JPH06325920A - Low-loss magnetic material and manufacture thereof - Google Patents

Abstract

PURPOSE:To reduce the loss of an eddy current by a method wherein Cao and SiO2 are made to solubilize in a specified ratio in the crystal grains of a spinel type Mn-Zn ferrite as the subcomponents of the ferrite. CONSTITUTION:A spinal type Mn-Zn ferrite contains 30 to 42mol% of MnO and 4 to 19 mol % of ZnO with the remnant of Fe2O3 as its main components and contains CaO and SiO2 as its subcomponents. At least one kind of a compound out of these subcomponents is a low-loss magnetic material being solid solubilized in spinel crystal grains. Thereby, the loss of the Mn-Zn ferrite is a loss lower than that of a conventional Mn-Zn ferrite and the Mn-Zn ferrite, which shows a superior performance as the material for a transformer of a switching power supply or the like, can be obtained.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a low loss material,
More specifically, the present invention relates to a spinel type Mn—Zn-based ferrite used for a main transformer of a switching power supply, a smooth choke, a power supply transformer material, and the like, and a manufacturing method thereof.

[0002]

2. Description of the Related Art Conventionally, switching power supplies, transformer materials for power supplies, etc. having a drive frequency of about 200 kHz have been used.

In recent years, the progress of high performance and miniaturization of various electronic devices has been remarkable, and accordingly, further higher performance and miniaturization of switching power supplies, transformer materials for power supplies, etc. are desired.

Therefore, Mn-Zn used for a main transformer, a smooth choke, etc. and a power transformer material.
It is desired to further reduce the loss of the system ferrite. In order to reduce the size and weight of the product, consideration is being given to increasing the switching frequency and drive frequency in various fields, and power supplies of about 1 MHz are now being commercialized.

Here, spinel type Mn-Zn ferrite used for a power transformer material or the like is generally prepared by mixing, pre-firing, pulverizing, granulating, shaping and firing the spinel type Mn-Zn ferrite. Manufactured by the powder metallurgy method, and the density of the sintered body is 4.75 to 4.8 at most.
It is about 5 gr / cm ³ .

[0006]

However, when the conventional spinel type Mn-Zn type ferrite is used at a high frequency such as 1 MHz, the heat generation due to the power loss of the ferrite is remarkable and the function cannot be effectively achieved. Had.

In the above-mentioned conventional powder metallurgy method, the powder particle size is controlled by crushing after pre-firing, and the density and structure of the sintered body are controlled by the balance with the firing atmosphere and temperature. As a means for improving the density, there are methods such as making the powder particle size fine and increasing the holding temperature during firing, but both of them not only significantly deteriorate the magnetic properties due to abnormal grain growth but It has a drawback that it becomes long and the consumption of the crusher and the media becomes remarkable. Furthermore, the latter is not preferable because the firing furnace imposes a great burden, the life of the furnace becomes short, and the cost is high.

The spinel type Mn-
Zn ferrite itself has a density of about 5.2 gr / cm ^3, but at present, it has not been achieved by a general powder metallurgy method to improve the density of the sintered body to that extent. Therefore, the initial permeability (μ _i ) and the saturation magnetic flux density (Bs) are low, and the core loss value is not sufficient.
The excellent magnetic properties of the n-Zn ferrite could not be utilized.

Therefore, the technical problem of the present invention is that spinel type Mn-
This was done in response to the desire to reduce the loss of Zn-based ferrite. By eliminating the drawbacks of the prior art, power loss is small and heat is effectively generated even in the high frequency band from about 100 kHz to about 1 MHz. An object is to provide a suppressed low loss magnetic material and a method for manufacturing the same.

[0010]

[Means for Solving the Problems] Generally, spinel type Mn
-CaO contained as an accessory component in the Zn-based ferrite,
SiO ₂ is said to form a grain boundary phase at the grain boundary.
As a result of various investigations, the present inventors have solved the above-mentioned problems by making CaO and SiO ₂ which are subcomponents solid-solved not only in the grain boundary phase but also in the crystal grains in a specific ratio. It was discovered that spinel type Mn-Zn based ferrite with even lower loss can be obtained.

