Powder for producing sintered body and method for producing same, and ceramic sintered body

Abstract

The present invention addresses the problem of providing: a powder for producing a sintered body, with which it is possible to produce a ceramic sintered body that has excellent magnetic characteristics, a small grain size, and a high degree of spinel synthesis; a method for producing a powder for producing a sintered body; and a ceramic sintered body. A powder for producing a sintered body according to the present invention comprises a spinel structure represented by the compositional formula MeO∙Fe2O3. With respect to the powder for producing a sintered body, the metal element Me is at least one element that is selected from the group consisting of Zn, Ni, Cu, Mn, Mg, Co and rare earth elements, the crystallite size of the powder for producing a sintered body is 30-100 nm as determined by measurement based on X-ray diffractometry, and the coefficient of variation of the crystallite size as determined from an observation image obtained by observing the powder for producing a sintered body using a scanning electron microscope is not more than 30%.

Description

Powder for manufacturing sintered bodies and method for manufacturing the same, and ceramic sintered bodies

[0001] This invention relates to a powder for manufacturing sintered bodies, a method for manufacturing the same, and ceramic sintered bodies.

[0002] Conventionally, in order to improve the performance of ceramic electronic components, the type, blending amount, and particle size of composite oxides used as raw materials have been investigated. Patent Document 1 describes a technology relating to ferrite powder, a method for producing ferrite powder, and a method for producing an inductor by firing a molded body obtained using ferrite powder.

[0003] Patent No. 5498756

[0004] In electronic components constructed using ceramics, the demand for higher performance, reliability, and miniaturization is increasing, making the control of the internal structure of ceramic sintered bodies increasingly important. Traditionally, structural control of ceramic sintered bodies has primarily focused on the particle size and variability of the raw materials used, the elements and amounts of additives, and crystallinity. However, despite long-term research, these technologies have limitations in significantly improving performance, reliability, and precision at the manufacturing level.

[0005] The object of the present invention is to provide a powder for manufacturing sintered bodies that can produce ceramic sintered bodies with excellent magnetic properties, small grain size, and high spinel composition. Another object of the present invention is to provide a method for manufacturing the powder for manufacturing sintered bodies and a ceramic sintered body.

[0006] As a result of diligent research, the inventors have found that the above problems can be solved by adopting the following configuration.

[0007] In other words, the present invention relates to the following [1] to [7]. [1] Composition formula MeO・Fe ２ O ３A powder for manufacturing a sintered body having a spinel structure represented by , wherein the metal element Me is at least one selected from the group consisting of Zn, Ni, Cu, Mn, Mg, Co and rare earth elements, the crystallite size of the powder for manufacturing a sintered body determined by measurement based on X-ray diffraction is 30 to 100 nm, and the coefficient of variation of the crystallite size determined from observation images of the powder for manufacturing a sintered body obtained using a field emission scanning electron microscope is 30% or less. [2] The powder for manufacturing a sintered body according to [1], wherein the content of Na relative to the total mass of the powder for manufacturing a sintered body is less than 30 ppm by mass, the content of Cl relative to the total mass of the powder for manufacturing a sintered body is less than 30 ppm by mass, and the content of S relative to the total mass of the powder for manufacturing a sintered body is less than 30 ppm by mass. [3] The sintered body manufacturing powder according to [1] or [2], wherein the coefficient of variation of the metal element Me, determined by elemental mapping measurement based on the SEM-EDS method, is 30.0% or less. [4] The sintered body manufacturing powder according to any one of [1] to [3], wherein the cumulative intensity ratio of the metal element Me, determined by the elemental mapping measurement, is 0.10% or less. [5] A method for manufacturing the sintered body manufacturing powder according to any one of [1] to [4], wherein the sintered body manufacturing powder is manufactured by a liquid phase method. [6] The method for manufacturing the sintered body manufacturing powder according to [5], comprising: a precipitate generation step of reacting a salt of the metal element Me, a salt of Fe, and an alkali to precipitate a precursor containing the metal elements Me and Fe; and a heat treatment step of heat treating the precursor to obtain the sintered body manufacturing powder. [7] A ceramic sintered body obtained by sintering the sintered body manufacturing powder according to any one of [1] to [4]. [8] A ceramic sintered body obtained by sintering a mixture of the sintered body manufacturing powder described in any of [1] to [4] and a ceramic material. [9] A ceramic sintered body described in [7] or [8] that is an electronic component.

[0008] According to the present invention, it is possible to provide a powder for manufacturing sintered bodies that can produce ceramic sintered bodies with excellent magnetic properties, small grain size, and high spinel composition. Furthermore, according to the present invention, it is possible to provide a method for manufacturing the powder for manufacturing sintered bodies and a ceramic sintered body.

