CN110418776B - MnCoZn ferrite and method for producing same - Google Patents

Abstract

The present invention provides a MnCoZn ferrite which not only has good magnetic properties of high electrical resistance and low squareness ratio, but also has excellent mechanical strength. A MnCoZn-based ferrite composed of a basic component, an auxiliary component and inevitable impurities, and the basic component contains iron: 47.1 mol% or more and less than 50.0 mol% in terms of Fe ₂ O ₃ , zinc: ZnO 3.0 mol % or more and less than 15.5 mol %, cobalt: 0.5 to 4.0 mol % in terms of CoO, and manganese: the balance; with respect to the basic component, as the auxiliary component: SiO ₂ : 50 to 300 Mass ppm, and CaO: 300 to 1300 mass ppm; the amounts of P, B, S, Cl, Bi and Zr in the unavoidable impurities are respectively controlled at: P: less than 50 mass ppm; B: less than 20 mass ppm ppm; S: less than 30 mass ppm; Cl: less than 50 mass ppm; Bi: less than 20 mass ppm; and Zr: less than 20 mass ppm; , the resistivity is above 30Ω·m, and the Curie temperature is above 170°C.

Description

MnCoZn ferrite and method for producing same

Technical Field

The present invention relates to a MnCoZn-based ferrite which is suitable for use in applications such as noise filters for vehicles, has a high resistivity, has a small squareness ratio as a ratio of a residual magnetic flux density to a saturation magnetic flux density (residual magnetic flux density/saturation magnetic flux density) at 100 ℃, and is hard to break, and a method for producing the MnCoZn-based ferrite.

Background

As soft magnetic oxide magnetic materialsAs a representative example, MnZn ferrite can be cited. The conventional MnZn ferrite contains about 2 mass% or more of Fe having positive magnetic anisotropy²⁺Counteracting Fe with negative magnetic anisotropy³⁺、Mn²⁺Thereby realizing high initial permeability and low loss in the kHz region.

Such MnZn ferrite is inexpensive compared to amorphous metals and the like, and is widely used as a magnetic core of a noise filter, a transformer, or an antenna of a switching power supply or the like.

However, since MnZn ferrite has a large amount of Fe²⁺Therefore, Fe is liable to occur³⁺-Fe²⁺There is an electron exchange therebetween, and there is a disadvantage that the resistivity is as low as 0.1 Ω · m. Therefore, when the frequency range used becomes high, the loss due to eddy current flowing in ferrite rapidly increases, the initial permeability greatly decreases, and the loss also increases. Therefore, the durable frequency of MnZn ferrite is limited to about several hundred kHz, and NiZn ferrite is mainly used in the MHz level. The resistivity of the NiZn ferrite is 10⁵Since Ω · m or more is about 1 ten thousand times as large as MnZn ferrite and the eddy current loss is small, the high initial permeability and low loss characteristics are hardly lost even in a high frequency region.

However, NiZn ferrite has a significant problem. That is, Ni has more negative magnetic anisotropy energy than Mn and contains almost no Fe having positive magnetic anisotropy²⁺And thus the squareness ratio increases. The squareness ratio is a value obtained by dividing the residual magnetic flux density by the saturation magnetic flux density, and when the value is large, the initial permeability is greatly reduced and the loss is increased at the same time upon application of a magnetic field from the outside. Therefore, the properties as a soft magnetic material are significantly impaired.

In addition to the NiZn ferrite, as a method for obtaining ferrite having a large resistivity, there is a method of reducing Fe contained in MnZn ferrite by²⁺To increase the resistivity.

For example, patent documents 1, 2, and 3 report that Fe is added₂O₃The component content is less than 50 mol% to reduce Fe²⁺MnZn ferrite in an amount to increase resistivity. However, since it is also like NiZn ironThe same as the matrix body is composed only of ions having negative magnetic anisotropy, so the problem of the rectangular ratio reduction is not solved at all.

Thus, patent documents 4, 5, and 6 disclose addition of Fe²⁺Co having positive magnetic anisotropy other than²⁺But these techniques are not intended to reduce the squareness ratio. Further, since the measures against abnormal particles described later are insufficient, the cost and the manufacturing efficiency are also poor.

In contrast, patent document 7 reports high-resistance MnCoZn ferrite that can be stably produced by controlling the occurrence of abnormal grains by planning the composition of impurities, and has a low squareness ratio.

In addition, abnormal grain growth occurs when the balance of local grain growth is broken for some reason, and is therefore a phenomenon often seen when manufacturing using a powder metallurgy method. In such abnormally grown grains, substances that greatly inhibit the movement of magnetic domain walls, such as impurities and lattice defects, are mixed, so that the soft magnetic properties are lost and the residual magnetic flux density is increased, with the result that the squareness ratio is improved. Meanwhile, the resistivity is lowered due to insufficient grain boundary formation.

