JPH0812476A - Method for sintering oxide magnetic material with high magnetic permeability - Google Patents

Abstract

PURPOSE:To obtain the subject material at a low cost by laying on a sintered tile powder composed of ZnO and at least one kind of oxide selected from Fe2O3, MnO, Al2O3 and ZrO2 and ZnO, putting a meshy tile thereon, and then putting thereon an oxide magnetic material molded product consisting mainly of Fe2O3, MnO and ZnO, followed by sintering. CONSTITUTION:This sintering method comprises reducing developing internal stress through canceling the composition difference between the surface layer and inner layer of a molded form by preventing the Zn evaporation from the surface layer through controlling the atmosphere during evaporating the Zn through a meshy tile from the ZnO powder in the 2nd layer in the sintering process. Besides, by this method, contact between the molded form and embedded powder etc., can be avoided, preventing its deformation and also preventing the powder from scorching onto the sintered compact. In the figure, the 1st layer represents an Al2O3 tile, 2nd layer the powder 2 composed of ZnO and ZrO2 laid uniformly on the 1st layer, 3rd layer the meshy tile 3, and the molded form 4 is put on the tile 3, followed by sintering at 1400 deg.C for 2h in an oxygen- contg. nitrogen atmosphere.

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 high-permeability oxide magnetic material suitable for use in a transformer magnetic core for communication, and more particularly to a sintering method thereof.

[0002]

2. Description of the Related Art Mn-Zn ferrites are often used as magnetic cores for transformers for various communications. In recent years, there has been a demand for downsizing and high performance of transformers for communication, and for this reason, Mn-Zn ferrites having a large initial permeability have been required.

Conventionally, as a method for increasing the initial magnetic permeability, there is addition of a trace amount of an additive having an effect of promoting grain growth and sintering at a high temperature.

However, in the case of the latter high temperature sintering, Mn-Z
There is a problem in that Zn evaporates from the n-type ferrite surface layer and a composition difference occurs between the surface layer and the inner layer, which causes internal stress and significantly deteriorates the magnetic characteristics. For this reason, conventionally, high magnetic permeability (initial magnetic permeability at 10 kHz is 1000
(0 or more) When sintering a Mn-Zn ferrite compact, in order to prevent evaporation of Zn, the compact is embedded in a powder having the same composition as the compact to be sintered and the particle size is adjusted to sinter. There is a way to do.

[0005]

However, according to this method, the raw material cost of the burial powder, the manufacturing cost and the work load increase, the washing process after sintering occurs, and the yield due to deformation after sintering increases. Since there is a problem of an increase in manufacturing cost due to a decrease or the like, the high magnetic permeability Mn-Zn-based ferrite is different from other Mn-
There is a drawback that the cost is higher than that of Zn-based ferrite.

The present invention eliminates the above-mentioned drawbacks and can be manufactured at low cost, and has an initial magnetic permeability of 1 at 10 kHz.
The present invention provides a method for sintering a high magnetic permeability Mn-Zn-based oxide magnetic material having a magnetic permeability of 0000 or more.

[0007]

The present invention provides a powder composed of ZnO and at least one oxide of Fe ₂ O ₃ , MnO, Al ₂ O ₃ and ZrO ₂ on a sintered tile. It is characterized in that it is spread, a mesh tile is placed on the powder, and a molded body of an oxide magnetic material containing Fe ₂ O ₃ , MnO and ZnO as main components is placed on the mesh tile and sintered. This is a method of sintering a high-permeability oxide magnetic material.

[0008]

In the present invention, the ZnO-containing powder of the second layer during sintering passes through the mesh tile, Zn is evaporated, and the atmosphere is controlled to prevent the evaporation of Zn from the surface layer of the molded body. Eliminates the composition difference of layers and reduces the generation of internal stress. Further, by eliminating the contact between the compact and the buried powder, it is possible to prevent deformation and prevent seizure of the powder on the sintered body.

[0009]

EXAMPLES Examples of the present invention will be described below.

Example 1 First, in a Mn-Zn-based ferrite containing Fe ₂ O ₃ , MnO and ZnO as main components, the composition ratios were Fe ₂ O ₃ 52.0 mol%, MnO 25.0 mol% and the balance. ZnO.

The raw material powders having the above composition ratios were mixed by a ball mill, prefired and granulated, and then the obtained granulated powder was molded. The molded body is ring-shaped and has dimensions of an outer diameter of 30 mm, an inner diameter of 18 mm, and a height of 5 mm. FIG. 1 is a side view showing a sintering method according to the present invention. As shown in FIG. 1, Al ₂ O ₃ tiles second layers uniformly spread a powder 2 composed of ZnO and ZrO _2, the further set reticulated tiles 3 in the third layer thereon first layer Then, the molded body 4 was placed thereon and sintered. At this time, the ZnO content in the powder used for the second layer was changed between 0 and 60 wt%. Sintering is oxygen 0.5
% Nitrogen atmosphere and the temperature was maintained at 1400 ° C. for 2 hours. The sintering temperature is 1350 to 1400.
C., the holding time is preferably 2 to 10 hours, and the atmosphere during sintering is preferably a nitrogen atmosphere containing 0.3% to 3.5% oxygen.