According to the present invention, the main component is 30 to 42.
In a spinel-type Mn—Zn-based ferrite containing mol% MnO, 4 to 19 mol% ZnO and the balance Fe ₂ O ₃ , and CaO and SiO ₂ as subcomponents, at least one of the subcomponents is spinel crystal. A low-loss magnetic material characterized by being solid-dissolved in grains can be obtained.

According to the present invention, in the low loss magnetic material, when the amount of the sub-component dissolved as solid solution is CaO,
Within the range of 10 to 70% of the total CaO content, SiO
_In the case of ₂ , a low loss magnetic material characterized by being in the range of 10 to 60% of the total SiO ₂ content is obtained.

That is, according to the present invention, spinel type Mn-
10 to 70% of the total CaO content of CaO, which is contained as a sub-component in an amount of 1.0 wt% or less, and SiO ₂ which is contained as a sub-component of 1.0 wt% or less, in SiO _{2
2 In} the range of 10 to 60% of the total content, by solid-dissolving in spinel crystal particles, the core loss characteristics can be improved and high performance of the switching power supply can be realized.

Currently, for spinel type Mn-Zn ferrite materials, a core loss value of 450 kW / m ³ or less is required in a low frequency region of about 100 kHz, and a core loss value of about 1 MHz is required. , 50
A core loss value of 0 kW / m ³ or less is required. Therefore, in the present invention, these CaO and SiO, which are subordinate components, are used.
_The solid loss of 2 in a specific ratio not only in the grain boundary phase, but in the crystal grains, improved the core loss characteristics so as to satisfy the above requirements. By firing in a controlled atmosphere, SiO ₂ ,
A specific amount of CaO can be dissolved in the grains, and the difference in the degree of oxidation between the ferrite grain boundary phase and the main phase crystal can be reduced. This is probably because the degree of oxidation was made uniform, the resistivity of the grain boundary phase and main phase crystals inside the sintered body were both improved, and the eddy current loss was mainly reduced.

Further, as a result of further investigations, the present inventors have made Nb ₂ O ₅ as a subcomponent a solid solution not only in the grain boundary phase but also in the crystal grains in a specific ratio to further lower the content. It was discovered that lossy spinel type Mn-Zn ferrite can be obtained.

According to the present invention, there is provided a low loss magnetic material characterized by further containing 0 to 0.08% by weight (not including 0) of Nb ₂ O ₅ as an auxiliary component in the low loss magnetic material. can get.

According to the present invention, in the low loss magnetic material, Nb ₂ O ₅ is solid-dissolved in the spinel crystal grains in the range of 20 to 70% of the total weight of Nb ₂ O _5. A low loss magnetic material that can be obtained

That is, in the present invention, Nb ₂ O ₅ is added to Nb
By making a solid solution in the spinel crystal particles in the range of 20 to 70% of the total ₂ O ₅ content, the core loss characteristics can be improved and the performance of the power transformer material can be improved.

Here, in the present invention, the core loss characteristics can be improved by solid-solving these Nb ₂ O ₅ sub-components not only in the grain boundary phase but also in the crystal grains in a specific ratio. By firing in an atmosphere in which the oxygen partial pressure is controlled appropriately, Nb ₂ O ₅ can be dissolved in the crystal grains in a specific ratio, and the difference in the degree of oxidation between the ferrite grain boundary phase and the main phase crystal can be reduced. As a result, the degree of oxidation of the crystal grains and the grain boundary phase of the sintered body can be made uniform, and the resistivity of the grain boundary phase and the main phase crystal inside the sintered body are both improved, mainly It seems that the eddy current loss decreased.

Further, according to the present invention, it is possible to reduce the influence of magnetic strain caused by the difference in internal stress between the grain boundary phase inside the sintered body and the main phase crystal, and it is possible to obtain high magnetic permeability.

