Metal magnetic powder, composite magnetic body, and electronic component

Abstract

To provide metal magnetic powder in which μ" can be maintained in a predetermined value or more at a wide frequency band in a high-frequency region, and a composite magnetic body and an electronic component which include the metal magnetic powder.SOLUTION: Metal magnetic powder includes Co as a main component, has an average particle size of 3 nm or more and 100 nm or less, and has a variation in particle size of 0.1 or more in a CV value. In the metal magnetic powder, when x represents a ratio of a phase of hcp-Co, y represents a ratio of a phase of fcc-Co, and z represents a ratio of a phase of ε-Co, x, y and z are within an area (including on lines) enclosed by line segments connecting the following points A, B, C, D, E in a triangular diagram (x, y, z).SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a metal magnetic powder containing nanoparticles, a composite magnetic body, and an electronic component. [Background technology]

[0002] For example, Patent Document 1 discloses a magnetic material of metal magnetic powder made of metal nanoparticles as a magnetic material for high frequencies. Metal nanoparticles can reduce the number of magnetic domains per unit particle compared to metal magnetic particles on the order of micrometers, and can reduce eddy current loss in the high frequency band. However, even with the magnetic material of metal magnetic powder made of metal nanoparticles in Patent Document 1, when the operating frequency exceeds 1 GHz, the magnetic permeability drops drastically (Figure 2 of Patent Document 1), and magnetic loss increases.

[0003] Furthermore, in recent years, as frequencies have increased, higher frequency noise has been generated, and there has been an increasing demand for noise countermeasures. Magnetic materials used in these high frequency applications are required to have a μ” (the imaginary part of complex permeability / the characteristic of attenuating magnetic flux) greater than a specified value over a wide frequency band. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2006-303298 A Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide nanoparticles capable of maintaining μ″ at or above a predetermined value over a wide frequency band in the high frequency region, as well as a magnetic powder, a composite magnetic body, and an electronic component that contain the nanoparticles. [Means for solving the problem]

[0006] In order to achieve the above object, a nanoparticle according to one aspect of the present invention comprises: Contains Co as the main component, A metal magnetic powder having an average particle size of 3 nm to 100 nm and a particle size variation of 0.1 or more in terms of CV value. In the metal magnetic powder, when the ratio of the hcp-Co phase is x, the ratio of the fcc-Co phase is y, and the ratio of the ε-Co phase is z, It is characterized in that x, y, and z are within the area (including on the line) enclosed by the line segments connecting the following points A, B, C, D, and E on the triangular diagram (x, y, z). A(0.00,0.90,0.10), B(0.55,0.25,0.20), C(0.55,0.20,0.25), D(0.40,0.15,0.45), and E(0.00,0.15,0.85).

[0007] The present inventors conducted extensive research into a metal magnetic powder containing Co as a main component, and as a result discovered that when the hcp-Co phase, the fcc-Co phase, and the ε-Co phase are in a predetermined relative ratio in the metal magnetic powder, it is possible to maintain μ″ at or above a predetermined value in a wide frequency band in the high frequency region, and thus completed the present invention.

[0008] Moreover, a composite magnetic body according to one aspect of the present invention includes at least the above-mentioned metal magnetic powder and a resin.

[0009] Furthermore, an electronic component according to an aspect of the present invention comprises at least the above-mentioned metal magnetic powder. Examples of the composite magnetic body or electronic component include noise suppression sheets, radio wave absorbers, and noise filters such as chip beads. [Brief description of the drawings]

[0010] [Figure 1A] FIG. 1A is a schematic diagram of a magnetic powder containing a metal magnetic powder according to one embodiment of the present invention. [Figure 1B]FIG. 1B is a schematic diagram showing a cross section of a composite magnetic body according to one embodiment of the present invention. [Figure 1C] FIG. 1C is a schematic cross-sectional view showing an example of an electronic component according to one embodiment of the present invention. [Diagram 2] FIG. 2 is an example of an X-ray diffraction pattern of a metal magnetic powder. [Diagram 3] FIG. 3 is a ternary diagram showing the composition of a metal magnetic powder in one embodiment of the present invention. [Figure 4A] FIG. 4A is a graph showing high frequency characteristics of a magnetic body including a metal magnetic powder according to one embodiment of the present invention. [Figure 4B] FIG. 4A is a graph showing high-frequency characteristics of a magnetic body containing a metal magnetic powder according to a comparative example of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, an embodiment shown in the drawings will be described.

[0012] (magnetic powder) The metal magnetic powder 1 according to this embodiment is composed of metal nanoparticles 2, and the average particle size of the nanoparticles 2 (i.e., the average particle size of the magnetic powder) is 3 nm or more and 100 nm or less. The average particle size of the nanoparticles 2 may be calculated by measuring the circle equivalent diameter of each nanoparticle 2 using a transmission electron microscope (TEM).

[0013] Specifically, the magnetic powder 1 is observed at a magnification of 100,000 times or more by a TEM, and the equivalent circle diameter of each nanoparticle 2 included in the observation field is measured by image analysis software. At this time, it is preferable to measure the equivalent circle diameters of at least 500 nanoparticles 2, and based on the measurement results, the average value of the equivalent circle diameters is taken as the average particle size Dave of the nanoparticles 2, and σ / Dave, which is the standard deviation σ of the equivalent circle diameters divided by the average particle size, is calculated as the CV value (coefficient of variation, particle size variation).

