JP3233420B2 - Manganese-zinc ferrite and magnetic core - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a manganese-zinc ferrite and a magnetic core formed from the manganese-zinc ferrite.

[0002]

2. Description of the Related Art Among manganese-zinc ferrites, high permeability soft magnetic materials containing trace amounts of calcium oxide and silicon oxide as subcomponents are used for magnetic cores for high-band transformers of various communication equipment and the like, and magnetic cores for noise filters. It has been heavily used. In such a high magnetic permeability ferrite, a high magnetic permeability is required especially in a high frequency band of about 100 kHz to 500 kHz.

[0003] In the production of ferrites such as manganese-zinc-based ferrite, iron chloride is used as a raw material iron, and iron oxide obtained using the same is mixed with manganese or zinc oxide to form granules, which are then sintered. Ferrite has been obtained.

In such a case, impurities in the raw iron oxide greatly affect magnetic properties such as core loss and magnetic permeability. For example, when the amount of P is large, the magnetic permeability of ferrite with high magnetic permeability is significantly reduced. I do it. For this reason,
It is important to purify the iron chloride solution and regulate the amount of impurities. For example, in JP-A-3-50124, 5
1-54 mol% of Fe ₂ O _3, 19~25 mol% of Zn
High permeability manganese-zinc ferrite containing O
O the 0.01~0.15wt%, the SiO ₂ 0.02wt%
Hereinafter, P is regulated to 0.005 wt% (50 ppm) or less and Cl is regulated to 0.01 to 0.12 wt% or less to improve the magnetic permeability.

[0005] However, purifying the iron chloride solution to reduce the P content requires a great deal of labor and increases production equipment and production costs. Therefore, the permeability in a high-frequency range without changing the P content is increased. It is desired to improve the magnetic susceptibility.

[0006] Further, there is a limit to the improvement of the magnetic permeability by only the regulation of the P amount.
Sufficiently high magnetic permeability cannot be obtained in a high frequency band, for example, in the entire range of 100 kHz to 500 kHz. In this case, the magnetic permeability at a frequency of about 500 kHz is insufficient.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a manganese-zinc ferrite having a high magnetic permeability in a high frequency range and a magnetic core using the same.

[0008]

This and other objects are achieved by the present invention which is defined below as (1) to (5). (1) Iron oxide of 51 to 54 mol% in terms of Fe ₂ O ₃ , M
21-29 mol% of manganese oxide in terms of nO, zinc oxide of more than 20 mol% in terms of ZnO and 25 mol% or less, 100-350 ppm of calcium oxide in terms of CaO, 50-150 ppm of silicon oxide in terms of SiO ₂ and more than 0 300pp
A manganese-zinc ferrite containing m or less of P and containing 30 to 1000 ppm of a sodium compound in terms of metal added and sintered.

(2) The manganese-zinc ferrite according to (1), wherein the amount of the sodium compound added to the content of P is 1 to 60 in terms of metal.

(3) 51 to 54 mol% in terms of Fe ₂ O ₃
Iron oxide, 21 to 29 mol% manganese oxide in terms of MnO, zinc oxide in excess of 20 mol% to 25 mol% in terms of ZnO, 100 to 350 ppm of calcium oxide in terms of CaO, and 50 to 150 ppm in terms of SiO ₂ Containing silicon and P of more than 0 and 300 ppm or less, and 30 to
A manganese-zinc ferrite, which is sintered by adding 1500 ppm of a potassium compound.

(4) The manganese-zinc ferrite according to (3), wherein the amount of the potassium compound to be added to the content of P is 1 to 60 in terms of metal.

(5) A magnetic core comprising the manganese-zinc ferrite according to any one of (1) to (4).

[0013]

According to the present invention, by adding a predetermined amount of potassium or sodium, the electric resistivity increases at each P amount, and a high magnetic permeability in a high frequency band of a frequency of about 100 kHz to 500 kHz, particularly at 500 kHz is realized.

In the present invention, the P content and the potassium content and the sodium content are regulated to predetermined values, respectively, so that P is 5 to 10 in a high frequency range, especially at 500 kHz.
Higher permeability can be obtained than manganese-zinc ferrite with a low P content of about ppm.

The high magnetic permeability on the high frequency side by adding potassium or sodium, for example, at a frequency of about 500 kHz, suppresses abnormal grain growth during sintering that occurs when the amount of P is high, so that the particle diameter becomes large. This is considered to be realized by the fact that the electrical resistivity increases and the eddy current loss decreases.

Heretofore, addition of an alkali metal to a manganese-zinc ferrite has been known. For example, Japanese Patent Publication No. 52-18726 discloses that the addition of 0.06 to 0.04% by weight of Na ₂ O or K ₂ O reduces ferrite noise of a magnetic head and improves initial magnetic permeability.