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 7-230909

Patent document 2: japanese patent laid-open No. 2000-277316

Patent document 3: japanese patent laid-open No. 2001-220222

Patent document 4: japanese patent No. 3418827

Patent document 5: japanese patent laid-open No. 2001 and 220221

Patent document 6: japanese patent laid-open publication No. 2001 and 68325

Patent document 7: japanese patent No. 4508626

Disclosure of Invention

Problems to be solved by the invention

With the development of the above-mentioned patent document 7, MnCoZn ferrite satisfactory in magnetic characteristics at 23 ℃ has been obtained.

On the other hand, in recent years, electrification driving of automobiles is remarkable, and cases of mounting MnCoZn ferrite in automobiles are increasing, but mechanical strength is an important characteristic in the same use. In the vehicle-mounted application, since the automobile vibrates during running, it is also required that MnCoZn ferrite as a ceramic is not damaged by the impact of vibration, as compared with the electric products and industrial equipment mainly used so far.

However, Fe₂O₃Since MnCoZn ferrite having a composition of less than 50 mol% has a small number of oxygen vacancies and is easily sintered during firing, vacancies easily remain in crystal grains and the formation of grain boundaries is easily nonuniform. As a result, there is a problem that the ferrite is more easily damaged when an external impact is applied than the conventional MnCoZn ferrite.

In addition, since the vehicle-mounted application is susceptible to heat generation, it is required to maintain magnetic characteristics even at high temperatures. However, although patent document 7 mentions the magnetic properties at 23 ℃, it does not mention the magnetic properties at 100 ℃.

That is, the technique disclosed in patent document 7 has a sufficient magnetic characteristic at 23 ℃, but when an in-vehicle application is assumed, there is still a problem that the mechanical strength against damage and the magnetic characteristic at a high temperature of 100 ℃ are not necessarily sufficient.

The purpose of the present invention is to provide MnCoZn ferrite having both good magnetic properties of high electrical resistance at 23 ℃ and low squareness ratio at 100 ℃ by changing the selected composition, and mechanical strength of damage resistance indicated by a wear value (ラトラー value) by suppressing the growth of abnormal grains while forming a uniform grain boundary, and to provide an advantageous method for producing the MnCoZn ferrite.

Means for solving the problems

The present inventors first studied Fe of MnCoZn ferrite necessary for obtaining desired magnetic characteristics₂O₃Appropriate amounts of ZnO and CoO, and as a result, found that all of the characteristics of high resistivity, small squareness ratio at 100 ℃ and high Curie temperature can be simultaneously realizedAnd (3) a range.

Next, focusing on the microstructure, it was found that the damage of the sintered core expressed by the abrasion value can be suppressed by reducing the voids in the crystal grains, adjusting the crystal grain size, and realizing a crystal grain boundary of an appropriate thickness. Here, in order to achieve a desired crystal structure, it is based on the recognition that SiO, which is a component segregated at grain boundaries₂And the amount of CaO added have a great influence, and suitable ranges of these components have been successfully determined. If it is within this range, the abrasion value can be kept low.

Further, with respect to the suppression of the generation of abnormal particles which are indispensable for having both appropriate magnetic properties and mechanical strength against damage, attention is paid to production conditions at the time of generation of abnormal particles.

As a result, it was found that when the SiO was used₂And excessive CaO, or impurities derived from the raw materials or other trace additive components for MnZn ferrite are mixed due to insufficient cleaning in the production process, etc., and abnormal grains are generated when the P, B, S, Cl, Bi and Zr components are contained in a certain amount or more.

The present invention is based on the above findings.

Further, as described above, high resistivity is mentioned in patent document 1, patent document 2, patent document 3 and the like, and patent document 4, patent document 5 and patent document 6 state about addition of Co having positive magnetic anisotropy²⁺However, since there is no description about the squareness ratio and no description about measures against abnormal particles, it is assumed that the mechanical strength is also insufficient. Also, with patent document 7 which mentions a low squareness ratio, it is not expected to have sufficient mechanical strength capable of suppressing damage due to insufficient regulation of additives.

The main features of the present invention are as follows.

1. A MnCoZn-based ferrite composed of a basic component, an auxiliary component, and inevitable impurities, characterized in that:

the basic components comprise:

iron: with Fe₂O₃Is counted as 471 mol% 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%, based on CoO, and

manganese: the balance;

the auxiliary components include, as the essential components:

SiO₂: 50 to 300 mass ppm, and

CaO: 300 to 1300 mass ppm;

the amounts of P, B, S, Cl, Bi and Zr in the unavoidable impurities are controlled to be:

p: less than 50 mass ppm;

b: less than 20 mass ppm;

s: less than 30 mass ppm;

cl: less than 50 mass ppm;

bi: less than 20 mass ppm; and

zr: less than 20 mass ppm;

and, in the MnCoZn-based ferrite:

the abrasion value is less than 0.85 percent,

the squareness ratio at 100 ℃ is below 0.35,

a resistivity of 30 Ω · m or more, an

The Curie temperature is above 170 ℃.