[0014] The average particle size of the nanoparticles 2 may be 57 nm or less, or 48 nm or less. The smaller the average particle size of the nanoparticles 2, the easier it is to form a single domain, and the magnetic loss of the magnetic powder can be maintained up to high frequencies. The shape of the nanoparticles 2 is not particularly limited, but the manufacturing method shown in this embodiment usually produces nanoparticles 2 that are spherical or nearly spherical. In addition, a coating such as an oxide film or an insulating film may be formed on the surface of the nanoparticles 2.

[0015] The CV value of the particle size of the nanoparticles 2 is 0.1 or more, and may be 0.2 or more. By widening the particle size distribution, it is possible to widen the μ″ band. In addition, the upper limit of the CV value of the nanoparticles 2 is not particularly limited, but may be 1 or less, or may be 0.7 or less.

[0016] The nanoparticles 2 are Co nanoparticles whose main component is Co. The term "main component" means an element that occupies 80 wt% or more of the nanoparticles. The nanoparticles preferably contain 90 wt% or more of Co, and more preferably contain 93 wt% or more of Co.

[0017] Furthermore, the magnetic powder 1 may contain at least one amphoteric metal other than Co (main component). The amphoteric metal refers to the four elements aluminum (Al), zinc (Zn), tin (Sn) and lead (Pb), and the magnetic powder 1 may contain Zn as an amphoteric metal. The content of Co in the magnetic powder 1 is expressed as W Co (wt%), and the amphoteric metal content is W AM (wt%), W AM / (W Co +W AM ) is preferably 0.001% or more (10 ppm or more) and 10% or less, and more preferably 1% or more and 7% or less. In addition, when the magnetic powder 1 contains two or more kinds of amphoteric metals, W AM is the sum of the contents of each amphoteric metal.

[0018] As shown in FIG. 1A, when the magnetic powder 1 contains an amphoteric metal, the amphoteric metal may be present inside the nanoparticles 2 and / or on the surface of the nanoparticles 2. In other words, the magnetic powder 1 may contain, as crystal grains 3 of the amphoteric metal, crystal grains 3a present inside the nanoparticles 2 and / or crystal grains 3b attached to the surface of the nanoparticles 2. The grain size of the crystal grains 3 of the amphoteric metal is preferably smaller than the average grain size of the nanoparticles 2. The location of the amphoteric metal can be identified, for example, by mapping analysis using TEM-EDS.

[0019] The magnetic powder may contain other trace elements such as Fe, Ni, Cu, Na, Mg, Ca, Cl, P, C, Si, N, and O. The total content of other trace elements (elements other than Co and amphoteric metals) in the magnetic powder is preferably 20 wt% or less.

[0020] The composition of the magnetic powder can be measured by composition analysis using, for example, inductively coupled plasma atomic emission spectroscopy (ICP-AES), X-ray fluorescence analysis (XRF), energy dispersive X-ray analysis (EDS), or electron energy loss spectroscopy (EELS), and is preferably measured by ICP-AES. In composition analysis by ICP-AES, a sample containing the magnetic powder is first collected in a glove box, and the sample is added to an acid solution such as HNO3 (nitric acid) and dissolved by heating. The composition analysis by ICP-AES is performed using this dissolved sample, and the Co and other elements contained in the sample are quantified.

[0021] In the magnetic powder, the main phase of each nanoparticle 2 is a crystalline phase made of Co. Specific examples of the crystalline phase made of Co include the hcp-Co phase (hexagonal close-packed structure), the fcc-Co phase (face-centered cubic structure), and the ε-Co phase (a type of cubic crystal). The nanoparticle 2 of this embodiment contains at least the fcc-Co phase and the ε-Co phase among these three phases.

[0022] In this embodiment, these nanoparticles 2 may be mixed-phase nanoparticles containing two or three of the above-mentioned three mixed phases. Alternatively, they may be any of the three phases, such as single-phase nanoparticles made of hcp-Co, single-phase nanoparticles made of fcc-Co, or single-phase nanoparticles made of ε-Co. In addition, the magnetic powder 1 containing the nanoparticles 2 may be an aggregate of mixed-phase nanoparticles, or may be in a state in which single-phase nanoparticles of multiple phases are mixed, or may be in a state in which mixed-phase nanoparticles and single-phase nanoparticles are mixed.

[0023] Agglomerated Co or micrometer-order Co particles tend to be hcp-Co phase, but when Co is a fine particle of 100 nm or less, the main phase tends to be fcc-Co phase (face-centered cubic structure) or ε-Co phase (a type of cubic crystal). In this embodiment, the ratio of the above three phases in the magnetic powder is controlled by a specific manufacturing method described later.

[0024] When the magnetic powder 1 contains a crystalline phase made of Co within the grains of the nanoparticles 2, it can exhibit a high permeability loss (μ”) in a frequency range of 1.00 to 10.00 GHz or wider.

[0025] The crystalline phase ratio of Co in the magnetic powder 1 (i.e., the crystalline phase ratio of Co in the nanoparticles 2) can be analyzed by X-ray diffraction (XRD). Figure 2 (d) shows an example of an XRD pattern of a magnetic powder. Note that Figure 2 (a) to (c) are all XRD patterns recorded in literature and databases such as ICDD, where (a) is the XRD pattern of the ε-Co phase, (b) is the XRD pattern of the fcc-Co phase, and (c) is the XRD pattern of the hcp-Co phase.