In Japanese Patent Publication No. 48-6759,
0.032～0.7Wt% of NaCl, with the aim losses reduced by the addition of KCl, in JP-A 1-296602 and JP thereby achieving a loss reduction by the addition of 0.15 wt% or less of K ₂ O.

However, these are not high permeability manganese-zinc ferrites. That is, the content of the main component or the content of the subcomponent and the content thereof are different from those of the present invention, and therefore, high magnetic permeability at a frequency of 100 kHz to 500 kHz cannot be realized.

[0019]

[Specific Configuration] Hereinafter, a specific configuration of the present invention will be described in detail. The manganese-zinc ferrite after sintering in the present invention contains iron oxide, manganese oxide and zinc oxide as main components.

These main components are Fe ₂ O ₃
51 to 54 mol% in terms of conversion, 21 to 29 mol% in terms of MnO,
In particular, the content is 23 to 28 mol%, more than 20 mol% in terms of ZnO, 25 mol% or less, particularly about 21 to 23 mol%. Outside this range, high magnetic permeability cannot be obtained.

The manganese-zinc ferrite of the present invention contains calcium oxide and silicon oxide as secondary components.

[0022] These subcomponents, respectively, and calculated as CaO 100~350ppm, SiO ₂ in terms 50~150ppm about. Outside this range, the frequency is between 100 kHz and 500
It is difficult to obtain a high magnetic permeability at kHz, especially at 500 kHz. Note that CaO and SiO ₂ are generally present at grain boundaries.

The manganese zinc-based ferrite of the present invention further contains more than 300 ppm of P and less than O. If P is not contained, the effect of the present invention by adding sodium or potassium is not exhibited. The content of P is 300pp
m, high frequency range, for example, 100 kHz to 500 kHz
Becomes insufficient.

When using Dalai powder, mill scale, or the like as the raw material iron, reducing the P content requires an extraordinarily large amount of labor in purifying iron chloride. Also, P
Is small, the magnetic permeability at a frequency of about 100 kHz decreases. For these reasons, the content of P is 20
~ 120 ppm, especially 45-80 ppm is preferred. In addition,
P is generally considered to be present at the grain boundaries.

In the ferrite of the present invention, potassium oxide and / or sodium oxide, especially K
It is contained in the form of ₂ O or Na ₂ O.

In this case, the added sodium compound or potassium compound may be partially evaporated or sublimated by firing, and the content of sodium oxide or potassium oxide in the ferrite may not match the added amount. is there. That is, the content of sodium oxide or potassium oxide is about 10 to 100% by weight of the added amount in terms of metal,
In particular, it is about 15 to 50% by weight.

The ferrite of the present invention may further contain, if necessary, one or more of niobium oxide, bismuth oxide, indium oxide, vanadium oxide, molybdenum oxide and the like. These are Nb ₂ O ₅ equivalent, Bi
₂ O ₃ conversion, In ₂ O ₃ conversion, V ₂ O ₅ conversion, MoO ₃
In terms of conversion, the total amount is preferably about 0 to 3000 ppm.

The average crystal grain size of the ferrite of the present invention containing such a component is generally about 20 to 30 μm. The initial magnetic permeability μi at a frequency of 100 kHz at 25 ° C. is 7000 or more, especially 9000 or more, for example, 900
Initial permeability μi of about 0 to 12000 and frequency of 500kHz
Is 2500 or more, especially 4000 or more, for example 4000 to
About 6000 are obtained at the same time.

In order to produce the manganese-zinc ferrite and the magnetic core of the present invention, first, a mixture of a usual iron oxide component, a manganese oxide component and a zinc oxide component is prepared as a main component.

These main components are mixed as the final composition of ferrite so as to have the above-mentioned quantitative ratio, and are provided as raw materials. At this time, the total of the P content in these mixtures is
As described above, O is more than 300 ppm, preferably 20 to
It is regulated to 120 ppm, particularly preferably 45 to 80 ppm.

In this case, the amount of P is small, for example, 10 ppm
If the frequency is restricted to about 100,
The permeability at kHz decreases and the initial value, the initial permeability μ
It becomes difficult to realize i10000. On the other hand, when the amount of P is regulated to a preferable range, for example, about 60 ppm, the permeability at a frequency of 100 kHz is slightly lowered by the addition of potassium oxide, but the initial permeability μi10000 is realized. Magnetic susceptibility can be improved. In addition, at a frequency of 500 kHz, the magnetic permeability can be doubled as compared with the case where no alkali is added. Therefore, the initial permeability μi at 100 kHz, which is the target value, is not less than 10,000 and the initial permeability μi5 at 500 kHz.
000 or more are obtained simultaneously.