[0009] In this specification, numerical ranges expressed using "~" mean a range that includes the numbers before and after "~" as the lower and upper limits. In this specification, each component may be made using one substance alone or using two or more substances in combination. Here, when two or more substances are used in combination for each component, the content of that component refers to the total content of the substances used in combination, unless otherwise specified.

[0010] [Powder for Sintered Body Production] The powder for sintered body production of the present invention (hereinafter also simply referred to as "this powder") has the composition formula MeO・Fe ２ O ３ It has a spinel structure represented by . Me represents at least one metallic element selected from the group consisting of Zn, Ni, Cu, Mn, Mg, Co and rare earth elements. Furthermore, the crystallite size of this powder, as determined by measurement based on X-ray diffraction, is 30 to 100 nm, and the coefficient of variation of the crystallite size, as determined from observation images obtained by observing this powder using a field emission scanning electron microscope, is 30% or less.

[0011] This powder is used, for example, in the manufacture of ceramic sintered bodies (hereinafter simply referred to as "sintered bodies") used as ceramic electronic components, in order to precisely control the performance and reliability of the sintered bodies. More specifically, as will be described later, by using this powder as a ceramic material for manufacturing sintered bodies and then molding and firing them, it is possible to manufacture ceramic sintered bodies with excellent magnetic properties, small grain size, and high spinel composition.

[0012] The exact reason why this powder enables the production of ceramic sintered bodies with excellent magnetic properties, small grain size, and high spinel content is still unknown, but the inventors speculate that it is due to the following mechanism. The spinel structure contained in the sintered body is considered to be one of the factors that affect the performance of the sintered body, such as its magnetic properties and reliability. It is presumed that if the grain size is large or the spinel content is low in the sintered body, the magnetic properties and reliability of the sintered body will be greatly impaired. Crystal phases such as the spinel structure in the sintered body are generated and grown in the thermal reactions of each oxide during heat treatment processes such as molding and firing of the ceramic material, and are thought to differ depending on the composition and distribution of oxides in the ceramic material, the molding method, the sintering method, and the size of the sintered body. Conventionally, a mixture obtained by blending two or more oxide powders of single metal elements has been used to produce spinel-type ferrite. In this case, since the generation and growth of the crystal phase proceeds separately for each particle with a significantly different composition during the heat treatment process, it is thought that variations in composition distribution and crystal phase size occur in the manufactured sintered body, leading to a decrease in performance such as magnetic properties. In contrast, when manufacturing a sintered body using this powder, since the crystallite size of this powder is within a predetermined range, the size of the crystalline phase generated and grown in the heat treatment process can be made smaller. Furthermore, since the coefficient of variation of the crystallite size is below a predetermined value, the generation and growth of the crystalline phase using this powder as a seed crystal in the heat treatment process becomes more uniform, and variations in the composition, distribution, and size of the crystalline phase in the sintered body are significantly suppressed, resulting in the production of a sintered body with a high degree of spinel composition. Thus, it is believed that by using this powder, it is possible to manufacture a sintered body with excellent magnetic properties, a small grain size, and a high degree of spinel composition.

[0013] The present invention will be described in more detail below. Furthermore, when a sintered body is produced by molding and firing a mixture of powder for sintered body production and ceramic material, if any of the magnetic properties, grain size, or spinel composite degree of the resulting sintered body are superior, this is also referred to as "the effects of the present invention are superior."

[0014] This powder has the composition formula MeO·Fe ２ O ３ It has a spinel structure represented by the formula shown above. The metal element Me is at least one selected from the group consisting of Zn, Ni, Cu, Mn, Mg, Co, and rare earth elements. Examples of rare earth elements included in the metal element Me are Sc, Y, and lanthanides, with Sc or Y being preferred. The metal element Me is preferably at least one selected from the group consisting of Ni, Cu, Zn, Mn, Mg, and rare earth elements, and any one or more of Ni, Cu, and Zn are more preferred. In the above composition formula, the metal element Me exists in cationic form. The spinel structure of this powder may be doped.

[0015] The metallic element Me may be used alone or in combination of two or more types. The content of metallic element Me is preferably 15 to 40% by mass, and more preferably 20 to 35% by mass, based on the total mass of the powder. The content of Fe is preferably 30 to 60% by mass, and more preferably 35 to 55% by mass, based on the total mass of the powder.

[0016] This powder is, for example, a composite oxide of the metal elements Me and Fe. That is, in this powder, the remainder after removing the metal elements Me and Fe may be oxygen atoms. The oxygen atom content varies depending on the type of metal element Me contained in this powder, but may be, for example, 10 to 35% by mass or 15 to 30% by mass.

