Zirconium powder material

Abstract

The present invention addresses the problem of providing a zirconia powder material which can be easily crushed. A zirconia powder material according to the present disclosure contains 95% by mass or more of ZrO2 with the balance being made up of unavoidable impurities, and satisfies at least one of the requirements described below. Requirement (1): the 10% deformation test force P (mN) in a micro compression strength test is in the range of 0 < P ≤ 0.012, Requirement (2): the number of neckings formed by primary particles as determined by STEM tomography analysis is less than 3, Requirement (3): the coefficient of variation in the particle size distribution of the primary particles as determined by STEM tomography analysis is 0.35 or less, and the average particle diameter is 25 nm or more

Description

Zirconium powder material

[0001] This invention relates to zirconium powder materials.

[0002] Zirconia powder materials, primarily composed of zirconium oxide, are attracting attention as additives that improve the properties of electronic materials. Specific applications include compounding with electrode active materials to stabilize the structure of electrode active materials in lithium-ion secondary batteries, using them as inorganic fillers to improve the heat resistance of separators, and using them as dielectric calcium zirconate (CaZrO) in multilayer ceramic capacitors (MLCCs). ３ Examples of applications include raw materials for the manufacture of perovskite-type composite oxides (low dielectric temperature compensation applications), such as ).

[0003] In recent years, as miniaturization of MLCCs has become a priority, there has also been a demand for higher capacitance, making it common practice to achieve both thin-layer and multi-layer construction. Consequently, MLCC manufacturers are increasingly using CaZrO as the dielectric material. ３ Further miniaturization of the material has been investigated. For example, Patent Document 1 discloses a method for providing a fine zirconium oxide powder with very small particle size, a sharp particle size distribution, good dispersibility, few impurities, and extremely low bulk density and tap density. This method involves generating a basic zirconium sulfate precipitate by dispersing an aqueous ammonium sulfate solution in a heated and stirred aqueous zirconium salt solution over time, then neutralizing this precipitate with alkali to convert it to zirconium hydroxide, and finally processing it by a conventional method to obtain zirconium oxide powder.

[0004] Special Publication No. 6-88791

[0005] As mentioned above, for example, miniaturization of MLCCs requires the miniaturization of the dielectric material, which necessitates the miniaturization of the raw material. However, as the raw material is miniaturized, the particles come into contact with each other more easily during the process of obtaining the raw material (e.g., drying and firing), and particle clusters (aggregates) are easily formed. Once such aggregates are formed, it is usually difficult to break them apart (disintegrate them). On the other hand, when compounding zirconia powder material with other materials, as is done in MLCCs, it is important to compound them as uniformly as possible. Therefore, the challenge is to provide a zirconia powder material with weak cohesive force. Thus, the problem that the present invention aims to solve is to provide a zirconia powder material that can be easily disintegrated.

[0006] The above problems can be solved by the following means.

[0007] ZrO ２ A zirconia powder material consisting of 95% by mass or more of zirconia and the remainder being unavoidable impurities, satisfying at least one of the following requirements: Requirement (1): The 10% deformation test force P (mN) in the microcompression strength test is in the range of 0 < P ≤ 0.012; Requirement (2): The number of neckings formed by primary particles by STEM tomography analysis is less than 3; Requirement (3): The coefficient of variation in the particle size distribution of primary particles by STEM tomography analysis is 0.35 or less, and the average particle size is 25 nm or more.

[0008] In this specification, "X to Y" is used to mean "X or greater and Y or less," including the numerical values ​​(X and Y) before and after it as the lower and upper limits, respectively. When multiple "X to Y" or "X or greater and Y or less" are described, for example, when "X1 to Y1, or X2 to Y2" is described, all disclosures are made with each numerical value as the upper limit, each numerical value as the lower limit, and all combinations of these upper and lower limits (i.e., they provide a lawful basis for amendments). Specifically, amendments with respect to X1 or greater, amendments with respect to Y2 or less, amendments with respect to X1 or less, amendments with respect to Y2 or greater, amendments with respect to X1 to X2, amendments with respect to X1 to Y2, etc., must all be considered lawful. In addition, unless otherwise specified, operations and measurements of physical properties, etc., are performed under conditions of room temperature (20 to 25°C) / relative humidity 40 to 50% RH. Furthermore, all combinations of embodiments and descriptions disclosed in this specification must be understood to be disclosed in this application. In other words, they must be understood to provide a basis for amendments. Furthermore, when there is a description of the content or concentration of each component, if two or more are included, it may refer to the total amount. Note that the expression "X or more" means "X or greater than X," and the expression "Y or less" means "Y or less than Y."

[0009] <Zirconia Powder Material> In one embodiment of the present invention, ZrO ２ A zirconia powder material is provided that consists of 95% by mass or more of zirconia and the remainder being unavoidable impurities, and satisfies at least one of the following requirements: (1) the 10% deformation test force P (mN) in the microcompression strength test is in the range of 0 < P ≤ 0.012; (2) the number of neckings formed by primary particles by STEM tomography analysis is less than 3; and (3) the coefficient of variation in the particle size distribution of primary particles by STEM tomography analysis is 0.35 or less, and the average particle size is 25 nm or more. According to this embodiment, a zirconia powder material that can be easily crushed can be provided.

[0010] Zirconia powder material is zirconia (ZrO ２It contains ) with a mass percentage of 95% or more, and the remainder consists of unavoidable impurities. Examples of unavoidable impurities include hafnium oxide. Hafnium coexists with zirconium and has very similar chemical properties, so it is usually an unavoidable impurity that is difficult to separate. It is known that the hafnium content in zirconium ore is about 1 to 4 wt%. Zirconia (ZrO) contained in zirconia powder material ２ The amount of zirconia (ZrO) contained in the zirconia powder material may be 97% by mass or more, 99% by mass or more, 99.5% by mass or more, or 99.85% by mass or more. ２ The upper limit of the content of ) can be, for example, 100% by mass (i.e., the zirconia powder material is composed only of zirconia), 99.95% by mass or less, or 99.5% by mass or less. In one embodiment of the present invention, the zirconia (ZrO) contained in the zirconia powder material ２ The mass may be 97% or more and 99.95% or less, or 99% or more and 99.5% or less.