As a raw material of the auxiliary component, a compound or calcium oxide, preferably CaCO ₃ , which becomes calcium oxide upon firing of calcium carbonate, and a compound or silicon oxide, preferably SiO ₂ which becomes silicon oxide upon firing are added. Is done. In this case, the raw materials of these subcomponents are added so that the final composition of the magnetic material is in the above-mentioned ratio.

Further, a sodium compound and / or
Alternatively, a potassium compound, more preferably a sodium compound and a potassium compound, particularly preferably a sodium compound is added.

As the sodium compound, Na ₂ CO
₃ , Na ₂ SO ₄ , Na ₃ AlF _{6 and the} like can be used. In this case, if the sodium compound is dissolved, it becomes difficult to uniformly distribute sodium in the material,
Poorly soluble compounds are preferred, of which Na ₃ Al
F ₆ is preferred.

The amount of the sodium compound added is 30 to 1000 ppm, preferably 100 to 400 ppm in terms of metal.

If the addition amount is less than the above range, the effect of the present invention cannot be obtained, and if it exceeds the above range, the magnetic permeability will rather decrease.

The amount of the sodium compound to be added relative to the P content is preferably 1 to 60, particularly 2 to 10, more preferably 2 to 5 in terms of metal. By regulating this ratio as described above, a higher magnetic permeability can be obtained.

As the potassium compound, K ₂ CO
₃ , K ₂ SO ₄ etc. can be used, but K ₂ CO ₃
Etc. are preferred.

The addition amount of the potassium compound is 3 in metal conversion.
0 to 1500 ppm, preferably 200 to 400 ppm. If the addition amount is less than the above range, the effect of the present invention cannot be obtained, and if it exceeds the above range, the magnetic permeability will rather decrease.

The amount of the potassium compound to be added to the P content is preferably 1 to 60, particularly 2 to 10, more preferably 2 to 5 in terms of metal. By regulating this ratio as described above, a higher magnetic permeability can be obtained.

When a sodium compound and a potassium compound are used in combination, the amount of the potassium compound to be added to the sodium compound is preferably 2 or less, particularly preferably 1 or less in terms of metal.

If necessary, one or more of niobium oxide, bismuth oxide, indium oxide, vanadium oxide, molybdenum oxide and the like are further added to the raw material mixture.

After mixing the main component and the added trace component in this manner, the mixture is mixed with a spray drier or the like for 80 to 20 minutes.
Granules having a diameter of about 0 μm. Then, a small amount of a suitable binder, for example, polyvinyl alcohol, for example, 0.1 to 1.0% by weight is added thereto, followed by molding.

Next, the firing method for firing the molded product is not particularly limited, and a normal firing method for a high-permeability manganese-zinc ferrite may be used. For example, in an atmosphere in which the oxygen concentration is controlled, 5 to the desired sintering temperature
The temperature is gradually increased at a rate of about 0 to 150 ° C./hr, and sintering is completed at that temperature.

The firing atmosphere at this time is preferably air, particularly an oxygen atmosphere. The sintering is usually performed in such an atmosphere at a temperature of 1300 ° C. or higher, particularly 1350-14
This is performed by maintaining the temperature at a predetermined temperature in the range of 50 ° C. for about 4 to 5 hours.

After the sintering is completed as described above, the cooling rate is 200 to 300 ° C./h in an atmosphere in which the oxygen concentration is controlled.
It is preferable to cool at about r.

[0047]

EXAMPLES Hereinafter, the present invention will be described in more detail by showing specific examples of the present invention. Example 1 MnO (25.5 mol%), ZnO (21.5 mol%), Fe ₂ O ₃ (53.0 mol%) as main components, CaCO ₃ (150 ppm in terms of CaO), S as subcomponents
iO ₂ (30 ppm) was added. Sample for this comparison
The total amount of P in the main component of No. 1 was 10 ppm.

Further, in this sample No. 1, Na ₃ Al
Sample No. 2 of the present invention was obtained by adding 300 ppm of F ₆ in terms of Na, and Sample No. 3 of the present invention was obtained by adding 200 ppm of K ₂ CO ₃ in terms of K.

Further, the content of P, Na ₃ AlF ₆ (N
a) and K ₂ CO ₃ (K conversion) were changed as shown in Table 1, and sample Nos.
No. 15 was obtained.

After mixing these, the mixture is granulated to an average particle size of 150 μm by a spray drier, molded by adding a binder, kept at 1420 ° C. for 5 hours in an oxygen atmosphere, sintered, and has an outer diameter of 31 mm and an inner diameter of 31 mm. A toroidal core having a thickness of 19 mm and a height of 8 mm was obtained. When the final composition was measured by X-ray fluorescence, the main component and P corresponded to the raw material composition. Calcium oxide was 250 ppm in terms of CaO, and silicon oxide was 100 ppm in terms of SiO ₂ .

