JP2001118714A - Small-loss oxide magnetic material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive, small-loss oxide magnetic material which is small in loss at its working temperature in a working environment. SOLUTION: An oxide magnetic material contains 52.5-53.5 mol % Fe2O3, 35.0-45.0 mol%; MnO, and the balance ZnO as main components and 0.005-0.05 wt.% SiO2, 0.01-0.1 wt.% CaO, 0.2-5.0 wt.% CuO, and at least 0.01-2.0 wt.% V2O5, 0.005-0.1 wt.% Nb2O5 or 0.005-0.5 wt.% TiO2 as accessory components. The crystal grain size of the material is adjusted to 5-10 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an oxide magnetic material, and more particularly to a low-loss oxide magnetic material used for a switching power supply and the like.

[0002]

2. Description of the Related Art In recent years, miniaturization of electronic devices such as portable devices has been rapidly progressing. Power supplies used in these electronic devices follow the same flow. The transformer that constitutes the power supply has a large volume and a large power loss.
Its miniaturization and high efficiency are urgently needed.

One solution is to increase the driving frequency, and a low-loss oxide magnetic material applied to a magnetic core used in a transformer is desired.

[0004] The characteristics required of the magnetic core material include a low loss at the drive frequency, a high saturation magnetic flux density,
High Curie temperature, high specific resistance, and the like.

In general, ferrite is used as a magnetic core material for transformers. A typical Mn-Zn ferrite material is Fe ₂
A main component composed of O ₃ , MnO, and ZnO, and CaO, Si
And O _{2 and} other additive components.

[0006] The loss of ferrite is the hysteresis loss,
It is known that it consists of eddy current loss and residual loss. Hysteresis loss is loss associated with irreversible motion of the domain wall.

In order to reduce the hysteresis loss, it is necessary to reduce factors that hinder the movement of the domain wall such as inclusions and pores, to increase the crystal grain size, and to increase the magnetic domain size.

The eddy current loss is a loss generated by electromagnetic induction, and increases in proportion to the specific resistance. Further, the cause of the residual loss is unknown, and even the loss factor has not been elucidated.

If the loss of ferrite is large, not only the efficiency as a power supply is poor, but also a problem of thermal runaway due to self-heating occurs. Generally, the loss of Mn-Zn ferrite used as a material for a magnetic core used in a power transformer is as follows.
It is designed to be minimum in the temperature range of 60 to 100 ° C, but this is due to the environmental temperature of the power supply being 60 to 100 ° C.

[0010]

However, if the temperature at which the loss is minimized is lower than the ambient temperature, there is a problem of thermal runaway because the loss increases due to the temperature rise. On the other hand, if the temperature is too high, the hysteresis loss, which is considered to be caused by an increase in the magnetocrystalline anisotropy constant, causes an increase in the loss at room temperature.

Accordingly, an object of the present invention is to provide a low-loss oxide magnetic material which can be fired at a low temperature in order to produce a low-loss material at a low operating temperature and at a low cost.

[0012]

As a result of various studies, the present inventor has found that Fe-Mn having a spinel type crystal structure has been developed.
The main component composition of the Zn-based ferrite is 52.5;
～53.5Mol% of _Fe 2 _O 3, _35.0~45.0m
% of MnO and the balance of ZnO, and 0.005 to 0.05 wt% of SiO ₂ , 0.01 as sub-components.
~ 0.1 wt% CaO and 0.2-5.0 wt% C
uO, and 0.01 to 2.0 wt% of V
₂ O ₅ , 0.005 to 0.1 wt% Nb ₂ O ₅ , 0.0
It has been found that low-temperature sintering is possible and loss can be reduced by containing at least one of TiO ₂ of 0.5 to 0.5 wt% and further setting the average crystal grain size to 5 to 10 μm.

That is, the present invention relates to an Fe--Mn--Zn ferrite having a spinel type crystal structure, wherein the main component composition is 52.5 to 53.5 mol% of Fe ₂ O ₃ , 35.
0 to 45.0 mol% of MnO and the balance being ZnO, and 0.005 to 0.05 wt% of Si as a subcomponent.
O ₂ , 0.01-0.1 wt% CaO, and 0.2-5.
A low-loss oxide magnetic material containing 0 wt% CuO.

The present invention also provides the low-loss oxide magnetic material as described above, wherein 0.01 to 2.0 wt% of V ₂ O ₅ , 0.005 to
0.25 wt% Nb ₂ O ₅ , 0.005 to 0.5 wt%
A low-loss oxide magnetic material comprising at least one of TiO ₂ of the present invention.

Further, the present invention provides the low-loss oxide magnetic material described above, wherein the crystal grain size is 5 to 10 μm.

According to the present invention, by adding CuO, densification in the sintering process is promoted, and sintering can be performed at a lower temperature than before.

