Ni-Zn-Cu ferrite powder, sintered body, ferrite sheet

Abstract

To provide a Ni-Zn-Cu-based ferrite powder capable of being sintered even at a low temperature of 860°C, for example.SOLUTION: A Ni-Zn-Cu-based ferrite powder comprises 45-49 mol% of Fe2O3, 5-25 mol% of NiO, 15-40 mol% of ZnO, 5-15 mol% of CuO, and 0-3 mol% of CoO, wherein a crystallite size is 180 nm or less. The Ni-Zn-Cu-based ferrite powder is used in a sintered compact or ferrite sheet.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to Ni-Zn-Cu ferrite materials, specifically to a ferrite powder that can be sintered at low temperatures, and also to a sintered body and a ferrite sheet using the ferrite powder. [Background technology]

[0002] In recent years, electronic devices for home and industrial use have become smaller and lighter, and consequently, there is a growing need for smaller, more efficient, and higher-frequency electronic components used in these devices.

[0003] For example, inductors used in electronic circuits of electronic devices range from wound-type inductors, which form coils by winding insulating copper wire around a magnetic core or air-core bobbin, to ferrite-sintered multilayer chip inductors, which have been put into practical use.

[0004] This multilayer chip inductor is manufactured through the following manufacturing process: a green sheet is formed by depositing a paste containing ferrite powder into a sheet. Conductive patterns are then formed on this green sheet using a paste containing electrode materials such as Ag and Ag-Pd, by printing or other means. These sheets are then stacked and sintered at a predetermined temperature to form the external electrodes.

[0005] Incidentally, as mentioned above, the manufacturing process for multilayer chip inductors employs a method of simultaneously firing the electrode material and ferrite laminate. This method has the problem that the inherent properties of the ferrite deteriorate due to interfacial reactions (mutual diffusion) between the electrode material such as Ag and Ag-Pd and the ferrite. To avoid this problem, it is considered necessary to fire the inductors at a low temperature of approximately 900°C or below.

[0006] However, when fired at temperatures below 900°C, it is difficult to obtain a Ni-based ferrite sintered body with excellent electromagnetic properties such as permeability, suitable for use as a magnetic material for multilayer chip inductors.

[0007] Several technologies have been proposed to enable sintering of Ni-Zn-Cu ferrite powder even at low temperatures. For example, one method involves adding borosilicate glass, a sintering aid, to generate a liquid phase during sintering and promote the growth of ferrite particles (Patent Document 1). Another method involves adding glass components, such as glass components consisting of SiO2, B2O3, and Na2O, to form liquid-phase sintering and promote ferrite particle growth (Patent Document 2). There is also a method that involves adding glass components that do not contain PbO, which has a high environmental impact, or Na, which reduces the permeability of ferrite and adversely affects electronic devices, to form liquid-phase sintering and promote ferrite particle growth (Patent Document 3). Furthermore, for RFID applications, there is a method to achieve high permeability by controlling the full width at half maximum of the XRD diffraction peak of the crystalline phase of Ni-Zn-Cu ferrite powder (Patent Document 4). [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 5-326241 [Patent Document 2] Japanese Patent Publication No. 2000-208316 [Patent Document 3] Japanese Patent Publication No. 2007-99539 [Patent Document 4] Japanese Patent Publication No. 2005-64468 [Overview of the Initiative] [Problems that the invention aims to solve]

[0009] All of the methods described in Patent Documents 1 to 3 involve adding glass components to form liquid-phase sintering and promote ferrite particle growth. However, the amount of these additives added is very small, making uniform dispersion difficult and promoting uneven growth of ferrite particles. Furthermore, while Patent Document 4 does not include any sintering aids, it requires firing at high temperatures of 1060°C or higher, and low-temperature sintering is not considered.

[0010] Therefore, the present invention aims to provide a Ni-Zn-Cu ferrite powder that can be sintered at low temperatures in order to solve the problems of the conventional technology described above. [Means for solving the problem]

[0011] The aforementioned technical problems can be solved by the present invention as follows.

