JPH03190204A - Ferrite magnetic material and manufacture thereof - Google Patents

Abstract

PURPOSE:To obtain ferrite magnetic material having low loss by heat-treating a mixture of ferrite powder high in crystallizability and glass powder containing at least Co component in a specific temperature range, and binding the ferrite powder with the glass. CONSTITUTION:Ferrite powder 1 of high crystallizability and glass powder 2 containing Co component are mixed well, the mixture is granulated and pressure molded, and the powder 2 mixed in the powder 1 during molding is softened and melted so that the powder 1 is bound with the powder 2 to be solidified. Since treating time is short at a stage in which the Co component contained in the material 1 of the binding material of the powder 1 is diffused in the powder 1 during heat treating, a structure in which the much component exists in the bound part without sufficient diffusion is provided. Thus a magnetic material accurate in size, low in loss and high in permeability is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is applicable to ferrite magnetic materials used in transformers, inductors,
The present invention relates to a ferrite magnetic material with an ultra-low shrinkage rate made by bonding and solidifying highly crystalline ferrite powder with a glass material, which is used in various electronic components such as magnetic heads, and a method for manufacturing the same.

BACKGROUND OF THE INVENTION Conventional methods for producing ferrite magnetic materials are mostly based on powder metallurgy, that is, sintering methods that require powder molding and high-temperature firing steps.

When producing a Ni-Zn-Cu-based ferrite magnetic material, starting materials Fe2e3. Nip, ZnO.

CuO is blended in a predetermined ratio, and calcined and pulverized at about 700 to 1000°C (referred to as calcined powder) and granulated in order to promote degassing and a certain degree of solid phase reaction.

After the process of molding, the molded body is heated to a temperature of 1000 to 1400°C, which is higher than the above-mentioned pre-firing temperature, in an appropriate atmosphere.
A polycrystalline ferrite magnetic material is obtained by main firing at a certain temperature. In order to obtain the desired magnetic properties, small amounts of various oxides are often added to the above starting materials.

It is known that adding a small amount of CO2O3 is effective when trying to obtain a low-loss Ni-Zn-Cu-based ferrite magnetic material. However, generally, the addition of CO2O3 also causes a significant decrease in magnetic permeability.

Therefore, as described in Japanese Patent Publication No. 35-1576, for example, Bi2O,+ is added at the same time as CO2O3 to suppress the decrease in magnetic permeability and obtain a ferrite magnetic material with low loss and high magnetic permeability. Similar to Bi2O3, V2O5
It is also well known that addition of a small amount of PbO is also effective in improving magnetic permeability. This effect is said to be attributable to the fact that the addition of each activates the ferrite grain boundaries, promotes the sintering reaction, advances shrinkage and densification, and in other words, makes the ferrite highly crystallized.

Problems to be Solved by the Invention Ferrite magnetic materials obtained by conventional techniques have the disadvantage that shrinkage of several lθ% occurs during main firing.

Therefore, it was possible to obtain an ultra-low shrinkage ferrite magnetic material as follows. That is, a high-crystalline ferrite powder that has been sufficiently ferrite-ized at a high temperature is mixed with a glass powder having a softening point lower than this firing temperature, and the firing temperature is set at a temperature equal to or higher than the softening point temperature of this glass powder and the above-mentioned high-crystalline ferrite powder. By heat-treating in the following range, we were able to bind highly crystalline ferrite powder to glass and suppress the shrinkage rate to a few percent.

However, in the above-mentioned ultra-low shrinkage ferrite magnetic material, the ferrite powder used is sufficiently highly crystallized by high-temperature firing, so the conventional addition of a small amount of oxide for high magnetic permeability has almost no effect.

Therefore, although the conventional combination of oxides such as CO2O3 and Bi2O3 for high magnetic permeability achieves low loss, it is not possible to suppress the significant decrease in magnetic permeability, and It has been difficult to obtain low shrinkage ferrite magnetic materials.

