Composite oxide particles, method for manufacturing an electrolyte membrane, composite electrode, and method for manufacturing composite oxide particles

Abstract

This invention provides composite oxide particles containing proton conductors, which can be produced as dense bodies with a relative density of 90% or more by firing at 1500°C. [Solution] The composite oxide particles of the present disclosure are composite oxide particles that include a proton conductor comprising Ba, at least one selected from the group consisting of Zr and Hf, a trivalent metal element M, and O, and do not contain nickel oxide, wherein the metal element M is at least one selected from the group consisting of Sc, In, Yb, Y, and Gd, and the average particle diameter of the composite oxide particles is less than 100 nm.

Description

[Technical Field]

[0001] This disclosure relates to composite oxide particles, a method for producing an electrolyte membrane, a composite electrode, and a method for producing composite oxide particles. [Background technology]

[0002] As an electrolyte material having proton conductivity, the chemical formula is BaZrMO x A perovskite-type complex oxide represented by this chemical formula is known. In this chemical formula, M is a trivalent substitution element, and x represents the composition ratio of oxygen (O).

[0003] Chemical formula BaZrMO x A liquid-phase synthesis method using complexes such as citric acid or ethylenediaminetetraacetic acid is generally known as a method for producing perovskite-type complex oxides represented by . For example, Patent Document 1 describes a precursor aqueous solution and a method for producing complex oxide particles containing nickel(II) oxide and a barium-based proton conductor such as Ba(Zr,Ce,Y)O3. The precursor aqueous solution described in Patent Document 1 contains a coordinating organic compound that coordinates to the metal ions constituting the complex oxide to be produced, and citric acid and ethylenediaminetetraacetic acid are disclosed as these coordinating organic compounds.

[0004] Furthermore, as a method other than liquid-phase synthesis, Non-Patent Document 1 describes BaZrMO x A synthesis process using a coprecipitation method with NH4HCO3 as a coprecipitation agent is shown to obtain fine particles of the perovskite-type composite oxide represented by [formula]. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2021-91578 [Non-patent literature]

[0006] [Non-Patent Document 1] Yusuke Nagawa et al., "Fabrication of Proton Conductor BaZr1-xYxO3-δ Microparticles Using Two Precipitants, NH4HCO3 and NH4OH," Fuel Cells Vol.22 No.4 2023. [Overview of the project] [Problems that the invention aims to solve]

[0007] According to the manufacturing method proposed in Patent Document 1, nanoparticles of a composite oxide containing a barium-based proton conductor and nickel(II) oxide can be produced by heat treatment at a relatively low temperature. However, methods for synthesizing nanoparticles of a composite oxide containing a barium-based proton conductor but not nickel oxide at low temperatures have not been previously investigated. Therefore, it is difficult to obtain particles with a particle size of less than 100 nm for a composite oxide containing a barium-based proton conductor but not nickel oxide using the conventional manufacturing method proposed in Patent Document 1.

[0008] In the manufacturing method proposed in Non-Patent Document 1, particle growth occurs due to heat treatment of the precursor at high temperatures, making it difficult to obtain composite oxide particles on the nanometer order, and the average particle size of the obtained particles is on the order of several hundred nanometers. As a result, the composite oxide particles obtained by the manufacturing method proposed in Non-Patent Document 1 have a small surface area, so it is assumed that it will be difficult to obtain a dense material (for example, a dense material with a relative density of 90% or more) at low temperatures (for example, around 1500°C) using these composite oxide particles. For example, when using composite oxide particles obtained by the manufacturing method proposed in Non-Patent Document 1 as an electrolyte membrane, it is assumed that it will be difficult to obtain a dense electrolyte membrane at low temperatures. Furthermore, when these composite oxide particles are used in a composite electrode, the surface area will be small, and it is possible that the catalytic activity will be insufficient.

[0009] Conventional technologies have made it difficult to provide composite oxide particles containing a barium-based proton conductor and free of nickel oxide, which can be produced as a dense body with a relative density of 90% or more by firing at 1500°C.

[0010] Therefore, the present disclosure aims to provide composite oxide particles containing a proton conductor that can be produced as a dense body with a relative density of 90% or more by firing at 1500°C. [Means for solving the problem]

[0011] This disclosure is, A composite oxide particle comprising a proton conductor containing Ba, at least one selected from the group consisting of Zr and Hf, a trivalent metal element M, and O, and not containing nickel oxide, The aforementioned metal element M is at least one selected from the group consisting of Sc, In, Yb, Y, and Gd. The average particle size of the composite oxide particles is less than 100 nm. We provide composite oxide particles. [Effects of the Invention]

[0012] This disclosure provides composite oxide particles containing a proton conductor, which can be produced as a dense body with a relative density of 90% or more by firing at 1500°C. [Brief explanation of the drawing]