[0017] <Crystallite Size> The crystallite size of this powder, as determined by measurement based on X-ray diffraction (XRD), is 30 to 100 nm. A crystallite size of 40 to 90 nm is preferred for this powder in terms of achieving superior effects of the present invention.

[0018] <Coefficient of Variation of Crystallite Size> In addition, the coefficient of variation of crystallite size (hereinafter also simply referred to as "coefficient of variation of crystallite size") obtained from observation images obtained by observing the powder for manufacturing the sintered body using a scanning electron microscope is 30% or less. It is presumed that by manufacturing a sintered body using this powder with a coefficient of variation of crystallite size of 30%, the variation in the composition, distribution, and size of the crystalline phase in the sintered body is greatly suppressed, and a sintered body with a high degree of spinel synthesis is produced. In this powder, the coefficient of variation of crystallite size is preferably 25% or less. The lower limit of the coefficient of variation of crystallite size is not particularly limited, and the coefficient of variation of crystallite size of this powder may be 0%.

[0019] This document describes in detail the method for measuring the coefficient of variation of crystallite size of oxide powders, including this powder. First, the oxide powder A is processed into pellets by pressure molding. The obtained pellets are observed at a magnification of 50,000x using an FE-SEM (field emission scanning electron microscope) to obtain observation images. 200 oxide powders are randomly selected from the obtained observation images, and the equivalent diameter of each circle is measured. From the obtained measurement values, the arithmetic mean AM (unit: nm) and standard deviation σ (unit: nm) are calculated. The coefficient of variation of crystallite size is a value calculated as the ratio of the standard deviation σ to the arithmetic mean AM (σ / AM), and is expressed as a percentage (%).

[0020] <Coefficient of Variation of Metal Element Me> In this powder, for superior effects of the present invention, the coefficient of variation of metal element Me (hereinafter also referred to as "coefficient of variation of metal element Me") determined by elemental mapping measurement based on the SEM-EDS method (scanning electron microscope-energy dispersive X-ray spectroscopy) is preferably 30.0% or less, and more preferably 25.0% or less. A smaller coefficient of variation of metal element Me indicates a more uniform distribution of metal element Me in the powder. The lower limit of the coefficient of variation of metal element Me is not particularly limited and may be 5.0% or more, or 10.0% or more. When two or more metal elements are included in the powder as metal element Me, for example, the statement "the coefficient of variation of metal element Me is 30.0% or less" means that the coefficient of variation of each metal element is 30.0% or less. The meaning of the preferred range above is the same.

[0021] The coefficient of variation of the metallic element Me in oxide powder is measured by the following method. First, a sample of oxide powder is pressure-molded to produce a pellet with a diameter of 20 mm. After Pt deposition is applied to the prepared pellet, elemental mapping measurement of the metallic element Me is performed using the SEM-EDS method. The SEM-EDS measurement conditions are an acceleration voltage of 15 kV, a process time of 2, a field of view of 3, and a magnification of 1000x. The average intensity and standard deviation σ of the metallic element Me are determined for all measurement points in the elemental mapping image obtained by the elemental mapping measurement. The obtained standard deviation σ is divided by the average intensity and expressed as a percentage to obtain the coefficient of variation of the metallic element Me (coefficient of variation of elemental distribution) (unit: %).

[0022] <Integrated Intensity Ratio of Metal Element Me> In this powder, the integrated intensity ratio of metal element Me (hereinafter also simply referred to as "integrated intensity ratio") determined by elemental mapping measurement based on the SEM-EDS method is preferably 0.10% or less, and more preferably 0.05% or less, in terms of achieving superior effects of the present invention. A smaller integrated intensity ratio means that the metal element Me is more uniformly distributed in the powder. By using a powder with an integrated intensity ratio within the above range, a sintered body with a higher spinel synthesis degree and higher reliability can be manufactured. The lower limit of the integrated intensity ratio is not particularly limited and may be 0% or more, or 0.01% or more.

[0023] The cumulative intensity ratio is measured by the following method. First, elemental mapping measurements are performed on the metallic element Me using the SEM-EDS method, similar to the method for measuring the coefficient of variation of the metallic element Me. A histogram is created from the intensity of the metallic element Me measured at each measurement point of the metallic element Me mapping, with the horizontal axis representing the intensity at each measurement point and the vertical axis representing the frequency. The threshold value is obtained by adding 10 times the square root of the intensity of the most frequent value to the intensity of the most frequent value. The cumulative intensity ratio (in %) is calculated for the total intensity (total cumulative) in the region above this threshold.

