JPH06310320A - Oxide magnetic substance material - Google Patents

Abstract

PURPOSE:To lower a magnetic loss by a method wherein at least CaO and SiO2 in a specific amount are added to an MnZn-based ferrite and, in addition, at least one kind of a specific metal oxide in a specific amount is added. CONSTITUTION:An oxide magnetic substance material is constituted in such a way that 0.05<=CaO<=0.3wt.% and 0.005<=SiO2<=0.1wt.% as subcomponents are contained in a ferrite whose main component is composed of an oxide of Mn, Zn and Fe and that at least one kind out of TiO2, CaO, CuO and SnO2 is a sintered body containing 0.005<=MxOz<=0.2wt.%. Thereby, it is possible to obtain a ferrite material whose magnetic loss is low. A switching power supply manufactured by using it can be made small, generates little heat and is highly efficient.

Description

Detailed Description of the Invention

[0001]

The present invention relates to an inductance component,
The present invention relates to an oxide magnetic material used for a power transformer core or the like. In particular, the oxide magnetic material of the present invention relates to a low-loss MnZn-based ferrite magnetic material excellent in high frequency characteristics.

[0002]

2. Description of the Related Art With the recent progress in electronics technology, the downsizing and densification of equipment have led to a higher operating frequency. For example, magnetic materials used for transformer magnetic cores for switching power supplies and the like are also required to cope with higher frequencies, and in order to prevent heat generation especially when miniaturized, low magnetic loss at high frequencies is required. Has been done.

For example, magnetic materials used as magnetic core materials are roughly classified into metallic materials and oxide ferrite materials. Metal-based materials have the advantage of high saturation magnetic flux density and high magnetic permeability, but have an electrical resistivity of 10 ^-6 to 10 ^-4.
Since it is as low as Ω · cm, there is a drawback that magnetic loss due to eddy current increases at high frequencies.

Since this drawback is improved by reducing the thickness of the magnetic material, a metal foil processed into a thin foil and wound with an insulator sandwiched between them is also manufactured. There is a problem that the body is limited to about 10 μm, and it is difficult to form a complicated shape and the cost is high. For this reason, it could only be used up to a frequency band of about 100 kHz.

On the other hand, a ferrite material has a saturation magnetic flux density as low as about 1/2 that of a metal material. However, the electrical resistivity is 1 Ω · c for the MnZn type that is usually used.
m, which is much higher than that of metallic materials, and C
By using an additive such as aO or SiO ₂ , the electrical resistivity can be further increased to about 10 to several hundreds Ω · cm, and the magnetic loss due to the eddy current is relatively small up to high frequencies. It can be used without doing. In addition, it has the advantage that it can easily make a complicated shape and is low in cost.

Therefore, for example, as a transformer core material for a power source at a switching frequency of 100 kHz or more,
This ferrite material was generally used.

[0007]

However, even such a ferrite material has a problem that it cannot be used because the magnetic loss due to the eddy current increases at a frequency of 500 kHz or higher. Further, even if the material has a relatively low loss at high frequency, there is a problem that the magnetic loss rapidly increases when the used magnetic flux density is increased.

If the temperature coefficient of the magnetic loss is positive near room temperature, the transformer generates heat due to the magnetic loss during actual use, so that the temperature rises, and as the temperature rises, the magnetic loss further increases and the heat generation becomes large. To become
There is a risk of thermal runaway.

Therefore, although it depends on the operating conditions, it is generally required that the temperature coefficient of the magnetic loss near room temperature is negative, and that the temperature characteristic is such that the magnetic loss is minimized at the temperature actually used. It

However, in the absence of a material having a sufficiently low magnetic loss and a material having a relatively low magnetic loss, the magnetic loss minimum temperature is generally around room temperature and thermal runaway easily occurs, while the magnetic loss minimum temperature is 40 to A material having a temperature of 60 ° C. or higher has a problem of extremely large magnetic loss. Therefore, there has been a problem that a material having an extremely low magnetic loss and a good temperature characteristic has not been obtained until now.

In order to solve the above-mentioned problems of the prior art, it is an object of the present invention to provide a magnetic material having extremely low magnetic loss under high frequency and high magnetic flux density. Moreover, when the temperature characteristic is not preferable, a means for improving this is provided.

[0012]

In order to achieve the above object, the first oxide magnetic material of the present invention comprises a ferrite composed of oxides of Mn, Zn, and Fe as main components and 0% as a subcomponent. 0.05 ≤ CaO ≤ 0.3 wt%, 0.005
≦ SiO ₂ ≦ 0.1% by weight, and further includes Group A (Ti
O ₂ , CoO, CuO, SnO ₂ ) is a sintered body containing at least one kind and 0.005 ≦ M _x O _z ≦ 0.2 wt%.

The second oxide magnetic material of the present invention has the above-mentioned group B (ZrO ₂ , HfO ₂ , Ta).
₂ O ₅ , Al ₂ O ₃ , Ga ₂ O ₃ , In ₂ O ₃ , GeO ₂ , Sb ₂
O ₃ ) is contained in an amount of 0.01% by weight or more and 0.2% by weight or less.

The third oxide magnetic material of the present invention further comprises MgO in an amount of 0.01% by weight or more.
It has a constitution of containing 0.2 wt% or less.

