KR20010031685A - Manganese-zinc Ferrite and Making Method - Google Patents

Abstract

It is an object of the present invention to provide a manganese-zinc-based ferrite and a method for producing the same, which exhibit a high ultra-permeability in a wide band and especially a high super-permeability in a low frequency region of about 10 kHz.

The holding temperature of the main temperature holding step during the firing of manganese-zinc ferrite is set to 1,200 to 1,450 ° C, and the temperature lowering step during the firing is performed before the main temperature holding step so that the minimum temperature of the temperature lowering step during the firing is 1,000 to 1,400 ° C. By setting the temperature at least 50 ° C lower than the holding temperature of the main temperature holding step, 50 to 56 mol% of iron oxide based on Fe ₂ O ₃ , 22 to 39 mol% of manganese oxide based on MnO, and 8 to 8 based on ZnO A method for producing a manganese-zinc ferrite containing 25 mol% zinc oxide as a main component and having an average grain size of 50 µm to 150 µm is provided.

Description

Manganese-zinc ferrite and its manufacturing method {Manganese-zinc Ferrite and Making Method}

In such broadband transmission transformers, for example pulse transformers, manganese-zinc ferrites for cores with high permeability in broadband and high permeability in the entire range of 10 to 500 kHz are required for accurate digital communication.

In accordance with such a request, the present applicant has provided Japanese Patent Application Laid-Open No. 6-204025 with manganese-zinc ferrite, which exhibits a high permeability in broadband and a high permeability in the entire range of 10 to 500 kHz. The manganese-zinc-based ferrite disclosed in the above publication discloses manganese containing 50 to 56 mol% of iron oxide based on Fe ₂ O ₃ , 22 to 39 mol% of manganese oxide based on MnO, and 8 to 25 mol% of zinc oxide based on ZnO. -Zinc-based ferrite, which is sintered after adding 800 ppm or less of bismuth oxide on the basis of Bi ₂ O _{3 and} 1200 ppm or less of molybdenum oxide on the basis of MoO ₃ .

The manganese-zinc ferrites disclosed in the Japanese Patent Application Laid-Open show high super-permeability over broadband at 10 ° C. at 10 kHz, 100 kHz, and 500 kHz, respectively, of 9,000 or more, 9,000 or more and 3,000 or more, respectively.

The present invention relates to a manganese-zinc ferrite and a method for manufacturing the same, and particularly to a manganese-zinc ferrite having a high initial magnetic permeability (μi) and a method for manufacturing the same, which are preferably used as a core of a broadband transmission transformer. It is about.

1 is a view showing a temperature profile during firing in the embodiment,

2 is a view showing a temperature profile during firing in a comparative example,

3 is a drawing substitute photograph taken a sample cross-section of the present invention,

Figure 4 is a drawing substitute photograph taken a sample cross-section of the comparative example.

In order to realize miniaturization and high speed communication in such a pulse transformer, it is important to show higher ultra-permeability especially in the low frequency region of about 10 kHz. Accordingly, even if the number of turns is reduced, the rise of the output pulse can be sharpened and the amount of operation attenuation can be reduced, so that accurate digital communication can be performed.

It is an object of the present invention to provide a manganese-zinc-based ferrite and a method for producing the same, which exhibit a high ultra-permeability in a wide band and especially a high super-permeability in a low frequency region of about 10 kHz.

(1) 50 to 56 mol% of iron oxide based on Fe ₂ O ₃ , 22 to 39 mol% of manganese oxide based on MnO, and 8 to 25 mol% of zinc oxide based on ZnO as main components,

Manganese-zinc ferrite having an average crystal grain size of 50 µm to 150 µm.

(2) The manganese-zinc-based ferrite of (1), having a bismuth oxide of 800 ppm or less on a Bi ₂ O ₃ basis and a molybdenum oxide of 1,200 ppm or less on a MoO ₃ basis as an auxiliary component with respect to the main component.

(3) The manganese-zinc ferrite of (1) or (2), which further contains 50 to 500 ppm of calcium oxide on a CaO basis.

(4) (1) to (3) where the permeability μ ₁₀₀ measured at a frequency of 10 kHz and magnetic flux density B = 100 millitesla is at least 1.20 times the permeability μ ₁ measured at a frequency of 10 kHz and magnetic flux density B = 1 millitesla Manganese-zinc ferrite.

