JP6964555B2 - MnZnNiCo-based ferrite and its manufacturing method - Google Patents

Description

The present invention relates to MnZnNiCo-based ferrite, which is particularly suitable for the magnetic core of a transformer for a switching power supply, and a method for producing the same.

Magnetic materials are roughly classified into oxide-based magnetic materials and metal-based soft magnetic materials.
The oxide-based magnetic material is classified into a hard magnetic material such as Ba-based ferrite and Sr-based ferrite and a soft magnetic material such as MnZn-based ferrite and NiZn-based ferrite.

The metal-based soft magnetic material has a feature that the saturation magnetic flux density is higher than that of the oxide-based material, but the electric resistance is small. Therefore, when it is used in a high frequency region, there is a problem that iron loss becomes large due to the generated eddy current. Therefore, in recent years, the frequency used has been increasing due to the demand for miniaturization and high density of electronic devices. For example, in a switching power supply used in a high frequency band of about 100 kHz, a metallic soft magnetic material is used. There are few things.

On the other hand, among the above-mentioned oxide magnetic materials, the soft magnetic material is a material that easily magnetizes even with a slight magnetic field, and therefore is widely used in a wide range of fields such as power supplies, communication equipment, measurement control equipment, magnetic recording, and computers. MnZn-based ferrite, which has a small iron loss, has been mainly used as the magnetic core material of the power transformer used in the high frequency band.

This MnZn-based ferrite has a problem that the eddy current loss is high because the electrical resistivity is as low as about 0.01 to 0.05Ω · m. Therefore, there has been a demand for a magnetic material in which the electric resistance is further increased to reduce the eddy current loss, and the iron loss is further reduced as a whole to suppress the calorific value.
To solve this problem, for example, in Patent Document 1, a small amount of an oxide such as calcium oxide or silicon oxide is added to MnZn-based ferrite as a subcomponent to segregate it at the grain boundary to increase the grain boundary resistance as a whole. A technique for solving the problem by increasing the resistivity as a few Ω · m or more is disclosed.

Further, the MnZn-based ferrite for the power source is required to have a high saturation magnetic flux density Bs, a high Curie temperature Tc, and a low magnetic loss Pcv. It is known that the Curie temperature Tc is almost determined by the composition of the main component. Further, it is known that an oxide ferrite compound containing MnZn-based ferrite exhibits ferrimagnetism, and the saturation magnetic flux density and Curie temperature change depending on the type of metal atom having a magnetic moment and the position occupied by the metal atom.

In addition, the saturation magnetic flux density of oxide-based ferrite decreases with increasing temperature and becomes zero at the Curie temperature, which is the temperature at which magnetism disappears. Therefore, the higher the Curie temperature, the more the saturation magnetic flux density from room temperature to the transformer operating temperature. Is known to be able to keep high. As a technique relating to the saturation magnetic flux density, for example, Patent Document 2 discloses that the saturation magnetic flux density can be increased by increasing the amount of _{Fe 2} O _3.

However, in recent years, in the power supply portion of an electronic device, various parts tend to be loaded at a higher density in order to meet the demand for miniaturization. In such a high-density loading state, the temperature at which the ferrite core is used, that is, the operating temperature of the transformer reaches 80 ° C. due to the heat generated by various parts.
The technique described in Patent Document 2 does not particularly mention the operation at a high temperature of 80 ° C.
Further, although Patent Document 3 discloses a technique for reducing iron loss at a high frequency of 500 kHz or more and in a temperature range of 20 to 120 ° C., the absolute value of such iron loss is large and the saturation magnetic flux density. Is not specifically mentioned.

Here, one of the factors governing the iron loss of ferrite is the magnetic anisotropy constant K ₁ . The iron loss changes with the temperature change of the magnetic anisotropy constant K ₁ , and becomes the minimum at the temperature at which _{K 1 = 0.} Therefore, in order to reduce the temperature change of the iron loss of ferrite, it is necessary to reduce the temperature dependence (temperature coefficient of iron loss) of _{the magnetic anisotropy constant K 1.}

The magnetic anisotropy constant K ₁ is almost determined by the types of elements constituting the spinel compound of ferrite, which is the main phase. In the case of MnZn-based ferrite, the temperature dependence is reduced by introducing Co ions, and iron is used. The absolute value of the temperature coefficient of loss can be reduced (see, for example, Non-Patent Documents 1 and 2). This makes it possible to obtain a ferrite material having a small iron loss in the vicinity of room temperature to 100 ° C. and a relatively small iron loss even in the temperature range before and after that.

