JP6553833B1 - MnCoZn-based ferrite and method for producing the same - Google Patents

Abstract

Provided is an MnCoZn ferrite having not only good magnetic properties such as high resistance and low coercive force, but also excellent mechanical strength. A MnCoZn-based ferrite composed of a basic component, subcomponents and inevitable impurities, wherein the basic component is iron: 45.0 mol% or more in terms of Fe2O3, less than 50.0 mol%, zinc: 3.0 mol% or more in terms of ZnO , Less than 15.5 mol%, cobalt: 0.5 to 4.0 mol% in terms of CoO and manganese: balance, and as a subcomponent with respect to the basic component, SiO2: 50 to 300 massppm and CaO: 300 to 1300 massppm And the amount of Cd, Pb, Sb, As, Se, Bi, and Zr in the inevitable impurities is suppressed to less than 20 massppm, respectively, so that the Rattler value is less than 0.85% and the coercive force at 100 ° C. is 15 A / m. The specific resistance is 30Ω · m or more and the Curie temperature is 170 ° C or more. 100 ° C., initial permeability of 3000 or more at 1 kHz, and 100 ° C., initial permeability at 1MHz over 2000 and 100 ° C., initial permeability at 10MHz more than 150.

Description

  The present invention relates to a MnCoZn-based ferrite having a high specific resistance, a small coercive force at 100 ° C., which is suitable for use in a vehicle-mounted noise filter, and the like, and a manufacturing method thereof.

A typical example of the soft magnetic oxide magnetic material is MnZn ferrite. Conventional MnZn ferrite contains Fe ²⁺ having a positive magnetic anisotropy of about 2 mass% or more, and cancels out with Fe ³⁺ and Mn ²⁺ having a negative magnetic anisotropy. Achieving low losses.
Since this MnZn ferrite is less expensive than amorphous metal or the like, it is widely used as a noise filter such as a switching power supply, a transformer, and a magnetic core of an antenna.

However, MnZn ferrite, since ^{Fe 2+} amount is ^large, easily occurs electron transfer between Fe 3+ ^{-Fe 2+,} specific resistance has the disadvantage of low and 0.1 [Omega · m order. Therefore, when the frequency region to be used is increased, the loss due to the eddy current flowing in the ferrite increases rapidly, the initial permeability is greatly reduced, and the loss is also increased. For this reason, the service life frequency of MnZn ferrite is limited to about several hundred kHz, and NiZn ferrite is mainly used in the MHz order. The specific resistance of this NiZn ferrite is 10 ⁵ (Ω · m) or more, about 10,000 times that of MnZn ferrite, and has low eddy current loss. Therefore, the characteristics of high initial permeability and low loss are not easily lost even in a high frequency region.

  However, NiZn ferrite has a big problem. This is because soft magnetic materials are required to react sensitively to changes in the external magnetic field, so it is preferable that the coercive force Hc be small. However, NiZn ferrite is composed only of ions having negative magnetic anisotropy. The value of this coercivity is large. The coercive force is defined in JIS C 2560-2.

As a method for obtaining a ferrite having a large specific resistance other than NiZn ferrite, there is a method of increasing the specific resistance by reducing the amount of Fe ²⁺ contained in the MnZn ferrite.
For example, Patent Document 1, Patent Document 2, and Patent Document 3 report MnZn ferrite having a specific resistance increased by reducing the Fe ²⁺ content with Fe ₂ O ₃ component less than 50 mol%. However, since these also consist only of ions having negative magnetic anisotropy like NiZn ferrite, the problem of reducing the coercive force has not been solved at all.

Therefore, techniques for adding Co ²⁺ having positive magnetic anisotropy other than Fe ²⁺ were disclosed in Patent Document 4, Patent Document 5 and Patent Document 6, which are aimed at lowering the coercive force. It was not a thing. Moreover, since the countermeasure to the abnormal grain mentioned later was inadequate, it was inferior also in terms of cost and manufacturing efficiency.

On the other hand, Patent Document 7 reports high resistivity MnCoZn ferrite having low coercivity, which can suppress the appearance of abnormal grains by providing a specified impurity composition, and can be stably manufactured.
In addition, abnormal grain growth is what occurs when the balance of grain growth is broken locally due to some cause, and is a phenomenon often seen in manufacturing using powder metallurgy. In this abnormally grown grain, a substance that greatly impedes the movement of the domain wall, such as impurities and lattice defects, is mixed, so that the soft magnetic property is lost and the coercivity is increased. At the same time, the resistivity decreases due to the insufficient formation of grain boundaries.