[0024] In this powder, it is preferable that, in the diffraction pattern obtained by powder X-ray diffraction analysis of this powder, the peak originating from the spinel structure is detected as the main peak, and the peaks originating from crystal structures other than the spinel structure (hereinafter also referred to as "other crystal structures") are not detected or are very small compared to the peak originating from the spinel structure.

[0025] In the diffraction pattern of this powder obtained by powder X-ray diffraction analysis, it is preferable that no peaks originating from other crystal structures are detected, or that the peak intensities of any peaks originating from other crystal structures are 0.10% or less (more preferably 0.05% or less) of the peak intensity of the peak with the highest peak intensity among the peaks originating from the spinel structure. It is particularly preferable that no peaks originating from other crystal structures are detected in the diffraction pattern of this powder obtained by powder X-ray diffraction analysis.

[0026] In this powder, it is preferable that the content of elements other than Fe, the metallic element Me, and O is low, as this enhances the effects of the present invention. In particular, the content of Na relative to the total mass of the powder is preferably less than 50 ppm by mass, and more preferably less than 30 ppm by mass. Furthermore, the content of Cl relative to the total mass of the powder is preferably less than 50 ppm by mass, and more preferably less than 30 ppm by mass. Moreover, the content of S relative to the total mass of the powder is preferably less than 50 ppm by mass, and more preferably less than 30 ppm by mass. In particular, in this powder, it is preferable that the content of Na relative to the total mass of the powder, the content of Cl relative to the total mass of the powder, and the content of S relative to the total mass of the powder are all within the above preferred ranges. The respective contents of Na, Cl, and S contained in the oxide powder are measured by the method described in the examples below.

[0027] <Method for Manufacturing This Powder> One possible method for manufacturing this powder is the liquid phase method. The liquid phase method is a method for manufacturing this powder from raw materials containing the metal element Me in the presence or in a liquid, and this powder can be manufactured by a known liquid phase method.

[0028] The powder is preferably synthesized by a liquid-phase method. By synthesizing this powder by a liquid-phase method, a powder for manufacturing sintered bodies having a uniform spinel structure can be easily produced. A uniform spinel structure means that in the diffraction pattern obtained by the above-mentioned powder X-ray diffraction analysis, the peak originating from the spinel structure is detected as the main peak, and the peaks originating from other crystal structures are not detected or are very small. Furthermore, by synthesizing by a liquid-phase method, variations in shape are suppressed, and a powder for manufacturing sintered bodies with a suppressed coefficient of variation of crystallite size can be easily produced. Moreover, because variations in shape are suppressed in the powder synthesized by a liquid-phase method, the surface shape and internal structure are uniform, and a sintered body with a large contact area with the internal electrode can be stably produced. In this way, by using this powder synthesized by a liquid-phase method, a more reliable sintered body can be easily produced.

[0029] A method for producing this powder by a liquid-phase method includes, for example, a precipitate formation step in which salts of the metal elements Me and Fe are reacted with an alkali to precipitate a precursor containing the metal elements Me and Fe, and a heat treatment step in which the precursor is heat-treated to obtain the powder. In particular, a method in which salts of the metal elements Me and Fe are reacted with an alkali in an aqueous buffer solution containing salts (excluding salts of the metal elements Me and Fe) in the precipitate formation step (hereinafter also referred to as "production method A") is preferred.

[0030] In manufacturing method A, the salt used in the buffer aqueous solution is not particularly limited as long as it does not contain either the metal elements Me or Fe, and examples include carbonates, bicarbonates, sulfates, chlorides, acetates, and nitrates. Specific examples of the above salts include ammonium bicarbonate (bisulfite), sodium carbonate, sodium bicarbonate (baking soda), ammonium nitrate, sodium chloride, ammonium chloride, sodium sulfate, ammonium sulfate, sodium acetate, and ammonium acetate, with ammonium bicarbonate, sodium bicarbonate, or ammonium acetate being preferred. In the precipitate formation step and the stirring curing described later, the temperature of the buffer aqueous solution is preferably kept below 45°C, and more preferably below 25°C.

[0031] The salts of the metal element Me and Fe used in manufacturing method A are not particularly limited, but salts with good water solubility are preferred, and at least one selected from the group consisting of nitrates, chlorides, sulfates, and acetates, and hydrates thereof, is preferred. In the precipitation step, the salts of the metal element Me and Fe are preferably used in aqueous solution form, and it is more preferable to dropwise add the aqueous solution containing the salts of the metal element Me and Fe to the buffer aqueous solution. The aqueous solution containing the salts of the metal element Me and Fe may contain organic acids. Examples of organic acids include tartaric acid, lactic acid, citric acid, malic acid, fumaric acid, and acetic acid.