[0015]

According to the above-mentioned constitution of the present invention, at least a specific amount of CaO and SiO _{2 is} added to the MnZn-based ferrite.
Was added, and a specific amount of group A (TiO ₂ , Co
By adding at least one kind of metal oxide of O, CuO, SnO ₂ ), a magnetic material having low magnetic loss can be obtained.

Further, Group B (ZrO ₂ , HfO ₂ , Ta
₂ O ₅ , Al ₂ O ₃ , Ga ₂ O ₃ , In ₂ O ₃ , GeO ₂ , Sb ₂
By adding at least one kind of metal oxide of O ₃ ), a magnetic material having a lower magnetic loss can be obtained.

Of the subcomponents, the roles of CaO and SiO ₂ increase the electric resistance of MnZn ferrite,
The magnetic loss associated with the eddy current is reduced.

The role of the additives of group A is to further reduce the magnetic loss, but the mechanism of loss reduction by these additives is not clear at this time. Some materials, such as TiO ₂ , have a slightly higher electric resistance, but it is considered that the effect is caused by changing the magnetic domain structure or magnetostriction rather than the effect.

The role of the additives of group B is CaO and Si.
It is to increase the electric resistance further together with O ₂ .

The lower limit of the amount added is the minimum necessary for the effect of reducing magnetic loss to appear. On the other hand, the reason for setting the upper limit is that when the addition amount increases too much, the magnetic permeability decreases,
This is to increase the magnetic loss.

However, with respect to CoO, the magnetic loss does not necessarily increase even if a considerably large amount is added. However, there are drawbacks that the magnetic permeability is significantly lowered and the minimum loss temperature is lowered.

Although the minimum loss temperature can be raised by increasing the addition amount of MgO, the loss increases if the addition amount is too large.

When two or more kinds of metal oxides are used as the group A or the group B, the addition amount of one kind is the lower limit of 0.0.
Even if less than 1% by weight, the total amount of two or more kinds is 0.0
If it is 1 weight or more, the effect of lowering the loss appears. Of course, there is no problem even if each of a plurality of types of M _x O _z is within the addition range, and the magnetic loss can be reduced as compared with the case of only CaO and SiO ₂ .

[0024]

[Example] Generally, among magnetic properties of ferrite, saturation magnetic flux density, Curie temperature, minimum loss temperature, etc. depend on the main composition, while permeability, residual magnetic flux density, coercive force, magnetic loss, etc. It is said that this is a characteristic that is dominated by the fine structure, although it is also affected by.

Since the high frequency magnetic loss is mainly caused by the eddy current loss, it is considered that the loss becomes smaller as the electrical resistivity becomes higher. However, the electrical resistivity of MnZn ferrite itself is
As mentioned above, it is not high enough.

For this reason, the mainstream of the development of low magnetic loss MnZn ferrite for high frequencies is to increase the electrical resistivity by using various additives and controlling the fine structure.

On the other hand, the minimum temperature of magnetic loss of MnZn type ferrite has been conventionally explained by the crystal magnetic anisotropy. That is, the sign of the magnetocrystalline anisotropy constant K ₁ changes from a negative value to a positive value as the temperature rises K ₁ = 0
It is said that the magnetic loss has a minimum value at the temperature of.

This temperature coincides with a so-called secondary peak of magnetic permeability, which has a maximum magnetic permeability. This K ₁ monotonically increases with increasing temperature, but since Fe ²⁺ has a positive K ₁ , the amount of Fe ²⁺ increases (that is, Fe ₂ O ₃
The temperature of the secondary peak moves to the lower temperature side (when the amount increases).

Therefore, if the Fe ₂ O ₃ content of the main composition is large, the minimum loss temperature becomes too low, so the Fe ₂ O ₃ content is 54 m.
It was generally about ol% or less.

Further, TiO ₂ and CoO are additives often used for ferrite, but Ti ⁴⁺ is solid-dissolved in the ferrite phase to maintain electric neutrality, so that Fe ³⁺ is changed to Fe ²⁺ . Let

Co ²⁺ itself has a large positive K ₁
have. For this reason, the minimum loss temperature decreases with an increase in the addition amount of these, and therefore, it has not always been used as a low-loss ferrite.

On the other hand, high saturation magnetic flux density, Curie temperature, and magnetic permeability are required as properties of the high-frequency low-loss material other than magnetic loss. These properties are basically required properties of a soft magnetic material and are considered to be important properties for reducing loss ("Powder and powder metallurgy" Vol. 34, No. 5, P191). .

The saturation magnetic flux density increases as the amount of ZnO increases to some extent and the amount of Fe ₂ O ₃ increases. However, Z
If the amount of nO is too large, the Curie temperature decreases, and Fe ₂
It is known that if the amount of O ₃ is too large, the magnetic permeability decreases.

For the above reasons, the main composition of the low-loss MnZn ferrite is Fe ₂ O ₃ of 53 to 54 mo.
It is optimal that the content of ZnO is about 1% and ZnO is about 9 to 12 mol% ("Electronic Ceramics").
1985 winter issue P44).