2. The MnCoZn-based ferrite according to the above 1, wherein the MnCoZn-based ferrite is

Initial magnetic permeability of more than 3000 at 100 ℃ and 1kHz,

an initial permeability at 100 ℃ and 1MHz of 2000 or more, an

The initial permeability at 100 deg.C and 10MHz is above 150.

3. The MnCoZn-based ferrite according to the above 1 or 2, wherein a sintered density of the MnCoZn-based ferrite is 4.85g/cm³The above.

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

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

6. A method for producing MnCoZn ferrite, characterized by comprising the steps of:

a calcination step of calcining the mixture of the basic components, and

a mixing-pulverizing step of adding an auxiliary component to the calcined powder obtained in the calcining step, mixing and pulverizing the mixture, and

a granulating step of adding a binder to the pulverized powder obtained in the mixing-pulverizing step, mixing the powder, and granulating the mixture, and

a firing step of firing the granulated powder obtained in the granulating step at 1290 ℃ or higher for 1 hour or longer to obtain MnCoZn-based ferrite according to any one of the above-mentioned items 1 to 3.

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

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

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

Effects of the invention

According to the present invention, MnCoZn ferrite having excellent mechanical strength in which not only high electrical resistance and a low squareness ratio at 100 ℃ are excellent but also excellent breakdown resistance is achieved by forming uniform grain boundaries and suppressing abnormal grain growth.

The MnCoZn ferrite of the invention has excellent magnetic characteristics, and the initial permeability at 100 ℃ and 1kHz is more than 3000, the initial permeability at 100 ℃ and 1MHz is more than 2000, and the initial permeability at 100 ℃ and 10MHz is more than 150.

Further, since the MnCoZn ferrite of the present invention has a high initial permeability μ i at 100 ℃ and a low squareness ratio, it is particularly suitable for applications such as a noise filter used in a high-temperature environment such as an in-vehicle system and a transformer affected by heat generation associated with power conversion.

Detailed Description

The present invention will be specifically described below.

First, the reason why the composition of MnCoZn ferrite is limited to the above range in the present invention will be described. In addition, iron, zinc, cobalt, and manganese contained as essential components in the present invention are all converted to Fe₂O₃Values of ZnO, CoO, and MnO. And, these Fe₂O₃The contents of ZnO, CoO and MnO are expressed in mol%, and the contents of the auxiliary component and the impurity component are expressed in mass ppm with respect to the entire ferrite.

Fe₂O₃: 47.1 mol% or more and less than 50.0 mol%

Containing an excess of Fe₂O₃Of (i) Fe²⁺The amount increases, and thus the resistivity of MnCoZn ferrite decreases. To avoid this problem, Fe must be added₂O₃The amount of the compound is controlled to less than 50 mol%. However, if the amount is too small, the squareness ratio increases and the Curie temperature decreases, so that Fe is limited to Fe₂O₃The content of the catalyst is 47.1 mol% at the lowest. Preferably Fe₂O₃In the range of 47.1 to 49.8 mol%, more preferably in the range of 47.1 to 49.5 mol%.

ZnO: 3.0 mol% or more and less than 15.5 mol%

ZnO functions to increase the saturation magnetization of ferrite, and to increase the sintered density and increase the saturation magnetic flux density due to its relatively low saturation vapor pressure, and is an effective component to reduce the squareness ratio. Therefore, the zinc is limited to a minimum content of 3.0 mol% in terms of ZnO. On the other hand, if the zinc content is higher than an appropriate value, a drop in the Curie temperature is caused, which presents a problem in practical use. Therefore, the upper limit of zinc in terms of ZnO is limited to less than 15.5 mol%. Preferably, the ZnO is in the range of 5.0 to 15.3 mol%, more preferably 7.0 to 15.0 mol%, most preferably 7.0 to 14.0 mol%.

And (3) CoO: 0.5 mol% to 4.0 mol%

Co in CoO²⁺Is an ion having positive magnetic anisotropy energy, and with the addition of an appropriate amount of this CoO, the absolute value of the sum of the magnetic anisotropy energies decreases, and as a result, a reduction in squareness ratio is achieved. Therefore, it is necessary to add 0.5 mol% or more of CoO. On the other hand, a large amount of addition causes a decrease in resistivity, induces abnormal grain growth, and conversely causes an increase in squareness ratio due to excessive positive tilt of the sum of magnetic anisotropy energies. To prevent this problem, the maximum addition amount of CoO is limited to 4.0 mol%. Preferably the range of CoO is greater than 0.7 mol% and less than 4.0 mol%, more preferably greater than 0.9 mol% and less than 4.0 mol%, most preferably 1.0 to 3.5 mol%.