[0032] The alkali used in manufacturing method A is not particularly limited, but suitable examples include sodium hydroxide and potassium hydroxide. When the alkali is used in aqueous solution form, ammonium hydroxide may also be used. In the precipitate formation step, it is preferable that the alkali is also used in aqueous solution form.

[0033] In the precipitate formation process, while adding aqueous solutions containing salts of the metal elements Me and Fe dropwise, it is preferable to add an alkaline aqueous solution to the buffer aqueous solution to maintain a constant pH of the buffer aqueous solution. The pH of the buffer aqueous solution that is maintained at a constant value is preferably 6.0 or higher, more preferably 7.0 or higher, preferably 10.0 or lower, more preferably 9.0 or lower, and even more preferably 8.0 or lower.

[0034] In manufacturing method A, it is preferable to further include a step of stirring and curing the precursor generated as a precipitate between the precipitate generation step and the heat treatment step. The stirring and curing time is preferably 1 hour or more, more preferably 5 hours or more, even more preferably 10 hours or more, and particularly preferably 15 hours or more. When the stirring and curing time is longer than the above lower limit, the density of the molded body and sintered body will be higher and more stable compared to when the stirring and curing time is shorter, provided that the content of the metal elements Me and Fe is the same. Also, when the stirring and curing time is longer than the above lower limit, it is thought that the flake shape, which is the characteristic shape of layered hydroxide, will disappear due to repeated collisions caused by stirring, and it will easily become granular. The upper limit of the stirring and curing time is not particularly limited and depends on the concentration of the reaction solution and the stirring force, but for example it is 32 hours or less, and 24 hours or less is preferable.

[0035] The powder is obtained by a heat treatment step in which the precursor obtained by the precipitate formation reaction is heat-treated. The heat treatment temperature is preferably 250°C or higher, and more preferably 300°C or higher. If the heat treatment temperature is higher than the lower limit, decarboxylation and dehydration during firing can be suppressed, and sintering can be further promoted. Also, the higher the heat treatment temperature, the more dense secondary particles are formed by necking of primary particles. On the other hand, the heat treatment temperature is preferably 1200°C or lower, and more preferably 1000°C or lower. If the heat treatment temperature is lower than the upper limit, the formation of linked grains, in which primary particles are bonded together, can be suppressed. Linked grains grow quickly, and the formation of linked grains leading to the formation of larger sintered particles is a well-known phenomenon known as Ostwald growth. If the heat treatment temperature is below the upper limit, the formation of linked grains is suppressed, and it is thought that the particle size of the sintered body becomes more uniform. The heat treatment time in the heat treatment step is not particularly limited, but is preferably 2 to 12 hours, and more preferably 4 to 10 hours.

[0036] [Sintered Body] This powder is used in the manufacture of sintered bodies (ceramic sintered bodies). A method for manufacturing a sintered body using this powder includes, for example, a molding step of molding a raw material powder containing this powder to obtain a molded body, and a sintering step of sintering the molded body to obtain a sintered body.

[0037] The raw material powder may be the powder alone or a mixture containing the powder and a ceramic material, but it is preferable to use the powder alone. As the ceramic material, known materials used in the manufacture of ceramic sintered bodies can be used, and examples include metal oxides containing one or more metals such as iron (Fe), nickel (Ni), copper (Cu), zinc (Zn), bismuth (Bi), cobalt (Co), and manganese (Mn). The metal oxide may also be a composite oxide containing two or more of the above metals. The content of the powder in the above mixture is not particularly limited, and is, for example, 30 to 100% by mass relative to the total content of the ceramic material and the powder.

[0038] The manufacturing method of the sintered body including the forming process and the sintering process is not particularly limited, and known manufacturing methods using ceramic materials can be applied. The raw material powder used for forming may be subjected to a crushing treatment by a bead mill as necessary. Further, the raw material powder may be manufactured by granulation using a spray dryer.

[0039] Examples of the sintered body manufactured using this powder include a sintered body obtained by sintering this powder and a sintered body obtained by sintering a mixture of this powder and a ceramic material. The sintered body is preferably a solid solution containing the metal elements Me and Fe. In the sintered body, depending on the content and / or firing temperature of the metal elements Me and Fe, they may form compounds such as oxides and exist at the grain boundaries as secondary phases.

