JPH0725618A - Production of soft ferrite - Google Patents

Abstract

PURPOSE:To provide a technology enabling the stable production of a soft ferrite having excellent magnetic characteristics. CONSTITUTION:A soft ferrite is produced by adding at least one kind of additive as a subsidiary component to a basic component. In the above production process, the average particle diameter of the additive is controlled, according to the addition timing, to a size finer than the average particle diameter of the mixed raw material powder and/or the average particle diameter of crushed ferrite powder obtained by crushing a burnt product. This process enables stable production of a soft ferrite having excellent magnetic characteristics.

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 soft ferrite, and particularly to a method for stably producing soft ferrite having excellent magnetic properties.

[0002]

2. Description of the Related Art Generally, soft ferrite materials such as Mn-Zn type ferrite and Ni-Zn type ferrite are widely used for noise filters of various communication devices and transformer cores. This soft ferrite material is required to have further improved magnetic characteristics in order to realize miniaturization and high integration of today's electronic devices. Therefore, the conventional soft ferrite materials are Fe ₂ O ₃ , MnO, Zn
With respect to basic components such as O, NiO, and MgO, various additives that segregate at the crystal grain boundaries of the sintered body and control and improve electromagnetic and mechanical properties by interaction with the crystal grains are used. Improvements have been made according to each application.

For example, in polycrystalline Mn-Zn type ferrite,
A technique has been proposed in which a small amount of SiO ₂ or CaO is added to increase electric resistance to reduce eddy current loss and magnetic loss of Mn-Zn ferrite (Japanese Patent Publication No. 36-
2283). However, this technique is still insufficient to meet the demand for even lower magnetic loss in recent years, and it was essential to use other types of additives. For example, a technique for further reducing magnetic loss by adding Nb ₂ O ₅ , V ₂ O ₅ , Al ₂ O ₃ , CoO, CuO, ZrO ₂ in addition to the above SiO ₂ and CaO additives is known. , JP-A-60-132301. As described above, various studies have been performed on many additives from the past, but these are based on the viewpoint of making the component composition and thickness of the grain boundaries where the additives segregate uniform. It is not a technique for improving the magnetic characteristics by controlling the powder properties.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and it is possible to stably produce soft ferrite having excellent magnetic properties by controlling the powder property of the additive. The purpose is to provide the technology that can.

[0005]

[Means for Solving the Problems] In the production of soft ferrite, in addition to the basic component as a matrix, it segregates at the crystal grain boundaries of the sintered body and interacts with the crystal grains, resulting in electromagnetic and mechanical properties. Various additives are used to control and improve the like. The content of this additive is usually tens to thousands.
It is said that the amount is as small as ppm, and the crystal grain boundaries that are formed have an ultrathin structure of about several nanometers, and it is considered that variations in the composition near the grain boundaries cannot be ignored. Therefore, in order to realize high characteristics, it is necessary to form such an ultrafine structure uniformly, in which the additives are dispersed as uniformly as possible in the raw material mixed powder or the pulverized powder after calcination. This is very important.

On the basis of such knowledge, the inventors have conducted various studies for improving the dispersibility of additives in order to realize the above object. As a result, the inventors have found that by controlling the average particle diameter of the additive, it is possible to uniformly disperse this trace component in the ferrite and improve the magnetic characteristics, and have reached the present invention.

That is, the present invention relates to a method for producing soft ferrite which comprises adding at least one additive as a sub-component to a basic component, and when the additive is added at the time of mixing raw materials, the additive is added. Is a method for producing soft ferrite, characterized in that the average particle size thereof is equal to or smaller than the average particle size of the raw material mixed powder (first invention), and the additive is used during pulverization of the calcined product. When added, this additive is a method for producing soft ferrite, characterized in that its average particle size is equal to or smaller than the average particle size of the pulverized powder after calcination of the calcinated product (second method). Invention), when the additive is added separately at the time of mixing the raw materials and at the time of pulverizing the calcined product, the average particle diameter of the additive is not more than the average particle diameter of the raw material mixed powder. With the calcination powder It is a manufacturing method of the soft ferrite, which comprises using an an average particle under size or less size of pulverized powder after (the third invention).

[0008]

The feature of the present invention is that, when the additive is mixed, the average particle size of the additive is adjusted to be smaller than the average particle size of the raw material mixed powder and / or the calcined product is pulverized, depending on the time of addition of the additive. The point is to control the size to be equal to or smaller than the average particle size of the subsequent pulverized ferrite powder (first invention, second invention, third invention). As a result, it becomes possible to uniformly disperse these additives in the ferrite and improve the magnetic characteristics. In this way, the reason for controlling the average particle size of the additive is that when the average particle size of the additive exceeds the average particle size of the mixed raw material powder or the average particle size of the pulverized ferrite powder after calcination, Even after the pulverization operation, the additives are not uniformly dispersed, and microscopically, there are parts with high and low concentrations of additives, which increases composition non-uniformity, so magnetic properties cannot be improved. Is.

In the method of the present invention, various powder raw materials are mixed, calcined and pulverized so as to have a predetermined component composition, then compression-molded according to a conventional method, and then fired to form soft ferrite. It can be manufactured. At this time, the additives are added at the time of mixing the raw materials and / or at the time of pulverizing the calcined product.

