JP2002187769A - Ferrite material and ferrite core using the same - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To provide a ferrite material which simultaneously realizes a high Bs value and a high magnetic permeability. An oxide having a spinel structure containing Fe as a main component and at least one of Zn, Ni, and Cu as a main component,
A ferrite material in which the content of an oxide containing at least one of Zn, Ni, and Cu as a main component is less than 0.01% by volume.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a ferrite material. In particular, the present invention proposes a ferrite material exhibiting a high saturation magnetic flux density and a high magnetic permeability, and a ferrite core using the same.

[0002]

2. Description of the Related Art Ferrite materials are widely used as cores for inductors, transformers, ballasts, electromagnets, noise reduction, and the like. In particular, in recent years, with the progress of miniaturization and thinning of battery-powered portable devices such as mobile phones and notebook personal computers, the demand for smaller and thinner power supplies required for these portable devices has been increasing. Therefore, the inductor
It is also difficult to flow a large current due to the downsizing of the application core, and a ferrite material capable of flowing a large current even with a small volume is required, and a ferrite material having a high saturation magnetic flux density is desired.

That is, when a ferrite material is formed into a core shape and a winding is formed into a coil, the larger the current applied to the winding, the larger the magnetic flux density that occurs. There is a characteristic that does not become. The magnetic flux density at this time is a saturation magnetic flux density (hereinafter referred to as Bs value). If a current in a range exceeding this Bs value is passed, inconveniences such as heat generation will occur. Therefore, a higher current can flow as the Bs value increases.

In addition, there is an increasing demand for higher inductance of components required for these portable devices. Therefore, a ferrite material having a large inductance is required even when the size is reduced, and a ferrite material having a high magnetic permeability, which is a material characteristic of the inductance, is desired.

[0005]

However, it is said that a commonly used ferrite material cannot achieve both a high Bs value and a high magnetic permeability.

On the other hand, it has been proposed to improve the characteristics by adding various additives to a ferrite material. According to Japanese Patent Application Laid-Open No. 6-295811, Fe ₂ O ₃ , MgO, NiO, CuO and ZnO are mainly used. It is shown that the Bs value is increased by adding MoO ₃ to the ferrite material used as a component.

[0007] However, none of these methods satisfy the above-mentioned problems of high Bs value and high magnetic permeability.

Therefore, an object of the present invention is to obtain a ferrite material having a high Bs value and a high magnetic permeability at the same time.

[0009]

The ferrite material of the present invention is mainly composed of an oxide having a spinel structure containing Fe as a main component and at least one of Zn, Ni and Cu, and at least one of Zn, Ni and Cu. Oxide composed mainly of one kind
It is characterized by being less than 0.01% by volume.

[0010] The ferrite material of the present invention may be composed of Zn, Ni.
Or 90 of an oxide containing at least one of Cu as a main component
It is characterized in that at least% by volume consists of crystal grains.

Further, the present invention is characterized in that the ferrite material has an average crystal grain size of 1 to 50 μm and a sintered density of 5.0 g / cm ³ or more.

[0012] Further, the present invention relates to the above-mentioned ferrite material,
The oxides of e, Zn, Ni, Cu and Mn are Fe ₂ O ₃ , ZnO, N
iO, Fe ₂ O ₃ is 48 to 50 mol% CuO and MnO terms, CuO 5 mol
% Or less, MnO is contained in the range of 0.01 to 1 mol%, and ZnO / Ni
It is characterized in that the molar ratio of O is 0.5 to 1.6.

Further, the ferrite material of the present invention further comprises Zr
Or Y oxide, converted to ZrO ₂ or Y ₂ O ₃ respectively,
and rO ₂ is 0.001 to 0.1 parts by weight, Y ₂ O ₃ is characterized in that it contains 0.001 to 0.1 parts by weight.

Further, a ferrite core according to the present invention is characterized in that the ferrite core is formed into a predetermined shape with the above ferrite material.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The ferrite material of the present invention is mainly composed of an oxide having a spinel structure containing Fe as a main component and at least one of Zn, Ni and Cu, and is composed of Zn, Ni or Cu.
The content of the oxide containing at least one of the main components
By setting the content to less than 0.01% by volume, a high Bs value and a high magnetic permeability are simultaneously realized.