[0013] [Figure 1] Figure 1 is a flowchart showing the method for producing composite oxide particles according to Embodiment 2. [Figure 2] Figure 2 is a flowchart showing the method for producing composite oxide particles according to Example 1. [Figure 3] Figure 3 is a flowchart showing the method for producing a composite oxide according to Comparative Example 2. [Figure 4] Figure 4 is a graph showing the structural analysis results of the composite oxide particles of Examples 1 to 7 and Comparative Examples 1 to 4 by X-ray diffraction (XRD). [Figure 5A] Figure 5A shows a scanning electron microscope (SEM) image of the composite oxide particles BaZr0.8Yb0.2O3-δ produced in Example 1. [Figure 5B] Figure 5B is a graph showing the particle size analysis results of the composite oxide particles BaZr0.8Yb0.2O3-δ from Example 1, obtained using the SEM image shown in Figure 5A. [Figure 6A] Figure 6A shows an SEM image of the composite oxide particles BaZr0.85Yb0.15O3-δ produced in Example 2. [Figure 6B] Figure 6B is a graph showing the particle size analysis results of the composite oxide particles BaZr0.85Yb0.15O3-δ from Example 2, obtained using the SEM image shown in Figure 6A. [Figure 7A] Figure 7A shows an SEM image of the composite oxide particles BaZr0.9Yb0.1O3-δ produced in Example 3. [Figure 7B] Figure 7B is a graph showing the particle size analysis results of the composite oxide particles BaZr0.9Yb0.1O3-δ from Example 3, obtained using the SEM image shown in Figure 7A. [Figure 8A] Figure 8A shows an SEM image of the composite oxide particles BaZr0.8In0.2O3-δ produced in Example 4. [Figure 8B] Figure 8B is a graph showing the particle size analysis results of the composite oxide particles BaZr0.8In0.2O3-δ from Example 4, obtained using the SEM image shown in Figure 8A. [Figure 9A] Figure 9A shows an SEM image of the composite oxide particles BaZr0.8Gd0.2O3-δ produced by Example 5. [Figure 9B] Figure 9B is a graph showing the particle size analysis results for the composite oxide particles BaZr0.8Gd0.2O3-δ from Example 5, obtained using the SEM image shown in Figure 9A. [Figure 10A] Figure 10A shows an SEM image of the composite oxide particles BaHf0.8Yb0.2O3-δ produced in Example 6. [Figure 10B]Figure 10B is a graph showing the particle size analysis results of the composite oxide particles BaHf0.8Yb0.2O3-δ from Example 6, obtained using the SEM image shown in Figure 10A. [Figure 11A] Figure 11A shows an SEM image of the composite oxide particles BaZr0.8Sc0.2O3-δ produced in Example 7. [Figure 11B] Figure 11B is a graph showing the particle size analysis results of the composite oxide particles BaZr0.8Sc0.2O3-δ according to Example 7, obtained using the SEM image shown in Figure 11A. [Figure 12A] Figure 12A shows an SEM image of the composite oxide particles BaZr0.8Yb0.2O3-δ from Comparative Example 1. [Figure 12B] Figure 12B is a graph showing the particle size analysis results for the composite oxide particles BaZr0.8Yb0.2O3-δ from Comparative Example 1, obtained using the SEM image shown in Figure 12A. [Figure 13A] Figure 13A shows an SEM image of the composite oxide particles BaZr0.8Yb0.2O3-δ from Comparative Example 2. [Figure 13B] Figure 13B is a graph showing the particle size analysis results for the composite oxide particles BaZr0.8Yb0.2O3-δ from Comparative Example 2, obtained using the SEM image shown in Figure 13A. [Figure 14] Figure 14 is a graph showing the results of XRD structural analysis measurements when the heat treatment temperature for obtaining composite oxide particles was changed in Example 1. [Figure 15] Figure 15 is a graph showing the composition of the product when the molar ratio of tetramethylammonium bicarbonate to tetramethylammonium hydroxide is changed, for example, when tetramethylammonium bicarbonate and tetramethylammonium hydroxide are used as additives in the production of composite oxide particles in Example 1. [Modes for carrying out the invention]

[0014] [The process leading to obtaining one embodiment of the present invention] The inventors of the above chemical formula BaZrMO x We conducted thorough research on perovskite-type composite oxides represented by [formula]. As a result, we obtained the following findings.

[0015] Chemical formula BaZrMO x As a method for producing perovskite-type complex oxides represented by [formula], liquid-phase synthesis using complexes such as citric acid or ethylenediaminetetraacetic acid is generally known, as described above. In liquid-phase synthesis, powder can be produced by heating an aqueous solution containing cations. In this method, particle growth occurs due to heating at high temperatures, making it difficult to obtain nanometer-order particles.

[0016] As an alternative to liquid-phase synthesis, a method using coprecipitation, as shown in Non-Patent Document 1 above, has been disclosed. In this method, by adding NH4HCO3 to an aqueous solution containing cations and allowing coprecipitation, it is possible to synthesize complex oxides with smaller particle sizes than those obtained by the liquid-phase synthesis method. However, in this method, NH4HCO3 is added to an acidic aqueous solution of raw materials, so CO3 2- It is conceivable that the decomposition of Ba and the generation of BaCO3 would make it difficult to control the composition of Ba. Furthermore, Non-Patent Document 1 discloses that the particle size of the fabricated nanoparticles is 121 nm or larger, making it unsuitable as a method for fabricating nanoparticles smaller than 100 nm.

[0017] Therefore, the inventors have found that by using tetramethylammonium bicarbonate and tetramethylammonium hydroxide as additives, it is possible to synthesize composite oxide particles having an average particle size of less than 100 nm while controlling the composition of Ba. Furthermore, it has been found that a dense material can be produced by heat-treating the composite oxide particles having an average particle size of less than 100 nm at a low temperature of 1500°C or less.

[0018] Furthermore, the inventors have found that, for composite oxide particles made using tetramethylammonium bicarbonate and tetramethylammonium hydroxide as additives, it is desirable that they contain a proton conductor comprising Ba, at least one selected from the group consisting of Zr and Hf, a trivalent metal element M, and O, but without nickel oxide, and that the metal element M is at least one selected from the group consisting of Sc, In, Yb, Y, and Gd.

[0019] Furthermore, Patent Document 1 discloses that the material contains Ni, and that the particle size can be reduced by including Ni. However, when Ni is included, there are concerns that it may reduce proton conductivity or catalytic activity when used in electrolytes or air electrodes.

[0020] The inventors' findings described above were previously unknown, and based on these findings, the inventors discovered a novel problem. The technology described below in this disclosure has novel technical features that produce remarkable effects capable of solving the newly discovered problem.

[0021] [Embodiments of this Disclosure] Embodiments of the present disclosure will be described below with reference to the drawings.

[0022] (Embodiment 1) The composite oxide particles according to Embodiment 1 include a proton conductor comprising Ba, at least one selected from the group consisting of Zr and Hf, a trivalent metal element M, and O, and do not contain nickel oxide. Here, the metal element M is at least one selected from the group consisting of Sc, In, Yb, Y, and Gd. The average particle diameter of the composite oxide particles according to Embodiment 1 is less than 100 nm. The average particle diameter of the composite oxide particles according to Embodiment 1 may be, for example, 90 nm or less.

[0023] As demonstrated in Examples 1 to 7 described later, with the above configuration, the composite oxide particles according to Embodiment 1 can be densely packed with a relative density of 90% or more by firing at 1500°C.

[0024] In this specification, the relative density of a dense body made of composite oxide particles is the ratio (percentage) of the measured density calculated from the mass and volume of the dense body made of composite oxide particles to the theoretical density of the composite oxide constituting the composite oxide particles.