(5) Manganese-zinc ferrites according to any one of (1) to (4), in which the super-permeability μ ₁ is 15,000 or more at 10 kHz.

(6) The manganese-zinc ferrite of any of (1) to (5), having at least one thermal ramp-down step during firing.

(7) In the manufacturing method of manganese-zinc ferrite by firing, it has a main temperature holding step of 1,200 to 1,4 50 ° C during firing, and a temperature lowering step before the main temperature holding step, A process for producing manganese-zinc ferrite, characterized in that the temperature is set at 1,000 to 1,400 ° C and at least 50 ° C or lower than the holding temperature of the main temperature holding step.

(8) The process for producing manganese-zinc ferrite, which yields the manganese-zinc ferrite of any one of (1) to (6).

In the present invention, the holding temperature of the main temperature holding step during firing of manganese-zinc ferrite is set to 1,200 to 1,450 ° C, and a temperature lowering step is provided before the main temperature holding step so that the minimum temperature of the temperature lowering step during firing is 1,000 to 1,400 ° C. By setting the temperature at least 50 ℃ lower than the holding temperature of the main temperature holding process (hereinafter, referred to as `` temperature drop ''), abnormal crystal growth is prevented and the average grain size is 50 µm to 150 µm, preferably 10 kHz. At, a manganese-zinc ferrite having a super-transmittance of 15,000 or more was obtained. Accordingly, when the core obtained by the manganese-zinc ferrite of the present invention is combined with, for example, a pulse transformer, even if the number of turns is reduced, the output pulse can be sharply raised and the operation attenuation can be reduced, thereby miniaturizing. In addition, high-speed and accurate digital communication is possible.

In addition, since the manganese-zinc ferrite of the present invention has a super-permeability of 100 kHz or the same as that of the conventional manganese-zinc ferrite, the number of turns can be reduced when the transformer is used, thereby miniaturizing the transformer.

The manganese-zinc ferrite of the present invention has a unique characteristic that the magnetic permeability μ ₁₀₀ measured at a magnetic flux density of B = 1 millesla is at least 1.20 times the magnetic permeability μ ₁ measured at a magnetic flux density of B = ₁₀₀ millesla. Indicates. The permeability μ ₁₀₀ / permeability μ ₁ of the conventional manganese-zinc ferrite was 1.10 at the highest.

In addition, Japanese Patent No. 2,914,554 discloses a method of firing manganese-zinc ferrite two or more times as a method capable of producing high-permeability, high-permeability, high-permeability manganese-zinc ferrite having very high efficiency and low unit cost. have. According to the above production method, a firing-lowering step of the same concept as the firing-lowering step of the present invention is disclosed. The minimum temperature of the firing-lowering step is 1,100 ° C. or less, preferably 1,000 ° C. or less, more preferably 500 It is below ℃. Accordingly, the lower the minimum temperature of the temperature lowering step during the firing can be interpreted as being preferable.

In contrast, in the present invention, the minimum temperature of the temperature lowering step during firing was set to a temperature range of 1,000 to 1,400 ° C. Further, in the present invention, the temperature drop in the temperature lowering step during firing is preferably 30 ° C. or higher, particularly 50 ° C. or higher. The reason why the minimum temperature of the temperature-lowering process during baking in this invention was set to 1,000-1,400 degreeC is mentioned later. In the firing method of the present invention, it is possible to shorten the time required in the temperature-lowering step during firing of the conventional firing method, and as a result, the entire manufacturing time can be shortened.

In addition, the present invention aims to improve the super-permeability in the low frequency region of about 10 kHz, but the conventional method aims to improve the super-permeability in the high frequency region of 100 kHz or more.

Hereinafter, the specific structure of this invention is demonstrated.

In the manufacturing method of manganese-zinc ferrite according to the present invention, the holding temperature of the main temperature holding step in the case of firing the molded body of the calcined ferrite material is set to 1,200 to 1,450 ° C, especially 1,350 to 1,450 ° C, and the main temperature is maintained. A temperature lowering step during firing is provided before the step so that the minimum temperature of the temperature lowering step during firing is set to a temperature range of 1,000 to 1,400 ° C., and the temperature drop is set to 30 ° C. or higher, particularly 50 ° C. or higher.

