JPH07211533A - Method of manufacturing oxide magnetic material - Google Patents

Abstract

PURPOSE:To provide a method of manufacturing an oxide magnetic material at high frequency, a low loss, and remaining magnetic density for use in a switching power supply, etc. CONSTITUTION:Fe, Mn, and Zn are mixed at a specific ratio in a type of a chloride solution, and sprayed and heat-dissolved in a spray calciner to form a mixed oxide powder comprising Fe2O3 71.5+ or -2%, MnO 22.5+ or -2%, and ZnO 6.0+ or -2%. Thereafter, they are heat-treated at 1000 deg.C or less and further SiO2 0.005 to 0.1%, CaO 0.01 to 0.5%, TiO2 0.01 to 0.5%, V2O5 0.005 to 0.1%, and Nb2O5 0.005 to 0.1% are used as sub-components and added simultaneously, and a calcine powder being controlled to be a mean particle diameter 0.3 to 1.0mum is used as a main material, and granulated and molded to burn at 1000 to 1200 deg.C. Thus, it is possible to obtain an oxide magnetic material having a small loss value, a great saturated magnetic flux density, and further small remaining magnetic flux density, suitable for a transformer material for a high frequency switching power supply.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to several hundred kHz to several MHz.
The present invention relates to a method for producing a high-frequency, low-loss oxide magnetic material used in a transformer core for a high-frequency switching power supply having a switching frequency of 1.

[0002]

2. Description of the Related Art With the recent miniaturization of electronic equipment, the miniaturization of a switching power supply used as a power supply source thereof has also progressed. Higher switching frequency is indispensable for downsizing of this switching power supply, and electronic components used are required to have high frequency and low loss. In particular, oxide magnetic materials, which are transformer materials, are used together with transistors, FETs, diodes, etc.
It is an electronic material for which low loss at high frequencies is desired.

Under such circumstances, as an oxide magnetic material having a high frequency and a low loss, Japanese Patent Laid-Open Nos. 4-230006, 4-150007, 4-192309, 4-192308, and 4-1449026 are known. JP-A-3-242906, JP-A-3-248405, JP-A-3
-248404, JP-A-3-233907, JP-A-3-
212906, JP-A-3-184307, JP-A3-1
63802, JP-A-3-135002, JP-A-3-13
5003, JP-A-3-93667, JP-A-2-1565
11, JP-A-1-224265, JP-A-63-3192
54, various proposals have been made as disclosed in Japanese Patent Laid-Open No. 60-91602.

Characteristic features of these oxide magnetic materials having a low loss at high frequencies are the increase in resistance of the grain boundary layer due to the oxide and the miniaturization of the crystal grain size. In particular, regarding the crystal grain size, it is necessary that the grain size is fine and at the same time the grain size is uniform. Therefore, the calcined powder used for manufacturing is also required to be fine and have a uniform particle size.

Conventionally, a calcined powder produced by the following manufacturing method has been used. That is, the main component Fe
It is a calcined powder obtained by mixing ₂ O ₃ , MnO, ZnO, etc. in a ball mill, drying it, calcining it in a rotary kiln, etc., and then pulverizing it again in a ball mill.

In the conventional method using the calcinated powder, in order to obtain a fine calcinated powder having a uniform particle size, which is suitable for a high frequency low loss magnetic material, the calcination temperature is lowered and the crushing time is shortened. I needed to make it longer. However, when the calcination temperature is lowered, the sintering reaction of the raw material powder does not proceed and the components are not homogenized.
Further, if the crushing time is lengthened, the amount of impurities mixed from the ball mill increases, which causes abnormal grain growth and the like.

If an attempt is made to produce an oxide magnetic material having a high frequency and a low loss by using the calcined powder obtained by such a conventional manufacturing method, the residual magnetic flux density will increase. The difference between the residual magnetic flux density and the residual magnetic flux density will be reduced. For this reason, there is a problem in that the heat generated when actually mounted in the switching power supply becomes large.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a manufacturing method for obtaining an oxide magnetic material having a low loss at high frequencies and a small residual magnetic flux density.