[0025] The average particle size of the composite oxide particles according to Embodiment 1 is preferably 70 nm or less. As demonstrated in Examples 1 to 7 described later, composite oxide particles with an average particle size of 70 nm or less can be more reliably produced as dense bodies with a relative density of 90% or more by firing at 1500°C.

[0026] The lower limit of the average particle diameter of the composite oxide particles according to Embodiment 1 is not particularly limited. For example, the average particle diameter of the composite oxide particles according to Embodiment 1 may be 40 nm or more, or 50 nm or more.

[0027] In this specification, the average particle diameter of composite oxide particles is determined using SEM images of the composite oxide particles. The particle diameters of 100 or more (e.g., 100 to 500) particles arbitrarily selected from the SEM images of the composite oxide particles are determined, for example, using an image analysis device based on the projected area (i.e., the diameter of circles with the same area is identified as the particle diameter), and a particle size distribution based on the number of particles is created. In that particle size distribution, the particle size when the cumulative volume is equal to 50% (i.e., the 50% diameter) is defined as the average particle diameter.

[0028] The composite oxide particles according to Embodiment 1 may be particles made of a single-phase composite oxide. That is, the composite oxide particles according to Embodiment 1 may be particles made of a single-phase composite oxide with an average particle diameter of less than 100 nm. With such a configuration, the composite oxide particles according to Embodiment 1 can more reliably produce a dense body with a relative density of 90% or more, even at a low temperature of 1500°C.

[0029] Here, it can be confirmed that the composite oxide particles are composed of a single-phase composite oxide by observing that the X-ray diffraction pattern obtained by X-ray diffraction measurement of the composite oxide particles does not have diffraction peaks originating from other substances such as impurities, in addition to diffraction peaks originating from a proton conductor containing Ba, at least one selected from the group consisting of Zr and Hf, a trivalent metal element M, and O.

[0030] As described above, the composite oxide particles according to Embodiment 1 include a proton conductor comprising Ba, at least one selected from the group consisting of Zr and Hf, a trivalent metal element M, and O. The composite oxide particles according to Embodiment 1 may substantially consist of a proton conductor comprising Ba, at least one selected from the group consisting of Zr and Hf, a trivalent metal element M, and O. In this disclosure, "the composite oxide particles substantially consist of the above-mentioned proton conductor" means that the molar ratio of the above-mentioned proton conductor in the composite oxide particles is 90% or more, and may be 95% or more. The composite oxide particles according to Embodiment 1 may consist only of the above-mentioned proton conductor.

[0031] The proton conductor contained in the composite oxide particles according to Embodiment 1 may substantially consist of Ba, at least one selected from the group consisting of Zr and Hf, a trivalent metal element M, and O. In this disclosure, when we say that the proton conductor substantially consists of Ba, at least one selected from the group consisting of Zr and Hf, a trivalent metal element M, and O, we mean that the molar ratio (i.e., mole fraction) of the total amount of substance of Ba, Zr, Hf, M, and O to the total amount of substance of all elements constituting the proton conductor is 90% or more. For example, this molar ratio (i.e., mole fraction) may be 95% or more. The proton conductor may consist only of Ba, at least one selected from the group consisting of Zr and Hf, M, and O.

[0032] As demonstrated later in the comparison between Example 1 and Comparative Examples 3 and 4, when the composite oxide particles consist of a proton conductor that does not contain Ca or Sr but contains Ba, the composite oxide particles can be synthesized in a single phase at a low temperature of 1100°C.

[0033] The composite oxide particles according to Embodiment 1 can be manufactured, for example, by the manufacturing method according to Embodiment 2, which will be described later. Figure 1 is a flowchart showing the method for manufacturing composite oxide particles according to Embodiment 1.

[0034] (Embodiment 2) Figure 1 is a flowchart showing the method for producing composite oxide particles according to Embodiment 2. The method for producing composite oxide particles according to Embodiment 2 is: (S11) A precursor of composite oxide particles is obtained from an aqueous solution containing Ba ions, at least one ion selected from the group consisting of Zr ions and Hf ions, M ions which are trivalent metal element ions, tetramethylammonium bicarbonate, and tetramethylammonium hydroxide. (S12) The above precursor is heat-treated to obtain composite oxide particles. Includes.

[0035] The M ion, which is a trivalent metal element ion, is, for example, at least one selected from the group consisting of Sc ions, In ions, Yb ions, Y ions, and Gd ions.

[0036] In the manufacturing method according to Embodiment 2, the aqueous solution for obtaining the precursor of composite oxide particles contains tetramethylammonium bicarbonate and tetramethylammonium hydroxide in addition to the ions of the constituent elements of the composite oxide particles. By using such an aqueous solution, a precursor of composite oxide particles in which the constituent elements of the composite oxide particles are uniformly dispersed can be obtained. By heat-treating this precursor, composite oxide particles can be synthesized at a lower temperature than the heat treatment in conventional manufacturing methods, for example, around 1100°C. Thus, according to the manufacturing method of Embodiment 2, composite oxide particles can be synthesized at a lower temperature than conventional manufacturing methods, thereby suppressing particle growth due to heat treatment and obtaining composite oxide particles with an average particle diameter of less than 100 nm.

[0037] In the aqueous solution used to obtain the precursor of composite oxide particles, the molar ratio of tetramethylammonium bicarbonate to tetramethylammonium hydroxide (amount of tetramethylammonium bicarbonate / amount of tetramethylammonium hydroxide) is preferably 0.7 or higher, and more preferably 0.75 or higher. This allows the composition of the composite oxide particles to be produced to be closer to the desired composition.

[0038] In the aqueous solution used to obtain the precursor of composite oxide particles, the molar ratio of tetramethylammonium bicarbonate to tetramethylammonium hydroxide is preferably 2.0 or less, and more preferably 1.5 or less. This allows the composition of the composite oxide particles to be produced to be closer to the desired composition.

[0039] In the above aqueous solution, the molar ratio of tetramethylammonium bicarbonate to tetramethylammonium hydroxide may be 0.7 or more and 2.0 or less, 0.7 or more and 1.5 or less, 0.75 or more and 2.0 or less, or 0.77 or more and 1.5 or less.

