JP6439086B1 - MnCoZn-based ferrite and method for producing the same - Google Patents

Abstract

As basic components, iron: 45.0 mol% or more in terms of Fe2O3 and less than 50.0 mol%, zinc: 15.5 to 24.0 mol% in terms of ZnO, cobalt: 0.5 to 4.0 mol% in terms of CoO, and manganese Including MnCoZn-based ferrite composed of inevitable impurities, the remainder being SiO2: 50 to 300 massppm and CaO: 300 to 1300 massppm as subcomponents with respect to the basic component, and P in the above inevitable impurities , B, S, and Cl are respectively suppressed to P: less than 50 massppm, B: less than 20 massppm, S: less than 30 massppm, and Cl: less than 50 massppm. Further, the Rattler value is less than 0.85%, and the squareness ratio at 23 ° C is 0. .35 or less, specific resistance of 30 Ω · m or more and By the Curie temperature and 100 ° C. or higher, a high resistance, but also have good magnetic properties of low squareness ratio, it provides MnCoZn ferrite bring together excellent mechanical strength.

Description

The present invention relates to a MnCoZn-based ferrite having a high specific resistance, a small squareness ratio that is a ratio of residual magnetic flux density to saturated magnetic flux density (residual magnetic flux density / saturated magnetic flux density), and a method of manufacturing the same.
In the present specification, the squareness ratio is a value at 23 ° C.

A typical example of the soft magnetic oxide magnetic material is MnZn ferrite. The conventional MnZn ferrite contains about 2 mass% or more of Fe ²⁺ having positive magnetic anisotropy, and cancels out with Fe ³⁺ and Mn ²⁺ having negative magnetic anisotropy. We have achieved the permeability rate and low loss.
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 Ni has a larger negative magnetic anisotropy energy than Mn and contains almost no Fe ²⁺ having a positive magnetic anisotropy, so that the squareness ratio is increased. The squareness ratio is a value obtained by dividing the residual magnetic flux density by the saturation magnetic flux density. If this value is large, the initial permeability is greatly reduced and a loss is increased at the same time after a magnetic field is once applied from the outside. . Therefore, the characteristics as a soft magnetic material are greatly impaired.

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 squareness ratio has not been solved at all.

Therefore, the technique of adding Co ²⁺ having positive magnetic anisotropy other than Fe ²⁺ was disclosed in Patent Document 4, Patent Document 5 and Patent Document 6, which are aimed at lowering the squareness ratio. It was not a thing. Moreover, since measures against abnormal grains described later are insufficient, the cost and production efficiency are also inferior.

On the other hand, Patent Document 7 reports a high-resistance MnCoZn ferrite having a low squareness ratio that suppresses the appearance of abnormal grains by providing a definition in the impurity composition, enables stable production.
The abnormal grain growth is a phenomenon that occurs when the balance of grain growth is locally lost for some reason, and is a phenomenon often observed during production using the powder metallurgy method. In this abnormally grown grain, substances that greatly disturb the movement of the domain wall such as impurities and lattice defects are mixed, so that the residual magnetic flux density is increased, and as a result, the squareness ratio is increased. At the same time, the specific resistance decreases because the formation of grain boundaries becomes insufficient.

Japanese Patent Laid-Open No. 7-230909 JP 2000-277316 A JP 2001-220222 A Japanese Patent No. 341827 JP 2001-220221 A JP 2001-68325 A Japanese Patent No. 4508626 JP 2006-44971 A

With the development of the aforementioned Patent Document 7, MnCoZn ferrite that is satisfactory in terms of magnetic properties can be obtained.
On the other hand, in recent years, there has been a remarkable movement in the electrification of automobiles, and the number of cases where MnCoZn ferrite is also installed in automobiles is increasing. However, the mechanical strength is an important characteristic 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 is getting to be.

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. Tends 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, while the technique disclosed in Patent Document 7 has sufficient magnetic properties, it has left a problem in that it is not always sufficient with respect to the mechanical strength against this defect.