Regarding such a technique, for example, in Patent Document 4, _{MnZnCo-based ferrite containing Fe 2} O ₃ , ZnO, and MnO as main components and containing 0.01 mol% or more and less than 0.5 mol% of CoO has a wider temperature than before. It is disclosed that K ₁ = 0 in the range, and high magnetic permeability and low loss can be realized in a wide temperature range.
Further, in the ferrite described in Patent Document 4, as shown in FIG. 1 of the same document, an example in which the minimum temperature of the core loss shifts to the low temperature side is introduced.

Special Publication No. 36-002283 Japanese Unexamined Patent Publication No. 11-329822 Special Fair 8-1844 Gazette Special Fair 04-033755

"The Effects of Cobalt subsuititions on some properties of manganese zinc ferrites", A. et al. D. Giles and F. F. Westendorp: J.M. Phys. D: Appl. Phys. 9 (1976) 2117 "Low-loss Power Ferrites for frequencies up to 500 kHz", T.I. G. W. Stijintjes and J. J. Roelofsma; Adv. Cer. 16 (1986) 493

However, when Co is added as described in Patent Document 4, the iron loss temperature coefficient and iron loss are minimized due to slight fluctuations in the firing temperature and the oxygen concentration in the firing atmosphere due to the influence of the contained impurities. Another problem may arise, such as fluctuations in the temperature at which it becomes and the iron loss value greatly deteriorates.

Further, in the above-mentioned conventional techniques (Patent Documents 1 to 4), 300 kHz or more is maintained while maintaining a high saturation magnetic flux density up to the transformer operating temperature, which is necessary for miniaturization and high efficiency of the power supply of electronic components. None of the ferrite materials having the property of exhibiting low loss in a wide temperature range of 0 to 100 ° C. when driven at a high frequency has been realized.

The present invention has been developed in view of the above situation, and is 300 kHz or higher (300 kHz or higher) while maintaining a high saturation magnetic flux density up to the transformer operating temperature (80 ° C.) in order to reduce the size and efficiency of the power supply of electronic components. In particular, it is an object of the present invention to provide an MnZnNiCo-based ferrite material having a small absolute value of iron loss in a wide temperature range of 0 to 100 ° C. when driven at a high frequency of (500 kHz).

In order to solve the above-mentioned problems of the prior art, the inventors have set _{the contents of the basic components such as Fe 2} O ₃ , ZnO, NiO, CoO and MnO to the saturation magnetic flux density, the iron loss, and the like. In addition to investigating the effects of these on the temperature characteristics, we conducted intensive studies on the effects of the sintering densities of various metal oxides and ferrites, which are additive components, on the saturation magnetic flux density, iron loss, and their temperature characteristics.

As a result, after controlling the above basic components in MnZnNiCo-based ferrite within an appropriate range, the selection of sub-components as additive components and their amounts are controlled within an appropriate range, and the sintering density is appropriate. We have found that it is necessary to control the range and further reduce the content of specific elements.

In particular, using iron oxide having a Cl content of 500 mass ppm or less as the iron oxide as a ferrite raw material and suppressing the Cl content in the final sintered body to 80 mass ppm or less is the effect of the present invention. We have found that it is extremely effective and completed the present invention. It was also found that the Sr content must be 10.0 mass ppm or less and the Ba content must be 10.0 mass ppm or less in order to exhibit such an effect.