[0040] The sintered body manufactured using this powder is used as a magnetic material, and among them, it is preferably used as a core material constituting electronic components such as inductors and transformers. As described above, the sintered body manufactured using this powder has excellent magnetic properties, a small grain size, and a high spinel synthesis degree. Further, by using this powder, a sintered body with suppressed variation in grain size can be manufactured. For example, since the number of crystal grains that can be arranged between electrodes can be ensured even when the grain size is small and the distance between electrodes is narrow, by using the sintered body manufactured using this powder as the core material of a multilayer chip inductor, the multilayer chip inductor can be further miniaturized. Furthermore, since it is a sintered body with a high spinel synthesis degree and high homogeneity, it is possible to suppress a decrease in life under high temperature and high humidity, and high-performance and highly reliable electronic components can be obtained. By using the sintered body manufactured using this powder in this way, ceramic electronic components that are small, high-performance, and highly reliable can be realized. Examples of uses of the sintered body other than the above electronic components include magnets, recording materials, and various toners.

[0041] Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to the following examples.

[0042] [Inventive Example 1] <Manufacture of Powder for Sintered Body Production by Liquid Phase Method> Nickel(II) nitrate hexahydrate, zinc nitrate hexahydrate, copper(II) nitrate trihydrate, and iron(III) nitrate nonahydrate (all manufactured by Kishida Chemical Co., Ltd.) were prepared as salts of metal element Me, ammonium bicarbonate (manufactured by Kishida Chemical Co., Ltd.) was prepared as a carbonate, and 7.4 mol / L aqueous ammonia (manufactured by Kishida Chemical Co., Ltd.) was prepared as an alkali.

[0043] Nickel(II) nitrate hexahydrate, zinc nitrate hexahydrate, copper(II) nitrate trihydrate, and iron(III) nitrate nonahydrate were dissolved in 1 L of pure water to prepare a mixed aqueous solution. The addition amounts of each component were adjusted so that the composition of the obtained powder A would be the composition shown in Table 1 below.

[0044]

[0045] 500 mL of a 0.8 M aqueous ammonium bicarbonate solution was placed in a 2 L beaker. A pH electrode for pH control was inserted into the aqueous ammonium bicarbonate solution. The above mixed aqueous solution was dropped into the aqueous ammonium bicarbonate solution being stirred by a rotor with a rotation speed set at 500 rpm at a rate of 1 L / h.

[0046] In order to prevent the pH of the aqueous ammonium bicarbonate solution from decreasing due to the dropping of the acidic mixed aqueous solution, 7.4 mol / L aqueous ammonia was dropped into the aqueous ammonium bicarbonate solution by a liquid feed pump that was on / off controlled by a pH controller (TDP-51 manufactured by Dongxing Chemical Research Institute). Thereby, the pH of the reaction solution in the beaker was maintained at a constant value of 7.0 during the dropping of the mixed aqueous solution. Thus, a precipitate was generated by the precipitation reaction. After all of the mixed aqueous solution was dropped and the generation of the precipitate by the precipitation reaction was completed, the generated precipitate was subjected to stirring and aging for 20 hours using a rotor with a rotation speed set at the same 500 rpm as during the precipitation reaction to obtain a slurry of precursor A containing nickel, zinc, copper, and iron.

[0047] The slurry, after stirring and curing, was separated into solid and liquid components by suction filtration to obtain the solid component. The obtained solid component was washed with water to remove ammonia, chlorine, nitric acid, etc. The washing of the solid component was continued until the electrical conductivity of the filtrate was 5 ms / m or less. The washed solid component was vacuum dried in a vacuum dryer at 40°C for 20 hours. In this way, a dried powder of precursor A containing nickel, zinc, copper, and iron was obtained.

[0048] Measurement of thermal loss using a TG-DTA instrument (STA 2500 Regulus, manufactured by Netch Japan) confirmed the heating temperature at which carbonate groups, hydroxyl groups, and adsorbed water completely detached from precursor A and oxides were formed. Furthermore, measurements using an X-ray fluorescence analyzer (ZSX Prius 4, manufactured by Rigaku Corporation) confirmed that the composition ratio of nickel, zinc, copper, and iron in precursor A was as specified in the initial calculation. Analysis of the filtrate revealed that the precipitate yield was over 90% by mass.

[0049] The dried powder of the obtained precursor A was placed in an alumina crucible and heat-treated at 420°C in an air atmosphere to perform decarboxylation and dehydration. In the heat treatment, the temperature was raised at a rate of 5°C / min and held at 420°C for 6 hours, after which it was cooled by natural cooling to obtain powder A for sintering body production.

[0050] Analysis of the obtained powder A using a powder X-ray diffractometer (Brooker, D8 ADVANCE) revealed that a main peak originating from the spinel structure was detected in the obtained X-ray diffraction pattern, while no peaks originating from other crystal structures were detected. Evaluation of the crystallite size from the X-ray diffraction pattern showed that the crystallite size of the obtained powder A was 50 nm. Furthermore, measurement using the above method revealed that the coefficient of variation of the crystallite size of powder A was 19%. Similar to precursor A, measurement using a fluorescence X-ray analyzer confirmed that the composition of powder A is as shown in Table 1.