Most of the low-loss ferrites actually developed are within this composition range, and reduction of loss is centered on the additives and fine structure described above using the main composition in the vicinity. It was

The inventors actually manufactured ferrites in which various metal oxides were added in combination to MnZn-based ferrites having various main composition ratios, and examined the effects of additives / main compositions in detail. As a result, it was found that by adding 3 to 5 or more components, the loss-reducing effect far superior to the conventional one was achieved.

Further, by using these additives in the main composition containing Fe ₂ O ₃ excessively and containing a small amount of ZnO, which is completely different from the conventional ones, 300 kHz to several MHz can be obtained.
However, they have found that ferrite with even lower magnetic loss can be obtained.

For these reasons, the main composition of the oxide magnetic material of the present invention is Fe ₂ O ₃ of 53 to 60 mol.
%, MnO 34-44 mol%, ZnO 0-9mo
It is desirable to include 1%. Further, Fe ₂ O ₃ is 55 to 60 m
ol%, MnO 34-42 mol%, ZnO 0-6
More preferably, it is mol%.

Regarding the loss reduction by the additive, CaO
It is well known that by simultaneously adding SiO ₂ and SiO ₂ and segregating them into grain boundaries, it is possible to increase the electrical resistance and reduce the eddy current loss. The loss can be further reduced by using the A group) and the fourth (B group) additives.

However, according to the study by the inventors,
It is important to precipitate the group B additive also at the grain boundaries. In other words, it is expected that the electrical resistance will increase and the eddy current loss will decrease if a large amount of the additive is used.
In reality, addition of a large amount makes it easier for the additive to form a solid solution in the ferrite phase, thereby increasing the hysteresis loss. Therefore, a low loss material can be obtained by making the amount of the additive as small as possible and precipitating thinly and uniformly at the grain boundaries. Specifically, it is desirable that the concentration of the group B metal oxide in the grain boundary layer is 5 times or more the concentration inside the grain. By adopting such a configuration, the loss can be reduced. Can be done.

On the other hand, it is desirable that the group A and MgO should be solid-dissolved in the ferrite phase. MgO has the effect of raising the minimum temperature of magnetic loss, which is
Fe ²⁺ becomes Fe ³⁺ due to the solid solution of ²⁺ in the ferrite phase.
It is thought that this is because K ₁ decreases and K ₁ decreases.

Another characteristic required for low magnetic loss MnZn ferrite is that the relative density of the sintered body is 4.6 g / cm.
^It is desirable that it is ³ or more. If the sintered density is low, the effective area is reduced and the loss is increased. Further, if the sintering density is low, the atmosphere is likely to be affected by cooling during firing, and especially in a composition containing a large amount of Fe ₂ O _3, it may be difficult to obtain the original characteristics unless the atmosphere is precisely controlled. There is a cause of lowering the production yield.

Next, the magnetic permeability is preferably in the range of 700 to 1600. Further, the electrical resistivity is preferably a direct current resistivity of about 20 to 2 kΩ · cm. The magnetic permeability and the electrical resistivity change depending on the crystal grain size. If the grain size is too small, the magnetic permeability is low, and if it is too large, the electrical resistance is low. Therefore, the average crystal grain size is 10 μm or less,
About 5 μm is desirable.

The MnZn ferrite material of the present invention exhibits an ultra-low magnetic loss even when the measurement frequency is in the MHz band.
Therefore, a switching power supply using this material as a magnetic core and having a switching frequency of 300 kHz to 5 MHz is
Small size and high efficiency. That is, when the oxide magnetic material of the present invention is used as a magnetic core of a switching power supply having a switching frequency of 300 kHz to 5 MHz, a compact and highly efficient switching power supply can be provided.

Hereinafter, the present invention will be described with reference to Examples, focusing on the case where some of the groups A and B are used. However, as shown in Examples 4 to 6, the claims of other inventions are claimed. Even when additives other than those mentioned above were used, similar effects were observed to some extent.

Example 1 As starting materials, powders of α-Fe ₂ O ₃ , MnCO ₃ and ZnO having a purity of 99.5% were used.
The composition ratio of these powders was Fe ₂ O ₃ = 54.5mo.
1%, MnO = 36 mol%, ZnO = 9.5 mol%
And the respective powders were weighed so that the total weight became 300 g. CoO was weighed so as to be 0.05% by weight in the final sintered body, and these powders were wet pulverized for 10 hours in a ball mill, pulverized, and dried.

After calcining this mixed powder in air at 900 ° C. for 2 hours, the amounts of CaO and SiO ₂ became (Table 1),
CaCO ₃ , so that Sb ₂ O ₃ is 0.05% by weight,
SiO ₂ and Sb ₂ O ₃ were added, and the mixture was again wet mixed and ground for 10 hours in a ball mill and dried to obtain a calcined powder.

10% by weight of a 5% by weight aqueous solution of polyvinyl alcohol was added to these calcined powders, and the mixture was passed through a 30 # sieve to granulate. These granulated powders were uniaxially die-molded, and the molded body was binder-out in air at 500 ° C. for 1 hour.

