JPH06290926A - Mn-zn ferrite magnetic material - Google Patents

Abstract

PURPOSE:To provide Mn-Zn ferrite magnetic material which is burned at a low temperature, high in density, small in evaporation of Zn, and low in power loss, wherein the magnetic material is used for a transformer or an inductor of a switching power supply. CONSTITUTION:Mn-Zn ferrite magnetic material powder is mainly composed of 10 to 87wt.% of Fe2O3, 10 to 50wt.% of MnO, and 3 to 40wt.% of ZnO, and 0.005 to 0.100wt.% of SiO2, 0.010 to 0.500wt.% of CaO, 0.010 to 0.500wt.% of TiO, 0.005 to 0.100wt.% of V2O5, and 0.005 to 0.100wt.% of Nb2O5 are added to Mn-Zn ferrite magnetic material powder at the same time, and the mixture of powders is burned at a temperature range of 800 to 1200 deg.C into a burned body 4. 8g/cm<3> or above in burning density, whereby a low-loss Mn-Zn ferrite remarkably lessened in burning cost can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low loss Mn-Zn ferrite magnetic material used as a magnetic core material for transformers and inductors, and a method for producing the same.

[0002]

2. Description of the Related Art In recent years, switching power supplies have become smaller and lighter as electronic devices have become smaller. Behind this is the development of low-loss Mn-Zn ferrite magnetic materials used as magnetic core materials for transformers and inductors. As a low-loss Mn-Zn ferrite magnetic material, JP-A-3-
163803, JP 3-141621, JP 3-248403, JP 4-69905, JP 3-223119, JP 3-254103, JP 2-30660, JP 2-54901, JP 2-54902.
, JP-A-2-122603, JP-A-2-124724, JP-A2-1
83501, JP 2-153501, JP 1-143307, JP 1-259509, JP 64-79016, JP 63-62206, JP 63-255903, JP 63-260883, JP Sho 63-14406
It is disclosed in many publications such as the Japanese publication.

Particularly, in JP-A-3-141612, B-H
Loop saturation magnetic flux density Bs / residual magnetic flux density Br is 3.0
Above, frequency 100kHz, magnetic flux density 200mT, temperature 10
A transformer material for a high frequency power source with a loss at 0 ° C. of 450 kW / m ³ or less has been obtained by adding niobium oxide alone. On the other hand, in view of the fact that the switching frequency has shifted from 100kHz to a high frequency of 500kHz as a trend of recent switching power supplies, it is clear that it is necessary to reduce not only the conventional loss of 100kHz but also the loss at 500kHz. is there. That is, it is necessary to develop a low-loss Mn-Zn ferrite magnetic material in such a wide frequency range.

By the way, in the current typical manufacturing method of Mn-Zn ferrite, first, iron oxide Fe ₂ O _{3 as} a raw material,
Manganese oxide Mn ₃ O ₄ and zinc oxide ZnO are weighed in a composition ratio so that the desired magnetic characteristics can be obtained, and wet mixed in a ball mill. Next, the obtained slurry is dried and calcined at 800 ° C to 1100 ° C. After wet pulverization with a ball mill again, a binder such as polyvinyl alcohol is added to granulate, and the mixture is filled in a mold and pressed to obtain a molded product having a required shape.

In the prior art, this molded product has a temperature of 1250 ° C. to 13 ° C. while controlling the oxygen concentration in the atmosphere.
It has been fired in the high temperature range of 50 ° C. However,
Due to such a high firing temperature, the heat-resistant furnace material is heavily consumed, and the amount of energy for keeping the furnace temperature at a high level is enormous, so that the cost is inevitably high. Further, if the firing temperature is high, Zn evaporates from the surface of the ferrite core during firing, and the composition of the surface layer changes, resulting in deterioration of magnetic properties such as high permeability not being obtained.

To reduce such high firing costs
In Japanese Patent Laid-Open No. 63-222018, CaO, Si
O₂, V₂O_Five, Ta₂O_Five, SnO₂, CuO, Na
₂O, Ag ₂Depending on the O additive, the firing temperature may be increased to 1150 ° C.
Attempts have been made to lower it. In addition, JP-A-3-268404
In the publication, firing at a temperature of 1100 ° C or higher and lower than 1250 ° C
It is mentioned about the success.