[0040] The above-mentioned precursor is preferably heat-treated at a temperature of, for example, 900°C or higher and 1100°C or lower. By setting the heat treatment temperature of the precursor to 1100°C or lower, particle growth during heat treatment can be suppressed, making it easier to obtain composite oxide particles with an average particle diameter of less than 100 nm, and it is also possible to further reduce the average particle diameter of the resulting composite oxide particles. On the other hand, by setting the heat treatment temperature of the precursor to 900°C or higher, the inclusion of impurities can be prevented, making it possible to obtain composite oxide particles that are closer to single-phase, or even single-phase composite oxide particles.

[0041] (Embodiment 3) The method for producing an electrolyte membrane according to Embodiment 3 includes obtaining a dense electrolyte membrane by firing an electrolyte material containing composite oxide particles according to Embodiment 1 at a temperature exceeding 1100°C and not exceeding 1500°C.

[0042] In the manufacturing method according to Embodiment 3, by using the composite oxide particles according to Embodiment 1, a dense electrolyte membrane can be obtained at a lower temperature of 1500°C or below compared to conventional dense electrolyte membranes. Thus, according to the manufacturing method of Embodiment 3, the firing temperature can be reduced compared to conventional dense electrolyte membranes.

[0043] Herein, in this specification, a dense electrolyte membrane means an electrolyte membrane having a relative density of 90% or more. The relative density of an electrolyte membrane is the ratio (percentage) of the measured density calculated from the mass and volume of the electrolyte membrane to the theoretical density of the constituent materials of the electrolyte membrane.

[0044] The electrolyte material described above contains composite oxide particles according to Embodiment 1, and may consist of composite oxide particles according to Embodiment 1. The electrolyte material may further contain other substances (e.g., other electrolytes) other than the composite oxide particles according to Embodiment 1.

[0045] Methods for forming composite oxide particles into a film include pellet molding using powder molding dies and sheet molding using green sheets. These molded bodies can be fired, for example, in an electric furnace.

[0046] The thickness of the electrolyte membrane is, for example, 1 to 1000 μm.

[0047] The electrolyte membrane obtained by the manufacturing method according to Embodiment 3 has proton conductivity. Therefore, the electrolyte membrane obtained by the manufacturing method according to Embodiment 3 can be used, for example, as an electrolyte membrane for a proton-conducting ceramic fuel cell.

[0048] (Embodiment 4) The composite electrode according to Embodiment 4 includes a conductive air electrode material and composite oxide particles according to Embodiment 1.

[0049] The composite electrode according to Embodiment 4 contains the composite oxide particles according to Embodiment 1. Since the composite oxide particles according to Embodiment 1 have an average particle size of less than 100 nm, the surface area of ​​the composite electrode according to Embodiment 4 can be increased. Therefore, the composite electrode according to Embodiment 4 can improve catalytic activity. As a result, a cell equipped with the composite electrode according to Embodiment 4 can improve power generation performance.

[0050] Examples of conductive air electrode materials include lanthanum strontium cobalt oxide, lanthanum strontium cobalt iron oxide, barium strontium cobalt iron oxide, and barium cobalt oxide.

[0051] The composite electrode according to Embodiment 4 can be applied, for example, to the air electrode of a fuel cell, particularly to the air electrode of a proton-conducting ceramic fuel cell. In this case, the composite electrode according to Embodiment 4 may be provided on an electrolyte membrane, for example, by a screen printing method.

[0052] [Other embodiments] (Note) The above description of embodiments discloses the following technologies.

[0053] (Technology 1) A composite oxide particle comprising a proton conductor containing Ba, at least one selected from the group consisting of Zr and Hf, a trivalent metal element M, and O, and not containing nickel oxide, The aforementioned metal element M is at least one selected from the group consisting of Sc, In, Yb, Y, and Gd. The average particle size of the composite oxide particles is less than 100 nm. Composite oxide particles.

[0054] With this configuration, the composite oxide particles of Technology 1 can be produced as a dense body with a relative density of 90% or more by firing at 1500°C. (Technology 2) The average particle diameter is 70 nm or less. Composite oxide particles as described in Technology 1.

[0055] This configuration allows for the more reliable production of dense bodies with a relative density of 90% or higher by firing the composite oxide particles of Technology 2 at 1500°C.

[0056] (Technology 3) The method includes obtaining a dense electrolyte film by firing an electrolyte material containing composite oxide particles as described in Technology 1 or 2 at a temperature exceeding 1100°C and not exceeding 1500°C. A method for manufacturing an electrolyte membrane.

[0057] This method allows for lower firing temperatures compared to conventional dense electrolyte membranes.

[0058] (Technology 4) A conductive air electrode material, Composite oxide particles as described in Technology 1 or 2, A composite electrode, including one.

[0059] This configuration allows the composite electrode of Technology 4 to improve catalytic activity and thus enhance the power generation performance of the cell.

[0060] (Technology 5) To obtain a precursor of composite oxide particles from an aqueous solution containing Ba ions, at least one ion selected from the group consisting of Zr ions and Hf ions, a trivalent metal element ion M ion, tetramethylammonium bicarbonate, and tetramethylammonium hydroxide, The process involves heat-treating the precursor to obtain the composite oxide particles, A method for producing composite oxide particles, including

[0061] This method allows for the synthesis of composite oxide particles at lower temperatures than conventional manufacturing methods, thereby suppressing particle growth due to heat treatment and enabling the production of composite oxide particles with an average particle diameter of less than 100 nm.

[0062] (Technology 6) The aforementioned M ion is at least one selected from the group consisting of Sc ions, In ions, Yb ions, Y ions, and Gd ions. A method for producing composite oxide particles as described in Technical 5.

[0063] This method allows for the production of composite oxide particles with an average particle size of less than 100 nm, which can be used to create a dense material with a relative density of 90% or more by firing at 1500°C.

[0064] (Technology 7) In the aqueous solution, the molar ratio of tetramethylammonium bicarbonate to tetramethylammonium hydroxide is 0.7 or higher. The method for producing composite oxide particles according to Technique 5 or 6.

[0065] According to this method, the composition of the composite oxide particles to be produced can be controlled to a composition closer to the target composition.

[0066] (Technique 8) The precursor is heat-treated at a temperature of 900 °C or higher and 1100 °C or lower. The method for producing composite oxide particles according to any one of Techniques 5 to 7.

[0067] According to this method, composite oxide particles with an average particle diameter of less than 100 nm can be obtained as composite oxide particles closer to a single phase or single-phase composite oxide particles.