[0026] After obtaining an XRD pattern of the magnetic powder as shown in Figure 2(d) by 2θ / θ measurement of XRD, profile fitting (peak separation) of the measured XRD pattern is performed using XRD analysis software. The separated diffraction peaks are then compared with a database to identify the crystalline phases contained in the magnetic powder. In the XRD pattern shown in Figure 2(d), the peaks indicated by "◯" are diffraction peaks derived from the hcp-Co phase, the peaks indicated by "▽" are diffraction peaks derived from the fcc-Co phase, and the peaks indicated by "□" are diffraction peaks derived from the ε-Co phase.

[0027] The ratio of the Co crystalline phase may be calculated based on the integrated intensity of the diffraction peak. Specifically, the diffraction peaks in the XRD pattern (d) are identified by profile fitting, and then the integrated intensity of the identified diffraction peaks is calculated. hcp is the integrated intensity of the diffraction peak derived from the hcp-Co phase, and W fcc is the integrated intensity of the diffraction peak derived from the fcc-Co phase, and Wε is the integrated intensity of the diffraction peak derived from the ε-Co phase. hcp / (W hcp +W fcc +Wε), W fcc / (W hcp +W fcc +Wε), Wε / (W hcp +W fcc +Wε) can be calculated.

[0028] In the XRD pattern (d) of FIG. 2, the diffraction peaks of the hcp-Co phase, the fcc-Co phase, and the ε-Co phase were detected, and the ratio of the hcp-Co phase (W hcp / (W hcp +W fcc +Wε)) is 40%, and the ratio of fcc-Co phase (W fcc / (W hcp +W fcc +Wε)) is 25%, and the ratio of ε-Co phase (Wε / (W hcp +W fcc +Wε)) is 35%.

[0029] The crystal phase of the nanoparticles 2 may contain a small amount of amphoteric metal or impurity element in solid solution. However, it is preferable that the degree of deviation of the lattice constant of the crystal phase is 0.5% or less. The "degree of deviation of the lattice constant" is expressed by (|d STD -d f |) / d STD (%), d STD is the lattice constant of the crystal phase recorded in the database, and df is the lattice constant of the crystal phase calculated by analyzing the XRD pattern of the magnetic powder. The lattice constant may be measured by a high-resolution image using a TEM.

[0030] In addition, the presence or absence of a mixed phase structure in the grains of the nanoparticles 2 can be confirmed by analysis using a TEM such as a high resolution electron microscope (HREM), electron backscatter diffraction (EBSD), or electron diffraction. For example, when analyzing the crystal phase of each nanoparticle 2 by electron diffraction of a TEM, at least 50 nanoparticles 2 are irradiated with an electron beam, and based on the electron diffraction pattern obtained at that time, it is determined whether each nanoparticle 2 has a single phase structure or a mixed phase structure. In this analysis, it is preferable to select nanoparticles 2 that are isolated within the field of view and irradiate them with an electron beam. In addition, when comparing the mixed phase state, the electron diffraction patterns of multiple nanoparticles may be analyzed at once, and the ratio of the Co crystal phase of the powder may be calculated by analyzing the diffraction intensity caused by each phase by taking Debye rings.

[0031] In other words, in analyzing the crystalline phase ratio of Co in a magnetic powder, the crystalline phase of the nanoparticles 2 may first be identified by electron diffraction using a TEM, and then the phase ratio may be calculated by XRD using the results of the electron diffraction analysis as a reference.

[0032] In this embodiment, in the magnetic powder 1 (nanoparticles 2), the ratio of each Co crystal phase is controlled to be within the area surrounded by the lines connecting A, B, C, D, and E (including on the lines) in a ternary diagram as shown in Figure 3, where the ratio of the hcp-Co phase is x, the ratio of the fcc-Co phase is y, and the ratio of the ε-Co phase is z. A(0.00,0.90,0.10), B(0.55,0.25,0.20), C(0.55,0.20,0.25), D(0.40,0.15,0.45), and E(0.00,0.15,0.85).

[0033] By using such a phase ratio, it is possible to widen the bandwidth of μ″ in the high frequency band.

[0034] Preferably, the ratio of each crystal phase is controlled so that it exists within the area surrounded by the lines connecting A, F, G, and H (including on the lines) in the triangular diagram shown in Figure 3. A(0.00,0.90,0.10), F(0.30, 0.54, 0.16), G(0.30,0.20,0.50), H(0.00,0.20,0.80).

[0035] (composite magnetic material) Next, a composite magnetic body 10 containing the above-mentioned magnetic powder will be described with reference to FIG. 1B.

[0036] The composite magnetic body 10 contains the magnetic powder having the above-mentioned characteristics and the resin 6, and the nanoparticles 2 constituting the magnetic powder are dispersed in the resin 6. In other words, the resin 6 is interposed between the nanoparticles 2, and insulates adjacent particles. The resin 6 may be any resin material having insulating properties, and the material is not particularly limited. For example, the resin 6 may be a thermosetting resin such as an epoxy resin, a phenolic resin, or a silicone resin, or a thermoplastic resin such as an acrylic resin, polyethylene, or polypropylene, and is preferably a thermosetting resin.

[0037] The area ratio of the magnetic powder in the cross section of the composite magnetic body 10 is preferably 10% to 60%, and more preferably 10% to 40%.

[0038] The area ratio of the magnetic powder in the cross section of the composite magnetic body 10 can be calculated by observing the cut surface of the composite magnetic body 10 using a scanning electron microscope (SEM) or a transmission electron microscope (TEM) and analyzing the cross-sectional image using image analysis software. Specifically, the cross-sectional image of the composite magnetic body 10 is binarized based on the contrast to distinguish the magnetic powder from other parts, and the ratio of the area occupied by the magnetic powder to the entire image (i.e., the area of ​​the observed field of view) is calculated. The area ratio calculated by the above method can be regarded as the filling rate of the nanoparticles 2 in the composite magnetic body 10.

