TWI667220B - MnCoZn ferrite and manufacturing method thereof - Google Patents

Abstract

The present invention provides a MnCoZn ferrite which is a MnCoZn ferrite as a basic component and contains iron: 45.0 mol% or more and less than 50.0 mol% in terms of Fe ₂ O ₃ , and zinc: in terms of ZnO 15.5 mol% to 24.0 mol%, cobalt: 0.5 mol% to 4.0 mol% in terms of CoO, and manganese: the remainder, containing SiO ₂ : 50 mass ppm to 300 mass ppm as a subcomponent with respect to the basic component CaO: 300 mass ppm to 1300 mass ppm, and the remainder contains unavoidable impurities, and the amounts of P, B, S, and Cl in the unavoidable impurities are respectively suppressed to P: less than 50 mass ppm, B: less than 20 mass ppm, S: not 30massppm and Cl: less than 50massppm, further, the wear value is less than 0.85%, the square ratio at 23°C is set to 0.35 or less, and the specific resistance is set to 30Ω. m or more, and the Curie temperature is set to 100 ° C or more.

Description

MnCoZn ferrite and manufacturing method thereof

The present invention relates to a MnCoZn-based ferrite having a high specific resistance, a square ratio which is a ratio of a residual magnetic flux density to a saturation magnetic flux density (residual magnetic flux density/saturated magnetic flux density), and which is less likely to be defective, and a method for producing the same.

Further, in the present specification, the square ratio means a value at 23 °C.

A representative example of the soft magnetic oxide magnetic material is MnZn ferrite. The conventional MnZn ferrite contains about 2 mass% (mass%) or more of Fe ²⁺ having positive magnetic anisotropy, which is offset by Fe ³⁺ and Mn ²⁺ having negative magnetic anisotropy. A high initial permeability or low loss is achieved in the kHz region.

Since the MnZn ferrite is inexpensive compared with an amorphous metal or the like, it is widely used as a noise filter such as a switching power supply, a transformer, or a core of an antenna.

However, since MnZn ferrite has a large amount of Fe ²⁺ , it is easy to cause electron transfer between Fe ³⁺ -Fe ²⁺ and the specific resistance is as low as 0.1 Ω. The disadvantage of the m level. Therefore, if the frequency region to be used becomes high, the loss caused by the eddy current flowing in the ferrite body sharply increases, the initial permeability is greatly lowered, and the loss is also increased. Therefore, the limit of the durability frequency of the MnZn ferrite is about several hundred kHz, and NiZn ferrite is mainly used at the MHz level. The NiZn ferrite has a specific resistance of 10 ⁵ (Ω·m) or more, and is about 10,000 times that of the MnZn ferrite, and has a small eddy current loss. Therefore, even in a high frequency region, it is difficult to lose high initial permeability and low. Loss of this feature.

However, there are big problems in NiZn ferrite. It is that, compared with Mn, Ni has a large negative magnetic anisotropy energy and contains almost no Fe ²⁺ having positive magnetic anisotropy, so the square ratio becomes large. The square ratio is obtained by dividing the residual magnetic flux density by the saturation magnetic flux density. When the value is large, after the magnetic field is temporarily applied from the outside, the initial permeability is greatly lowered and the loss is increased. Therefore, the characteristics as a soft magnetic material are greatly impaired.

As a method of obtaining a ferrite having a larger specific resistance 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, in Patent Document 1, Patent Document 2, and Patent Document 3, there is reported a MnZn ferrite having improved specific resistance by setting the Fe ₂ O ₃ component to less than 50 mol% and reducing the Fe ²⁺ content. . However, like these NiZn ferrites, since only ions having negative magnetic anisotropy are contained, the problem of lowering the square ratio is not solved at all.

For this reason, Patent Document 4, Patent Document 5, and Patent Document 6 disclose a technique of adding Co ²⁺ having positive magnetic anisotropy other than Fe ²⁺ , but these do not have a purpose of reducing the square ratio. . In addition, countermeasures against abnormal particles described later are not sufficient, and therefore, they are also inferior in terms of cost and manufacturing efficiency.

On the other hand, Patent Document 7 reports that the provision of an impurity composition is set to suppress the occurrence of abnormal particles, stable manufacturing can be achieved, and the square ratio is low. High resistance MnCoZn ferrite.

Further, the abnormal particle growth is a phenomenon which occurs when the balance of particle growth locally collapses for some reason, and is a phenomenon often seen when manufacturing by the powder metallurgy method. A substance that greatly hinders the movement of the magnetic wall is contaminated with impurities or lattice defects in the abnormally grown particles. Therefore, the residual magnetic flux density increases, and as a result, the square ratio increases. At the same time, the grain boundary formation becomes insufficient, and thus the specific resistance is lowered.

