JPH05226138A - Mn-zn ferrite - Google Patents

Abstract

PURPOSE:To obtain a low-loss Mn-Zn ferrite which can reduce power loss drastically by using specific Fe2O3, MnO, and ZnO as basic components and then adding calcium, germanium, and tantalum oxides to the basic components as by-products. CONSTITUTION:A raw material with basic components which are Fe2O3 51.5-54.5mol.%, MnO: 30-40mol.%, and ZnO: 6-18mol.% is mixed as a final composition and then tentative baking is performing within atmosphere. 0.02-0.20wt.% calcium oxide which is converted to CaO, 0.03-0.40wt.% germanium oxide which is converted to GeO2, and 0.01-0.10wt.% tantalum oxide which is converted to Ta2O5 are added and mixed to the tentatively baked powder as sub- components. Furthermore. 0.01-0.60wt.% titanium oxide which is converted to TiO2 or 0.005-0.040wt.% silicon oxide which is converted to SiO2 or both of these are added and mixed, thus obtaining Mn-Zn soft ferrite with an extremely small power loss under a high magnetic field.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a Mn-Zn type ferrite having a small power loss, which is suitable for use in a magnetic core such as a transformer for a switching power supply.

[0002]

2. Description of the Related Art Mn--Zn oxide magnetic material, so-called M
The n-Zn ferrite is widely used as a core and a transformer material for various communication devices, power supplies, etc.
With the spread of the A equipment, it is also used as a transformer material for a switching power supply that operates in a high frequency range of about 100 kHz.

Mn used as such a transformer material
Various characteristics such as a high saturation magnetic flux density, a high magnetic permeability and a low loss can be mentioned as the characteristics required for the -Zn ferrite, but especially for the switching power source transformer which is the object of the present invention, a high magnetic field is used. Below, low loss is particularly important. Therefore, it has been attempted to improve the Mn-Zn-based ferrite by adding various trace components.

For example, in Japanese Patent Laid-Open No. 58-15037.
Is Nb₂ O_Five The addition of
No. 301 publication discloses CaO, Nb₂ O_Five , SiO₂ , V₂ 
O_Five , Al₂ O₃ , CoO, CuO and ZrO₂ Etc.
In addition, the current standard switching frequency of 10
We are trying to improve the loss at 0 kHz,
Power loss at z, 0.2T is 300 to 350 mW /
cm³ It has been realized to a certain level. In addition,
In 63-255903, CaO, SiO ₂ as well as
GeO₂ Is added, but the power loss is 600-700
mW / cm³ Stays in.

[0005]

DISCLOSURE OF THE INVENTION The present invention has a standard switching power supply frequency of 100 kHz, 0.2.
Low loss Mn- that can further improve the power loss of 300 to 350 mW / cm ³ at T and can significantly reduce the loss when used as a transformer for a switching power supply.
It is intended to provide a Zn-based ferrite.

[0006]

In order to solve the above-mentioned problems, the present invention uses, as a basic component, Fe ₂ O ₃ : 51.5 to 54.5 mol% MnO: 30 to 40 mol% ZnO: 6 to 18 mol%. In this basic component, oxides of calcium, germanium and tantalum are added as sub-components. Calcium oxide: 0.02 to 0.20% by weight in terms of CaO Germanium oxide: 0.03 to 0.40% by weight in terms of GeO ₂ tantalum oxide : 0.01 to 0.10 in terms of Ta ₂ O ₅
The present invention provides a Mn-Zn-based ferrite characterized by being contained in an amount of 0.01% by weight, and can further contain an oxide of titanium as an auxiliary component in an amount of 0.01 to 0.60% by weight in terms of titanium oxide: TiO _2. Further, an oxide of silicon may be contained in an amount of 0.005 to 0.040% by weight in terms of silicon oxide: SiO ₂ .

