution (mol) / the amount of barium ions in the raw material aqueous solution) The amount of ions (mol)}×100) was calculated. As a result, the content of barium ions remaining in the mixed liquid was 0.085%. The results are shown in Table 1.

(Measurement of the content of Ba ²⁺ , Zr ⁴⁺ and Y ³⁺ remaining in the mixed solution)
A high-frequency inductively coupled plasma emission spectrometer (ICP) device (trade name: SPS3500, manufactured by Hitachi High-Tech Science) was used to measure the contents of Ba ²⁺ , Zr ⁴⁺ , and Y ³⁺ .
When plasma energy is externally applied to an analysis sample using an ICP device, component elements (atoms) contained in the analysis sample are excited. ICP devices detect the emission lines (spectral lines) emitted when the excited atoms return to lower energy levels. Then, the type of component element is determined from the position (wavelength) of the detected emission line, and the content of each element is determined from the intensity of the emission line.

When measuring the content of Ba ²⁺ remaining in the mixed solution using an ICP device, three Ba standard solutions of known concentrations (49.95 ppm, 24.975 ppm, 9.99 ppm) and a blank solution are used. A calibration curve was created using
In addition, when measuring the content of Zr ⁴⁺ using an ICP device, calibration is performed using three Zr standard solutions of known concentrations (10.01 ppm, 5.005 ppm, 2.002 ppm) and a blank solution. Created a line.
In addition, when measuring the content of Y ³⁺ using an ICP device, three Y standard solutions of known concentrations (24.925 ppm, 9.97 ppm, 4.995 ppm) and a blank solution are used for calibration. Created a line.
Then, the concentrations of Ba ²⁺ , Zr ⁴⁺ , and Y ³⁺ in each solution were determined by applying the intensity of the luminescent line detected from each analysis sample to the respective calibration curves of Ba ²⁺ , Zr ⁴⁺ , and Y ³⁺ .

(Firing process S3)
The perovskite oxide precursor was collected by filtering the mixed solution after precipitating the perovskite oxide precursor in the precipitation step S2 using a filter. Next, the collected perovskite oxide precursor was crushed for 15 minutes using an alumina mortar.
A first firing step was performed in which the crushed perovskite oxide precursor was held at 600° C. for 2 hours in an air atmosphere using a high-temperature furnace (product name: HT04/17, manufactured by Nabertherm).
The perovskite oxide precursor after the first firing was subjected to uniaxial pressure molding at 200 MPa to obtain pellets with a diameter of 13 mm. A second firing step was performed in which the obtained pellets were held at 1200° C. for 5 hours in the air using a high-temperature furnace (trade name: HT04/17, manufactured by Nabertherm).
By performing the above steps, the perovskite oxide of Example 1 was obtained.

"Comparative Example 1 to Comparative Example 5"
In the precipitation step S2, the amount of ammonium hydrogen carbonate and the amount of ammonium hydroxide used as a precipitant were determined by the ratio of the number of moles shown in Table 1 to the total number of moles of yttrium ions, barium ions, and zirconium ions in the raw material aqueous solution, respectively. Perovskite oxides of Comparative Examples 1 to 5 were obtained in the same manner as in Example 1, except that the perovskite oxides were doubled.

In Comparative Examples 1 to 5, the pH of the mixed solution after precipitating the perovskite oxide precursor was measured in the same manner as in Example 1. The results are shown in Table 1.

Furthermore, in Comparative Examples 1 to 5, the contents of yttrium ions (Y ³⁺ ), barium ions (Ba ²⁺ ), and zirconium ions (Zr ⁴⁺ ) contained in the mixed solution after precipitating the perovskite oxide precursor (Residual amount) was measured in the same manner as in Example 1. The results are shown in Table 1.
Regarding barium ions, the ratio to the amount of barium ions used as a raw material for the raw material aqueous solution was calculated in the same manner as in Example 1.
Furthermore, for zirconium ions that were not below the detection limit, the ratio to the amount of zirconium ions used as a raw material for the raw material aqueous solution was calculated in the same manner as for barium ions. The results are shown in Table 1.

Further, the content (residual amount) of barium ions (Ba ²⁺ ) in the mixed solution after precipitating the perovskite oxide precursor in Example 1 and Comparative Examples 1 to 5 is shown in FIG.
Further, the content (residual amount) of zirconium ions (Zr ⁴⁺ ) in the mixed solution after precipitating the perovskite oxide precursor in Example 1 and Comparative Examples 1 to 5 is shown in FIG.

As shown in Table 1 and FIG. 2, in Example 1, the content (residual amount) of barium ions (Ba ²⁺ ) contained in the mixed solution after precipitating the perovskite oxide precursor was very small. Furthermore, as shown in Table 1 and FIG. 3, in Example 1, the content (residual amount) of zirconium ions (Zr ⁴⁺ ) contained in the mixed solution after precipitating the perovskite oxide precursor was below the detection limit. Met. Furthermore, as shown in Table 1, in Example 1, the content (residual amount) of yttrium ions (Y ³⁺ ) contained in the mixed solution after precipitating the perovskite oxide precursor was also below the detection limit. .