The present invention has been completed by further studying based on the above findings, and the gist structure of the present invention is as follows.
1. 1. MnZnNiCo-based ferrite consisting of basic components, sub-components and unavoidable impurities.
Basic ingredients,
Fe ₂ O ₃ : 53.00 to 57.00 mol%,
ZnO: 4.00-11.00 mol%,
NiO: 0.50 to 4.00 mol% and CoO: 0.10 to 0.50 mol%
The rest is MnO
Including as
Sub-ingredients with respect to the basic ingredients
SiO ₂ : 50-500 mass ppm,
CaO: 200-2000 mass ppm and Nb ₂ O ₅ : 50-500 mass ppm
Including as
Further, Cl, Sr and Ba in the unavoidable impurities are each set to Cl: 80 mass ppm or less with respect to the basic component.
Sr: 10.0mass ppm or less and Ba: 10.0mass ppm or less are suppressed and included.
The MnZnNiCo-based ferrite, wherein the sintering density of the MnZnNiCo-based ferrite is in the range of ^{4.65 to 4.85 Mg / m 3.}

When the saturation magnetic flux density at a magnetization force of 1200 A / m at 2.80 ° C is 400 mT or more, the maximum magnetic flux density is 50 mT and the frequency is 500 kHz, the iron loss at 0 to 100 ° C is 100 kW / m ³ or less, and iron. The MnZnNiCo-based ferrite according to 1 above, wherein the iron loss at the minimum loss temperature is 75 kW / m ^{3 or less.}

3. 3. The basic components Fe, Zn, Ni, Co and Mn raw materials are mixed, calcined and crushed, and then the sub-components Si, Ca and Nb raw materials are mixed, crushed and then molded. A method for producing MnZnNiCo-based ferrite, which comprises a series of steps of firing at a maximum temperature in the range of 1050 to 1250 ° C.
A method for producing MnZnNiCo-based ferrite, wherein the Fe raw material is iron oxide, and the Cl content in the iron oxide is iron oxide of 500 mass ppm or less.

4. The method for producing MnZnNiCo-based ferrite according to 3 above, wherein the MnZnNiCo-based ferrite is the MnZnNiCo-based ferrite according to 1 or 2.

According to the present invention, it is possible to provide an MnZnNiCo-based ferrite having a small magnetic loss in a wide temperature range when a high frequency drive of 300 kHz or more is performed while maintaining a high saturation magnetic flux density until the transformer operating temperature (80 ° C.) is reached. Can be done.
Further, since the present invention has excellent magnetic characteristics at high frequencies, it is possible to reduce the size of the power transformer and reduce the iron loss.

Hereinafter, the present invention will be specifically described.
_{The MnZnNiCo-based ferrite of the present invention contains the following appropriate amounts of Fe 2} O ₃ , ZnO, NiO and CoO from the viewpoint of optimizing the temperature characteristics of iron loss and iron loss during high-frequency driving, and the balance is MnO. It has basic ingredients.

First, the basic components of the MnZnNiCo-based ferrite of the present invention will be specifically described.
Fe ₂ O ₃ : 53.00 to 57.00 mol% in the basic components
Fe ₂ O ₃ needs to have a mol ratio of 53.00 mol% or more in the basic component in order to set the saturation magnetic flux density at 80 ° C. to 400 mT or more. On the other hand, if _{the mol ratio of Fe 2} O ₃ in the basic component exceeds 57.00 mol%, the iron loss becomes too large. Therefore, the upper limit is set to 57.00 mol%. It is preferably in the range of 54.50 to 56.50 mol%.

ZnO: 4.00-11.00 mol% of the basic components
In order to reduce the iron loss of ZnO and maintain the iron loss in a wide temperature range from 0 to 100 ° C. at a maximum magnetic flux density of 50 mT and a frequency of 500 kHz, the amount of ZnO added is included in the basic components. The mol ratio needs to be in the range of 4.00 to 11.00 mol%. It is preferably in the range of 5.50 to 8.50 mol%, more preferably 6.0 to 8.00 mol%.

NiO: 0.50 to 4.00 mol% of the basic ingredients
NiO has a saturation magnetic flux density of 80 ° C. of 400 mT or more, reduces iron loss, and maintains a small iron loss in a wide temperature range from 0 to 100 ° C. at a maximum magnetic flux density of 50 mT and a frequency of 500 kHz. In order to do so, the amount of addition must be in the range of 0.50 to 4.00 mol% in terms of the mol ratio in the basic component. It is preferably in the range of 1.50 to 3.50 mol%, and more preferably in the range of 1.00 to 3.00 mol%.

