JPH04101401A - Ferrite magnetic material and its manufacturing method - Google Patents

Abstract

PURPOSE:To achieve an increase in initial permeability for high frequencies by mixing a high crystallinity ferrite powder with a glass powder containing at least In component, heating this mixture to a temperature at which a melting reaction occurs between this glass powder and indium oxide, and binding the high crystallinity ferrite powder with the glass material. CONSTITUTION:An Ni-Zn-Cu type ferrite powder is achieved by sintering a mixture containing Fe2O3, NiO, ZnO, and CuO at 1320 deg.C. X-ray analysis has shown that this ferrite magnetic powder has an adequate spinel ratio. A glass powder with In component is mixed together with this high crystallinity ferrite powder and, after this mixture forms particles, is compressed in a ring shape mold. This mold is placed in an electric furnace and is heat-processed at a temperature of 1200 deg.C to achieve a glass binding ring shape ferrite core.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is a highly crystalline ferrite powder used in various electronic components such as transformers, inductors, and magnetic heads, which is bonded and solidified with a glass material and has an ultra-low shrinkage rate. The present invention relates to a ferrite magnetic material and its manufacturing method.

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

When making a Ni-Zn-Cu-based ferrite magnetic material, the starting materials Fe2C)+, Nip, and Zn○CuO are mixed in a predetermined ratio, and in order to proceed with degassing and a certain degree of solid phase reaction, 700 to 1000 The compact is calcined at a temperature of about 100°C, then undergoes the steps of crushing, granulation, and molding, and the molded body is heated to 100°C at a temperature higher than the above calcining temperature in an appropriate atmosphere.
0~ ] A polycrystalline ferrite magnetic material is obtained by main firing at about 400°C.

Small amounts of various oxides are often added to the above starting materials in order to obtain desired magnetic properties. For example, JP-A-55-67565, JP-A-60210572
As shown in Japanese Patent Laid-Open No. 63-260006, many machining tests have been carried out, including the addition of various oxides.

Problems to be Solved by the Invention In the ferrite obtained by the conventional technology, a firing shrinkage of several tens of percent occurs in the main firing, which causes distortion and cracks in the shape of the fired body.

Therefore, it was possible to suppress the firing shrinkage rate to a few percent in the following manner. That is, after mixing highly crystalline ferrite powder that has been sufficiently spinelized at high temperature and glass powder with a softening point lower than this firing temperature, and molding this,
An ultra-low shrinkage ferrite magnetic material in which highly crystalline ferrite powder was bonded with glass was obtained by heat treatment at a temperature above the softening point of the glass powder and below the sintering temperature of the highly crystalline ferrite powder.

However, since the above-mentioned ultra-low shrinkage ferrite 1-VA material has a small firing shrinkage rate, the density of the fired material is lower than that of conventional ferrite magnetic material, that is, the initial magnetic permeability is relatively low in the entire frequency band. It has the following drawbacks.

The present invention aims to increase the initial permeability of an ultra-low shrinkage ferrite magnetic material, particularly in a high frequency band.

Means for Solving the Problems In order to solve the above problems, the present invention uses a mixture of a highly crystalline ferrite powder and a glass powder containing at least an In component, or a mixture of a highly crystalline ferrite powder, a glass powder, and a powdered mixture. An ultra-low shrinkage ferrite material having a structure in which a mixture of indium oxide and indium oxide is heated at a temperature higher than the temperature at which a melting reaction occurs between the glass powder and indium oxide, and the above-mentioned highly crystalline ferrite powder is bound with a glass material. That is.

Function As described above, the In 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. It is thought that this results in a structure in which a large amount of In is present on the outer surface of the highly crystalline ferrite powder, resulting in a high initial magnetic permeability in a high frequency band.

Note that similar results were obtained even when using a mixture of highly crystalline ferrite powder, glass powder, and indium oxide because the melting reaction between the glass powder and indium oxide occurred first, and the glass containing the In component It is thought that this is because a process occurs in which the same state as when the In components are mixed, and then a part of the In component diffuses to the outer surface of the ferrite powder.

Example Examples of the present invention will be described below.

That is, as shown in FIG. 1, the present invention binds a highly crystalline ferrite powder 1 having a large amount of In component on its outer surface with a glass material 2 that softens and melts at a temperature below the firing temperature of this highly crystalline ferrite powder 1. The structure will be as follows. In the figure, 3 is a void, and 4 is a bore in the highly crystalline ferrite powder 1.