On the other hand, as shown in Table 1 and Figure 2, in Comparative Example 1, the content (residual amount) of barium ions (Ba ²⁺ ) contained in the mixed solution after precipitating the perovskite oxide precursor was extremely low. There were many This shows that it is difficult to precipitate the barium component when only ammonium hydroxide is used as a precipitant.

Furthermore, as shown in Table 1 and FIG. 3, in Comparative Examples 3 to 5, the content (residual amount) of zirconium ions (Zr ⁴⁺ ) contained in the mixed solution after precipitating the perovskite oxide precursor was high. Ta. This indicates that it is difficult to sufficiently precipitate the zirconium component when only ammonium hydrogen carbonate is used as a precipitant, or when ammonium hydrogen carbonate and a small amount of ammonium hydroxide are used as precipitants. I understand.

"Example 2"
(Raw material aqueous solution preparation step S1)
A barium nitrate aqueous solution, a zirconium nitrate aqueous solution, and an yttrium nitrate aqueous solution are mixed, and the ratio of the yttrium component, barium component, and zirconium component is determined to be the desired perovskite oxide (BaZr _0.95 Y _0.05 O _3-δ A perovskite oxide of Example 2 was obtained in the same manner as in Example 1, except that a raw material aqueous solution corresponding to the composition of (BZY-5)) was prepared.

"Example 3"
(Raw material aqueous solution preparation step S1)
A barium nitrate aqueous solution, a zirconium nitrate aqueous solution, and an yttrium nitrate aqueous solution are mixed, and the ratio of yttrium component, barium component, and zirconium component is determined to be the desired perovskite oxide (BaZr _0.85 Y _0.15 O _3-δ A perovskite oxide of Example 3 was obtained in the same manner as in Example 1, except that a raw material aqueous solution corresponding to the composition of (BZY-15)) was prepared.

"Example 4"
(Raw material aqueous solution preparation step S1)
A barium nitrate aqueous solution, a zirconium nitrate aqueous solution, and a yttrium nitrate aqueous solution are mixed, and the ratio of the yttrium component, barium component, and zirconium component is determined to be the desired perovskite oxide (BaZr _0.8 Y _0.2 O _3-δ). A perovskite oxide of Example 4 was obtained in the same manner as in Example 1, except that a raw material aqueous solution corresponding to the composition of (BZY-20)) was prepared.

In Examples 2 to ^{4 , the} content (residual amount) was measured in the same manner as in Example 1. The results are shown in Table 2.
Regarding barium ions, the ratio to the amount of barium ions used as a raw material for the raw material aqueous solution was calculated in the same manner as in Example 1.

As shown in Table 2, in Examples 2 to 4, the content (residual amount) of barium ions (Ba ²⁺ ) contained in the mixed solution after precipitating the perovskite oxide precursor was very small. . Furthermore, as shown in Table 2, in Examples 2 to 4, the content (residual amount) of zirconium ions (Zr ⁴⁺ ) contained in the mixed solution after precipitating the perovskite oxide precursor was below the detection limit. It was below. Furthermore, as shown in Table 2, in Examples 2 to 4, the content (residual amount) of yttrium ions (Y ³⁺ ) contained in the mixed solution after precipitating the perovskite oxide precursor also reached the detection limit. It was below.

In addition, X-ray diffraction (XRD) measurements were performed on the perovskite oxides of Example 1 and Comparative Examples 1 to 5 using an X-ray diffraction device (trade name: SmartLab/RA/DX: manufactured by Rigaku). Ta. The results are shown in FIG.
FIG. 4 is a chart showing the X-ray diffraction results of the perovskite oxides of Example 1 and Comparative Examples 1 to 5. FIG. 4 shows charts of perovskite oxides of Example 1 and Comparative Examples 1 to 5, as well as charts of BaZr _0.9 Y _0.1 O _3-δ (BZY-10) described in Non-Patent Document 1. Also included is a chart showing the X-ray diffraction results for perovskite oxides having the chemical compositions shown.

As shown in FIG. 4, the perovskite oxide of Example 1 and the perovskite oxide having the chemical composition represented by BaZr _0.9 Y _0.1 O _3-δ (BZY-10) described in Non-Patent Document 1 The peak position in X-ray diffraction is the same for both materials. From this, it can be confirmed that the perovskite oxide of Example 1 is a single-phase perovskite oxide having a chemical composition represented by BaZr _0.9 Y _0.1 O _3-δ (BZY-10). Ta.

Further, the perovskite oxides of Comparative Examples 1 to 5 are similar to the perovskite oxide of Example 1, and the perovskite oxides of BaZr _0.9 Y _0.1 O _3-δ (BZY- The peak position in X-ray diffraction was the same as that of the perovskite oxide having the chemical composition shown in 10). _{However ,} in Comparative Examples ₁ to _{5 ,} as shown in FIG. X-ray diffraction peaks of impurities were also confirmed. From this, it was found that the perovskite oxides of Comparative Examples 1 to 5 were not single-phase perovskite oxides.