Further, in order to prevent deterioration of magnetic properties due to evaporation of Zn, a method of using a case having the same composition as that of the fired body or firing a molded body of zinc oxide at the same time is disclosed in JP-A-3-4170.
No. 8 publication.

[0008]

An object of the present invention is to reduce loss in the frequency range of 100 kHz to 500 kHz.
Low loss M with high saturation magnetic flux density and low residual magnetic flux density
An object is to provide an n-Zn ferrite magnetic material. At the same time, a method for obtaining a low-loss Mn-Zn ferrite magnetic material that enables a high sintered density to be obtained even at a firing temperature of 1200 ° C. or less, has a small amount of Zn evaporated by low-temperature firing, and has excellent magnetic characteristics is provided. To provide.

[0009]

Means for Solving the Problems The present invention is intended to solve the above problems, and the gist thereof is as follows: (1) MnO: 10 to 50% by weight as a main component.
%, ZnO: 3-40%, Fe ₂ O ₃ : 10-87%,
SiO ₂ : 0.005 as a trace element
~ 0.100%, CaO: 0.010 ~ 0.500%,
_{TiO 2: 0.010~0.500%, V 2} O 5: 0.
_{005~0.100%, Nb 2 O 5:} 0.005~0.
100% at the same time, density of 4.8g / cm ³ or more,
A Mn-Zn ferrite magnetic material, characterized in that the compositional difference between ZnO on the surface and inside is 0.5% by weight or less. (2) Fe ₂ O ₃ : 71.5% by weight as the main component
± 2%, MnO: 22.5 ± 2%, ZnO: 6.0 ± 2
%, And as a trace element, SiO ₂ : 0.0
05-0.100%, CaO: 0.010-0.500
%, TiO ₂ : 0.010 to 0.500%, V ₂ O ₅ :
_{0.005~0.100%, Nb 2 O 5:} 0.005~
0.100% at the same time, density 4.8 g / cm ³ or more, saturation magnetic flux density 520 mT or more, residual magnetic flux density 170 mT
Below, the magnetic flux density is 200 mT, the loss value at a frequency of 100 kHz is 300 kW / m ³ or less, the magnetic flux density is 50 mT, and the frequency is 500.
A low-loss Mn-Zn ferrite magnetic material having a loss value of 70 kW / m ³ or less at kHz and a composition difference between the surface and the interior of ZnO of 0.5 wt% or less. (3) Also, as a main component, Fe ₂ O ₃ : 7 by weight%
1.5 ± 2%, MnO: 22.5 ± 2%, ZnO: 6.
It has a composition of 0 ± 2%, and as a trace element, SiO ₂ :
0.005-0.100%, CaO: 0.010-0.
_{500%, TiO 2: 0.010~0.500%} , V 2
_{O 5: 0.005~0.100%, Nb 2} O 5: 0.0
Density of 4.8 g / cm ^{3 is} obtained by using Mn—Zn ferrite raw material powder that also contains 0.05 to 0.100%.
Above, saturation magnetic flux density 520mT or more, residual magnetic flux density 170
Loss of 300 kW / m ³ or less at a magnetic flux density of 200 mT and a frequency of 100 kHz at a frequency of 100 kHz, and a magnetic flux density of 50 mT at a frequency of 50
Low loss Mn-Zn with a loss value at 0 kHz of 70 kW / m ³ or less and a composition difference between the surface and the interior of ZnO of 0.5 wt% or less
The ferrite magnetic material was obtained by firing at a firing temperature of 800 to 1200 ° C., and firing at 1100 ° C. or less was possible.

The ranges of the above components were determined for the following reasons. That is, the range of the main component composition is Mn-
It was limited because the original low-loss magnetic characteristics of Zn ferrite are lost. Therefore, the effect of the present invention is that the density is 4.8 g.
/ Cm ³ or more, the difference in composition between the surface and the interior of ZnO is 0.5 wt% or less, and the fact that the composition can be fired at 800 to 1200 ° C. %, MnO: 10-50%, ZnO: 3-40%,
Fe ₂ O _3: 10~87%, and made.