Japanese Patent Application Laid-Open No. 7-230909 JP, 2000-277316, A JP 2001-220222 A Patent No. 3418827 gazette Japanese Patent Application Publication No. 2001-220221 JP 2001-68325 A Patent No. 4554960

With the development of Patent Document 7 mentioned above, it has become possible to obtain MnCoZn ferrite which is satisfactory to a certain extent in magnetic characteristics.
On the other hand, there is a remarkable movement of electrification of automobiles in recent years, and although MnCoZn ferrite is also increasingly mounted in automobiles, the mechanical strength is a property regarded as important in the same application. Compared to electrical products and industrial equipment that were the main applications up to that time, automobiles generate vibrations when traveling. Therefore, in automotive applications, ceramics such as MnCoZn ferrite that are not damaged by vibration are required. It has become possible to

However, MnCoZn ferrite with less than 50 mol% of Fe ₂ O ₃ component has few oxygen vacancies, so that sintering is likely to proceed during firing, so that vacancies are likely to remain in crystal grains, and grain boundaries are generated. Is likely to be uneven. As a result, there has been a problem that when subjected to external impact, it tends to be deficient compared to conventional MnCoZn ferrite.
That is, the technique disclosed in Patent Document 7 has a problem in that the obtained magnetic properties are sufficient but the mechanical strength for the defect is not necessarily sufficient.

In addition, when MnCoZn ferrite is used as an on-vehicle noise filter, it is used in a relatively high temperature environment, but there is a concern that the coercive force deteriorates in such a high temperature environment.
For this reason, when used in such a high temperature environment, it is required that the Curie temperature is high and the coercive force at 100 ° C. is low.
However, although Patent Document 7 mentions magnetic properties at 23 ° C., it does not mention magnetic properties at 100 ° C., particularly initial permeability.

  The present invention is expressed by a Rattler value by generating uniform crystal grain boundaries and suppressing abnormal grain growth while maintaining good magnetic properties of high resistance and low coercivity even at 100 ° C. An object of the present invention is to propose MnCoZn ferrite having a mechanical strength called fracture resistance together with its advantageous manufacturing method.

The inventors first examined the appropriate amount of Fe ₂ O ₃ , ZnO, and CoO of MnCoZn ferrite necessary to obtain desirable magnetic properties, and as a result, the specific resistance is high, the coercive force at 100 ° C. is small, and We have found a proper range that can realize all of the characteristics that the Curie temperature is high simultaneously.

Next, paying attention to the microstructure, we found that defects in the sintered core that can be expressed by the Rattler value can be suppressed by reducing the vacancies in the crystal grains, adjusting the crystal grain size, and realizing a grain boundary with an appropriate thickness. . Here, in order to realize a desirable crystal structure, the inventors have succeeded in determining an appropriate amount range of these components based on the recognition that the addition amount of SiO ₂ and CaO, which are segregated components, greatly affects the grain boundaries. . If it is in this range, a low Latler value can be held.

Furthermore, the suppression of abnormal grain appearance, which is essential for combining the preferred magnetic properties and mechanical strength against defects, was examined focusing on the preparation conditions at the time of abnormal grain appearance.
As a result, when the above-mentioned SiO ₂ and CaO are excessive, or contained in natural ore, or mixed during smelting, or a trace amount of additive component used for other MnZn ferrite is insufficient in cleaning of the manufacturing process, etc. It has been found that abnormal grains appear when the respective components such as Cd, Pb, Sb, As, Se, Bi and Zr which are mixed due to the above are contained in a certain amount or more.
The present invention is based on the above findings.

As described above, Patent Document 1, Patent Document 2 and Patent Document 3 refer to high specific resistance, and Patent Document 4, Patent Document 5 and Patent Document 6 show positive magnetic difference. Although there is a description regarding the addition of Co ²⁺ having anisotropy, there is no description regarding the coercive force. In Patent Document 5, on the contrary, it is stipulated that Pb is intentionally added. Furthermore, since there is no description about measures against abnormal particles in these documents, it is presumed that the mechanical strength is also insufficient. In addition, with respect to Patent Document 7 referred to regarding the low coercive force, since the definition of the additive is insufficient, a sufficient mechanical strength capable of suppressing defects cannot be expected.

The essential features of the present invention are as follows.
1. A MnCoZn ferrite comprising a basic component, an accessory component and an unavoidable impurity, wherein
As the basic component,
Iron: 45.0 mol% or more, less than 50.0 mol%, in terms of Fe ₂ O ₃ ,
Zinc: 3.0 mol% or more and less than 15.5 mol% in terms of ZnO,
Cobalt: 0.5 to 4.0 mol% in terms of CoO and manganese: the balance,
With respect to the above basic component, as the above subcomponent,
SiO _2: 50~300massppm and CaO: 300~1300massppm
Including
The amount of Cd, Pb, Sb, As, Se, Bi and Zr in the unavoidable impurities is suppressed to less than 20 massppm,
Furthermore, in the above-mentioned MnCoZn ferrite,
Rattler value is less than 0.85%,
The coercivity at 100 ° C is 15A / m or less,
Resistivity of 30 Ω · m or more,
Curie temperature is 170 ° C or higher,
Initial permeability of 3000 or more at 100 ° C, 1kHz,
An MnCoZn ferrite characterized in that the initial permeability at 100 ° C. and 1 MHz is 2000 or more and the initial permeability at 100 ° C. and 10 MHz is 150 or more.

2. 3. The MnCoZn ferrite according to the above 1, wherein the sintered density of the MnCoZn ferrite is 4.85 g / cm ³ or more.

3. 3. The MnCoZn-based ferrite according to 1 or 2 above, wherein the MnCoZn-based ferrite is a MnCoZn-based ferrite made of a granulated powder-sintered body having a particle size distribution d90 value of more than 150 μm and 300 μm or less.

