JP2002367821A - High-permeability oxide magnetic material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide oxide magnetic material which has both high initial permeability and high impedance characteristics at the same time. SOLUTION: This high-permeability oxide magnetic material contains 52.0 to 53.0 mol% Fe2 O3 , 19.0 to 23.5 mol% ZnO, and residual mol% MnO as main components and 0.005 to 0.025 wt.% SiO2 , 0.02 to 0.07 wt.% CaO, 0.01 to 0.03 wt.% Bi2 O3 , and 0.01 to 1.0 wt.% Gd2 O3 as auxiliary components.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a high-permeability oxide magnetic material, and more particularly, to a ferrite material for a noise filter.

[0002]

2. Description of the Related Art In recent years, there has been a remarkable technological innovation of miniaturization and high performance of electronic equipment. As a result, there has been a demand for high performance of Mn-Zn ferrite used, for example, high permeability and low loss. I have. Above all, a ferrite core for a noise filter is required to have high initial permeability and impedance.

[0003] Generally, the main component composition of Mn-Zn ferrite having a high initial magnetic permeability is 52.0 to 52.5 m.
_{o1% Fe 2 O 3, 24.0~28.0mol} % MnO, balance ZnO, which is a composition in the vicinity, even those that are currently commercially available, is approximately this range.

[0004] Mn-Zn ferrite contains SiO ₂ , CaO, Bi ₂ O _{3 and the} like as subcomponents. The initial magnetic permeability is a reversible change in magnetization, and is mostly magnetized by domain wall motion. The domain wall motion depends on the magnetic domain size and crystal magnetic anisotropy in the crystal, and the initial magnetic permeability increases by increasing the magnetic domain size or decreasing the crystal magnetic anisotropy.

[0005] Bi ₂ O ₃ is added for the purpose of accelerating grain growth, and is for obtaining a large crystal grain size necessary for obtaining a high initial magnetic permeability (the domain size in the crystal is: Depends on crystal grain size). SiO ₂ and CaO are added for the purpose of forming a high-resistance grain boundary layer to reduce eddy current loss which is a loss component of ferrite. Eddy current losses increase with increasing frequency,
In the high frequency range, the change in magnetization is suppressed by the magnetic field,
The initial permeability decreases. An effective means to prevent this is to increase the resistance of the material, thereby improving the frequency characteristics of the initial magnetic permeability in a high frequency range.

When the initial magnetic permeability maintains a high value up to the high frequency range, the peak value of the imaginary part appears on the high frequency side,
This also increases the impedance. In order to achieve high initial permeability and high impedance, it is necessary to examine the above composition and select an optimal composition.

Although Bi ₂ O ₃ is effective in promoting grain growth, it is also a factor that promotes abnormal grain growth. In order to obtain a high initial magnetic permeability only by increasing the crystal grain size, abnormal grains are generated. It will be easier. The abnormal grains increase the eddy current loss, reduce the specific resistance, and cause a significant reduction in impedance. Therefore, it is difficult to simultaneously achieve high initial permeability and high impedance characteristics.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to provide an oxide magnetic material which can solve the above-mentioned problems and can simultaneously realize high initial permeability and high impedance characteristics.

[0009]

As a result of various studies, the present inventor has found that the main component composition is 52.0-53.0 mol%.
Of Fe ₂ O _3, 19.0~23.5mol% of ZnO, the balance being MnO, 0.005~0.025w as a sub-component
t% SiO ₂ , 0.02 to 0.07 wt% CaO,
01～0.03Wt% of Bi ₂ O _3, 0.01~1.0wt
% Of Gd ₂ O ₃ was found to have high initial magnetic permeability and high impedance characteristics. Further, with the above composition, the average crystal grain size of the sintered body is 5-2.
It has been found that by setting the thickness to 0 μm, a high permeability oxide magnetic material having higher initial permeability and high impedance characteristics can be obtained.

According to the product of the present invention, a high initial magnetic permeability can be obtained by adding Gd ₂ O ₃ without depending on increasing the crystal grain size. As a result, high initial magnetic permeability and high impedance characteristics are simultaneously realized without reducing impedance. As described above, the initial magnetic permeability largely depends on the crystal grain size and the crystal magnetic anisotropy. Therefore, although the details are unknown, the initial magnetic permeability is increased by the addition of Gd with a constant crystal grain size, so that Gd ₂ O ₃ forms a solid solution in the spinel lattice of ferrite to reduce the crystal magnetic anisotropy. It is presumed that the initial permeability increased.

That is, in the present invention, the main component composition is 52.0 to
53.0Mol% of Fe ₂ O _3, 19.0~23.5mol
% Of ZnO and the balance of MnO.
0.5 to 0.025 wt% SiO ₂ , 0.02 to 0.07 w
t% of CaO, 0.01~0.03wt% of Bi ₂ O _3,
Is a high-permeability magnetic oxide which is characterized by containing Gd ₂ O ₃ of 0.01 to 1.0%.