CoO: 0.10 to 0.50 mol% in the basic ingredients
CoO also has a function of reducing the temperature coefficient of magnetic permeability, as described in Japanese Patent Publication No. 52-4753. However, when CoO is excessively contained, not only the temperature coefficient of iron loss becomes positive at room temperature or higher and thermal runaway occurs, but also the change with time becomes large, which is not desirable. Therefore, the upper limit of CoO is 0.50 mol% in terms of the mol ratio in the basic component. On the other hand, when the amount of CoO added is small, the effect of improving the temperature coefficient becomes small, and improvement of the iron loss value cannot be expected. Therefore, the lower limit of CoO is 0.10 mol% as the mol ratio in the basic component.

The ferrite of the present invention is an MnZnNiCo-based ferrite, and _{the rest of the basic components other than Fe 2} O ₃ , ZnO, NiO and CoO is manganese oxide (MnO). The preferable range of MnO is 31.50 to 40.00 mol% in mol ratio in the basic component, and more preferably 31.80 to 39.80 mol%.

The basic components of the MnZnNiCo-based ferrite of the present invention have been described above, but the MnZnNiCo-based ferrite of the present invention needs to contain the following additive components as subcomponents in addition to the above basic components. _{That is, Fe 2} O ₃ , ZnO, MnO, NiO and CoO, which are the basic components of the ferrite of the present invention, _{form a spinel structure, but SiO 2} , CaO and Nb ₂ O which do not form a spinel are formed therein. _A high-performance Mn—Zn-based ferrite having a smaller iron loss can be obtained by compound-adding an auxiliary component such as 5. _{In addition, components such as Ta 2} O ₅ , _{Zr O 2} and V ₂ O ₅ that do not form spinel may be further added in a small amount.

SiO ₂ : 50 to 500 mass ppm with respect to the basic component
SiO ₂ forms a high resistance phase at the grain boundaries together with CaO, and contributes to the reduction of iron loss. However, if the addition amount is less than 50 mass ppm, the addition effect is small. On the other hand, if it is contained in excess of 500 mass ppm, abnormal grain growth occurs during sintering and iron loss is significantly increased. Therefore, SiO ₂ needs to be added in the range of 50 to 500 mass ppm with respect to the basic component. The range of 50 to 300 mass ppm is preferable in order to surely prevent the generation of abnormal particles in the sintered body structure.

CaO: 200-2000 mass ppm for the basic component
When CaO _{coexists with SiO 2,} it increases the grain boundary resistance and contributes to lower iron loss, but when the addition amount is less than 200 mass ppm, the effect is small. On the other hand, when it exceeds 2000 mass ppm, the iron loss increases on the contrary. Therefore, CaO needs to be added in the range of 200 to 2000 mass ppm with respect to the basic component. In order to obtain a ferrite having a lower iron loss, CaO is preferably in the range of 200 to 1500 mass ppm.

Nb ₂ O ₅ : 50 to 500 mass ppm with respect to the basic component
Nb ₂ O ₅ effectively contributes to the increase of specific resistance in the coexistence of SiO ₂ and CaO, but its addition effect is poor when the content is less than 50 mass ppm. On the other hand, if it exceeds 500 mass ppm, the iron loss will increase. Therefore, Nb ₂ O ₅ needs to be added in the range of 50 to 500 mass ppm with respect to the basic component. In order to obtain a ferrite having a lower iron loss, Nb ₂ O ₅ is preferably in the range of 50 to 300 mass ppm.

The sintering density of ferrite in the present invention is in the range of ^{4.65 to 4.85 Mg / m 3.} If it is less than 4.65 Mg / m ³ , the iron loss will be large. On the other hand, if ^{it exceeds 4.85 Mg / m 3} , the iron loss during high frequency driving becomes large. In order to obtain a ferrite having a lower iron loss, the sintering density is preferably in the range of ^{4.70 to 4.80 Mg / m 3.}

Next, the unavoidable impurities in the present invention will be described.
The components other than those described above of the MnZnNiCo-based ferrite in the present invention are unavoidable impurities. Examples of this unavoidable impurity include Cl, Sr, Ba, P and B. Then, as described below, Cl, Sr and Ba are components that are particularly suppressed to a predetermined amount or less. The smaller the content of unavoidable impurities, the better, and it may be 0 mass%, but industrially, it is preferably about 0.01 mass% or less.

