JP2023158013A - Ni-Zn-Cu-BASED FERRITE POWDER, SINTERED COMPACT, FERRITE SHEET - Google Patents

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

The present invention relates to a Ni-Zn-Cu-based ferrite material, and relates to a ferrite powder that can be sintered at low temperatures.The present invention also relates to a sintered body and a ferrite sheet using the ferrite powder. .

In recent years, household and industrial electronic devices have become smaller and lighter, and as a result, there has been a growing need for smaller, more efficient, and higher frequency electronic components used in the various electronic devices mentioned above. There is.

For example, inductors used in the electronic circuits of electronic devices have evolved from wire-wound types, in which a coil is formed by winding copper wire with an insulating coating around a magnetic core or air-core bobbin, to ferrite sintered multilayer chip inductors, which have been put into practical use. ing.

This multilayer chip inductor is manufactured through the following manufacturing steps. That is, after forming a conductive pattern by printing or the like using a paste containing an electrode material such as Ag or Ag-Pd on a green sheet formed by forming a sheet of paste containing ferrite powder, these are laminated, It is manufactured through a process of sintering at a predetermined temperature to form external electrodes.

By the way, as mentioned above, in the manufacturing process of the multilayer chip inductor, since the method of co-firing the laminate of the electrode material and ferrite is adopted, the interfacial reaction between the electrode material such as Ag or Ag-Pd and the ferrite ( The problem is that the original characteristics of ferrite deteriorate due to mutual diffusion (interdiffusion), and in order to avoid this problem, it is said that it is necessary to sinter at a low temperature of about 900° C. or lower.

However, when firing at a temperature of 900° C. or lower, it is difficult to obtain a Ni-based ferrite sintered body having excellent electromagnetic properties such as magnetic permeability as a magnetic material for a multilayer chip inductor.

Up to now, several techniques have been proposed for Ni--Zn--Cu based ferrite powder that can be sintered even at low temperatures. For example, there is a method of adding borosilicate glass, which is a sintering aid, to generate a liquid phase during sintering and promoting the growth of ferrite particles (Patent Document 1), and another method of adding a glass component is SiO There is a method of adding a glass component consisting of ₂ , B ₂ O ₃ and Na ₂ O to form liquid phase sintering and promoting the growth of ferrite particles (Patent Document 2). There is also a method of forming liquid phase sintering and promoting ferrite particle growth by adding PbO, which has a large environmental impact, and a glass component that does not contain Na, which reduces the magnetic permeability of ferrite and has a negative impact on electronic devices. (Patent Document 3). Furthermore, for RFID applications, there is a method of controlling the half width of the XRD diffraction peak of the crystal phase of Ni-Zn-Cu-based ferrite powder to achieve high magnetic permeability (Patent Document 4).

Japanese Patent Application Publication No. 5-326241 Japanese Patent Application Publication No. 2000-208316 Japanese Patent Application Publication No. 2007-99539 Japanese Patent Application Publication No. 2005-64468

All of Patent Documents 1 to 3 adopt a method of forming liquid phase sintering by adding a glass component to promote ferrite particle growth. However, the amount of these additives added is very small, and it is difficult to uniformly disperse them, which promotes non-uniform growth of ferrite particles. Further, in Patent Document 4, although no sintering aid is added, it is necessary to sinter at a high temperature of 1060° C. or higher, and sintering at a low temperature is not considered.

Therefore, in order to solve the problems in the prior art described above, the present invention aims to provide a Ni--Zn--Cu based ferrite powder that can be sintered at low temperatures.

The above technical problem can be achieved by the present invention as follows.

That is, in the present invention, Fe ₂ O ₃ is 45 to 49 mol%, NiO is 5 to 25 mol%,
It is a Ni-Zn-Cu-based ferrite powder characterized by containing 15 to 40 mol% of ZnO, 5 to 15 mol% of CuO, and 0 to 3 mol% of CoO, and having a crystallite size of 180 nm or less (invention 1). ).

Further, the present invention is the Ni-Zn-Cu-based ferrite powder according to Invention 1, which has a strain of 0.330 or less (Invention 2).

The present invention also provides the Ni-Zn-Cu-based ferrite powder according to the present invention 1 or the present invention 2, which has a sintered density of 5.00 g/cm ³ or more when fired at 860° C. in the atmosphere ( Present invention 3).

Further, the present invention is a sintered body using the Ni-Zn-Cu-based ferrite powder according to any one of Inventions 1 to 3 (Invention 4).

Further, the present invention is a ferrite sheet using the Ni-Zn-Cu-based ferrite powder according to any one of Inventions 1 to 3 (Invention 5).