[Prior Art Literature] [Patent Literature]

Patent Document 1: Japanese Patent Laid-Open No. Hei 7-230909

Patent Document 2: Japanese Patent Laid-Open Publication No. 2000-277316

Patent Document 3: Japanese Patent Laid-Open Publication No. 2001-220222

Patent Document 4: Japanese Patent No. 3418827

Patent Document 5: Japanese Patent Laid-Open Publication No. 2001-220221

Patent Document 6: Japanese Patent Laid-Open Publication No. 2001-68325

Patent Document 7: Japanese Patent No. 4508626

Patent Document 8: Japanese Patent Laid-Open No. 2006-44971

With the development of Patent Document 7, MnCoZn ferrite which satisfies magnetic properties is obtained.

On the other hand, in recent years, the trend of electrification of automobiles has become remarkable, and MnCoZn ferrites have been installed in automobiles, but they have received attention in this application. For mechanical strength. Compared with electrical equipment or industrial equipment that has been used as a main purpose so far, vibration occurs during traveling in automobiles. Therefore, in automotive applications, MnCoZn ferrite as ceramic is required to have no damage with respect to shock. By.

However, since the MnCoZn ferrite having a Fe ₂ O ₃ component of less than 50 mol% has a small amount of oxygen pores, it is easy to be sintered at the time of firing. Therefore, pores are likely to remain in the crystal grains, and formation of grain boundaries is likely to be uneven. As a result, when subjected to an impact from the outside, there is a problem that the defect is likely to occur as compared with the conventional MnCoZn ferrite.

That is, in the technique disclosed in Patent Document 7, the obtained magnetic characteristics are sufficient, and on the other hand, there is a problem that the mechanical strength against the defect is not sufficient.

Further, as a technique for improving the defect strength, Patent Document 8 discloses a technique of adding TiO ₂ in a range of 0.01 mass% to 0.5 mass%.

However, regarding the addition of TiO ₂ , on the other hand, since solid solution is dissolved in the crystal grains and Ti ^{4+ is formed} , and a part of Fe ³⁺ is reduced to Fe ²⁺ from the valence balance, the specific resistance is greatly lowered. The disadvantages.

The object of the present invention is to jointly propose a MnCoZn ferrite which maintains the good magnetic properties of the existing high resistance and low square ratio, and an advantageous manufacturing method thereof, and which generates uniform crystals by The boundary suppresses the growth of abnormal particles at the same time, and also has the mechanical strength of the defect resistance represented by the wear value.

The inventors first studied the reasonable amount of Fe ₂ O ₃ , ZnO, and CoO of MnCoZn ferrite required to obtain desired magnetic properties, and as a result, found that the specific resistance can be simultaneously achieved, and the square ratio is small. And a reasonable range of all the characteristics of high Curie temperature.

Further, in the present specification, as described above, the value at 23 ° C is a problem with respect to the square ratio. That is, in the MnZn ferrite core used in the use of an antenna or a noise filter, there are also many users who are away from the power transformer or semiconductor that is a heat source, and these are at normal temperature (5). Operate at °C~35°C). Therefore, it is important that the magnetic characteristics at 23 ° C which is a representative value in the range of normal temperature (5 ° C to 35 ° C) are good, that is, the square ratio is small.

Then, focusing on the fine structure, it was found that the defect of the sintered core represented by the wear value can be suppressed by reducing the voids in the crystal grains, adjusting the crystal grain size, and realizing a grain boundary of a moderate thickness. Here, in order to realize a desired crystal structure, since the amount of SiO ₂ and CaO added as a component segregated at the grain boundary has a large influence, the appropriate range of the components is successfully determined. If it is within this range, the low wear value can be maintained.

Further, in order to suppress the occurrence of abnormal particles in order to have better magnetic properties and mechanical strength against defects, attention has been paid to the production conditions at the time of occurrence of abnormal particles, and it has been found that the SiO is found. _{When the} amount of CaO is too large, and when a component such as P, B, S or Cl which is a source-derived impurity containing a certain value or more is contained, abnormal particles appear.

The present invention is based on the insights.

In addition, in the above-mentioned patent document 1, the patent document 2, the patent document 3, etc., about high specific resistance, it is mentioned, and patent document 4, patent document 5, and patent document 6 Although the addition of Co ²⁺ having positive magnetic anisotropy has been described, there is no description about the square ratio, and there is no description about the countermeasure against abnormal particles at all. Therefore, it is estimated that the mechanical strength is also insufficient. Further, in Patent Document 7 in which the low square ratio is mentioned, since the regulation of the additive is insufficient, sufficient mechanical strength capable of suppressing the defect cannot be expected. Further, even in Patent Document 8 which mentions an improvement in defect strength, a large reduction in specific resistance cannot be avoided.

The gist of the present invention is as follows.

