JPH05190316A - Manufacture of oxide magnetic material - Google Patents

Abstract

PURPOSE:To reduce the core loss of Mn-Zn ferrite as a transformer core material, at a high frequency. CONSTITUTION:For a presintering step of a Mn-Zn ferrite manufacture process, a power of 0.855g/cm<2> or below to the base area of a container is placed thereinto. Then presintering is performed in an air or oxygen atmosphere to produce (Mn, Fe)2O3 of such a quantity that I(Mn, Fe)2O3/IMn-Zn, a ratio of an X-ray diffraction intensity (I(Mn, Fe)2O3) of the Miller indices [222] face of (Mn, Fe)2O3 to an X-ray diffraction strength (IMn-Zn) of the Miller indices [311] face of Mn-Zn ferrite, will be 0.38 or more.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a low loss oxide magnetic material, and more particularly to a method for producing a manganese-zinc based ferrite used for a high frequency switching power supply.

[0002]

2. Description of the Related Art In recent years, the frequency of a switching power supply has been mainly 200 to 300 kHz for downsizing the power supply, but there is a strong demand for further downsizing. Magnetic path cross section A of magnetic material for power transformer, operating frequency f and magnetic flux density B
And have a relationship shown in the equation (1). A = {E / (4.4 × B · N · f)} × 10 ⁻⁷ (1) where A is the magnetic path cross-sectional area (cm ² ), E is the voltage (V), B
Is the magnetic flux density (mT), N is the number of coil turns, and f is the operating frequency (kHz). As is apparent from the equation (1), in order to reduce the size of the magnetic material for the power transformer, a magnetic material having a high magnetic flux density may be used to increase the operating frequency. At this time, it is required to reduce electric energy loss, that is, core loss (mainly hysteresis loss and eddy current loss) generated by the characteristics of the magnetic material when a coil is applied with a voltage. The Mn-Zn-based oxide magnetic material has a higher magnetic flux density and a relatively smaller core loss than other magnetic materials.
It is used as a magnetic material for switching power supply transformers up to the MHz band, and is being researched. But,
The core loss in the high frequency band is still large, and it is the current situation that improvement of the core loss is desired.

[0003]

In order to reduce the volume of the transformer core, it is necessary to further increase the operating frequency of the transformer core, as is apparent from the equation (1), but the core loss is reduced. At present, the higher the frequency becomes, the larger it becomes. Therefore, it is an urgent task to reduce the loss of the transformer core in the high frequency band as much as possible. An object of the present invention is to provide a method for producing an oxide magnetic material that solves the above problems.

[0004]

According to the present invention, manganese (M) is formed by pre-firing raw material powder and then pre-firing.
In the method for producing an n) -zinc (Zn) -based oxide magnetic material, the amount of powder placed in the container in the pre-baking step is 0.855 g / cm ² or less with respect to the bottom area of the container, and the atmosphere is air or oxygen (Mn, Fe) ₂ O ₃ is generated,
The amount is (Mn, Fe) ₂ O ₃ Miller index [222]
X-ray diffraction intensity of the plane (I (Mn, Fe) ₂ O ₃ ) and the Miller index of the Mn-Zn ferrite [311] plane X-ray diffraction intensity (IMn-Z
n) and a ratio I (Mn, Fe) ₂ O ₃ / IMn-Zn of 0.38 or more are pre-baked.

The present invention will be specifically described below.
First, as a raw material for Mn-Zn ferrite, Fe ₂ O ₃ is 9
9% or more, MnCO ₃ (form of MnO raw material) is 99.5% or more, and ZnO is 99% or more. The above raw materials were mixed with 53.0 mol% of Fe ₂ O ₃ and Mn.
37.5 mol% of O and 9.5 mol% of ZnO are weighed, additives are added, and these are mixed by a ball mill or the like so as to be sufficiently uniform. The mixing is preferably wet mixing.

Next, the mixture is dried and then pre-baked. In the pre-baking step, the amount of powder put in the container is 0.855 g / cm ² or less with respect to the bottom area of the container, the atmosphere is in the atmosphere or in oxygen, and (Mn, Fe) ₂ O ₃ is produced, and the amount is (Mn, Fe) ₂ O _3. , Fe) ₂ O ₃ needs to be pre-fired so that the ratio of the X-ray diffraction intensity of Mn—Zn ferrite to the X-ray diffraction intensity is 0.38 or more. However, I (Mn, Fe) ₂ O ₃ is the X-ray diffraction intensity of the (Mn, Fe) ₂ O ₃ Miller index [222] plane, and IMn-Zn is the Mn-Zn ferrite of the Miller index [311] plane. If expressed as a ratio with the X-ray diffraction intensity, I (Mn,
Fe) ₂ O ₃ /IMn-Zn≧0.38. (Mn, Fe) ₂
Ratio of X-ray diffraction intensity of [222] plane of O ₃ to X-ray diffraction intensity of [311] plane of Mn—Zn ferrite I (Mn, Fe)
_{When 2} O ₃ / IMn-Zn is less than 0.38, core loss (power
Loss, PL) becomes large, which is not preferable. In addition, the pre-baking method in which the pre-baked powder has a chance to come into contact with oxygen more,
For example, sparsely filling the pre-baked powder, thinning the thickness of the pre-baked powder, blowing oxygen gas or air into the pre-baked powder, etc. have the same effect. can get. Next, the powder binder (glue) is mixed with the pre-baked powder. Polyvinyl alcohol (PVA) is preferable as the powder binder (paste), but it is not particularly limited thereto. The molding pressure is preferably 1.0 to 3.0 ton / cm ² . After molding, the powder binder is degreased and fired.