Further, the present inventors set the density of the sintered body to 4.9.
It has been found that the ferrite core can have excellent magnetic characteristics originally possessed by Mn-Zn ferrite by setting g / cm ³ or more. Furthermore, Nb
_{By including 2} O ₅ as a sub-component of 0.08 wt% or less (not including 0), the magnetic properties can be remarkably improved, and the temperature rising atmosphere in the sintering step is N ₂ .
The inventors have found that the density of the sintered body is remarkably improved and excellent magnetic properties can be obtained.

According to the present invention, the main component is 30 to 42.
Mol% of MnO, in spinel Mn-Zn ferrite sintered body containing Fe ₂ O ₃ as ZnO, and the balance of 4 to 19 mol%, the sintered body density of at least 4.9 g / c
A low loss magnetic material characterized by having m ³ is obtained.

Further, according to the present invention, in the low loss magnetic material, the sintered body contains 0% Nb ₂ O ₅ as an accessory component.
A low loss magnetic material characterized by containing 0.08 wt% (not including 0) is obtained.

According to the present invention, there is obtained a method for producing a spinel type Mn-Zn ferrite sintered body, which comprises firing while raising the temperature in a nitrogen atmosphere. To be

Here, in the present invention, the reason why the density is improved by raising the temperature in a nitrogen (N ₂ ) atmosphere and the magnetic properties are remarkably improved is not clear, but the spinel reaction is not clear. It is considered that the grain growth and the densification proceeded under the condition that the grain size was further promoted, so that the density was improved and the structure was homogenized.

Further, in the present invention, Nb ₂ O ₅ not only reduces the eddy current loss by precipitating at the grain boundaries to increase the electric resistance, but also controls Bs,
It has the effect of improving the magnetic characteristics such as μ _i . Here, in the present invention, the amount of Nb ₂ O ₅ is set to 0.08 wt% or less because a magnetic property deterioration factor such as abnormal grain growth occurs in a region exceeding 0.08 wt%. By setting the density of the sintered body to 4.9 g / cm ³ or more by the above method, the magnetic characteristics are remarkably improved, and it becomes possible to supply an excellent material as a power transformer material. In the present invention, the cost is not significantly increased, and it is advantageous that the magnetic properties can be remarkably improved only by slightly changing the current process.

[0027]

EXAMPLES Examples of the low loss magnetic material according to the present invention will be described below.

Example 1 High-purity Fe ₂ O ₃ and Mn ₃
O ₄ and ZnO powder are mixed with 53 mol% Fe ₂
O ₃ , 35 mol% MnO, 12 mol% ZnO were weighed and mixed with a ball mill,
It was calcined at about 900 ° C.

Next, 0.02% by weight (wt.
%) SiO ₂ and 0.05 wt% CaO were added, and further mixed and crushed by a ball mill. Then, after mixing the obtained powder with a binder, about 2 tons / cm ²
And the resulting molded body is fired at a firing temperature of 1000.
Firing was performed in an atmosphere of ˜1400 ° C. and oxygen partial pressure: 1-10%.

FIG. 1 shows each sample obtained when the amount of CaO in the main phase crystal grains was changed in the sample in which the SiO ₂ content in the main phase crystal grains was 30% of the total SiO ₂ content. At 100 ° C., frequency (f =) 100 kHz-maximum magnetic flux density (B _m =) 2000 G, power loss (P _B ) value and initial magnetic permeability (μ _i ) value at room temperature are shown in FIG. In the sample in which the CaO content in the sample is 30% of the total CaO content, 100 ° C. and 100 kHz−2 of each sample obtained when the amount of SiO ₂ in the main phase crystal grains was changed
The P _{B at} 000 _G and the μ _i value at room temperature are shown.

CaO, S in the main phase crystal grains of FIGS. 1 and 2
The iO ₂ content is the ratio (%) of the content in the main phase crystal grains from which the grain boundary phase is removed by chemical etching to the total content.
It is the value shown in.

From FIG. 1 and FIG. 2, CaO is in the range of 10 to 70% of the total CaO content, and SiO ₂ is in the range of 10 to 60% of the total SiO ₂ content. It can be seen that the compacted sample has a small core loss value and high magnetic permeability.