Generally, a ferrite material containing Fe as a main component and containing Zn, Ni or Cu is mainly composed of an oxide having a spinel structure containing Fe as a main component. Oxides are present. Then, the oxide containing at least one of Zn, Ni and Cu as a main component exhibits weak magnetic or non-magnetic properties, lowering the overall magnetic properties,
In order to reduce the magnetic permeability and the Bs value, the content of the ferrite material of the present invention was reduced. The content of the oxide not containing Fe as a main component and containing at least one of Zn, Ni, and Cu as a main component is less than 0.01% by volume in the present invention by analyzing a small region of the ferrite material. I found out what to do.

Further, the ferrite material of the present invention comprises the Zn,
An oxide containing at least one of Ni and Cu as the main component
Even if present in a range of less than 0.01% by volume, it is preferable that 90% by volume or more of the particles are crystal particles. This is because the crystallization of the oxide increases the magnetism of the oxide itself, so that the Bs value and the magnetic permeability of the ferrite material can be further increased.

The ferrite material of the present invention contains
The content of the oxide containing at least one of Zn, Ni and Cu as a main component is measured, for example, as follows. While observing the sintered ferrite material with a scanning electron microscope (SEM),
Fe, Z by wavelength dispersive X-ray microanalyzer (WDS)
The distribution of each element of n, Ni and Cu is measured. The measurement conditions at this time were: acceleration voltage of about 15 kV, probe current of about 2 × 10 ^-7 A,
The analysis area is about 10 ³ μm ² to 10 ⁸ μm ² . Image processing the measurement results, the region where at least one of Ni, Zn or Cu is present in a region where Fe is small is an oxide containing Ni, Zn or Cu as a main component, and its area % Is the volume% of the oxide.

As another method, it can be calculated by an energy dispersive X-ray microanalyzer (EDS) while observing with a transmission electron microscope (TEM).

[0020] In addition, the crystal or non-crystal of the oxide is determined,
For quantification, X-ray diffraction or transmission electron microscope (TEM)
Done by For example, the crystal structure of each crystal in the sample can be identified using a transmission electron microscope (TEM). In addition, the ratio of crystal and non-crystal can be measured by simulating by the Rietveld method using the result of identification of the crystal structure and the result of X-ray diffraction of the sample. Further, a so-called calibration curve method in which a crystal or non-crystal is determined based on a calibration curve prepared using analysis samples having different oxide contents may be used.

The ferrite material of the present invention has an average crystal grain size in order to further increase the Bs value without lowering the magnetic permeability.
Preferably it is 1 to 50 μm. The reason for setting the average crystal grain size in the above range in the present invention is that if it is less than 1 μm, the sintering density is reduced and the magnetic permeability is not significantly improved,
If it exceeds 50 μm, the magnetic permeability will not be significantly improved.

In order to further increase the Bs value without decreasing the magnetic permeability, the sintered density of the ferrite material of the present invention is reduced.
It is preferably 5.0 g / cm ³ or more. The reason why the sintering density is set in the above range in the present invention is that when the sintering density is less than 5.0 g / cm ³ , the magnetic permeability is not significantly improved.

Further, the ferrite material of the present invention comprises Fe, Zn,
Ni, Cu and Mn oxides are converted to Fe _TwoO_Three, ZnO, NiO, CuO
And Fe in MnO conversion_TwoO_Three48 to 50 mol%, CuO 5 mol% or less,
MnO is contained in the range of 0.01 to 1 mol%, and the molar ratio of ZnO / NiO is
Preferably, the ratio is between 0.5 and 1.6.

The reason why the content of Fe ₂ O ₃ is 48 to 50 mol% in the present invention is that the Bs value can be further increased without lowering the magnetic permeability. The reason why CuO is set to 5 mol% or less is that the magnetic permeability can be further increased without lowering the Bs value. MnO is set to 0.01 to 1 mol% in order to further increase the Bs value without lowering the magnetic permeability. The reason that the molar ratio of ZnO / NiO is 0.5 to 1.6 is to further increase the Bs value without lowering the magnetic permeability.

In order to simultaneously realize a higher Bs value and a higher magnetic permeability, 48.5-49.5 mol% of Fe ₂ O ₃ , 0.01-4 mol% of CuO, 0.1-0.5 mol% of MnO, and ZnO / NiO 0.7-1.2 molar ratio
Is more preferable.

The ferrite material of the present invention preferably contains 0.001 to 0.1 parts by weight of ZrO ₂ or Y ₂ O ₃ as an accessory component. The reason for adding both amounts of 0.001 to 0.1 parts by weight is that a high Bs value and a high magnetic permeability can be realized at the same time. More preferable addition amount is ZrO ₂ or Y ₂ O ₃ together.
0.001 to 0.01 parts by weight.