Since the Ni-Zn-Cu-based ferrite powder according to the present invention has a small crystallite size, a ferrite sintered body with a high sintered density can be obtained even when sintered at a low temperature. In addition, since the Ni-Zn-Cu-based 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 in which Ag and magnetic powder are co-fired, it is possible to sinter the powder with a low melting point. It is expected that the diffusion of Ag can be suppressed and the inductor performance will be improved.

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

The Ni--Zn--Cu-based ferrite powder according to the present invention contains Fe, Ni, Zn, and Cu, and if necessary, Co as constituent metal elements. When each of the constituent metal elements is converted into Fe ₂ O ₃ , NiO, ZnO, CuO and CoO, based on the total (100%) of Fe ₂ O ₃ , NiO, ZnO, CuO and CoO, Fe ₂ O ₃ 49 mol% or less, NiO 5 to 25 mol%, ZnO 15 to 40 mol%, CuO 5 to 15 mol%, and CoO 0 to 3 mol%.

The Fe content of the Ni-Zn-Cu-based ferrite powder according to the present invention is 49 mol% or less in terms of Fe ₂ O ₃ . When the Fe content exceeds 49 mol%, sinterability is significantly reduced. The Fe content is preferably 48.9 mol% or less, more preferably 48.8 mol% or less. The lower limit is about 45 mol%.

The Ni content of the Ni-Zn-Cu-based 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. Further, the Curie temperature decreases, which limits the usable temperature range, which is not preferable. It is also not preferable that the Ni content exceeds 25 mol% because μ' decreases. The Ni content is preferably 6 to 24.9 mol%, more preferably 7 to 24.8 mol%.

The Zn content of the Ni-Zn-Cu-based ferrite powder according to the present invention is 15 to 40 mol% in terms of ZnO. If the Zn content is less than 15 mol%, μ' decreases, which is not preferable. Further, the Curie temperature decreases, which limits the usable temperature range, which is not preferable. It is also not preferable that the Zn content exceeds 40 mol% because μ' decreases. Zn content is preferably 18 to 38 mol%, more preferably 20 to 35 mol%

The Cu content of the Ni--Zn--Cu based ferrite powder according to the present invention is 5 to 15 mol% in terms of CuO. When the Cu content is less than 5 mol%, sinterability decreases, making it difficult to produce a sintered body at low temperatures. If the Cu content exceeds 15 mol%, μ' decreases, which is not preferable. The content of Cu is preferably 6 to 14 mol%, more preferably 7 to 13 mol%.

The Ni--Zn--Cu based 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, since the snake limit line is shifted to the high frequency side due to the ferrite containing Co, the ferrite core is the ratio of the real part μ' to the imaginary part μ' of complex magnetic permeability in the high frequency range. It is possible to improve the Q (μ′/μ”) of However, when the Co content exceeds 3 mol % in terms of CoO, the magnetic 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%.

The Ni--Zn--Cu based 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 promoted at the magnetic powder stage, so when firing a sintered body or green sheet, the sinterability decreases, making it impossible to sinter at low temperatures. . More preferably, it is 175 nm or less, and even more preferably 170 nm or less. The lower limit is about 100 nm.

The Ni--Zn--Cu based ferrite powder according to the present invention preferably has a crystal strain of 0.330 or less. If the strain exceeds 0.330, μ' may decrease, which is not preferable. It is more preferably 0.325 or less, even more preferably 0.320 or less. The lower limit is about 0.100. Note that the Ni--Zn--Cu based ferrite powder according to the present invention is preferably a spinel ferrite single phase.

The Ni--Zn--Cu based ferrite powder according to the present invention may contain various elements at impurity levels in addition to the above-mentioned elements as long as the properties thereof are not affected. It is generally known that adding Bi has the effect of lowering the sintering temperature of ferrite. However, when the dispersion state of Bi is non-uniform, it is not preferable to actively add Bi because it promotes non-uniform growth of particles during firing, and 0 ppm is preferable.

The Ni--Zn--Cu-based ferrite powder according to the present invention may contain Si as an unavoidable impurity with an upper limit of 500 ppm in terms of SiO ₂ . It is preferable not to contain Sn or the like (0 ppm).

The Ni-Zn-Cu-based ferrite powder according to the present invention is produced by mixing raw materials such as oxides, carbonates, hydroxides, and oxalates of each element constituting ferrite in a predetermined composition ratio using a conventional method. The obtained raw material mixture or the coprecipitate obtained by precipitating each element in an aqueous solution is calcined in the air at a temperature range of 650 to 950°C for 1 to 20 hours, and then pulverized. be able to. The temperature for pre-firing is preferably 700 to 940°C.