Examples

[0068] Hereinafter, the present disclosure will be described in more detail with reference to the following examples. As described below, in the examples, composite oxide particles and a dense body using the same were produced. Then, the physical properties of the composite oxide particles and the physical properties of the dense body were evaluated.

[0069] [Production of composite oxide particles] (Example 1) FIG. 2 is a flowchart showing the method for producing composite oxide particles according to Example 1. Referring to FIG. 2, the production of composite oxide particles will be described.

[0070] As starting materials for the composite oxide particles, the following materials were prepared. BaCl2·2H2O (manufactured by Kanto Chemical Co., Inc.) 1.66×10 -2 mol ZrO(Cl)2·8H2O (manufactured by Kanto Chemical Co., Inc.) 1.28×10 -2 mol Yb(Cl)3·6H2O (manufactured by Fujifilm Wako Pure Chemical Corporation) 3.77×10 -3 mol

[0071] The above starting materials were added to 172 mL of distilled water and dissolved to obtain a mixture, which was then stirred (S21).

[0072] Next, tetramethylammonium bicarbonate (manufactured by Tama Chemical Industry Co., Ltd.) 6.20 × 10 -2 mol and tetramethylammonium hydroxide (manufactured by Tama Chemical Industry Co., Ltd.) 4.12 × 10 -2 An aqueous solution containing mol was added to the above mixture (S22). That is, 6.20 × 10 -2 moles of tetramethylammonium bicarbonate and 4.12 × 10⁻⁶ -2 The entire volume of the aqueous solution obtained by adding 1 / 2 mol of tetramethylammonium hydroxide to water was added to the above-mentioned mixture. Hereafter, "tetramethylammonium bicarbonate" will be referred to as "TMAHC" and "tetramethylammonium hydroxide" as "TMAH".

[0073] Next, the resulting mixture was stirred to obtain a precipitate (S23, S24).

[0074] The obtained precipitate was filtered and then washed to obtain a solid (S25).

[0075] The obtained solid was dried to obtain a precursor (S26).

[0076] The precursor was heat-treated at 1100°C for 12 hours in an air atmosphere (S27).

[0077] As described above, the chemical formula is BaZr 0.8 Yb 0.2 O 3-δ A composite oxide particle represented by (δ is the amount of oxygen deficiency, 0 ≤ δ < 1.0) was fabricated.

[0078] (Example 2) In Example 2, composite oxide particles were prepared in the same manner as in Example 1, except that the starting materials for the composite oxide particles were changed to the following materials.

[0079] BaCl2·2H2O (manufactured by Kanto Chemical Co., Ltd.) 1.66 × 10 -2 mol ZrO(Cl)2·8H2O (manufactured by Kanto Chemical Co., Ltd.) 1.41 × 10 -2 mol Yb(Cl)3·6H2O (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) 2.49 × 10 -3 mol

[0080] (Example 3) In Example 3, composite oxide particles were prepared in the same manner as in Example 1, except that the starting materials for the composite oxide particles were changed to the following materials.

[0081] BaCl2·2H2O (manufactured by Kanto Chemical Co., Ltd.) 1.66 × 10 -2 mol ZrO(Cl)2·8H2O (manufactured by Kanto Chemical Co., Ltd.) 1.49 × 10 -2 mol Yb(Cl)3·6H2O (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) 1.66 × 10 -3 mol

[0082] (Example 4) In Example 4, composite oxide particles were prepared in the same manner as in Example 1, except that the starting material for the composite oxide particles was changed to the following material.

[0083] BaCl2·2H2O (manufactured by Kanto Chemical Co., Ltd.) 1.66 × 10 -2 mol ZrO(Cl)2·8H2O (manufactured by Kanto Chemical Co., Ltd.) 1.28 × 10 -2 mol In(Cl)3·4H2O (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) 3.77×10 -3 mol

[0084] (Example 5) In Example 5, composite oxide particles were prepared in the same manner as in Example 1, except that the starting materials for the composite oxide particles were changed to the following materials.

[0085] BaCl2·2H2O (manufactured by Kanto Chemical Co., Ltd.) 1.66 × 10 -2 mol ZrO(Cl)2·8H2O (manufactured by Kanto Chemical Co., Ltd.) 1.28 × 10 -2 mol Gd(NO3)3·6H2O (manufactured by Kanto Chemical Co., Ltd.) 3.77 × 10 -3 mol

[0086] (Example 6) In Example 6, composite oxide particles were prepared in the same manner as in Example 1, except that the starting material for the composite oxide particles was changed to the following material.

[0087] BaCl2·2H2O (manufactured by Kanto Chemical Co., Ltd.) 1.66 × 10 -2 mol Hf(Cl)4 (manufactured by Kanto Chemical Co., Ltd.) 1.28 × 10 -2 mol Yb(Cl)3·6H2O (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) 1.66 × 10 -3 mol

[0088] (Example 7) In Example 7, composite oxide particles were prepared in the same manner as in Example 1, except that the starting materials for the composite oxide particles were changed to the following materials.

[0089] BaCl2·2H2O (manufactured by Kanto Chemical Co., Ltd.) 1.66 × 10 -2 mol ZrO(Cl)2·8H2O (manufactured by Kanto Chemical Co., Ltd.) 1.28 × 10 -2 mol Sc(NO3)3·6H2O (manufactured by Daiichi Rare Elements Chemical Industry Co., Ltd.) 1.66 × 10 -3 mol

[0090] (Comparative Example 1) In Comparative Example 1, the composite oxide was prepared in the same manner as in Example 1, except for the following items (1) to (3).

[0091] (1) Starting materials for composite oxide particles The starting materials for the composite oxide particles were changed to the following materials. BaCl2·2H2O (manufactured by Kanto Chemical Co., Inc.) 1.66×10 -2 mol ZrO(Cl)2·8H2O (manufactured by Kanto Chemical Co., Inc.) 1.28×10 -2 mol Yb(Cl)3·6H2O (manufactured by Fujifilm Wako Pure Chemical Corporation) 3.77×10 -3 mol

[0092] (2) Additive Instead of the aqueous solution containing TMAHC and TMAH, a solution prepared by mixing 3.38×10 -2 mol of ammonium bicarbonate (manufactured by Kanto Chemical Co., Inc.) and 3.38×10 -1 mol of aqueous ammonia (manufactured by Fujifilm Wako Pure Chemical Corporation) was added to the above-mentioned mixture.