As a technique for improving the chipping strength, Patent Document 8 discloses a technique of adding TiO ₂ in a range of 0.01 to 0.5 mass%.
However, the addition of TiO ₂ , on the other hand, forms a solid solution in the crystal grains to produce Ti ^4+, and a part of Fe ³⁺ is reduced to Fe ²⁺ from the valence balance, resulting in a significant decrease in specific resistance. There was a disadvantage.

  The present invention maintains the good magnetic properties of conventional high resistance and low squareness ratio, while generating uniform crystal grain boundaries and at the same time suppressing abnormal grain growth, thereby providing defect resistance represented by Rattler value. It aims at proposing the MnCoZn ferrite which has the mechanical strength called the property 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 was high, the squareness ratio was small, and the Curie temperature was low. We have found an appropriate range in which all of the high characteristics can be realized simultaneously.
In the present specification, as described above, the value at 23 ° C. is a problem for the squareness ratio. This is because some MnZn ferrite cores used in antenna and noise filter applications are used at positions away from power transformers and semiconductors that are heat sources, and these operate at room temperature (5-35 ° C). To do. Therefore, it is important that the magnetic characteristics at 23 ° C., which is a typical value in the normal temperature (5-35 ° C.) range, that is, the squareness ratio is small.

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 addition amount of SiO ₂ and CaO, which are segregating components, greatly affects the grain boundaries, and therefore, an appropriate amount range of these components was successfully determined. A low Rattler value can be maintained within this range.

Moreover, essential in order to having both the mechanical strength to the preferred magnetic characteristics and defects, the suppression of abnormal grain appearance as a result of abnormal grains was examined by focusing on making conditions for occurrence of the aforementioned SiO ₂ It has been found that abnormal particles appear when CaO is excessive and when components such as P, B, S and Cl, which are impurities derived from raw materials, are contained in a certain value 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 describe positive magnetic differences. Although the addition of Co ²⁺ having anisotropy has been described, there is no description regarding the squareness ratio, and there is no description regarding countermeasures against abnormal grains, so it is presumed that the mechanical strength is insufficient. In addition, with respect to Patent Document 7 referred to regarding a low squareness ratio, since the definition of additives is insufficient, a sufficient mechanical strength that can suppress defects cannot be expected. Furthermore, even in Patent Document 8 that mentions improvement in chipping strength, a significant decrease in specific resistance cannot be avoided.

The gist of the present invention is as follows.
1. As a basic ingredient,
Iron: _Fe 2 _{O 3} in terms of in 45.0Mol% or more and less than 50.0 mol%,
Zinc: 15.5 to 24.0 mol% in terms of ZnO,
Cobalt: 0.5 to 4.0 mol% in terms of CoO and manganese: including the balance,
As a subcomponent for the basic component,
SiO _2: 50~300massppm and CaO: 300~1300massppm
The balance is MnCoZn-based ferrite composed of inevitable impurities,
The amounts of P, B, S and Cl in the inevitable impurities are respectively
P: less than 50 massppm,
B: Less than 20 massppm
S: less than 30 massppm and Cl: less than 50 massppm,
Furthermore, in the MnCoZn ferrite,
Rattler value is less than 0.85%,
The squareness ratio at 23 ° C. is 0.35 or less,
A MnCoZn-based ferrite having a specific resistance of 30 Ω · m or more and a Curie temperature of 100 ° C. or more.

2. 2. The MnCoZn ferrite according to 1, wherein the MnCoZn ferrite has a sintered density of 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 of 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 made of a granulated powder molded and sintered body having a crushing strength of less than 1.50 MPa.