In the present invention, it is preferable that the BET specific surface area of Fe ₂ O ₃ as the Fe raw material is 6.0 m ² /g or more. When the BET specific surface area of Fe ₂ O ₃ is less than 6.0 m ² /g, the mixing of each raw material becomes uneven, the sinterability of the ferrite magnetic powder decreases, and it becomes difficult to obtain a high sintered density during low-temperature sintering. I can't. The BET specific surface area of Fe ₂ O ₃ is more preferably 6.5 to 40.0 m ² /g, even more preferably 7.0 to 30.0 m ² /g. Note that the BET specific surface area of Fe ₂ O ₃ can be controlled by the synthesis stage, calcination stage, pulverization, etc. of Fe ₂ O ₃ .

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

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

The sintered density of the ferrite sintered body is preferably 5.00 g/cm ³ or higher even when sintered at a low temperature, for example, 860° C. or higher. If 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 .

The Ni-Zn-Cu ferrite sintered body according to the present invention is produced by molding the Ni-Zn-Cu ferrite powder according to the present invention in a mold at a rate of 0.3 to 3.0×10 ⁴ t/m ^{2 .} A molded body obtained by the so-called powder pressure molding method, which is applied with pressure, or a molded body obtained by the so-called green sheet method, which is laminated with green sheets containing the Ni-Zn-Cu ferrite powder according to the present invention. The laminate can be obtained by sintering the laminate at 840 to 1050°C for 1 to 20 hours, preferably 1 to 10 hours. As the molding method, any known method can be used, but the powder pressure molding method and green sheet method described above are preferred.

If the sintering temperature is less than 840°C, the sintered density will decrease, so sufficient electromagnetic properties will not be obtained, and the mechanical strength of the sintered body will decrease. If the sintering temperature exceeds 1050°C, the sintered body is likely to be deformed, making it difficult to obtain a sintered body with a desired shape. In addition, for example, in the case of a multilayer chip inductor, since a laminate of electrode materials such as Ag or Ag-Pd and ferrite are fired at the same time, an interfacial reaction (mutual diffusion) between the electrode and ferrite may cause disconnection of the electrode and deterioration of the original characteristics of ferrite. do. A more preferred sintering temperature is 860-1040°C.

The Ni--Zn--Cu-based ferrite sintered body according to the present invention can be used as a magnetic material for laminated chip inductors, inductance elements, and other electronic components by shaping it into a predetermined shape depending on the purpose.

Next, the green sheet in the present invention will be described.

Green sheet is a paint made by mixing the above Ni-Zn-Cu ferrite powder with a binding material, a plasticizer, a solvent, etc., and the paint is coated with a doctor blade coater etc. to a thickness of several μm to several hundred μm. This sheet is formed by forming a film and then drying it. After stacking these sheets, they are pressurized to form a laminate, and depending on the application, the laminate is sintered at a predetermined temperature to obtain multilayer chip inductors, inductance elements, and other electronic components.

The green sheet in the present invention contains 2 to 20 parts by weight of a binding material 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 binding material and 1 to 10 parts by weight of plasticizer. Further, solvent may remain due to insufficient drying after film formation. Furthermore, known additives such as a viscosity modifier may be added as necessary.

Types of bonding materials include polyvinyl butyral, polyacrylic ester, polymethyl methacrylate, vinyl chloride, polymethacrylic ester, ethylene cellulose, abietic acid resin, and the like. A preferred bonding material is polyvinyl butyral.

If the binding material is less than 2 parts by weight, the green sheet will become brittle, and in order to have strength, it is not necessary to have a content exceeding 20 parts by weight.

Types of plasticizers include benzyl-n-butyl phthalate, butyl phthalyl glycolate, dibutyl phthalate, dimethyl phthalate, polyethylene glycol, phthalate ester, butyl stearate, methyl agitate, and the like.

If the amount of plasticizer is less than 0.5 parts by weight, the green sheet becomes hard and cracks are likely to occur. If the amount of plasticizer exceeds 15 parts by weight, the green sheet becomes soft and difficult to handle.

In producing the green sheet according to the present invention, 15 to 150 parts by weight of a solvent is used per 100 parts by weight of Ni-Zn-Cu ferrite powder. If the solvent is outside the above range, a uniform green sheet will not be obtained, and the multilayer chip inductors, inductance elements, and other electronic components obtained by sintering the green sheet will likely have varying characteristics.

Examples of the solvent include acetone, benzene, butanol, ethanol, methyl ethyl ketone, toluene, propyl alcohol, isopropyl alcohol, n-butyl acetate, 3-methyl-3-methoxy-1-butanol, and the like.