[0039] Even when magnetic powder 1 is contained in composite magnetic body 10, the average particle size (D50), composition, and ratio of the Co crystalline phase of magnetic powder 1 can be analyzed by the methods described above (TEM observation, EDS, electron diffraction analysis, XRD, etc.).

[0040] The composite magnetic body 10 may contain ceramic particles, metal particles other than the nanoparticles 2, and the like. Furthermore, the shape and dimensions of the composite magnetic body 10 are not particularly limited and may be appropriately determined depending on the application.

[0041] (Method of manufacturing magnetic powder) An example of a method for producing the magnetic powder 1 and the composite magnetic body 10 will be described below. The magnetic powder of this embodiment may be produced using any of a gas phase method, a liquid phase method, and a solid phase method. For example, gas phase methods include a thermal CVD method, a plasma CVD method, a flame method, and a PVD method. Liquid phase methods include a thermal decomposition method, a liquid phase reduction method, and a laser ablation method. Solid phase methods include a method in which a precursor is directly heated and decomposed. In terms of ease of controlling the phase ratio, particle size, and dispersibility, it is preferable to use a thermal decomposition method.

[0042] The thermal decomposition method is a method for producing Co nanoparticles by heating and thermally decomposing a precursor Co complex. In general, a solution in which the precursor is dissolved in a solvent is heated to room temperature to about 300°C, and the precursor is thermally decomposed in the liquid phase. The precursor cobalt complex is typically octacarbonyldicobalt (Co2 (CO) 8 , or Co 4 (CO) 12 , chlorotriphenylphosphine cobalt (CoCl(Ph 3 P) 3 ), etc. can be used. In addition to dichlorobenzene and ethylene glycol, tetralin, o-dichlorobenzene, tetrahydrofuran (THF), oleyl alcohol, oleylamine, or octylamine can be used as the solvent. Furthermore, a surfactant can be added to the solution to control the dispersibility and particle size. For example, it is preferable to use a silane coupling agent containing an aniline structure and / or a phenyl group as the surfactant. Other surfactants that can be used include oleic acid, lauric acid, palmitic acid, melissic acid, trioctylphosphine oxide (TOPO), trioctylamine (TOA), triphenylphosphine oxide (TPPO), triphenylphosphine (TPP), and triphenylamine (TPA). When selecting a precursor, a solvent, and a surfactant, each may be used alone or two or more types may be mixed together so that the desired particles can be obtained.

[0043] As the reaction vessel, for example, a separable flask can be used, and the material of the reaction vessel is not particularly limited. The precursor, the solvent, and if necessary, the surfactant are put into a reaction vessel such as a separable flask, and stirred using a mechanical stirrer or the like. Thereafter, heating for pyrolysis is performed by a heater, but in order to perform heating as uniformly as possible, it is preferable to use, for example, a mantle heater. After cooling the heated solution, the unreacted matter and intermediate products are removed using a cleaning solvent, and the generated nanoparticles 2 are washed. As the cleaning solvent, for example, an organic solvent such as acetone, dichlorobenzene, or ethanol can be used, and in order to suppress oxidation of the nanoparticles 2, it is preferable to subject the cleaning solvent to a degassing treatment. Alternatively, it is preferable to use an organic solvent of ultra-dehydrated grade with a water content of 10 ppm or less as the cleaning solvent. Thereafter, in order to separate and recover the nanoparticles 2 from the solvent, centrifugation or a magnet may be used. By the above process, a magnetic powder is obtained.

[0044] It is preferable that a series of steps from weighing the raw materials to washing and collecting the nanoparticles be carried out in an inert gas atmosphere such as argon or nitrogen.

[0045] After synthesis of nanoparticles, the particle size distribution may be adjusted. In order to control the average particle size or particle size distribution (CV value), the nanoparticles may be classified using a device such as a liquid chromatography device, an electric mobility classifier device, or an inertial classifier device (e.g., a cascade impactor). Furthermore, the particle size distribution may be broadened by mixing classified nanoparticles of different particle sizes.

[0046] Co as precursor 2 (CO) 8 or CoCl(Ph 3 P) 3When synthesizing Co nanoparticles using TOA, the surfactants mentioned above can be used as the surfactant to be added, but the phase ratio of the obtained Co nanoparticles tends to be high in the hcp-Co phase when TOA is used, high in the ε-Co phase when TOP is used, and high in the fcc-Co phase when TOPO is used. In order to control the phase ratio, these surfactants may be mixed and added. The amount of surfactant added is preferably about 0.1 to 50 molar equivalents relative to the amount of Co.

[0047] Regardless of which precursor is used, in terms of particle size control, it is desirable to carry out the thermal decomposition treatment at a high temperature for a long time in order to increase the particle size. On the other hand, if the thermal treatment is carried out at a low temperature for a short time, it is easy to obtain particles with a small particle size. Also, in order to obtain particles with a wide particle size distribution, it is preferable to increase the temperature rise rate to the decomposition temperature. The thermal decomposition temperature is preferably 30°C or higher and lower than the boiling point of the solvent, the thermal decomposition time is 10 minutes to 24 hours, and the temperature rise rate is about 0.5 to 50°C / min, but is not particularly limited to these ranges.