MnO: balance of

The present invention is MnCoZn ferrite, and the balance of the basic component composition thereof needs to be MnO. The reason is that if not MnO, good magnetic characteristics of high saturation magnetic flux density, low loss and high permeability cannot be obtained. Preferably, the range of MnO is 33.5 to 43.0 mol%, more preferably 34.0 to 42.5 mol%, most preferably 34.0 to 42.0 mol%.

The basic components are described above, and the auxiliary components are described below.

SiO₂: 50 to 300 mass ppm

SiO is known₂Contributes to the homogenization of the crystal structure of ferrite, and reduces residual vacancies in the grains with a proper amount of addition, and lowers the squareness ratio by lowering the residual magnetic flux density. And, SiO₂Since crystals segregated at grain boundaries to increase the resistivity and at the same time reduce the coarse grain size, the wear value, which is an index of the damage to the sintered body, can be reduced. Therefore, it is limited to contain SiO at a minimum of 50 mass ppm₂. On the other hand, in the case of excessive addition, since the occurrence of abnormal particles (which is a starting point of damage) conversely increases the abrasion value, and at the same time, the initial permeability decreases and the squareness ratio also increases, it is necessary to add SiO to the steel sheet₂The content of (B) is limited to 300 mass ppm or less. SiO is preferred₂Is in the range of 60 to 250 mass ppm.

CaO: 300 to 1300 mass ppm

CaO segregates in the MnCoZn ferrite grain boundary and has an effect of inhibiting grain growth. Therefore, by adding an appropriate amount, the resistivity can be increased, the residual magnetic flux density can be reduced to reduce the squareness ratio, and the abrasion value can be reduced due to the reduction of coarse crystals. Therefore, the minimum content of CaO is limited to 300 mass ppm. On the other hand, in the case of excessive addition, since abnormal particles occur, the abrasion value increases, the initial permeability decreases, and the squareness ratio also increases, it is necessary to limit the CaO content to 1300 mass ppm or less. Preferably, the content of CaO is in the range of 350 to 1000 mass ppm, most preferably 350 to 990 mass ppm.

Next, impurity components to be controlled will be described.

P: less than 50 mass ppm, B: less than 20 mass ppm, S: less than 30 mass ppm, Cl: less than 50 mass ppm, Bi: less than 20 mass ppm, and Zr: less than 20 mass ppm

Of these, P, B, S and Cl are components inevitably contained in the raw material iron oxide. In addition, Bi and Zr are generally intentionally added components to obtain the magnetic characteristics required for MnZn ferrite. If these mixing amounts are very small, there is no problem, but if they are contained in an amount of more than a certain amount, abnormal grain growth of ferrite is caused, which has a serious adverse effect on various properties of the ferrite obtained. As in the present invention, it contains only Fe of less than 50 mol%₂O₃The ferrite of the composition (2) is more likely to undergo grain growth than those containing 50 mol% or more, and therefore if the amounts of P, B, S, Cl, Bi and Zr are large, abnormal grain growth is likely to occur. In this case, the squareness ratio at 100 ℃ is increased due to an increase in residual magnetic flux density, and the electrical resistivity is lowered due to insufficient grain boundary formation, the initial permeability is also lowered, and it becomes a starting point of damage to increase the abrasion value.

Therefore, in the present invention, the contents of P, B, S, Cl, Bi and Zr are controlled to less than 50, 20, 30, 50, 20 and 20 mass ppm, respectively. The content of P is preferably 30 mass ppm or less, the content of B is preferably 15 mass ppm or less, the content of S is preferably 15 mass ppm or less, the content of Cl is preferably 30 mass ppm or less, the content of Bi is preferably 10 mass ppm or less, and the content of Zr is preferably 10 mass ppm or less.

Further, various properties of the MnCoZn ferrite are greatly affected by various parameters, not limited to the composition. Therefore, in the present invention, in order to obtain desired magnetic properties and strength properties, the following conditions are preferably satisfied.

Sintered density: 4.85g/cm³The above

In MnCoZn ferrite, sintering and grain growth are performed by a sintering process to form grains and grain boundaries. In order to obtain an embodiment capable of realizing a crystal structure of a low squareness ratio in which a nonmagnetic component present at grain boundaries is properly segregated at the grain boundaries and the crystal grains are composed of a component having a suitable grain diameter and uniform magnetism, it is necessary to sufficiently perform a sintering reaction. In addition, from the viewpoint of preventing damage, it is not preferable because the strength is lowered when sintering is insufficient.