[0011] (Requirement (1)) In one embodiment of the present invention, the 10% deformation test force P (mN) in the microcompression strength test of the zirconia powder material is in the range of 0 < P ≤ 0.012. Because the 10% deformation test force P (mN) in the microcompression strength test of the zirconia powder material is in such a range, the zirconia powder material can be easily converted into primary particles, and when compounded with other materials, the particles constituting the zirconia powder material can be uniformly diffused. Therefore, compounding with other particles can be performed at low temperatures. The smaller the value of the 10% deformation test force P (mN), the smaller the force required for deformation. Therefore, the 10% deformation test force P (mN) in the microcompression strength test is preferably 0.011 or less, more preferably 0.010 or less, even more preferably 0.009 or less, and even more preferably 0.008 or less. The lower limit of the 10% deformation test force P (mN) in the microcompression strength test is greater than 0, but can be, for example, 0.001 or more, 0.003 or more, or 0.005 or more. The method of the microcompression strength test will be described in the Examples section. In one embodiment of the present invention, the 10% deformation test force P (mN) in the microcompression strength test of the zirconia powder material can be 0.001 or more and 0.011 or less, or 0.003 or more and 0.010 or less.

[0012] (Requirement (2)) In one embodiment of the present invention, the number of neckings formed by primary particles in the zirconia powder material as determined by STEM tomography analysis is less than three. Here, necking refers to the bonding between primary particles that constitute secondary particles (aggregates) of the zirconia powder material. The bonding referred to here is not a chemical bond, but a bond that originates from a weak force that causes particles to attract each other. The presence of necking can be specifically confirmed by STEM tomography analysis. Primary particles as determined by STEM tomography analysis are, in other words, the smallest unit of particles observed in the STEM tomography analysis image. In the zirconia powder material of this disclosure, the primary particles of zirconia particles are not densely aggregated, that is, the density of primary particles in the secondary particles (aggregates) is small, so there are few bonds (neckings) between primary particles that constitute the aggregates. Zirconia powder material composed of such particles can be easily crushed. Therefore, the zirconia powder material can be easily converted into primary particles, and when compounded with other materials, the particles constituting the zirconia powder material can be uniformly dispersed. Therefore, compounding with other particles can be performed at low temperatures. In one embodiment of the present invention, the number of neckings formed by primary particles in the zirconia powder material by STEM tomography analysis is preferably 2.50 or less, 2.30 or less, 2.10 or less, 2.00 or less, 1.96 or less, 1.95 or less, 1.94 or less, 1.93 or less, and 1.00 or less, in that order. In one embodiment of the present invention, the lower limit of the number of neckings formed by primary particles in the zirconia powder material by STEM tomography analysis is, for example, greater than 0, 1.30 or more, or 1.60 or more. The method for calculating the number of neckings will be explained in the Examples section. In one embodiment of the present invention, the number of neckings formed by primary particles in a zirconia powder material by STEM tomography analysis may be 1.00 or more and 2.50 or less, 1.30 or more and 2.00 or less, 1.30 or more and 1.96 or less, or 1.30 or more and 1.95 or less.

[0013] (Requirement (3)) In one embodiment of the present invention, the coefficient of variation in the particle size distribution of primary particles in the zirconia powder material, as determined by STEM tomography analysis, is 0.35 or less, and the average particle size is 25 nm or more. The width of the particle size distribution in the zirconia powder material being 0.35 or less allows for uniform mixing even if the powder properties of the other material particles differ when compounding with particles of other materials, and consequently, the temperature required for compounding can be reduced. Furthermore, the average particle size of the zirconia powder material being 25 nm or more has the technical effect of suppressing contact points between particles and suppressing the increase in the number of necking formations. In one embodiment of the present invention, the coefficient of variation in the particle size distribution of primary particles in the zirconia powder material, as determined by STEM tomography analysis, is preferably 0.34 or less, more preferably 0.30 or less, and even more preferably 0.29 or less. By setting the coefficient of variation in the particle size distribution of primary particles in zirconia powder material, as determined by STEM tomography analysis, to such an upper limit, more uniform mixing can be achieved when compounding with other material particles, even if the powder properties of those other material particles differ, and consequently, the temperature required for compounding can be lowered. In one embodiment of the present invention, the lower limit of the coefficient of variation in the particle size distribution of primary particles in zirconia powder material, as determined by STEM tomography analysis, can realistically be, for example, 0.15 or higher. In one embodiment of the present invention, the coefficient of variation in the particle size distribution of primary particles in zirconia powder material, as determined by STEM tomography analysis, is 0.15 or more and 0.34 or less, 0.15 or more and 0.30 or less, or 0.15 or more and 0.29 or less. In one embodiment of the present invention, the average particle size of the zirconia powder material is preferably 20 nm or more, 22 nm or more, 24 nm or more, 26 nm or more, and 28 nm or more, in that order. Having such a lower limit for the average particle size of the zirconia powder material has the technical effect of more efficiently suppressing contact sites between particles and more efficiently suppressing the increase in the number of necking formations. In one embodiment of the present invention, the upper limit of the average particle size of the zirconia powder material is, for example, 45 nm or less, 40 nm or less, 35 nm or less, 33 nm or less, or 29.5 nm or less.In one embodiment of the present invention, the average particle diameter of the zirconia powder material is 20 nm or more and 40 nm or less, 22 nm or more and 35 nm or less, 24 nm or more and 33 nm or less, 26 nm or more and 29.5 nm or less, or 28 nm or more and 29.5 nm or less. When the average particle diameter of the zirconia powder material has such an upper limit, the final reached particle diameter (the particle size obtained when the disintegration treatment is performed until no change occurs in the particle size distribution) after the disintegration treatment can be reduced. This average particle diameter can generally be measured by observation with a transmission electron microscope. The particle diameter observed with a transmission electron microscope means the maximum distance among distances between any two points on the contour line of an observed particle (observation surface). As the value of the average particle diameter, a value calculated as an average value of particle diameters of particles observed in several to several tens of fields of view (for example, 3 to 30 fields of view) is used, and specifically, the method described in the Examples can be used. The acceleration voltage in a transmission electron microscope is typically set to 200 kV.