In the method for manufacturing a fuel cell of the present invention, an electrolyte material containing a perovskite oxide precursor precipitated using a coprecipitation method is shaped and fired. In the fuel cell manufacturing method of the present invention, since sintering can be performed at a low temperature that can suppress volatilization of the barium component, sintering can be carried out at a low temperature that suppresses volatilization of the barium component. The composition of the subsequent perovskite oxide can be controlled with high precision, and an electrolyte layer containing the perovskite oxide having a desired composition can be formed. Therefore, according to the present invention, it is expected that the characteristics and quality of a fuel cell having an electrolyte layer containing a perovskite oxide will be improved. In addition, in the fuel cell manufacturing method of the present invention, the electrolyte layer can be formed by sintering at a low temperature, so that the components volatilized from the material that will become the electrolyte layer during sintering are mixed with other components that are not the electrolyte layer. It is possible to prevent the reaction from deteriorating the functions of other members other than the electrolyte layer. Furthermore, since it can be sintered at low temperatures, the energy involved in sintering can be reduced. In addition, the inside of the sintering furnace is not contaminated by components volatilized from the material that becomes the electrolyte layer during sintering, making it easier to maintain and manage the manufacturing equipment, and reducing costs associated with the equipment.

Furthermore, the perovskite oxide precursor obtained by the production method of the present invention can be preferably used not only as a material for an electrolyte layer of a proton-conducting ceramic fuel cell (PCFC) but also as a material for an electrolyte layer of an electrolytic device. can.

S1 raw material aqueous solution adjustment step, S2 precipitation step, S3 firing step.

Claims (10)

One or more rare earth element ions selected from scandium, yttrium, lanthanum, cerium, praseodymium, neodymium, samarium, eurobium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium, and barium ion. , a raw material aqueous solution preparation step of preparing a raw material aqueous solution containing zirconium ions;
Contains ammonium hydroxide and ammonium hydrogen carbonate in an amount of 0.5 to 20 times the total number of moles of rare earth element ions, barium ions, and zirconium ions in the raw material aqueous solution, and Precipitating a perovskite oxide precursor in the mixed solution by adding a precipitant containing 0.08 mol to 0.45 mol of ammonium hydrogen carbonate to the raw material aqueous solution to form a mixed solution. process and
A method for producing a perovskite oxide, comprising a firing step of producing a perovskite oxide by firing the perovskite oxide precursor. The method for producing a perovskite oxide according to claim 1, wherein in the precipitation step, the pH of the mixed solution after precipitating the perovskite oxide precursor is set to 9.40 to 9.80. The method for producing a perovskite oxide according to claim 1, wherein the rare earth element is yttrium. The method for producing a perovskite oxide according to claim 1, wherein in the firing step, the perovskite oxide precursor is fired at a temperature of 900°C to 1300°C. One or more rare earth element ions selected from scandium, yttrium, lanthanum, cerium, praseodymium, neodymium, samarium, eurobium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, and lutetium, and barium ion. , a raw material aqueous solution preparation step of preparing a raw material aqueous solution containing zirconium ions;
Contains ammonium hydroxide and ammonium hydrogen carbonate in an amount of 0.5 to 20 times the total number of moles of rare earth element ions, barium ions, and zirconium ions in the raw material aqueous solution, and Precipitating a perovskite oxide precursor in the mixed solution by adding a precipitant containing 0.08 mol to 0.45 mol of ammonium hydrogen carbonate to the raw material aqueous solution to form a mixed solution. A method for producing a perovskite oxide precursor, comprising the steps of: The method for producing a perovskite oxide precursor according to claim 5, wherein in the precipitation step, the pH of the mixed solution after precipitating the perovskite oxide precursor is set to 9.40 to 9.80. The method for producing a perovskite oxide precursor according to claim 5, wherein the rare earth element is yttrium. producing a perovskite oxide precursor by the method for producing a perovskite oxide precursor according to claim 5;
A method for manufacturing a fuel cell, comprising a firing step of forming and firing an electrolyte material containing the perovskite oxide precursor to form an electrolyte layer made of a sintered body containing a perovskite oxide. The method for manufacturing a fuel cell according to claim 8, wherein in the firing step, the electrolyte material is fired at a temperature of 900°C to 1300°C. The firing step laminates, in this order, a layer formed by molding the electrode material to become the first electrode, a layer formed by molding the electrolyte material, and a layer formed by molding the electrode material to become the second electrode. a laminate forming step of forming a laminate;
Manufacturing the fuel cell according to claim 8, comprising a laminate firing step of obtaining a sintered body in which the first electrode, the electrolyte layer, and the second electrode are stacked by firing the laminate. Method.

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