Example 2 High-purity Fe ₂ O ₃ and Mn ₃
O ₄ and ZnO powder were mixed with 53 mol% of Fe ₂ O ₃ and 39
Weigh it so that it is mol% MnO, 8 mol% ZnO,
These powders were mixed in a ball mill and then calcined at about 900 ° C. Next, 0.03 wt% of Si was added to the calcined powder.
O ₂ and 0.10 wt% CaO were added, and further mixed and crushed with a ball mill. Next, after mixing the obtained powder with a binder, it is molded at about 2 ton / cm ² ,
Baking temperature of these obtained molded bodies: 1000 to 1250
Firing was carried out in an atmosphere of ° C and oxygen partial pressure of 0.1 to 6%.

FIG. 3 shows the samples obtained when the amount of CaO in the main phase crystal grains was changed in the sample in which the SiO ₂ content in the main phase crystal grains was 30% of the total SiO ₂ content. P _B at 60 ° C., f = 1 MHz, B _m = 500 G
Fig. 4 shows the values, and Fig. 4 shows that the CaO content in the main phase grains is C
60% of each sample obtained when the amount of SiO ₂ in the main phase crystal grains was changed in the sample containing 30% of the total content of aO.
The P _B value at ° C, f = 1 MHz, and B _m = 500 G is shown.

CaO and S in the main phase crystal grains of FIGS.
The amount of iO ₂ is a value in which the content in the main phase crystal grains from which the grain boundary phase has been removed by chemical etching is expressed as a ratio (%) to the total content.

From FIG. 3 and FIG. 4, CaO in the range of 10 to 70% of the total content of CaO and SiO ₂ in the range of 10 to 60% of the total content of SiO ₂ are dissolved in the spinel crystal grains. It can be seen that a low core loss value was obtained for the aged sample.

(Example 3) High-purity Fe ₂ O ₃ and Mn ₃
O ₄ and ZnO powder were mixed with 53 mol% of Fe ₂ O ₃ and 35
Weighed so as to be mol% MnO and 12 mol% ZnO, mixed these powders in a ball mill, and then measured about 900
It was calcined at ℃.

Next, 0.02 wt% of Si was added to the calcined powder.
O ₂ , 0.05 wt% CaO and 0.04 wt% N
b ₂ O ₅ was added, and further mixed and crushed with a ball mill. Next, after mixing the obtained powder with a binder,
Molded at about 2 ton / cm ²
Firing temperature: 1100 to 1400 ° C, oxygen partial pressure: 1 to 10
% In the atmosphere.

FIG. 5 shows each sample obtained when the amount of Nb ₂ O ₅ in the main phase crystal grains was changed at 100 ° C. and f = 100 k.
The P _B value at Hz and B _m = 2000 G and the μ _i value at room temperature are shown. In addition, N in the main phase crystal grains in FIG.
The amount of b ₂ O ₅ is the content of the content in the main phase crystal grains from which the grain boundary phase has been removed by chemical etching, as a ratio (%) to the total content.

According to FIG. 5, the total content of Nb ₂ O ₅ is 20 to 7
It can be seen that in the range of 0%, the sample in which Nb ₂ O ₅ is solid-solved in the spinel crystal grains has a low core loss value. (Example 4) High purity _{Fe 2 O 3, Mn 3 O} 4, ZnO
Powder of 53 mol% Fe ₂ O ₃ and 39 mol% Mn
O and ZnO of 8 mol% were weighed, and these powders were mixed in a ball mill and calcined at about 900 ° C. Next, 0.03 wt% of SiO ₂ , 0.1
0 wt% CaO and 0.04 wt% Nb ₂ O ₅ were added, and further mixed and crushed by a ball mill. Next, the obtained powder is mixed with a binder and then molded at about 2 ton / cm ² , and the obtained molded body is fired at a firing temperature:
It was fired in an atmosphere of 1100 to 1400 ° C. and an oxygen partial pressure of 3% or less.

FIG. 6 shows 60 ° C., 1 kHz-of each sample obtained when the Nb ₂ O ₅ content in the main phase crystal grains was changed.
The P _B value at 500 G is shown. The amount of Nb ₂ O ₅ in the main phase crystal grains in FIG. 6 is the content of the main phase crystal grains in which the grain boundary phase has been removed by chemical etching as a ratio (%) to the total content. is there.