[0014] In one embodiment of the present invention, the zirconia powder material satisfies at least one requirement among requirement (1), requirement (2), and requirement (3), preferably satisfies at least requirement (1), more preferably satisfies requirement (1) and requirement (2), or satisfies requirement (1) and requirement (3), and even more preferably satisfies all of requirement (1), requirement (2), and requirement (3). As the number of satisfied requirements increases in this manner, the intended effect of the present invention can be achieved more efficiently.

[0015] <Method for Producing Zirconia Powder Material> According to one embodiment of the present invention, for example, ZrO ２ is 95% by mass or more, and the balance consists of unavoidable impurities: requirement (1): the 10% deformation test force P (mN) in a micro-compression strength test is in the range of 0 < P ≦ 0.012; requirement (2): the number of necks formed by primary particles according to STEM tomography analysis is less than 3; requirement (3): the coefficient of variation in the particle size distribution of primary particles according to STEM tomography analysis is 0.35 or less, and the average particle diameter is 25 nm or more. Provided is a method for producing a zirconia powder material that satisfies at least one of the above requirements. For requirements (1) to (3), refer to the above description.

[0016] According to one embodiment of the present invention, a method for producing a zirconia powder material is provided, which involves obtaining zirconium hydroxide from a raw material zirconium as a starting material, and then heat-treating the zirconium hydroxide.

[0017] The raw material zirconium is preferably prepared in the form of a solution. That is, a solution containing the raw material zirconium is prepared. The raw material zirconium may be a zirconium salt. The zirconium salt can be any salt that dissociates into zirconium ions, such as at least one selected from the group consisting of zirconium oxynitrate, zirconium oxychloride, and zirconium nitrate. Among these, zirconium oxychloride is preferred. Examples of solvents used in the solution containing the raw material zirconium include water, dilute hydrochloric acid solution, or mixtures thereof. Water is preferred among these.

[0018] In a solution containing the raw material zirconium, the concentration of the raw material zirconium (e.g., zirconium oxychloride) is, for example, 0.1 to 0.7 M, 0.2 to 0.6 M, or 0.3 to 0.5 M. In 1.2 L of the solution containing the raw material zirconium, the amount of Zr is, for example, 0.2 to 0.7 moles, 0.3 to 0.6 moles, or 0.4 to 0.5 moles.

[0019] According to one embodiment of the present invention, a raw material zirconium is reacted with ammonium peroxodisulfate by contact. When producing zirconium hydroxide from raw material zirconium, ammonium sulfate is usually used as the sulfate chlorinator, but in the present invention, the use of ammonium peroxodisulfate is particularly preferred. After ammonium peroxodisulfate is added to the reaction system, it supplies the reaction raw materials through a decomposition reaction. During the process until this decomposition reaction occurs, ammonium peroxodisulfate diffuses sufficiently into the reaction system, and the sulfate chlorination reaction proceeds uniformly in the system. Furthermore, because the reaction proceeds uniformly, particle nucleation occurs almost simultaneously, so sintering during heat treatment can be suppressed, and the descalability of the resulting zirconium oxide is thought to be improved. This is the inventors' speculation, and this mechanism does not limit the technical scope of the present invention. Ammonium peroxodisulfate is preferably prepared in the form of a solution. That is, a solution containing ammonium peroxodisulfate is prepared. Examples of solvents used in the solution containing ammonium peroxodisulfate include water.

[0020] In a solution containing ammonium peroxodisulfate, the concentration of ammonium peroxodisulfate is, for example, 0.1–1.5 M, 0.2–1.4 M, 0.3–1.3 M, 0.4–1.0 M, or 0.5–0.9 M. In 0.2 L of a solution containing ammonium peroxodisulfate, the amount of substance of S is, for example, 0.05–0.5 mol, 0.1–0.4 mol, 0.2–0.4 mol, or 0.2–0.27 mol.

[0021] One embodiment of the present invention involves contacting a solution containing raw material zirconium with a solution containing ammonium peroxodisulfate, where S / Z is the ratio of the amount of S in ammonium peroxodisulfate to the amount of Zr in the raw material zirconium, and it is preferable to carry out the reaction such that the following conditions are satisfied: 0.460 ≤ S / Z ≤ 0.800, preferably 0.460 ≤ S / Z ≤ 0.600. In this specification, "S" in S / Z refers to the amount of sulfur atoms, and "Z" refers to the amount of zirconia atoms. If, for example, ammonium sulfate is used instead of ammonium peroxodisulfate, it may not be possible to provide a zirconia powder material that can be easily crushed. Also, even if ammonium peroxodisulfate is used as a sulfated chlorine agent, if S / Z is less than 0.460 or greater than 0.800, it may not be possible to provide a zirconia powder material that can be easily crushed.

[0022] According to one embodiment of the present invention, the solution containing the raw material zirconium is heated before contacting the raw material zirconium with ammonium peroxodisulfate. The temperature of the solution containing the raw material zirconium is, for example, 70 to 99°C, 80 to 97°C, or 90 to 97°C. In particular, if the temperature exceeds 90°C, the aqueous solution of the zirconium salt becomes moderately hot, and fine particle nuclei of zirconia are obtained. Since these fine particles become reaction nuclei later, it is expected that the reaction will be made more homogenized. According to one embodiment of the present invention, the solution containing the raw material zirconium is heated before contacting the raw material zirconium with ammonium peroxodisulfate, and the temperature of the solution containing the raw material zirconium is between 90°C and 99°C.