[0007]

EXAMPLES Examples of the present invention will be described below. Fe ₂ O ₃
53.0 mol%, MnO (raw material form is MnCO ₃ )
37.5 mol%, the ZnO were weighed so as to be 9.5 mol%, SiO ₂ as grain boundary phase high resistance material 0.
0.05 mol%, CaO (the form of the raw material is CaCO ₃ ) is 0.1%.
1 mol% was added and wet-mixed for 30 hours in an iron ball mill. At this time, 99% alcohol was used as the dispersion medium.
Then, after filtering and drying the mud cloth, the weight shown in Table 1 was put into a boat of the material shown in the same table at 850 ° C. for 4 hours and pre-baked in the atmosphere shown in the same table. The size of the quartz boat is 130 × 180 × 50 mmt in internal dimensions, and the size of the platinum boat is 50 × 120 × 50 mmt. The amount of (Mn, Fe) ₂ O ₃ in the pre-baked powder thus obtained is I (M
The ratio of (n, Fe) ₂ O ₃ / IMn-Zn was as shown in the table.
Rigaku Geiger Flex manufactured by Rigaku Denki Co., Ltd.
Was used.

Next, as a powder binder (paste), P. V. A
After adding, the shape of the molded body is outer diameter φ30, inner diameter φ20,
It was molded into a toroidal type having a thickness of 7 mmt. This compact was placed on an alumina substrate and set in an electric furnace.
The atmosphere is N ₂ gas, 50 ℃ / from room temperature to 600 ℃
The temperature was raised at a rate of h and the temperature was maintained at 600 ° C. for 4 hours for degreasing. After that, the temperature was raised to 1130 ° C. at a rate of 200 ° C./h and heated, and kept at 1130 ° C. for 4 hours. The shape of the obtained sample is outer diameter φ25, inner diameter φ17, thickness 5mm
It was a toroidal type of t. The core loss (PL) was measured with a u function meter under the conditions of a frequency of 1 MHz and a magnetic flux density of 0.05 Tesla, and the measurement results at 60 ° C. are shown in Table 1. It is clear that when I (Mn, Fe) ₂ O ₃ /IMn-Zn≧0.38, the core loss (PL) is 950 mW / cm ³ or less, which is extremely small. The magnetic permeability μ was 2000 or more, and the saturation magnetic flux density 4πMs was 5000 Gauss or more. Also,
The bending strength was 2700 kg / cm ² or more.

[0009]

[Table 1] ──────────────────────────────────── Pre-baking container Pre-baking container Fill I (Mn, Fe) ₂ O ₃ / Core loss (PL) No Charge amount Powder amount in atmosphere of material IMn-Zn (mW / cm ³ ) (g) (g / cm ² ) ────────── ──────────────────────────── 1 10 Quartz Atmosphere 0.043 0.84 680 2 50 Quartz Atmosphere 0.217 0.74 740 3 100 Quartz Atmosphere 0.427 0.63 810 4 200 Quartz in air 0.855 0.38 950 5 ^* 100 Platinum in nitrogen 1.667 0 1350 ───────────────────────────────── ──── ^* mark; Comparative example

[0010]

As described above, according to the manufacturing method of the present invention, the core loss can be made smaller than that produced by the conventional manufacturing method. Mn- according to the invention
By using Zn ferrite as the core of a power transformer, information equipment, communication equipment, electronic measuring equipment, video equipment,
The present invention is extremely useful industrially because it enables downsizing, thinning, weight reduction, and the like of a power source used in audio equipment and the like.

Claims (1)

[Claims] 1. In a method for producing a manganese (Mn) -zinc (Zn) -based oxide magnetic material, which comprises pre-firing a raw material powder and then pre-firing, the amount of powder to be put in the container in the pre-firing step is 0.855 g / cm ² for the bottom area
The atmosphere is as follows (Mn,
Fe) ₂ O ₃ was produced, and the amount thereof was (Mn, Fe) ₂
X-ray diffraction intensity of the mirror index [222] plane of O ₃ (I (Mn, F
e) ₂ O ₃ ) and the Miller index of Mn-Zn ferrite [31
1] ratio of X-ray diffraction intensity (IMn-Zn) to I (Mn, Fe) ₂ O ₃
/ IMn-Zn is pre-fired to be 0.38 or more, a method for producing an oxide magnetic material.