4. 4. The MnCoZn-based ferrite according to any one of 1 to 3, wherein the MnCoZn-based ferrite is a MnCoZn-based ferrite comprising a granulated powder-sintered body having a crushing strength of more than 1.10 MPa and less than 1.50 MPa. MnCoZn ferrite.

5. A MnCoZn ferrite comprising a basic component, an accessory component and an unavoidable impurity, wherein
As the basic component,
Iron: _Fe 2 _{O 3} in terms of in 45.0Mol% or more and less than 50.0 mol%,
Zinc: 3.0 mol% or more and less than 15.5 mol% in terms of ZnO,
Cobalt: 0.5 to 4.0 mol% in terms of CoO and manganese: the balance,
As a subcomponent with respect to the basic component,
SiO _2: 50~300massppm and CaO: 300~1300massppm
Including
The amount of Cd, Pb, Sb, As, Se, Bi and Zr in the unavoidable impurities is suppressed to less than 20 massppm,
Furthermore, in the above-mentioned MnCoZn ferrite,
Rattler value is less than 0.85%,
The coercivity at 100 ° C is 15A / m or less,
Resistivity of 30 Ω · m or more and Curie temperature of 170 ° C
And
The MnCoZn-based ferrite is formed into a granulated powder having a particle size distribution d90 value of more than 150 μm and 300 μm or less--sintered body and / or formed into a granulated powder having a crushing strength of more than 1.10 MPa and less than 1.50 MPa. What is claimed is: 1. A MnCoZn-based ferrite characterized by comprising

6. A calcining step of calcining a mixture of basic components and a mixing-pulverizing step of adding subcomponents to the calcined powder obtained in the calcining step, mixing, and crushing;
A granulating step of adding a binder to the pulverized powder obtained in the above-mentioned mixing-pulverizing step, mixing, and then granulating it;
After forming the granulated powder obtained in the granulation step, firing is performed at 1290 ° C. or higher for 1 hour or longer to obtain the MnCoZn-based ferrite according to 1 or 2 above. Ferrite manufacturing method.

7. 7. The method for producing an MnCoZn ferrite according to 6, wherein the granulation is a spray drying method.

8. 8. The method for producing an MnCoZn-based ferrite as described in 6 or 7 above, wherein a value of a particle size distribution d90 of the granulated powder is more than 150 μm and 300 μm or less.

9. The method for producing an MnCoZn ferrite according to any one of 6 to 8, wherein the granulated powder has a crushing strength of more than 1.10 MPa and less than 1.50 MPa.

According to the present invention, not only having good magnetic properties of high resistance and low coercivity, but also generating uniform grain boundaries and at the same time suppressing abnormal grain growth, it is mechanically excellent in defect resistance. It is possible to obtain MnCoZn ferrite having strength.
The MnCoZn ferrite of the present invention has excellent magnetic properties such that the initial permeability at 100 ° C. and 1 kHz is 3000 or more, the initial permeability at 100 ° C. and 1 MHz is 2000 or more, and the initial permeability at 100 ° C. and 10 MHz is 150 or more. .
In addition, since the MnCoZn ferrite of the present invention has a high initial permeability μi at 100 ° C. and a low coercive force, the influence of heat generation due to noise filters and power conversion used in a high temperature environment such as in-vehicle, for example. It is particularly suitable for use in receiving transformers and the like.

Hereinafter, the present invention will be specifically described.
First, the reason why the composition of the MnCoZn ferrite is limited to the above range in the present invention will be described. In addition, about iron, zinc, cobalt, and manganese contained in the present invention as basic components, all values are represented by values converted to Fe ₂ O ₃ , ZnO, CoO, and MnO. The contents of Fe ₂ O ₃ , ZnO, CoO, and MnO are expressed in mol%, and the contents of one subcomponent and the impurity component are expressed in mass ppm with respect to the entire ferrite.

Fe ₂ O ₃ : 45.0 mol% or more and less than 50.0 mol% When Fe ₂ O ₃ is excessively contained, the amount of Fe ²⁺ increases, thereby reducing the specific resistance of MnCoZn ferrite. In order to avoid this, the amount of Fe ₂ O ₃ needs to be suppressed to less than 50 mol%. However, if the amount is too small, the coercivity is increased and the Curie temperature is decreased, so that iron is contained at least 45.0 mol% in terms of Fe ₂ O ₃ . A preferable range of Fe ₂ O ₃ is 47.1 mol% or more and less than 50.0 mol%, and most preferably 47.1 to 49.5 mol%.

ZnO: 3.0 mol% or more and less than 15.5 mol% ZnO increases the saturation magnetization of ferrite, and also has a relatively low saturation vapor pressure, thereby increasing the sintering density and increasing the saturation magnetic flux density. It is an effective component for lowering the coercivity. Therefore, at least 3.0 mol% of zinc is contained in terms of ZnO as a minimum. On the other hand, when the zinc content is larger than the appropriate value, the Curie temperature is lowered and there is a problem in practical use. Therefore, the upper limit of zinc is less than 15.5 mol% in terms of ZnO. A preferable range of ZnO is 5.0 to 15.3 mol%, more preferably 7.0 to 15.0 mol%, and most preferably 7.0 to 14.0 mol%.