[0007]

First, in the present invention, the ratio of the basic components is changed to Fe _{2
O 3: 51.5~54.5mol%, MnO:} 30~4
The reason for limiting the content to 0 mol% and ZnO: 6 to 18 mol% will be described. The operating temperature of the transformer for the switching power supply is usually 60 to 70 ° C., so that the power loss is low in this temperature range, and the power loss is negative temperature dependence from the room temperature to the temperature range of about 80 to 120 ° C. above the operating temperature. It is desirable to have sex. From this viewpoint, Fe ₂ O
As a result of examining the proportions of ₃ , MnO and ZnO, the above range was obtained.

In the present invention, calcium oxide, germanium oxide and tantalum oxide are added to the above-mentioned basic components as auxiliary components, and titanium oxide or silicon oxide or both are further added. The reasons for limiting the amount are as follows. Calcium oxide: 0.02 to 0.20 wt% in terms of CaO Calcium oxide is a useful component that effectively increases the grain boundary resistance in the coexistence with germanium oxide and thus brings about a low loss, but its content is 0. 02
If it is less than 0.2% by weight, the effect of improving the grain boundary resistance is poor, and if it exceeds 0.20% by weight, on the contrary, the loss becomes large. Therefore, it is added in the range of 0.02 to 0.20% by weight. ..

Germanium oxide: GeO ₂ conversion 0.03
˜0.40 wt% Germanium oxide (mainly GeO ₂ ) increases the electrical resistance of the grain boundary by coexistence with calcium oxide and contributes effectively to the reduction of eddy current loss, but the content is 0.03 wt%. If it is less than 0.4% by weight, the effect of addition is poor, while if it exceeds 0.40% by weight, hysteresis loss increases, so 0.03 to
The range was limited to 0.40% by weight.

Tantalum oxide: 0.01 to Ta ₂ O ₅ equivalent
0.10 wt% tantalum oxide (mainly Ta ₂ O ₅ ) effectively contributes to reduction of loss in the high frequency region. The reason why the loss is improved by the addition of tantalum oxide has not been clarified yet, but it alters the high resistance grain boundary phase formed by the combined inclusion of calcium oxide and germanium oxide, and increases the specific resistance. At the same time, it is considered that it has a function of mitigating the adverse magnetic effect due to the existence of foreign phases at the grain boundaries. However, if the content is less than 0.01% by weight, the effect is poor. On the other hand, if the content is more than 0.10% by weight, the loss is increased.
It was added in the range of 0% by weight.

[0011] The titanium oxide: TiO ₂ in terms of 0.01 to 0.
60 wt% titanium oxide (mainly TiO ₂ ) has the effect of promoting reoxidation of grain boundaries in the cooling process during firing of the ferrite core, increasing the specific resistance of the core, and reducing loss in the high frequency region. If the content is less than 0.01% by weight, the addition effect is poor, while if it exceeds 0.60% by weight, loss is increased. Therefore, it is added in the range of 0.01 to 0.60% by weight. I decided.

Silicon oxide: converted to SiO ₂ 0.005 to 0.
040 wt% silicon oxide (mainly SiO ₂ ) contributes to the reduction of eddy current loss by increasing the grain boundary resistance by coexistence with calcium oxide.
If the content is less than 0.005% by weight, the effect of addition is poor. On the other hand, if it exceeds 0.040% by weight, abnormal grain growth is likely to occur during firing, resulting in unstable properties.
It was limited to the range of 05 to 0.040% by weight.

As described above, it is very effective to increase the specific resistance in order to reduce the loss in the high frequency range up to 100 kHz, but in the present invention, in the coexistence of germanium oxide and calcium oxide, The above object is achieved by containing tantalum oxide, titanium oxide, silicon oxide, or both of them and uniformly dispersing them in grain boundaries.