FIG. 2 shows ZnO in the powder used for the second layer.
It is a figure which shows the relationship between content and the magnetic characteristic of the sintered compact obtained by the above. The magnetic characteristics are that the frequency is 10 kHz at room temperature.
The initial magnetic permeability μi at z, the relative loss coefficient tan δ / μi at 10 kHz, and the relative hysteresis loss coefficient h _{10 at 10} kHz were measured.

As shown in FIG. 2, as the ZnO content in the powder composed of ZrO ₂ and ZnO increased, the magnetic characteristics improved, but the ZnO content tended to deteriorate at a peak of 40 wt%. is there. This has a ZnO content of 50%
It is considered that when the sintering is performed as described above, the amount of ZnO on the surface is larger than that inside the sintered body and the internal stress is generated. On the other hand, when the peak ZnO content is 40 wt% or less, on the contrary, the ZnO content on the surface is reduced and internal stress is generated, which is considered to deteriorate the characteristics. Also,
From this example, the optimum range of ZnO content is 30-50w.
It can be seen that it is t%.

(Example 2) A granulated powder of Mn-Zn ferrite was obtained by the same composition and procedure as in Example 1. next,
The obtained granulated powder was molded into A as shown in FIG.
An E-shaped molded body having a B portion size of 30 mm was prepared.

Further, as shown in FIG. 1, Al ₂ is formed in the first layer.
O ₃ tiles 1 and ₂ , a powder composed of ZnO and ZrO ₂ uniformly laid on the second layer (ZnO content is 40 wt%), and a mesh-like Al ₂ O ₃ tile 3 is set on the third layer and placed on top of it. The above E-shaped compact was placed and sintered. The sintering conditions were a temperature of 1400 ° C. and a holding time of 2 hours in a nitrogen atmosphere containing 0.5% oxygen.

Next, with respect to the obtained E-type sintered body, A and B dimensions as shown in FIG. 3 were measured. The results are shown in Table 1.

[0017] As a comparative example, in the stacking process at the time of sintering, Al ₂ O ₃ tiles first layer, uniformly spread of ZnO in the second layer and the powder of ZrO ₂ Metropolitan (ZnO content of 4
0 wt%), an E-shaped compact was placed thereon, and the powder and the compact were directly contacted with each other and sintered to obtain an E-type sintered body in the same procedure as in the above-mentioned example. After that, dimensions were measured. The results are shown in Table 1.

[0018]

[Table 1]

As shown in Table 1, the use of reticulated tiles allows for
The dimensional difference between AB is reduced and the deformation is improved.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments.
Various changes are possible. For example, the powder used in the second layer, in the present embodiment is used a powder composed of ZnO and ZrO ₂ Prefecture, powder made of ZnO and Fe ₂ O ₃ Prefecture Alternatively, ZnO and Fe ₂ O _3, ZrO ₂ and ZnO and Fe ₂ O ₃ , MnO, Al ₂ O ₃ , ZrO, etc.
Needless to say, a powder composed of at least one or more oxides out of ₂ may be used, but powders in combination with other oxides that do not affect ferrite other than these may also be used. Further, the powder of the second layer may be a mixed powder of raw material powders or a powder that has been pre-baked. The tile of the first layer may be a ZrO ₂ tile.

[0021]

As described above, according to the present invention, it is possible to obtain an inexpensive method for sintering a high-permeability oxide magnetic material having an initial magnetic permeability of 10,000 or more.

[Brief description of drawings]

FIG. 1 is a side view showing a sintering method according to the present invention.

FIG. 2 is a diagram showing the relationship between the amount of ZnO in the powder used in the second layer and the magnetic properties of the sintered body. FIG. 2A is a diagram showing the relationship between ZnO content and μi. FIG. 2B shows ZnO content and ta.
The figure which shows the relationship of ndelta / micro | micron | mu. FIG. 2C is a diagram showing a relationship between ZnO content and h ₁₀ .

3 is a front view of an E-shaped core used in Example 2. FIG.

[Explanation of symbols]

 1 tile 2 powder 3 mesh tile 4 molded body A upper dimension B lower dimension

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display H01F 1/34

Claims (1)

[Claims] 1. Fe ₂ O ₃ , MnO, Al on a sintered tile
_A powder composed of ZnO and at least one oxide of at least one of ₂ O ₃ and ZrO ₂ is spread, a mesh tile is placed on the powder, and Fe ₂ O ₃ , MnO, and A method for sintering a high-permeability oxide magnetic material, which comprises placing and sintering a compact of an oxide magnetic material containing ZnO as a main component.