An object of the present invention is to provide an ultra-low shrinkage ferrite magnetic material with low loss and a method for manufacturing the same.

Means for Solving the Problems In order to solve the above problems, the present invention provides a mixture of a highly crystalline ferrite powder and a glass powder containing at least a Co component, or a mixture of a highly crystalline ferrite powder, a glass powder, and a cobalt oxide. is heated at a temperature higher than the temperature at which the melting reaction between the glass powder and cobalt oxide occurs and lower than the firing temperature of the highly crystalline ferrite powder,
This is an ultra-low shrinkage ferrite magnetic material with a structure in which highly crystalline ferrite powder is bonded with glass.

Function As described above, the Co component contained in the glass material, which is the binder for the highly crystalline ferrite powder, diffuses into the highly crystalline ferrite powder during the heat treatment, and because the treatment time is short, it is sufficiently diffused. This is thought to result in a structure in which a large amount of Co component is present in the bonded portion, resulting in a behavior different from that of the conventional method in which loss is reduced despite a small decrease in magnetic permeability.

Note that similar results were obtained when using a mixture of highly crystalline ferrite powder, glass powder, and cobalt oxide because the melting reaction between the glass powder and cobalt oxide occurred first.
This is thought to be due to a process in which the state is the same as when glass containing a Co component is melted, and then a part of the Co component is diffused into the ferrite powder.

Example Examples of the present invention will be described below.

That is, as shown in FIG. 1, the present invention has a structure in which a highly crystalline ferrite powder 1 is bound with a glass material 2 containing a Co component that softens and melts at a temperature below the firing temperature of this highly crystalline ferrite powder. It is something. In addition, 3 in the figure is a void,
4 is a bore in the highly crystalline ferrite powder l.

Specifically, highly crystalline ferrite powder 1 and glass powder containing a Co component are thoroughly mixed. In some cases,
For example, in the case where it is desired to contain a large amount of Co component so as to make glass production difficult, highly crystalline ferrite powder 1, glass powder, and powdered cobalt oxide are thoroughly mixed. After granulating and press-molding this mixture, the glass powder mixed between the high-crystalline ferrite powders 1 in this molded body is softened and melted to bind the high-crystalline ferrite powders 1 with the glass material 2. A magnetic material that has been solidified. However, when mixing powdered cobalt oxide, it is necessary to heat it to a temperature at which the glass powder and cobalt oxide melt and react.

The highly crystalline ferrite powder 1 used here is one that has been sufficiently ferrite-formed by high-temperature firing, and is preferably one that has been fired at 900° C. or higher.

If you want to obtain a soft ferrite magnetic material, the smaller the coercive force Hc of the highly crystalline ferrite powder 1, the better, so the larger the size of the magnetic particles, the better. However, on the other hand, the packing density of the highly crystalline ferrite powder 1 decreases. So it's actually 100
A diameter of up to 200 μm is suitable.

Next, the glass softening temperature for binding the highly crystalline ferrite powder 1 may be lower than the heat treatment temperature, but considering the application of the ferrite magnetic material according to the present invention, the lower limit is 300°C or higher from the viewpoint of heat resistance. This is desirable. The amount of glass powder added to high crystalline ferrite powder 1 is 0.3 to 3Qw
If the t% is less than Q, 3wt%, the binding effect of the highly crystalline ferrite powder 1 is small and mechanical strength cannot be ensured. On the other hand, if the amount of glass is more than 30 wt%, the binding force will be sufficiently strong, but the non-magnetic amount will increase, so the magnetic properties as a ferrite magnetic material will be significantly deteriorated, which is not preferable.

Note that similar results can be obtained even if the cobalt oxide used changes the valence of Co, such as CO2031Coo.

Hereinafter, specific examples will be described.