The conventional method for producing the ferrite of the present invention is
The treatment should be performed according to. That is, the final ferrite
As the composition, for example, iron oxide may be Fe₂ O₃ Converted to 51.
5-54.5 mol%, manganese oxide is 3 in terms of MnO
0 to 40 mol%, zinc oxide 6 to 18 m in terms of ZnO
Mix so that it is contained in the proportion of ol%, and then add
And calcium oxide (calculated as CaO) 0.02-0.2
0% by weight, germanium oxide (GeO₂ Conversion) to 0.0
3 to 0.40 wt% and tantalum oxide (Ta₂ O_Five Exchange
0.01 to 0.10% by weight, and further titanium oxide
(TiO ₂ 0.01 to 0.60% by weight or oxidation
Silicon (SiO₂ (Converted) 0.005-0.040 weight
%, Or both to contain
Made from raw materials. However, the timing of addition of subcomponents will be described later.
There is no problem even after calcination.

This material is calcined at a temperature of 800 ° C. or higher,
Then, after finely pulverized, it is fired in a nitrogen gas whose oxygen concentration is controlled at a high temperature of 1150 ° C. or higher. Note As a raw material of Fe ₂ O _3, not only Fe ₂ O _3, FeO and Fe ₃
It is possible to use O ₄ , and further, compounds capable of being converted into Fe ₂ O ₃ by firing, such as iron hydroxide and iron oxalate. As the MnO raw material, not only MnO, but also MnO ₂ , Mn ₃ O ₄ , and compounds that can be converted to MnO by firing, such as manganese carbonate and manganese oxalate, can be used. Further Zn
The O raw material is not limited to ZnO, but Zn can be obtained by firing.
Compounds that can be converted to O, such as zinc carbonate and zinc oxalate, can be used.

The Ca, Ge and Ta, and further the oxides of Ti and Si may be added in the form of oxides, which are changed into oxides by heating during the manufacturing process, or metals, carbonates, oxalates, etc. May be used.

[0017]

【Example】

[Example 1] Fe ₂ O ₃ : 53.5mo as the final composition
1%, MnO: 34.5 mol% and ZnO: 12mo
After mixing 1% of the raw materials of the basic components, calcination was performed in the atmosphere at 900 ° C. for 3 hours.

With respect to this calcined powder, CaO (added as CaCO ₃ ) and GeO in a ratio as the final composition shown in Table 1 were used.
₂ and Ta ₂ O ₅ were added and blended, and the above raw materials were simultaneously ground and mixed by a wet ball mill. Then, PVA (polyvinyl alcohol) was added as a binder to the mixed powder, and after granulation, the outer diameter was 36 mm, the inner diameter was 24 mm, and the height was 12 mm.
Was molded into a ring shape and baked at 1320 ° C. for 3 hours in a nitrogen atmosphere in which the oxygen partial pressure was controlled.

The DC specific resistance of the thus obtained sintered core was measured by the 4-terminal method, and the frequency was 10
Table 1 shows the results of measuring the power loss at 0 kHz, maximum magnetic flux density: 0.2 T, temperature: 80 ° C. with an AC BH loop tracer.

[0020]

[Table 1]

As is apparent from Table 1, according to the present invention,
Each of which contains calcium oxide, germanium oxide and tantalum oxide as an accessory component is 300 m
Low power losses below W / cm ³ have been achieved. On the other hand, in all cases out of the proper range of the present invention, the loss improving effect is small, and in extreme cases, the loss characteristics are deteriorated conversely due to abnormal grain growth.

Example 2 Fe ₂ O ₃ as the final composition:
52.7 mol%, MnO: 34.6 mol% and Zn
After mixing the raw materials of the basic components of O: 12.7 mol%, calcination was performed in the atmosphere at 900 ° C. for 3 hours. With respect to this calcined powder, C in the ratio as the final composition shown in Table 2 is used.
aO (using CaCO ₃ ), GeO ₂ , Ta ₂ O ₅ and TiO ₂ were added and blended, the above raw materials were simultaneously ground and mixed by a wet ball mill, and then the mixed powder was tested in the same manner as in Example 1.