[0023] According to one embodiment of the present invention, a solution containing ammonium peroxodisulfate is heated before contacting the raw material zirconium with ammonium peroxodisulfate. The temperature of the solution containing ammonium peroxodisulfate is, for example, 50°C or more and less than 80°C, 60°C or more and less than 80°C, 60 to 70°C, or 60 to 65°C. When the temperature of the solution containing ammonium peroxodisulfate is within this range, a zirconia powder material that can be easily crushed can be provided. Keeping the temperature below 80°C also has the effect of suppressing the decomposition of ammonium peroxodisulfate. In this embodiment, 63°C was used, but similar effects can be expected even if the temperature is changed to a temperature below 60°C, such as 59°C. Therefore, according to one embodiment of the present invention, a solution containing ammonium peroxodisulfate is heated before contacting the raw material zirconium with ammonium peroxodisulfate, and the temperature of the solution containing ammonium peroxodisulfate is below 60°C, for example, 58°C or higher.

[0024] According to one embodiment of the present invention, the ratio of the temperature of the solution containing the raw material zirconium (°C) to the temperature of the solution containing ammonium peroxodisulfate (°C) is 1.2 to 1.7, or 1.3 to 1.5.

[0025] According to one embodiment of the present invention, contact between a solution containing raw material zirconium and a solution containing ammonium peroxodisulfate is carried out by adding the solution containing ammonium peroxodisulfate to the solution containing raw material zirconium. In this case, the addition rate of the solution containing ammonium peroxodisulfate is preferably 5 to 30 mL / min, 10 to 27 mL / min, or 15 to 23 mL / min. Within this range, a zirconia powder material that can be crushed more easily can be provided. Particularly important is that, unlike other sulfated chlorides, ammonium peroxodisulfate is generated after the addition of sulfate ions, which serve as the reaction initiation point. Therefore, it is important to complete the addition of ammonium peroxodisulfate before the sulfate ion generation reaction begins. By doing so, a zirconia powder material that can be crushed easily can be provided more efficiently. Accordingly, according to one embodiment of the present invention, the addition of ammonium peroxodisulfate is completed before the sulfate ion generation reaction begins. The start of the sulfate ion generation reaction may be confirmed, for example, by visually observing foaming or by monitoring the rise in temperature. According to one embodiment of the present invention, before contact between the solution containing raw material zirconium and the solution containing ammonium peroxodisulfate, the temperature of the solution containing raw material zirconium is higher than the temperature of the solution containing ammonium peroxodisulfate. In this case, if the temperature of the solution containing raw material zirconium is maintained by using a mantle heater or the like (without changing the set temperature of the mantle heater), and it is confirmed that the temperature rises (for example, rises by 5°C or more from the set temperature of the mantle heater) when the solution containing ammonium peroxodisulfate is brought into contact with it, then it can be considered that the sulfate rhizate formation reaction has started. According to one embodiment of the present invention, the addition rate of the solution containing ammonium peroxodisulfate is 7% by volume / min or more, when the total amount added is 100% by volume. An addition rate of 7% by volume / min or more allows for more efficient provision of zirconia powder material that can be easily crushed. According to one embodiment of the present invention, the addition rate of the solution containing ammonium peroxodisulfate is 7% by volume / min or more and 20% by volume / min or less, when the total amount added is 100% by volume.

[0026] It is preferable to add the solution containing ammonium peroxodisulfate while stirring the solution containing the raw material zirconium. Furthermore, it is preferable to continue stirring the mixture after adding the entire amount of ammonium peroxodisulfate. It is preferable to continue this stirring for, for example, 15 to 120 minutes, 30 to 90 minutes, or 45 to 75 minutes even after the entire amount of the solution containing ammonium peroxodisulfate has been added.

[0027] According to one embodiment of the present invention, basic zirconium sulfate is generated after the above contact or after the above stirring. Preferably, the pH is 0.1 to 0.5. Zirconium hydroxide can then be obtained by adding the basic zirconium sulfate slurry to the alkaline solution. Preferably, the pH is 8.5 to 9.0 after adding the basic zirconium sulfate slurry to the alkaline solution. This allows for complete precipitation of the zirconium and improves the yield. The obtained zirconium hydroxide can be separated using a separation method such as filtration. Washing with an alkaline solution is also preferable if necessary. For example, aqueous ammonia is a suitable alkaline solution.

[0028] According to one embodiment of the present invention, zirconium hydroxide is heat-treated. By heat-treating, a zirconia powder material can be obtained. The heat treatment temperature is, for example, 380°C to 950°C, 450°C to 880°C, or 500°C to 800°C. The heat treatment time is, for example, 0.5 to 12 hours, 1 to 9 hours, or 2 to 6 hours. The obtained zirconia powder material can be further pulverized as needed. Pulverization can be done at a laboratory level by grinding in a mortar and pestle, or by using a jet mill as needed. A jet mill is a process that uses high-pressure air or gas to pulverize a material into particles. The resulting pulverized particles can be collected in a collector or baghouse. When a counter-jet mill is used as the jet mill, the time until the pulverized particles are collected depends on the particle supply rate and gas pressure. This is because, in a counterjet mill where classification is performed by centrifugal force, pulverized particles that have become smaller than a certain size (for example, 200 μm or less, 100 μm or less, or 10 μm or less) are automatically collected according to their density. According to one embodiment of the present invention, the pressure of the air or gas is, for example, 0.05 to 0.3 MPa. According to one embodiment of the present invention, the supply amount of particles to be pulverized is, for example, 1 to 5 g / min.

[0029] It is preferable to obtain the zirconia powder material in the manner described above.

[0030] <Applications of Zirconia Powder Material> In one embodiment of the present invention, the applications of the zirconia powder material are not particularly limited, but zirconia powder material is attracting attention as an additive material that improves the properties of electronic materials. Specific applications include compounding with electrode active materials to stabilize the structure of electrode active materials in lithium-ion secondary batteries, using it as an inorganic filler to improve the heat resistance of separators, and using it as a dielectric calcium zirconate (CaZrO) in multilayer ceramic capacitors (MLCCs). ３raw material applications for producing perovskite-type composite oxides represented by ) (for low-dielectric temperature compensation applications), and the like. When compounding a zirconia powder material with other materials as used in MLCCs, the zirconia powder material of the present invention has weak cohesion between particles, so uniform compounding can be achieved. By uniformly mixing the starting raw materials of the composite material, the contact distance between these starting raw materials can be shortened. Therefore, synthesis at low temperature is enabled, particle growth can be suppressed, and micronization of the composite particles can be achieved.

