Method for producing dispersion, method for producing metal oxide particles, and method for producing ceramic sheet

Abstract

The method for producing the dispersion liquid of the present application includes: a first stirring step of stirring metal oxide particles modified with an organic acid in a first solution containing at least one of an inorganic acid and acetic acid and a solvent; a cleaning and recovering step of cleaning and recovering the metal oxide particles stirred in the first stirring step; and a second stirring step of stirring the metal oxide particles recovered in the cleaning and recovering step in a second solution containing at least one of an amine and ammonia and a polar solvent.

Description

Technical Field

[0001] This invention relates to methods for manufacturing dispersions, methods for manufacturing metal oxide particles, and methods for manufacturing ceramic sheets. Background Technology

[0002] In recent years, with the increasing demand for improved performance of electronic devices, there has been a need to control the size and shape of metal oxide particles used as their constituent materials.

[0003] As a method for manufacturing such metal oxide particles, Patent Document 1 discloses a method for manufacturing barium titanate nanocrystals, characterized in that a solution is obtained by mixing an aqueous solution of barium hydroxide, an aqueous solution of a water-soluble titanium complex, an aqueous solution of sodium hydroxide, an amine compound, and an organic carboxylic acid, and the solution is heated for synthesis, and in the above solution, the number of moles of the amine compound relative to 1 mole of barium is 2 to 16 and the number of moles of the organic carboxylic acid relative to 1 mole of barium is 2 to 8.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent No. 5637389 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] According to the method for manufacturing barium titanate nanocrystals described in Patent Document 1, barium titanate nanocrystals with monodispersity, fine size, and a controlled hexagonal structure can be synthesized. Furthermore, because the barium titanate nanocrystals manufactured in this way have uniform size and shape, they can be stacked to form structures in two-dimensional or three-dimensional arrangements, thus holding promise for applications in devices with novel performance and functions. Additionally, because the barium titanate nanocrystals manufactured in this way are fine-grained, they are also considered capable of addressing the miniaturization of electronic devices. Moreover, the barium titanate nanocrystals manufactured in this way exhibit a tendency to self-align.

[0009] The barium titanate nanocrystals described in Patent Document 1 are, for example, used in the dielectric layer of multilayer ceramic capacitors. Such dielectric layers are typically manufactured by forming a dispersion of barium titanate nanocrystals on a substrate. Therefore, when manufacturing a dielectric layer using the barium titanate nanocrystals described in Patent Document 1, it is important to use a dispersion with excellent dispersibility of the barium titanate nanocrystals in order to utilize the aforementioned characteristics of the barium titanate nanocrystals.

[0010] According to the method for manufacturing barium titanate nanocrystals described in Patent Document 1, organic carboxylic acids with long carbon chains, such as oleic acid, are coordinated to the (100) facets of the nanocrystals during nanocrystal synthesis, inhibiting crystal growth on the (100) facets and thus controlling the size and shape of the barium titanate nanocrystals. In other words, the barium titanate nanocrystals described in Patent Document 1 are modified with organic carboxylic acids. Patent Document 1 describes dispersing the obtained barium titanate nanocrystals in toluene, then dropping this solution onto a silicon substrate and drying it to remove the solvent, which is the only way to produce a dense array. Thus, when using the barium titanate nanocrystals described in Patent Document 1 to manufacture a dispersion, the barium titanate nanocrystals are dispersed in a non-polar solvent such as toluene.

[0011] In contrast, the inventors investigated the dispersion of organic acid-modified metal oxide particles, such as the barium titanate nanocrystals described in Patent Document 1, in a polar solvent. The inventors specifically considered that if the organic acid-modified metal oxide particles could be dispersed in water, a polar solvent, then when forming this dispersion on a substrate, the surface tension of water could be utilized to draw the metal oxide particles closer together, thereby enabling them to be densely packed, more specifically, arranged in a two-dimensional or three-dimensional configuration on the substrate at low cost.

[0012] However, organic acid-modified metal oxide particles exhibit hydrophobicity, thus they are easily dispersed in nonpolar solvents such as toluene, but not in polar solvents such as water. Therefore, it can be seen that simply dispersing organic acid-modified metal oxide particles in polar solvents cannot produce a dispersion with excellent dispersibility.

[0013] Furthermore, when composite metal oxide particles such as barium titanate are used in electronic devices and electronic components, the characteristics of these devices are more easily improved after element substitution, compared to using composite metal oxide particles in their simple state.

[0014] However, the barium titanate nanocrystals described in Patent Document 1 are typically manufactured with a simple composition, making it difficult to perform elemental substitutions. Therefore, even when using the barium titanate nanocrystals described in Patent Document 1 in electronic devices and electronic components, it is difficult to improve the characteristics of these devices and components.

[0015] This invention addresses the aforementioned problems and aims to provide a method for manufacturing a dispersion that, even when using organic acid-modified metal oxide particles as starting materials, can produce a dispersion with excellent dispersibility of metal oxide particles in polar solvents. Furthermore, this invention aims to provide a method for manufacturing metal oxide particles that can improve the properties of electronic devices, electronic components, etc. Additionally, this invention aims to provide a method for manufacturing ceramic sheets using the above-described dispersion manufacturing method.

[0016] Problem-solving methods

[0017] The method for manufacturing the dispersion of the present invention is characterized by comprising: a first stirring step in which metal oxide particles modified by organic acid are placed in a first solution containing at least one of inorganic acid and acetic acid and a solvent and stirred; a washing and recovery step in which the metal oxide particles stirred in the first stirring step are washed and then recovered; and a second stirring step in which the metal oxide particles recovered in the washing and recovery step are placed in a second solution containing at least one of amine and ammonia and a polar solvent and stirred.

[0018] The method for manufacturing metal oxide particles of the present invention is characterized by comprising: a dispersion manufacturing step, wherein a dispersion is manufactured by the dispersion manufacturing method of the present invention; and a metal ion adsorption step, wherein at least one metal ionized ion selected from the group consisting of Mg, Ca, Sr, Mn, Fe, Co, Ni, Cu, Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Gd, Tb, Dy, Ho, Eu, Tm, Yb and Lu is adsorbed onto the interface of the metal oxide particles contained in the dispersion.