It should be noted that the ferrite material of the present invention does not exclude anything other than the above components. For example, Al
₂ O ₃ , SiO ₂ , CaO, MgO, K ₂ O, Cr ₂ O ₃ , P ₂ O ₅ , WO ₃ , PbO, K
₂₀ or the like may be contained in a range of less than 0.05 part by weight.

The method for producing a ferrite material of the present invention is as follows.
It is as follows. Fe_TwoO_Three, ZnO, NiO and CuO powder
At least one specific surface area is 5m^Tworaw material powder exceeding / g
The mixture is mixed and crushed by a vibration mill or the like. At this time, mixed powder
Specific surface area of crushed powder is 5m ^Two/ g powder. Get
The powder at a heating rate of 250 ° C / hour or less, 800-950 ° C
Hold for 10 to 20 hours, and cool at a rate of 100 ° C / hour or less.
The calcined powder obtained by adding the above sub-components,
And granulate. The obtained granules are specified by a well-known method.
It is shaped into a shape and fired at 950-1400 ° C.

Usually, the specific surface area of the powder when producing a ferrite material contributes to the specific surface area of the primary raw material. The powder specific surface area at that time is 2-3 m ² / g. In the present invention, Fe
A powder having a large specific surface area is used to promote the crystallization of a ferrite having a spinel structure containing as a main component, and the specific surface area is further increased by sufficiently mixing and pulverizing. That is, in the present invention, a local raw material having a large specific surface area and a powder having a specific surface area of more than 5 m ² / g after mixing and pulverization are removed to remove a local non-uniform composition. As a result, the content of the oxide containing at least one of Zn, Ni, and Cu as a main component in a part of the ferrite sintered body can be less than 0.01% by volume.

Under the above calcination conditions, the heating rate was 250 ° C. /
The reason why the temperature is kept at 800 to 900 ° C. for 10 to 20 hours is to promote the powder having high specific surface area with high reactivity to ferrite crystal having spinel structure.

That is, in order to make the above oxide less than 0.01% by volume, the specific surface area of the raw material powder of Fe ₂ O ₃ , ZnO, NiO and CuO is increased, and the specific surface area after mixing and pulverization is increased or temporarily. It is advisable to lower the heating rate and lengthen the calcination time under the firing conditions.

Under the above calcination conditions, the temperature drop rate was 100 ° C. /
The reason for setting the time to be equal to or less than the time is that the amorphous particles are likely to be generated at a high cooling rate. That is, when the cooling rate is reduced, the volume% of the crystal particles can be increased.

The subcomponent does not restrict the addition after the calcination, and the addition of the subcomponent to the main component before the calcination does not affect the characteristics at all.

Further, the present invention is characterized in that a ferrite core is formed using the above ferrite material.

Here, the ferrite core is shown in FIG.
A ring-shaped toroidal core 1 as shown in (a) or a bobbin-shaped core 2 as shown in FIG. 1 (b) may be used. By winding the winding portions 1a and 2a, respectively, can do.

Such a ferrite core of the present invention is used for a high-current inductor. In particular, a power supply section through which a large current flows requires a high Bs value and a high inductance, such as a communication device, a cellular phone, and the like. It can be suitably used as a power supply component in a device such as a computer.

[0037]

Example 1 Using raw material powders of Fe ₂ O ₃ , ZnO, NiO and CuO having a specific surface area exceeding 5 m ² / g, 40 mol% of Fe ₂ O ₃ , 1 mol% of CuO, 0.5 mol
% Of MnO and the molar ratio of ZnO / NiO were adjusted to 1.8, and mixed and pulverized by a vibration mill. At this time, the specific surface area of the powder after the mixing and pulverization was 5 m ² / g or more. The obtained powder is heated at a rate of
The temperature was raised at a rate of not more than / hour, the temperature was maintained at 800 to 950 ° C. for 10 to 20 hours, and the temperature was lowered at a temperature lowering rate of 60 ° C./hour. The obtained granules are compression-molded and formed into the shape of the toroidal core 1 shown in FIG. 1, and the formed body is fired at 950 ° C. to 1400 ° C. to obtain Zn, Ni or Cu shown in Table 1. Samples Nos. 5 to 9 containing at least one oxide as a main component were produced.