Further, SiO ₂ , CaO, Nb ₂ O ₅ , V
By adding ₂ O ₅ and concentrating it in the grain boundary layer, the specific resistance increases.

TiO ₂ forms a solid solution in the crystal grains and forms Fe ³⁺
To reduce the negative anisotropy constant. Further, by adding TiO ₂ , Fe ³⁺ decreases and the specific resistance increases. Since the eddy current loss (Pe) is proportional to the reciprocal of the specific resistance, the eddy current loss can be reduced.

Although the cause is unknown, the resonance loss, which is one of the residual losses, can be reduced by setting the average crystal grain size to 5 to 10 μm.

The main component compositions of 52.5 to 53.5 mol% of Fe ₂ O ₃ and 35.0 to 45.0 mol% of MnO are as follows: Fe ₂ O ₃ is 52.5 mol% or less and MnO is 4 MnO.
If the content is 5 mol% or more, the temperature at which the loss is minimized is much higher than the ambient temperature of the transformer, and the loss at room temperature is significantly increased. Further, Fe ₂ O ₃ is 53.5.
If the content is at least mol% and the content of MnO is at most 35 mol%, the temperature at which the loss is minimized will be lower than the ambient temperature, and problems such as thermal runaway will occur.

The reason why the content of SiO ₂ is 0.005 to 0.05 wt% is that if the content is less than 0.005 wt%, sufficient specific resistance cannot be obtained and the loss increases.
This is because abnormal grain growth occurs when the above is exceeded, and the loss increases.

The reason why the content of CaO is set to 0.01 to 0.1 wt% is that if the content is less than 0.01 wt%, sufficient specific resistance cannot be obtained and the loss increases, so that the content is 0.1 wt% or more. This is because abnormal grain growth and loss increase.

The reason why the content of CuO is 0.2 to 5.0 wt% is as follows.
If the content is less than 0.2 wt%, no sufficient improvement in sinterability is observed, and the density of the sintered body is low and the loss increases.
If the content is 0 wt% or more, abnormal grain growth occurs, and the loss increases.

The reason why the amount of V ₂ O ₅ is 0.01 to 2.0 wt% is that if the content is less than 0.01 wt%, a sufficient improvement in specific resistance cannot be seen. If there is, the density of the sintered body becomes low and the loss increases.

The reason that the amount of Nb ₂ O ₅ is 0.005 to 0.1 wt% is that if the content is less than 0.005 wt%, a sufficient improvement in specific resistance cannot be seen. If there is, the density of the sintered body becomes low and the loss increases.

The reason why the amount of TiO ₂ is set to 0.005 to 0.5 wt% is that when the content is less than 0.005 wt%, a sufficient improvement in specific resistance cannot be seen, and when the content is more than 0.5 wt%. This is because the density of the sintered body decreases and the loss increases.

The reason why the average crystal grain size is 5 to 10 μm is as follows.
If the thickness is 5 μm or less, the hysteresis loss increases, and the loss deteriorates. If the thickness is 10 μm or more, the loss which is considered to deteriorate the residual loss increases.

[0028]

Embodiments of the present invention will be described below in detail.

(Embodiment 1) The main component composition is 52.0.
~ 54.0 mol% Fe₂O₃, 34.0-46.0m
ol% MnO and the balance ZnO.
Mixing at 850 ° C for 2 hours in air atmosphere.
Calcination, 0.03 wt% SiO as a sub-component ₂, 0.
05 wt% CaO and 3.0 wt% CuO were added.
Thereafter, fine pulverization was performed with a ball mill. After fine grinding, binder
And granulate with a spray drier, φ30 ×
Molded into a toroidal shape of φ25 × 5mm, reducing atmosphere
It was sintered at 1200 ° C. in air. Wind the core obtained.
Then, samples 1-1 to 1-9 shown in Table 1 were manufactured. This trial
Core loss at 100kHz-2000G-80 ° C,
Table 1 shows the results of measuring the average crystal grain size and the sintered body density.
Show.

As the conventional material 1, 53.0 mol% of Fe ₂ O ₃ and 35 mol% of M
The main component composition of nO and the balance ZnO.
O ₂ and 0.03 wt%, was added 0.05 wt% of CaO, without CuO is added, then molded into a toroidal shape of φ30 × φ25 × 5mm, and sintered at 1200 ° C.. A winding was applied to the obtained core to obtain a comparative product shown in Table 1. Table 1 shows the results of measuring the core loss, average crystal grain size, and sintered body density of this comparative product at 100 kHz-2000 G-80 ° C.

[0031]

[Table 1]

According to Table 1, the main component composition was 52.5 to 53.5.
mol% of _Fe 2 _O 3, _{35.0~45.0mol%} of M
It can be seen that the invention product in which nO and the remainder are ZnO has better core loss than the conventional material and the material having the main component composition outside the scope of the present invention.