[0048] The particle size can also be controlled by the precursor concentration in the solution, and a high concentration makes it easier to obtain particles with a small particle size. The range of the precursor concentration is not particularly limited, but is preferably about 0.1 to 100 mM. Furthermore, the particle size and particle size distribution can be controlled by adding additional precursor during the thermal decomposition of the precursor. If a solution with a high precursor concentration close to the saturation solubility is prepared and added to the solution during thermal decomposition, nanoparticles with a wide particle size distribution are more likely to be obtained. On the other hand, if a solution with a low concentration is added, particles with a narrow particle size distribution and particle growth are more likely to be obtained. Since it also depends on the combination of the solvent and the surfactant, the precursor concentration before addition, and the timing of addition during the thermal decomposition reaction, it is preferable to adjust the concentration appropriately.

[0049] After stopping the stirring of the solution to stop the reaction, the generated nanoparticles 2 are washed and collected. When washing the nanoparticles 2, a washing solvent that dissolves unreacted raw materials and intermediate products is used. Specifically, the washing solvent may be, for example, an organic solvent such as acetone, dichlorobenzene, or ethanol.

[0050] In order to suppress oxidation of the nanoparticles 2, it is preferable to perform a degassing process on the washing solvent. Alternatively, it is preferable to use an organic solvent of ultra-dehydrated grade with a water content of 10 ppm or less as the washing solvent. The nanoparticles 2 can be collected by centrifugation or by using a magnet. The above steps produce a magnetic powder.

[0051] The series of steps from weighing the raw materials to washing and collecting the nanoparticles are carried out in an inert gas atmosphere such as an Ar atmosphere.

[0052] (Method of manufacturing composite magnetic body) Next, an example of a method for manufacturing the composite magnetic body 10 will be described. The composite magnetic body 10 can be manufactured by mixing the magnetic powder, the resin 6, and a solvent, subjecting the mixture to a predetermined dispersion process, and forming the mixture into a predetermined shape (for example, a sheet). As the dispersion process, it is preferable to employ ultrasonic dispersion or media dispersion using a bead mill or the like.

[0053] The conditions for the dispersion treatment are not particularly limited, and various conditions may be set so that the nanoparticles 2 are uniformly dispersed in the resin 6. As the solvent to be added during the dispersion treatment, for example, an organic solvent such as acetone, dichlorobenzene, or ethanol may be used, and it is preferable to use a degassed organic solvent or an organic solvent of ultra-dehydrated grade. In addition, as the media used during the media dispersion treatment, various ceramic beads may be used, and ZrO, which has a large specific gravity among ceramic beads, is preferable. 2 It is preferable to use beads of the above formula.

[0054] The slurry obtained by the above dispersion process is dried in an inert atmosphere such as an Ar atmosphere to obtain a dried body by volatilizing the solvent. The dried body is then crushed using a mortar or a dry crusher to obtain granules containing the magnetic powder and the resin 6. The granules are then filled into a mold and pressed to obtain the composite magnetic body 10.

[0055] When a thermosetting resin is used as the resin 6, it is preferable to subject the composite magnetic body after pressure molding to a hardening treatment.

[0056] The method for producing the composite magnetic body is not limited to the above-mentioned pressure molding method. For example, the slurry obtained by the dispersion process may be applied onto a PET film and dried to obtain a sheet-shaped composite magnetic body 10.

[0057] The series of steps for obtaining the composite magnetic body 10 are also carried out in an inert atmosphere such as an Ar atmosphere, similar to the production of the magnetic powder.

[0058] (Summary of the embodiment)

[0059] According to the magnetic powder 1 containing the nanoparticles 2 of this embodiment, the hcp-Co phase, the fcc-Co phase, and the ε-Co phase have a predetermined ratio relationship, so that it is possible to maintain μ″ at a predetermined value or higher over a wide frequency band (for example, from 1.00 GHz or less to 10.00 GHz or more) in the high frequency region of the gigahertz band. According to the magnetic powder of this embodiment, the ratio relationship between the hcp-Co phase, the fcc-Co phase, and the ε-Co phase is controlled within the region surrounded by the line segments connecting points A, B, C, D, and E in the triangular diagram (x, y, z) shown in FIG. 3 (including the areas on the lines).

[0060] Therefore, as shown in FIG. 4A, μ" can be maintained at or above a predetermined value over a wide frequency band in the high frequency region of the gigahertz band. Specifically, in this embodiment, as shown in FIG. 4A, Fmin, which is the lower limit of the frequency at which μ" is 0.5 or more, is 1.00 GHz or less, and Fmax, which is the upper limit of the frequency at which μ" is 0.5 or more, is 10.00 GHz or more, and μ" can be continuously 0.5 or more between Fmin and Fmax. In this embodiment, the noise absorption effect is enhanced over a wide band in the high frequency region of the gigahertz band. For example, noise can be removed up to a higher frequency range than products using conventional ferrite or Fe-based flat powder.

[0061] In contrast, for example, in conventional magnetic powders that fall outside the area enclosed by the line segment connecting points A, B, C, D, and E in the triangular diagram (x, y, z) shown in Figure 3, it is not possible to maintain μ" higher than a specified value over a wide frequency band in the high frequency range of the gigahertz band. Specifically, as shown in Figure 4B, in the past, Fmin, the lower limit of the frequency at which μ" is 0.5 or greater, is greater than 1.00 GHz, or Fmax, the upper limit of the frequency at which μ" is 0.5 or greater, is less than 10.00 GHz, and the frequency interval between Fmin and Fmax is narrow. With such conventional technology, the noise suppression effect is poor over a wide band.