CoO: 0.5 mol% to 4.0 mol%
Co ²⁺ in CoO is an ion having a positive magnetic anisotropy energy, and as a result of the addition of an appropriate amount of CoO, the absolute value of the sum of the magnetic anisotropy energy decreases, so that the coercive force is reduced. The For that purpose, it is essential to add 0.5 mol% or more of CoO. On the other hand, when a large amount is added, the specific resistance is lowered, abnormal grain growth is induced, and the sum of magnetic anisotropy energy is excessively positively inclined. In order to prevent this, CoO is limited to the addition of up to 4.0 mol%. The range of preferred CoO is more than 0.7 mol%, 4.0 mol% or less, more preferably more than 0.9 mol%, 4.0 mol% or less, further preferably 1.0 to 3.5 mol%, most preferably 1.0. It is -3.0 mol%.

MnO: balance The present invention is MnCoZn ferrite, and the balance of the basic component composition needs to be MnO. The reason is that unless MnO is used, good magnetic properties such as high saturation magnetic flux density, low loss, and high magnetic permeability cannot be obtained. A preferable range of MnO is 33.5 to 42.0 mol%, more preferably 34.0 to 42.0 mol%, and most preferably 34.0 to 40.0 mol%.

The basic components have been described above, but the subcomponents are as follows.
SiO _2: 50~300massppm
SiO ₂ is known to contribute to homogenizing the crystal structure of ferrite, and with the addition of an appropriate amount, the voids remaining in the crystal grains are reduced, and the coercive force is lowered by lowering the residual magnetic flux density. Let Further, since SiO ₂ segregates at the grain boundary to increase the specific resistance and at the same time to reduce the crystals having a coarse grain size, the Rattler value, which is an index of defects in the sintered body, can be reduced. Therefore, at least 50 mass ppm of SiO ₂ is included. On the other hand, abnormal grain appeared in the opposite in the case of the addition amount excessive, which contains increases and Ratora value to become a starting point of the defect, since the initial permeability is decreased and increased coercivity simultaneously, the SiO ₂ Should be limited to 300 mass ppm or less. A more preferred content of SiO ₂ is in the range of 60 to 250 mass ppm.

CaO: 300-1300 massppm
CaO segregates at the crystal grain boundary of MnCoZn ferrite, has a function of suppressing the growth of crystal grains, and also has a role of reducing vacancies remaining in the crystal grains. Therefore, with the addition of an appropriate amount, the specific resistance is increased, the coercivity is also reduced, and the coarse crystals are reduced, so that the rattler value can also be reduced. Therefore, at least 300 mass ppm of CaO is included. On the other hand, when the addition amount is excessive, abnormal grains appear, the initial magnetic permeability is lowered, and the Rattler value and the coercive force are also increased. Therefore, it is necessary to limit the CaO content to 1300 massppm or less. A more preferred content of CaO is in the range of 350 to 1000 mass ppm, most preferably 350 to 990 mass ppm.

Next, the impurity component to be suppressed will be described.
Cd, Pb, Sb, As, Se, Bi, and Zr are each less than 20 massppm. Among these, Cd, Pb, Sb, As, and Se are contained in natural ores, or are mixed in during smelting. It is an ingredient inevitably contained in the inside. Bi and Zr are components that are conventionally added in order to obtain desired magnetic properties of MnZn ferrite. If these amounts are very small, there is no problem, but if they are contained in a certain amount or more, abnormal grain growth of the ferrite is induced, and the various properties of the obtained ferrite are seriously adversely affected. Ferrite having a composition containing less than 50 mol% of Fe ₂ O ₃ as in the present invention is more likely to proceed with crystal grain growth than that containing 50 mol% or more, so Cd, Pb, Sb, As, Se, When the amounts of Bi and Zr are large, abnormal grain growth is likely to occur. In this case, not only the coercive force is increased, but also the specific resistance is decreased due to insufficient generation of crystal grain boundaries, the initial permeability is decreased, and the Rattler value is also increased because it becomes a starting point of a defect.
Therefore, in the present invention, the contents of Cd, Pb, Sb, As, Se, Bi, and Zr are all suppressed to less than 20 massppm.

  Further, not only the composition but also various characteristics of MnCoZn ferrite are greatly influenced by various parameters. Therefore, in the present invention, it is preferable to satisfy the following conditions in order to have desired magnetic characteristics and strength characteristics. Preferably, the Cd content is 15 massppm or less, the Pb, Sb, and As contents are all 7 massppm or less, the Se content is 15 massppm or less, and the Bi and Zr contents are all 10 massppm or less.

Sintered density: 4.85 g / cm ³ or more In the MnCoZn ferrite, sintering and grain growth proceed by firing treatment to form crystal grains and grain boundaries. Crystal structure capable of realizing low coercivity, that is, nonmagnetic components to be present at grain boundaries are appropriately segregated at grain boundaries, and grains are composed of components having a suitable grain size and uniform magnetism In order to achieve the desired form, the sintering reaction needs to proceed sufficiently. In addition, from the viewpoint of preventing defects, when the sintering is insufficient, the strength is unfavorably reduced.
From the above viewpoints, the MnCoZn ferrite of the present invention preferably has a sintered density of 4.85 g / cm ³ or more. By satisfying this, the coercivity can be reduced, and the Latler value can be suppressed to be low. In addition, in order to realize this sintering density, it is necessary to make the maximum holding temperature at the time of baking 1290 ° C. or more, and to hold the holding time at this temperature for 1 h or more. Preferably, the maximum holding temperature is 1290-1400 ° C. and the holding time is 1-8 hours. In addition, when abnormal grain growth occurs, the sintered density does not increase. Therefore, it is necessary to make the additive amount and impurity amount described above within an appropriate range so that abnormal grains do not appear.