(Embodiment 2) The main component composition is 53.0 m
ol% of _Fe 2 _O 3, _39.0mol% of MnO, and weighed so as to balance ZnO, a ball mill and mixed with, and calcined for 2 hours at 850 ° C. in an air atmosphere, the SiO ₂ as subcomponent 0 0.003 to 0.07 wt%, CaO is 0.1%.
After adding 05 wt% and 3.0 wt% of CuO, the mixture was finely pulverized by a ball mill. After fine pulverization, a binder was added and granulated with a spray drier.
Formed into a 5 mm toroidal shape and placed in a reducing atmosphere
By sintering at 00 ° C., samples 2-1 to 2-6 were prepared.

As a conventional material 2, a sample having the same main component composition and the same amount of additive but without adding CuO was prepared in the same manner, and sintered at 1200 ° C. A winding was applied to the obtained core, and the core loss at 100 kHz-2000 G-80 ° C., the average crystal grain size, and the specific resistance were measured. The results are shown in Table 2.

[0035]

[Table 2]

According to Table 2, the content of SiO ₂ was 0.005 to 0.05.
It can be seen that the core loss is smaller than that of the conventional material 2 in the sample to which wt% is added.

(Embodiment 3) The main component composition is 53.0.
mol% Fe ₂ O ₃ , 39.0 mol% MnO, and the balance ZnO were weighed, mixed using a ball mill, and calcined in an air atmosphere at 850 ° C. for 2 hours, and 0.03 wt. % SiO ₂ , 0.007 to 0.2 wt%
% Of CaO and 3.0 wt% of CuO were added, and then pulverized by a ball mill. After fine pulverization, a binder was added and granulated with a spray drier.
Formed into a 5 mm toroidal shape and placed in a reducing atmosphere
By sintering at 00 ° C., samples 3-1 to 3-5 were prepared.

As a conventional material 3, a sample having the same main component composition and additive amount without CuO was prepared in the same manner, and sintered at 1200 ° C. A winding was applied to the obtained core, and the core loss, average crystal grain size, and specific resistance were measured at 100 kHz to 2000 G. Table 3 shows the results.

[0039]

[Table 3]

According to Table 3, the content of CaO was 0.01 to 0.1 wt%.
It can be seen that the core loss of the added sample is smaller than that of the conventional material 3.

(Embodiment 4) The main component composition is 53.0.
mol% of _Fe 2 _O 3, _39.0mol% of MnO, and weighed so as to balance ZnO, a ball mill and mixed with, and calcined for 2 hours at 850 ° C. in an air atmosphere, as an auxiliary component, the SiO ₂ 0.03 wt%, CaO 0.05 wt%
% And CuO in an amount of 0.1 to 6.0 wt%, and then finely pulverized by a ball mill. After fine grinding, add a binder,
Granulate by spray dryer, φ30 × φ25 × 5m
m in a toroidal shape and 1200 in a reducing atmosphere.
Sintering was performed at ℃ to prepare Samples 4-1 to 4-6.

As a conventional material 4, a sample having the same main component composition and additive amount but no CuO was prepared by the same method, and sintered at 1200 ° C. Table 4 shows the results of measuring the core loss, average crystal grain size, and specific resistance at 100 kHz-2000 G-80 ° C. by applying a winding to the obtained core.

[0043]

[Table 4]

From Table 4, it can be seen that the core loss is smaller than that of the conventional material 4 in the sample in which CuO is added in an amount of 0.1 to 5.0 wt%.

(Embodiment 5) The main component composition is 53.0.
mol% of _Fe 2 _O 3, _39.0mol% of MnO, and weighed so as to balance ZnO, a ball mill and mixed with, and calcined for 2 hours at 850 ° C. in an air atmosphere, as an auxiliary component, the SiO ₂ 0.03 wt%, CaO 0.05 wt%
%, 3.0 wt% of CuO, and 0.005 to 3.0% of V ₂ O ₅ .
After adding 0 wt%, the mixture was finely pulverized with a ball mill. After pulverization, a binder was added, the mixture was granulated with a spray drier, formed into a toroidal shape of φ30 × φ25 × 5 mm, sintered at 1200 ° C. in a reducing atmosphere, and sample 5-
1 to 5-4 were produced.

Further, as the conventional material 5, a sample having the same main component composition and additive amount but without adding CuO and V ₂ O ₅ was prepared in the same manner, and sintered at 1200 ° C. A winding is applied to the obtained core, and 100 kHz-2000G-8
Table 5 shows the core loss at 0 ° C., the average crystal grain size, and the specific resistance.

[0047]

[Table 5]

From Table 5, it can be seen that the core loss is smaller than that of the conventional material when the addition amount is in the range of 0.01 to 2.0 wt%.