1. A MnCoZn-based ferrite containing, as a basic component, iron: 45.0 mol% or more and less than 50.0 mol% in terms of Fe ₂ O ₃ and zinc: 15.5 mol% to 24.0 mol in terms of ZnO %, cobalt: 0.5 mol% to 4.0 mol% in terms of CoO and manganese: the remainder, as the subcomponent, includes SiO ₂ : 50 mass ppm to 300 mass ppm and CaO: 300 mass ppm to 1300 mass ppm, and The remaining portion contains unavoidable impurities, and the amounts of P, B, S, and Cl in the unavoidable impurities are respectively suppressed to P: less than 50 mass ppm, B: less than 20 mass ppm, S: less than 30 mass ppm, and Cl: less than 50 mass ppm, further, in the MnCoZn ferrite, the abrasion value is less than 0.85%, the square ratio at 23 ° C is 0.35 or less, and the specific resistance is 30 Ω. m or more, and the Curie temperature is 100 ° C or more.

2. The MnCoZn-based ferrite according to 1, wherein the MnCoZn-based ferrite has a sintered density of 4.85 g/cm ³ or more.

3. The MnCoZn-based ferrite according to the above-mentioned item 1 or 2, wherein the MnCoZn-based ferrite is a MnCoZn-based ferrite of a formed-sintered body containing a granulated powder having a particle size distribution d90 of 300 μm or less. body.

The MnCoZn-based ferrite according to any one of the above-mentioned, wherein the MnCoZn-based ferrite is a shaped-sintered MnCoZn containing a granulated powder having a crushing strength of less than 1.50 MPa. Ferrite.

A method for producing a MnCoZn-based ferrite, comprising: a pre-calcining step of pre-calcining a mixture of basic components weighed so as to have a predetermined component ratio; and a mixing-pulverizing step to the pre-calcining step To the obtained pre-calcined powder, an auxiliary component adjusted to a predetermined ratio is added, mixed and pulverized; and a calcination step, a binder is added to the pulverized powder obtained in the mixing-pulverizing step, and mixed, and then granulated The value of the particle size distribution d90 of the powder is 300 μm or less. And/or granulation is carried out so that the crushing strength is less than 1.50 MPa, and the obtained granulated powder is molded, and then calcined under the conditions of a maximum holding temperature: 1290 ° C or more and a holding time: 1 hour or more. The MnCoZn-based ferrite according to the above 1 or 2.

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

According to the present invention, the following MnCoZn ferrite can be obtained, which not only has good magnetic properties such as high electrical resistance and low square ratio, but also has excellent defect resistance by suppressing abnormal particle growth simultaneously with formation of uniform grain boundaries. This mechanical strength.

The MnCoZn ferrite of the present invention has excellent magnetic properties: an initial permeability of 3,000 or more at 23 ° C and 1 kHz, an initial permeability of 2,000 or more at 23 ° C and 1 MHz, and an initial permeability of 150 at 23 ° C and 10 MHz. the above.

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, iron, zinc, cobalt, and manganese which are contained in the present invention as a basic component are all expressed by values of Fe ₂ O ₃ , ZnO, CoO, and MnO. In addition, the content of the Fe ₂ O ₃ , ZnO, CoO, and MnO is expressed by mol%, and the content of the subcomponent and the impurity component is represented by 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⁺ is increased, whereby the specific resistance of the MnCoZn ferrite is lowered. In order to avoid this, it is necessary to suppress the amount of Fe ₂ O ₃ to less than 50 mol%. However, when the amount of Fe ₂ O ₃ is too small, the square ratio is increased and the Curie temperature is lowered. Therefore, it is required to contain at least 45.0 mol% of iron in terms of Fe ₂ O ₃ . The preferred range of Fe ₂ O ₃ is 47.1 mol% or more and less than 50.0 mol%, more preferably 47.1 mol% to 49.5 mol%.

ZnO: 15.5 mol% to 24.0 mol%

Since ZnO increases the saturation magnetization of the ferrite and has a relatively low saturated vapor pressure, it has a function of increasing the sintered density and increasing the saturation magnetic flux density, and is a component effective for reducing the square ratio. Therefore, it is assumed that at least 15.5 mol% of zinc is contained in terms of ZnO. On the other hand, in the case where the zinc content is more than a reasonable value, the Curie temperature is lowered, which is problematic in practical use. Therefore, the upper limit of zinc is set to 24.0 mol% in terms of ZnO. The range of ZnO is preferably 15.5 mol% to 23.0 mol%, more preferably 17.0 mol% to 23.0 mol%.