[0093] (3) Heat treatment conditions of the precursor According to the evaluation items described below, the heat treatment time of the precursor was changed. The composite oxide particles for crystal structure analysis of the particles were prepared by heat-treating the precursor at 1100 °C for 12 hours in an air atmosphere, similar to Example 1. The composite oxide particles for particle size analysis and relative density measurement during firing at 1500 °C were prepared by heat-treating the precursor at 1200 °C for 12 hours in an air atmosphere.

[0094] (Comparative Example 2) Figure 3 is a flowchart showing the method for producing composite oxide particles according to Comparative Example 2. The production of composite oxide particles will be described while referring to Figure 3.

[0095] The following materials were prepared as starting materials for the composite oxide particles. Ba(NO3)2 (manufactured by Kanto Chemical Co., Inc.) 0.1 mol ZrO(NO3)2·2H2O (manufactured by Kanto Chemical Co., Inc.) 0.08 mol Yb(NO3)3·xH2O (2 < x < 6, manufactured by High-Purity Chemical Research Institute Co., Ltd.) 0.02 mol

[0096] The above starting materials were added to distilled water to obtain a mixture, and the mixture was stirred (S31).

[0097] Next, 0.3 mol of citric acid monohydrate (manufactured by Kanto Chemical Co., Ltd.) and 0.3 mol of ethylenediaminetetraacetic acid (manufactured by Kanto Chemical Co., Ltd.) were added to the mixture (S32). Hereafter, "ethylenediaminetetraacetic acid" will be referred to as "EDTA".

[0098] Next, while measuring the pH of the mixture using a pH meter (manufactured by Horiba, Ltd.), ammonia water (28% by weight, manufactured by Kanto Chemical Co., Ltd.) was added to the mixture to adjust the pH of the mixture to 7 (S33).

[0099] Next, the mixture was stirred at a temperature of 90°C (S34).

[0100] After adjusting the pH of the mixture to 7, the temperature of the mixture was raised from 95°C to 240°C using a hot stirrer to evaporate the solvent (i.e., water) (S35). In this way, water was removed from the mixture and a solid was obtained.

[0101] The resulting solid was ground in a mortar and then degreased at a temperature of approximately 400°C (S36). In this way, a powder was obtained.

[0102] The obtained powder was heat-treated at 1100°C for 12 hours or at 1200°C for 12 hours in an air atmosphere (S37).

[0103] As described above, BaZr 0.8 Yb 0.2 O 3-δ A composite oxide powder was prepared (where δ is the oxygen deficiency, 0 ≤ δ < 1.0).

[0104] Similar to Comparative Example 1, composite oxide particles prepared by heat treatment at 1100°C for 12 hours in an air atmosphere were used for crystal structure analysis of the particles. Furthermore, composite oxide particles prepared by heat treatment at 1200°C for 12 hours in an air atmosphere were used for particle size analysis and relative density measurement during firing at 1500°C.

[0105] (Comparative Example 3) In Comparative Example 3, composite oxide particles were prepared in the same manner as in Example 1, except that the starting materials for the composite oxide particles were changed to the following materials.

[0106] Ca(NO3)2·4H2O (manufactured by Kanto Chemical Co., Ltd.) 1.66 × 10 -2 mol ZrO(Cl)2·8H2O (manufactured by Kanto Chemical Co., Ltd.) 1.28 × 10 -2 mol Yb(Cl)3·6H2O (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) 3.77×10 -3 mol

[0107] (Comparative Example 4) In Comparative Example 4, composite oxide particles were prepared in the same manner as in Example 1, except that the starting material for the composite oxide particles was changed to the following material.

[0108] Sr(NO3)2 (manufactured by Kanto Chemical Co., Ltd.) 1.66 × 10 -2 mol ZrO(Cl)2·8H2O (manufactured by Kanto Chemical Co., Ltd.) 1.28 × 10 -2 mol Yb(Cl)3·6H2O (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) 3.77×10 -3 mol

[0109] [evaluation] The composite oxide particles obtained in the examples and comparative examples were subjected to crystal structure analysis, particle size analysis, and relative density measurement at 1500°C using the methods described below. However, for the composite oxide particles obtained in Comparative Examples 3 and 4, only the crystal structure analysis of the particles was evaluated.

[0110] (Crystal structure analysis of composite oxide particles) The crystal structure of the composite oxide particles was analyzed by XRD. The instrument used was SmartLab (manufactured by Rigaku Corporation). Cu-Kα rays were used as the X-ray source, and the composite oxide particles were analyzed at a tube voltage of 30kV and a tube current of 20mA. Figure 4 is a graph showing the XRD structural analysis results of the composite oxide particles of Examples 1 to 7 and Comparative Examples 1 to 4. Based on the XRD patterns shown in Figure 4, the results of single-phase formation by heat treatment at 1100°C are shown in Table 1. In Table 1, "A" indicates single-phase formation, and "B" indicates that it was not single-phase.

[0111] (Particle size analysis of composite oxide particles) The average particle size of the composite oxide particles was analyzed using SEM images of the composite oxide particles. The SEM used for the analysis was a JSM7900F (manufactured by JEOL Ltd.). The SEM analysis was performed under an acceleration voltage of 2kV.

[0112] Figure 5A shows the composite oxide particles BaZr according to Example 1. 0.8 Yb 0.2 O 3-δ Figure 5B shows an SEM image of the composite oxide particles BaZr obtained using the SEM image shown in Figure 5A, according to Example 1. 0.8 Yb 0.2 O 3-δ This graph shows the particle size analysis results. The particle size analysis results shown in Figure 5B are a volume-based particle size distribution created based on particle sizes obtained by analyzing more than 100 arbitrary particles using the SEM image shown in Figure 5A with the image analysis software ImageJ. The 50% diameter obtained using this particle size distribution was taken as the average particle size. Table 1 shows the average particle size.

[0113] Figure 6A shows the composite oxide particles BaZr according to Example 2. 0.85 Yb 0.15 O 3-δFigure 6B shows an SEM image of the composite oxide particles BaZr obtained using the SEM image shown in Figure 6A, according to Example 2. 0.85 Yb 0.15 O 3-δ This graph shows the particle size analysis results. The average particle size of the composite oxide particles in Example 2 was determined using the same method as for the composite oxide particles in Example 1.