5. A calcining step of calcining a mixture of basic components weighed to have a predetermined component ratio and a calcined powder obtained in the calcining step, adding a subcomponent adjusted to a predetermined ratio, mixing, A mixing-grinding step to grind;
After adding and mixing a binder to the pulverized powder obtained in the mixing and pulverizing step, granulation is performed so that the granulated powder has a particle size distribution d90 of 300 μm or less and / or a crushing strength of less than 1.50 MPa. After the formed granulated powder is molded, it is fired under the conditions of maximum holding temperature: 1290 ° C. or higher and holding time: 1 hour or longer to obtain the MnCoZn ferrite according to 1 or 2 above, Manufacturing method.

6). 6. The method for producing MnCoZn ferrite according to 5 above, wherein the granulation is a spray drying method.

According to the present invention, not only has excellent magnetic properties such as high resistance and low squareness ratio, but also generates uniform crystal grain boundaries and at the same time suppresses abnormal grain growth, thereby providing excellent mechanical properties such as fracture resistance. MnCoZn ferrite having both strength can be obtained.
The MnCoZn ferrite of the present invention has excellent magnetic properties such that the initial permeability at 23 ° C. and 1 kHz is 3000 or more, the initial permeability at 23 ° C. and 1 MHz is 2000 or more, and the initial permeability at 23 ° C. and 10 MHz is 150 or more. .

Hereinafter, the present invention will be specifically described.
First, the reason why the composition of 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. Further, the content of these Fe ₂ O ₃ , ZnO, CoO, and MnO is mol%, while the contents of subcomponents and impurity components are expressed in mass ppm with respect to the entire ferrite.

Fe ₂ O ₃ : 45.0 mol% to less than 50.0 mol% When Fe ₂ O ₃ is excessively contained, the amount of Fe ²⁺ increases, thereby decreasing 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 squareness ratio is increased and the Curie temperature is decreased. Therefore, at least 45.0 mol% of iron in terms of Fe ₂ O ₃ is contained. A preferable range of Fe ₂ O ₃ is 47.1 mol% or more and less than 50.0 mol%, and more preferably 47.1 to 49.5 mol%.

ZnO: 15.5 mol% to 24.0 mol%
ZnO increases the saturation magnetization of ferrite and has a relatively low saturation vapor pressure, thereby increasing the sintering density and increasing the saturation magnetic flux density, and is an effective component for reducing the squareness ratio. Therefore, at least 15.5 mol% of zinc in terms of ZnO is included. On the other hand, when the zinc content is higher than the appropriate value, the Curie temperature is lowered, which causes a practical problem. Therefore, the upper limit of zinc is 24.0 mol% in terms of ZnO. The preferable range of ZnO is 15.5 to 23.0 mol%, more preferably 17.0 to 23.0 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, resulting in a reduction in squareness ratio. 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 resistivity decreases, abnormal grain growth is induced, and the sum of the magnetic anisotropy energy is excessively positively inclined. In order to prevent this, CoO is limited to a maximum addition of 4.0 mol%. The range of preferable CoO is 1.0 to 3.5 mol%, more preferably 1.0 to 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 26.5 to 32.0 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 the homogenization of the ferrite crystal structure, and with the addition of an appropriate amount, the voids remaining in the crystal grains are reduced and the residual magnetic flux density is lowered, thereby reducing the squareness ratio. 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. For this reason, at least 50 mass ppm of SiO ₂ is contained. On the other hand, when the addition amount is excessive, abnormal grains appear on the contrary, and this is the starting point of the defect, so the Rattler value increases and at the same time the squareness ratio also increases, so the SiO ₂ content is limited to 300 massppm or less. There is a need. The preferable content of SiO ₂ is 60 to 250 massppm.

CaO: 300-1300 massppm
CaO segregates at the crystal grain boundaries of MnCoZn ferrite and has a function of suppressing the growth of crystal grains. Therefore, with the addition of an appropriate amount, the specific resistance increases, the squareness ratio is lowered by reducing the residual magnetic flux density, and the Rattler value can also be reduced because coarse crystals are reduced. For this reason, at least 300 mass ppm of CaO is included. On the other hand, when the addition amount is excessive, abnormal grains appear and the Rattler value and the squareness ratio also increase. Therefore, it is necessary to limit the content of CaO to 1300 massppm or less. The preferable content of CaO is 350 to 1000 massppm.