The contents of Na and K in terms of metal are as follows:
It was about 15 to 50% by weight of the added amount.

In addition, Comparative Samples Nos. 5 to 7 containing no silicon oxide, calcium oxide, silicon oxide and calcium oxide in Sample No. 8 were obtained.

The volume resistivity ρ of each of the obtained toroidal cores
And the initial permeability μ at a frequency of 100 kHz at 25 ° C.
₁₀₀ and the initial magnetic permeability μ ₅₀₀ at a frequency of 500 kHz were measured. Note that an impedance analyzer was used for measuring the magnetic permeability. These results are as shown in Table 1.

[0054]

[Table 1]

From the results shown in Table 1, the effect of the present invention is clear. That is, the resistivity ρ is increased in accordance with the present invention, the mu ₁₀₀ P: although slightly decreased at 10 ppm, Elsewhere is equally or increased, it is mowing determine which has increased especially mu ₅₀₀ and much .

P: 180 ppm sample of the present invention
It can also be seen that in Nos. 11 and 12, the characteristics of Comparative Sample No. 1 with P: 10 ppm already exceeded.

Optical micrographs of Sample Nos. 8, 4 and 1 are shown in FIGS. 1, 2 and 3, respectively. As can be seen from these photographs, when no alkali is added, the crystal particle diameters are uniform at P: 10 ppm as shown in FIG. 3, but at P: 60 ppm, the crystal particle diameter is as shown in FIG. Is uneven. In contrast,
Sample No. 8 of the present invention containing 60 ppm of P to which Na was added.
Has a uniform crystal particle diameter as shown in FIG. From these results, it can be seen that the addition of Na or K according to the present invention inhibits liquid phase sintering due to P and suppresses abnormal grain growth of crystals.

Example 2 Sample Nos. 1, 8 and 1 produced in Example 1
1 were measured temperature change of the respective mu _100. The result is shown in FIG.

The effect of the present invention is clear from the results shown in FIG.

[0060]

The manganese-zinc phyllite of the present invention has a high electric resistivity and a high frequency band of 100 kHz to 500 kHz.
It has a high magnetic permeability at kHz, especially at 500 kHz.
Moreover, it has a high magnetic permeability even on a low frequency side of a frequency of about 10 kHz to 100 kHz.

Further, according to the present invention, high electric resistivity and high magnetic permeability can be realized without extremely reducing the content of P, so that cost and manufacturing advantages are extremely large.

[Brief description of the drawings]

FIG. 1 is a drawing substitute photograph showing a crystal structure, and is an optical microscope photograph of a manganese-zinc ferrite of the present invention.

FIG. 2 is a drawing substitute photograph showing a crystal structure, and is an optical microscope photograph of a conventional manganese-zinc ferrite.

FIG. 3 is a drawing substitute photograph showing a crystal structure, and is an optical microscope photograph of a conventional manganese-zinc-based ferrite.

FIG. 4 is a graph showing temperature characteristics of initial magnetic permeability μ _{100 at} a frequency of 100 kHz.

Claims (5)

(57) [Claims] 1. An iron oxide of 51 to 54 mol% in terms of Fe ₂ O ₃ , a manganese oxide of 21 to 29 mol% in terms of MnO,
Zinc oxide of more than 20 mol% and 25 mol% or less in terms of ZnO,
100-350 ppm of calcium oxide and S in terms of CaO
iO containing silicon oxide and 0 super 300ppm following P of 50~150ppm with ₂ equivalent, 30 to 100 in terms of a metal
A manganese-zinc ferrite characterized by being sintered by adding 0 ppm of a sodium compound. 2. The manganese-zinc ferrite according to claim 1, wherein the amount of the sodium compound added to the P content is 1 to 60 in terms of metal. 3. An iron oxide content of 51 to 54 mol% in terms of Fe ₂ O ₃ , a manganese oxide content of 21 to 29 mol% in terms of MnO,
Zinc oxide of more than 20 mol% and 25 mol% or less in terms of ZnO,
100-350 ppm of calcium oxide and S in terms of CaO
It contains 50 to 150 ppm of silicon oxide in terms of iO ₂ and more than 0 to 300 ppm of P, and 30 to 150 ppm in terms of metal.
A manganese-zinc ferrite obtained by adding 0 ppm of a potassium compound and sintering. 4. The manganese-zinc ferrite according to claim 3, wherein the amount of the potassium compound relative to the P content is 1 to 60 in terms of metal. 5. A magnetic core comprising the manganese-zinc ferrite according to claim 1.