In the range of SiO ₂ and CaO, the loss at 500 kHz is deteriorated below the lower limit value above 300 kW / m ³ , and above the upper limit value, the loss value is also high due to occurrence of abnormal grain growth. Limited Also, TiO
_{When 2} is out of the above range, the loss at 500 kHz becomes worse below the lower limit and becomes 300 kW / m ³ or above, and the abnormal grain growth occurs above the upper limit and the loss also deteriorates. Therefore, cracks will occur.

With respect to the ranges of V ₂ O ₅ and Nb ₂ O ₅ , when the composition is below the above lower limit value and the firing is carried out at 800 to 1200 ° C., the sintering density becomes 4.8 g / cm ³ or less, and the saturation magnetic flux becomes saturated. A density of 520 mT or more cannot be obtained, and above the upper limit value, vacancies remain in the crystal grains, resulting in high loss at both 100 kHz and 500 kHz. These S
If even one additive of iO ₂ , CaO, TiO ₂ , V ₂ O ₅ , and Nb ₂ O ₅ is out of the above range or lacks, it is necessary to set the sintering density to 4.8 g / cm ³ or more.
Since firing at 0 ° C. or higher is required, and Zn inevitably evaporates, the difference in composition between the surface and the interior of ZnO becomes 0.5% by weight or more.

Further, the low-loss Mn-Zn ferrite magnetic material of the present invention is obtained by firing at 800 to 1200 ° C. for 5 to 15 hours. At the time of firing, the oxygen concentration of the atmosphere is adjusted according to the firing temperature. It changes.

[0014]

According to the present invention, the loss value at 100 kHz and 200 mT is 300 kW / m ³ or less, and at the same time 500 kHz and 50
The loss value at mT was 70 kW / m ³ or less. By the way, 100 of the highest level low loss materials currently on the market
The published value for kHz and 200 mT is 410 kW / m ³ (100 ° C)
The highest level of high frequency and low loss material, 500kH
The published value of z and 50 mT is 80 kW / m ³ (100 ° C).

Further, according to the present invention, the conventional material is 4.8 g.
/ Cm ³ or less, the sintered density is 4.8 g / cm ³ or more, and therefore the saturation magnetic flux density, which is usually 510 mT or less, is 5 or less.
It was over 20mT. Furthermore, the residual magnetic flux density is 170 mT
In the following, when actually mounted on a power supply and used as a transformer, the difference between the saturation magnetic flux density and the residual magnetic flux density, which is the operating range, can be increased.

The Mn-Zn ferrite magnetic material of the present invention is the conventional material Mn-Zn ferrite magnetic material 1250-150.
800 when sintered in the temperature range of 1350 ° C
Firing in a temperature range of up to 1200 ° C. is possible, consumption of heat-resistant furnace material can be reduced, and the amount of energy required to maintain the temperature of the furnace can be significantly reduced. Further, since the present invention is low-temperature firing, the composition difference between ZnO on the surface and inside of the Mn-Zn ferrite magnetic material is 0.5% by weight in the normal firing method.
As described above, the content is suppressed to 0.5% by weight or less, the evaporation of Zn which causes deterioration of magnetic characteristics is small, and the invention can be applied to a high magnetic permeability material and the like.

[0017]

EXAMPLES The characteristics and manufacturing method of the low-loss Mn-Zn ferrite magnetic material according to the present invention will be described below in detail. Example 1: 71.0% by weight of Fe ₂ O _{3 and} 2 of MnO
A total of 500 g of Fe ₂ O ₃ , Mn ₃ O ₄ , and ZnO was weighed so that the composition was 3.0% by weight and ZnO was 6.0% by weight, and 500 g of pure water was simultaneously mixed with a ball mill.
This powder is dried, calcined at 800 ° C for 2 hours, and SiO ₂
0.050 wt% and CaCO ₃ 0.2 in CaO conversion
00 wt%, the TiO ₂ 0.400 wt%, V ₂ O ₅ 0.040 wt%, Nb ₂ O ₅ and was added 0.050% by weight, were mixed and ground again by a ball mill.