Next, the impurity component to be suppressed will be described.
P: less than 50 massppm, B: less than 20 massppm, S: less than 30 massppm, and Cl: less than 50 massppm These are components inevitably contained in raw materials such as iron oxide. If these contents are very small, there is no problem, but if they are contained in a certain amount or more, abnormal grain growth of 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 prone to crystal grain growth than that containing 50 mol% or more, and therefore has a large amount of P, B, S and Cl. And abnormal grain growth is likely to occur. In that case, the squareness ratio increases as the residual magnetic flux density increases, and the generation of crystal grain boundaries becomes insufficient, so that the specific resistance decreases, and the Rattler value also increases because it becomes a starting point for defects.
Therefore, in the present invention, the contents of P, B, S, and Cl are suppressed to less than 50, 20, 30, and 50 mass ppm, respectively.
In addition, the allowable amount of inevitable impurities including P, B, S and Cl described above needs to be 70 mass ppm or less as a whole. Preferably, the tolerable amount of the inevitable impurities is 65 massppm or less.

  Therefore, it is preferable to suppress the mixing of impurities in the basic component and subcomponents used as raw materials as much as possible. The total amount of impurities in the basic component and subcomponents used as raw materials is preferably 70 massppm or less, more preferably 65 massppm or less including the above-described P, B, S and Cl.

  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.

Sintering density: 4.85 g / cm ³ or more In MnCoZn ferrite, sintering and grain growth proceed by the firing treatment, and crystal grains and crystal grain boundaries are formed. The crystal structure that can achieve high saturation magnetic flux density and low residual magnetic flux density, that is, nonmagnetic components that should exist at the grain boundaries are segregated appropriately at the grain boundaries, and the grains maintain an appropriate grain size and have uniform magnetic properties. In order to realize a form composed of components having sinter, the sintering reaction needs to proceed sufficiently. Also, from the viewpoint of preventing defects, if the sintering is insufficient, the strength decreases, which is not preferable.
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 squareness ratio can be reduced and the Rattler value can be suppressed low. In order to realize this sintered density, it is necessary to set the maximum holding temperature during firing to 1290 ° C. or more and to fire the holding time at this temperature for 1 hour or more. The maximum holding temperature is preferably 1290 to 1400 ° C., and the holding time is preferably 1 to 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 is produced using granulated powder having a granulated powder crushing strength of less than 1.50 MPa.
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 a laser diffraction / scattering method described in JIS Z 8825. “ D 90” represents a particle size of 90% cumulative volume from the small particle size side in the particle size distribution curve. Moreover, about the crushing strength of granulated powder, it measures by the method prescribed | regulated to JISZ8841.
If the value of the particle size distribution d90 is too small, fluidity decreases due to an increase in the contact points between the granulated powders. Since an increase problem arises, the lower limit of d90 is preferably 75 μm. In addition, if the granulated powder crushing strength is greatly reduced, the granulated powder will be crushed during transportation and filling the mold of the powder, and the fluidity will decrease. Since there is a problem of increase in molding pressure at the time, the lower limit of the crushing strength is preferably 0.50 MPa.