[0114] Figure 7A shows the composite oxide particles BaZr according to Example 3. 0.9 Yb 0.1 O 3-δ Figure 7B shows an SEM image of the composite oxide particles BaZr obtained using the SEM image shown in Figure 7A, according to Example 3. 0.9 Yb 0.1 O 3-δ This graph shows the particle size analysis results. The average particle size of the composite oxide particles in Example 3 was determined using the same method as for the composite oxide particles in Example 1.

[0115] Figure 8A shows the composite oxide particles BaZr according to Example 4. 0.8 In 0.2 O 3-δ Figure 8B shows an SEM image of the composite oxide particles BaZr obtained using the SEM image shown in Figure 8A, according to Example 4. 0.8 In 0.2 O 3-δ This graph shows the particle size analysis results. The average particle size of the composite oxide particles in Example 4 was determined using the same method as for the composite oxide particles in Example 1.

[0116] Figure 9A shows the composite oxide particles BaZr according to Example 5. 0.8 Gd 0.2 O 3-δ Figure 9B shows an SEM image of the composite oxide particles BaZr obtained using the SEM image shown in Figure 9A, according to Example 5. 0.8 Gd 0.2 O 3-δ This graph shows the particle size analysis results. The average particle size of the composite oxide particles in Example 5 was determined using the same method as for the composite oxide particles in Example 1.

[0117] Figure 10A shows the SEM image of the composite oxide particles BaHf 0.8 Yb 0.2 O 3-δ according to Example 6. Figure 10B is a graph showing the particle size analysis result of the composite oxide particles BaHf 0.8 Yb 0.2 O 3-δ obtained using the SEM image shown in Figure 10A, according to Example 6. The average particle size of the composite oxide particles of Example 6 was determined in the same manner as the composite oxide particles of Example 1.

[0118] Figure 11A shows the SEM image of the composite oxide particles BaZr 0.8 Sc 0.2 O 3-δ according to Example 7. Figure 11B is a graph showing the particle size analysis result of the composite oxide particles BaZr 0.8 Sc 0.2 O 3-δ obtained using the SEM image shown in Figure 11A, according to Example 7. The average particle size of the composite oxide particles of Example 7 was determined in the same manner as the composite oxide particles of Example 1.

[0119] Figure 12A shows the SEM image of the composite oxide particles BaZr 0.8 Yb 0.2 O 3-δ according to Comparative Example 1. Figure 12B is a graph showing the particle size analysis result of the composite oxide particles BaZr 0.8 Yb 0.2 O 3-δ obtained using the SEM image shown in Figure 12A, according to Comparative Example 1. The average particle size of the composite oxide particles of Comparative Example 1 was determined in the same manner as the composite oxide particles of Example 1.

[0120] Figure 13A shows the SEM image of the composite oxide particles BaZr 0.8 Yb 0.2 O 3-δ according to Comparative Example 2. Figure 13B is a graph showing the particle size analysis result of the composite oxide particles BaZr 0.8 Yb 0.2 O 3-δThis graph shows the particle size analysis results. The average particle size of the composite oxide particles of Comparative Example 1 was determined using the same method as for the composite oxide particles of Example 1.

[0121] (Relative density measurement during firing at 1500°C) Regarding the measurement of relative density during firing at 1500°C, we will first explain the pellet preparation process.

[0122] 3.0 g of composite oxide particles were transferred to a plastic container along with zirconia balls. Then, 15 g of ethanol (manufactured by Kanto Chemical Co., Ltd.) was added to the plastic container. A mixture was thus obtained. Next, the mixture was ground in a ball mill for 12 hours. After grinding with the ball mill, the mixture was dried using a hot stirrer to remove the ethanol. A powder was thus obtained.

[0123] Next, the obtained powder was pressed into a cylindrical shape at a press pressure of 50 MPa using a hydraulic pump (manufactured by NPA Systems Co., Ltd.) and a powder molding die with a diameter of 11 mm, and then further molded at a press pressure of 200 MPa using a cold isohydraulic press (manufactured by NPA Systems Co., Ltd.).

[0124] The resulting circular molded material was fired at 1500°C for 12 hours in an air atmosphere. This yielded sintered pellets.

[0125] The volume and mass of the obtained sintered pellets were measured, and the relative density was calculated using the following formula. The results are shown in Table 1. Relative density (%) = {(pellet mass) ÷ (pellet volume) ÷ (theoretical density)} × 100

[0126] (Evaluation results of composite oxide particles) Based on the results shown in Table 1, the composite oxide particles produced in the examples and comparative examples are described below.

[0127] First, the composite oxide particles of Example 1, prepared using TMAHC and TMAH as additives, are compared with the composite oxide particles of Comparative Example 1, prepared using ammonium carbonate and ammonia as additives, and the composite oxide particles of Comparative Example 2, prepared using citric acid and EDTA as additives.

[0128] The average particle size of the composite oxide particles was 57 nm in Example 1, 143 nm in Comparative Example 1, and 167 nm in Comparative Example 2, with Example 1 showing the smallest average particle size.

[0129] As shown in Table 1, in Example 1, the composite oxide particles became single-phase after heat treatment at 1100°C. However, the composite oxide particles in Comparative Examples 1 and 2 did not become single-phase at 1100°C, and single-phase formation was confirmed only after heat treatment at 1200°C. As described above, for Comparative Examples 1 and 2, the average particle diameter was determined for the composite oxide particles obtained by heat treatment at 1200°C, i.e., the single-phase composite oxide particles. It is assumed that the average particle diameter increased for the composite oxide particles in Comparative Examples 1 and 2 because the heat treatment temperature was increased in order to achieve single-phase formation.

[0130] Furthermore, the relative density at firing at 1500°C was 98% for the composite oxide particles of Example 1, 83% for the composite oxide particles of Comparative Example 1, and 87% for the composite oxide particles of Comparative Example 2, with Example 1 showing the highest relative density.

[0131] From the above, it was confirmed that composite oxide particles with an average particle diameter of less than 100 nm can be densified at a low temperature of 1500°C.

[0132] Next, the composition will be explained using Examples 1 to 7, Comparative Example 3, and Comparative Example 4.