[0019] The method for manufacturing ceramic sheets of the present invention is characterized by comprising: a dispersion manufacturing step, wherein a dispersion is manufactured by the dispersion manufacturing method of the present invention; and a forming step, wherein the dispersion is formed into a sheet shape on a substrate.

[0020] The effects of the invention

[0021] According to the present invention, a method for manufacturing a dispersion can be provided, which can produce a dispersion with excellent dispersibility of metal oxide particles in polar solvents even when using metal oxide particles modified with organic acids as starting materials. Furthermore, according to the present invention, a method for manufacturing metal oxide particles can be provided, which can produce metal oxide particles capable of improving the properties of electronic devices, electronic components, etc. In addition, according to the present invention, a method for manufacturing ceramic sheets using the above-described dispersion manufacturing method can be provided. Attached Figure Description

[0022] Figure 1 This is a graph showing the measurement results of particle size distribution in the dispersion of Example 1-1.

[0023] Figure 2 This is a graph showing the measurement results of particle size distribution in the dispersion of Example 2-1.

[0024] Figure 3 This is a graph showing the measurement results of particle size distribution in the dispersion of Example 3-1.

[0025] Figure 4 This is a graph showing the measurement results of particle size distribution in the dispersion of Example 4-1.

[0026] Figure 5 This is a schematic diagram showing the planar structure of the ceramic sheet in Examples 1-2.

[0027] Figure 6 This is a schematic diagram showing the cross-sectional structure of the ceramic sheet in Examples 1-2.

[0028] Figure 7 This is a schematic diagram showing the planar structure of the ceramic sheet in Example 2-2.

[0029] Figure 8 This is a schematic diagram showing the cross-sectional structure of the ceramic sheet in Example 2-2.

[0030] Figure 9 The graph shows the measurement results of the temperature characteristics of the relative permittivity and dielectric loss tangent in the ceramic sintered layers of Examples 1-3.

[0031] Figure 10 This is a graph showing the measurement results of the temperature characteristics of the relative permittivity and dielectric loss tangent in the ceramic sintered layers of Examples 2-3.

[0032] Figure 11 This is a STEM image showing the cross-section of the ceramic sheet in Examples 1-4.

[0033] Figure 12 It means Figure 11 The elemental mapping of the distribution of Ti in the STEM image shown.

[0034] Figure 13 It means Figure 11 The elemental mapping of the distribution of Ba in the STEM image shown.

[0035] Figure 14 It means Figure 11 The elemental mapping of the distribution of Y in the STEM image shown.

[0036] Figure 15This is a schematic diagram showing the manufacturing process of the ceramic sheets in Examples 1-4.

[0037] Figure 16 This is a STEM image showing the cross-section of the ceramic sheet in Examples 2-4.

[0038] Figure 17 It means Figure 16 The elemental mapping of the distribution of Ti in the STEM image shown.

[0039] Figure 18 It means Figure 16 The elemental mapping of the distribution of Ba in the STEM image shown.

[0040] Figure 19 It means Figure 16 The elemental mapping of the distribution of Mn in the STEM image shown.

[0041] Figure 20 This is a schematic diagram showing the manufacturing process of the ceramic sheets in Examples 2-4.

[0042] Figure 21 This is a graph showing the measurement results of the temperature characteristics of the relative permittivity in the ceramic sintered layers of Examples 1-5.

[0043] Figure 22 This is a graph showing the measurement results of the temperature characteristics of the relative permittivity in the ceramic sintered layers of Examples 2-5. Detailed Implementation

[0044] The following describes the manufacturing methods of the dispersion, the metal oxide particles, and the ceramic sheets of the present invention. Furthermore, the present invention is not limited to the following configurations and can be adapted without departing from the spirit of the invention. Additionally, combinations of multiple preferred configurations described below also fall under the scope of the present invention.

[0045] [Method for preparing dispersion]

[0046] The method for manufacturing the dispersion of the present invention is characterized by comprising the following steps: a first stirring step in which metal oxide particles modified by organic acid are placed in a first solution containing at least one of inorganic acid and acetic acid and a solvent and stirred; a washing and recovery step in which the metal oxide particles stirred in the first stirring step are washed and then recovered; and a second stirring step in which the metal oxide particles recovered in the washing and recovery step are placed in a second solution containing at least one of amine and ammonia and a polar solvent and stirred.

[0047] <First mixing process>

[0048] Metal oxide particles modified with organic acids are placed in a first solution containing at least one of an inorganic acid and acetic acid, and a solvent, and stirred. Thereby, at least one of the inorganic acid and acetic acid in the first solution cleaves the organic acid modified on the metal oxide particles, thus protonating the metal oxide particles.

[0049] Metal oxide particles modified with organic acids, such as barium titanate nanocrystals as described in Patent Document 1, exhibit monodispersity, meaning they are uniform in size and shape. Therefore, as a starting material for manufacturing dispersions, by using metal oxide particles modified with organic acids, as described later, it is possible to produce dispersions containing metal oxide particles of uniform size and shape. Thus, as described later, in the manufacture of ceramic sheets, by using such dispersions, it is possible to densely, more specifically, to have a two-dimensional or three-dimensional arrangement and accumulate the metal oxide particles on a substrate.

[0050] The organic acid is preferably at least one selected from the group consisting of acetic acid, citric acid, oxalic acid, propionic acid, oleic acid, linoleic acid, and linolenic acid.

[0051] The metal oxide constituting the metal oxide particles is preferably at least one selected from the group consisting of barium titanate, strontium titanate, zirconium titanate, zirconium oxide, hafnium oxide, cerium oxide and titanium oxide.

[0052] The shapes of metal oxide particles can include, for example, polyhedral and spherical shapes. For instance, barium titanate and strontium titanate particles are hexahedral cuboids, cerium oxide particles are octahedral, and titanium oxide particles are spherical. As will be discussed later, from the viewpoint of densifying the ceramic sheet by densely filling it with metal oxide particles, cuboid shapes are preferred in the manufacture of ceramic sheets. Here, cuboid shapes include not only perfect cuboids but also imperfect cuboids with chamfered vertices. Of course, cuboid shapes also include cubic shapes. Furthermore, spherical shapes include not only perfect spheres but also imperfect spheres.