[0009]

In order to solve the above problems, the present invention uses a powder obtained by spray roasting a chloride solution of a main metal component constituting an oxide magnetic material as a raw material calcining powder. By controlling the particle size of the raw material powder and further adding an additive, an oxide magnetic material having a low residual magnetic flux density and a low loss at high frequency, which were not obtained by a usual method, was obtained. That is, Fe, Mn, and Zn are mixed in a predetermined ratio in the form of a chloride solution, and the obtained liquid is sprayed in a spray roasting furnace to be pyrolyzed, and Fe ₂ O _{3 in} weight% is used.
71.5 ± 2%, MnO 22.5 ± 2%, Zn
After forming a mixed oxide powder of O 6.0 ± 2%, it is heat treated at 200 ° C. or higher and 1000 ° C. or lower, and SiO ₂ 0.005 to 0.100 as a sub-component.
%, CaO 0.010 to 0.500%, TiO ₂
0.010 to 0.500%, V ₂ O ₅ 0.00
_{5 to} 0.100%, Nb ₂ O ₅ 0.005 to 0.10.
0% at the same time, and then mixed and crushed to use the calcined powder whose average particle size is controlled to 0.3 to 1.0 μm as the main raw material, and granulate and shape this calcined powder, A method for producing an oxide magnetic material having a low loss at a high frequency and a low residual magnetic flux density, which is characterized by firing at 1000 to 1200 ° C. while controlling an oxygen partial pressure of an atmosphere.

The present invention will be described in detail below. First,
The reason for using the spray-baked mixed oxide powder will be described. The mixed oxide powder sprayed in a spray roasting furnace and pyrolyzed is sufficiently homogenized because it is mixed in the form of a chloride solution at a prescribed ratio, and powder with a small particle size is obtained. This is because pulverization requires almost no crushing and less impurities are mixed. As a result, a fired body having a uniform grain size and a fine crystal grain size is obtained.

Next, the main components of the mixed oxide powder and the composition range thereof will be described. The mixed oxide of the present invention is made of Fe ₂ O ₃ 71.5 ± 2%, MnO 2 by weight%.
22.5 ± 2% and ZnO 6.0 ± 2% were set, but if deviating from these, the hysteresis loss increases and the loss remarkably deteriorates. Further, the temperature range of the heat treatment of the mixed oxide powder is set to 200 ° C. or higher and 1000 ° C. or lower, in order to sufficiently remove chlorine and prevent unnecessary grain growth.

In the present invention, the addition of a trace amount of additive is an essential condition, and the conditions include SiO ₂ , CaO,
Particularly preferable characteristics are obtained when TiO ₂ , V ₂ O ₅ , and Nb ₂ O ₅ are used. The proper composition range (% by weight) of each additive and the reason therefor are as follows. SiO ₂₀ .
005 to 0.100%, CaO 0.010 to 0.50
This is because the range of 0% does not result in low loss at high frequencies below the lower limit and abnormal grain growth occurs above the upper limit.
In the range of TiO ₂ 0.010 to 0.500%, low loss does not occur at high frequencies at the lower limit or lower, and abnormal grain growth occurs at the upper limit or higher. V ₂ O ₅ 0.005~0.100
%, Nb ₂ O ₅ 0.005 to 0.100%,
This is because if the temperature is below the lower limit, a fired body with a sufficient density cannot be obtained by firing at 1000 to 1200 ° C., and if it is above the upper limit, the loss at high frequencies is deteriorated due to the enlargement of crystal grains.

The firing for obtaining the oxide magnetic material is carried out while controlling the oxygen partial pressure as in the usual production method, but the firing temperature is set to a relatively low temperature of 1000 to 1200 ° C. This is because above this temperature, the crystal grain size becomes too large and the loss at high frequencies becomes worse, and below the lower limit the sintering does not proceed. Further, when the average particle size obtained by mixing and crushing is controlled in the range of 0.3 to 1.0 μm, pores and the like do not remain even though the firing temperature is relatively low at 1000 to 1200 ° C. , The crystal grain size is 0.5 ~
An oxide magnetic material having a low residual magnetic flux density in the range of 5.0 μm and high frequency and low loss can be obtained.

[0014]

EXAMPLES The present invention will be further described below based on examples. Example 71.6 wt% Fe ₂ O ₃ by spray roasting, MnO
An oxide mixed powder having a composition of 22.5 wt% and ZnO 5.9 wt% was manufactured. After heat-treating this at 800 ° C, SiO ₂ 0.025 wt%, CaC in terms of CaO
O ₃ 0.110 wt%, TiO ₂ 0.190 wt
%, V ₂ O ₅ 0.012 wt%, Nb ₂ O ₅ 0.0
22 wt% was added and mixed by a ball mill. When the powder after mixing was measured with a laser diffraction type particle size distribution analyzer, the average particle size was 0.83 μm.