[0012] In other words, the present invention relates to a Ni-Zn-Cu ferrite powder containing 45-49 mol% Fe2O3, 5-25 mol% NiO, 15-40 mol% ZnO, 5-15 mol% CuO, and 0-3 mol% CoO, with a crystallite size of 180 nm or less, characterized in that the Ni-Zn-Cu ferrite powder is a single-phase spinel ferrite (Invention 1).

[0013] Furthermore, the present invention is a Ni-Zn-Cu ferrite powder according to Invention 1, wherein the strain is 0.330 or less (Invention 2).

[0014] Furthermore, the present invention achieves a sintered density of 5.00 g / cm³ when fired at 860°C in air. 3 The Ni-Zn-Cu ferrite powder described in Invention 1 or Invention 2 above (Invention 3).

[0015] Furthermore, the present invention is a sintered body using Ni-Zn-Cu ferrite powder described in any one of the present inventions 1 to 3 (present invention 4).

[0016] Furthermore, the present invention is a ferrite sheet using the Ni-Zn-Cu ferrite powder described in any one of the present inventions 1 to 3 (present invention 5). [Effects of the Invention]

[0017] The Ni-Zn-Cu ferrite powder according to the present invention has a small crystallite size, so a ferrite sintered body with high sintered density can be obtained even when sintered at low temperature. In addition, since the Ni-Zn-Cu ferrite powder according to the present invention can be sintered at a low temperature of, for example, 860°C, when used in a multilayer inductor where Ag and magnetic powder are co-fired, it can suppress the diffusion of Ag with a low melting point, and is expected to improve inductor performance. [Description of Embodiments]

[0018] The Ni-Zn-Cu ferrite powder according to the present invention will be described.

[0019] The Ni-Zn-Cu ferrite powder according to the present invention contains Fe, Ni, Zn and Cu as constituent metal elements, and optionally Co. When each constituent metal element is converted into Fe₂O₃, NiO, ZnO, CuO and CoO, based on the total (100%) of Fe₂O₃, NiO, ZnO, CuO and CoO, the powder contains not more than 49 mol% of Fe₂O₃, 5 to 25 mol% of NiO, 15 to 40 mol% of ZnO, 5 to 15 mol% of CuO, and 0 to 3 mol% of CoO.

[0020] The Fe content of the Ni-Zn-Cu ferrite powder according to the present invention is not more than 49 mol% in terms of Fe₂O₃. If the Fe content exceeds 49 mol%, sinterability is significantly reduced. The Fe content is preferably not more than 48.9 mol%, more preferably not more than 48.8 mol%. The lower limit is about 45 mol%.

[0021] The Ni content of the Ni-Zn-Cu ferrite powder according to the present invention is 5 to 25 mol% in terms of NiO. If the Ni content is less than 5 mol%, μ' decreases, which is not preferable. In addition, the Curie temperature decreases, which limits the usable temperature range, so this is not preferable. If the Ni content exceeds 25 mol%, μ' also decreases, which is not preferable. The Ni content is preferably 6 to 24.9 mol%, more preferably 7 to 24.8 mol%.

[0022] The Zn content of the Ni-Zn-Cu ferrite powder according to the present invention is 15 to 40 mol% in terms of ZnO. A Zn content of less than 15 mol% is undesirable because it reduces μ'. Furthermore, it is undesirable because it lowers the Curie temperature and limits the usable temperature range. A Zn content exceeding 40 mol% is also undesirable because it reduces μ'. The Zn content is preferably 18 to 38 mol%, more preferably 20 to 35 mol%.

[0023] The Cu content of the Ni-Zn-Cu ferrite powder according to the present invention is 5 to 15 mol% in terms of CuO. If the Cu content is less than 5 mol%, the sinterability decreases, making it difficult to produce a sintered body at low temperatures. If the Cu content exceeds 15 mol%, it is undesirable because μ' decreases. The Cu content is preferably 6 to 14 mol%, more preferably 7 to 13 mol%.