PVA (polyvinyl alcohol) was added to the obtained powder in an amount of 1% by weight to prepare granulated powder having a water content of 3.0 ± 0.5%. The outer diameter was 25 mm and the inner diameter was 16 m.
It was press-molded into a ring having a height of 6 mm and a pressure of 2.5 ton / cm ³ . This molded body was heated to 500 ° C. at 5 ° C./hr, and heated to 1100 ° C. at 100 ° C./hr. 80 on the way
Nitrogen gas was mixed into the air at 0 ° C., and the atmosphere was switched to an oxygen concentration of 0.74%. After reaching 1100 ° C, hold for 5 hours, control oxygen concentration up to 500 ° C, 150 ° C / hr
After that, the temperature was lowered and the furnace was cooled thereafter.

The conductor 2 is attached to the ring-shaped core thus obtained.
The book was wound 4 turns each, and the loss value was measured by a BH analyzer (manufactured by Iwasaki Tsushin Co., Ltd.).
z, 280kW / m ³ at 200mT (80 ° C), 500kHz
, 50 kW / m ³ (80 ° C.) at 50 mT. Also,
The saturation magnetic flux density and residual magnetic flux density at an applied magnetic field of 800 A / m were measured at room temperature of 25 ° C.
T was 149 mT. 410m at 100 ℃
It was T, 60 mT. The result of the density measurement by the Archimedes method was 4.93 g / cm ³ . Example 2: 50 molded articles produced in the same manner as in Example 1
Temperature rises up to 0 ℃ at 5 ℃ / hr, up to 800 ℃ 100 ℃ / hr
The temperature was raised. The atmosphere is switched at 800 ° C, the temperature is maintained for 15 hours, and the oxygen concentration is controlled up to 500 ° C at 150 ° C /
The temperature was lowered at hr and the furnace was cooled thereafter.

The loss value of the ring-shaped core thus obtained was measured and found to be 295 kW / at 100 kHz and 200 mT.
^{m 3 (80 ℃), 39kW} / m 500kHz, with 50mT
^{It was 3} (80 ° C). In addition, the applied magnetic field 8 at room temperature 25 ° C
The saturation magnetic flux density and residual magnetic flux density at 00 A / m were measured and found to be 522 mT and 168 mT, respectively. 1
At 00 ° C., they were 400 mT and 65 mT, respectively. Furthermore, the result of the density measurement by Archimedes method is 4.87 g.
It was / cm ³ . Example 3: In order to examine the difference in the composition of Zn between the surface and the inside of the burned Mn-Zn ferrite magnetic material, the cross sections of the ring-shaped cores of Examples 1 and 2 were polished, and the vicinity of the surface and the central portion were measured by XPS. When the composition was examined, the results shown in Table 1 were obtained.

[0021]

[Table 1]

In Comparative Example 1, Fe ₂ O ₃ was 71.0% by weight, MnO was 23.0% by weight, ZnO was 6.0% by weight, and SiO ₂ was 0.1% by weight as a minor additive. 0
Example 1 containing 15% by weight and 0.065% by weight of CaO
A Mn-Zn ferrite magnetic material produced by the conventional method, in which a molded body obtained in the same manner as in 1. was fired at 1300 ° C. In addition, Example 3 is different from Example 1 in the main component composition, but in the case where the trace elements are the same as in Example 1.

In Examples 1 and 2 according to the present invention, Z
The difference in composition between the surface and the central portion of nO is 0.5% by weight or less, whereas in Comparative Example 1, there is a difference of 0.8% by weight or more. The magnetic characteristics will be described in Comparative Example 15,
Also in Example 3 having a main component composition different from that of Example 1, it can be seen that evaporation of Zn is small when the trace element of the present invention is added and firing is performed at a low temperature. Example 4 to Example 8: Example 4 when the firing temperature was changed
-Example 2 is shown in Table 2.

[0024]

[Table 2]

As the fired compact, the same one as in Example 1 was used. In the examples according to the present invention, sufficient magnetic properties and densities were obtained even at low firing temperatures. Further, with respect to the molded body of Comparative Example 1, Comparative Examples 2 to 6 when the firing temperature was changed are also shown in Table 2. However, at 1200 ° C. or lower, sufficient density and necessary magnetic characteristics were not obtained. . Example 9 to Example 20: Table 3 shows the results of Example 9 to Example 20 when the amounts of the trace elements were changed.