[0053] The particle size of the metal oxide particles is preferably greater than 15 nm and less than 100 nm. If the particle size of the metal oxide particles is large, dispersion becomes difficult. According to the method for manufacturing the dispersion of the present invention, a dispersion with excellent dispersibility of metal oxide particles in a polar solvent can be produced. When the particle size of the metal oxide particles is less than 100 nm, the metal oxide particles are less likely to fall due to their own weight in the subsequently obtained dispersion, thus enabling the production of a dispersion with excellent dispersibility of metal oxide particles.

[0054] The particle size of a metal oxide particle, when the particle is polyhedral, refers to the length of its longest side; when the particle is spherical, it refers to its diameter. The particle size of a metal oxide particle is determined by the number-average particle size measured by a dynamic light scattering measurement device.

[0055] The first solution comprises at least one of an inorganic acid and acetic acid, and a solvent. More specifically, the first solution may comprise an inorganic acid and a solvent, acetic acid and a solvent, or an inorganic acid, acetic acid, and a solvent.

[0056] The inorganic acid is preferably at least one selected from the group consisting of hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, and boric acid. Nitric acid is more preferably used as the inorganic acid. When nitric acid is used as the inorganic acid, it is less corrosive than hydrochloric acid, and therefore is less likely to cause corrosion of metal oxide particles during stirring.

[0057] The solvent contained in the first solution is preferably a polar solvent. Examples of polar solvents included in the first solution include water and ethanol. Among these, water is preferred. When the first solution contains water as a polar solvent, the first solution may also contain at least one of an inorganic acid and acetic acid as an aqueous solution.

[0058] In this specification, polar solvent means a solvent with a relative permittivity greater than 6.0.

[0059] As long as at least one of the inorganic acid and acetic acid contained in the first solution satisfies the condition that it can cleave the organic acid modified on the metal oxide particles and protonate the metal oxide particles, the concentration of at least one of the inorganic acid and acetic acid contained in the first solution, the stirring time, and other stirring conditions are not particularly limited and can be appropriately adjusted according to the amount of metal oxide particles put into the first solution.

[0060] <Cleaning and Recycling Process>

[0061] The metal oxide particles stirred in the first stirring process are then washed and recycled.

[0062] This process is performed, for example, as follows: First, the stirred liquid obtained in the first stirring step is centrifuged to separate the metal oxide particles from the first solution. Next, after discarding the first solution and recovering the residual metal oxide particles, the metal oxide particles are placed in a washing solution such as water and stirred to wash the metal oxide particles. Then, the resulting stirred liquid is centrifuged to separate the metal oxide particles from the washing solution. Afterward, the washing solution is discarded, and the remaining metal oxide particles are recovered. The recovered metal oxide particles are thus protonated.

[0063] <Second mixing process>

[0064] The metal oxide particles recovered in the washing and recycling process are placed in a second solution containing at least one of an amine and ammonia, and a polar solvent, and stirred. Thereby, at least one of the amine and ammonia contained in the second solution adsorbs onto the surface of the protonated metal oxide particles, thereby hydrophilizing the metal oxide particles. As a result, the hydrophilized metal oxide particles are easily dispersed in the polar solvent contained in the second solution.

[0065] The second solution contains at least one of an amine and ammonia, and a polar solvent. More specifically, the second solution may contain an amine and a polar solvent, or it may contain ammonia and a polar solvent, or it may contain an amine, ammonia, and a polar solvent.

[0066] The amine is preferably at least one selected from the group consisting of tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, monoethanolamine, diethanolamine, triethanolamine, monoethylamine, diethylamine, and triethylamine. From the viewpoint of the working environment, tetrabutylammonium hydroxide is more preferably preferred.

[0067] Examples of polar solvents included in the second solution include water and ethanol.

[0068] The polar solvent contained in the second solution is preferably water. When the second solution contains water as a polar solvent, this process can obtain a dispersion of metal oxide particles dispersed in water. Water also has a relatively high surface tension in liquids. Therefore, as described later in the manufacture of ceramic sheets, if a dispersion of metal oxide particles in water is used, the metal oxide particles are drawn closer together under the surface tension of water, easily forming a two-dimensional or three-dimensional arrangement and accumulating on the substrate. Therefore, by dispersing metal oxide particles in water with high surface tension, as described later in the manufacture of ceramic sheets, it is possible to accumulate large-diameter metal oxide particles or accumulate metal oxide particles over a large area at low cost.

[0069] Even when the second solution contains ethanol or other polar solvents besides water, the metal oxide particles are easily dispersed in the polar solvent by means of at least one of the amines and ammonia contained in the second solution.

[0070] When the second solution contains water as a polar solvent, the second solution may also contain at least one of the amine and ammonia as an aqueous solution.

[0071] As long as the conditions are such that at least one of the amine and ammonia contained in the second solution is adsorbed on the surface of the protonated metal oxide particles, making the metal oxide particles hydrophilic, then the concentration of at least one of the amine and ammonia contained in the second solution, the stirring time, and other stirring conditions are not particularly limited, and can be appropriately adjusted according to the amount of metal oxide particles added to the second solution.

[0072] Based on the above, according to the method for manufacturing dispersion of the present invention, even when using metal oxide particles modified with organic acids as starting materials, it is possible to manufacture dispersions with excellent dispersibility of metal oxide particles in polar solvents.

[0073] [Methods for manufacturing metal oxide particles]

[0074] The method for manufacturing metal oxide particles of the present invention is characterized by comprising: a dispersion manufacturing step, wherein a dispersion is manufactured by the dispersion manufacturing method of the present invention; and a metal ion adsorption step, wherein at least one metal ionized ion selected from the group consisting of Mg, Ca, Sr, Mn, Fe, Co, Ni, Cu, Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Gd, Tb, Dy, Ho, Eu, Tm, Yb and Lu is adsorbed onto the interface of the metal oxide particles contained in the dispersion.

[0075] <Dispersion Manufacturing Process>

[0076] A dispersion is manufactured using the dispersion manufacturing method of the present invention described above.

