JPH08250318A - Frrite material and manufacture - Google Patents

Abstract

PURPOSE: To provide a ferrite material which is usable for various electronic parts and superior in magnetic characteristic and mechanical strength enough to eliminate the need of post-working by minimizing the dimensional variation and deformation in baking steps, irrespective of the size of the magnetic substance in the manufacturing method of the ferrite passage. CONSTITUTION: An Ni-Zn or Ni-Zn-Cu ferrite crystal grain powder 1 made by mixing and calcining ferrite raw powders, a filler powder 2 composed of oxides and metal powders constituting a ferrite, and at least one additive 3 0.05-10.0wt.% in total to supply 0 in the baking step are mixed and baked.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ferrite material used for various electronic parts and a method for manufacturing the same.

[0002]

2. Description of the Related Art Conventional ferrite materials as magnetic materials have been manufactured by the following two methods.

First, the first method is to pulverize a ferrite crystal grain agglomerate obtained by calcining a ferrite raw material powder, mix the obtained ferrite crystal grain powder with a binder, knead and granulate, and then form a predetermined shape. A molded body was prepared, and the molded body was subjected to main firing to obtain a ferrite material.

However, since the ferrite material produced by the first method undergoes firing contraction of 15 to 20% during main firing and is accompanied by firing deformation, grinding processing is required when obtaining a ferrite material having a complicated shape. I had a problem.

The second method is to form a ferrite material by crushing a ferrite crystal grain agglomerate obtained by calcining a ferrite raw material powder and dispersing and solidifying a mold resin in the obtained ferrite crystal grain powder. there were.

However, although the second method can obtain a ferrite material with high dimensional accuracy, since the binding property between the ferrite grain powders is insufficient as compared with the ferrite material produced by the first method, magnetic properties and It had a problem of poor mechanical strength.

In view of the above problems of the method for producing a ferrite material, in recent years, JP-A-58-135606 and JP-A-5-135606 have been used.
As in the method for producing a magnetic body described in Japanese Patent Application Laid-Open No. 0-50207, ferrite powders are sintered and bonded while suppressing volumetric shrinkage of a molded body by adding glass powder and firing the mixture to obtain sufficient mechanical strength and magnetic properties. And a method of producing a ferrite material described in JP-A-1-264959, the metal particles that are nitrided or oxidized during firing are mixed with the ferrite powder particles.
Attempts have been made to reduce the rate of dimensional change of the compact during sintering by binding the ferrite powder with metal particles that become nitrides or oxides and by reducing the voids between the particles of the ferrite powder.

[0008]

However, since all the ferrite materials obtained by the conventional techniques are non-magnetically bonded, there is a limit to the improvement of the magnetic properties, and the dimensional change of the compact is reduced during firing. Although you can
The dimensional change of 0.8% or more and the deformation during firing could not be suppressed. As a result, it is necessary to post-process the fired body formed by firing the molded body to obtain a ferrite material having a desired dimension, and post-working of the fired body is required to obtain a ferrite material with high dimensional accuracy. In order to achieve this, the dimensional change rate and the amount of deformation of the compact during firing must be further reduced.

The present invention has been made to solve the above problems, and
By adding an additive that supplies oxygen to the oxides and metal powders that make up the ferrite during the firing process, dimensional changes and deformation of the compact during firing do not occur, even though it has excellent magnetic properties. An object of the present invention is to provide a ferrite material with high dimensional accuracy that does not require post-processing of a bonded body and a method for manufacturing the ferrite material.

[0010]

In order to solve the above-mentioned problems, the present invention provides a Ni raw material prepared by mixing and calcining a ferrite raw material.
-Zn-based or Ni-Zn-Cu-based ferrite crystal grain powder, and oxides and metal powders forming ferrite are obtained by adding at least one additive that supplies oxygen in the firing process and firing. Ferrite material.