Next, the manufacturing method of the MnCoZn ferrite of this invention is demonstrated.
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 obtained calcined powder is pulverized to obtain a pulverized powder. At this time, the subcomponents defined in the present invention are added at a predetermined ratio, and pulverized together with the calcined powder. In this step, the powder is sufficiently homogenized so that the concentration of the added component is not biased, and at the same time, the calcined powder is refined to the target average particle size. Here, the average particle diameter of the target pulverized powder is 1.4 to 1.0 μm.
Next, an organic binder such as polyvinyl alcohol is added to the powder having the target composition, and a granulated powder is obtained by granulation by a spray drying method or the like under appropriate conditions so as to obtain a sample having a desired particle size and crushing strength. In the case of the spray drying method, it is desirable that the exhaust air temperature is lower than 270 ° C. Here, the suitable particle size of the granulated powder is 75 to 300 μm in terms of the particle size distribution d90. Moreover, the suitable crushing strength of the granulated powder is 0.50 MPa or more and less than 1.50 MPa.
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 the sieve through a sieve having an opening of 350 μm. Appropriate firing conditions are a maximum holding temperature of 1290 or more and a holding time of 1 hour or more.
Note that the obtained ferrite sintered body may be subjected to processing such as surface polishing.

Thus, previously impossible,
・ To obtain a MnCoZn ferrite that satisfies all of the excellent characteristics of a Rattler value of less than 0.85%, a squareness ratio at 23 ° C. of 0.35 or less, a specific resistance of 30 Ω · m or more, and a Curie temperature of 100 ° 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 for 16 hours using a ball mill and then calcined in air at 925 ° C. for 3 hours. Next, to this calcined powder, SiO ₂ and CaO were weighed in amounts corresponding to 150 and 700 mass ppm, respectively, and then added and pulverized with 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. The particle size distribution d90 of the granulated powder used for molding was 230 μm, and the 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 And a sintered cylindrical columnar core having a diameter of 10 mm and a height of 10 mm.
Since high-purity raw materials were used, the amounts of impurities P, B, S and Cl contained in the ferrite were all 5 mass ppm. The contents of P, B, S and Cl were quantified according to JIS K 0102 (IPC mass spectrometry).

The obtained sample was measured according to 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 4-terminal method. The initial permeability of the toroidal core was calculated based on the inductance measured by using an LCR meter (4980A manufactured by Keysight) with a 10-turn winding on the toroidal core. The Curie temperature was calculated from the measurement result of the temperature characteristic of the inductance. The Rattler value was measured according to the method defined in JPMA P11-1992. The squareness ratio was calculated by dividing the residual magnetic flux density Br measured at 23 ° C. based on JIS C 2560-2 by the saturation magnetic flux density Bs.
The obtained results are also shown in Table 1.

As shown in the table, in Examples 1-1 to 1-7, which are invention examples, the high strength of the Rattler value is less than 0.85%, the specific resistance at 23 ° C. is 30 Ω · m or more, and the squareness ratio is 0. It was possible to obtain a MnCoZn ferrite having excellent magnetic properties of .35 or less and a Curie temperature of 100 ° C. or more.
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 as Fe ²⁺ is produced. 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 the squareness ratio and a decrease in the Curie temperature are observed.
Moreover, in Comparative Example 1-4 where the ZnO amount exceeds the appropriate range, the Curie temperature is decreased. On the other hand, in Comparative Example 1-5 in which the amount of ZnO is less than the appropriate range, the squareness ratio is increased, and preferable magnetic characteristics are not realized.
Further, in Comparative Example 1-6, in which the amount of CoO is less than the appropriate range, the residual magnetic flux density is increased, so the squareness ratio is high. On the other hand, in Comparative Example 1-7, where the amount of CoO exceeds the appropriate range, the magnetic anisotropy is increased. For this reason, the squareness ratio increases, and both deviate from the preferred range.