Specifically, highly crystalline ferrite powder 1 and glass powder containing an In component are thoroughly mixed. In some cases,
For example, when it is desired to contain a large amount of In component to the extent that it is difficult to make glass, highly crystalline ferrite powder 1, glass powder, and powdered indium oxide are thoroughly mixed, and this mixture is granulated and pressure-molded. By softening and melting the glass powder mixed between the highly crystalline ferrite powders 1 in this compact, the highly crystalline ferrite powders 1 are bound and solidified by the glass material 2 to form a ferrite magnetic body. However, when mixing powdered indium oxide, it is necessary to heat the mixture to a temperature at which the glass powder and indium oxide melt and react.

The highly crystalline ferrite powder 1 used here is sufficiently spinelized by high-temperature firing, and is usually 1000
It is preferable that the material be fired at a temperature of ℃ or higher.

When obtaining a soft ferrite 6n material, the smaller the coercive force Hc of the highly crystalline ferrite powder, the better, so the larger the size of the magnetic powder, the better. Actually 100
A diameter of up to 200 μm is suitable.

Next, a glass material 2 that binds the highly crystalline ferrite powder 1 is
The softening temperature may be lower than the heat treatment temperature, but considering the application of the ferrite magnetic material according to the present invention, it is desirable that the lower limit is 300°C or higher from the viewpoint of heat resistance. The amount of glass powder added to highly crystalline Ferrite I powder 1 is 0.
If 3 to 30 wt% is less than 0.3 wt%, 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 greater than 30 wt%, the binding force will be sufficiently strong, but since the amount of non-magnetic material will increase, the magnetic properties as a ferrite magnetic material will be significantly deteriorated, which is not preferable. Note that In2O3 was used as indium oxide in the experiment, but I
Any oxide containing the n component may be used.

Hereinafter, specific examples will be described.

Example 1 The blending molar ratio of FezO3, NiO, Zn○ and CuO is 4
A mixture consisting of 9.0: 17.0: 30.0: 4.0, and l nzoi of 0.0 for the above mixture.
The mixtures to which 9 parts by weight were added were separately calcined at 1320°C for 6 hours to prepare two types of Ni-Zn-Cu based ferrite powders having an average particle size of 7 μm. As a result of X-ray analysis, both types showed sharp spinel structure diffraction lines characteristic of soft ferrite, indicating that they are highly crystalline ferrite magnetic powders.
In other words, it was confirmed that the spinel ratio was sufficiently advanced.

On the other hand, an alkali-free product containing no In component is made by adding 3 wt% of In, O,, to lead silicate glass, heating and melting it at 800°C, cooling it, and creating an In component with an average particle size of 1 μm. A glass powder containing the following was prepared. 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.

3 parts by weight of the above-mentioned glass powder containing 3.0 wt% In component was mixed with the above-mentioned highly crystalline ferrite powder without addition of In2O, and the mixture was granulated and then heated under a pressure of 3 tons.
On/c go, inner diameter 7mm, outer diameter 12mm.

A ring-shaped molded product with a thickness of 3 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 +nz03 is not added, glass powder containing no In component, and In2
O, were well mixed at a weight ratio of 100:2.91:0.09, and from this mixture a glass-bonded ring-shaped ferrite core was obtained under the same conditions as Inventive Product 1 (Inventive Product 2).
).

For comparison, inventive product 1 was prepared from a mixture obtained by adding 3.0 parts by weight of alkali-free lead silicate glass that does not contain In to the above-mentioned highly crystalline ferrite powder to which InzO3 was added.
A glass-bonded ring-shaped ferrite core was obtained under the same conditions as (comparison product).

Invention product 13 Invention product 2. Comparative products have exactly the same composition. As shown in Table 1, the firing shrinkage rate was less than 1%, and the density of the fired bodies did not differ enough to affect the initial magnetic permeability. Moreover, no difference is observed in scanning electron microscopy of these microstructures.

Table 1 The frequency characteristics of the initial magnetic permeability of these materials are shown in Part 2.

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

Compared to the comparative product, the difference in initial magnetic permeability is large in the frequency band of 2 MHz or higher, and at 7 MHz, an increase in initial magnetic permeability of 50% is observed.

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 heat-treated at 1200'C. did. The temperature profile at that time was such that the heating rate was 240'C/lh, the high temperature rate was 300°C/h, and the holding time at 1200°C was 300 to 180 minutes. The characteristics of the obtained magnetic material are shown in the third article. There was almost no difference in properties between Inventive Product 1 and Inventive Product 2, and compared to the comparative product, a product with high initial magnetic permeability was obtained at any holding time. However, as the holding time increases, its properties become closer to those of the comparative product (the microstructure was observed using a scanning electron microscope, but no structural changes such as ferrite grain growth were observed. In component exists on the outer surface of the crystalline ferrite powder, and as the retention time increases,
The In component diffuses into the highly crystalline ferrite powder,
This is thought to mean that the composition distribution is relatively close. The features of the present invention are most apparent when the holding time is 60 minutes or less.