[0062] In addition, in the magnetic powder of the embodiment showing the results shown in Figure 4A, the Co phase ratio (x, y, z) in the ternary diagram shown in Figure 3 is (0.40, 0.20, 0.40), and in the magnetic powder of the comparative example showing the results shown in Figure 4B, the Co phase ratio (x, y, z) in the ternary diagram shown in Figure 3 is (1.00, 0.00, 0.00).

[0063] The composite magnetic body 10 having the magnetic powder 1 containing the nanoparticles 2 according to this embodiment exhibits high magnetic permeability loss in a wide high frequency range of 1.00 GHz to 10.00 GHz, and can be suitably applied to electronic components for high frequency applications such as noise suppression sheets, radio wave absorbers, and noise filters.

[0064] An example of an electronic component containing magnetic powder (or composite magnetic body 10) is chip bead 100 as shown in FIG. 4. The chip bead 100 has an element body made of the composite magnetic body 10 of this embodiment, and a coil section 50 is embedded inside the element body. A pair of external electrodes 60, 80 are formed on the end faces of the element body, and each of the external electrodes 60, 80 is electrically connected to the lead-out sections 50a, 50b of the coil section 50, respectively. Since electronic components such as the chip bead 100 contain the magnetic powder (composite magnetic body 10) of this embodiment, they have excellent noise absorption characteristics at high frequencies.

[0065] Although the embodiment has been described above, the present invention is not limited to the above-mentioned embodiment and can be modified in various ways. For example, the magnetic powder may contain other magnetic particles different from the nanoparticles 2 according to the above-mentioned embodiment, as long as the effect of this embodiment is achieved. Examples of other magnetic particles include Fe, Ni, FeC 2 ,CoC,Fe 4 N, γ-Fe 2 O 3 , Fe 3 O 4 , CoFe 2 O 4 , NiFe 2 O 4 , etc., and may be contained in an amount of, for example, about 10 wt % or less. EXAMPLES

[0066] The present invention will be described in more detail below with reference to specific examples, although the present invention is not limited to the following examples.

[0067] Experimental Example 1 Metal magnetic powders shown in sample numbers 1 to 6 in Table 1 were manufactured. The average particle size of these metal magnetic powders was about 20 nm, and the particle size variation was 0.1 in CV value. In the metal magnetic powder, when the ratio of the hcp-Co phase is x, the ratio of the fcc-Co phase is y, and the ratio of the ε-Co phase is z, the ratio of the Co phase was adjusted so that x, y, and z are within the area surrounded by the line segment connecting points A, B, C, D, and E in the triangular diagram (x, y, z) shown in Figure 3.

[0068] The ratio of the Co phase was adjusted by preparing hcp-Co single-phase nanoparticles, fcc-Co single-phase nanoparticles, and ε-Co single-phase nanoparticles and mixing them as follows.

[0069] (hcp-Co single-phase nanoparticles) First, CoCl(PPh 3 ) 3(precursor), oleyl alcohol (solvent), and oleic acid (surfactant) were weighed and placed in a separable flask. The solution was heated under Ar atmosphere while being stirred, to pyrolyze the precursor in the solution. Specifically, the solution in the separable flask was heated to 120°C at a heating rate of 5°C / min using a mantle heater and a temperature controller while being stirred by a mechanical stirrer. In this case, in order to synthesize nanoparticles with different average particle sizes from 5 to 400 nm, the synthesis was performed by changing the temperature holding time from 30 minutes to 24 hours after the temperature of the solution reached a predetermined temperature.

[0070] After cooling the pyrolyzed solution to 30°C, ethanol was added to the solution to precipitate the generated nanoparticles. The rotation speed was set to 20,000 rpm, and centrifugation was performed for 10 minutes. The supernatant was removed to remove undecomposed raw materials and by-products. This centrifugation process was repeated three times to collect the nanoparticles.

[0071] As a result of the synthesis, nanoparticles with average diameters of 5, 10, 20, 50, 100, 120, 200, and 400 nm were obtained. X-ray diffraction confirmed that all were single-phase hcp-Co. The coefficient of variation (CV) of the particle diameters of the nanoparticles between 5 and 20 nm was 0.1. On the other hand, the CV values ​​of the nanoparticles with an average diameter of 50 nm or more were 0.2 to 0.6.

[0072] Nanoparticles with an average particle size of 20 nm were classified three times using a cascade impactor to obtain single-phase hcp-Co nanoparticles with an average particle size of 20 nm and a CV value of 0.05. Nanoparticles with an average particle size of 50 nm or more were then classified once or twice to obtain single-phase hcp-Co nanoparticles with a CV value of 0.1 for each average particle size.

[0073] (fcc-Co single-phase nanoparticles) First, Co 2 (CO) 8(precursor), o-dichlorobenzene (solvent) and N-phenyl-3-aminopropyltrimethoxysilane (surfactant) were weighed and put into a separable flask. The solution was heated and stirred under an Ar atmosphere to pyrolyze the precursor in the solution. Specifically, the solution in the separable flask was heated to 180°C by controlling the heating rate to 5°C / min using a mantle heater and a temperature controller while stirring with a mechanical stirrer. In this case, in order to synthesize nanoparticles with different average particle sizes of 5 to 400 nm, the synthesis was performed by changing the temperature holding time from 10 minutes to 16 hours after the temperature of the solution reached a predetermined temperature.