[0077] <Metal Ion Adsorption Process>

[0078] The interface of the metal oxide particles contained in the dispersion is used to adsorb at least one ionized metal ion selected from the group consisting of Mg, Ca, Sr, Mn, Fe, Co, Ni, Cu, Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Gd, Tb, Dy, Ho, Eu, Tm, Yb, and Lu. Thus, at the interface of the metal oxide particles contained in the dispersion, at least one of the ionized amine and ammonia that modifies the metal oxide particles exchanges with the metal ion, a process known as cation exchange. Because the size of the metal ion is smaller than that of the ionized amine and ammonia, the metal oxide particles can be densely packed through the aforementioned cation exchange.

[0079] In this process, at least one metal ionized metal ion selected from the group consisting of Mg, Ca, Sr, Mn, Fe, Co, Ni, Cu, Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Gd, Tb, Dy, Ho, Eu, Tm, Yb and Lu can be used as the metal ion.

[0080] In this process, for example, by imparting metal salts to metal oxide particles as follows, metal ions can be adsorbed at the interface of the metal oxide particles.

[0081] In this process, the metal oxide particles contained in the dispersion can also be placed into an aqueous solution of metal salt containing metal ions dissolved in water.

[0082] Alternatively, in this process, a metal salt containing metal ions can be added to the dispersion.

[0083] Alternatively, in this process, the dispersion can be mixed with an aqueous solution of a metal salt containing metal ions dissolved in water.

[0084] The metal salt is preferably at least one selected from the group consisting of chloride salts, acetates, nitrates, sulfates, phosphates, and borates. More preferably, the metal salt is at least one of chloride salts and nitrates.

[0085] If metal oxide particles manufactured by the above processes are used to manufacture ceramic sheets as described later, a denser ceramic sheet can be obtained. Furthermore, the internal structure of the ceramic sheet can be made, for example, a core-shell structure where metal ions exist as the shell of the metal oxide particles. Therefore, according to the method for manufacturing metal oxide particles of the present invention, the interface of the metal oxide particles can be controlled, and thus the magnetic structure can be controlled. For example, if barium titanate particles, as metal oxide particles, are made into a core-shell structure through cation exchange based on the above method and then used as the dielectric layer of a multilayer ceramic capacitor, a multilayer ceramic capacitor with small temperature variation in the relative permittivity of the dielectric layer and excellent reliability can be achieved.

[0086] Based on the above, the method for manufacturing metal oxide particles according to the present invention can manufacture metal oxide particles that can improve the properties of electronic devices, electronic components, etc.

[0087] [Methods for manufacturing ceramic tiles]

[0088] The method for manufacturing ceramic sheets of the present invention is characterized by comprising: a dispersion manufacturing step, wherein a dispersion is manufactured by the dispersion manufacturing method of the present invention; and a forming step, wherein the dispersion is formed into a sheet shape on a substrate.

[0089] <Dispersion Manufacturing Process>

[0090] A dispersion is manufactured using the dispersion manufacturing method of the present invention described above.

[0091] <Forming Process>

[0092] A dispersion of liquid is formed into sheets on a substrate. This allows for the fabrication of ceramic sheets on the substrate.

[0093] This process is performed, for example, as follows: First, the dispersion is applied to the surface of the substrate using methods such as dip coating, slot coating, or gravure coating. Then, the dispersion film is dried to create a ceramic sheet on the substrate.

[0094] Based on the above, ceramic sheets can be manufactured using a dispersion of metal oxide particles in a polar solvent. Because the metal oxide particles, with uniform size and shape, are dispersed in the polar solvent, using such a dispersion during ceramic sheet manufacturing allows the metal oxide particles to be densely packed, more specifically, arranged in a two-dimensional or three-dimensional manner, and deposited on the substrate. In particular, when the polar solvent in the dispersion is water, as mentioned above, the metal oxide particles are drawn closer together under the surface tension of water, easily accumulating in a two-dimensional or three-dimensional arrangement on the substrate.

[0095] Subsequently, if the ceramic sheet is sintered to sinter the metal oxide particles, a ceramic sintered layer can be obtained. Such a ceramic sintered layer can be used, for example, as the dielectric layer of a multilayer ceramic capacitor. If such a densified ceramic sheet is used to manufacture the dielectric layer of a multilayer ceramic capacitor, gaps that could become conductive paths are difficult to exist in the dielectric layer, thus preventing short circuits between the internal electrode layers of the multilayer ceramic capacitor via the dielectric layer.

[0096] <Metal Ion Adsorption Process>

[0097] The method for manufacturing ceramic sheets of the present invention may further include a metal ion adsorption step, in which the interface of the metal oxide particles contained in the sheet formed in the forming step adsorbs at least one metal ion selected from the group consisting of Mg, Ca, Sr, Mn, Fe, Co, Ni, Cu, Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Gd, Tb, Dy, Ho, Eu, Tm, Yb and Lu.

[0098] In this process, at the interface of the metal oxide particles contained in the sheet, at least one of the ionized amine and ammonia that modifies the metal oxide particles exchanges with metal ions, a process known as cation exchange. Because the size of the metal ions is smaller than that of the ionized amine and ammonia, the metal oxide particles can be densely arranged by performing the aforementioned cation exchange on them. In other words, this process can produce a dense ceramic sheet. Furthermore, the internal structure of the ceramic sheet can be made, for example, a core-shell structure in which metal ions exist as the shell of the metal oxide particles. Therefore, according to this process, the interface of the metal oxide particles can be controlled, and thus the magnetic structure can be controlled. For example, if barium titanate particles, which are metal oxide particles, are made into a core-shell structure by the aforementioned cation exchange on a sheet formed by the molding process, and then used as the dielectric layer of a multilayer ceramic capacitor, a multilayer ceramic capacitor with a small temperature change in the relative permittivity of the dielectric layer and excellent reliability can be achieved.

[0099] In this process, at least one metal ionized metal ion selected from the group consisting of Mg, Ca, Sr, Mn, Fe, Co, Ni, Cu, Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Gd, Tb, Dy, Ho, Eu, Tm, Yb and Lu can be used as the metal ion.

[0100] In this process, for example, by applying an aqueous solution of a metal salt to the sheet as follows, metal ions can be adsorbed at the interface of the metal oxide particles.