CoO: 0.5 mol% to 4.0 mol%

Co ^{2+ in} CoO is an ^ion having positive magnetic anisotropy energy, and with the addition of a reasonable amount of CoO, the absolute value of the sum of magnetic anisotropy energy is lowered, and as a result, the square ratio is lowered. Therefore, it is necessary to add 0.5 mol% or more of CoO. On the other hand, a large amount of addition causes a square ratio to rise due to a decrease in specific resistance, an initiation of abnormal particle growth, and an excessively large sum of magnetic anisotropy energy. In order to prevent this, it is assumed that CoO is stopped at a maximum of 4.0 mol%. A preferred range of CoO is from 1.0 mol% to 3.5 mol%, more preferably from 1.0 mol% to 3.0 mol%.

MnO: the remaining part

The present invention is a MnCoZn ferrite, and the remainder of the basic composition of the composition needs to be MnO. The reason for this is that if it is not MnO, good magnetic properties of high saturation magnetic flux density, low loss, and high magnetic permeability cannot be obtained. A preferred range of MnO is from 26.5 mol% to 32.0 mol%.

The basic components have been described above, and the subcomponents are as follows.

SiO ₂ : 50 mass ppm to 300 mass ppm

It is known that SiO ₂ contributes to the homogenization of the crystal structure of the ferrite, and the pores remaining in the crystal grains are reduced with an appropriate amount of addition, and the residual magnetic flux density is lowered, whereby the square ratio is lowered. Further, since SiO ₂ increases the specific resistance by segregation at the grain boundary and reduces the crystal of the coarse particle diameter, the wear value which is an index of the defect of the sintered body can be reduced. Therefore, it is assumed to contain at least 50 mass ppm of SiO ₂ . On the other hand, when the amount of addition is too large, abnormal particles appear instead, and this becomes a starting point of the defect. Therefore, the abrasion value increases and the square ratio also increases. Therefore, it is necessary to limit the content of SiO ₂ to 300 mass ppm or less. The preferred content of SiO ₂ is from 60 mass ppm to 250 mass ppm.

CaO: 300 mass ppm to 1300 mass ppm

CaO has a role of segregating at the grain boundary of MnCoZn ferrite and suppressing grain growth. Therefore, the specific resistance increases with an appropriate amount of addition, and the residual magnetic flux density is made. By this, the square ratio is also lowered, and the coarse crystals are reduced, so that the abrasion value can also be lowered. Therefore, it is set to contain at least 300 mass ppm of CaO. On the other hand, when the amount of addition is too large, abnormal particles appear, and the wear value and the square ratio also increase. Therefore, it is necessary to limit the content of CaO to 1300 mass ppm or less. The preferred content of CaO is from 350 mass ppm to 1000 mass ppm.

Next, the impurity component to be suppressed will be described.

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

These are components which are inevitably contained in raw materials such as iron oxide. If the content is extremely small, there is no problem. However, when a certain amount or more is contained, the abnormal particle growth of the ferrite is caused, and the characteristics of the obtained ferrite are seriously adversely affected. In the present invention, ferrite having a composition of only Fe ₂ O ₃ of less than 50 mol% is more likely to be crystallized than particles containing 50 mol% or more. Therefore, if the amounts of P, B, S, and Cl are large, Abnormal particle growth is prone to occur. In this case, the square ratio increases as the residual magnetic flux density increases, and the generation of grain boundaries becomes insufficient. Therefore, the specific resistance decreases and becomes a starting point of the defect, and thus the wear value also increases.

Therefore, in the present invention, the contents of P, B, S, and Cl are each suppressed to less than 50 mass ppm, less than 20 mass ppm, less than 30 mass ppm, and less than 50 mass ppm.

Further, it is necessary to set the total allowable amount of impurities including the P, B, S, and Cl to 70 mass ppm or less. It is preferable that the allowable amount of the unavoidable impurities is 65 mass ppm or less.

Therefore, it is preferable to suppress the incorporation of impurities in the basic component and the subcomponent used as the raw material as much as possible. The total amount of the impurities in the basic component and the subcomponent used as the raw material is preferably 70 mass ppm or less, more preferably 65 mass ppm or less, including the P, B, S, and Cl.

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

. Sintering density: 4.85g/cm ³ or more

The MnCoZn ferrite is sintered and subjected to particle growth by calcination treatment to form crystal grains and grain boundaries. In order to realize a crystal structure capable of realizing a high saturation magnetic flux density and a low residual magnetic flux density, that is, a form in which a non-magnetic component which is present at a grain boundary is appropriately segregated at a grain boundary, a crystal is required to be segregated. The granules contain ingredients that maintain a moderate particle size and have a uniform magnetic properties. Further, from the viewpoint of prevention of defects, when the sintering is insufficient, the strength is also lowered, which is not preferable.