Example 2
When all the contained iron, zinc, cobalt and manganese 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 21.0 mol%, and the amount of CoO is 2 The raw materials were weighed to have a composition of 0.0 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, the amounts of SiO ₂ and CaO shown in Table 2 were added to the calcined powder and pulverized 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. The particle size distribution d90 of the granulated powder used for molding was 230 μm, the crushing strength was 1.29 MPa, and the amounts of impurities P, B, S and Cl in the ferrite were all 5 mass ppm.
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 cylindrical core with 5 diameters: 10 mm and height: 10 mm.
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 appropriate ranges, the Rattler value is less than 0.85% and the specific resistance at 23 ° C. is 30Ω. MnCoZn ferrite having excellent magnetic properties of m or more, a squareness ratio of 0.35 or less, and a Curie temperature of 100 ° C. or more could be obtained.
On the other hand, in Comparative Examples 2-1 and 2-3 in which any one of SiO ₂ and CaO is less than the appropriate range, the crystal grain size is prepared because the generation of crystal 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.
Moreover, in Comparative Examples 2-2, 2-4, and 2-5, in which even one of the same components is excessive, abnormal grains have appeared, and sintering density is low because sintering is inhibited. Rattler value is also high. In addition, since the generation of crystal grain boundaries is insufficient, the specific resistance is low, and the squareness ratio is increased as the residual magnetic flux density is 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 of Example 1-2, while using a raw material having different amounts of impurities, the outer diameter is 25 mm. A sintered toroidal core having 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 prepared, and the characteristics were evaluated using the same method and apparatus as in Example 1. The results are shown in Table 3. The granulated powder used for molding had a particle size distribution d90 of 230 μm and a crushing strength of 1.29 MPa.

As shown in the table, Example 3-1, in which the contents of P, B, S, and Cl are not more than the specified values, is expressed in terms of strength represented by Rattler values, squareness ratio, specific resistance, and Curie temperature. Good values are obtained for all of the magnetic properties.
On the other hand, in Comparative Examples 3-1 to 3-6 in which one or more of these four levels exceed the specified value, abnormal grains appear and sintering is inhibited. Since the sintering density is low, the Rattler value is high, and the generation of crystal grain boundaries is insufficient, so that the specific resistance is low, and the squareness ratio increases as the residual magnetic flux density increases.

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.
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. The granulated powder used for molding had a particle size distribution d90 of 230 μm and a crushing strength of 1.29 MPa.

As shown in the table, Examples 3-1 to 3-3 have a maximum holding temperature during firing of 1290 ° C. or higher, a holding time of 1 hour or longer, and a sintered density of 4.85 g / cm ³ or higher. In No. 5, the strength represented by the Rattler value and the magnetic properties represented by the specific resistance, squareness ratio and Curie temperature were good.
In contrast, in Comparative Examples 3-1 to 3-6 in which the firing temperature is less than 1290 ° C. or the holding time is less than 1 hour and the sintered density is less than 4.85 g / cm ³ , the sintered density is low. Therefore, the Latler value is high and the crystal grain growth is insufficient, so that the hysteresis loss is increased. As a result of the increase in the residual magnetic flux density Br, the squareness ratio is increased, and both strength and magnetic properties are increased. It is not preferable from the viewpoint.

Example 5
By using the granulated powder obtained under the same composition and the same spray-drying conditions as in Example 1-2 by the method shown in Examples 1 and 2, the particle size distribution d90 shown in Table 5 by changing the sieving conditions A toroidal core and a cylindrical core were molded by applying a pressure of 118 MPa to the value of (crushing strength: 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 And a cylindrical core with 5 diameters: 10 mm and height: 10 mm.
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 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. % Or less.
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 reduced.

Example 6
Example 1-2 produced by the method shown in Examples 1 and 2 Slurry produced with the same composition was spray-dried under the exhaust air temperature conditions shown in Table 6 to obtain granulated powders having different crushing strengths. 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 And a cylindrical core with 5 diameters: 10 mm and height: 10 mm.
The results of evaluating the characteristics of each sample using the same method and apparatus as in Example 1 are also shown in Table 6.

As shown in the Table, in Examples 6-1 exhaust air temperature of the spray drying granulation is not excessively high, crushing strength of the granulated powder is less than 1.5 MPa, the granulated powder is sufficiently crushed it during molding Therefore, there is no gap between the granulated powders, and therefore there are few starting points 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. The Rattler value is higher and the strength is lower.