[0024] The Ni-Zn-Cu ferrite powder according to the present invention may contain Co. The Co content is 0 to 3 mol% in terms of CoO. In the present invention, the presence of Co in the ferrite shifts the snake limit line to the higher frequency side, thereby improving the Q (μ' / μ) of the ferrite core, which is the ratio of the real part μ' to the imaginary part μ'' of the complex permeability in the high-frequency range. However, if the Co content exceeds 3 mol% in terms of CoO, the permeability tends to decrease, and the Q of the ferrite core also tends to decrease. The Co content is preferably 0 to 2.9 mol%, more preferably 0 to 2.8 mol%.

[0025] The Ni-Zn-Cu ferrite powder according to the present invention has a crystallite size of 180 nm or less. If the crystallite size exceeds 180 nm, particle growth is accelerated at the magnetic powder stage, which reduces sinterability when firing the sintered body or green sheet, making low-temperature sintering impossible. More preferably, the crystallite size is 175 nm or less, and even more preferably 170 nm or less. The lower limit is about 100 nm.

[0026] The Ni-Zn-Cu ferrite powder according to the present invention preferably has a crystal strain of 0.330 or less. If the strain exceeds 0.330, it may decrease μ', which is undesirable. More preferably it is 0.325 or less, and even more preferably 0.320 or less. The lower limit is about 0.100. The Ni-Zn-Cu ferrite powder according to the present invention is preferably a single-phase spinel ferrite.

[0027] The Ni-Zn-Cu ferrite powder according to the present invention may contain various elements at impurity levels in addition to the aforementioned elements, as long as they do not affect its properties. Generally, it is known that adding Bi has the effect of lowering the sintering temperature of ferrite. However, if the dispersion state of Bi is non-uniform, it promotes non-uniform particle growth during firing, so aggressive addition of Bi is undesirable, and 0 ppm is preferable.

[0028] The Ni-Zn-Cu ferrite powder according to the present invention may contain Si as an unavoidable impurity, up to a maximum of 500 ppm in terms of SiO2. It is preferable that it does not contain Sn or the like (0 ppm).

[0029] The Ni-Zn-Cu ferrite powder according to the present invention can be obtained by conventional methods, which involve mixing raw materials such as oxides, carbonates, hydroxides, and oxalates of each element constituting ferrite in predetermined compositional ratios to obtain a raw material mixture, or by precipitating each element in an aqueous solution to obtain a coprecipitation, which is then calcined in air at a temperature range of 650 to 950°C for 1 to 20 hours, followed by pulverization. The calcination temperature is preferably 700 to 940°C.

[0030] In this invention, the BET specific surface area of ​​Fe2O3, the Fe raw material, is 6.0 m². 2 It is preferable that the BET specific surface area of ​​Fe2O3 is 6.0 m² or more. 2 If the amount is less than / g, the mixing of each raw material becomes non-uniform, reducing the sinterability of the ferrite magnetic powder, and preventing the acquisition of a high sinter density during low-temperature sintering. The BET specific surface area of ​​Fe2O3 is 6.5 to 40.0 m². 2 / g, more preferably still 7.0 to 30.0 m 2 / g. The BET specific surface area of Fe₂O₃ can be controlled in the Fe₂O₃ synthesis step, firing step, pulverization and other steps.

[0031] Furthermore, in the present invention, since no sintering aid is added during the production of the Ni-Zn-Cu ferrite powder, non-uniform grain growth can be suppressed.

[0032] Next, the Ni-Zn-Cu ferrite sintered body according to the present invention will be described.

[0033] It is preferable that the sintered density of the ferrite sintered body is high even during low-temperature sintering. For example, even during low-temperature firing at about 860°C, the sintered density is 5.00 g / cm 3 or higher. When the sintered density is less than 5.00 g / cm 3 , sufficient electromagnetic properties cannot be obtained, and the mechanical strength of the sintered body becomes low, which is not preferable. The upper limit of the sintered density is about 5.40 g / cm 3 .