Cl: 80 mass ppm or less In order to suppress the generation of abnormal grains in the sintered structure and the variation in grain size distribution of crystal grains, and to suppress the decrease in saturation magnetic flux density due to the improvement in the density of the sintered core, iron oxide as a raw material It is necessary to reduce the amount of Cl in the mixture to 500 mass ppm or less, and to reduce the amount of Cl remaining in the final sintered body after firing, that is, the MnZnNiCo-based ferrite to 80 mass ppm or less.

Sr: 10.0mass ppm or less, Ba: 10.0mass ppm or less As described above, the MnZnNiCo-based ferrite of the present invention has the composition of the basic components Fe ₂ O ₃ , ZnO, MnO, NiO and CoO within the above range. In addition to controlling, it is necessary to add SiO ₂ , CaO and Nb ₂ O as subcomponents in an appropriate amount in a complex manner. However, in order to stably realize low iron loss in the temperature range of 0 to 100 ° C., it is necessary to limit the contents of Sr and Ba in addition to Cl contained as a trace component.

Here, Sr and Ba are elements used when forming hexagonal ferrite, so-called hard ferrite, without having a spinel structure. The mechanism by which these Sr and Ba affect the magnetic properties of MnZnNiCo-based ferrite, which is the final sintered body, especially the iron loss and magnetic permeability in the temperature range of 0 to 100 ° C. has not been clarified yet. However, the inventors think as follows. That is, when Co is contained, which has a great influence on the magnetic anisotropy, such as MnZnNiCo-based ferrite of the present invention, it is considered that the interaction with Co is exhibited and it becomes difficult to reduce the iron loss value. ..

In order to realize low iron loss in the temperature range of 0 to 100 ° C. as in the present invention, the contents of Sr and Ba must be 10.0 mass ppm or less, respectively, and exceed 10.0 mass ppm. If it is contained, a predetermined low iron loss value cannot be obtained. Therefore, the contents of Sr and Ba are suppressed to the range of 10.0 mass ppm or less. Further, in order to realize low iron loss, it is preferable to keep the Sr and Ba contents in the range of 7.0 mass ppm or less.

_{Further, Sr and Ba may be contained in iron oxide (Fe 2} O ₃ ), zinc oxide (ZnO), and manganese oxide (MnO), which are the raw materials of the main components. Therefore, the contents of Sr and Ba may be adjusted by adjusting the amounts of various iron oxide, zinc oxide and manganese oxide raw materials having different contents of Sr and Ba.

Next, the method for producing MnZnNiCo-based ferrite in the present invention will be described.
In the MnZnNiCo-based ferrite of the present invention, first, _{powder raw materials of Fe 2} O ₃ , ZnO, MnO, NiO and CoO are weighed so as to have a predetermined ratio specified in the present invention, and these are sufficiently mixed and calcined. And crush to obtain calcined powder.
At this time, it is important to suppress the Cl content in _{iron oxide (Fe 2} O ₃ ), which is an Fe raw material, to 500 mass ppm or less. For that purpose, for example, the iron oxide obtained by the iron chloride roasting method is washed. The Cl content in iron oxide for ferrite is 0.15% (= 1500 mass ppm) or less in JIS K1462 (1981), but it is important to further reduce it in the present invention.

Next, the above-mentioned sub-ingredients are added to the temporary baking powder so as to have a predetermined ratio specified in the present invention, mixed, and further pulverized. In this pulverization work, it is necessary to sufficiently homogenize the added components so that the concentration is not biased. After that, an organic binder such as polyvinyl alcohol is added to the crushed calcined powder, granulated, and further pressure is applied to form a predetermined shape, which is then fired to form a sintered body (product). do.