Further, the present invention is the above-described high-permeability oxide magnetic material, wherein the sintered body has an average crystal grain size of 5 to 20 μm.

The main component composition is 52.0-53.0 mol% of Fe ₂ O ₃ , 19.0-23.5 mol% of ZnO, and the balance M
The reason for using nO is that if the content of Fe ₂ O ₃ is less than 52.0 mol%, a sufficient initial magnetic permeability cannot be obtained. Fe ₂ O ₃
Exceeds 53.0 mol%, a sufficient initial magnetic permeability cannot be obtained and the impedance is reduced. ZnO
If it is less than 19.0 mol%, a sufficient initial magnetic permeability cannot be obtained, and if it exceeds 23.5 mol%, the Curie temperature decreases and it becomes impractical.

The subcomponent is 0.005 to 0.025 wt% of S.
iO ₂ , 0.02 to 0.07 wt% CaO, 0.01 to
0.03 wt% Bi ₂ O ₃ , 0.01-1.0 wt% G
The reason for using d ₂ O ₃ is that if the content of SiO ₂ is less than 0.005 wt% and the content of CaO is less than 0.02 wt%, a high-resistance grain boundary layer cannot be obtained and a high impedance cannot be obtained. . SiO ₂ is more than 0.025 wt%,
If O exceeds 0.07 wt%, sufficient initial magnetic permeability cannot be obtained. If Bi ₂ O ₃ is less than 0.01 wt%, the effect of crystal grain growth cannot be obtained, and if it exceeds 0.03 wt%, eddy current loss increases due to generation of abnormal grains and the specific resistance and impedance are reduced. is there. Gd ₂ O ₃ is
If the content is less than 0.01 wt%, a sufficient effect of reducing the crystal magnetic anisotropy cannot be obtained. If the content exceeds 1.0 wt%, the solid solution is formed as an impurity in the crystal grains to lower the initial magnetic permeability.

The reason why the average crystal grain size is 5 to 20 μm is as follows.
If the average crystal grain size is less than 5 μm, sufficient initial magnetic permeability cannot be obtained, and if it exceeds 20 μm, eddy current loss increases, and specific resistance and impedance are reduced.

[0016]

Embodiments of the present invention will be described below.

(Embodiment 1) As an invention product, 22.5 mol% of Fe ₂ O ₃ of 52.5 mol% 1% as a main component composition
Of ZnO and the balance MnO, and 0.01 as a subcomponent.
0.03 wt% of Ca (OH) ₂ in terms of 5 wt% of SiO _2, CaO, 0.015wt% of Bi ₂ O _3, 0.1w
t% of Gd ₂ O ₃ was weighed and mixed for 2 hours using an attritor. After mixing, the mixture was granulated with a spray dryer.
Thereafter, each mixed powder was pre-fired in an atmosphere at 850 ° C. for 2 hours. The obtained powder was ground using an attritor. After crushing, granulate with a spray drier, 25mmφ-1
Press to 5mmφ-12mm toroidal shape, 13
The firing was performed at a firing temperature of 50 ° C. and a holding time of 2 hours.

Further, as a conventional product, the main component composition is 52.5 m.
o 1% Fe ₂ O ₃ , 22.5 mol% ZnO, balance M
composed of nO and 0.015 wt% of Si as a subcomponent
O ₂ , 0.03 wt% CaO, 0.015 wt% Bi ₂ O
Mn-Zn ferrite containing ₃ was produced in a similar process.

Table 1 shows the average grain size of the invention product and the conventional product,
Specific resistance, Curie temperature (Tc), 10 kHz and 100
The initial permeability (μ) at kHz and the maximum value (Zmax) of the impedance when the number of turns is 10 Turn are shown.

[0020]

[Table 1]

From Table 1, it can be seen that the invention product has a μ, Z
It can be seen that max and specific resistance are high.

FIG. 1 shows the frequency characteristics of the initial magnetic permeability of the invention product and the conventional product. From FIG. 1, it can be seen that the invention product maintains a high initial magnetic permeability up to high frequencies.

(Embodiment 2) 51.
0-54.0mo1% Fe_TwoO_Three, 18.0-25.0m
ol% of ZnO and the balance of MnO, as sub-components
0.015 wt% SiO_Two0.03 in terms of CaO
wt% Ca (OH)_Two, 0.015 wt% Bi_TwoO _Three,
0.1 wt% Gd_TwoO_ThreeWeigh and use an attritor
And mixed for 2 hours. After mixing, make with a spray dryer
Granulated. Then, each mixed powder was placed in the air at 850 ° C for 2 hours.
Baked for a while. Grind the obtained powder using an attritor
did. After crushing, granulate with a spray drier, 25m
Press into toroidal shape of mφ-15mmφ-12mm
And fired at a firing temperature of 1350 ° C. and a holding time of 2 hours.
Was.

Table 2 shows the average crystal grain size, specific resistance, Tc, μ at 100 kHz, and the number of turns of 10 Tur of the present embodiment.
Zmax of n is shown.