(Example 1) The molar ratio of Fe203, NiO, ZnO, and CuO is 4
A mixture consisting of 8.5:15.3:32.2:3.5 and a mixture obtained by adding 0.2 parts by weight of CO2O3 to the above mixture were separately calcined at 1320°C for 6 hours to obtain Ni- Two types of Zn-Cu based ferrite final firing components were prepared. As a result of X-ray analysis, sharp spinel structure diffraction lines characteristic of soft ferrite were obtained for both types.
It was confirmed that the powder was a highly crystalline ferrite magnetic powder.

On the other hand, alkali-free glass containing no Co component is made by adding 6.6 parts by weight of CO2O3 to lead silicate glass, heating and melting it at 800°C, and then rapidly cooling it. Prepared powder. As a result of X-ray analysis, a diffraction pattern unique to glass was obtained, confirming that sufficient reaction had occurred and vitrification had occurred.

The above-mentioned highly crystalline ferrite powder to which no Co2O3 was added was thoroughly mixed with 3.2 parts by weight of the above-mentioned glass powder containing the Co component, and after granulating the mixture, 3 tons
/cffl pressure, inner diameter 7mm, outer diameter 12mm, thickness 3
A ring-shaped molded product with a diameter of mm was created.

This molded product was placed in an electric furnace and heat-treated in air at 1200° C. for 60 minutes to obtain a glass-bonded ring-shaped ferrite core (Product 1 of the present invention).

On the other hand, the above-mentioned highly crystalline ferrite powder to which Co2O3 is not added, glass powder containing no Co component, and CO2
O3 was thoroughly mixed in a weight ratio of 100:3:0.2, and a glass-bonded ring-shaped ferrite core was obtained from the mixture under the same conditions as Inventive Product 1 (Inventive Product 2).

For comparison, inventive product 1 was prepared from a mixture in which 3.0 parts by weight of alkali-free lead silicate glass containing no Co component was added to the above-mentioned highly crystalline ferrite powder to which CO2O3 was added.
A glass-bonded ring-shaped ferrite core was obtained under the same conditions as (comparison world).

Invention product 19 Invention product 2. Comparative products have exactly the same composition. Moreover, no difference is observed when observing these fine structures with a scanning electron microscope.

The properties of these materials are shown in Table 1.

Table 1 Product 1 of the present invention and Product 2 of the present invention have almost the same characteristics.

Although the loss (tan δ) was reduced to 50% or less compared to the comparative product, the magnetic permeability was nearly double, and a ferrite magnetic material with low loss, high magnetic permeability, and an ultra-low shrinkage rate was obtained.

(Example 2) Three ring-shaped molded bodies created under the same conditions as Example 1 (one each of the present invention product, the present invention product 2, and the comparison product) were placed in an electric furnace and heated at 1200°C. Processed. The temperature profile at that time was a heating rate of 170°C/1h, a cooling rate of 300°C/h, and a holding time of 30°C at 1200°C.
It took ~180 minutes. The characteristics of the obtained ferrite magnetic material are shown in FIG. There is almost no difference in the properties between Invention Product 1 and Invention Product 2, and compared to the comparative product, the loss (tan δ) is small and the magnetic permeability (μ) is large at all holding times. ing. However, as the retention time increases, the characteristics become closer to those of the comparative product.

The microstructure was observed using a scanning electron microscope, but no structural changes such as the ferrite particle size were observed. This is thought to mean that as time increases, the Co component diffuses into the highly crystalline ferrite powder, and the composition approaches the comparative product. From FIG. 2, many of the features of the present invention appear when the holding time is 120 minutes or less.

(Example 3) FezO:+, NiO, ZnO, and CuO molar ratio is 48
．． 0 to 0.5 parts by weight of CO2O3 was added to a starting mixture consisting of 5:15.3:32.2:3.5, mixed well, and then calcined at 1320°C for 6 hours to obtain an average particle size of 70 μm.
A Ni-Zn-Cu based soft ferrite main fired powder was prepared. As a result of X-ray analysis, sharp spinel structure diffraction lines characteristic of soft ferrite were obtained, confirming that the powder was a highly crystalline ferrite magnetic powder.