From FIG. 6, the total content of Nb ₂ O ₅ is 20 to 7
It can be seen that in the range of 0%, the sample in which Nb ₂ O ₅ is solid-solved in the spinel crystal grains has a low core loss value.

(Fifth Embodiment) In the same process as in the first embodiment, N
A sample was prepared by adding b ₂ O ₅ varying from 0 to 0.10 wt%. FIG. 7 shows the relationship between the Nb ₂ O ₅ content of this sample, the P _B value at 100 ° C. and 100 kHz-2000 G, and the μ _i value at room temperature.

From FIG. 7, the Nb ₂ O ₅ content was 0 to 0.
It can be seen that excellent magnetic characteristics are obtained when the content is 08 wt% (excluding 0%).

Example 6 High-purity Fe ₂ O ₃ and Mn ₃
52.5Fe ₂ O ₃ -35 by blending O ₄ and ZnO raw materials
It was set to be MnO-12.5ZnO (mol%).
Next, the compounded powder was mixed in a ball mill, pre-fired, pulverized again in the ball mill, mixed with a bander, and then molded. Then, the obtained molded body was changed in the temperature rising atmosphere, temperature and holding conditions to obtain a fired body. Table 1 below shows the sintered body density and the obtained magnetic characteristics. Sintered body density is 4.9g / c
It can be seen that all the magnetic properties are excellent in the samples of m ³ or more.

[0046]

[Table 1]

Example 7 The powder compact obtained in Example 1 was fired at a temperature rise in N _{2 and a} temperature rise in the atmosphere. Hold 130
The temperature was 0 ° C., and the atmosphere was a mixed gas of N ₂ and O ₂ . Table 2 below shows the magnetic characteristics of the materials in which the temperature rising part is in an N ₂ atmosphere and an air (air) atmosphere. Excellent magnetic properties are exhibited when the temperature rising portion is set to N ₂ .

[0048]

[Table 2]

(Embodiment 8) In the same process as in Embodiment 1, N
A sample was prepared by adding b ₂ O ₅ varying from 0 to 0.1 wt%.

Table 3 below shows the magnetic characteristics when the amount of Nb ₂ O ₅ was changed. When Nb ₂ O ₅ or 0.08 wt% or less (not including 0), excellent magnetic properties are exhibited.

[0051]

[Table 3]

[0052]

As described above, according to the present invention, M
In a method for producing an n-Zn ferrite by an ordinary powder metallurgy method, calcium oxide and silicon dioxide, which are subcomponents, are contained in calcium oxide in a total content of 1 of calcium oxide.
By making 0 to 70% and 10 to 60% of the total content of silicon dioxide in silicon dioxide into solid solution in spinel crystal grains respectively, the loss is lower than that of the conventional Mn-Zn type ferrite, and it can be used in switching power supplies. It is possible to obtain Mn—Zn based ferrite exhibiting excellent performance as a transformer material.

Further, according to the present invention, in the method for producing Mn-Zn-based ferrite by the usual powder metallurgy method, the auxiliary component Nb ₂ O ₅ is in the range of 0 to 0.08 wt% (excluding 0%). In addition, Nb ₂ O ₅ is contained in the spinel crystal grains as a solid solution in an amount of 20 to 70% of the total content of Nb ₂ O ₅ , so that the power loss is lower than that of conventional Mn-Zn ferrite. It is possible to provide a Mn-Zn-based ferrite exhibiting excellent performance as a transformer material.

Furthermore, according to the present invention, the density of the sintered body is 4.
When it is 9 g / cm ³ or more, the magnetic characteristics are remarkably improved. At this time, 0.08 wt% of Nb ₂ O ₅ was added.
The density can be increased to 4.9 g / cm ³ or more by using the following (not including 0) and using a firing pattern of raising the temperature in N ₂ . This has a density of 4.9g
/ Cm ³ or more because it is possible to secure the excellent magnetic properties originally possessed by Mn-Zn ferrite,
It is considered that the temperature increase in N ₂ contributes to the improvement of the characteristics by the progress of grain growth and densification under the condition that the spinelization reaction is further promoted.