As comparative examples, Sample Nos. ₂ to 4 containing no oxide containing at least one of Zn, Ni and Cu as main components and containing SiO ₂ which is a nonmagnetic oxide were prepared. .

The sample within the range of the present invention had an average crystal grain size of 0.5 μm or more and a sintered density of 4.5 g / cm ³ or more.

The obtained sintered body was used as a toroidal core 1,
This is wound around a copper wire with a wire diameter of 0.2 mm for 7 turns and is 100 kHz.
The Q value was measured using an LCR meter under the following conditions.

Next, as shown in FIG. 2, a primary winding 3 was wound on the toroidal core 1 by using a coated copper wire having a wire diameter of 0.2 mm.
Turn the secondary winding 4 for 30 turns and connect the power supply 5 to the primary winding 3 and the magnetometer 6 to the secondary winding 4, respectively, and measure the Bs value under the conditions of 100 Hz and 100 Oe. did.

As shown in Table 1, Zn, Ni or
Samples Nos. 8 and 9 containing at least 0.01% by volume of an oxide containing at least one of Cu as the main components had low Bs values and low magnetic permeability.

Samples Nos. 1 to 4 containing the non-magnetic oxide SiO ₂ also had low Bs values and low magnetic permeability.

On the other hand, in Samples Nos. 5 to 7 of the present invention containing less than 0.01% by volume of the above-mentioned oxide, excellent properties such as a Bs value of 2950 gauss or more and a magnetic permeability of 600 or more were obtained.

[0045]

[Table 1]

Example 2 Next, the main components were 40 mol% Fe ₂ O ₃ , 1 mol% CuO, 0.5 mol
% MnO and ZnO / NiO molar ratio was 1.8. The temperature reduction rate during calcination was set at 100 ° C / hour, and the content (vol%) of oxides containing at least one of Zn, Ni and Cu as the main component and the ratio of crystal grains (vol%) were shown. It was changed as shown in FIG. Other conditions were the same as those in Example 1 to obtain Sample Nos. 10 to 17 having the shape of the toroidal core 1.

When the Bs value and the Q value of the obtained sintered body were measured in the same manner as in Example 1, the results shown in Table 2 were obtained.

From these results, in Samples Nos. 10, 11, 14, and 15 in which the crystal grains are 90% by volume or more, Bs value of 3200 gauss or more and magnetic permeability of 820 or more are more excellent. Was.

[0049]

[Table 2]

Example 3 Next, the main components were 40 mol% Fe ₂ O ₃ , 1 mol% CuO, 0.5 mol
% MnO and ZnO / NiO molar ratio was 1.8. In addition, the content (volume%) of an oxide containing at least one of Zn, Ni, and Cu as a main component, and the ratio (volume
%), Average grain size and sintered density were changed as shown in Table 3. Other conditions were the same as in Example 1 to obtain Sample Nos. 18 to 37 in the shape of the toroidal core 1.

When the Bs value and the Q value of the obtained sintered body were measured in the same manner as in Example 1, the results shown in Table 3 were obtained. The average crystal grain size of each sample was determined by taking SEM photographs of sintered porcelain etched by various methods and calculating the average value of the diameters of the inscribed circle and the circumscribed circle in contact with each crystal. Was measured by

From these results, it is found that Sample Nos. 22 to 29 within the scope of the present invention in which the crystal grains are less than 90% by volume, the average crystal grain size is 1 to 50 μm, and the sintered density is 5.0 g / cm ³ or more, Bs value is 2950
Excellent characteristics were obtained with Gauss or higher and magnetic permeability of 650 or higher.

The oxide content is less than 0.01% by volume, the crystal grains are 90% by volume or more, and the average crystal grain size is 1 to 50%.
μm, sample No. 18-21, ³⁰ with a sintered density of 5.0 g / cm ³ or more
In the case of ~ 37, the Bs value was 3300 gauss or more, and the magnetic permeability was 900 or more, further excellent characteristics were obtained.

[0054]

[Table 3]

Example 4 Next, the molar ratios of the main components Fe ₂ O ₃ , CuO, MnO and ZnO / NiO were varied as shown in Table 4 to obtain Zn, Ni or
The content of the oxide containing at least one of Cu as a main component is less than 0.01% by volume, and the ratio of the crystal particles in the content is 80% by volume.
Samples Nos. 38 to 49 having the shape of the toroidal core 1 were obtained in the same manner as in Example 1 except for the above. Each sample had an average crystal grain size of 0.5 μm or more and a sintered density of 4.8 g / cm ³ or more.