[0031] The present invention includes the following aspects and embodiments.

[0032] 1. ZrO ２ is 95% by mass or more, with the balance being unavoidable impurities, and satisfies at least one of the following requirements: a zirconia powder material, wherein requirement (1): the 10% deformation test force P (mN) in a micro-compression strength test is in the range of 0 < P ≤ 0.012; requirement (2): the number of neckings formed by primary particles according to STEM tomography analysis is less than 3; requirement (3): the coefficient of variation in the particle size distribution of primary particles according to STEM tomography analysis is 0.35 or less, and the average particle diameter is 25 nm or more.

[0033] 2. The zirconia powder material according to 1., which satisfies (1) above.

[0034] 3. The zirconia powder material according to 1. or 2., wherein the 10% deformation test force P (mN) in the micro-compression strength test is 0.011 or less.

[0035] 4. The zirconia powder material according to any one of 1. to 3., wherein the 10% deformation test force P (mN) in the micro-compression strength test is 0.010 or less, 0.009 or less, or 0.008 or less.

[0036] 5. The zirconia powder material according to any one of 1. to 4., wherein the 10% deformation test force P (mN) in the micro-compression strength test is 0.001 or more.

[0037] 6. The zirconia powder material according to any one of 1. to 5., wherein the 10% deformation test force P (mN) in the micro-compression strength test is 0.003 or more, or 0.005 or more.

[0038] 7. The zirconia powder material according to any one of 1. to 6., wherein a 10% deformation test force P (mN) in the micro compression strength test is 0.001 or more and 0.011 or less.

[0039] 8. The zirconia powder material according to any one of 1. to 7., wherein a 10% deformation test force P (mN) in the micro compression strength test is 0.003 or more and 0.010 or less.

[0040] 9. The zirconia powder material according to any one of 1. to 8., which satisfies the above (2).

[0041] 10. The zirconia powder material according to any one of 1. to 9., wherein the number of necking is 2.5 or less.

[0042] 11. The zirconia powder material according to any one of 1. to 10., wherein the number of necking is 2.1 or less, 2 or less, 1.95 or less, 1.94 or less, 1.93 or less, or 1 or less.

[0043] 12. The zirconia powder material according to any one of 1. to 11., wherein the number of necking is 1 or more and 2.5 or less.

[0044] 13. The zirconia powder material according to any one of 1. to 12., wherein the number of necking is 1.3 or more and 2 or less, 1.3 or more and 1.96 or less, or 1.3 or more and 1.95 or less.

[0045] 14. The zirconia powder material according to any one of 1. to 13., which satisfies the above (3).

[0046] 15. The zirconia powder material according to any one of 1. to 14., wherein the coefficient of variation is 0.15 or more and 0.34 or less.

[0047] 16. The zirconia powder material according to any one of 1. to 15., wherein the coefficient of variation is 0.15 or more and 0.29 or less.

[0048] 17. The zirconia powder material according to any one of 1. to 16., wherein an average particle size of the zirconia powder material is 20 nm or more and 40 nm or less.

[0049] 18. The zirconia powder material according to any one of 1 to 17, wherein the average particle size of the zirconia powder material is 22 nm or more and 35 nm or less, 24 nm or more and 33 nm or less, 26 nm or more and 29.5 nm or less, or 28 nm or more and 29.5 nm or less.

[0050] 19. A method for producing zirconium hydroxide, comprising contacting a solution containing raw material zirconium with a solution containing ammonium peroxodisulfate, wherein the reaction is carried out such that the ratio of the amount of S in ammonium peroxodisulfate to the amount of Zr in the raw material zirconium is S / Z, and the following condition is satisfied: 0.460 ≤ S / Z ≤ 0.800.

[0051] 20. The method for producing zirconium hydroxide according to 19, wherein the concentration of the raw material zirconium in the solution containing the raw material zirconium is 0.1 to 0.7 M.

[0052] 21. A method for producing zirconium hydroxide according to 19 or 20, wherein the concentration of the raw material zirconium in the solution containing the raw material zirconium is 0.2 to 0.6 M or 0.3 to 0.5 M.

[0053] 22. A method for producing zirconium hydroxide according to any one of 19 to 21, wherein the amount of Zr in the solution containing the raw material zirconium is 0.2 to 0.7 moles.

[0054] 23. A method for producing zirconium hydroxide according to any one of 19 to 22, wherein the amount of Zr in the solution containing the raw material zirconium is 0.3 to 0.6 moles or 0.4 to 0.5 moles.

[0055] 24. A method for producing zirconium hydroxide according to any one of claims 19 to 23, wherein the concentration of ammonium peroxodisulfate in the solution containing ammonium peroxodisulfate is 0.1 to 1.5 M.

[0056] 25. A method for producing zirconium hydroxide according to any one of claims 19 to 24, wherein the concentration of ammonium peroxodisulfate in the solution containing ammonium peroxodisulfate is 0.2 to 1.4 M, 0.3 to 1.3 M, 0.4 to 1.0 M, or 0.5 to 0.9 M.

[0057] 26. A method for producing zirconium hydroxide according to any one of claims 19 to 25, wherein the amount of S in the solution containing ammonium peroxodisulfate is 0.05 to 0.5 moles.

[0058] 27. A method for producing zirconium hydroxide according to any one of 19 to 26, wherein the amount of S in the solution containing ammonium peroxodisulfate is 0.1 to 0.4 moles, 0.2 to 0.4 moles, or 0.2 to 0.27 moles.

[0059] 28. A method for producing zirconium hydroxide according to any one of 19 to 27, comprising carrying out the reaction such that 0.460 ≤ S / Z ≤ 0.600.