The test results are also shown in Table 2.

[0024]

[Table 2]

As is apparent from Table 2, according to the present invention,
In addition to calcium oxide, germanium oxide, and tantalum oxide as subcomponents, those containing a composite of titanium oxide have a higher direct current specific resistance and a low power loss of less than 300 mW / cm ³ . On the other hand, none of those outside the proper range of the present invention have a loss improving effect, and in extreme cases, they are conversely deteriorated due to abnormal grain growth.

Example 3 Fe ₂ O ₃ as the final composition:
53.5 mol%, MnO: 34.5 mol% and Zn
O: 12 mol% of the raw materials of the basic components were mixed and then calcined in the atmosphere at 900 ° C. for 3 hours. With respect to this calcined powder, Ca in the ratio as the final composition shown in Table 3 is used.
O (added as CaCO ₃ ), GeO ₂ , Ta ₂ O ₅ and SiO ₂ were added and blended, and the above raw materials were simultaneously pulverized and mixed by a wet ball mill, and then the mixed powder of Example 1
The same experiment was performed.

The test results are shown in Table 3.

[0028]

[Table 3]

As is apparent from Table 3, according to the present invention,
All of the compounds containing calcium oxide, germanium oxide, tantalum oxide and silicon oxide as sub-components have achieved low power loss of less than 300 mW / cm ³ . On the other hand, in all cases out of the proper range of the present invention, the loss improving effect is small, and in extreme cases, the loss characteristics are deteriorated conversely due to abnormal grain growth.

Example 4 Fe ₂ O ₃ as the final composition:
52.7 mol%, MnO: 34.6 mol% and Zn
After mixing the raw materials of the basic components of O: 12.7 mol%, calcination was performed in the atmosphere at 900 ° C. for 3 hours. With respect to this calcined powder, C in the ratio as the final composition shown in Table 4 is used.
aO-(using _{CaCO 3), GeO 2, Ta} 2 O 5, T
io ₂ and SiO ₂ were added and blended, the above raw materials were simultaneously pulverized and mixed by a wet ball mill, and then the mixed powder was tested in the same manner as in Example 1.

The test results are also shown in Table 4.

[0032]

[Table 4]

As is apparent from Table 4, according to the present invention,
In addition to calcium oxide, germanium oxide, tantalum oxide, and titanium oxide as subcomponents, a compound further containing silicon oxide has a high DC specific resistance of 300 mW /
Low power losses of less than cm ³ have been achieved. On the other hand, none of those outside the proper range of the present invention have a loss improving effect, and in extreme cases, they are conversely deteriorated due to abnormal grain growth.

[0034]

According to the present invention, as a core of a transformer for a high frequency power source having a switching power source frequency of about 100 kHz, an Mn-Zn type software having a significantly smaller power loss under a high magnetic field than conventional materials. Ferrite can be obtained.

Claims (3)

[Claims] 1. Fe ₂ O ₃ : 51.5 to 54.5 mol
% MnO: 30 to 40 mol% ZnO: 6 to 18 mol% as a basic component, and oxides of calcium, germanium and tantalum as secondary components in this basic component, calcium oxide: 0.02 to 0.20 wt% in terms of CaO Germanium oxide: GeO ₂ conversion 0.03 to 0.40 wt% Tantalum oxide: Ta ₂ O ₅ conversion 0.01 to 0.10.
A Mn-Zn-based ferrite, characterized in that the Mn-Zn-based ferrite is contained in an amount of 1 wt%. 2. The Mn—Zn-based ferrite according to claim 1, further comprising a titanium oxide as an accessory component in an amount of 0.01 to 0.60 wt% in terms of titanium oxide: TiO _2. -Zn ferrite. 3. The Mn—Zn-based ferrite according to claim 1 or 2, further comprising an oxide of silicon as an accessory component in an amount of 0.005 to 0.040 wt% in terms of silicon oxide: SiO _2. Mn-Zn ferrite.