For the firing, the temperature was set to 1200 ° C., the temperature was raised in air, and the O ₂ atmosphere was controlled according to the equilibrium oxygen partial pressure of the ferrite during the maximum temperature holding and cooling. At this time, the firing time and the pressure at the time of molding are set so that the average crystal grain size of the sintered body is 3 to
About 5 μm, the density of the sintered body is about 4.7 g / cm ³ ,
It was changed so as to fall within the range of 4.6 to 4.8 g / cm ³ .

The outer diameter of the obtained sintered body was 2
A ring-shaped sample with a diameter of 0 mm, an inner diameter of 14 mm, and a thickness of 3 mm was cut out, and the magnetic loss at 1 MHz / 50 mT was 20
The measurement was performed in steps of 20 ° C between 0 ° C and 120 ° C.

The magnetic loss was measured by winding a layer of insulating tape around the ring-shaped ferrite core and then measuring the wire diameter of 0.26 mm.
A sample in which a φ insulated conductor was wound around the entire circumference was prepared and measured using an AC BH curve tracer.
As a result, the loss value became the minimum value at 60 ° C. in all the samples. The measured loss values at that time are shown in (Table 1) in units of KW / m ³ .

By the same method, CaO was reduced to 0.1% by weight, SiO ₂ was reduced to 0.05% by weight, and CoO and Sb ₂ were added.
CaCO ₃ , SiO ₂ so that the amount of O ₃ is (Table 2).
When a sintered body to which CoO and Sb ₂ O ₃ were added was prepared and the temperature characteristic of magnetic loss was measured, the amount of CoO was 0.
In the case of less than 05% by weight, the minimum value was obtained at 60 ° C.
However, when the CoO amount is 0.1 to 0.2% by weight, 4
It reached a minimum value at 0 ° C.

Further, in the case of 0.3% by weight, the minimum value was obtained at 20 ° C. Measure the loss value measurement result at the minimum temperature by KW
It is shown in (Table 2) in units of / m ³ .

[0054]

[Table 1]

[0055]

[Table 2]

As is clear from (Table 1) and (Table 2), when either CaO or SiO ₂ is not contained at all, C
Even if it contains oO and Sb ₂ O ₃ , the loss value is large. Also,
The loss is further reduced by adding an appropriate amount of CoO to the one containing CaO and SiO ₂ . Furthermore, the magnetic loss is reduced by adding four types at the same time in a specific amount, and particularly,
05 ≦ CaO ≦ 0.3% by weight, 0.005 ≦ SiO ₂ ≦
0.1% by weight, 0.005% by weight ≦ CoO, 0.01
When it was within the range of ≤Sb ₂ O ₅ ≤0.2% by weight, the magnetic loss was as low as 300 kW / m ³ or less. However, when CoO is 0.3% by weight or more, the minimum loss temperature is as low as 20 ° C. and the relative permeability is 90% or less.
There was a defect that it was too low, about 500, compared with about 0 to 1600 or more.

Example 2 By the same method as in Example 1, the composition ratio Fe ₂ O ₃ = 56.5 mol% and MnO = 38 mol.
%, ZnO = 5.5 mol%, and the total weight is 30
Each powder was weighed so that it would be 0 g. to this,
CoO was weighed so as to be 0.05% by weight in the final sintered body, and these powders were wet-ground for 10 hours in a ball mill, pulverized, and dried.

After calcining the mixed powder in air at 900 ° C. for 2 hours, CaO and SiO ₂ were adjusted to the amounts shown in Table 3 and Ta ₂ O ₅ was adjusted to 0.05% by weight so that CaCO
₃ , SiO ₂ and Ta ₂ O ₅ were added, and the mixture was again wet mixed and pulverized for 10 hours in a ball mill and dried to obtain a calcined powder.

Sinters were prepared from these calcined powders in the same manner as in Example 1 and the temperature characteristics of magnetic loss at 1 MHz and 50 mT were measured. showed that. The measured loss values at that time are shown in (Table 3) in units of KW / m ³ .

By the same method, CaO was reduced to 0.1% by weight, SiO ₂ was reduced to 0.05% by weight, and CoO and Ta ₂ were added.
CaCO ₃ , SiO ₂ so that the amount of O ₅ is (Table 4).
A sintered body to which CoO and Ta ₂ O ₅ were added was manufactured, and the temperature characteristic of magnetic loss was measured.
In the case of 5% by weight or less, the minimum value was obtained at 80 ° C. However, when the amount of CoO was 0.1% by weight, the minimum value was obtained at 60 ° C. Further, when the amount of CoO was 0.2% by weight, it became the minimum value at 40 ° C. In the case of 0.3% by weight, the minimum value was obtained at 20 ° C. The loss value measurement results at the minimum temperature are shown in (Table 4) in units of KW / m ³ .

[0061]

[Table 3]

[0062]

[Table 4]

As is clear from (Table 3) and (Table 4), when either CaO or SiO ₂ is not contained at all, C
Even if it contains oO and Ta ₂ O ₅ , the loss value is large. Also C
The loss can be further reduced by adding an appropriate amount of CoO to an appropriate amount of aO and SiO ₂ . Furthermore, the lowest magnetic loss can be achieved by adding four types at the same time.
Especially 0.05 ≦ CaO ≦ 0.3% by weight, 0.005 ≦ S
iO ₂ ≦ 0.1 wt%, 0.005 wt% ≦ CoO,
In the range of 0.01 ≦ Ta ₂ O ₅ ≦ 0.2 wt%, the magnetic loss was 100 kW / m ³ or less, which was a low magnetic loss.