[Brief description of drawings]

FIG. 1 shows Si in a main phase crystal grain in Example 1 of the present invention.
In a sample having an O ₂ content of 30% of the total SiO ₂ content, the CaO content in the main phase crystal grains and 100 ° C., f = 10
0 kHz, power loss value and the ambient temperature at B _m = 2000 G, is a diagram showing the relationship between the mu _i value at f = 100kHz.

FIG. 2 Ca in the main phase crystal grains in Example 1 of the present invention
In the sample in which the O content is 30% of the total CaO content, the SiO ₂ content in the main phase crystal grains and 100 ° C., f = 100
kHz, power loss value and the ambient temperature at B _m = 2000 G, is a diagram showing the relationship between the mu _i value at f = 100kHz.

FIG. 3 Si in the main phase crystal grains in Example 2 of the present invention
The amount of CaO in the main phase crystal grains and 60 ° C., f = 1 MH in the sample in which the O ₂ content is 30% of the total SiO ₂ content
z, it is a diagram showing the relationship between the power loss value of B _m = 500G.

FIG. 4 Ca in the main phase crystal grains in Example 2 of the present invention
In the sample in which the O content is 30% of the total CaO content, the amount of SiO ₂ in the main phase crystal grains and 60 ° C., f = 1 MH
z, it is a diagram showing the relationship between the power loss value of B _m = 500G.

FIG. 5: Nb in crystal grains of main phase in Example 3 of the present invention
₂ O ₅ amount and 100 ° C., f = 100 kHz, B _m = 200
Power loss value at 0G and room temperature, f = 100kHz
FIG. 6 is a diagram showing a relationship with μ _i in FIG.

FIG. 6 is an Nb in a main phase crystal grain in Example 4 of the present invention.
₂ O ₅ amount and 60 ° C., a diagram showing the relationship between the power loss value at _{f = 1MHz, B m = 500G} .

FIG. 7 is a graph showing the Nb ₂ O ₅ content in Example 5 of the present invention, the power loss value at 100 ° C., f = 100 kHz, B _m = 2000 G, and μ at room temperature, f = 100 kHz.
It is a figure which shows the relationship with _i .

Claims (8)

[Claims] 1. Mn of 30 to 42 mol% as a main component
O, 4 to 19 mol% ZnO and the balance Fe ₂ O ₃
In a spinel-type Mn—Zn-based ferrite containing CaO and SiO ₂ as a minor component, at least one of the minor components is a solid solution in the spinel crystal grains. 2. The low loss magnetic material according to claim 1, further comprising Nb ₂ O ₅ as an accessory component in an amount of 0 to 0.08% by weight.
A low loss magnetic material containing (not including 0). 3. The low-loss magnetic material according to claim 1 or 2, wherein the amount of the sub-component dissolved as a solid solution is in the range of 10 to 70% of the total CaO content in the case of CaO.
In the case of iO ₂ , a low loss magnetic material characterized by being in the range of 10 to 60% of the total SiO ₂ content. 4. The low loss magnetic material according to claim 2 or 3, wherein Nb ₂ O ₅ is solid-dissolved in the spinel crystal grains within a range of 20 to 70% of the total weight of Nb ₂ O _5. Characteristic low loss magnetic material. 5. A method for producing a spinel type Mn—Zn ferrite sintered body, which comprises firing in an atmosphere having an oxygen partial pressure of 10% or less. 6. Mn of 30 to 42 mol% as a main component
O, 4 to 19 mol% ZnO and the balance Fe ₂ O ₃
A spinel-type Mn-Zn-based ferrite sintered body containing, a low-loss magnetic material having a sintered body density of at least 4.9 g / cm ³ . 7. The low loss magnetic material according to claim 6, wherein the sintered body contains Nb ₂ O ₅ in an amount of 0 to 0.0.
A low loss magnetic material containing 8% by weight (not including 0). 8. A method for producing a spinel type Mn—Zn ferrite sintered body, which comprises firing while raising the temperature in a nitrogen atmosphere, and a method for producing a low loss magnetic material.