(Embodiment 6) The main component composition is 53.0.
mol% of _Fe 2 _O 3, _39.0mol% of MnO, and weighed so as to balance ZnO, a ball mill and mixed with, and calcined for 2 hours at 850 ° C. in an air atmosphere, as an auxiliary component, the SiO ₂ 0.03 wt%, CaO 0.05 wt%
%, 3.0 wt% of CuO and 0.003 to Nb ₂ O ₅ .
After adding 0.2 wt%, the mixture was finely pulverized with a ball mill. After pulverization, a binder was added, the mixture was granulated with a spray drier, formed into a toroidal shape of φ30 × φ25 × 5 mm, and sintered at 1200 ° C. in a reducing atmosphere to obtain samples 6-1 to 6-4. Produced.

Further, as the conventional material 6, CuO and Nb ₂ O ₅ were prepared in the same manner with the same main component composition and additive amount.
Was prepared and sintered at 1200 ° C. Winding is applied to the obtained core, and 100 kHz-2000G-
Table 6 shows the results of measuring the core loss at 80 ° C., the average crystal grain size, and the specific resistance.

[0051]

[Table 6]

From Table 6, it can be seen that the core loss is smaller than that of the conventional material 6 when the addition amount is in the range of 0.005 to 0.1 wt%.

(Embodiment 7) The main component composition is 53.0.
mol% of _Fe 2 _O 3, _39.0mol% of MnO, and weighed so as to balance ZnO, a ball mill and mixed with, and calcined for 2 hours at 850 ° C. in an air atmosphere, as an auxiliary component, the SiO ₂ 0.03 wt%, CaO 0.05 wt%
%, CuO at 3.0 wt%, and TiO ₂ at 0.003-0.00%.
After adding 6 wt%, the mixture was finely pulverized by a ball mill. After pulverization, a binder was added, the mixture was granulated with a spray dryer, formed into a toroidal shape of φ30 × φ25 × 5 mm, and sintered at 1200 ° C. in a reducing atmosphere to obtain a sample 7-
1 to 7-4 were produced.

As a conventional material 7, a sample having the same main component composition and additive amount but without adding CuO and TiO ₂ was prepared in the same manner, and sintered at 1200 ° C. A winding is applied to the obtained core, and 100 kHz-2000G-8
Table 7 shows the results of measuring the core loss, average crystal grain size, and specific resistance at 0 ° C.

[0055]

[Table 7]

Table 7 shows that the core loss is smaller than that of the conventional material when the amount of addition is in the range of 0.005 to 0.5 wt%.

The main component composition is 53.0 mol% of Fe ₂
O ₃ , 39.0 mol% of MnO and the balance ZnO were weighed and mixed using a ball mill, and calcined at 850 ° C. for 2 hours in an air atmosphere. As an auxiliary component, 0.03 wt% of SiO ₂ was added. CaO is 0.05 wt%, CuO is 3.
After adding 0 wt%, the mixture was finely pulverized with a ball mill. After fine pulverization, a binder is added, the mixture is granulated by a spray drier, formed into a toroidal shape of φ30 × φ25 × 5 mm, and is reduced to 1100, 1150, 120 in a reducing atmosphere.
Sintering was performed at 0.1250 ° C. to prepare Samples 8-1 to 8-5.

As a conventional material 8, a sample having the same main component composition and the same additive amount but without adding CuO was prepared by the same method, and sintered at 1250 ° C. Table 8 shows the results of measuring the core loss, average crystal grain size and specific resistance at 100 kHz-2000 G-80 ° C. by applying a winding to the obtained core.
Shown in

[0059]

[Table 8]

From Table 8, it can be seen that the core loss of the sample having an average crystal grain size of 5 to 10 μm is smaller than that of the conventional material 8.

[0061]

As described above, according to the present invention, a low-loss oxide magnetic material having a spinel-type crystal structure, a low sintering temperature and a small loss can be obtained. .

Claims (3)

[Claims] 1. Fe—Mn having a spinel-type crystal structure
The main component composition of the Zn-based ferrite is 52.5;
～53.5Mol% of _Fe 2 _O 3, _35.0~45.0m
% of MnO and the balance of ZnO, and 0.005 to 0.05 wt% of SiO ₂ , 0.01 as sub-components.
~ 0.1 wt% CaO and 0.2-5.0 wt% C
A low-loss oxide magnetic material comprising uO. 2. The low-loss oxide magnetic material according to claim 1, wherein 0.01 to 2.0 wt% of V ₂ O ₅ , 0.005 to 0.005%.
25 wt% Nb ₂ O ₅ , 0.005 to 0.5 wt% T
A low-loss oxide magnetic material comprising at least one of iO ₂ . 3. The low-loss oxide magnetic material according to claim 1, wherein the crystal grain size is 5 to 10 μm.