[0034] The Ni-Zn-Cu ferrite sintered body according to the present invention is obtained by sintering, at a temperature of 840 to 1050°C for 1 to 20 hours, preferably 1 to 10 hours, either a molded body obtained by a so-called powder compression molding method in which the Ni-Zn-Cu ferrite powder according to the present invention is compressed using a mold under a pressure of 0.3 to 3.0 × 10 4 t / m 2 , or a layered body obtained by a so-called green sheet method in which green sheets containing the Ni-Zn-Cu ferrite powder according to the present invention are laminated. As the molding method, a known method can be used, and the above powder compression molding method and green sheet method are preferable.

[0035] If the sintering temperature is below 840°C, the sintering density decreases, resulting in insufficient electromagnetic properties and reduced mechanical strength of the sintered body. If the sintering temperature exceeds 1050°C, deformation is more likely to occur in the sintered body, making it difficult to obtain a sintered body of the desired shape. Furthermore, in the case of multilayer chip inductors, for example, since the electrode material such as Ag, Ag-Pd, and the ferrite laminate are fired simultaneously, interdiffusion at the interface between the electrode and the ferrite can cause electrode breakage and deterioration of the ferrite's inherent properties. A more preferable sintering temperature is 860 to 1040°C.

[0036] The Ni-Zn-Cu ferrite sintered body according to the present invention can be used as a magnetic material for multilayer chip inductors, inductance elements, and other electronic components by shaping it into a predetermined form depending on the application.

[0037] Next, we will describe the green sheet in this invention.

[0038] A green sheet is a sheet obtained by mixing the above-mentioned Ni-Zn-Cu ferrite powder with a binder, plasticizer, and solvent to form a coating, depositing the coating to a thickness of several micrometers to several hundred micrometers using a doctor blade coater, and then drying it. After stacking these sheets and applying pressure, a laminate is formed, and depending on the application, the laminate can be sintered at a predetermined temperature to obtain multilayer chip inductors, inductance elements, and other electronic components.

[0039] The green sheet in this invention contains 2 to 20 parts by weight of a binder and 0.5 to 15 parts by weight of a plasticizer per 100 parts by weight of the Ni-Zn-Cu ferrite powder according to the present invention. Preferably, it contains 4 to 15 parts by weight of a binder and 1 to 10 parts by weight of a plasticizer. In addition, residual solvent may remain due to insufficient drying after film formation. Furthermore, known additives such as viscosity modifiers may be added as needed.

[0040] The types of binding materials include polyvinyl butyral, polyacrylic acid ester, polymethyl methacrylate, vinyl chloride, polymethacrylate ester, ethylene cellulose, and abietic acid resin. The preferred binding material is polyvinyl butyral.

[0041] If the amount of binding material is less than 2 parts by weight, the green sheet will become brittle, and a content exceeding 20 parts by weight is not necessary to provide sufficient strength.

[0042] Examples of plasticizers include benzyl-n-butyl phthalate, butyl butylphthalylglycolate, dibutyl phthalate, dimethyl phthalate, polyethylene glycol, phthalate esters, butyl stearate, and methyl agitate.

[0043] If the amount of plasticizer is less than 0.5 parts by weight, the green sheet will become hard and prone to cracking. If the amount of plasticizer exceeds 15 parts by weight, the green sheet will become soft and difficult to handle.

[0044] In the production of the green sheet according to the present invention, 15 to 150 parts by weight of solvent are used per 100 parts by weight of Ni-Zn-Cu ferrite powder. If the solvent is outside the above range, a uniform green sheet cannot be obtained, and the multilayer chip inductors, inductance elements, and other electronic components obtained by sintering this sheet tend to have variations in characteristics.