[0101] In this process, the sheet can also be placed in an aqueous solution of a metal salt containing metal ions dissolved in water.

[0102] Alternatively, in this process, an aqueous solution of a metal salt containing metal ions dissolved in water can be coated onto the sheet.

[0103] The metal salt is preferably at least one selected from the group consisting of chloride salts, acetates, nitrates, sulfates, phosphates, and borates. More preferably, the metal salt is at least one of chloride salts and nitrates.

[0104] Example

[0105] The following examples illustrate, more specifically disclosing the method for manufacturing the dispersion of the present invention and the method for manufacturing the ceramic sheet of the present invention. Furthermore, the present invention is not limited to these examples.

[0106] [Example 1-1]

[0107] The dispersion of Example 1-1 was prepared by the following method.

[0108] <First mixing process>

[0109] One g of cubic barium titanate particles, modified with oleic acid and with a particle size of 50 nm on each side, was placed in 30 mL of a 0.1 mol / L nitric acid aqueous solution and stirred for 24 hours. The nitric acid cleaved the oleic acid in the barium titanate particles, thus protonating them.

[0110] <Cleaning and Recycling Process>

[0111] First, the barium titanate particles are separated from the nitric acid aqueous solution by centrifugation of the stirred liquid obtained in the first stirring step. Next, the nitric acid aqueous solution is discarded, and the remaining barium titanate particles are recovered. These particles are then washed by stirring in water. The resulting stirred liquid is then centrifuged to separate the barium titanate particles from the water. The water is then discarded, and the remaining barium titanate particles are recovered. The recovered barium titanate particles are then protonated.

[0112] <Second mixing process>

[0113] The barium titanate particles recovered during the washing and recycling process were placed in 30 mL of a 0.2 mol / L tetrabutylammonium hydroxide aqueous solution and stirred for 24 hours. As a result, the tetrabutylammonium hydroxide was adsorbed onto the surface of the protonated barium titanate particles, making the barium titanate particles hydrophilic. Consequently, a white dispersion of barium titanate particles in water was obtained.

[0114] Based on the above, the dispersion of Example 1-1 was manufactured.

[0115] [Example 2-1]

[0116] The dispersion of Example 2-1 was prepared by the following method.

[0117] <First mixing process>

[0118] One g of cubic barium titanate particles, modified with oleic acid and with a particle size of 100 nm on each side, was placed in 30 mL of a 1 mol / L nitric acid aqueous solution and stirred for 1 hour. The nitric acid cleaved the oleic acid on the barium titanate particles, thus protonating them.

[0119] <Cleaning and Recycling Process>

[0120] First, the barium titanate particles and the nitric acid aqueous solution are separated by centrifugation of the stirred liquid obtained in the first stirring step. Next, the nitric acid aqueous solution is discarded, and the remaining barium titanate particles are recovered. These particles are then washed by stirring in water. The resulting stirred liquid is then centrifuged to separate the barium titanate particles and water. The water is then discarded, and the remaining barium titanate particles are recovered. The recovered barium titanate particles are then protonated.

[0121] <Second mixing process>

[0122] The barium titanate particles recovered during the washing and recycling process were placed in 30 mL of a 0.2 mol / L tetrabutylammonium hydroxide aqueous solution and stirred for 18 hours. As a result, the tetrabutylammonium hydroxide was adsorbed onto the surface of the protonated barium titanate particles, making the barium titanate particles hydrophilic. Consequently, a white dispersion of barium titanate particles in water was obtained.

[0123] Based on the above, the dispersion of Example 2-1 was manufactured.

[0124] [Example 3-1]

[0125] The dispersion of Example 3-1 was prepared using the following method.

[0126] <First mixing process>

[0127] One g of cubic strontium titanate particles, modified with propionic acid and with a diameter of 100 nm on each side, were placed in 30 mL of a 0.5 mol / L hydrochloric acid aqueous solution and stirred for 24 hours. This process cleaves the propionic acid on the strontium titanate particles with hydrochloric acid, thus protonating the particles.

[0128] <Cleaning and Recycling Process>

[0129] First, the strontium titanate particles and hydrochloric acid aqueous solution are separated by centrifugation of the stirred liquid obtained in the first stirring step. Next, the hydrochloric acid aqueous solution is discarded, and the remaining strontium titanate particles are recovered. These particles are then washed by stirring in water. The resulting stirred liquid is then centrifuged to separate the strontium titanate particles and water. The water is then discarded, and the remaining strontium titanate particles are recovered. The recovered strontium titanate particles are then protonated.

[0130] <Second mixing process>

[0131] The strontium titanate particles recovered during the washing and recycling process were placed in 30 mL of a 0.5 mol / L triethanolamine aqueous solution and stirred for 24 hours. As a result, triethanolamine adsorbed onto the surface of the protonated strontium titanate particles, making the particles hydrophilic. Consequently, a white dispersion of strontium titanate particles in water was obtained.

[0132] Based on the above, the dispersion of Example 3-1 was manufactured.

[0133] [Example 4-1]

[0134] The dispersion of Example 4-1 was prepared using the following method.

[0135] <First mixing process>

[0136] One g of spherical titanium dioxide particles with a diameter of 60 nm, modified with oleic acid, were placed in 30 mL of a mixed aqueous solution of 0.05 mol / L nitric acid and 1 mol / L acetic acid and stirred for 24 hours. This process, involving the nitric acid and acetic acid, cleaved the oleic acid in the titanium dioxide particles, thus protonating them.

[0137] <Cleaning and Recycling Process>

[0138] First, the titanium oxide particles and the mixed aqueous solution are separated by centrifugation of the stirred liquid obtained in the first stirring step. Next, the mixed aqueous solution is discarded, and the remaining titanium oxide particles are recovered. These particles are then washed by stirring in water. Then, the resulting stirred liquid is centrifuged to separate the titanium oxide particles from the water. The water is then discarded, and the remaining titanium oxide particles are recovered. The recovered titanium oxide particles are then protonated.