-It is produced using granulated powder having a particle size distribution d90 value of 300 μm or less.
-It produces using granulated powder whose granulated powder crushing strength is less than 1.50 MPa (preferably 1.30 MPa or less).
In general, MnCoZn ferrite is obtained by filling a granulated powder in a mold and then performing a powder molding step of compressing at a pressure of about 100 MPa, and firing and sintering the obtained molded body. On the surface of this ferrite, minute irregularities due to the gaps between the granulated powders remain even after sintering, and this becomes a starting point of defect for impact, and the Rattler value increases as the remaining minute irregularities increase. Therefore, in order to reduce the gap between the granulated powders, it is preferable to remove the granulated powder having a coarse particle size and to suppress the crushing strength of the granulated powder to a certain value or less.
As an effective means for satisfying this condition, it is effective to adjust the particle size by passing the obtained granulated powder through a sieve. On the other hand, in order to reduce the crushing strength of the granulated powder, it is effective to prevent the temperature from becoming excessively high when granulating by applying heat as in the spray granulation method. The particle size distribution is measured by particle size analysis by laser diffraction / scattering method described in JIS Z 8825. "D90" represents a particle size of 90% of the total volume from the small particle size side in the particle size distribution curve. Further, the crushing strength of the granulated powder is measured by the method defined in JIS Z 8841.

If the value of the particle size distribution d90 is too small, the fluidity decreases due to an increase in the contact point between the granulated powders, so that there is a problem in filling the powder mold during powder molding and an increase in molding pressure during molding. The lower limit of d90 is 150 μm. The preferred particle size distribution d90 is in the range of 180 to 290 μm, more preferably 200 to 280 μm.
If the granulated powder crushing strength is greatly reduced, the granulated powder will be crushed during transportation and powder filling, and the fluidity will be reduced. Since the problem of an increase in the molding pressure occurs, the lower limit of the crushing strength is set to exceed 1.10 MPa. The preferred crush strength range is 1.12 MPa or more and less than 1.50 MPa, more preferably 1.15 to 1.40 MPa, and most preferably 1.15 to 1.30 MPa.

Next, the method for producing the MnCoZn ferrite of the present invention will be described.
Regarding the production of MnCoZn ferrite, first, Fe ₂ O ₃ , ZnO, CoO and MnO powder are weighed so as to have a predetermined ratio, and after sufficiently mixing these, calcination is performed. Next, the calcined powder obtained is pulverized. Here, the subcomponents defined in the present invention are added at a predetermined ratio, and combined with the calcined powder and pulverized. In this step, the powder is sufficiently homogenized so that the concentration of the added component is not uneven, and at the same time, the calcined powder is refined to the target average particle size.
Regarding the above steps, it is important to use high-purity raw materials with a small amount of impurities, and to thoroughly wash before mixing, grinding media, etc. in order to prevent mixing of components contained in other materials. is there.
Subsequently, an organic substance binder such as polyvinyl alcohol is added to the powder having the target composition, and granulated powder by granulation such as spray drying under appropriate conditions so as to obtain a sample having the desired particle size and crushing strength as described above. And In the case of the spray drying method, it is desirable that the exhaust air temperature be lower than 270 ° C., more preferably 260 ° C. or lower. 200 degreeC is preferable and, as for the lower limit of exhaust air temperature, 210 degreeC is more preferable. Next, after passing through steps such as sieving for particle size adjustment as necessary, pressure is applied by a molding machine, and then molding is performed under suitable baking conditions. In addition, it is desirable to remove the coarse powder on a sieve through the sieve of 350 micrometers of openings.
The appropriate firing conditions are, as described above, the maximum holding temperature: 1290 ° C. or more, and the holding time: 1 h or more.
The obtained ferrite sintered body may be subjected to processing such as surface polishing.

Thus, previously impossible,
・ To obtain MnCoZn ferrite that satisfies all of the excellent characteristics of Rattler value less than 0.85%, coercive force at 100 ° C. of 15 A / m or less, specific resistance of 30 Ω · m or more, and Curie temperature of 170 ° C. or more. it can.