However, when CoO is 0.3% by weight, the minimum loss temperature is as low as 20 ° C., and the relative permeability is about 3 to 100, compared with the other materials having a relative magnetic permeability of about 700 to 1200.
There was a drawback that it was too low, around 00.

Further, comparing (Table 1) (Table 2) of Example 1 with (Table 3) (Table 4) of this example, the relative permeability of this example with more Fe and less Zn was compared. Magnetic susceptibility is 200
The magnetic loss was small though it was about 400 lower.

(Example 3) As in Example 2, the composition ratio F
e ₂ O ₃ = 57 mol%, MnO = 38 mol%, ZnO
= 5 mol%, and each powder was weighed so that the total weight was 300 g. CoO was 0.2% by weight in the final sintered body and MgO was weighed so that the amount was (Table 5), and these powders were wet-ground for 10 hours in a ball mill and pulverized and dried.

This mixed powder was calcined in air at 900 ° C. for 2 hours, and then 0.1% by weight of CaO and 0.0% of SiO ₂ were obtained.
CaCO ₃ , SiO ₂ and Ta ₂ O ₅ were added so that the amount of Ta ₂ O ₅ became 2% by weight and the amount of Ta ₂ O ₅ became 0.05% by weight, and the mixture was again wet mixed and pulverized for 10 hours in a ball mill and dried.
It was a calcined powder.

Sinters were prepared from these calcined powders in the same manner as in Example 1, and the temperature characteristics of magnetic loss were measured.
The results are shown in (Table 5).

[0069]

[Table 5]

As is clear from Table 5, when MgO was added to a material having a minimum loss temperature of 40 ° C. or less, the minimum loss temperature increased. In particular, when the addition amount was 0.01% by weight or more and 0.2% by weight or less, the loss minimum temperature of 60 to 80 ° C. could be achieved without increasing the loss.

(Example 4) As in Example 1, the composition ratio was Fe ₂ O ₃ = 56.5 mol% and MnO = 37.5 mol.
%, ZnO = 6 mol%, and the respective powders were weighed so that the total weight became 300 g. To this, TiO
₂ , CuO, and SnO ₂ were weighed so that the final addition amounts were as shown in Table 6, and these powders were wet-milled with a ball mill.
h Mixed and crushed and dried.

This mixed powder was calcined in air at 800 ° C. for 2 hours, and then 0.1% by weight of CaO and 0.0% of SiO ₂ were obtained.
CaCO ₃ and SiO ₂ were added so as to be 2% by weight, and the mixture was ground again with a ball mill to prepare a calcined powder.
A sintered body was produced from this calcined powder by the same method as in Example 1.

With respect to the ring-shaped sample cut out from the obtained sintered body, the temperature dependence of the magnetic loss was measured under the same conditions of 1 MHz and 50 mT as in Example 1, and it was found that 0.2% by weight of TiO ₂ was added. In all the samples except the addition of 0.3% by weight, the loss showed a minimum value at 80 ° C. However, TiO ₂
Of 0.2% by weight, the loss showed a minimum value at 60 ° C. Further, when 0.3% by weight was added, a minimum value was exhibited at 20 ° C. This minimum loss value is shown in (Table 6) in units of kW / m ³ .

[0074]

[Table 6]

As is clear from (Table 6), CaO, S
Compared with the addition of iO ₂ only, TiO ₂ , CuO, S
The composite addition of 0.005% by weight or more and 0.2% by weight or less of any of nO ₂ had an extremely low loss within the specific addition range.

Example 5 As in Example 1, the composition ratios were Fe ₂ O ₃ = 56.5 mol% and MnO = 37.5 mol.
%, ZnO = 6 mol%, and the respective powders were weighed so that the total weight became 300 g. To this, TiO
₂ , CoO, CuO, and SnO ₂ were weighed so that the final amount of addition was as shown in (Table 7), and these powders were wet-ground for 10 hours in a ball mill and pulverized and dried.

This mixed powder was calcined in air at 800 ° C. for 2 hours, and then 0.1% by weight of CaO and 0.0% of SiO ₂ were obtained.
2% by weight and Ta ₂ O ₅ at 0.05% by weight, C
aCO ₃ and each metal oxide were added, and the mixture was pulverized and mixed again in a ball mill to obtain a calcined powder. A sintered body was produced from this powder in the same manner as in Example 1.

With respect to the ring-shaped sample cut out from the obtained sintered body, the temperature dependence of the magnetic loss was measured under the same conditions of 1 MHz and 50 mT as in Example 1, and 0.2% by weight of TiO ₂ and CoO was added. In all the samples except the addition of 0.3 wt% and, the loss showed a minimum value at 80 ° C. However, T
With 0.2% by weight addition of iO ₂ and CoO, the loss is 60 ° C.
Shows the minimum value. Moreover, when 0.3% by weight is added, 20
It showed a minimum value at ℃. This minimum loss value is shown in (Table 7) in units of kW / m ³ . Further, the results of the same measurement performed with the measurement magnetic field set to 100 mT are shown in (Table 8). Further, with respect to the case of CoO addition of 0% by weight and the case of 0.05% by weight, the temperature change of the loss value at the measurement magnetic field of 50 mT is shown in (Table 9).