The Bs value and the Q value of the obtained sintered body were measured in the same manner as in Example 1. The results shown in Table 4 were obtained.

From these results, it was found that 48 to 50 mol% of Fe ₂ O ₃ , 0.01
Sample Nos. 40 to 49 in which the molar ratio of CuO of 55 mol%, MnO of 0.01 to 1 mol% and ZnO / NiO was 0.5 to 1.6, the magnetic permeability was 600 or more, and the Bs value was 3500 gauss or more. Excellent characteristics were obtained.

[0058]

[Table 4]

Example 5 Next, the main components were 48 mol% of Fe ₂ O ₃ and 1 mol% of CuO, 0.5 mol
% MnO and the molar ratio of ZnO / NiO to 0.7, Zn, Ni or Cu
The content of the oxide containing at least one of the main components
Less than 0.01% by volume, of which the ratio of crystal grains was 80% by volume or more, and the contents of ZrO ₂ and Y ₂ O ₃ as auxiliary components were changed as shown in Table 5, In the same manner as in the above, Sample Nos. 49 to 57 having the shape of the toroidal core 1 were obtained. Each sample had an average crystal grain size of 0.5 μm or more and a sintered density of 4.5 g / cm ³ or more.

The Bs value and the magnetic permeability of the obtained sintered body were measured in the same manner as in Example 1. The results shown in Table 5 were obtained.

From these results, it was found that the amount of ZrO ₂ added was 0.001 to 0.1.
In Sample Nos. 50, 52, 54 to 57 in which the parts by weight or the added amount of Y ₂ O ₃ was 0.001 to 0.1 parts by weight, the Bs value was 4600 gauss or more, and the magnetic permeability was 700 or more and more excellent characteristics were obtained. Was.

[0062]

[Table 5]

[0063]

As described above, according to the present invention, an oxide having a spinel structure containing Fe as a main component and at least one of Zn, Ni or Cu as a main component, and at least one of Zn, Ni and Cu is used. By setting the content of the oxide containing the seed as the main component to less than 0.01% by volume, it is possible to obtain a ferrite material that simultaneously realizes a high Bs value and a high magnetic permeability.

Further, according to the present invention, by forming a ferrite core using the above ferrite material, a large current can be used and the inductance can be increased. Therefore, by using this ferrite core as an inductor for a large current application, it is possible to contribute to miniaturization of various electronic devices.

[Brief description of the drawings]

FIGS. 1A and 1B are perspective views showing a ferrite core of the present invention.

FIG. 2 is a diagram for explaining a method of measuring a Bs value in a ferrite material of the present invention.

[Explanation of symbols]

 1: ring-shaped toroidal core 2: bobbin-shaped core 1a, 2a: winding portion 3: primary winding 4: secondary winding 5: power supply 6: magnetometer

Claims (6)

[Claims] 1. An oxide having a spinel structure containing Fe as a main component and at least one of Zn, Ni and Cu,
A ferrite material characterized in that the content of an oxide containing at least one of Zn, Ni and Cu as a main component is less than 0.01% by volume. 2. The ferrite material according to claim 1, wherein 90% by volume or more of the oxide containing at least one of Zn, Ni and Cu is composed of crystal grains. 3. The ferrite material according to claim 1, wherein the ferrite material has an average crystal grain size of 1 to 50 μm and a sintering density of 5.0 g / cm ³ or more. 4. An oxide of Fe, Zn, Ni, Cu and Mn, respectively.
Fe ₂ O ₃ , ZnO, NiO, CuO and Fe ₂ O _{3 in} terms of MnO: 48 to 50 mol% CuO: 5 mol% or less MnO: contained in the range of 0.01 to 1 mol%, and a molar ratio of ZnO / NiO The ferrite material according to any one of claims 1 to 3, wherein is 0.5 to 1.6. 5. The method according to claim 1, wherein 100 parts by weight of the ferrite material is
Zr or Y oxide as a secondary component, respectively, ZrO ₂
5. The ferrite material according to claim 1, further comprising: ZrO ₂ : 0.001 to 0.1 part by weight in terms of Y ₂ O ₃ , Y ₂ O ₃ : 0.001 to 0.1 part by weight. 6. A ferrite core formed into a predetermined shape with the ferrite material according to claim 1.