[0139] <Second mixing process>

[0140] The titanium oxide particles recovered during the washing and recycling process were placed in 30 mL of a 0.2 mol / L ammonia solution and stirred for 24 hours. As a result, ammonia was adsorbed onto the surface of the protonated titanium oxide particles, making the particles hydrophilic. Consequently, a white dispersion of titanium oxide particles in water was obtained.

[0141] Based on the above, the dispersion of Example 4-1 was manufactured.

[0142] [Rating 1]

[0143] For the dispersions of Examples 1-1, 2-1, 3-1, and 4-1, the zeta potential and particle size distribution were measured using a dynamic light scattering measurement device, the "Zetasizer nano," manufactured by Malvern Instruments. Furthermore, for the dispersions of Examples 1-1, 2-1, 3-1, and 4-1, after the zeta potential and particle size distribution measurements were taken, the presence or absence of precipitation was confirmed after standing for more than 30 days. The results are as follows.

[0144] Regarding the dispersion of Example 1-1, the zeta potential is -39.4 mV, and the particle size distribution is as follows: Figure 1 This results in a steep distribution. Figure 1 This is a graph showing the measurement results of the particle size distribution in the dispersion of Example 1-1. Furthermore, even after the dispersion of Example 1-1 was left for more than 30 days following the measurement of zeta potential and particle size distribution, no precipitation was observed. Therefore, the dispersion of Example 1-1 confirms that barium titanate particles have high dispersibility in water, a polar solvent.

[0145] Regarding the dispersion of Example 2-1, the zeta potential is -35.3 mV, and the particle size distribution is as follows: Figure 2 This results in a steep distribution. Figure 2 This is a graph showing the measurement results of particle size distribution in the dispersion of Example 2-1. Furthermore, even after the dispersion of Example 2-1 was left for more than 30 days following the measurement of zeta potential and particle size distribution, no precipitation was observed. Therefore, the dispersion of Example 2-1 confirms that barium titanate particles have high dispersibility in water, a polar solvent.

[0146] Regarding the dispersion of Example 3-1, the zeta potential is -23.7 mV, and the particle size distribution is as follows: Figure 3 This results in a steep distribution. Figure 3 This is a graph showing the measurement results of particle size distribution in the dispersion of Example 3-1. Furthermore, even after the dispersion of Example 3-1 was left for more than 30 days following the measurement of zeta potential and particle size distribution, no precipitation was observed. Therefore, the dispersion of Example 3-1 confirms that strontium titanate particles have high dispersibility in water, a polar solvent.

[0147] Regarding the dispersion of Example 4-1, the zeta potential is -30.5 mV, and the particle size distribution is as follows: Figure 4 This results in a steep distribution. Figure 4 This is a graph showing the measurement results of particle size distribution in the dispersion of Example 4-1. Furthermore, even after the dispersion of Example 4-1 was left for more than 30 days following the measurement of zeta potential and particle size distribution, no precipitation was observed. Therefore, it can be confirmed that the titanium oxide particles in the dispersion of Example 4-1 exhibit high dispersibility in water, a polar solvent.

[0148] [Examples 1-2]

[0149] Using the dispersion from Example 1-1, ceramic sheets of Example 1-2 were manufactured by the following method. First, the dispersion from Example 1-1 was coated onto the surface of a Pt / Si substrate using a dip-coating method. More specifically, the Pt / Si substrate was immersed in the dispersion from Example 1-1 and then lifted at a speed of 1 μm / min. Subsequently, the coating of the dispersion from Example 1-1 was dried, thereby forming the ceramic sheets of Example 1-2 on the Pt / Si substrate.

[0150] [Example 2-2]

[0151] Except for the dispersion used in Example 2-1, the ceramic sheets of Example 2-2 were manufactured in the same manner as the ceramic sheets of Example 1-2.

[0152] [Rating 2]

[0153] For the ceramic sheets of Examples 1-2 and 2-2, the packing state of the barium titanate particles was confirmed. The results are as follows.

[0154] Figure 5 This is a schematic diagram showing the planar structure of the ceramic sheet in Examples 1-2. Figure 6 This is a schematic diagram showing the cross-sectional structure of the ceramic sheets in Examples 1-2. For example... Figure 5 and Figure 6 As shown, in the ceramic sheet 10A of Examples 1-2, it can be confirmed that barium titanate particles 15A are densely, more specifically, stacked on the Pt / Si substrate 20 with a three-dimensional arrangement.

[0155] Figure 7 This is a schematic diagram showing the planar structure of the ceramic sheet in Example 2-2. Figure 8 This is a schematic diagram showing the cross-sectional structure of the ceramic sheet in Example 2-2. For example... Figure 7 and Figure 8 As shown, in the ceramic sheet 10B of Example 2-2, it can be confirmed that the barium titanate particles 15B are densely, more specifically, stacked on the Pt / Si substrate 20 with a three-dimensional arrangement.

[0156] [Examples 1-3]

[0157] The ceramic sheets of Examples 1-2 were fired at 1100°C to sinter the barium titanate particles, thereby producing the ceramic sintered layers of Examples 1-3.

[0158] [Examples 2-3]

[0159] Except for the ceramic sheet used in Example 2-2, the ceramic sintered layers of Example 2-3 were manufactured in the same manner as the ceramic sintered layers of Example 1-3.

[0160] [Rating 3]

[0161] For the ceramic sintered layers of Examples 1-3 and 2-3, capacitors were constructed by forming Pt electrodes on the surface opposite to the Pt / Si substrate. Then, for each capacitor, measurements were performed using an LCR meter at 1 kHz and 10 mV, thereby measuring the relative permittivity and temperature characteristics of the dielectric loss tangent of the ceramic sintered layers of Examples 1-3 and 2-3. The results are as follows.

[0162] Figure 9 This is a graph showing the measurement results of the temperature characteristics of the relative permittivity and dielectric loss tangent in the ceramic sintered layers of Examples 1-3. (See graph for details.) Figure 9 As shown, the relative permittivity of the ceramic sintered layers in Examples 1-3 is very high over a wide temperature range, approximately 700 at room temperature. Furthermore, due to... Figure 9The dielectric loss tangent shown is a low value, so it can be said that... Figure 9 The measured relative permittivity results shown essentially reflect the relative permittivity of the ceramic sintered layers of Examples 1-3 themselves. Therefore, if the ceramic sintered layers of Examples 1-3 are used, for example, as the dielectric layer of a multilayer ceramic capacitor, it can be considered that a large capacitance can be obtained over a wide temperature range. Furthermore, according to... Figure 9 The measured results of the relative permittivity and dielectric loss tangent shown can be considered as the ceramic sintered layers of Examples 1-3, indicating that a dense ceramic sintered layer using barium titanate particles was obtained.