[0045] The types of solvents include acetone, benzene, butanol, ethanol, methyl ethyl ketone, toluene, propyl alcohol, isopropyl alcohol, n-butyl acetate, and 3-methyl-3-methoxy-1-butanol.

[0046] The stacking pressure is 0.2 × 10 4 ~0.6 × 10 4 t / m 2 It is preferable.

[0047] Next, we will describe the ferrite sheet according to the present invention.

[0048] In this invention, a Ni-Zn-Cu ferrite sintered body can be used in the form of a plate to create a ferrite sheet.

[0049] The thickness of the plate-shaped ferrite sintered body in the present invention is preferably 0.01 to 1 mm. More preferably 0.02 to 1 mm, and even more preferably 0.03 to 0.5 mm.

[0050] In the ferrite sheet according to the present invention, an adhesive layer can be provided on at least one surface of the ferrite sintered plate. The thickness of the adhesive layer is preferably 0.001 to 0.1 mm.

[0051] In the ferrite sheet according to the present invention, a protective layer can be provided on at least one surface of the ferrite sintered plate. The thickness of the protective layer is preferably 0.001 to 0.1 mm.

[0052] Examples of the adhesive layer in the present invention include double-sided adhesive tape. The double-sided adhesive tape is not particularly limited, and known double-sided adhesive tapes can be used. Alternatively, the adhesive layer may be formed by sequentially laminating an adhesive layer, a flexible and stretchable film or sheet, an adhesive layer, and a release sheet on one side of a ferrite sintered plate.

[0053] The protective layer in this invention enhances reliability and durability against powder fallout when the ferrite sintered plate is divided. The protective layer is not particularly limited as long as it is made of a resin that stretches without breaking when the ferrite sheet is bent, and examples include PET film.

[0054] The ferrite sheet according to the present invention may be configured to be separable from at least one groove pre-formed on at least one surface of the ferrite sintered plate, in order to adhere it closely to a bent portion and to prevent cracking during use. The groove may be continuous or intermittently formed, and a number of minute recesses can be used as a substitute for the groove. The groove preferably has a U-shaped or V-shaped cross-section.

[0055] In order to adhere the ferrite sheet according to the present invention to a bent portion and to prevent it from cracking during use, it is preferable to pre-divide the ferrite sintered plate into small pieces. For example, the ferrite sintered plate may be divided using at least one groove provided on at least one surface of the ferrite sintered plate as a starting point, or the ferrite sintered plate may be divided into small pieces without forming grooves.

[0056] The ferrite sintered plate is divided into triangles, quadrilaterals, polygons, or combinations thereof of any size by grooves. For example, the length of one side of a triangle, quadrilateral, or polygon is usually 1 to 12 mm, and if the bonding surface of the object to be attached is curved, it is preferably 1 mm or more and 1 / 3 or less of the radius of curvature, more preferably 1 mm or more and 1 / 4 or less. When grooves are formed, the plate can adhere closely or substantially to flat surfaces, cylindrical curved surfaces, and surfaces with some irregularities without irregular cracking outside the grooves.

[0057] The width of the groove opening formed in the ferrite sintered plate is usually 250 μm or less, and more preferably 1 to 150 μm. If the opening width exceeds 250 μm, the decrease in magnetic permeability of the ferrite sintered plate becomes large and undesirable. The depth of the groove is usually 1 / 20 to 3 / 5 of the thickness of the ferrite sintered plate. In the case of a thin sintered ferrite plate with a thickness of 0.1 mm to 0.2 mm, the depth of the groove is preferably 1 / 20 to 1 / 4, more preferably 1 / 20 to 1 / 6 of the thickness of the sintered ferrite plate. [Examples]

[0058] The present invention will be specifically described below with reference to examples of the present invention.

[0059] [Measurement of specific surface area of ​​Fe2O3 raw material] The specific surface area of ​​the Fe2O3 raw materials was measured using the BET method with "Macsorb HM model-1208" (manufactured by Mounttech Co., Ltd.). The specific surface areas of each Fe2O3 raw material used in the examples and comparative examples are shown in Table 1.