For the above highly crystalline ferrite powder where no CO2O3 was added to the starting mixture, powdered CO2O3 was added from 0 to 0.5.
A ring-shaped ferrite core was prepared under the same conditions as in Example 1 from a mixture in which 3 parts by weight of alkali-free lead silicate glass powder containing no Co component was added to the mixture. (Product of the present invention).

On the other hand, to the above-mentioned highly crystalline ferrite powder obtained by adding CO2O3 to the starting mixture, an alkali-free product containing no Co component was prepared by adding 3 parts by weight of lead silicate glass powder to the starting mixture. A ferrite core with a similar shape was created (comparison product).

The characteristics of each are shown in Figure 3.

It is shown that the product of the present invention is a low-loss, high-permeability magnetic material at all amounts of CO2O3 added.

Here, powdered CO mixed with highly crystalline ferrite powder
It is clear from Example 1 that the same characteristics can be obtained even when part or all of 2O3 is replaced by the Co component of an alkali-free lead silicate glass.

In the above example, the magnetic permeability was measured in accordance with the JIS standard (C2561). First, a layer of insulating tape was wrapped around the ring-shaped ferrite core, and then the wire diameter was 0.26 mr.
A sample was prepared in which an oφ insulated copper wire was wound in one layer over the entire circumference. Next, this self-inductance L at I MHz
and Q at 500 kHz was measured with a Maxwell bridge at a magnetic field strength of 0.8 (A/m) or less,
Magnetic permeability was calculated from this self-inductance L. The loss (tanδ) was the reciprocal of Q.

Furthermore, the shrinkage rate was measured by measuring the outer diameter of the ring-shaped molded product before heat treatment and the ring-shaped ferrite core after heat treatment.
The dimensional shrinkage rate before and after heat treatment was calculated.

Effects of the Invention As described above, according to the present invention, a glass-bonded low-shrinkage ferrite magnetic material using highly crystalline ferrite powder has a structure in which the Co component is localized in the bonded portion.
It is a magnetic material with good dimensional accuracy, low loss, and high magnetic permeability, making it highly effective as a useful electronic component and material used in various magnetic application products.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram of a microstructure showing an example of the ferrite magnetic material of the present invention, and Fig. 2 is a schematic diagram of a microstructure showing an example of the ferrite magnetic material of the present invention.
Holding time and loss (tanδ) at 200℃, magnetic permeability (μ
), and Figure 3 shows the relationship between Co o2 @ compounding amount and loss (tan δ). It is a characteristic diagram showing the relationship of magnetic permeability (μ). 1... Highly crystalline ferrite powder, 2...
・Glass material, 3... air gap, 4... bore.

Claims (3)

[Claims] (1) Ni-Z that has been sufficiently converted into ferrite by high-temperature firing
Highly crystalline n-based or Ni-Zn-Cu-based ferrite powder is bound with a glass material that has a lower softening point than the fired ferrite powder, and the Co component is added to the bound part rather than within the highly crystalline ferrite grains. Ferrite magnetic material with more. (2) Ni-Z that has been sufficiently converted into ferrite by high-temperature firing
A mixture of n-based or Ni-Zn-Cu-based highly crystalline ferrite powder and glass powder having a softening point lower than that of the fired high-crystalline ferrite powder and containing at least a Co component is added. After pressure molding, the glass powder mixed in the molded body is softened and melted by heat treatment at a temperature lower than the firing temperature of the high crystalline ferrite powder, and the high crystalline ferrite powder is bonded with the glass material. Production method. (3) Heat treatment temperature of a mixture of Ni-Zn-based or Ni-Zn-Cu-based highly crystalline ferrite powder, glass powder, and powdered cobalt oxide at a temperature higher than the temperature at which the glass powder and cobalt oxide melt and react. 3. The method for producing a ferrite magnetic material according to claim 2, wherein the firing temperature is lower than or equal to the firing temperature of the highly crystalline ferrite powder.