From the above viewpoint, MnCoZn ferrite of the present invention preferably has 4.85g/cm³The above sintered density. By satisfying this, the squareness ratio can be reduced and the abrasion value can be controlled to be low. In order to achieve the sintered density, it is necessary to set the maximum holding temperature at firing to 1290 ℃ or higher and to perform firing at the holding temperature for 1 hour or longer. Preferably, the maximum holding temperature is 1290 to 1400 ℃ and the holding time is 1 to 8 hours.

Further, since the sintered density does not increase when abnormal grain growth occurs, it is necessary to manufacture the ceramic powder so that the amount of the additive and the amount of the impurity are within appropriate ranges so as not to cause abnormal grain growth.

The granulated powder having a particle size distribution d90 value of 300 μm or less was used for the production.

The granulated powder having a crushing strength of less than 1.50MPa (preferably 1.30MPa or less) is used for the production.

Generally, the MnCoZn ferrite is obtained by firing the obtained compact through a powder forming process in which granulated powder is filled in a die and then compressed under a pressure of about 100MPa to perform a powder forming process, and then sintering the same. Even after sintering, fine irregularities due to gaps between granulated powders remain on the surface of the ferrite, and this becomes a starting point of damage due to impact, so that the abrasion value increases with an increase in the remaining fine irregularities. 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 control 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 sieving the obtained granulated powder. On the other hand, in order to reduce the crushing strength of the granulated powder, when granulation is performed by applying heat as in the spray granulation method, it is effective to prevent the temperature from being excessively high. The particle size distribution was measured by particle size analysis by a laser diffraction/scattering method described in JIS Z8825. "d 90" represents a particle diameter at 90% of the volume accumulation from the small particle diameter side in the particle size distribution curve. The crushing strength of the granulated powder was measured by the method specified in JIS Z8841.

If the value of the particle size distribution d90 is too small, the fluidity is reduced due to an increase in the number of contact points between the granulated powders, and therefore, there arises a problem that the die filling of the powders fails at the time of powder molding and the molding pressure increases at the time of molding, and therefore, the lower limit of d90 is defined as 150 μm. The particle size distribution d90 preferably ranges from 180 to 290. mu.m, more preferably from 200 to 280. mu.m.

When the crushing strength of the granulated powder is greatly reduced, the granulated powder is crushed during transportation and at the time of mold filling of the powder, the flowability is reduced, and there are also problems of failure at the time of mold filling of the powder and increase in the molding pressure at the time of molding, so that the lower limit of the crushing strength is defined to be more than 1.10 MPa. The crushing strength is preferably in the range of 1.12MPa or more and less than 1.50MPa, more preferably 1.15 to 1.40MPa, most preferably 1.15 to 1.30 MPa.

Next, a method for producing MnCoZn ferrite of the present invention will be described.

For MnCoZn ferriteThe body is produced by first weighing Fe in a predetermined ratio₂O₃ZnO, CoO and MnO powders and they are thoroughly mixed and then calcined. The resulting calcined powder is then pulverized. At this time, the auxiliary components specified in the present invention are added at a predetermined ratio, mixed with the calcined powder, and pulverized. In this step, the calcined powder is refined to a target average particle size while homogenizing the powder sufficiently so that the concentrations of the components to be added do not vary.

In addition, it is important for the above process to use a high-purity raw material containing a small amount of impurities and to sufficiently clean the raw material before mixing, pulverizing a medium, and the like are used, in order to prevent components contained in other materials from being mixed.

Subsequently, an organic binder such as polyvinyl alcohol is added to the powder having the target composition, and a granulated powder is produced by granulation by a spray drying method or the like under appropriate conditions to obtain a sample having the desired particle size and crushing strength as described above. In the case of spray drying, it is desirable that the air discharge temperature is less than 270 ℃ and more preferably 260 ℃ or less. The lower limit of the discharge air temperature is preferably 200 deg.c, more preferably 210 deg.c. Then, the particle size is adjusted by a process such as sieving as necessary, and then the resultant is molded by applying pressure by a molding machine, and then fired under appropriate firing conditions. Further, it is desirable to pass through a sieve having a mesh size of 350 μm to remove coarse powder on the sieve.

The obtained ferrite sintered body may be subjected to a surface polishing treatment or the like.

In this way, MnCoZn ferrite, which has not been obtained in the past, can be obtained, which satisfies all of the following excellent properties at the same time:

an abrasion value of less than 0.85%,

a squareness ratio at 100 ℃ of 0.35 or less,

a resistivity of 30 Ω · m or more, an

Curie temperature is 170 ℃ or higher.