[0060] [Measurement of ferrite composition] The composition of the ferrite calcined powder for the ferrite core mentioned above was measured using a multi-element simultaneous X-ray fluorescence analyzer, Simultix 14 (Rigaku Corporation).

[0061] [Identification and quantification of crystalline phases] The crystalline phases constituting the ferrite were evaluated using D8 ADVANCE.

[0062] [Crystallite size, strain, lattice constant] The crystallite size, strain, and lattice constant of the ferrite were evaluated using D8 ADVANCE with TOPAS software Ver.4, in the same manner as described above for X-ray diffraction.

[0063] [Measurement of the magnetic properties of ferrite cores] The powder, prepared by mixing 15g of ferrite calcined powder for the ferrite core mentioned above with 1.5mL of a 6.5% diluted PVA aqueous solution, is placed into a mold with an outer diameter of 20mmφ and an inner diameter of 10mmφ, and pressed using a press machine at a rate of 1 ton / cm². 2 By compressing the material and firing it at 860, 880, 900, and 920°C for 2 hours, a ferrite ring core was obtained for measuring the initial magnetic permeability.

[0064] The initial permeability of the ring core was measured at frequencies of 100 kHz and 1 MHz using an impedance / material analyzer E4991A (manufactured by Agilent Technologies, Inc.).

[0065] [Measurement of sintering density of ferrite core] The sintering density of the ferrite sintered body used for the aforementioned magnetic property measurement was determined by measuring the outer diameter, inner diameter, and weight, and then calculating the result.

[0066] Example 1: Each oxide raw material was weighed to obtain the desired composition of Ni-Zn-Cu ferrite, and after wet mixing, the mixed slurry was filtered and dried to obtain a raw material mixed powder (iron oxide (1) from Table 1 was used as the Fe2O3 raw material). The raw material mixed powder was calcined in air at 750-850°C for 2 hours, and the resulting calcined product was pulverized with a vibratory mill to obtain the Ni-Zn-Cu ferrite powder according to the present invention. The composition, crystallite size, strain, and lattice constant of the obtained powder are shown in Table 2.

[0067] The obtained Ni-Zn-Cu ferrite powder was molded into a body using the method described above. The sinter density and initial permeability (100 kHz, 1 MHz) of the ferrite sintered body obtained by sintering this molded body in air at a sintering temperature of 860-920°C for 2 hours are shown in Table 2.

[0068] XRD evaluation of the obtained Ni-Zn-Cu ferrite confirmed that it was a single-phase spinel ferrite.

[0069] Examples 2 and 3: Ni-Zn-Cu ferrite powder was obtained in the same manner as in Example 1, except for various changes in the composition range. The composition, crystallite size, and strain of the obtained Ni-Zn-Cu ferrite powder are shown in Table 2. The sintering density and initial permeability (100 kHz, 1 MHz) of the ferrite sintered body prepared in the same manner as in Example 1 using the obtained Ni-Zn-Cu ferrite powder are also shown in Table 2.

[0070] Examples 4 and 5: Ni-Zn-Cu-Co ferrite powder was obtained in the same manner as in Example 1, except that the composition range was varied and Co was added. The composition, crystallite size, and strain of the obtained Ni-Zn-Cu-Co ferrite powder are shown in Table 2. The sintering density and initial permeability (100 kHz, 1 MHz) of ferrite sintered bodies prepared in the same manner as in Example 1 using the obtained Ni-Zn-Cu-Co ferrite powder are also shown in Table 2.

[0071] Comparative Example 1: Ni-Zn-Cu ferrite powder was obtained in the same manner as in Example 1, except for various changes in the composition range. The composition, crystallite size, and strain of the obtained Ni-Zn-Cu ferrite powder are shown in Table 2. The sintering density and initial permeability (100 kHz, 1 MHz) of the ferrite sintered body prepared in the same manner as in Example 1 using the obtained Ni-Zn-Cu ferrite powder are also shown in Table 2.