Example 3 The blending molar ratio of FezOi, NiO, ZnO, and CaO is 4
9.0 : ] 7.0 : 30.0 : 0 to 0.15 overlapping parts of ■n203 were added to the starting mixture consisting of 4.0, mixed thoroughly, and then calcined at 1320'C for 6 hours to obtain an average particle size of A 7oIIm Ni-Zn-Cu-based soft ferrite 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, that is, spinelization had progressed sufficiently.

In contrast to the above highly crystalline ferrite powder in which In, 03 was not added to the starting mixture, the alkali-free powder containing no In component contained 3 parts by weight of lead silicate glass powder and powdered Inz.
A ring-shaped ferrite core was prepared from a mixture to which 0.15 parts by weight of O3 was added under the same conditions as in Example 1 (product of the present invention).

On the other hand, an alkali-free mixture containing no In component was prepared by adding 3 parts by weight of lead silicate glass powder to the above-mentioned highly crystalline ferrite powder in which Tn203 was added to the starting mixture under the same conditions as in Example 1. A ring-shaped ferrite core was created (comparison product). The characteristics of each are shown in FIG.

The products of the present invention exhibit high initial magnetic permeability at all amounts of TnzOz added. If the amount added is greater than 0.09 parts by weight, the increase in initial magnetic permeability will be saturated at 7 MHz and will decrease at IMHz, so it is desirable that TnzO3 be added in an amount of 0.09 parts by weight or less.

Here, powdered I 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 r+z○3 is made of In component of alkali-free lead silicate glass.

In the above examples, the initial magnetic permeability was measured in accordance with the JIS standard (C2561), and after wrapping one layer of insulating tape around the ring-shaped ferrite core, the wire diameter was 0.26 mm.
A sample was prepared by wrapping an insulated copper wire of φ in one layer around the entire circumference. Next, the self-inductance L at 10 kHz to 10 MHz was measured with a mask well ring at a measurement magnetic field strength of 0.8 (A/m) or less, and the initial magnetic permeability was calculated from the self-inductance L.

Effects of the Invention As described above, according to the present invention, in a glass bonded ultra-low shrinkage ferrite magnetic material using highly crystalline ferrite powder, a structure in which an In component is present on the outer surface of the highly crystalline ferrite powder is obtained. As a result, it becomes a magnetic material with improved initial magnetic permeability in a high frequency band, and can exhibit excellent effects as a useful electronic component material used in various magnetic application products.

[Brief explanation of drawings]

Figure 1 is a schematic diagram of the microstructure showing an example of the ferrite magnetic material of the present invention, Figure 2 is a frequency characteristic diagram of initial magnetic permeability, and Figure 3 is a diagram of the frequency characteristics of the ferrite magnetic material of the present invention. A characteristic diagram showing the relationship between retention time and initial permeability, Figure 4 is InzO
3 is a characteristic diagram showing the relationship between the blending amount of No. 3 and the initial magnetic permeability. FIG. l...High crystal ferrite powder, 2...
Glass material, 3... air gap, 4... bore.

Claims (3)

[Claims] (1) Ni-Zn with sufficiently advanced spinel ratio by high-temperature firing
In is added to the outer surface from the inside of the system or Ni-Zn-Cu system.
A ferrite magnetic material made by bonding highly crystalline ferrite powder containing many components with a glass material that has a lower softening point than the fired ferrite powder. (2) Ni-Zn with sufficiently advanced spinel ratio by high-temperature firing
After mixing and granulating a highly crystalline ferrite powder based on Ni-Zn-Cu based or Ni-Zn-Cu based glass powder having a softening point lower than that of the fired ferrite powder and containing at least an In component, the mixture is pressure-molded. . A method for producing a ferrite magnetic body, in which glass powder mixed in the compact is softened and melted by heat treatment at a temperature below the firing temperature of the highly crystalline ferrite powder, and the highly crystalline ferrite powder is bound with a glass material. (3) Ni-Zn that has been sufficiently transformed into spinel by high-temperature firing
or Ni-Zn-Cu based highly crystalline ferrite powder, glass powder having a softening point lower than that of the fired ferrite powder, and powdered indium oxide are mixed and granulated, and a mixture is pressure-molded. A method for producing a ferrite magnetic material, which comprises binding highly crystalline ferrite powder with a glass material by heat treatment at a temperature above the melting reaction temperature of the glass powder and indium oxide and below the firing temperature of the above-mentioned highly crystalline ferrite powder.