The reason why the holding temperature of the main temperature holding step is set to 1,200 to 1,450 ° C is for promoting ferriteization and controlling the grain size, and the initial permeability at 10 kHz in the temperature range is considerably improved. The temperature holding time of the main temperature holding step is preferably 0.1 to 10 hours.

In addition, the reason why the minimum temperature of the temperature reduction step during the firing is set to 1,000 to 1,400 ° C. is considered to relieve the stress generated between the crystal grains and the grain boundaries.

The minimum temperature is preferably 1,100 to 1,350 ° C, particularly 1,150 to 1,300 ° C, more preferably 1,200 to 1,300 ° C.

If the temperature drop is less than 50 DEG C, the effect of lowering the temperature during firing is lowered, and the improvement of the super-permeability at 10 kHz is not sufficient. The temperature drop is preferably 100 to 250 ° C, particularly preferably 150 to 200 ° C.

In addition, the temperature holding step at the lowest temperature may be provided in the temperature lowering step during firing. In the case where the temperature holding step is performed at the lowest temperature, the temperature is preferably set within 3.0 hours.

The temperature reduction rate in the temperature lowering step during the firing is 20 to 300 ° C./hour, preferably 30 to 200 ° C./hour, and the temperature increase rate is set to 20 to 300 ° C./hour, preferably 30 to 200 ° C./hour. desirable. The temperature lowering step during the firing is preferably within 6.0 hours.

The temperature lowering step during firing is not essential for obtaining the manganese-zinc ferrite of the present invention, but is preferably placed immediately before the main temperature holding step.

A prefiring process or a preliminary temperature maintaining process may come before the temperature lowering step during the firing. In the preliminary firing process or the preliminary temperature holding step, the maximum temperature is equal to or lower than the holding temperature of the main temperature holding step, and must be higher than the minimum temperature of the temperature lowering step during firing, specifically, about 1,100 to 1,400 ° C. . The maximum temperature may be represented by a peak and may be maintained within a range of 5.0 hours. In addition, in the following description, the peak temperature appears as a peak and the holding time is instantaneous is referred to as a preliminary temperature holding process.

In the firing of the present invention, the temperature raising step leading to the preliminary temperature holding step and the temperature lowering step following the main temperature holding step can be the same as the conventional firing temperature profile. Specifically, the temperature increase rate in the temperature raising step is preferably 20 to 50 ° C / hour. The temperature increase rate can be changed to two or more stages. In this case, it is preferable to increase the initial temperature increase rate and gradually slow it down gradually. For example, in the case of using the second stage, it is preferable that the temperature increase rate of the first stage is about 200 to 500 占 폚 / hour, and the temperature increase rate of the second stage is about 20 to 200 占 폚 / hour. On the other hand, the temperature lowering rate in the temperature lowering step is preferably about 20 to 500 ° C / hour. The temperature reduction rate in the temperature lowering step can also be changed to two or more stages, and in the case of two stages, the temperature reduction rate of the first stage is about 20 to 200 占 폚 / hour, and the temperature reduction rate of the second stage is about 200 to 500 占 폚 / hour. It is preferable to set it as.

The furnace used in the firing of the present invention may be a continuous furnace or a batch furnace. Moreover, the atmosphere at the time of baking can be adjusted according to the equilibrium oxygen partial pressure theory, and it is preferable to carry out especially in the nitrogen atmosphere (it exists only in oxygen) which controlled oxygen partial pressure.

Firing under the above conditions according to the present invention yields a manganese-zinc ferrite having an average crystal grain size of 50 to 150 µm and an initial permeability of 15,000 or more at 10 kHz.

The average grain size of the manganese-zinc ferrite of the present invention is preferably 50 to 150 µm, more preferably 60 to 130 µm, particularly preferably 70 to 120 µm. The present invention is manganese-zinc ferrite having an average grain size of 50 to 140 µm and containing at least 50% by volume, in particular at least 70% by volume, more preferably at least 80% by volume. The initial permeability at 10 kHz of the manganese-zinc ferrite of the present invention is preferably 20,000 or more, particularly 25,000 or more. The initial permeability at 10 kHz of the manganese-zinc ferrite of the present invention is currently up to about 35,000, the higher the value is, the better.