Claims (5)

A MnCoZn-based ferrite composed of a basic component, subcomponents and inevitable impurities,
As the basic component,
Iron: Fe ₂ O ₃ in terms of in 45.0Mol% or more and less than 50.0 mol%,
Zinc: 15.5 to 24.0 mol% in terms of ZnO,
Cobalt: 0.5 to 4.0 mol% in terms of CoO and
Manganese: balance
Including
As a subcomponent with respect to the basic component,
SiO ₂ : 50 to 300 massppm and
CaO: 300-1300 massppm
Including
The amounts of P, B, S and Cl in the inevitable impurities are respectively
P: less than 50 massppm,
B: Less than 20 massppm
S: less than 30 massppm and
Cl: less than 50 massppm
To suppress,
Furthermore, in the MnCoZn ferrite,
Rattler value is less than 0.85%,
The squareness ratio at 23 ° C. is 0.35 or less,
Specific resistance is 30 Ω · m or more and
Curie temperature is 100 ° C or higher
And
And the MnCoZn ferrites, molding of granulated powder value less 300μm particle size distribution d90 - ing a sintered body Mn CoZn ferrite. A MnCoZn-based ferrite composed of a basic component, subcomponents and inevitable impurities,
As the basic component,
Iron: Fe ₂ O ₃ in terms of in 45.0Mol% or more and less than 50.0 mol%,
Zinc: 15.5 to 24.0 mol% in terms of ZnO,
Cobalt: 0.5 to 4.0 mol% in terms of CoO and
Manganese: balance
Including
As a subcomponent with respect to the basic component,
SiO ₂ : 50 to 300 massppm and
CaO: 300-1300 massppm
Including
The amounts of P, B, S and Cl in the inevitable impurities are respectively
P: less than 50 massppm,
B: Less than 20 massppm
S: less than 30 massppm and
Cl: less than 50 massppm
To suppress,
Furthermore, in the MnCoZn ferrite,
Rattler value is less than 0.85%,
The squareness ratio at 23 ° C. is 0.35 or less,
Specific resistance is 30 Ω · m or more and
Curie temperature is 100 ° C or higher
And
And the MnCoZn ferrites, molding crushing strength of the granulated powder is less than 1.50MPa - ing a sintered body Mn CoZn ferrite. The sintered density of the MnCoZn ferrite is 4.85 g / cm. ^Three The MnCoZn-based ferrite according to claim 1 or 2, which is as described above. 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;
After adding and mixing a binder to the pulverized powder obtained in the mixing and pulverizing step, granulation is performed so that the granulated powder has a particle size distribution d90 of 300 μm or less and / or a crushing strength of less than 1.50 MPa. After forming the granulated powder, the maximum holding temperature: 1290 ° C. or higher and the holding time: 1 hour or longer are fired,
A MnCoZn-based ferrite composed of a basic component, subcomponents and inevitable impurities,
As the basic component,
Iron: Fe ₂ O ₃ in terms of in 45.0Mol% or more and less than 50.0 mol%,
Zinc: 15.5 to 24.0 mol% in terms of ZnO,
Cobalt: 0.5 to 4.0 mol% in terms of CoO and
Manganese: balance
Including
As a subcomponent with respect to the basic component,
SiO ₂ : 50 to 300 massppm and
CaO: 300-1300 massppm
Including
The amounts of P, B, S and Cl in the inevitable impurities are respectively
P: less than 50 massppm,
B: Less than 20 massppm
S: less than 30 massppm and
Cl: less than 50 massppm
To suppress,
Furthermore, in the MnCoZn ferrite,
Rattler value is less than 0.85%,
The squareness ratio at 23 ° C. is 0.35 or less,
Specific resistance is 30 Ω · m or more and
Curie temperature is 100 ° C or higher
The manufacturing method of the MnCoZn type ferrite which has a baking process to obtain the MnCoZn type ferrite which is . The method for producing MnCoZn ferrite according to claim 4 , wherein the granulation is a spray drying method.