Here, it is important that the firing conditions are such that the maximum temperature during firing is in the range of 1050 to 1250 ° C. This is because the sintering density of the ferrite of the present invention can be obtained. In order to obtain a more stable ferrite sintering density, the maximum temperature during firing is preferably in the range of 1100 to 1200 ° C. The other conditions of the firing are not particularly limited as long as the above-mentioned ferrite sintering density can be obtained, but the holding time at the above-mentioned maximum temperature is in the range of 3 to 8 hours, and the oxygen concentration at the above-mentioned maximum temperature. Is preferably in the range of 1 to 5 vol%. The other conditions of the firing may be in accordance with a conventional method.

The MnZnNiCo-based ferrite thus obtained has a saturation magnetic flux density of 400 mT or more at a magnetization force of 1200 A / m at 80 ° C., a maximum magnetic flux density of 50 mT, and a frequency of 500 kHz, which was extremely difficult to realize with the conventional MnZn-based ferrite. The iron loss at 0 to 100 ° C. measured in 1 is 100 kW / m ³ or less, and further, at the temperature at which the iron loss measured at the maximum magnetic flux density of 50 mT and the frequency of 500 kHz is the minimum (also referred to as the minimum iron loss temperature in the present invention). The present invention has a characteristic of iron loss of 75 kW / m ³ or less, and has a small magnetic loss in a wide temperature range when driving at a high frequency of 300 kHz or more while maintaining a high saturation magnetic flux density up to a transformer operating temperature (80 ° C.). MnZnNiCo-based ferrite.

The other steps of producing the MnZnNiCo-based ferrite powder and the step of producing the sintered body (MnZnNiCo-based ferrite) are not particularly limited, and the so-called conventional method may be followed.

Hereinafter, examples confirmed for the present invention will be described.
The _{raw materials of Fe 2} O ₃ , ZnO, MnO, NiO and CoO were mixed so as to have various compositions shown in Tables 1 and 2. As these raw materials, those having different impurities contents were used.
After the above mixing, calcining was carried out at 930 ° C. for 3 hours and pulverized to obtain calcined powder. _{SiO 2} , CaO and Nb ₂ O ₅ as subcomponents were added to the obtained calcined powder in the amounts shown in Tables 1 and 2, and the mixture was pulverized with a ball mill for 10 hours. Then, polyvinyl alcohol was added as a binder to the pulverized powder, and the granulated powder was granulated to obtain a granulated powder. Then, the granulated powder was formed into a ring shape having an outer diameter of 36 mm, an inner diameter of 24 mm, and a height of 12 mm. Was used as a molded body. Then, this molded product was calcined at the maximum temperature shown in Tables 1 and 2 in a mixed gas of nitrogen and air in which the oxygen partial pressure was controlled in the range of 1 to 5 vol% for 3 hours to obtain a ring-shaped sample (a ring-shaped sample). Ferrite sintered body) was obtained. In Tables 1 and 2, the amount of Cl in iron oxide, the amount of Cl in the sintered body, the amount of Sr, and the amount of Ba were measured by a fluorescent X-ray analysis according to a conventional method, and the sintering density was determined by using the above ring-shaped sample. It was measured according to the Archimedes method. Further, in the above firing, the rate of temperature rise from 500 ° C. to the maximum temperature of firing was set to 650 ° C./h.

When the ring-shaped sample obtained as described above is wound with 20 turns on the primary side and 40 turns on the secondary side and a magnetic field of 1200 A / m is applied by a DC BH loop tracer at 20 to 200 ° C. The magnetic flux density was measured. This is because the magnetic flux is almost saturated in a magnetic field of this magnitude, and the value of the magnetic flux density at this time is considered to be the saturated magnetic flux density.

Further, 5 windings on the primary side and 5 windings on the secondary side were applied, and an AC BH loop tracer was used to measure the iron loss when the temperature was changed and the magnetic flux density was excited to a magnetic flux density of 50 mT at a frequency of 500 kHz.

Based on the above measurement results, the density of the ferrite sintered body, the saturation magnetic flux density at 80 ° C., the iron loss minimum temperature, and the iron loss values at 0 ° C., 100 ° C. and the iron loss minimum temperature are shown in Tables 1 and 2, respectively. Described. Here, No. 1 in Table 1. 1-1 to 1-24 are examples of inventions conforming to the present invention, while No. 1 to Table 2 shows No. 2-1 to 2-28 show comparative examples outside the scope of the present invention. No. in Table 1 In 1-1 to 1-20, the maximum temperature during firing was set to 1150 ° C., and No. 1 in Table 1 was set. 1-21 to 1-24 changed the maximum temperature during firing to one of 1050 ° C, 1100 ° C, 1200 ° C and 1250 ° C, respectively.