From the above viewpoints, the sintered density of the MnCoZn ferrite of the present invention is preferably 4.85 g/cm ³ or more. By satisfying this condition, the square ratio is lowered, and the abrasion value can be suppressed low. Further, in order to achieve the sintered density, it is necessary to set the maximum holding temperature at the time of firing to 1,290 ° C or higher, and to perform calcination at a holding time at this temperature of 1 h or more. The maximum holding temperature is preferably from 1290 ° C to 1400 ° C, and the holding time is preferably from 1 hour to 8 hours. Further, in the case where abnormal particle growth has occurred, the sintered density is not improved. Therefore, it is necessary to control the amount of the additive or the amount of impurities described above to an appropriate range so that the abnormal particles do not occur.

. It is produced using a granulated powder having a particle size distribution d90 of 300 μm or less.

. The granulated powder having a crushing strength of less than 1.50 MPa was used for the production.

In general, the MnCoZn ferrite can be obtained by a powder forming step of compressing the granulated powder at a pressure of about 100 MPa after filling the mold, and the obtained shaped body is calcined and sintered. The minute irregularities caused by the gap between the granulated powders remain on the surface of the ferrite after sintering, and this is a starting point of the defect with respect to the impact. Therefore, the wear value changes as the residual of the fine unevenness increases. high. Therefore, in order to reduce the gap between the granulated powders, it is preferred to remove the granulated powder having a coarse particle size and also to suppress the crushing strength of the granulated powder to a certain value or less.

As means for satisfying the conditions, as for the particle size, 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 too high when granulation is performed by applying heat like spray granulation. Regarding the particle size distribution, laser diffraction is described by Japanese Industrial Standards (JIS) Z 8825. The particle size analysis by the scattering method was carried out. The "d90" indicates a particle diameter of 90% cumulative from the small particle size side in the particle size distribution curve. Further, the crushing strength of the granulated powder was measured by the method specified in JIS Z 8841.

In addition, if the value of the particle size distribution d90 is too small, the fluidity is lowered due to an increase in the contact point between the granulated powders, so that the mold filling failure of the powder during powder formation and the molding pressure at the time of molding increase occur. Problem, it is better to put under d90 The limit is set to 75 μm. In addition, if the crushing strength of the granulated powder is greatly lowered, the granulated powder is crushed at the time of conveyance and filling of the mold of the powder, and the fluidity is lowered, whereby the failure of the filling of the mold of the powder and the increase of the forming pressure at the time of molding still occur. Therefore, it is preferable to set the lower limit of the crushing strength to 0.50 MPa.

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

In the production of MnCoZn ferrite, first, Fe ₂ O ₃ powder, ZnO powder, CoO powder, and MnO powder are weighed so as to have a predetermined ratio, and these are sufficiently mixed and then pre-calcined. The obtained pre-calcined powder is then pulverized to obtain a pulverized powder. At this time, the subcomponents specified in the present invention are added at a predetermined ratio, and are pulverized together with the precalcined powder. In this step, the powder is sufficiently homogenized so that the concentration of the added component is not biased, and the pre-calcined powder is refined to a target average particle size. Here, the target pulverized powder has an average particle diameter of 1.4 μm to 1.0 μm.

Then, an organic binder such as polyvinyl alcohol is added to the powder having the target composition, and a sample having a desired particle size and crushing strength is obtained by granulation by a spray drying method or the like under appropriate conditions. Granulated into powder. In the case of the spray drying method, it is desirable to make the exhaust air temperature lower than 270 °C. Here, regarding the preferable particle size of the granulated powder, the value of the particle size distribution d90 is from 75 μm to 300 μm. Further, the preferred crushing strength of the granulated powder is 0.50 MPa or more and less than 1.50 MPa.

Then, after passing through a step such as sieving for particle size adjustment, after applying pressure in a molding machine and forming, calcination is carried out under appropriate calcination conditions. Furthermore, it is desirable to pass a granulated powder having a pore size of 350 μm in the sieve and to coarsely powder the sieve. Remove. Further, a reasonable calcination condition is that the maximum holding temperature is 1290 ° C or higher and the holding time is 1 hour or longer.

Further, the obtained ferrite sintered body may be subjected to surface polishing or the like.

In this way, it is possible to obtain both,

. Wear value less than 0.85%

. The square ratio at 23 ° C is 0.35 or less

. The specific resistance is 30Ω. m or more

. Curie temperature is above 100 °C,

All of the excellent properties of MnCoZn ferrite.