[0025]

[Table 2]

From Table 2, it is found that 52.0 to 53.0 mol% of F
e ₂ O ₃ and samples (invention product 2-5) are conventional (Table 1)
It can be seen that μ and Zmax are higher as compared with. 1
Sample containing 9.0 to 23.5 mol% of ZnO (Invention 6
9) show that Tc, μ, and Zmax are high.

(Embodiment 3) 52.
2Mo1% of Fe ₂ O _3, 22.0mol% of ZnO, the balance MnO, of 0.01～0.08Wt% in terms of SiO _2, CaO of 0～0.03Wt% as an auxiliary component Ca (OH ) ₂ , 0.015 wt% Bi ₂ O ₃ , 0.1 w
t% of Gd ₂ O ₃ was weighed and mixed for 2 hours using an attritor. After mixing, the mixture was granulated with a spray dryer.
Thereafter, each mixed powder was pre-fired in an atmosphere at 850 ° C. for 2 hours. The obtained powder was ground using an attritor. After crushing, granulate with a spray drier, 25mmφ-1
Press to 5mmφ-12mm toroidal shape, 13
The firing was performed at a firing temperature of 50 ° C. and a holding time of 2 hours.

Table 3 shows the average crystal grain size, specific resistance, Tc, μ at 100 kHz, and the number of turns of 10 Tur of the present embodiment.
Zmax of n is shown.

[0029]

[Table 3]

From Table 3, it can be seen that the samples containing 0.005 to 0.025 wt% of SiO ₂ and 0.02 to 0.07 wt% of CaO (Invention products 10 to 16) have high μ and Zmax.

(Embodiment 4) 52.
It consists of ₂ mol% of Fe ₂ O ₃ , 22.0 mol% of ZnO and the balance MnO, and 0.015 wt% of S as a sub-component.
0.03 wt% of Ca (OH) in terms of iO ₂ and CaO
₂ , 0.005 to 0.035 wt% Bi ₂ O ₃ , 0.005
Ｄ1.2 wt% of Gd ₂ O ₃ was weighed and mixed for 2 hours using an attritor. After mixing, the mixture was granulated with a spray dryer. Then, each mixed powder was placed in an atmosphere at 850 ° C. for 2 hours.
Pre-baked for hours. The obtained powder was ground using an attritor. After crushing, granulate with a spray drier, 25
It was pressed into a toroidal shape of mmφ-15 mmφ-12 mm and fired at a firing temperature of 1350 ° C. and a holding time of 2 hr.

Table 4 shows the average crystal grain size, specific resistance, Tc, μ at 100 kHz, and the number of turns of 10 Tur of the present embodiment.
Zmax of n is shown.

[0033]

[Table 4]

According to Table 4, 0.01 to 0.03 wt% Bi
_TwoO_Three, 0.01 to 1.0 wt% Gd _TwoO_ThreeSample
Clear products 17 to 24) have high μ and Zmax.
You.

(Embodiment 5) 52.
It consists of ₂ mol% of Fe ₂ O ₃ , 22.0 mol% of ZnO and the balance MnO, and 0.015 wt% of S as a sub-component.
0.03 wt% of Ca (OH) in terms of iO ₂ and CaO
₂ , 0.015 wt% Bi ₂ O ₃ , 0.1 wt% Gd ₂ O
₃ was weighed and mixed using an attritor for 2 hours. After mixing, the mixture was granulated with a spray dryer. Thereafter, each mixed powder was pre-fired in an atmosphere at 850 ° C. for 2 hours. The obtained powder was ground using an attritor. After pulverization, granulate with a spray drier, 25mmφ-15mmφ-1
Pressed into 2mm toroidal shape, 1280-140
The firing was performed at a firing temperature of 0 ° C. and a holding time of 2 hours.

Table 5 shows the average crystal grain size, specific resistance, Tc, μ at 100 kHz, and the number of turns of 10 Tur of this embodiment.
Zmax of n is shown.

[0037]

[Table 5]

Table 5 shows that the samples having an average crystal grain size of 5 to 20 μm (Invention products 25 to 27) have a high μ without reducing the specific resistance and Zmax.

[0039]

As described above, according to the present invention,
An oxide magnetic material capable of simultaneously realizing high initial permeability and high impedance characteristics was provided.

[Brief description of the drawings]

FIG. 1 is a diagram showing frequency characteristics of initial permeability of an invention product to which Gd ₂ O ₃ is added and a conventional product.

[Explanation of symbols]

 A Invented product B Conventional product

Claims (2)

[Claims] 1. The main component composition is 52.0 to 53.0 mol%.
Of Fe ₂ O _3, 19.0~23.5mol% of ZnO, the balance being MnO, 0.005~0.025w as a sub-component
t% SiO ₂ , 0.02 to 0.07 wt% CaO,
01～0.03Wt% of Bi ₂ O _3, 0.01~1.0wt
% Of Gd ₂ O ₃ . 2. The high-permeability oxide magnetic material according to claim 1, wherein the average crystal grain size of the sintered body is 5 to 20 μm.