[0079]

[Table 7]

[0080]

[Table 8]

[0081]

[Table 9]

As is clear from (Table 7) and (Table 8), compared with the addition of only CaO, SiO ₂ and Ta ₂ O ₅ , those obtained by adding TiO ₂ , CuO and SnO ₂ in combination were The loss was extremely low in the addition range of 0.005% by weight or more and 0.2% by weight or less. For CoO, 0.00
The loss was low at 5% by weight or more, but at 0.3% by weight,
The minimum loss temperature is reduced to 20 ° C., and the relative magnetic permeability of other samples is about 700 to 1100, whereas the minimum loss is 400.
Degraded with the degree.

When the measuring magnetic field was 100 mT, the effect of reducing the loss by these additives was more remarkable. Further, as is clear from (Table 9), not only the minimum loss value was lowered, but also the effect of reducing loss was observed over the entire temperature range.

Example 6 As in Example 1, the composition ratios were Fe ₂ O ₃ = 56.5 mol% and MnO = 39.5 mol.
%, ZnO = 4 mol%, and the respective powders were weighed so that the total weight became 300 g. CoO
Was weighed so that the final amount was 0.05% by weight, and these powders were mixed and pulverized by a ball mill for 10 hours in a wet manner and dried.

This mixed powder was calcined in air at 800 ° C. for 2 hours, and then 0.1% by weight of CaO and 0.0% of SiO ₂ were obtained.
2% by weight, ZrO ₂ , HfO ₂ , Ta ₂ O ₅ , Al ₂
O ₃ , Ga ₂ O ₃ , In ₂ O ₃ , GeO ₂ , and Sb ₂ O ₃ (Table 1
CaCO ₃ and the respective metal oxides are added so that the amount becomes 0), and the mixture is pulverized and mixed again in a ball mill,
It was a calcined powder. A sintered body was produced from this powder in the same manner as in Example 1.

With respect to the ring-shaped sample cut out from the obtained sintered body, the temperature dependence of the magnetic loss was measured under the same conditions of 1 MHz and 50 mT as in Example 1. The loss was 80 ° C. in any sample. The minimum value was shown. This minimum loss value is shown in (Table 10) in units of kW / m ³ .

[0087]

[Table 10]

As is clear from (Table 10), CaO,
SiO₂, Compared to the addition of CoO only, ZrO₂, H
fO₂, Ta₂O_Five, Al₂O₃, Ga₂O₃, In₂O₃, G
eO ₂, Sb₂O₃What was added in combination was 0.01
Within the range of addition by weight of 0.2% by weight or less, 100k
W / m³It was below the level and extremely low loss.

Next, when these samples were broken and their fracture surfaces were observed, grain boundary fracture occurred in all of them, and the average crystal grain size was about 4 μm. Therefore, regarding the sample of the added amount (0.03 or 0.05% by weight) that resulted in the lowest loss,
The distribution of each group A additive element on the fracture surface was measured using SIMS (secondary ion mass spectrometer).

First, when the analysis range was narrowed down to a diameter of 3 μm and several tens of points were analyzed for the same sample, the concentration of the additive had a slight difference depending on the analysis position. Therefore, the analysis range is 50 ×
The average additive element concentration was determined to be 50 μm, and the profile in the depth direction of each additive from the fracture surface was measured.

As a result, in any additive system, the concentration of the additive element decreases as it goes deeper from the fracture surface (that is, the grain boundary portion) (progresses to the inside of the grain), and from the depth of about several tens nm, the rest. It became almost constant. So with the grain boundary part,
Comparing the concentrations inside the particles where the concentration became almost constant, the concentration at the grain boundary part was about 10 for all the additives.
It was twice as high.

Example 7 In the same manner as in Example 1, the composition ratios were Fe ₂ O ₃ = 56 mol% and MnO = 39 mol.
%, ZnO = 5 mol%, and each was weighed so that the total weight was 300 g, wet-mixed for 10 hours in a ball mill, and dried. This powder is 800 ~ 1200 ℃
Calcination was performed in the air at each temperature for 2 hours. Furthermore, in the final sintered body, CaO is 0.1% by weight, SiO ₂ is 0.02% by weight, Ta ₂ O ₅ is 0.05% by weight, and CoO is 0.05% by weight. , CaCO ₃ and SiO ₂ and T
A ₂ O ₅ and CoO were weighed and added, and again wet-mixed and pulverized in a ball mill for 10 hours to obtain a calcined powder.

The calcined powder was fired at 1200 ° C. for 1 hour in the same manner as in Example 1 to obtain a sintered body. Also,
In the same manner, a sample was prepared in which only Ta ₂ O ₅ or CoO was added at the time of mixing before calcination.

With respect to the ring-shaped sample cut out from the obtained sintered body, the temperature dependence of the magnetic loss of 1 MHz and 50 mT was measured in the same manner as in Example 1, and the loss showed a minimum value at 80 ° C. in any sample. Indicated. The average crystal grain size of the sintered body was measured by observing the fracture surface of the sintered body with an electron microscope. Further, Ta concentration in the grain boundary layer and inside the grains was measured by the same method as in Example 6 to determine the grain boundary portion concentration / grain internal concentration ratio. The results are shown in (Table 11).