Examples

Example 1

The total content of Fe, Zn, Co and Mn is converted into Fe₂O₃In the case of ZnO, CoO and MnO, Fe was weighed in the proportions shown in Table 1₂O₃Amounts of ZnO, CoO and MnO, each raw material powder was mixed for 16 hours using a ball mill, and then calcined in air at 925 ℃ for 3 hours. Then, SiO equivalent to 150 and 700 ppm by mass equivalent was weighed respectively₂And CaO, it was added to the calcined powder and pulverized using a ball mill for 12 hours. Next, polyvinyl alcohol was added to the obtained pulverized slurry, spray-dried and granulated at a discharge temperature of 250 ℃, coarse powder was removed through a sieve having a mesh size of 350 μm, and then a pressure of 118MPa was applied to form a ring core and a rectangular core. Further, since a high-purity raw material was used and the medium such as a ball mill was thoroughly cleaned before use to reduce the mixing of components derived from other materials, the amounts of impurities P, B, S, Cl, Bi and Zr contained in the annular core and the rectangular core were each 5 mass ppm, the particle size distribution d90 of the granulated powder for molding was 230 μm, and the crushing strength was 1.29 MPa. In addition, the contents of P, B, S, Cl, Bi and Zr were determined according to JIS K0102 (IPC mass analysis).

Then, the molded body was charged into a firing furnace, and fired at a maximum temperature of 1350 ℃ for 2 hours in a gas flow in which nitrogen and air were properly mixed, to obtain an outer diameter: 25mm, inner diameter: 15mm, high: 5mm sintered body annular core and 5 diameters: 10mm, high: 10mm sintered cylindrical core.

The sintered density of the toroidal core was measured by the Archimedes method at 23 ℃ and the resistivity was measured by the 4-terminal method based on JIS C2560-2.

The initial permeability of the toroidal core was calculated from the inductance value measured at 100 ℃ by an LCR measuring instrument (4980A, manufactured by キーサイト) with 10 windings wound around the toroidal core. In addition, the initial permeability of some samples was also measured at 23 ℃.

The curie temperature was calculated from the result of measurement of the temperature characteristics of the inductance value.

For the abrasion value, the measurement was carried out in accordance with the method defined in JPMA P11-1992.

The squareness ratio was calculated by dividing the residual magnetic flux density Br measured at 100 ℃ based on JIS C2560-2 by the saturation magnetic flux density Bs. In addition, the squareness ratio of some samples was also determined at 23 ℃.

The results obtained are summarized in table 1.

[ Table 1]

As shown in the table, in examples 1-1 to 1-8 as examples of the present invention, MnCoZn ferrite having both high strength with a wear value of less than 0.85% and excellent magnetic properties of a resistivity of 30. omega. m or more at 23 ℃, a squareness ratio of 0.35 or less at 100 ℃ and a Curie temperature of 170 ℃ or more can be obtained.

On the other hand, the Fe content is 50.0 mol% or more₂O₃Comparative examples 1-1 and 1-2 in which Fe was accompanied²⁺The resulting resistivity of (2) is greatly reduced. On the other hand, in Fe₂O₃In comparative examples 1 to 3 in which the amount of (C) was less than 45.0 mol%, an increase in squareness ratio and a decrease in Curie temperature at 100 ℃ were observed.

In addition, in comparative examples 1 to 4 in which the amount of ZnO exceeded the appropriate range, a decrease in Curie temperature was observed. On the other hand, in comparative examples 1 to 5 in which the amount of ZnO did not reach the appropriate range, the squareness ratio increased, and good magnetic characteristics could not be achieved.

Further, in comparative examples 1 to 6 in which the amount of CoO did not reach the appropriate range, the squareness ratio was high due to insufficient positive magnetic anisotropy, while in comparative examples 1 to 7 in which the amount of CoO exceeded the appropriate range, an excessive increase in positive magnetic anisotropy caused an increase in squareness ratio and deviated from the preferred range.

Further, in comparative examples 1 to 8 in which the amount of ZnO exceeded the appropriate range, satisfactory Curie temperatures were not obtained.

Example 2

The total content of Fe, Zn, Co and Mn is converted into Fe₂O₃In the case of ZnO, CoO and MnO, as Fe₂O₃The composition of 49.0 mol%, ZnO 10.0 mol%, CoO 2.0 mol% and the balance MnO was measuredThe raw materials were mixed using a ball mill for 16 hours and then calcined in air at 925 ℃ for 3 hours. Then, SiO was added to the calcined powder in the amount shown in Table 2₂And CaO, and pulverized using a ball mill for 12 hours. Next, polyvinyl alcohol was added to the obtained pulverized slurry, spray-dried granulation was performed at a discharge temperature of 250 ℃, coarse powder was removed through a sieve having a mesh size of 350 μm, and then a pressure of 118MPa was applied to form a ring core and a cylindrical core. The contents of P, B, S, Cl, Bi and Zr in the toroidal core and the cylindrical core were all 5 mass ppm, and the granulated powder for molding had a particle size distribution d90 of 230 μm and a crushing strength of 1.29 MPa.