[0163] Figure 10 This is a graph showing the measurement results of the temperature characteristics of the relative permittivity and dielectric loss tangent in the ceramic sintered layers of Examples 2-3. (See figure) Figure 10 As shown, the relative permittivity of the ceramic sintered layers in Examples 2-3 is very high over a wide temperature range, approximately 1500 at room temperature. Furthermore, due to... Figure 10 The dielectric loss tangent shown is a low value, therefore Figure 10 The measured relative permittivity results shown substantially reflect the relative permittivity of the ceramic sintered layers of Examples 2-3 themselves. Therefore, it can be considered that if the ceramic sintered layers of Examples 2-3 are used, for example, as the dielectric layer of a multilayer ceramic capacitor, a larger capacitance can be obtained over a wider temperature range compared to the case of using the ceramic sintered layers of Examples 1-3. Furthermore, according to... Figure 10 The measured results of the relative permittivity and dielectric loss tangent shown, as ceramic sintered layers of Examples 2-3, can be considered as dense ceramic sintered layers using barium titanate particles.

[0164] [Examples 1-4]

[0165] The ceramic sheets from Examples 1-2 were immersed in 100 mL of a 3 mol / L YCl3 aqueous solution for 24 hours while still attached to a Pt / Si substrate. Subsequently, the ceramic sheets with the Pt / Si substrate were removed from the YCl3 aqueous solution and dried in dry air, thereby obtaining the ceramic sheets from Examples 1-4 disposed on a Pt / Si substrate.

[0166] [Examples 2-4]

[0167] The ceramic sheets from Examples 1-2 were immersed in 100 mL of a 1 mol / L Mn(NO3)2 aqueous solution for 24 hours while still attached to a Pt / Si substrate. Subsequently, the ceramic sheets with the Pt / Si substrate were removed from the Mn(NO3)2 aqueous solution and dried in dry air, thereby obtaining the ceramic sheets from Examples 2-4 disposed on a Pt / Si substrate.

[0168] [Rating 4]

[0169] For the ceramic sheets of Examples 1-4 and 2-4, cross-sections were fabricated using focused ion beam (FIB) on a Pt / Si substrate. Then, elemental mapping was performed on the cross-sections of each ceramic sheet using scanning transmission electron microscopy-energy dispersive X-ray diffraction (STEM-EDS). The results are as follows.

[0170] Figure 11 This is a STEM image showing the cross-section of the ceramic sheet in Examples 1-4. Figure 12 It means Figure 11 The elemental mapping of the distribution of Ti in the STEM image is shown. Figure 13 It means Figure 11 The elemental mapping of the distribution of Ba in the STEM image is shown. Figure 14 It means Figure 11 The elemental mapping of the distribution state of Y in the STEM image shown. Figure 15 This is a schematic diagram showing the manufacturing process of the ceramic sheets in Examples 1-4.

[0171] like Figure 11 As shown, in the ceramic sheets of Examples 1-4, particle alignment was confirmed. Then, these aligned particles were... Figure 12 The distribution of Ti shown and Figure 13 The distribution of Ba shown confirms that they are barium titanate particles. Furthermore, from... Figure 14 The distribution of Y shown confirms that Y exists at the interface of the barium titanate particles. Therefore, it can be considered that Y exists in the ceramic sheets of Examples 1-4 as a shell of the barium titanate particles.

[0172] Based on the above, it can be confirmed that when manufacturing the ceramic sheets of Examples 1-4, if... Figure 15 As shown, by using the ceramic sheets of Examples 1-2 ( Figure 15 The topmost state of the middle) is immersed in YCl3 aqueous solution ( Figure 15 The central state of the barium titanate (BaTiO3) particles is modified with tetrabutylammonium hydroxide ions (TBA+) and Y ions (Y). 3+ ) exchange (cation exchange), Y ion (Y 3+ Precipitation occurs at the interface of barium titanate (BaTiO3) particles. Figure 15 (The state at the bottom of the middle).

[0173] Figure 16 This is a STEM image showing the cross-section of the ceramic sheet in Examples 2-4. Figure 17 It means Figure 16 The elemental mapping of the distribution of Ti in the STEM image is shown. Figure 18It means Figure 16 The elemental mapping of the distribution of Ba in the STEM image is shown. Figure 19 It means Figure 16 The elemental mapping diagram of the distribution state of Mn in the STEM image shown. Figure 20 This is a schematic diagram showing the manufacturing process of the ceramic sheets in Examples 2-4.

[0174] like Figure 16 As shown, in the ceramic sheets of Examples 2-4, particle alignment can be confirmed. Then, these aligned particles, according to... Figure 17 The distribution of Ti shown and Figure 18 The distribution of Ba shown confirms that it consists of barium titanate particles. Furthermore, according to... Figure 19 The distribution of Mn shown confirms that Mn exists at the interface of the barium titanate particles. Therefore, it can be considered that Mn exists in the ceramic sheets of Examples 2-4 as a shell of the barium titanate particles.

[0175] From the above, it can be confirmed that when manufacturing the ceramic sheets of Examples 2-4, if... Figure 20 As shown, by using the ceramic sheets of Examples 1-2 ( Figure 20 The topmost state of the middle) is immersed in an aqueous solution of Mn(NO3)2. Figure 20 The central state of the barium titanate (BaTiO3) particles is modified with tetrabutylammonium hydroxide ions (TBA+) and Mn ions (Mn). 2+ ) exchange (cation exchange), Mn ions (Mn 2+ Precipitation occurs at the interface of barium titanate (BaTiO3) particles. Figure 20 (The state at the bottom of the middle).

[0176] [Examples 1-5]

[0177] The ceramic sheets of Examples 1-4 were fired at 700°C to sinter the barium titanate particles, thereby producing the ceramic sintered layers of Examples 1-5.