[0060] 29. A method for producing zirconium hydroxide according to any one of claims 19 to 28, comprising adjusting the temperature of the solution containing the raw material zirconium to 70 to 99°C before contact.

[0061] 30. A method for producing zirconium hydroxide according to any one of claims 19 to 29, comprising adjusting the temperature of the solution containing the raw material zirconium to 80 to 97°C, 90 to 97°C, or above 90°C and below 99°C before contact.

[0062] 31. A method for producing zirconium hydroxide according to any one of claims 19 to 30, comprising adjusting the temperature of the solution containing ammonium peroxodisulfate to 50 to 65°C before contact.

[0063] 32. A method for producing zirconium hydroxide according to any one of claims 19 to 31, comprising adjusting the temperature of the solution containing ammonium peroxodisulfate to 65°C or more and less than 80°C, 60°C or more and less than 80°C, 60 to 70°C, 60 to 65°C, 58°C or more and less than 60°C, or less than 60°C before contact.

[0064] 33. A method for producing zirconium hydroxide according to any one of claims 19 to 32, wherein contact between a solution containing raw material zirconium and a solution containing ammonium peroxodisulfate is carried out by adding the solution containing ammonium peroxodisulfate to the solution containing raw material zirconium, and the rate of addition of the solution containing ammonium peroxodisulfate is 5 to 30 mL / min.

[0065] 34. A method for producing zirconium hydroxide according to any one of claims 19 to 33, wherein contact between a solution containing raw material zirconium and a solution containing ammonium peroxodisulfate is carried out by adding the solution containing ammonium peroxodisulfate to the solution containing raw material zirconium, and the rate of addition of the solution containing ammonium peroxodisulfate is 10 to 27 mL / min.

[0066] 35. A method for producing zirconium hydroxide according to any one of claims 19 to 34, wherein contact between a solution containing raw material zirconium and a solution containing ammonium peroxodisulfate is carried out by adding the solution containing ammonium peroxodisulfate to the solution containing raw material zirconium, and the rate of addition of the solution containing ammonium peroxodisulfate is 15 to 23 mL / min.

[0067] 36. A method for producing zirconium hydroxide according to any one of claims 19 to 35, wherein the rate of adding the solution containing ammonium peroxodisulfate is 7% by volume / minute or more, when the total amount added is 100% by volume.

[0068] 37. A method for producing zirconium hydroxide according to any one of claims 19 to 36, wherein the rate of adding the solution containing ammonium peroxodisulfate is 20% by volume / minute or less, when the total amount added is 100% by volume.

[0069] 38. A method for producing zirconium hydroxide according to any one of claims 19 to 37, wherein after adding the entire amount of ammonium peroxodisulfate, the mixture is continued to be stirred, and the stirring is continued for 15 to 120 minutes.

[0070] 39. A method for producing zirconium hydroxide according to any one of claims 19 to 38, wherein after adding the entire amount of ammonium peroxodisulfate, the mixture is continued to be stirred, and the stirring is continued for 30 to 90 minutes or 45 to 75 minutes.

[0071] 40. A method for producing zirconium hydroxide according to any one of claims 19 to 39, wherein basic zirconium sulfate is generated after the above contact or after the above stirring, and the pH at this time is 0.1 to 0.5.

[0072] 41. A method for producing zirconium hydroxide according to any one of claims 19 to 40, wherein the pH is adjusted to 8.5 to 9.0 by adding a basic zirconium sulfate slurry to an alkaline solution.

[0073] 42. A method for producing zirconia powder material, comprising obtaining zirconium hydroxide by the manufacturing method described in any of items 19 to 41 above, and heat-treating the zirconium hydroxide.

[0074] 43. The method for producing zirconium hydroxide according to 42, wherein the temperature of the heat treatment is 380°C to 950°C.

[0075] 44. The method for producing zirconium hydroxide according to 43, wherein the temperature of the heat treatment is 450°C to 880°C, or 500°C to 800°C.

[0076] 45. A method for producing zirconium hydroxide according to any one of 42 to 44, wherein the heat treatment time is 0.5 to 12 hours.

[0077] 46. ​​A method for producing zirconium hydroxide according to any one of 42 to 45, wherein the time of the heat treatment is 1 to 9 hours or 2 to 6 hours.

[0078] <Example 1> ZrO ２1226 ml of an aqueous solution of zirconium oxychloride containing 60 g was placed in a beaker and heated to 92°C with a mantle heater (concentration of zirconium oxychloride: 0.397 M, amount of Zr: 0.4869 mol). Separately, an aqueous solution was prepared by dissolving 26.39 g of ammonium peroxodisulfate in 152 ml of water and heating it to 63°C (concentration of ammonium peroxodisulfate: 0.761 M, amount of S (moles of S atoms): 0.2313 mol). The aqueous solution of ammonium peroxodisulfate was added to the aqueous solution of zirconium oxychloride little by little using a liquid delivery pump while stirring with a stirrer, and the entire amount was added over 7 minutes (addition rate of aqueous solution of ammonium peroxodisulfate: 21.71 mL / min). After the addition of ammonium peroxodisulfate was complete, the mixture was stirred for one hour, and it was confirmed that the solution became cloudy and a large amount of insoluble basic zirconium sulfate precipitate was formed (the pH at this time was confirmed to be 0.1 to 0.5). Subsequently, the solution was neutralized by adding basic zirconium sulfate to ammonia water (25°C). It was confirmed that the pH was 8.5 to 9.0. After that, the solution was filtered by suction, and the extracted solid was repulped with dilute ammonia water, followed by repeated suction filtration and washing to obtain zirconium hydroxide solid. The solid was placed in a sagger and heat-treated in a muffle furnace heated to 740°C (heat treatment temperature) for 3 hours, after which it was ground in a mortar. The obtained pulverized powder was further ground in the jet mill described below to obtain zirconia powder material. The 10% deformation test force P, necking number, coefficient of variation, average particle size, and crushing time (crushing rate) of the zirconia powder material are shown in the table below.