Then, the molded body was charged into a firing furnace, and fired at a maximum temperature of 1350 ℃ for 2 hours in a gas flow in which nitrogen and air were properly mixed, to obtain an outer diameter: 25mm, inner diameter: 15mm, high: 5mm sintered body annular core and 5 diameters: 10mm, high: a 10mm cylindrical core.

For these respective samples, the characteristics were evaluated by the same method and apparatus as in example 1.

The results obtained are summarized in table 2.

[ Table 2]

As shown in the table, in SiO₂In examples 2-1 to 2-4 in which the amount of CaO and the amount of CaO were within appropriate ranges, MnCoZn ferrite having both high strength with a wear value of less than 0.85% and excellent magnetic properties of a resistivity of 30. omega. m or more at 23 ℃ and a squareness ratio of 0.35 or less at 100 ℃ and a Curie temperature of 170 ℃ or more was obtained.

In contrast, among them, even SiO₂And comparative examples 2-1 and 2-3 in which CaO was not within the appropriate range, the abrasion value was higher than 0.85% because the grain boundary formation was insufficient and the size of the crystal grain was not uniform, and the resistivity was less than 30. omega. m because the grain boundary thickness was also insufficient.

In addition, in the level of comparative examples 2-2, 2-4 and 2-5 in which any one of the above components was excessive, abnormal particles appeared, which hindered sintering to lower the sintering density, and the abrasion value was also increased. Further, the resistivity is lowered due to insufficient formation of grain boundaries, the initial permeability is also lowered, and the squareness ratio is also increased.

Example 3

The outer diameters were produced by the methods described in examples 1 and 2, using the raw materials containing different amounts of impurities, or intentionally adding the components, in the same composition ratios as in examples 1 and 2, as the basic components and the auxiliary components: 25mm, inner diameter: 15mm, high: 5mm of sintered body annular core, and 5 diameters: 10mm, high: the characteristics of the 10mm cylindrical core were evaluated by the same method and apparatus as in example 1, and the obtained results are shown in Table 3. The granulated powder for molding had a particle size distribution d90 of 230 μm and a crushing strength of 1.29 MPa.

[ Table 3]

As shown in the table, in example 3-1 in which the contents of P, B, S, Cl, Bi and Zr were equal to or less than the predetermined values, the strength as expressed by the abrasion value and the magnetic properties as expressed by the squareness ratio at 100 ℃, the resistivity and the Curie temperature were all good.

In contrast, in each of comparative examples 3-1 to 3-8 in which one or more of the six content levels exceeded the prescribed value, abnormal particles appeared, the sintered density was reduced due to the inhibition of sintering, the abrasion value increased, and the electrical resistivity was reduced due to insufficient formation of grain boundaries, the initial permeability was also reduced, and the squareness ratio was also increased as the residual magnetic flux density was increased.

Example 4

According to the methods shown in examples 1 and 2, a molded body was produced from the basic components, the auxiliary components and the impurity components in the same composition ratios as in example 1-2, and the molded body was fired under various temperature conditions shown in Table 4. The granulated powder for molding had a particle size distribution d90 of 230 μm and a crushing strength of 1.29 MPa.

For these respective samples, the characteristics were evaluated by the same method and apparatus as in example 1. And the results obtained are summarized in table 4.

[ Table 4]

As shown in the table, the firing was carried out at a maximum holding temperature of 1290 ℃ or more and a holding time of 1 hour or more, and the sintered density was 4.85g/cm³In examples 4-1 to 4-5 above, the strength expressed by the abrasion value and the magnetic properties expressed by the specific resistance, the squareness ratio at 100 ℃ and the Curie temperature were all good.

On the other hand, when the firing temperature is less than 1290 ℃ or the holding time is less than 1 hour, the sintered density is less than 4.85g/cm³In comparative examples 4-1 to 4-3, the wear value was increased due to the low sintering density, the hysteresis loss was increased due to insufficient grain growth, and the residual magnetic flux density Br was increased, with the result that the squareness ratio was increased, which was not preferable from the viewpoint of both strength and magnetic characteristics.

Example 5

According to the methods shown in examples 1 and 2, granulated powders (crushing strength of 1.29MPa) obtained under the same spray drying conditions and the same composition as in examples 1 and 2 were used to obtain powders having the values of the particle size distribution d90 shown in Table 5 by changing the sieving conditions, and a pressure of 118MPa was applied to form a ring core and a cylindrical core. Then, the molded body was charged into a firing furnace, and fired at a maximum temperature of 1350 ℃ for 2 hours in a gas flow in which nitrogen and air were properly mixed, to obtain an outer diameter: 25mm, inner diameter: 15mm, high: 5mm sintered body annular core and 5 diameters: 10mm, high: a 10mm cylindrical core.