[0072] Comparative Example 2: Ni-Zn-Cu ferrite powder was obtained in the same manner as in Example 1, except that iron oxide raw material (2) in Table 1 was used as the Fe2O3 raw material. The composition, crystallite size, and strain of the obtained Ni-Zn-Cu ferrite powder are shown in Table 2. The sintering density and initial permeability (100 kHz, 1 MHz) of the ferrite sintered body prepared in the same manner as in Example 1 using the obtained Ni-Zn-Cu ferrite powder are also shown in Table 2.

[0073] Comparative Example 3: Ni-Zn-Cu ferrite powder was obtained in the same manner as in Example 1, except that iron oxide raw material (3) in Table 1 was used as the Fe2O3 raw material. The composition, crystallite size, and strain of the obtained Ni-Zn-Cu ferrite powder are shown in Table 2. The sintering density and initial permeability (100 kHz, 1 MHz) of the ferrite sintered body prepared in the same manner as in Example 1 using the obtained Ni-Zn-Cu ferrite powder are also shown in Table 2.

[0074] Comparative Example 4: Ni-Zn-Cu ferrite powder was obtained in the same manner as in Example 1, except that iron oxide raw material (4) in Table 1 was used as the Fe2O3 raw material. The composition, crystallite size, and strain of the obtained Ni-Zn-Cu ferrite powder are shown in Table 2. The sintering density and initial permeability (100 kHz, 1 MHz) of the ferrite sintered body prepared in the same manner as in Example 1 using the obtained Ni-Zn-Cu ferrite powder are also shown in Table 2.

[0075] Comparative Example 5: Ni-Zn-Cu-Co ferrite powder was obtained in the same manner as in Example 4, except that iron oxide raw material (2) in Table 1 was used as the Fe2O3 raw material. The composition, crystallite size, and strain of the obtained Ni-Zn-Cu-Co ferrite powder are shown in Table 2. The sintering density and initial permeability (100 kHz, 1 MHz) of the ferrite sintered body prepared in the same manner as in Example 1 using the obtained Ni-Zn-Cu-Co ferrite powder are also shown in Table 2.

[0076] Comparative Example 6: Ni-Zn-Cu-Co ferrite powder was obtained in the same manner as in Example 5, except that iron oxide raw material (2) in Table 1 was used as the Fe2O3 raw material. The composition, crystallite size, and strain of the obtained Ni-Zn-Cu-Co ferrite powder are shown in Table 2. The sintering density and initial permeability (100 kHz, 1 MHz) of the ferrite sintered body prepared in the same manner as in Example 1 using the obtained Ni-Zn-Cu-Co ferrite powder are also shown in Table 2.

[0077] [Table 1]

[0078] [Table 2]

[0079] The Ni-Zn-Cu ferrite powder according to the present invention achieves a sintering density of 5.00 g / cm³ even when sintered at a low temperature such as 860°C. 3Furthermore, when comparing the magnetic permeability at 100 kHz and 1 MHz at the same sintering temperature, it is higher than that of the comparative example. Therefore, it is suitable as a precursor for ferrite sintered bodies and ferrite sheets, and is also suitable as magnetic powder for multilayer chip inductors, inductance elements, and other electronic components.

Claims

1. Fe ２ O ３ A Ni-Zn-Cu ferrite powder containing 45-49 mol% of ZnO, 5-25 mol% of NiO, 15-40 mol% of ZnO, 5-15 mol% of CuO, and 0-3 mol% of CoO, with a crystallite size of 180 nm or less, characterized in that the Ni-Zn-Cu ferrite powder is a single-phase spinel ferrite.

2. The Ni-Zn-Cu ferrite powder according to claim 1, wherein the strain is 0.330 or less.

3. A sintered body using the Ni-Zn-Cu ferrite powder described in claim 1 or 2.

4. A ferrite sheet using the Ni-Zn-Cu ferrite powder described in claim 1 or 2.

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