[0133] Examples 1 to 7 used Ba at the A site of the perovskite, and Zr or Hf and Yb, In, Gd, or Sc at the B site. Comparative Examples 3 and 4 used Ca or Sr at the A site of the perovskite, and Zr and Yb at the B site. As can be seen from the XRD results in Figure 4, no impurity peaks were detected in the composite oxide particles of Examples 1 to 7, and all became single-phase after heat treatment at 1100°C, whereas impurity peaks remained in the composite oxide particles of Comparative Examples 3 and 4. From this, it can be seen that by using Ba at the A site, single-phase composite oxide particles can be synthesized at a lower temperature.

[0134] Examples 1 to 3 are BaZrYbO 3-δ The materials had different composition ratios represented by (δ being the amount of oxygen deficiency, 0 ≤ δ < 1.0), and their particle sizes were 57 nm, 50 nm, and 54 nm, respectively. The relative densities after heat treatment at 1500°C were 98% for Example 1, 98% for Example 2, and 95% for Example 3, all showing high relative densities exceeding 90%. From the above, it was concluded that regardless of the composition ratio, BaZrYbO 3-δ (δ is the amount of oxygen deficiency, 0 ≤ δ < 1.0) It can be seen that nanoparticles with a particle size of less than 100 nm can be densified at lower temperatures.

[0135] Examples 4 and 5 used materials with metal element M being In and Gd, respectively, and had average particle sizes of 70 nm and 66 nm. The relative density at firing at 1500°C was 97% for Example 4 and 96% for Example 5, both showing high relative densities exceeding 90%. From the above, it can be seen that even when using metal element M being In and Gd, nanoparticles with an average particle size of less than 100 nm can be densified at lower temperatures.

[0136] Example 6 is BaHfYbO 3-δ Example 7 is BaZrScO 3-δThe materials had different composition ratios represented by (δ being the amount of oxygen deficiency, 0 ≤ δ < 1.0), and their average particle sizes were 52 nm and 54 nm, respectively. Furthermore, the composite oxide particles of Example 6 and Comparative Example 7 had an average particle size similar to that of the composite oxide particles of the other examples, and were also single-phase, as in the other examples. Therefore, it is presumed that, similar to the other examples, a dense body with a relative density of 90% or more will be obtained when fired at 1500°C.

[0137] (Optimal heat treatment temperature for obtaining composite oxide particles) Figure 14 is a graph showing the results of XRD structural analysis measurements when the heat treatment temperature of the precursor for obtaining composite oxide particles was changed in Example 1. The heat treatment temperature for obtaining composite oxide particles will be explained based on Figure 14. Figure 14 shows the BaZr of Example 1. 0.8 Yb 0.2 O 3-δ The XRD results shown are for the composition when the precursor was heat-treated at 800°C to 1200°C. At 800°C, an impurity peak was observed, indicating that it is insufficient as a crystallization temperature. However, at heat treatment temperatures of 900°C to 1200°C, it can be seen that it is a single phase. From this, it can be seen that the heat treatment temperature of the precursor to obtain composite oxide particles is preferably 900°C or higher, and even more preferably 1000°C or higher. Furthermore, to more reliably obtain composite oxide particles with an average particle diameter of less than 100 nm, the heat treatment temperature should preferably be 1100°C or lower.

[0138] (Appropriate ratio of TMAHC to TMAH) Figure 15 is a graph showing the composition of the product when the molar ratio of TMAHC to TMAH is changed in Example 1, where TMAHC and TMAH are additives used to produce composite oxide particles. Based on Figure 15, the appropriate ratio of TMAHC to TMAH when synthesizing the precursor of composite oxide particles will be explained.

[0139] The graph in Figure 15 shows the BaZr of Example 1. 0.8 Yb 0.2 O 3-δThis plots the composition of the product synthesized by varying the ratio (molar ratio) of TMAHC to TMAH in the given composition. From this, the molar ratio of TMAHC to TMAH n TMAHC / n TMAH For n, we have been able to synthesize a composition close to the target between 0.7 and 2.0. On the other hand, n TMAHC / n TMAH When n is less than 0.7, it can be seen that the composition deviates from the target. TMAHC / n TMAH is 0.7≦n TMAHC / n TMAH ≤2.0 is desirable. From the results shown in Figure 15, in order to obtain a composition closer to the target composition, n TMAHC / n TMAH A value of 0.75 or higher is more desirable, while n TMAHC / n TMAH A value of 1.5 or less is preferable.

[0140] [Table 1] [Industrial applicability]

[0141] The composite oxide particles of this disclosure can be used as proton conductors and, for example, in electrolyte membranes and electrodes of proton-conducting ceramic fuel cells.

Claims

1. A composite oxide particle comprising a proton conductor containing Ba, at least one selected from the group consisting of Zr and Hf, a trivalent metal element M, and O, and not containing nickel oxide, The aforementioned metal element M is at least one selected from the group consisting of Sc, In, Yb, Y, and Gd. The average particle size of the composite oxide particles is less than 100 nm. Composite oxide particles.

2. The average particle diameter is 70 nm or less. The composite oxide particles according to claim 1.

3. The present invention provides a method for obtaining a dense electrolyte film by firing an electrolyte material containing composite oxide particles as described in claim 1 or 2 at a temperature exceeding 1100°C and not exceeding 1500°C. A method for manufacturing an electrolyte membrane.

4. A conductive air electrode material, The composite oxide particles according to claim 1 or 2, A composite electrode, including one.

5. To obtain a precursor of composite oxide particles from an aqueous solution containing Ba ions, at least one ion selected from the group consisting of Zr ions and Hf ions, M ions which are trivalent metal element ions, tetramethylammonium bicarbonate, and tetramethylammonium hydroxide, The process involves heat-treating the precursor to obtain the composite oxide particles, A method for producing composite oxide particles, including

6. The M ion is at least one selected from the group consisting of Sc ions, In ions, Yb ions, Y ions, and Gd ions. A method for producing composite oxide particles according to claim 5.

7. In the aqueous solution, the molar ratio of tetramethylammonium bicarbonate to tetramethylammonium hydroxide is 0.7 or higher. A method for producing composite oxide particles according to claim 5 or 6.

8. The precursor is heat-treated at a temperature of 900°C or higher and 1100°C or lower. A method for producing composite oxide particles according to any one of claims 5 to 7.

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