[0178] [Examples 2-5]

[0179] Except for the ceramic sheets used in Examples 2-4, the ceramic sintered layers of Examples 2-5 were manufactured in the same manner as the ceramic sintered layers of Examples 1-5.

[0180] [Rating 5]

[0181] For the ceramic sintered layers of Examples 1-5 and 2-5, capacitors were constructed by forming Pt electrodes on the surface opposite to the Pt / Si substrate. Then, for each capacitor, the temperature characteristics of the relative permittivity of the ceramic sintered layers of Examples 1-5 and 2-5 were measured using an LCR meter at 1 kHz and 10 mV. The results are as follows.

[0182] Figure 21 This is a graph showing the measurement results of the temperature characteristics of the relative permittivity in the ceramic sintered layers of Examples 1-5. (See graph for details.) Figure 21 As shown, the relative permittivity of the ceramic sintered layers of Examples 1-5 is very high and hardly changes over a wide temperature range, approximately 750 at room temperature. Therefore, if the ceramic sintered layers of Examples 1-5 are used, for example, as the dielectric layer of a multilayer ceramic capacitor, it is considered that a large capacitance can be obtained over a wide temperature range while the relative permittivity remains almost unchanged. Furthermore, from Figure 21 The relative permittivity measurement results shown indicate that, as ceramic sintered layers of Examples 1-5, a dense ceramic sintered layer using barium titanate particles was obtained.

[0183] Figure 22 This is a graph showing the measurement results of the temperature characteristics of the relative permittivity in the ceramic sintered layers of Examples 2-5. (See graph for details.) Figure 22 As shown, the relative permittivity of the ceramic sintered layers of Examples 2-5 is very high and hardly changes over a wide temperature range, approximately 780 at room temperature. Therefore, if the ceramic sintered layers of Examples 2-5 are used, for example, as the dielectric layer of a multilayer ceramic capacitor, it is considered that a large capacitance can be obtained over a wide temperature range with almost no change in the relative permittivity. Furthermore, according to... Figure 22 The relative permittivity measurement results shown indicate that, as ceramic sintered layers of Examples 2-5, a dense ceramic sintered layer using barium titanate particles was obtained.

[0184] Symbol Explanation

[0185] 10A and 10B ceramic sheets

[0186] 15A and 15B barium titanate particles

[0187] 20Pt / Si substrate

Claims

1. A method for manufacturing a dispersion, characterized in that, have: In the first stirring step, the metal oxide particles modified with organic acid are placed in a first solution containing at least one of inorganic acid and acetic acid and a solvent and stirred. The cleaning and recycling process involves cleaning the metal oxide particles after they have been stirred in the first stirring process and then recycling them. In the second stirring step, the metal oxide particles recovered from the cleaning and recovery step are placed in a second solution containing at least one of an amine and ammonia, as well as a polar solvent, and stirred.

2. The method for manufacturing the dispersion according to claim 1, wherein, The polar solvent contained in the second solution is water.

3. The method for manufacturing the dispersion according to claim 1 or 2, wherein, The organic acid is at least one selected from the group consisting of acetic acid, citric acid, oxalic acid, propionic acid, oleic acid, linoleic acid and linolenic acid.

4. The method for manufacturing the dispersion according to claim 1 or 2, wherein, The metal oxide constituting the metal oxide particles is at least one selected from the group consisting of barium titanate, strontium titanate, zirconium titanate, zirconium oxide, hafnium oxide, cerium oxide and titanium oxide.

5. The method for manufacturing the dispersion according to claim 1 or 2, wherein, The particle size of the metal oxide particles is greater than 15 nm and less than 100 nm.

6. The method for manufacturing the dispersion according to claim 1 or 2, wherein, The inorganic acid is at least one selected from the group consisting of hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, and boric acid.

7. The method for manufacturing the dispersion according to claim 6, wherein, The inorganic acid is nitric acid.

8. The method for manufacturing the dispersion according to claim 1 or 2, wherein, The amine is selected from at least one of the group consisting of tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, monoethanolamine, diethanolamine, triethanolamine, monoethylamine, diethylamine, and triethylamine.

9. The method for manufacturing the dispersion according to claim 8, wherein, The amine is tetrabutylammonium hydroxide.

10. A method for manufacturing metal oxide particles, characterized in that, have: The dispersion manufacturing process involves manufacturing a dispersion using the dispersion manufacturing method described in any one of claims 1 to 9. The metal ion adsorption process involves adsorbing at least one metal ionized from the group consisting of Mg, Ca, Sr, Mn, Fe, Co, Ni, Cu, Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Gd, Tb, Dy, Ho, Eu, Tm, Yb, and Lu at the interface of the metal oxide particles contained in the dispersion.

11. The method for manufacturing metal oxide particles according to claim 10, wherein, In the metal ion adsorption process, the metal oxide particles contained in the dispersion are placed in an aqueous solution of a metal salt containing the metal ions dissolved in water.

12. The method for manufacturing metal oxide particles according to claim 11, wherein, The metal salt is selected from at least one group consisting of chloride salts, acetates, nitrates, sulfates, phosphates and borates.

13. A method for manufacturing ceramic sheets, characterized in that, have: The dispersion manufacturing process involves manufacturing a dispersion using the dispersion manufacturing method described in any one of claims 1 to 9. The forming process involves shaping the dispersion into a sheet on a substrate.

14. The method for manufacturing ceramic sheets according to claim 13, wherein, It also includes a metal ion adsorption process, which causes the interface of the metal oxide particles contained in the sheet formed by the forming process to adsorb at least one metal ionized metal ion selected from the group consisting of Mg, Ca, Sr, Mn, Fe, Co, Ni, Cu, Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Gd, Tb, Dy, Ho, Eu, Tm, Yb and Lu.

15. The method for manufacturing ceramic sheets according to claim 14, wherein, In the metal ion adsorption process, the sheet is placed in an aqueous solution of a metal salt containing the metal ions dissolved in water.

16. The method for manufacturing ceramic sheets according to claim 15, wherein, The metal salt is selected from at least one group consisting of chloride salts, acetates, nitrates, sulfates, phosphates and borates.

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