[Examples]

Example 1

When all the iron, zinc, cobalt, and manganese contained are converted into Fe ₂ O ₃ , ZnO, CoO, and MnO, the ratios of Fe ₂ O ₃ , ZnO, CoO, and MnO are shown in Table 1 using a ball mill. Each of the raw material powders weighed was mixed for 16 hours, and then pre-calcined in air at 925 ° C for 3 hours. Then, SiO ₂ and CaO in an amount of 150 mass ppm and 700 mass ppm were weighed and added to the pre-calcined powder, respectively, and pulverized by a ball mill for 12 hours. Then, polyvinyl alcohol was added to the obtained pulverized slurry, spray-dried and granulated at an exhaust air temperature of 250 ° C, and the coarse powder was removed by a sieve having a pore size of 350 μm, and then a pressure of 118 MPa was applied to form a toroidal core ( Toroidal core) and cuboid core. The granulated powder for forming had a particle size distribution d90 of 230 μm and a crush strength of 1.29 MPa.

Thereafter, the shaped body is placed in a calciner at a maximum temperature of 1,350 ° C, Calcined in a gas stream obtained by suitably mixing nitrogen gas with air for 2 hours to obtain a sintered body toroidal core having an outer diameter of 25 mm, an inner diameter of 15 mm, and a height of 5 mm, and five sintered cylindrical shapes having a diameter of 10 mm and a height of 10 mm. core.

Further, since a high-purity raw material was used, the amounts of impurities P, B, S, and Cl contained in the ferrite were all 5 mass ppm. Further, the contents of P, B, S and Cl were quantified in accordance with JIS K 0102 (Ion pair chromatography (IPC) mass spectrometry).

With respect to the obtained sample, the sintered density was measured for the toroidal core by the Archimedes method at 23 ° C based on JIS C 2560-2, and the specific resistance was measured by a four-terminal method. 10 turns of the winding on the toroidal core, and the initial measurement of the toroidal core is calculated according to the inductance measured by the inductance capacitance and resistance meter (LCR meter) (4980A manufactured by Keysight). Magnetic rate. Further, the Curie temperature is calculated based on the measurement result of the temperature characteristics of the inductor. The abrasion value was measured in accordance with the method specified in Japan Powder Metallurgy Association (JPMA) P11-1992. The square 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 collectively shown in Table 1.

As shown in Table 1, in Examples 1-1 to 1-7 which are examples of the invention, a high strength having an abrasion value of less than 0.85% and a specific resistance at 23 ° C of 30 Ω were obtained. MnCoZn ferrite having excellent magnetic properties of m or more and a square ratio of 0.35 or less and a Curie temperature of 100 ° C or more.

On the other hand, in Comparative Example 1-1 and Comparative Example 1-2 containing 50.0 mol% or more of Fe ₂ O ₃ , the specific resistance was greatly lowered with the formation of Fe ²⁺ . On the other hand, in Comparative Example 1-3 in which the amount of Fe ₂ O ₃ was less than 45.0 mol%, an increase in the square ratio and a decrease in the Curie temperature were observed.

Further, in Comparative Example 1-4 in which the amount of ZnO exceeded the reasonable range, a decrease in the Curie temperature was observed. On the other hand, in Comparative Examples 1-5 in which the amount of ZnO did not satisfy a reasonable range, the square ratio was increased, and preferable magnetic characteristics were not achieved.

Further, in Comparative Example 1-6 in which the amount of CoO did not satisfy a reasonable range, the residual magnetic flux density was increased, so the square ratio was high, and on the other hand, in Comparative Example 1-7 in which the amount of CoO exceeded the reasonable range, magnetic anisotropy was The increase and the square ratio also become higher and out of the preferred range.

Example 2

When all of the iron, zinc, cobalt, and manganese contained are converted into 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 becomes The raw material was weighed in a manner of 2.0 mol% and the remainder was made into a MnO composition, and after mixing for 16 hours using a ball mill, it was pre-calcined in air at 925 ° C for 3 hours. Then, SiO ₂ and CaO in the amounts shown in Table 2 were added to the pre-calcined powder, and pulverization was carried out for 12 hours by a ball mill. Then, polyvinyl alcohol was added to the obtained pulverized slurry, spray-dried and granulated at an exhaust air temperature of 250 ° C, and the coarse powder was removed by a sieve having a pore size of 350 μm, and then a pressure of 118 MPa was applied to form a toroidal core and Cylindrical core. Further, the granulated powder for forming had a particle size distribution d90 of 230 μm and a crush strength of 1.29 MPa, and the amounts of impurities P, B, S and Cl in the ferrite were both 5 mass ppm.

Thereafter, the formed body was placed in a calcining furnace, and calcined in a gas stream obtained by suitably mixing nitrogen gas and air at a maximum temperature of 1,350 ° C for 2 hours to obtain an outer diameter of 25 mm, an inner diameter of 15 mm, and a height of 5 mm. The sintered body toroidal core, and five cylindrical cores having a diameter of 10 mm and a height of 10 mm.

Each of the samples was evaluated for the respective characteristics by the same method and apparatus as in Example 1.

The obtained results are collectively shown in Table 2.