[0095]

[Table 11]

As is clear from Table 11, the addition of Ta ₂ O ₅ and CoO results in a lower magnetic loss than that without addition, but the effect is obtained when the Ta concentration ratio is 5 or less. It got smaller. Conversely, No. As shown in 11, it is not preferable that CoO has a large concentration ratio. Further, the sample No. having a sintered body density of 4.6 g / cm ³ or less. 5
In Nos. 10 and 10, the loss was slightly larger than the others.

(Embodiment 8) As in Embodiment 1, Fe
₂ O ₃ , MnCO ₃ , and ZnO have the composition ratios shown in Table 12, and are weighed so that the total weight becomes 300 g.
CoO was further weighed so that the final CoO content would be 0.05% by weight, wet-mixed and ground in a ball mill for 10 hours, and dried. These mixed powders were calcined in air at 850 ° C. for 2 hours, and then 0.1% by weight of CaO, SiO ₂
CaCO ₃ , SiO ₂ and Ta ₂ O ₅ are weighed and added so that the amount of water is 0.02% by weight and the content of Ta ₂ O ₅ is 0.05% by weight, and the mixture is again wet mixed and ground in a ball mill for 10 hours and dried. To obtain a calcined powder.

A sintered body was prepared from these calcined powders in the same manner as in Example 1. Example 1 from the obtained sintered body
The magnetic loss at 1 MHz · 100 mT was measured in steps of 20 ° C to 120 ° C in steps of 20 ° C in the same manner as in. The results are shown in (Table 12).

[0099]

[Table 12]

As is clear from the results of (Table 12), the effect of the main composition is that Fe ₂ O ₃ is 53 mol% or more and 60% or more.
mol% or less, MnO is 34 mol% or more and 44 mol%
In the following, the loss was as low as about 1500 kW / m ³ or less in the range of 0 mol% or more and 9 mol% or less of ZnO. Further, Fe ₂ O ₃ is 55 mol% or more and 60 mol% or more.
Below, MnO is 35 mol% or more and 42 mol% or less, Z
When nO was in the range of 1 mol% or more and 6 mol% or less, the loss was 1000 kW / m ³ or less, which was an extremely low loss. However, when Fe ₂ O ₃ is 60 mol, there is a drawback that the minimum loss temperature is 20 ° C. or less, and the use is limited.

Example 9 As in Example 7, the composition ratio F
e₂O₃= 60 mol%, MnO = 37 mol%, ZnO
= 3 mol%, so that the total weight is 300 g
Each powder was weighed. CoO is finally sintered
0.05% by weight in the body, MgO (Table 13)
And weigh these powders in a ball mill.
Wet wet for 10 hours, pulverized, and dried. This mixed powder
After calcination in air at 900 ° C for 2 hours, CaO and Si
O₂Are 0.1% by weight and 0.02% by weight, respectively.
And Ta₂O_FiveIs 0.05% by weight, CaC
O₃ , SiO₂And Ta₂O _FiveIs added, and the ball
For 10 h, wet mix and pulverize and dry, then calcined powder
did.

Sintered bodies were prepared from these calcined powders in the same manner as in Example 1, and the temperature characteristics of magnetic loss at 1 MHz and 50 mT were measured. The results are shown in (Table 13).

[0103]

[Table 13]

As is clear from Table 13, when MgO is added to a material having a minimum loss temperature of 20 ° C. or less,
The minimum loss temperature rose. In particular, when the addition amount was 0.01% by weight or more and 0.2% by weight or less, the loss minimum temperature of 40 to 60 ° C. could be achieved with almost no increase in loss.

Example 10 In the same manner as in Example 1,
The composition ratio is Fe ₂ O ₃ = 57 mol%, MnO = 40 mol
%, ZnO = next 3 mol%, the CaO 0.1 wt%, a SiO ₂ 0.02 wt%, a ZrO ₂ 0.05 wt%, the sintered body (a) comprising SnO ₂ 0.05 wt% It was made.

Similarly, the composition ratio is Fe ₂ O ₃ = 54 mol
%, MnO = 36 mol%, ZnO = 10 mol%, CaO 0.1 wt%, SiO ₂ 0.02 wt%, ZrO ₂ 0.05 wt%, SnO ₂ 0.05 wt% A conjugate (b) was prepared.

Similarly, the composition ratio is Fe ₂ O ₃ = 54 mol
%, MnO = 36 mol%, ZnO = 10 mol%, and a sintered body (c) containing 0.1% by weight of CaO, 0.02% by weight of SiO ₂ , and 0.05% by weight of Ta ₂ O ₅ was produced. . The magnetic loss of these sintered bodies at 1 MHz and 50 mT was measured by the same method as in Example 1.

The magnetic loss of the sintered body (a) was minimal at 80 ° C., and the loss value was 90 kW / m ³ . Also a sintered body (b)
Has a minimum loss at 60 ° C, and the loss value is 250 kW /
It was m ³ . The above sintered bodies (a) and (b) are the ultra-low magnetic loss materials according to the present invention. The sintered body (c) is a conventional material having a minimum magnetic loss at 60 ° C. and a loss value of 540 kW / m ³ .