1 part of polyvinyl alcohol was added to the calcined powder.
%, And the water content is adjusted to 3 ± 0.5%, and the pressure after sintering is 2 ton / cm on a ring-shaped core whose shape after sintering is approximately 25 mm in outer diameter, 16 mm in inner diameter, and 7 mm in height.
Pressed at ² . The compact was fired at 1100 ° C. for 5 hours in a nitrogen atmosphere in which the oxygen concentration was controlled. The obtained high-frequency loss oxide magnetic material has a magnetic flux density of 50 mT and a frequency of 5
Table 1 shows the minimum loss value, the saturation magnetic flux density, and the residual magnetic flux density at 00 kHz and 1 MHz.

Comparative Example Comparative Example 1 is a commercially available high frequency low loss oxide magnetic material. Further, Comparative Example 2 uses a conventional method of calcining powder, that is, Fe ₂ O ₃ 71.6 wt% and MnO.
After mixing 22.5 wt% and ZnO 5.9 wt%, 10
It is produced by using a calcined powder obtained by pulverizing powder obtained by calcining at 50 ° C.

Loss values, saturation magnetic flux densities and residual magnetic flux densities of the respective materials of Comparative Examples 1 and 2 were measured in the same manner as in the examples. The results are also shown in Table 1.

Table 1 Loss value (kW / m ³ ) 500 kHz 1 MHz Saturation magnetic flux density Residual magnetic flux density 50 mT 50 mT (mT) (mT) Example 1 48 280 525 160 Comparative Example 1 80 310 470 190 Comparative Example 2 100 400 500 500 200

As is clear from Table 1, the loss values of the oxide magnetic materials produced by the manufacturing method of the present invention are smaller than those of Comparative Examples 1 and 2, and the minimum value is 48 kW / m ^{3 at} 500 kHz, It is 280 kW / m ^{3 at} 1 MHz. Also, regarding the saturation magnetic flux density and the residual magnetic flux density,
The oxide magnetic material using the calcined powder of the present invention has a very high saturation magnetic flux density of 525 mT and a low residual magnetic flux density of 160 mT.

As described above, according to the present invention, it is possible to obtain an oxide magnetic material having a high saturation magnetic flux density and a small residual magnetic flux density as well as a low loss at a high frequency. Therefore, a transformer for a high frequency switching power supply is obtained. Can be used as

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Yoshitaka Yamana 20-1 Shintomi, Futtsu City, Chiba New Nippon Steel Engineering Co., Ltd. New Process Engineering Department

Claims (2)

[Claims] 1. Fe, Mn and Zn are mixed in a predetermined ratio in the form of a chloride solution, and the resulting liquid is sprayed in a spray roasting furnace to be pyrolyzed, and Fe ₂ O ₃ 71% by weight is added. 0.5 ± 2%, MnO 22.5 ± 2%, ZnO 6.0 ± 2%, and a mixed oxide powder of 200 ° C. or higher, 10
Heat treatment is performed at a temperature of 00 ° C. or lower, and then calcinated powder having an average particle diameter controlled to 0.3 to 1.0 μm by mixing and crushing is used as a main raw material. After granulating and molding, firing at 1000 to 1200 ° C. A method for producing an oxide magnetic material. 2. Fe, Mn and Zn are mixed in a predetermined ratio in the form of a chloride solution, and the resulting liquid is sprayed in a spray roasting furnace to be pyrolyzed, and Fe ₂ O ₃ 71% by weight is added. 0.5 ± 2%, MnO 22.5 ± 2%, ZnO 6.0 ± 2%, and a mixed oxide powder of 200 ° C. or higher, 10
00 ° C. heat treatment below, SiO ₂ 0.005 to 0.100% to as an auxiliary _{component, CaO 0.010~0.500%, TiO 2 0.010~0.500} %, V 2 O 5 0. 005 to 0.100% and Nb ₂ O ₅ 0.005 to 0.100% are added at the same time, and then mixed and crushed to control the average particle size to 0.3 to 1.0 μm. Is used as a main raw material, and after granulating and molding, firing is performed at 1000 to 1200 ° C., and a method for producing an oxide magnetic material having a low loss at high frequency and a small residual magnetic flux density.