For these respective samples, the characteristics were evaluated by the same method and apparatus as in example 1. The results obtained are summarized in table 5.

[ Table 5]

As shown in the table, in example 5-1 in which the value of the particle size distribution d90 of the granulated powder was 300 μm or less, since the number of gaps between the granulated powders remained small and the starting points of breakage were reduced, the abrasion value could be controlled to 0.85% or less.

On the other hand, in comparative examples 5-1 to 5-3 in which the value of d90 was larger than 300. mu.m, the number of gaps between the granulated powders increased, and the number of starting points of breakage increased, so that the abrasion value increased and the strength decreased.

Example 6

Granulated powders having different crushing strengths were obtained by spray-drying slurries produced by the methods shown in examples 1 and 2 and having the same composition as in example 1-2 under the exhaust temperature conditions shown in table 6, coarse powders were removed from the granulated powders by passing them through a sieve having a mesh size of 350 μm, and then annular cores and cylindrical cores were formed by applying a pressure of 118 MPa. The particle size distribution d90 of the granulated powder at this time was 230. mu.m.

Then, the molded body was charged into a firing furnace, and fired at a maximum temperature of 1350 ℃ for 2 hours in a gas flow in which nitrogen and air were properly mixed, to obtain an outer diameter: 25mm, inner diameter: 15mm, high: 5mm sintered body annular core and 5 diameters: 10mm, high: a 10mm cylindrical core.

For these respective samples, the characteristics were evaluated by the same method and apparatus as in example 1. And the results obtained are summarized in table 6.

[ Table 6]

As shown in the table, in example 6-1 in which the air discharge temperature of the spray drying granulation was not excessively high, the crushing strength of the granulated powder was less than 1.5MPa, and since the granulated powder was sufficiently crushed at the time of molding and there was no gap between the granulated powders, the starting point of the breakage was reduced, so that the abrasion value could be controlled to less than 0.85%.

On the other hand, it is noted that in comparative examples 6-1 to 6-3 in which the discharge air temperature was too high and the crushing strength of the granulated powder was 1.5MPa or more, the abrasion value was increased and the strength was decreased because the starting points of breakage were increased due to the crushing failure of the granulated powder.

Claims (5)

1. a MnCoZn class ferrite, it is the MnCoZn class ferrite that is made up of basic component, auxiliary component and inevitable impurity, it is characterized in that: As the basic ingredients it contains: Iron: 47.1 mol% or more and less _than 50.0 mol% as _Fe2O3 , Zinc: 3.0 mol% or more and less than 15.5 mol% as ZnO, Cobalt: 0.5 to 4.0 mol% as CoO, and Manganese: balance; With respect to the basic ingredient, the auxiliary ingredient contains: SiO ₂ : 50 to 300 mass ppm, and CaO: 300 to 990 mass ppm; The amounts of P, B, S, Cl, Bi and Zr in the unavoidable impurities are respectively controlled at: P: less than 50 mass ppm; B: less than 20 mass ppm; S: less than 30 mass ppm; Cl: less than 50 mass ppm; Bi: less than 20 mass ppm; and Zr: less than 20 mass ppm; And, in the MnCoZn ferrite: The wear value is less than 0.85%, The squareness ratio at 100°C is below 0.35, The resistivity is above 30Ω·m, and Curie temperature above 170℃, The MnCoZn-based ferrite is composed of a shaped-sintered body of granulated powder having a particle size distribution d90 value of 230 μm or more and 300 μm or less, and the MnCoZn-based ferrite is composed of a crushing strength of more than 1.10 MPa and less than 1.50 MPa Formation of granulated powder - sintered body composition. 2. MnCoZn type ferrite according to claim 1, is characterized in that, described MnCoZn type ferrite: The initial permeability at 100°C and 1kHz is above 3000, Initial permeability above 2000 at 100°C, 1MHz, and The initial permeability at 100°C and 10MHz is above 150. 3. The MnCoZn-based ferrite according to claim 1 or 2, wherein the sintered density of the MnCoZn-based ferrite is 4.85 g/cm ³ or more. 4. A manufacturing method of MnCoZn-based ferrite, characterized in that it has the following steps: a calcination step of calcining the mixture of base ingredients, and A mixing-pulverizing process in which auxiliary components are added to the calcined powder obtained in the calcining process, and mixed and pulverized, and a granulation step of performing granulation after adding a binder to the pulverized powder obtained in the mixing-pulverizing step and mixing, and A firing step of obtaining the MnCoZn-based ferrite according to any one of claims 1 to 3 after molding the granulated powder obtained in the granulation step, and firing at 1290° C. or higher for 1 hour or longer. 5 . The method for producing MnCoZn-based ferrite according to claim 4 , wherein the granulation is a spray drying method. 6 .