The lamination pressure is preferably 0.2×10 ⁴ to 0.6×10 ⁴ t/m ² .

Next, the ferrite sheet according to the present invention will be described.

In the present invention, a ferrite sheet can be obtained by using a Ni--Zn--Cu ferrite sintered body in the form of a plate.

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, still more preferably 0.03 to 0.5 mm.

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

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

Examples of the adhesive layer in the present invention include double-sided adhesive tape. The double-sided adhesive tape is not particularly limited, and any known double-sided adhesive tape may be used. Alternatively, the adhesive layer may be one in which an adhesive layer, a flexible and stretchable film or sheet, an adhesive layer, and a release sheet are sequentially laminated on one side of a sintered ferrite plate.

By providing the protective layer in the present invention, reliability and durability against powder falling off when the sintered ferrite plate is divided can be improved. The protective layer is not particularly limited as long as it is a resin that stretches without breaking when the ferrite sheet is bent, and examples thereof include PET film and the like.

The ferrite sheet according to the present invention has at least one groove formed in advance on at least one surface of the ferrite sintered plate as a starting point in order to stick it tightly to a bent part and to prevent it from cracking during use. The sintered ferrite plate may be configured to be separable. The grooves may be continuous or discontinuously formed, and may be substituted for grooves by forming a large number of minute recesses. The groove preferably has a U-shaped or V-shaped cross section.

For the ferrite sheet according to the present invention, it is preferable to divide the ferrite sintered plate into small pieces in advance in order to adhere the ferrite sheet closely to the bent portion and to prevent it from breaking during use. For example, the ferrite sintered plate may be divided in advance 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 any grooves. Any of the following methods may be used.

The sintered ferrite plate is divided into triangles, quadrilaterals, polygons, or combinations thereof of arbitrary 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 surface to be adhered to is a curved surface, it is preferably 1 mm or more and 1/3 or less of the radius of curvature. More preferably, it is 1 mm or more and 1/4 or less. When a groove is formed, it can adhere or substantially adhere to not only a flat surface but also a cylindrical curved side surface and a somewhat uneven surface without being broken into irregular shapes at locations other than the groove.

The width of the opening of the groove formed in the sintered ferrite plate is usually preferably 250 μm or less, more preferably 1 to 150 μm. If the width of the opening exceeds 250 μm, the magnetic permeability of the sintered ferrite plate will decrease significantly, which is not preferable. Further, the depth of the groove is usually 1/20 to 3/5 of the thickness of the sintered ferrite plate. In addition, 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 1/4 of the thickness of the sintered ferrite plate. It is 20 to 1/6.

EXAMPLES Below, Examples of the present invention will be shown to specifically explain the present invention.

[Measurement of specific surface area of Fe ₂ O ₃ raw material]
The specific surface area of the Fe ₂ O ₃ raw material was measured by the BET method using "Macsorb HM model-1208" (manufactured by Mountech Co., Ltd.). Table 1 shows the specific surface area of each Fe ₂ O ₃ raw material used in Examples and Comparative Examples.

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

[Identification and quantification of crystal phase]
The crystal phase constituting ferrite was evaluated using D8 ADVANCE.

[Crystallite size, strain, lattice constant]
The crystallite size, strain, and lattice constant of ferrite were determined using D8 ADVANCE using TOPAS software Ver. Evaluation was made at 4.

[Measurement of magnetic properties of ferrite core]
A powder mixture of 15 g of the above-mentioned calcined ferrite powder for the ferrite core and 1.5 mL of a 6.5% diluted PVA aqueous solution was put into a mold with an outer diameter of 20 mmφ and an inner diameter of 10 mmφ, and a press machine was used to produce a powder of 1 ton/cm. ² and fired at 860, 880, 900, and 920°C for 2 hours to obtain a ferrite ring core for measuring initial magnetic permeability.

The initial magnetic 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).

[Measurement of sintered density of ferrite core]
The sintered density of the ferrite sintered body for measuring magnetic properties was determined by measuring the outer diameter, inner diameter, and weight.

Example 1:
Each oxide raw material was weighed and wet-mixed so that the composition of Ni-Zn-Cu ferrite would be a predetermined composition, and then the mixed slurry was filtered and dried to obtain a raw material mixed powder (Fe ₂ As the O ₃ raw material, iron oxide (1) shown in Table 1 was used). The raw material mixed powder was fired at 750 to 850° C. for 2 hours in the air, and the resulting pre-fired product was pulverized with a vibration mill to obtain Ni--Zn--Cu ferrite powder according to the present invention. The composition, crystallite size, strain, and lattice constant of the obtained powder are listed in Table 2.