[0079] (Jet mill conditions) Equipment: Seishin Corporation JOM-mini Internal specifications: Ceramic Sample supply rate: 4 g / min Disintegration conditions: Nozzle air pressure 0.1 MPa.

[0080] The 10% deformation test force P, necking number, and coefficient of variation / average particle size of the zirconia powder material were evaluated as follows.

[0081] (10% deformation test force P) The 10% deformation test force P was determined by measuring the secondary particle crushing strength.

[0082] Test: Compression test equipment: Shimadzu microcompression tester MCT-510 Surface detection mode: Soft surface detection mode Test force: 0.5 mN Loading speed: 0.0099 mN / sec Upper pressure indenter: Flat φ20 μm Number of tests: 5.

[0083] A minute amount of the sample was scattered onto the lower pressure plate, and a compression test was performed on each particle individually. A total of five particles were used, with five measurements performed per sample. During measurement, particles were selected that were not surrounded by other particles that could interfere with the measurement of a single particle; that is, particles that could be reliably measured individually. The strength was calculated assuming the sample shape was a perfect sphere. Although the sample deformed, it did not undergo sudden fracture, so the 10% strength (using the test force applied when a deformation of 10% of the particle diameter was applied) was calculated and used for comparison between samples. The following formula was used to calculate the deformation strength (JIS R 1639-5:2007).

[0084] C(x)=2.48P / πd ２ Here, C(x) represents the deformation strength (MPa), P represents the test force at 10% deformation (N), and d represents the particle size (mm). The test force at 10% deformation (N) is the average value of five tests.

[0085] (Necking number) The Necking number was determined by analyzing the aggregated particle structure using STEM tomography.

[0086] STEM is an abbreviation for Scanning Transmission Electron Microscopy Tomography.

[0087] Equipment: JEOL JEM-ARM200F atomic resolution analytical electron microscope Acceleration voltage: 200kV Magnification: 500,000x Tilt angle range: +78° to -78° Tilt angle step: 2° Pixel count: 512×512 pixels Pixel size: 0.781nm / pixel Reconstruction: System Frontier Composer Visualization: System Frontier Visualizer-evo, Thermo Fisher Scientific Avizo 3D Segmentation: Thermo Fisher Scientific Avizo 3D Numerical analysis: Thermo Fisher Scientific Avizo 3D Void analysis: Japan Visual Science ExFact Analysis For Polous Particles, measurement items: particle necking pathway, particle necking size, pore size, porosity, and curvature.

[0088] Sample preparation and measurement for STEM were performed as follows.

[0089] For sample preparation, an Au nanoparticle solution was dropped onto a Cu mesh with a C support film, and the sample was then ultrasonically dispersed in pure water and placed on the mesh. The Au nanoparticles were supported because they would be used as reference points during 3D reconstruction, as described later. A field of view was selected from the perspective of representing the prepared sample's morphology, and measurements were taken while continuously tilting the sample within the selected field of view under the conditions described above to obtain a continuous tilt image.

[0090] 3D reconstruction, segmentation, and image processing for STEM were performed as follows.

[0091] Dark-field images were used as the acquired two-dimensional continuous tilt images. Three-dimensional reconstructed images were obtained by image processing using Au nanoparticles in the dark-field images as a reference. Segmentation was performed based on the characteristics of the reconstructed images. First, the region with the highest brightness in the image (high-brightness region) was identified as Au nanoparticles, and the region outside the high-brightness region where particle images could be observed (medium-brightness region) was identified as zirconium oxide. Next, Au nanoparticles were excluded from the analysis because they did not represent the original information of the sample. Furthermore, to distinguish between the region inside the zirconium oxide (pore region) and the region away from the zirconium oxide region (vacuum region), segmentation was performed using the Ambient Occlusion algorithm. Next, the zirconium oxide particles were divided. First, the central area was recognized from the perspective of being away from the interface between the zirconium oxide region and the vacuum region, and a marker was set there. Subsequently, this marker was magnified using the Watershed algorithm to define the divided zirconium oxide. Also, the interfaces between adjacent divisions were defined as neckings.

[0092] Generally, segmented zirconium oxide and constrictions have complex shapes. To evaluate their sizes, the diameter (equivalent diameter) when converted to a circle of the same area was determined.

[0093] The above measurement was performed once per sample. The necking number was defined as the total number of constrictions observed in numerous particles divided by the total number of particles.

[0094] (Coefficient of Variation) The coefficient of variation was determined by analyzing the aggregated particle structure using STEM tomography. More specifically, the coefficient of variation was obtained by dividing the standard deviation σ of the distribution of primary particle diameters (nm) by the average particle size (nm), as described below.

[0095] (Average particle size) The average particle sizes listed in Table 1 were determined by observation using a transmission electron microscope. The particle size observed with a transmission electron microscope is defined as the maximum distance (maximum length) between any two points on the contour line of the observed particle (observation surface), and the average particle size can be calculated as the average value of the particle sizes observed in several to tens of fields (e.g., 3 to 30 fields). In this example, all particles that could be distinguished as primary particles in five randomly selected fields were measured, and the maximum length of each was manually measured. The arithmetic mean of these measured values ​​was then used as the average particle size. The acceleration voltage in the transmission electron microscope was typically set to 200 kV.

[0096] (Disintegration time) To determine whether the zirconia powder material could be easily disintegrated, disintegration tests were conducted on the zirconia powder material using a bead mill for each example and comparative example.

[0097] Apparatus: Labstar Mini DMS65 manufactured by Ashizawa Finetech Co., Ltd. Sample volume: 60 g Solvent: 300 g pure water Dispersant: "Kaocera 2020" 2.4 g (4 wt% zirconia weight ratio) Pretreatment: Turbine blade stirring 300 rpm x 10 min Peripheral speed: 8 m / s Discharge volume: 120 mL / min.

[0098] After bead milling, samples were taken at 0 min, 0.5 min, 1 min, 3 min, 5 min, 10 min, 20 min, and 30 min, and the particle size distribution was measured to compare the changes in particle size. The table shows the time taken until the 90% cumulative volume particle size (D90) was 1 μm or less.