As shown in Table 2, in Examples 2-1 to 2-4 in which the amount of SiO _{2 and the} amount of CaO were within a reasonable range, high strength at a wear value of less than 0.85% and a high strength at 23 ° C were obtained. The specific resistance is 30Ω. MnCoZn ferrite having excellent magnetic properties of m or more and a square ratio of 0.35 or less and a Curie temperature of 100 ° C or more.

On the other hand, in Comparative Example 2-1 and Comparative Example 2-3 in which either of SiO ₂ and CaO did not satisfy a reasonable range, the generation of grain boundaries was insufficient, and thus the crystal grain size was not uniform, so the abrasion value was Above 0.85%, and the grain boundary thickness is not sufficient, so the specific electricity is prevented from less than 30Ω. m.

Further, in Comparative Example 2-2, Comparative Example 2-4, and Comparative Example 2-5 in which one of SiO ₂ and CaO was excessive, abnormal particles appeared, and sintering was inhibited, so that the sintered density was low and the abrasion value was high. . Further, since the generation of the grain boundary is insufficient, the specific resistance is low, and the square ratio is also increased as the residual magnetic flux density increases.

Example 3

By the method shown in Example 1 and Example 2, a sintered body toroidal core having an outer diameter of 25 mm, an inner diameter of 15 mm, and a height of 5 mm was produced using the following materials, and five cylinders having a diameter of 10 mm and a height of 10 mm were used. In the shape of the raw material, the ratio of the basic component and the subcomponent to the same composition as in Example 1-2 is the same, and the amount of impurities contained in the raw material is different, and the same as in the first embodiment is used. The method and apparatus were used to evaluate the characteristics, and the results obtained are shown in Table 3. Further, the granulated powder for forming had a particle size distribution d90 of 230 μm and a crush strength of 1.29 MPa.

As shown in Table 3, in Example 3-1 in which the contents of P, B, S, and Cl were not more than the predetermined value, the strength expressed by the abrasion value, and the square ratio, the specific resistance, and the Curie temperature were obtained. The magnetic properties indicated are all good values.

On the other hand, in Comparative Example 3-1 to Comparative Example 3-6 in which one or more of the four levels exceeded a predetermined value, abnormal particles appeared, and sintering was hindered, so that the sintered density was low, so the abrasion value was high. Further, since the formation of the grain boundary is insufficient, the specific resistance is low, and the square ratio is also increased as the residual magnetic flux density increases.

Example 4

Under the various temperature conditions shown in Table 4, the ratios of the basic composition, the subcomponent, and the impurity component in the same manner as in Example 1-2 were obtained by the methods shown in Example 1 and Example 2. The produced shaped body was calcined.

Each of the samples was evaluated for the respective characteristics by the same method and apparatus as in Example 1. The obtained results are collectively shown in Table 4. Further, the granulated powder for forming had a particle size distribution d90 of 230 μm and a crush strength of 1.29 MPa.

As shown in Table 4, Example 3-1 to Example 3 were carried out in which the maximum holding temperature at the time of firing was 1290 ° C or higher and the holding time was 1 hour or longer, and the sintered density was 4.85 g/cm ³ or more. In 5, the strength represented by the abrasion value and the magnetic characteristics represented by the specific resistance, the square ratio, and the Curie temperature were good.

On the other hand, in Comparative Example 3-1 to Comparative Example 3-6 in which the calcination temperature was less than 1290 ° C or the holding time was less than 1 hour and the sintered density was less than 4.85 g/cm ³ , since the sintered density was low, the abrasion was performed. When the value is high and the crystal grain growth is insufficient, the hysteresis loss increases and the residual magnetic flux density Br increases. As a result, the square ratio becomes high, which is not preferable from the viewpoint of both strength and magnetic properties.

Example 5

Using the method shown in Example 1 and Example 2, and the granulated powder obtained by the same composition and the same spray drying conditions as in Example 1-2, and changing the sieving conditions, Table 5 was used. The value of the particle size distribution d90 shown was applied to the granulated powder (crushing strength: 1.29 MPa) having the above value to form a toroidal core and a cylindrical core. Thereafter, the formed body was placed in a calcining furnace, and calcined in a gas stream obtained by suitably mixing nitrogen gas and air at a maximum temperature of 1,350 ° C for 2 hours to obtain an outer diameter of 25 mm, an inner diameter of 15 mm, and a height of 5 mm. The sintered body toroidal core, and five cylindrical cores having a diameter of 10 mm and a height of 10 mm.

Each of the samples was evaluated for the respective characteristics by the same method and apparatus as in Example 1. The obtained results are collectively shown in Table 5.

As shown in Table 5, in Example 5-1 in which the particle size distribution d90 of the granulated powder was 300 μm or less, the amount of voids between the granulated powders was small, and the starting point of the defects was small, so that the abrasion value was suppressed to 0.85. %the following.