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

Evaluation of the obtained Ni-Zn-Cu ferrite by XRD confirmed that it was a single phase of spinel ferrite.

Examples 2 and 3:
Ni--Zn--Cu ferrite powder was obtained in the same manner as in Example 1 except that the composition range was variously changed. The composition, crystallite size, and strain of the obtained Ni--Zn--Cu ferrite powder are listed in Table 2. Table 2 also shows the sintered density and initial permeability (100 kHz, 1 MHz) of a ferrite sintered body produced in the same manner as in Example 1 using the obtained Ni--Zn--Cu ferrite powder.

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 variously changed and Co was added. The composition, crystallite size and strain of the obtained Ni-Zn-Cu-Co ferrite powder are listed in Table 2. Table 2 also lists the sintered density and initial permeability (100kHz, 1MHz) of a ferrite sintered body produced in the same manner as in Example 1 using the obtained Ni-Zn-Cu-Co ferrite powder.

Comparative example 1:
Ni--Zn--Cu ferrite powder was obtained in the same manner as in Example 1 except that the composition range was variously changed. The composition, crystallite size, and strain of the obtained Ni--Zn--Cu ferrite powder are listed in Table 2. Table 2 also shows the sintered density and initial permeability (100 kHz, 1 MHz) of a ferrite sintered body produced in the same manner as in Example 1 using the obtained Ni--Zn--Cu ferrite powder.

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 Fe ₂ O ₃ raw material. The composition, crystallite size, and strain of the obtained Ni--Zn--Cu ferrite powder are listed in Table 2. Table 2 also shows the sintered density and initial permeability (100 kHz, 1 MHz) of a ferrite sintered body produced in the same manner as in Example 1 using the obtained Ni--Zn--Cu ferrite powder.

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 Fe ₂ O ₃ raw material. The composition, crystallite size, and strain of the obtained Ni--Zn--Cu ferrite powder are listed in Table 2. Table 2 also shows the sintered density and initial permeability (100 kHz, 1 MHz) of a ferrite sintered body produced in the same manner as in Example 1 using the obtained Ni--Zn--Cu ferrite powder.

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 Fe ₂ O ₃ raw material. The composition, crystallite size, and strain of the obtained Ni--Zn--Cu ferrite powder are listed in Table 2. Table 2 also shows the sintered density and initial permeability (100 kHz, 1 MHz) of a ferrite sintered body produced in the same manner as in Example 1 using the obtained Ni--Zn--Cu ferrite powder.

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 Fe ₂ O ₃ raw material. The composition, crystallite size and strain of the obtained Ni-Zn-Cu-Co ferrite powder are listed in Table 2. Table 2 also lists the sintered density and initial permeability (100kHz, 1MHz) of a ferrite sintered body produced in the same manner as in Example 1 using the obtained Ni-Zn-Cu-Co ferrite powder.

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 Fe ₂ O ₃ raw material. The composition, crystallite size and strain of the obtained Ni-Zn-Cu-Co ferrite powder are listed in Table 2. Table 2 also lists the sintered density and initial permeability (100kHz, 1MHz) of a ferrite sintered body produced in the same manner as in Example 1 using the obtained Ni-Zn-Cu-Co ferrite powder.

The Ni-Zn-Cu ferrite powder according to the present invention has a sintered density of 5.00 g/cm ³ or more even when sintered at a low temperature such as 860°C, and has a magnetic permeability at 100 kHz and 1 MHz. When compared 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 as a magnetic powder for laminated chip inductors, inductance elements, and other electronic components.

That is, the present invention contains 45 to 49 mol% of Fe ₂ O ₃ , 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, and the crystallite size is 180 nm or less, the Ni-Zn-Cu ferrite powder is characterized in that the Ni-Zn-Cu ferrite powder is a single phase spinel ferrite (the present invention) 1).

Claims (5)

Contains 45 to 49 mol% of Fe ₂ O ₃ , 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, and has a crystallite size of 180 nm or less. Characteristic Ni-Zn-Cu ferrite powder. The Ni-Zn-Cu-based ferrite powder according to claim 1, which has a strain of 0.330 or less. The Ni-Zn-Cu-based ferrite powder according to claim 1 or 2, which has a sintered density of 5.00 g/cm ³ or more when fired at 860° C. in the atmosphere. A sintered body using the Ni-Zn-Cu ferrite powder according to any one of claims 1 to 3. A ferrite sheet using the Ni-Zn-Cu ferrite powder according to any one of claims 1 to 3.