[0051] [Comparative Example 1] <Production of powder for sintered body manufacturing by solid-phase method> As Comparative Example 1, powder for sintered body manufacturing was produced by a solid-phase method. Specifically, NiO (particle size 1.2 μm), ZnO (particle size 0.7 μm), CuO (particle size 1.1 μm), Fe ２ O ３ Using an oxide with a particle size of 1.2 μm, mixing and grinding was carried out for 24 hours under ion-exchanged water. The resulting mixed powder was then heat-treated by heating at 700°C for 2 hours to obtain powder C.

[0052] In the mixing and grinding process, the oxides were mixed and ground in a wet environment using deionized water with a bead mill. Zirconia media with a particle size of 0.05 to 0.15 mm was used as the grinding media, and the resulting pulverized material was sized so that the particle size was within the range of 0.2 to 0.9 μm. In addition, in the mixing and grinding process, to ensure dispersibility in a wet environment, a polyacrylic acid-based dispersion solvent in an amount of 5% by mass relative to the oxides was added to the deionized water.

[0053] A mixture of the pulverized composite oxide obtained by mixing and grinding, and a solvent was filtered by suction. The filtrate was dried at a temperature below 100°C, and then processed into a powder using an ultrasonic sieve to obtain a mixed powder. The obtained mixed powder of composite oxides was heat-treated using a rotary kiln. In the heat treatment, in order to obtain a uniform and stable powder, the heat treatment temperature was set to 700°C, which is lower than the crystallization temperature, and the mixed powder was held at 700°C for 2 hours. The powder obtained by the heat treatment was again ground and dried using a bead mill to obtain powder C. The particle size of powder C was in the range of 0.4 to 0.7 μm. The crystallite size of the obtained powder C was evaluated from the X-ray diffraction pattern and found to be 650 nm. Furthermore, the coefficient of variation of the crystallite size of powder C, as measured according to the above method, was 33%.

[0054] Similar to Invention Example 1, powder C was analyzed using an X-ray fluorescence analyzer, and it was confirmed that the composition ratio of nickel, zinc, copper, and iron contained in powder C was the same as that of powder A produced in Invention Example 1. Also, similar to Invention Example 1, powder C was subjected to powder X-ray diffraction analysis. As a result, a stable crystalline phase could not be obtained in powder C, and in addition to the peak originating from the spinel structure, many peaks with high peak intensity originating from other crystalline structures were detected. Therefore, the powder X-ray diffraction analyzer could not identify the crystalline structure to which powder C belonged, and the crystalline structure of powder C was determined to be "Unknown".

[0055] <Manufacturing of Molded Articles> Using powder A obtained in Invention Example 1 and powder C obtained in Comparative Example 1, molded articles and sintered articles were manufactured by the following method. Polyvinyl alcohol in an amount equivalent to 1% by mass per powder was added to each of powders A and C, and the resulting mixtures were granulated using a 300-mesh sieve. Each mixed powder after granulation was press-molded at a pressure of 100 MPa to produce annular molded articles with an outer diameter of 20 mm, an inner diameter of 14 mm, and a thickness of 3 mm.

[0056] <Manufacturing of Sintered Body> The manufactured annular molded body was fired in an air atmosphere to obtain an annular sintered body. The firing temperature (maximum temperature) was 900°C. The holding time at the firing temperature was 3 hours, the heating rate was 200°C / h, and cooling was performed by furnace cooling. Hereinafter, the sintered body manufactured using powder A will also be referred to as sintered body A (Inventive Example 1), and the sintered body manufactured using powder C will also be referred to as sintered body C (Comparative Example 1).

[0057] <Measurement> For each of the powders, powder A of Invention Example 1 and powder C of Comparative Example 1, the coefficient of variation and cumulative intensity ratio of the metal element Me (Ni, Cu, and Zn) were measured according to the method described above. The measurement results are shown in Table 2 below.

[0058] Also, the contents of Na, Cl, and S contained in Powder A of Invention Example 1 were measured according to the following method using fluorescent X-ray analysis. Powder A was processed into a pellet form by pressure molding in advance. Using a fluorescent X-ray analyzer (ZSX Prius 4 manufactured by Rigaku Corporation), the intensity of the fluorescent X-ray corresponding to each target element was measured from the pellet sample, and the content of each target element was quantified by the fundamental parameter method (FP method) from the obtained intensities. In consideration of the variation in the measurement results, 20 pellet samples were prepared, and the maximum value of the 20 measurement results was confirmed. As a result, with respect to the total mass of Powder A, the content of Na was less than 25 mass ppm, the content of Cl was less than 10 mass ppm, and the content of S was less than 5 mass ppm.