[0010]

【Example】

(Example 1) composition of the sintered body is _{Fe 2 O 3: 53.5 mol%} ,
The average particle diameters of Fe ₂ O ₃ : 0.8 μm, Mn ₃ O ₄ : 0.7 μm, and MnO: 37.5 mol% and ZnO: 9.0 mol%, respectively.
ZnO: 0.8 μm of the main raw material is mixed to make a raw material mixed powder, then the obtained raw material mixed powder is calcined, and then the obtained calcined product is crushed and dried to obtain an average particle size of 1.0 μm. A pulverized powder of ferrite was obtained. At this time, as an additive,
SiO ₂ = 150ppm, CaO = 350ppm, Nb ₂ O ₅ = 180ppm, SnO ₂ = 350pp
m, TiO ₂ = 900 ppm was added and blended at the time of mixing the raw materials and / or at the time of pulverizing the calcined product. Table 1 shows the addition timing and average particle diameter of these additives. The average particle size described in the examples is a measured value based on the air permeation method. Next, PVA as a binder was mixed with the obtained pulverized ferrite powder, and then molded into a ring shape and subjected to main firing to manufacture soft ferrite.

The core loss of the soft ferrite thus produced was measured at 500 kHz, 50 mT and 80 ° C., and the results are also shown in Table 1. The relationship between the average particle size of the additive (SiO ₂ ) and the core loss of soft ferrite is shown in FIG. As is clear from the results shown in FIG. 1, it was confirmed that the magnetic characteristics can be improved by making the additives finer. Further, when the average particle size of all the additives is equal to or less than the average particle size of the raw material mixed powder and / or the crushed ferrite powder, excellent magnetic properties can be obtained, but in other cases, the core loss is It was confirmed that it is necessary to control the average particle size of the additive to be equal to or smaller than the average particle size of the raw material mixed powder and / or the crushed ferrite powder.

[0012]

[Table 1]

(Example 2) The composition of the sintered body was Fe.₂O₃:
45.3 mol%, MnO: 20.2 mol%, MgO: 11.4 mol%, ZnO
 : The average grain size of Fe is 23.1 mol%.₂O
₃: 0.8 μm, Mn ₃O_Four : 0.7 μm, MgO: 0.6 μm, ZnO
 : Mixing main raw materials of 0.8 μm to form a raw material mixture,
Then, this raw material mixture is calcined, and then used as an additive.
SiO₂= 1000ppm, CaO = 3500ppm
Ferrai with an average particle size of 1.0 μm after crushing and drying
Obtained crushed powder. At this time, the average particle size of the additives used
It shows in Table 2. Next, in the same manner as in Example 1, soft blowjob
After manufacturing the ferrite, it was tested at 15.75kHz, 100mT, 100 ℃.
Aros was measured, and the results are also shown in Table 2. In Table 2
As is clear from the results shown, the Mn-Zn system ferrite of Example 1 was
As with the light, core loss (magnetism
It has been confirmed that it is possible to improve the physical characteristics).

[0014]

[Table 2]

Example 3 The composition of the sintered body was Fe ₂ O ₃ :
49.8 mol%, NiO: 35.7 mol%, ZnO: 14.5 mol% so that the average particle size of each is Fe ₂ O ₃ : 0.8 μm, NiO
: 0.7 μm, ZnO: 0.8 μm are mixed to form a raw material mixture, which is then calcined, and then V ₂ O ₅ = 1.4 wt% and CoO = 0.1 wt% are added as additives. After the addition and blending, the mixture was pulverized and dried to obtain a pulverized powder of ferrite having an average particle size of 1.1 μm. Table 3 shows the average particle diameters of the additives used at this time. Next, after manufacturing soft ferrite in the same manner as in Example 1, tan δ / μ at 5 MHz
_i was measured, and the results are also shown in Table 3. As is clear from the results shown in Table 3, it was confirmed that the magnetic properties can be improved in this example as well as the other examples by making the additives finer.

[0016]

[Table 3]

As described above, according to the present invention, the magnetic characteristics are excellent as compared with the case of using the additive having the average particle diameter exceeding the average particle diameter of the raw material mixed powder or the crushed ferrite powder. It is possible to stably manufacture soft ferrite. Moreover, the method of the present invention requires only a small amount of additive to obtain the same magnetic characteristics, and is therefore effective in reducing the raw material cost. The present invention is based on Mn-Zn series ferrite, Mn-Mg-Zn series ferrite, Ni-Zn series ferrite as shown in the examples.
It can be applied to all soft ferrites including system ferrites, and can be applied to all trace additives added to soft ferrites.

[0018]

As described above, according to the method of the present invention, it is possible to stably produce soft ferrite having excellent magnetic characteristics. As a result, if the material manufactured by the method of the present invention is used for the magnetic core of a switching power supply, etc., it is effective for increasing the efficiency and downsizing of the power supply and the like.

[Brief description of drawings]

FIG. 1 is a diagram showing the relationship between the average particle size of an additive (SiO ₂ ) and the core loss of soft ferrite.

Claims (3)

[Claims] 1. A base component containing at least 1 as a subcomponent.
In the method for producing a soft ferrite obtained by adding at least one kind of additive, when the additive is added at the time of mixing the raw materials, the average particle size of the additive is larger than the average particle size of the raw material mixed powder. A method for producing soft ferrite, characterized in that 2. A basic component and at least 1 as a secondary component.
In the method for producing a soft ferrite formed by adding at least one kind of additive, when this additive is added during pulverization of the calcined product, this additive has an average particle size of pulverized powder after calcination of the pulverized product. A method for producing soft ferrite, characterized in that a material having an average particle size or less is used. 3. A basic component, and at least 1 as a secondary component.
In the method for producing a soft ferrite formed by adding at least one kind of additive, when the additive is added separately at both the raw material mixing time and the calcination product crushing time, the additive is
The average particle size of the soft ferrite is characterized by using one having a size equal to or less than the average particle size of the raw material mixed powder, and one having a size equal to or less than the average particle size of the pulverized powder after calcination. Production method.