[0099] The cumulative volume particle size (D90) was calculated by measuring the particle size distribution using the following equipment.

[0100] Apparatus: Microtrac MT3300EX II manufactured by Microtrac. Dispersion solvent: Hexane / Methanol = 0.2%.

[0101] Regarding the disintegration time, each example and each comparative example was evaluated three times, and the average value was taken, resulting in the disintegration times shown in Table 1.

[0102] (BET Specific Surface Area) The specific surface area was measured using the gas adsorption method (BET single-point method) with a gas adsorption type pore distribution analyzer NOVA2000 (manufactured by Yuasa Ionics). The measurement range was 0.01 m. ２ Let the amount be / g or more, and the adsorbed gas be N ２ Ar, CO ２ This was used. In addition, vacuum degassing and heating (~250°C) was performed as a pretreatment.

[0103] Example 2: Zirconia powder material was manufactured in the same manner as in Example 1, except that the heat treatment temperature was changed to 530°C, and each evaluation was performed.

[0104] Example 3: Zirconia powder material was manufactured in the same manner as in Example 1, except that the heat treatment temperature was changed to 460°C, and each evaluation was performed.

[0105] Example 4: Zirconia powder material was manufactured in the same manner as in Example 1, except that the amount of ammonium peroxodisulfate used was changed to 33.34 g, and each evaluation was performed (concentration of ammonium peroxodisulfate: 0.9612 M; amount of S (moles of S atoms): 0.2922 mol).

[0106] Example 5: Zirconia powder material was prepared in the same manner as in Example 1, except that the amount of ammonium peroxodisulfate used was changed to 44.45 g, and each evaluation was performed (concentration of ammonium peroxodisulfate: 1.2815 M; amount of S (moles of S atoms): 0.3896 mol).

[0107] Comparative Example 1: ZrO ２1226 ml of an aqueous solution of zirconium oxychloride containing 60 g was placed in a beaker and heated to 92°C using a mantle heater. Separately, an aqueous solution was prepared by dissolving 15.28 g of ammonium sulfate in 152 ml of water. The ammonium sulfate aqueous solution was added to the zirconium oxychloride aqueous solution little by little using a liquid transfer pump while stirring with a stirrer, and the entire amount was added over 7 minutes. After the addition of ammonium sulfate was completed, the solution was stirred for 1 hour and it was confirmed that the solution became cloudy and a large amount of insoluble basic zirconium sulfate precipitate was formed. After neutralization with ammonia water, the solution was filtered by suction, and the extracted solid was repulped with dilute ammonia water, filtered again by suction, and washed repeatedly to obtain a zirconium hydroxide solid. The solid was placed in a sagger and heat-treated in a muffle furnace heated to 740°C for 3 hours, and then ground in a mortar. The obtained ground powder was crushed with a jet mill and then evaluated using a bead mill.

[0108] Comparative Example 2: Zirconia powder material was manufactured in the same manner as in Comparative Example 1, except that the heat treatment temperature was changed to 530°C, and each evaluation was performed.

[0109] Comparative Example 3: Zirconia powder material was manufactured in the same manner as in Comparative Example 1, except that the heat treatment temperature was changed to 460°C, and each evaluation was performed.

[0110] Comparative Example 4: Zirconia powder material was manufactured in the same manner as in Example 1, except that the amount of ammonium peroxodisulfate used was changed to 0 g, and each evaluation was performed.

[0111] Comparative Example 5: Zirconia powder material was manufactured in the same manner as in Example 1, except that the amount of ammonium peroxodisulfate used was changed to 11.11 g, and each evaluation was performed.

[0112] Comparative Example 6: Zirconia powder material was prepared in the same manner as in Example 1, except that the amount of ammonium peroxodisulfate used was changed to 22.22 g, and each evaluation was performed.

[0113] Comparative Example 7: Zirconia powder material was manufactured in the same manner as in Example 1, except that the amount of ammonium peroxodisulfate used was changed to 55.56 g, and each evaluation was performed.

[0114] Furthermore, the mass percentage of zirconia contained in the zirconia powder material was 99.80 ± 0.15% in both the examples and comparative examples, and trace amounts of hafnium oxide were also present.

[0115]

[0116] This application is based on Japanese Patent Application No. 2025-040977, filed on 14 March 2025, the disclosures thereof being incorporated herein by reference in their entirety.

Claims

1. ZrO ２ A zirconia powder material consisting of 95% by mass or more of zirconia and the remainder being unavoidable impurities, satisfying at least one of the following requirements: Requirement (1): The 10% deformation test force P (mN) in the microcompression strength test is in the range of 0 < P ≤ 0.012; Requirement (2): The number of neckings formed by primary particles by STEM tomography analysis is less than 3; Requirement (3): The coefficient of variation in the particle size distribution of primary particles by STEM tomography analysis is 0.35 or less, and the average particle size is 25 nm or more.

2. The zirconia powder material according to claim 1, satisfying the above (1).

3. The zirconia powder material according to claim 1, satisfying the above (2).

4. The zirconia powder material according to claim 2, satisfying the above (2).

5. A zirconia powder material according to any one of claims 1 to 4, satisfying the above (3).

6. A method for producing zirconium hydroxide, characterized by contacting a solution containing raw material zirconium with a solution containing ammonium peroxodisulfate, wherein the reaction is carried out such that the ratio of the amount of S in ammonium peroxodisulfate to the amount of Zr in the raw material zirconium is S / Z, and the following condition is satisfied: 0.460 ≤ S / Z ≤ 0.

800.

7. The method for producing zirconium hydroxide according to claim 6, characterized in that the reaction satisfies the following: 0.460 ≤ S / Z ≤ 0.

600.

8. The method for producing zirconium hydroxide according to claim 6, characterized in that the temperature of the solution containing ammonium peroxodisulfate is adjusted to 50 to 65°C before contact.

9. A method for producing a zirconia powder material, characterized by obtaining zirconium hydroxide by the manufacturing method described in any one of claims 6 to 8, and heat-treating the zirconium hydroxide.

Images