[0059] <Evaluation> For each of Sintered Body A and Sintered Body C, magnetic properties (initial magnetic permeability), spinel synthesis degree, and grain size were evaluated. The results of each evaluation are shown in Table 2 below.

[0060] (Initial magnetic permeability) An inductor was manufactured by winding an insulated copper wire around the entire circumference of an annular sintered body (ferrite core) for one layer. Using an impedance analyzer, the initial magnetic permeability (unit: H) of the inductor at 100 kHz was measured.

[0061] (Grain size) For each sintered body, the grain size (crystallite size) of the crystal grains having a spinel structure was measured using a FE-SEM (field emission scanning electron microscope). Specifically, the sintered body was observed at a magnification of 3000 times for 50 fields of view using a FE-SEM. From the images obtained by the observation, 20 crystal grains having a spinel structure were selected, the equivalent circle diameter of each was measured, and the obtained measurement values were averaged arithmetically to calculate the grain size (unit: μm) of the crystal grains having a spinel structure. Also, from the obtained measurement values, the standard deviation σ of the grain size was calculated.

[0062] (Spinel synthesis degree) For each sintered body, an analysis based on the X-ray diffraction method (XRD) was performed. In the obtained X-ray diffraction pattern, Fe ２ O ３The degree of spinel composition (%) was calculated using the following formula, based on the peak intensity IFe104 of the peak corresponding to the (104) plane and the peak intensity Isp311 of the peak corresponding to the (311) plane of the spinel structure: Spinel composition = Isp311 / (IFe104 + Isp311) × 100 (%)

[0063]

[0064] As shown in the table above, the sintered body produced using powder A of Invention Example 1 was found to have a higher initial permeability, smaller grain size, reduced grain size variation, and a higher spinel composition compared to the sintered body C produced using powder C of Comparative Example 1. To meet the needs for miniaturization and high performance of electronic components, it is required to reduce and uniformize the grain size while maintaining magnetic properties such as initial permeability, and to improve the proportion of the spinel crystal phase. In response to this, the sintered body produced using powder A of Invention Example 1, which has a spinel structure, a crystallite size in the range of 30 to 100 nm for sintered body production, and a coefficient of variation of crystallite size of 30% or less, was found to have significantly improved properties that are important for realizing high performance, high reliability, and miniaturization of ceramic electronic components.

Claims

1. Composition formula MeO・Fe ２ O ３ A powder for manufacturing a sintered body having a spinel structure represented by , wherein the metal element Me is at least one selected from the group consisting of Zn, Ni, Cu, Mn, Mg, Co and rare earth elements, the crystallite size of the powder for manufacturing a sintered body determined by measurement based on X-ray diffraction is 30 to 100 nm, and the coefficient of variation of the crystallite size determined from an observation image obtained by observing the powder for manufacturing a sintered body using a field emission scanning electron microscope is 30% or less.

2. The sintered body manufacturing powder according to claim 1, wherein the content of Na relative to the total mass of the sintered body manufacturing powder is less than 30 ppm by mass, the content of Cl relative to the total mass of the sintered body manufacturing powder is less than 30 ppm by mass, and the content of S relative to the total mass of the sintered body manufacturing powder is less than 30 ppm by mass.

3. The powder for manufacturing a sintered body according to claim 1 or 2, wherein the coefficient of variation of the metallic element Me, determined by elemental mapping measurement based on the SEM-EDS method, is 30.0% or less.

4. The powder for manufacturing a sintered body according to claim 3, wherein the cumulative intensity ratio of the metal element Me determined by the elemental mapping measurement is 0.10% or less.

5. A method for producing a sintered body powder according to claim 1 or 2, wherein the sintered body powder is produced by a liquid phase method.

6. A method for producing powder for sintered bodies according to claim 5, comprising: a precipitate formation step of reacting a salt of the metal element Me, a salt of Fe, and an alkali to precipitate a precursor containing the metal elements Me and Fe; and a heat treatment step of heat treating the precursor to obtain powder for producing sintered bodies.

7. A ceramic sintered body obtained by sintering the powder for manufacturing a sintered body according to claim 1 or 2.

8. A ceramic sintered body obtained by sintering a mixture of the powder for manufacturing a sintered body according to claim 1 or 2 and a ceramic material.

9. The ceramic sintered body according to claim 7, which is an electronic component.

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