On the other hand, in Comparative Example 5-1 to Comparative Example 5-3 in which the value of d90 was more than 300 μm, since there were many voids between the granulated powder and many starting points of the defect, the abrasion value was high and the strength was lowered.

Example 6

The slurry prepared by the method shown in Example 1 and Example 2, which was produced by the method shown in Example 1 and Example 2, was spray-dried under the exhaust air temperature conditions shown in Table 6, thereby obtaining a pressure. The granulated powder having different crushing strengths was passed through a sieve having a pore size of 350 μm to remove the coarse powder, and then a pressure of 118 MPa was applied to form a toroidal core and a cylindrical core. Further, the particle size distribution d90 of the granulated powder at this time was 230 μm.

Thereafter, the formed body was placed in a calcining furnace, and calcined in a gas stream obtained by suitably mixing nitrogen gas and air at a maximum temperature of 1,350 ° C for 2 hours to obtain an outer diameter of 25 mm, an inner diameter of 15 mm, and a height of 5 mm. The sintered body toroidal core, and five cylindrical cores having a diameter of 10 mm and a height of 10 mm.

Each of the samples was evaluated for the respective characteristics by the same method and apparatus as in Example 1. The obtained results are collectively shown in Table 6.

As shown in Table 6, in Example 6-1 in which the exhaust air temperature of the spray-drying granulation was not excessively high, the crushing strength of the granulated powder was less than 1.5 MPa, and the granulated powder was sufficiently destroyed at the time of molding, so that no residue remained. Since the gap between the granulated powders is small, the starting point of the defects is small, so that the abrasion value can be suppressed to less than 0.85%.

On the other hand, in the case of Comparative Example 6-1 to Comparative Example 6-3 in which the exhaust gas temperature is too high and the granulated powder crushing strength is 1.5 MPa or more, the starting point of the defect caused by the granulated powder destruction failure is large. Therefore, the wear value becomes high and the strength is lowered.

Claims (7)

A MnCoZn-based ferrite containing, as a basic component, iron: 47.1 mol% or more and less than 50.0 mol% in terms of Fe ₂ O ₃ and zinc: 15.5 mol% to 24.0 mol% in terms of ZnO. Cobalt: 0.5 mol% to 4.0 mol% in terms of CoO and manganese: 26.5 mol% to 32.0 mol% in terms of MnO as a remainder, and SiO ₂ as a subcomponent as a subcomponent : 50 mass ppm to 300 mass ppm and CaO: 300 mass ppm to 1300 mass ppm, and the remainder contains unavoidable impurities, and the amounts of P, B, S, and Cl in the unavoidable impurities are respectively suppressed to P: less than 50 mass ppm, B: not full 20 mass ppm, S: less than 30 mass ppm, and Cl: less than 50 mass ppm. Further, in the MnCoZn ferrite, the abrasion value is less than 0.85%, the square ratio at 23 ° C is 0.35 or less, and the specific resistance is 30 Ω. m or more, and the Curie temperature is 100 ° C or more. The MnCoZn-based ferrite according to the first aspect of the invention, wherein the MnCoZn-based ferrite has a sintered density of 4.85 g/cm ³ or more. The MnCoZn-based ferrite according to the first or second aspect of the invention, wherein the MnCoZn-based ferrite is a shaped-sintered MnCoZn of a granulated powder having a particle size distribution d90 of 300 μm or less. Ferrite. The MnCoZn-based ferrite according to the first or second aspect of the invention, wherein the MnCoZn-based ferrite is a MnCoZn system of a formed-sintered body comprising a granulated powder having a crushing strength of less than 1.50 MPa. Ferrite. The MnCoZn-based ferrite according to the third aspect of the invention, wherein the MnCoZn-based ferrite is a molded-sintered MnCoZn-based ferrite containing a granulated powder having a crush strength of less than 1.50 MPa. A method for producing a MnCoZn-based ferrite, comprising: a pre-calcining step of pre-calcining a mixture of basic components weighed so as to have a predetermined component ratio; and a mixing-pulverizing step, which is obtained in the pre-calcining step a pre-calcined powder is added with a sub-component adjusted to a predetermined ratio, and mixed and pulverized; and a calcination step, a binder is added to the pulverized powder obtained in the mixing-pulverizing step, and mixed, and then granulated powder is used. The granulation is carried out so that the value of the particle size distribution d90 is 300 μm or less and/or the crush strength is less than 1.50 MPa, and the obtained granulated powder is molded, and the maximum holding temperature is 1290 ° C or higher, and the holding time is 1 The calcination is carried out under the conditions of an hour or more to obtain the MnCoZn-based ferrite as described in the first or second aspect of the patent application. Manufacture of MnCoZn ferrite as described in claim 6 The method of producing, wherein the granulation is a spray drying method.