For these three types of samples, the product of the magnetic flux density B and the frequency f at each minimum loss temperature,
The magnetic loss was measured under the condition of constant B · f = 50 (mT · MHz) (under this condition, the core size is constant in the power transformer at the same output). The results are shown in (Table 14).

[0110]

[Table 14]

As is clear from (Table 13), these sintered bodies have a minimum loss in the vicinity of 1 to 2 MHz. (a)
Comparing (b) and (c), the sintered bodies (a) and (b) of the present invention are advantageous at 300 kHz or higher. However, 10
At MHz, there was also a considerable increase in loss in these samples.

Next, E type cores were cut out from each of these sintered bodies, a forward type switching power supply circuit was prototyped using the cores, and the temperature rise corresponding to the magnetic loss was evaluated. Under a constant light load condition, the temperature rise of the magnetic core with respect to the frequency and the magnetic flux density of the magnetic core was measured. The results are shown in (Table 15).

[0113]

[Table 15]

As is clear from (Table 15), when the temperature rise allowable value due to the magnetic core loss of the transformer is expected to be 25 ° C., the power supply using the sintered body (c) has a large temperature rise and is used at too high frequencies. I see that I can't. On the other hand, the power source using the ferrite material (a) or (b) of the present invention has a small temperature rise, and particularly in the case of (a), it can be sufficiently used even at 2 MHz or more at 50 mT. This is because the material used has ultra-low magnetic loss and excellent temperature characteristics.
Since it is general to use the magnetic flux with a lower magnetic flux density at higher frequencies, it can be considered that the magnetic flux density can be used up to about 5 MHz from the results of (Table 14). However, a switching power supply of 2 MHz or more increases the loss on the circuit side, and is not practical at this time.

From the above results, the switching frequency using the developed ferrite material is 100 kHz to 2 MHz.
The power source has low heat generation, high efficiency, and low risk of thermal runaway. Further, if the characteristic becomes remarkable especially at 300 kHz or more and the loss on the power supply circuit side is reduced, it can be used up to 5 MHz.

[0116]

As described above, in the present invention, the main component is M
Ferrite consisting of oxides of n, Zn, and Fe is added as a sub-component.
As 0.05 ≦ CaO ≦ 0.3% by weight, 0.005 ≦
SiO ₂≦ 0.1% by weight, and further includes Group A (Ti
O₂, CoO, CuO, SnO₂) At least one type
Upper, 0.005 ≦ M_xO_zSintering containing ≦ 0.2 wt%
It is an oxide magnetic material with the structure of being a body.
Therefore, it is a material with low magnetic loss that has never existed before.
The switching power supply manufactured is small, low heat generation, and high efficiency.
There is an effect that can be.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Osamu Ishii 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Yasuno Aono, 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd. (72) Inventor Masatake Suzumura 1006, Kadoma, Kadoma-shi, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (6)

[Claims] 1. A main component of Mn oxide, Zn oxide, F
In addition to the ferrite containing the oxide of e, 0.05
≦ CaO ≦ 0.3% by weight, 0.005 ≦ SiO ₂ ≤0.
1% by weight of metal oxide of group A shown below
Thing M_xO_zAt least one kind, 0.00
5 ≦ M_xO_zSpecified to be a sintered body containing ≦ 0.2 wt%
Characteristic oxide magnetic material. However, group A metal oxide M
_xO_zIs TiO₂, CoO, CuO, SnO₂In any of
is there. 2. A ferrite containing a subcomponent and a metal oxide of group A.
In addition, the following metal oxides M of group B_xO_zTo
At least one kind, 0.01 ≦ M _xO_z≤
A contract, characterized by being a sintered body containing 0.2% by weight.
The oxide magnetic material according to claim 1. However, metal oxidation of group B
Thing M_xO_zIs ZrO₂, HfO₂, Ta₂O_Five, Al₂O₃,
Ga₂O₃, In₂O₃, GeO₂, Sb₂O₃In any of
It 3. A ferrite containing a minor component and a metal oxide of group A, or a ferrite containing a minor component, a metal oxide of group A and a metal oxide of group B, and MgO further.
The oxide magnetic material according to claim 1 or 2, which is a sintered body containing 0.01% by weight or more and 0.2% by weight or less. 4. The concentration of the grain boundary layer portion of the group B metal oxide M _x O _z is 5 times or more the concentration inside the grain, according to claim 2 or 3. The oxide magnetic material described. 5. An oxide of Fe, which is the main component of ferrite, Fe ₂
O ₃ is 53 mol% or more and 60 mol% or less, Mn oxide MnO is 34 mol% or more and 44 mol% or less, and Zn oxide ZnO is 9 mol% or less.
The oxide magnetic material according to claim 1. 6. An oxide of Fe having a main composition of ferrite, Fe ₂
O ₃ is 55 mol% or more and 60 mol% or less, Mn oxide MnO is 34 mol% or more and 42 mol% or less, and Zn oxide ZnO is 6 mol% or less.
The oxide magnetic material according to claim 1.