[0074] Thereafter, the same procedures as for the above-mentioned hcp-Co single-phase nanoparticles were carried out after cooling the solution, and various fcc-Co single-phase nanoparticles having average particle sizes and CV values ​​equivalent to those of the above-mentioned hcp-Co single-phase nanoparticles were obtained.

[0075] (ε-Co single-phase nanoparticles) First, Co 2 (CO) 8 (precursor), tetralin (solvent) and trioctylphosphine oxide (surfactant) were weighed and put into a separable flask. The solution was heated and stirred under an Ar atmosphere to pyrolyze the precursor in the solution. Specifically, the solution in the separable flask was heated to 120°C by controlling the heating rate to 1°C / min using a mantle heater and a temperature controller while stirring with a mechanical stirrer. In this case, in order to synthesize nanoparticles with different average particle sizes from 5 to 400 nm, the synthesis was performed by changing the temperature holding time from 10 minutes to 16 hours after the temperature of the solution reached a predetermined temperature.

[0076] Thereafter, the solution was cooled and subsequent steps were carried out in the same manner as for the above-mentioned single-phase hcp-Co nanoparticles, and various single-phase ε-Co nanoparticles having average particle sizes and CV values ​​equivalent to those of the above-mentioned single-phase hcp-Co nanoparticles were obtained.

[0077] (Preparation of metal magnetic powder) For the hcp-Co single-phase nanoparticles, the average particle size and CV value were adjusted to the desired values ​​by mixing nanoparticles with various average particle sizes and a CV value of 0.1. The average particle size and CV value were adjusted by mixing particles with similar particle sizes. For example, particles with an average particle size of 20 nm and a CV value of 0.2 were obtained by mixing particles with average particle sizes of 10, 20, and 50 nm and a CV value of 0.1 at ratios of 3, 96, and 1 wt%, respectively. In this way, hcp-Co single-phase nanoparticles with an average particle size of about 20 nm and CV values ​​of 0.05, 0.1, 0.2, 0.4, 0.7, and 1.0 were prepared. The average particle size and CV value of each of the fcc-Co single-phase nanoparticles and the ε-Co single-phase nanoparticles were also adjusted in the same manner as for the hcp-Co single-phase nanoparticles. Furthermore, hcp-Co single-phase nanoparticles, fcc-Co single-phase nanoparticles, and ε-Co single-phase nanoparticles with equivalent average particle sizes and CV values ​​were mixed in the specified ratios shown in Table 1 to obtain the metal magnetic powders (Co nanoparticles) shown in sample numbers 1 to 6.

[0078] (Manufacturing of composite magnetic bodies) A composite magnetic body was produced using the magnetic metal powder by the method described below.

[0079] First, the magnetic powder and polystyrene resin were weighed so that the nanoparticle filling rate in the composite magnetic body was 20 vol%. Then, the weighed metal magnetic powder, polystyrene resin, and acetone as a solvent were mixed, and the mixture was subjected to ultrasonic dispersion treatment. The ultrasonic dispersion treatment time was 5 min, and the dispersion obtained by the ultrasonic dispersion treatment was heated to 50 ° C in an Ar atmosphere to obtain a dried body.

[0080] The dried material was then mixed in a mortar, and the resulting granules were filled in a metal mold and pressed to obtain a toroidal composite magnetic body with an outer diameter of 7 mm, an inner diameter of 3 mm, and a thickness of 1 mm. Each step of producing the composite magnetic body was carried out under an Ar atmosphere, except for the molding step. The cross-sections of the composite magnetic bodies produced by the above method were analyzed, and the filling rate of the metal magnetic powder was calculated based on the area ratio of the nanoparticles. It was confirmed that in all cases, the filling rate was 20 vol.%, as targeted.

[0081] The composite magnetic bodies produced from each of the metal magnetic powders were evaluated as follows.

[0082] (Average particle size of nanoparticles) The prepared nanoparticles were observed at a magnification of 100,000 times using a TEM (JEM-2100F manufactured by JEOL Ltd.). The circle equivalent diameters of 500 nanoparticles were measured using image analysis software, and the average particle size was calculated. The results are shown in Table 1.

[0083] (Analysis of Co crystal phase ratio) The XRD patterns of the composite magnetic bodies were obtained by 2θ / θ measurement using an XRD device (Rigaku Corporation: Smart Lab). The obtained XRD patterns were then analyzed using integrated X-ray analysis software (SmartLab Studio II) to determine the ratios of the hcp-Co phase, the fcc-Co phase, and the ε-Co phase (W hcp , W fcc , and Wε) were calculated. In this analysis, the ratio of each Co crystal phase was calculated with the total of the hcp-Co phase, the fcc-Co phase, and the ε-Co phase being 100%. The results are shown in Table 1.

[0084] (Evaluation of magnetic properties) The imaginary part of the complex permeability (i.e., permeability μ″ (unitless)) at each frequency was measured by the coaxial S-parameter method using a network analyzer (Agilent Technologies: N5222A). Then, as shown in Figure 4A, the minimum value of the frequency band where μ″ is 0.5 or more was taken as Fmin, and the maximum value was taken as Fmax. The results are shown in Table 1. In this case, samples with Fmin of 1.00 GHz or less and Fmax of 10.00 GHz or more, that is, samples where μ″ is always 0.5 or more at frequencies from 1.00 to 10.00 GHz, were judged to be good. In addition, samples with Fmin of 0.50 GHz or less and Fmax of 10.00 GHz or more, that is, samples where μ″ is always 0.5 or more at frequencies from 0.50 to 10.00 GHz, were judged to be particularly good.