Example 1
Iron contained, zinc, all cobalt and manganese _Fe 2 _O 3, ZnO, when calculated as CoO and _MnO, Fe ₂ O 3, ZnO, CoO, and MnO content was weighed so that the ratio shown in Table 1 Each raw material powder was mixed using a ball mill for 16 hours, and then calcined at 925 ° C. for 3 hours in air. Next, to this calcined powder, SiO ₂ and CaO were weighed after being respectively equivalent to 150 and 700 mass ppm, and then added, and ground in a ball mill for 12 hours. Next, polyvinyl alcohol is added to the obtained pulverized slurry, spray dry granulation is performed at an exhaust air temperature of 250 ° C., coarse powder is removed through a sieve having an opening of 350 μm, and then a pressure of 118 MPa is applied to apply a toroidal core and a rectangular parallelepiped core. Molded into. In addition, since a high purity raw material was used and the medium such as a ball mill was sufficiently washed before use to suppress mixing of components from other materials, impurities Cd, Pb, Sb, As and Se contained in the toroidal core and the rectangular parallelepiped core were used. Were all 3 mass ppm, and the Bi and Zr components were 5 mass ppm. The particle size distribution d90 of the granulated powder used for molding was 230 μm, and the crushing strength was 1.29 MPa. The contents of Cd, Pb, Sb, As, Se, Bi and Zr were quantified according to JIS K 0102 (IPC mass spectrometry).
Thereafter, the compact was placed in a firing furnace and fired at a maximum temperature of 1350 ° C. for 2 hours in a gas flow in which nitrogen gas and air were appropriately mixed. Outer diameter: 25 mm, inner diameter: 15 mm, height: 5 mm And a sintered cylindrical columnar core having a diameter of 10 mm and a height of 10 mm.

The obtained sample was measured based on JIS C 2560-2, the sintered density was 23 ° C., the toroidal core was measured by the Archimedes method, and the specific resistance was measured by the four-terminal method. The initial permeability of the toroidal core was calculated based on the inductance measured at 100 ° C. using an LCR meter (Keysight Corp. 4980A) after winding the toroidal core with 10 turns. In addition, the Curie temperature was calculated from the temperature characteristic measurement result of the inductance. The Rattler value was measured according to the method defined in JPMA P11-1992. The coercive force Hc was measured at 100 ° C. based on JIS C 2560-2.
The obtained results are also shown in Table 1. The coercivity at 23 ° C. and the initial permeability at 23 ° C. were measured for some samples.

As shown in the table, in Examples 1-1 to 1-9, which are invention examples, the high strength of the Rattler value is less than 0.85%, and the specific resistance at 23 ° C. is 30 Ω · m or more and the retention at 100 ° C. An MnCoZn ferrite having excellent magnetic properties of a magnetic force of 15 A / m or less and a Curie temperature of 180 ° C. or more could be obtained.
On the other hand, in Comparative Examples 1-1 and 1-2 containing 50.0 mol% or more of Fe ₂ O ₃ , the specific resistance is greatly reduced with the generation of Fe ²⁺ . On the other hand, in Comparative Example 1-3 in which the amount of Fe ₂ O ₃ is less than 45.0 mol%, an increase in coercive force and a decrease in Curie temperature are observed.
Moreover, in the comparative example 1-4 whose ZnO amount exceeds an appropriate range, the fall of Curie temperature is seen. On the other hand, in Comparative Example 1-5 in which the amount of ZnO is less than the appropriate range, the coercive force is increased, and preferable magnetic characteristics are not realized.
Furthermore, in Comparative Example 1-6 in which the amount of CoO does not reach the appropriate range, the coercivity is high due to the lack of positive magnetic anisotropy, while in the comparative example 1-7 in which the amount of CoO exceeds the appropriate range, excessive positive The coercivity is increased due to the increase of the magnetic anisotropy, and both deviate from the preferable range.
Furthermore, in Comparative Examples 1-8 and 1-9 in which the ZnO amount exceeded the appropriate range, a satisfactory Curie temperature was not obtained.

Example 2
When all of iron, zinc, cobalt and manganese contained are converted as Fe ₂ O ₃ , ZnO, CoO and MnO, the amount of Fe ₂ O ₃ is 49.0 mol%, the amount of ZnO is 10.0 mol%, and the amount of CoO is 2 The raw materials were weighed so as to have a composition of 0 mol% and the balance MnO, mixed for 16 hours using a ball mill, and then calcined in air at 925 ° C. for 3 hours. Next, SiO ₂ and CaO in amounts shown in Table 2 were added to the calcined powder, and grinding was performed for 12 hours with a ball mill. Next, polyvinyl alcohol is added to the obtained pulverized slurry, spray dry granulation is performed at an exhaust air temperature of 250 ° C., coarse powder is removed through a sieve having an opening of 350 μm, and then a pressure of 118 MPa is applied to apply a toroidal core and a cylindrical core. Molded into. Impurities Cd, Pb, Sb, As and Se contained in the toroidal core and the cylindrical core were all 3 massppm, and Zr and Bi were 5 massppm. In addition, the particle size distribution d90 of the granulated powder used for shaping | molding was 230 micrometers, and crushing strength was 1.29 MPa.
Thereafter, the compact was placed in a firing furnace and fired at a maximum temperature of 1350 ° C. for 2 hours in a gas flow in which nitrogen gas and air were appropriately mixed. Outer diameter: 25 mm, inner diameter: 15 mm, height: 5 mm The sintered body toroidal core of the above and the cylindrical-shaped core of five diameter: 10 mm and height: 10 mm were obtained.
About each of these samples, each characteristic was evaluated using the same method and apparatus as Example 1. FIG.
The obtained results are also shown in Table 2.