The manganese-zinc ferrite of the present invention may have a permeability μ ₁₀₀ of 10 kHz and a magnetic flux density of B = 100 millesla, or more than 1.20 times the permeability μ ₁ of a magnetic flux of a density of B = 1 millesla. . The μ ₁₀₀ / μ ₁ is currently about 1.50 times achieved.

The present invention is suitable for a wide range of compositions of manganese-zinc ferrites, but the main components are about 50 to 56 mol% based on Fe ₂ O ₃ , about 22 to 39 mol% based on MnO, and about 8 to 25 based on ZnO. It is preferable to set it as mol%. Outside of this range, the super-permeability at 10 kHz tends to be lowered.

In addition, the manganese-zinc ferrite of the present invention may contain calcium oxide and silicon oxide as auxiliary components. These auxiliary components are as 50~150ppm based 50~500ppm, particularly 100~300 ppm, SiO _2, based on the CaO, respectively. CaO and SiO ₂ are generally present at grain boundaries.

Such ferrite of the present invention preferably contains bismuth oxide and molybdenum oxide in the form of Bi ₂ O ₃ or MoO ₃ . In this case, the oxidized component of bismuth and molybdenum added, especially the molybdenum oxide component, are partially evaporated or sublimed by firing. Therefore, the content of bismuth oxide and molybdenum oxide in the ferrite does not match the addition amount. That is, the content of bismuth oxide is 50 to 100% by weight of the added amount based on Bi ₂ O ₃ , and the content of molybdenum oxide is preferably 10 to 60% by weight, particularly 10 to 30% by weight based on MoO ₃ . Do.

Moreover, it is preferable that the ferrite of this invention contains 1 or more types of niobium oxide, indium oxide, vanadium oxide, tantalum oxide, and zirconium oxide as needed. These are preferably 3 to 3000 ppm in total, based on Nb ₂ O ₅ , In ₂ O ₃ , V ₂ O ₅ , Ta ₂ O ₅ , and ZrO ₂ , respectively.

As for the average crystal grain diameter of the ferrite of this invention containing such a component, 50 micrometers-150 micrometers are preferable. Even if the average grain size becomes larger or smaller, the super-permeability at 10 kHz is lowered, so that the super-permeability at 10 kHz or more may not be achieved. In addition, the average crystal grain size is preferably obtained by etching the mirror friction surface with an acid, and then calculating the diameter when the polycrystalline body observed by the optical microscope is converted into a circle and making the average.

In this way, when the average crystal grain size becomes large or uniform, the initial permeability at 25 ° C. and 10 kHz can be at least 15,000, especially at least 20,000, more specifically at least 25,000, for example, at about 15,000 to 35,000. The initial permeability can be at least 8,000, in particular at least 9,000, more particularly at least 9,500, for example about 9,500 to 15,000, and the 500 kHz initial permeability is at least 2,000, in particular at least 3,000, more particularly at least 3,500, eg For example, an initial permeability of about 3,500 to 6,000 or more can be obtained.

In order to manufacture the manganese-zinc ferrite of the present invention, first, a mixture of a conventional iron oxide component, manganese oxide component and zinc oxide component is prepared as a main component. These main components are mixed and used as a raw material so that the final component of a ferrite may be said weight ratio. As a raw material of the auxiliary component, calcium carbonate or calcium compound which becomes calcium oxide by firing, calcium oxide, silicon compound which becomes silicon oxide by firing, or silicon oxide is added. In this case, the raw material of these auxiliary components is added so that the final component of a magnetic material may be said weight ratio.

Next, a bismuth oxide component and a molybdenum oxide component are added. Bi ₂ O ₃ , Bi ₂ (SO ₄ ) ₃ and the like can be used as the bismuth oxide component, but Bi ₂ O ₃ is preferable. The amount of the bismuth oxide component added is 800 ppm or less, in particular 600 ppm or less, preferably 100 to 400 ppm, based on Bi ₂ O ₃ . If the addition amount exceeds the above range, the initial permeability is reduced.