[0026]

[Table 3]

The main component composition is the same as in Example 1. Further, in Table 3, there are two numerical values in the magnetic property column and the density column when the lower stage is the case of firing at 1100 ° C. as in Example 1, and the upper stage is 800 as in Example 2. This is the case when firing at ℃. All of Examples 10 to 20 have the magnetic characteristics and density of the present invention. On the other hand, in Comparative Examples 7 to 13 in which the trace elements shown in Table 4 were lacking, the magnetic characteristics and the density of the present invention were not obtained.

[0028]

[Table 4]

Examples 21 to 32: Table 5 shows the results of Examples 21 to 32 when the same amount of the trace element as in Example 1 was added and the main component composition was changed.

[0030]

[Table 5]

When the main component composition is within the range of the present invention, a Mn-Zn ferrite magnetic material having a high magnetic flux density, a small residual magnetic flux density, a small loss, and a high density is obtained. On the other hand, in Comparative Example 14 in which the main component composition was out of the range of the present invention, the sintered density was obtained, but the magnetic characteristics were deteriorated. Examples 33 to 37: Examples 33 to 37 in which the main component composition was changed within the scope of the third invention were carried out. All trace elements were added in the same amounts as in Example 1. Table 6 shows the results of examining the density of the obtained fired body and the composition difference between the surface and the interior of Zn.

[0032]

[Table 6]

In Table 6, there are two numerical values when the lower stage is fired at 1100 ° C. as in Example 1.
The upper part shows the case where firing was performed at 800 ° C. as in Example 2. From this result, within the range of the main component composition of the third invention,
It can be seen that a Mn-Zn ferrite magnetic material having a density of 4.8 g / cm ³ or more and a composition difference between the surface and the interior of ZnO of 0.5% by weight or less can be obtained.

[0034]

According to the present invention, the frequency range from 100 kHz to
The loss at 500 kHz can be reduced as compared with the conventional one, and a low loss Mn-Zn ferrite magnetic material having a large saturation magnetic flux density and a small residual magnetic flux density can be provided. Further, it is possible to obtain a high sintered density even at a firing temperature of 1200 ° C. or lower, and to provide an Mn—Zn ferrite magnetic material excellent in magnetic characteristics, which causes little Zn evaporation by low temperature firing. became.

Claims (3)

[Claims] 1. MnO: 10 as a main component in% by weight.
˜50%, ZnO: 3-40%, Fe ₂ O ₃ : 10-8
It has a composition of 7%, and as a trace element, SiO ₂ : 0.
005 to 0.100%, CaO: 0.010 to 0.50
_{0%, TiO 2: 0.010~0.500%} , V
₂ O ₅ : 0.005 to 0.100%, Nb ₂ O ₅ : 0.
Density 4.8g, including 005 to 0.100% at the same time
/ Cm ³ or more, the composition difference of ZnO between the surface and the inside is 0.5 wt% or less, Mn-Zn ferrite magnetic material characterized by the above-mentioned. 2. The main component composition, in% by weight, is Fe ₂ O.
₃ : 71.5 ± 2% MnO: 22.5 ± 2% ZnO: 6.0 ± 2%, density 4.8 g / cm ³ or more, saturation magnetic flux density 520
mT or more, residual magnetic flux density 170 mT or less, magnetic flux density 200 m
T, loss value at frequency 100kHz is 300kW / m ³ or less,
Magnetic flux density 50mT, loss value at frequency 500kHz is 70kW
/ M ³ or less, the low-loss Mn-Zn ferrite magnetic material according to claim 1. 3. MnO: 10-50% by weight, Zn
_{O: 3~40%, Fe 2 O} 3: 10~87%, the Mn-Zn ferrite material powder consisting of, SiO _2: 0.005
~ 0.100%, CaO: 0.010 ~ 0.500%,
_{TiO 2: 0.010~0.500%, V 2} O 5: 0.
_{005~0.100%, Nb 2 O 5:} 0.005~0.
Mn-Zn ferrite having a sintering temperature of 800 to 1200 ° C., a density of 4.8 g / cm ³ or more, and a composition difference of ZnO between the surface and the interior of 0.5% by weight or less by simultaneously adding 100% as an additive. Manufacturing method of magnetic material.