[0085] [Table 1]

[0086] Experimental Example 2 A composite magnetic body was produced and evaluated in the same manner as in Experimental Example 1, except that a magnetic powder was used in which the single-phase nanoparticles of hcp-Co phase, fcc-Co phase, and ε-Co phase, each having an average particle size of 20 nm and a CV value of 0.4, produced in Experimental Example 1, were mixed in the specified ratios shown in Table 2. The results are shown in Table 2.

[0087] [Table 2]

[0088] Experimental Example 3 For each single-phase nanoparticle (hcp-Co, fcc-Co, ε-Co) with a CV value of 0.1 produced in Experimental Example 1, single-phase nanoparticles with different average particle sizes were mixed to produce single-phase nanoparticle powders with average particle sizes of 5, 10, 20, 50, 100, and 120 nm and CV values ​​of 0.2, 0.4, and 0.7 at each average particle size. Next, hcp-Co single-phase nanoparticles, fcc-Co single-phase nanoparticles, and ε-Co single-phase nanoparticles with the same average particle size and CV value were mixed in a predetermined ratio to produce metal magnetic powders with the average particle size, CV value, and Co phase ratio shown in Tables 3 to 7. Using the produced metal magnetic powder, a composite magnetic body was produced by the same method as in Experimental Example 1 and evaluated. The results are shown in Tables 3 to 7.

[0089] [Table 3]

[0090] [Table 4]

[0091] [Table 5]

[0092] [Table 6]

[0093] [Table 7]

[0094] In Table 2 and onwards, sample numbers marked with an * indicate metal magnetic powders according to comparative examples. Even if the particle size of the magnetic powder is within the range of 3 to 100 nm and the CV value is within the range of 0.1 to 1.0, if the phase ratio is outside the area (including on the line) surrounded by the line segment connecting points A, B, C, D and E in the triangular diagram (x, y, z) shown in Fig. 3, Fmin will exceed 1.00 GHz or Fmax will be less than 10.00 GHz, and it will not be possible to maintain μ" high at 0.5 or more in the range from 1.00 GHz to 10.00 GHz.

[0095] evaluation From the results shown in Tables 1 to 7, it was confirmed that in metal magnetic powders (nanoparticles) with an average particle size in the range of 1 to 100 nm and a CV value of 0.1 to 1.0, and a phase ratio within the region surrounded by the line segment connecting points A, B, C, D, and E in the triangular diagram (x, y, z) shown in FIG. 3 (including on the line), it is possible to maintain μ” high at 0.5 or more over a wide frequency band (for example, 1.00 GHz to 10.00 GHz) when the average particle size is in the range of 3 to 100 nm, preferably 3.6 to 54 nm, and the CV value is 0.1 to 1.0, preferably 0.2 to 0.7. In other words, it was found that the metal magnetic powders (nanoparticles) of the examples can be suitably used for purposes such as noise removal over a wide high frequency band.

[0096] Furthermore, it was confirmed that, in particular, for metal magnetic powders with a CV value in the range of 0.2 to 0.7, the range of Co phase ratio in which μ” can be maintained high at 0.5 or more over a wide frequency band (for example, from 0.50 GHz to 10.00 GHz) can be expanded compared to metal magnetic powders outside that range. Furthermore, from the results shown in Tables 2 to 7, it was confirmed that metal magnetic powders (nanoparticles) with phase ratios within the region surrounded by the line segment connecting points A, F, G, and H in the triangular diagram (x, y, z) shown in Figure 3 (including on the line) have further improved properties compared to metal magnetic powders with ratios outside that range.

[0097] Experimental Example 4 The single-phase nanoparticles having various average particle sizes and various CV values ​​obtained in Experimental Example 3 were mixed to obtain the predetermined phase ratios shown in Tables 8 and 9 to prepare metal magnetic powders. Composite magnetic bodies having metal magnetic powder filling rates of 10, 20, 40, and 60 vol% were then produced and evaluated. The results are shown in Tables 8 and 9.

[0098] [Table 8]

[0099] [Table 9]

[0100] evaluation From the results shown in Tables 8 to 9, it was confirmed that metal magnetic powders (nanoparticles) with a Co phase ratio within the area (including on the line) surrounded by the line connecting points A, B, C, D, and E in the triangular diagram (x, y, z) shown in Figure 3 exhibit good characteristics when the filling rate of the metal magnetic powder is in the range of 10 to 60 vol%. [Explanation of symbols]

[0101] 1…Magnetic powder 2. Nanoparticles 6… Resin 10…Magnetic powder 100… Chip beads 50… Coil section 60,80… External electrode

Claims

1. Contains Co as a main component, A metal magnetic powder having an average particle size of 3 nm or more and 100 nm or less and a particle size variation of 0.1 or more in terms of CV value, In the metal magnetic powder, when the ratio of the hcp-Co phase is x, the ratio of the fcc-Co phase is y, and the ratio of the ε-Co phase is z, A metal magnetic powder characterized in that x, y, and z are within the area surrounded by lines connecting the following points A, B, C, D, and E in a triangular diagram (x, y, z) (including on the lines). A (0.00, 0.90, 0.10), B(0.55, 0.25, 0.20), C (0.55, 0.20, 0.25), D(0.40, 0.15, 0.45), and E(0.00, 0.15, 0.85).

2. A composite magnetic body comprising the metal magnetic powder according to claim 1 and a resin.

3. An electronic component comprising the metal magnetic powder according to claim 1.

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