In addition, or the like of molybdenum oxide MoO ₃ ingredients, MoCl _3, but the MoO ₃ are preferred. The amount of the molybdenum oxide component added is 1,200 ppm, in particular 1,000 ppm or less, preferably 100 to 1,000 ppm based on MoO ₃ . If the addition amount exceeds the above range, the initial permeability is reduced. If necessary, at least one of niobium oxide, indium oxide, vanadium oxide, tantalum oxide, and zirconium oxide is added to the raw material mixture.

Thus, after mixing a main component and the addition trace component, a small amount, for example, 0.1-1.0 weight% of suitable binders, such as polyvinyl alcohol, is added here, and it shape | molds into 80-200 micrometers diameter granules with a spray dryer, etc.

Next, this molded article is fired. Firing conditions are as above.

By the above, the manganese-zinc ferrite of this invention can be obtained.

Hereinafter, the present invention will be described in more detail with reference to specific examples of the present invention.

(Example 1)

MnO 24 mol%, ZnO 23 mol%, Fe ₂ O ₃ 53 mol% as a main component, CaCO ₃ 200ppm (based on CaO in the final composition of the magnetic material), SiO ₂ 100ppm (in the final composition of the magnetic material), 200 ppm of Bi ₂ O _{3 and} 200 ppm of MoO ₃ were added to obtain a sample.

After mixing them, a binder was added, granulated to an average particle diameter of 150 mu m in a spray dryer, and molded, and 100 tendencies were obtained. 50 of these were fired in accordance with the temperature profile shown in FIGS. 1 (Example) and 2 (Comparative Example) in an atmosphere of controlled oxygen partial pressure to obtain an annular core having an outer diameter of 6 mm, an inner diameter of 3 mm, and a height of 1.5 mm.

In addition, the temperature profile shown in FIG. 1 (Example) and FIG. 2 (Comparative Example) will be described below.

Example Temperature Profile

Temperature raising process:

Heating rate up to 1,200 ℃: 300 ℃ / hour

Temperature rising rate from 1,200 ° C to 1,300 ° C: 100 ° C / hour

Preliminary Temperature Maintenance Process:

1.0 hour at 1,300 ℃

Temperature-fall process during firing:

Minimum temperature: 1,200 ℃

(Difference from the maintenance temperature of the main temperature holding process: 200 ° C)

Temperature dropping rate from 1,300 ℃ to 1,200 ℃: 100 ℃ / hour

Temperature rising rate from 1,200 ° C to 1,400 ° C: 100 ° C / hour

Main temperature holding process:

3.0 hours at 1,400 ℃

Temperature drop process:

Temperature dropping rate from 1,400 ℃ to 1,000 ℃: 100 ℃ / hour

Temperature drop rate from 1,000 ° C to room temperature: 250 ° C / hour

Temperature profile of the comparative example

Temperature raising process:

Heating rate up to 1,200 ℃: 300 ℃ / hour

Temperature rising rate from 1,200 ° C to 1,400 ° C: 100 ° C / hour

Preliminary Temperature Maintenance Process:

none

Temperature-fall process during firing:

none

Main temperature holding process:

3.0 hours at 1,400 ℃

Temperature drop process:

Temperature dropping rate from 1,400 ℃ to 1,000 ℃: 100 ℃ / hour

Temperature drop rate from 1,000 ° C to room temperature: 250 ° C / hour

That is, the temperature profile of the comparative example was made to exclude the preliminary temperature holding process and the temperature-falling process during baking.

In addition, when the final compositions of the examples and the comparative examples were measured by fluorescent X-rays, the main components, Ca and Si almost corresponded to the raw material compositions, and bismuth oxide and molybdenum oxide were 10 to 80% by weight of the added amount.

The initial permeability and average crystal grain size at 25 ° C., 10 kHz, 100 kHz, and 500 kHz of the obtained annular cores were measured. In addition, an impedance analyzer was used to measure permeability. The results are shown in Table 1.

Average grain size (㎛) Initial permeability μi 10 kHz 100 kHz 500 kHz Sample 1 * 27 13,000 12,600 3,300 Sample 2 * 30 15,600 13,200 3,500 Sample 3 * 33 17,800 11,400 2,800 Sample 4 52 22,900 11,800 3,700 Sample 5 67 27,500 12,000 4,000 Sample 6 89 35,700 15,100 5,200 Sample 7 114 33,400 14,400 4,700 Sample 8 132 30,200 12,700 4,200 Sample 9 146 28,200 11,100 3,900

*) Represents the scope of the present invention.