As shown in the table, in Examples 2-1 to 2-4 in which the amount of SiO _{2 and the} amount of CaO are within the appropriate range, the high strength that the rattler value is less than 0.85%, and the specific resistance at 23 ° C. is 30 Ω. A MnCoZn ferrite having excellent magnetic properties such as a coercive force at m to 100 ° C. of 15 A / m or less and a Curie temperature of 180 ° C. or more could be obtained.
On the other hand, in Comparative Examples 2-1 and 2-3 in which even one of SiO ₂ and CaO does not reach the appropriate range, the size of the crystal grains is uniform because the generation of the grain boundaries is insufficient. Therefore, the specific value is less than 30 Ω · m because the Rattler value is higher than 0.85% and the grain boundary thickness is insufficient.
Further, in the Comparative Examples 2-2, 2-4, and 2-5 levels where one or more of the same components are excessive, abnormal particles appear and sintering is inhibited, so the sintering density is low. Latler is also high. In addition, since the generation of crystal grain boundaries is insufficient, the specific resistance is low, the initial permeability is lowered, and the coercive force is also increased.

Example 3
According to the methods shown in Examples 1 and 2, the ratio of the basic component and the subcomponent is the same as that in Example 1-2, while raw materials having different amounts of impurities are used, or intentionally By adding the components, a sintered toroidal core having an outer diameter of 25 mm, an inner diameter of 15 mm, and a height of 5 mm, and a cylindrical core having five diameters of 10 mm and a height of 10 mm were produced. The results of evaluating the characteristics using the same method and apparatus are shown in Table 3. In addition, the particle size distribution d90 of the granulated powder used for shaping | molding was 230 micrometers, and crushing strength was 1.29 MPa.

As shown in the table, Example 3-1 in which the content of Cd, Pb, Sb, As, Se, Bi and Zr is not more than the specified value is the strength represented by the Rattler value, and the coercive force at 100 ° C. Good values are obtained for all of the magnetic characteristics represented by the specific resistance and the Curie temperature.
On the other hand, abnormal particles appear in all of Comparative Examples 3-1 to 3-9 in which one or more of these seven levels exceed the specified value, and sintering is inhibited. Since the sintered density is low, the Rattler value is high, and since the generation of crystal grain boundaries is insufficient, the specific resistance is low and the coercive force is also high.

Example 4
By using the methods shown in Examples 1 and 2, molded bodies produced at such a ratio that the basic component, the subcomponent and the impurity component have the same composition as Example 1-2 were subjected to various temperature conditions shown in Table 4. And fired. In addition, the particle size distribution d90 of the granulated powder used for shaping | molding was 230 micrometers, and crushing strength was 1.29 MPa.
About each of these samples, each characteristic was evaluated using the same method and apparatus as Example 1. The obtained results are also shown in Table 4.

As shown in the table, Examples 3-1 to 3-3 having a maximum holding temperature of 1290 ° C. or more and a holding time of 1 hour or more and a sintering density of 4.85 g / cm ³ or more. In No. 5, the strength represented by the Rattler value, the specific resistance, the coercive force at 100 ° C., and the magnetic properties represented by the Curie temperature were good.
On the other hand, in Comparative Examples 3-1 to 3-6, where the sintering temperature is less than 1290 ° C., or the holding time is less than 1 hour, and the sintering density is less than 4.85 g / cm ³ , the sintering density is low. Therefore, the Latler value is high, and the crystal grain growth is insufficient. As a result, the hysteresis loss is increased. As a result, the coercivity is high, which is not preferable in terms of both strength and magnetic characteristics.

Example 5
Using the granulated powder (crush strength: 1.29 MPa) obtained under the same composition and spray dry conditions as in Example 1-2 according to the method shown in Examples 1 and 2, changing the screening conditions A toroidal core and a cylindrical core were molded by applying a pressure of 118 MPa to the particle size distribution d90 shown in Table 5. Thereafter, the compact was placed in a firing furnace and fired at a maximum temperature of 1350 ° C. for 2 hours in a gas flow in which nitrogen gas and air were appropriately mixed. Outer diameter: 25 mm, inner diameter: 15 mm, height: 5 mm The sintered body toroidal core of the above and the cylindrical-shaped core of five diameter: 10 mm and height: 10 mm were obtained.
The characteristics of each of these samples were evaluated using the same method and apparatus as in Example 1. The obtained results are also shown in Table 5.

As shown in the table, in Example 5-1 in which the granulated powder particle size distribution d90 has a value of 300 μm or less, there are few remaining voids between the granulated powders, and there are few origins of defects, so the Rattler value is 0.85. It can be suppressed to less than%.
On the other hand, in Comparative Examples 5-1 to 5-3 in which the value of d90 is larger than 300 μm, there are many voids between the granulated powders and there are many origins of defects, so the rattler value is high and the strength is lowered.