As can be seen from the table, the ferrite raw material is obtained after appropriately selecting the compositions of _{the basic components of Fe 2} O ₃ , ZnO, MnO, NiO and CoO _{and the sub-components of SiO 2} , CaO and Nb ₂ O _5. An invention in which iron oxide having a Cl content of 500 mass ppm or less is used as iron oxide, the Cl content in the final sintered body is suppressed to 80 mass ppm or less, and Sr and Ba are controlled to 10.0 mass ppm or less. All of the MnZnNiCo-based ferrites in the examples have a magnetization force of 1200 A / m and a saturation magnetic flux density of 400 mT or more at a measurement temperature of 80 ° C. Further, the iron loss at 0 and 100 ° C. measured at a maximum magnetic flux density of 50 mT and a frequency of 500 kHz is 100 kW / m ³ or less, and the iron loss at the minimum iron loss temperature is 75 kW / m ³ or less.
From these facts, it can be seen that according to the present invention, a MnZnNiCo-based ferrite material having low iron loss can be obtained in the temperature range of 0 to 100 ° C. while maintaining a high saturation magnetic flux density.

On the other hand, the MnZnNiCo-based ferrites of the comparative examples, which do not satisfy any of the component compositions of the present invention, have a maximum magnetic flux density of 50 mT, an iron loss measured at a frequency of 500 kHz, and an iron loss value at any temperature of 0 or 100 ° C. Is over 100 kW / m ³ . Further, the iron loss value at the minimum iron loss temperature is only obtained in excess of ^{75 kW / m 3.}

The present invention can provide MnZnNiCo-based ferrite having a high saturation magnetic flux density and a small magnetic loss in a wide temperature range even at a high frequency of 300 kHz or higher, particularly 500 kHz, and thus can be used in in-vehicle equipment, industrial equipment, and the like. It can be widely applied to high-frequency drive power supplies using increasing SiC and GaN semiconductor devices.

Claims (2)

MnZnNiCo-based ferrite consisting of basic components, sub-components and unavoidable impurities.
Basic ingredients,
Fe ₂ O ₃ : 53.00 to 57.00 mol%,
ZnO: 4.00-11.00 mol%,
NiO: 0.50 to 4.00 mol% and CoO: 0.10 to 0.50 mol%
The rest is included as MnO
Sub-ingredients with respect to the basic ingredients
SiO ₂ : 50-500 mass ppm,
CaO: 200-2000 mass ppm and Nb ₂ O ₅ : 50-500 mass ppm
Including as
Further, Cl, Sr and Ba in the unavoidable impurities are each set to Cl: 80 mass ppm or less with respect to the basic component.
Sr: 10.0mass ppm or less and Ba: 10.0mass ppm or less are suppressed and included.
What sintered density 4.73 ~4.85Mg / m ³ range der of the MnZnNiCo ferrite,
The saturation magnetic flux density at a magnetization force of 1200 A / m at 80 ° C. is 400 mT or more.
When the maximum magnetic flux density frequency 50mT is 500 kHz, the iron loss at 0 to 100 ° C. is at 100 kW / m ³ or less, the iron loss at iron loss minimum temperature, characterized in der Rukoto 75kW / m ³ or less MnZnNiCo System ferrite. The basic components Fe, Zn, Ni, Co and Mn raw materials are mixed, calcined and crushed, and then the sub-components Si, Ca and Nb raw materials are mixed, crushed and then molded. A method for producing MnZnNiCo-based ferrite, which comprises a series of steps of firing with the maximum temperature in the range of 1050 to 1250 ° C. and the holding time at the maximum temperature of 3 to 8 hours.
The Fe raw material is iron oxide, Cl content in the oxide iron is Ri iron oxide der follows 500mass ppm, the MnZnNiCo ferrite is characterized MnZnNiCo ferrite der Rukoto according to claim 1 A method for producing MnZnNiCo-based ferrite.