The effect of the present invention is apparent from the results shown in Table 1. That is, according to the present invention, the average crystal grain size is increased to 52 to 146 탆, and the super-permeability at 10 kHz is particularly large compared with the conventional one. Moreover, it turns out that the super permeability of 100 kHz or more is also equivalent to or more than the conventional one. In Examples, crystals having a particle size of 50 to 140 µm were 80% by volume or more.

Examples and Comparative Examples to select a sample one by one arbitrarily with each 10kHz, the magnetic permeability of the magnetic flux density of 10 milli Tesla and 100 milli Tesla (μ _1, μ ₁₀₀₎ the measured, embodiments, and μ ₁ is 32,500, μ ₁₀₀ Was 49,700 and μ ₁₀₀ / μ ₁ was 1.53, but in the comparative example, μ ₁ was 1 2,500, μ ₁₀₀ was 13,900, and μ ₁₀₀ / μ ₁ was 1.11. 3 and 4 show photographs taken by optical microscopy of the sample cross sections of these examples and comparative examples, respectively.

(Example 2)

In the composition of the manganese-zinc ferrite, the main component was the same as in Example 1, and CaCO ₃ and SiO ₂ were added in the samples 12 and 13 as in Example 1, and in the samples 14 to 16, CaCO ₃ and without the addition of SiO ₂ instead of the Bi ₂ O ₃ and MoO containing added in an amount of from to _3, except in the same manner as in example 1 to obtain examples and Comparative examples 12 to 16 the core sample.

Sample 12

Bi ₂ O ₃ : 300ppm

MoO ₃ : 0

Sample 13

Bi ₂ O ₃ : 300ppm

MoO ₃ : 300ppm

Sample 14

Bi ₂ O ₃ : 400ppm

MoO ₃ : 400ppm

Sample 15

Bi ₂ O ₃ : 600ppm

MoO ₃ : 200ppm

Sample 16

Bi ₂ O ₃ : 200ppm

MoO ₃ : 800ppm

The initial permeability was measured in the same manner as in Example 1 for the above sample cores 12 to 16, and the same trend as in Example 1 was obtained.

The manganese-zinc ferrites of the present invention exhibit particularly high ultra-permeability in the low frequency region of about 10 kHz. Moreover, even in the high frequency region with a frequency of 100 kHz or more, the super-permeability as described above or higher is shown.

Claims (8)

It contains 50 to 56 mol% of iron oxide based on Fe ₂ O ₃ , 22 to 39 mol% of manganese oxide based on MnO, and 8 to 25 mol% of zinc oxide based on ZnO as its main components. Manganese-zinc ferrites of 50 μm to 150 μm. The manganese-zinc-based ferrite of claim 1, wherein the manganese-zinc-based ferrite has a bismuth oxide of 800 ppm or less based on Bi ₂ O ₃ and a molybdenum oxide component of 1,200 ppm or less based on MoO ₃ . The manganese-zinc ferrite as claimed in claim 1 or 2, which also contains 50 to 500 ppm of calcium oxide based on CaO. The magnetic permeability μ _{100 as} measured at the magnetic flux density B = 100 millitesla at a frequency of 10 kHz is the magnetic permeability μ _{1 as} measured at the magnetic flux density B = 1 millitesla. Manganese-zinc ferrites that are at least 1.20 times that of. The manganese-zinc ferrite as claimed in claim 1, wherein the super magnetic permeability μ ₁ at 10 kHz is at least 15,000. The manganese-zinc-based ferrite according to any one of claims 1 to 5, which has at least one temperature reduction step during firing. In the manufacturing method of manganese-zinc ferrite, it has a main temperature holding step of 1,200-1,450 ° C during firing, and a temperature-lowering step during firing before the main temperature holding step, and the minimum temperature of the temperature-lowering step during firing is 1,000-1,400 ° C. And at least 50 ° C or lower than the holding temperature of the main temperature holding step. The method for producing manganese-zinc ferrite according to claim 7, wherein the manganese-zinc ferrite of any one of claims 1 to 6 is obtained.