Example 6
Granules having different crush strengths are obtained by spray-drying a slurry prepared by the method shown in Examples 1 and 2 and having the same composition as Example 1-2 under the exhaust air temperature conditions shown in Table 6. After removing the coarse powder through a sieve having an opening of 350 μm, a pressure of 118 MPa was applied to form a toroidal core and a cylindrical core. The particle size distribution d90 of the granulated powder at this time was 230 μm.
Thereafter, the compact was placed in a firing furnace and fired at a maximum temperature of 1350 ° C. for 2 hours in a gas flow in which nitrogen gas and air were appropriately mixed. Outer diameter: 25 mm, inner diameter: 15 mm, height: 5 mm The sintered body toroidal core of the above and the cylindrical-shaped core of five diameter: 10 mm and height: 10 mm were obtained.
The results of evaluating the properties of each of these samples using the same method and apparatus as in Example 1 are also shown in Table 6.

As shown in the table, in Examples 1-2 and 6-1 in which the exhaust air temperature of the spray dry granulation is not excessively high, the crushing strength of the granulated powder is less than 1.5 MPa, and the granulated powder Since it crushes sufficiently, there is no gap between the granulated powder, and hence there are few origins of defects, so the rattler value can be suppressed to less than 0.85%.
On the other hand, when attention is paid to Comparative Examples 6-1 to 6-3 in which the exhaust air temperature is excessively high and the granulated powder crushing strength is 1.5 MPa or more, there are many origins of defects due to defective granulated powder crushing. Since the Latler value is high, the strength is decreasing.

Claims (9)

A MnCoZn ferrite comprising a basic component, an accessory component and an unavoidable impurity, wherein
As the basic component,
Iron: 45.0 mol% or more, less than 50.0 mol%, in terms of Fe ₂ O ₃ ,
Zinc: 3.0 mol% or more and less than 15.5 mol% in terms of ZnO,
Cobalt: 0.5 to 4.0 mol% in terms of CoO and manganese: the balance,
With respect to the above basic component, as the above subcomponent,
SiO _2: 50~300massppm and CaO: 300~1300massppm
Including
Cd in the inevitable impurities, Pb, Sb, As, S e Contact and Zr content, respectively less than 20Massppm, the Bi amount is suppressed below 5Massppm,
Furthermore, in the above-mentioned MnCoZn ferrite,
Rattler value is less than 0.85%,
The coercivity at 100 ° C is 15A / m or less,
Resistivity of 30 Ω · m or more,
Curie temperature is 170 ° C or higher,
Initial permeability of 3000 or more at 100 ° C, 1kHz,
An MnCoZn ferrite characterized in that the initial permeability at 100 ° C. and 1 MHz is 2000 or more and the initial permeability at 100 ° C. and 10 MHz is 150 or more. The MnCoZn ferrite according to claim 1, wherein a sintering density of the MnCoZn ferrite is 4.85 g / cm ³ or more.   The MnCoZn-based ferrite according to claim 1 or 2, wherein the MnCoZn-based ferrite is a MnCoZn-based ferrite comprising a granulated powder-sintered body having a particle size distribution d90 value of more than 150 µm and 300 µm or less. .   4. The MnCoZn-based ferrite is a MnCoZn-based ferrite made of a granulated powder-sintered body having a crushing strength of more than 1.10 MPa and less than 1.50 MPa. 5. MnCoZn ferrite. A MnCoZn-based ferrite composed of a basic component, subcomponents and inevitable impurities,
As the basic component,
Iron: 45.0 mol% or more, less than 50.0 mol%, in terms of Fe ₂ O ₃ ,
Zinc: 3.0 mol% or more and less than 15.5 mol% in terms of ZnO,
Cobalt: 0.5 to 4.0 mol% in terms of CoO and manganese: the balance,
With respect to the above basic component, as the above subcomponent,
SiO _2: 50~300massppm and CaO: 300~1300massppm
Including
Cd in the inevitable impurities, Pb, Sb, As, S e Contact and Zr content, respectively less than 20Massppm, the Bi amount is suppressed below 5Massppm,
Furthermore, in the above-mentioned MnCoZn ferrite,
Rattler value is less than 0.85%,
The coercivity at 100 ° C is 15A / m or less,
A resistivity of 30 Ω · m or more and a Curie temperature of 170 ° C. or more ,
The MnCoZn-based ferrite is formed into a granulated powder having a particle size distribution d90 value of more than 150 μm and 300 μm or less--sintered body and / or formed into a granulated powder having a crushing strength of more than 1.10 MPa and less than 1.50 MPa. What is claimed is: 1. A MnCoZn-based ferrite characterized by comprising A calcining step of calcining a mixture of basic components; a mixing-grinding step of adding and mixing and crushing subcomponents to the calcined powder obtained in the calcining step;
A granulating step of adding a binder to the pulverized powder obtained in the above-mentioned mixing-pulverizing step, mixing, and then granulating it;
3. After forming the granulated powder obtained in the granulation step, it is fired at 1290 ° C. or more for 1 hour or longer to obtain the MnCoZn-based ferrite according to claim 1 or 2, MnCoZn Method of producing ferrite.   The method for producing MnCoZn ferrite according to claim 6, wherein the granulation is a spray drying method.   The method for producing a MnCoZn-based ferrite according to claim 6 or 7, wherein a value of a particle size distribution d90 of the granulated powder is more than 150 µm and 300 µm or less. The crushing strength of the said granulated powder is more than 1.10 MPa and less than 1.50 MPa, The manufacturing method of the MnCoZn type ferrite in any one of the Claims 6-8 characterized by the above-mentioned.