[0011]

In the molded body, the sintering reaction due to the diffusion of oxygen from the free surface proceeds, so that the central portion of the molded body has a slower sintering reaction rate than the free surface. Therefore, a large-sized compact and a ferrite material obtained by firing in a low oxygen partial pressure have insufficient oxygen diffusion toward the center of the compact,
It has an inhomogeneous fine structure and cannot obtain good magnetic properties and mechanical strength. Therefore, in the present invention, by mixing an additive that supplies oxygen in the firing process, the oxidation of the metal powder in the oxidation diffusion in the inside and the free surface of the molded body and the firing of the ferrite crystal grain powder, the oxide and the metal powder are performed. Since the binding reaction rate is at the same level and a uniform fine structure is formed, it is possible to obtain a ferrite material having a low shrinkage ratio and good magnetic properties and mechanical strength.

[0012]

First Embodiment Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic view showing a fine structure at the time of powder compression molding which is an embodiment of the present invention.
FIG. 3 is a schematic diagram showing sintering when surface diffusion and oxygen diffusion are promoted by additives.

As shown in FIG. 1, the magnetic substance is Fe ₂ O ₃ , N.
The compounding molar ratio of iO, ZnO and CuO is 48.5: 1.
An oxide that forms at least ferrite as a filling powder 2 that promotes surface diffusion in a ferrite crystal grain powder 1 obtained by mixing and calcining a ferrite raw material powder of 6.5: 28.5: 6.5 (mol%). NiO, ZnO,
A mixture of CuO powder and metallic Fe powder, which is a metal powder, in the same composition ratio as the ferrite crystal grain powder 1, 35 parts by weight with respect to the ferrite crystal grain powder 1, and an additive 3 for supplying oxygen in the firing process. As described above, 5.0 parts by weight of MnO ₂ was added and mixed, and the mixture was compression molded.

Further, in the method for producing a ferrite material as a magnetic material, the compounding molar ratio of Fe ₂ O ₃ , NiO, ZnO and CuO is 48.5: 16.5: 28.5: 6.5 (mo.
(1%) of the ferrite raw material powder is calcined at 1300 ° C. for 3 hours to form a ferrite crystal grain agglomerate, and a ferrite crystal grain powder 1 is prepared. The ferrite crystal grain powder 1 is used as a filling powder 2. A mixture of at least NiO, ZnO, CuO powders which are oxides forming ferrite and metal Fe powder which is a metal powder in the same composition ratio as the ferrite crystal grain powder 1 is 35 weight with respect to the ferrite crystal grain powder 1. Part, and 5.0 parts by weight of MnO ₂ , which is an additive 3 that supplies oxygen during the firing process, was mixed and mixed, and 6.0 (wt%) of a binder containing polyvinyl butyral as a main component was added to the mixture. After making the granules,
The granulated powder is pressurized to 3 (t / cm ² ) and the inner diameter is 12 m.
m, an outer diameter of 25 mm, and a thickness of 10 mm are formed, and the ring-shaped compact is fired at 1230 ° C. to obtain a ring-shaped ferrite material that is a ferrite crystal body.

The characteristics of the ferrite material having the above structure and the method of manufacturing the ferrite material will be described below. FIG.
As shown in (a), the voids 4 of the ferrite crystal grain powder 1
Since the filler powder 2 that promotes the surface diffusion of the ferrite crystal grain powder 1 and the additive 3 that supplies oxygen during the firing process are present in the above, the volume expansion of the filler powder 2 and the oxygen supply and additives from the free surface during the firing process are present. 3 supplies oxygen from the inside as shown by the arrow in FIG. 3 (a), the volume diffusion of the ferrite crystal grain powder 1 is limited, and at the same time, the metal in oxygen diffusion in the inside of the compact and the free surface is formed. Oxidation of the powder and the sintering reaction rate of the ferrite crystal grain powder 1 and the oxide constituting the ferrite and the metal powder are at the same level,
Since sintering proceeds under the control of volume diffusion as shown by the arrow in the sintering model of FIG. 3B, a ferrite crystal body having a uniform fine structure is formed. Therefore, according to the present invention, even though the ferrite crystal grain powder 1 is a self-shrinking substance, the substance is dominated by surface diffusion, and firing is performed while causing uniform oxygen diffusion on the free surface and inside of the molded body. Since the bonding progresses, the distance between particles does not change during sintering, and because it has a fine structure with few pores remaining in the crystal grains, sufficient magnetic characteristics and mechanical properties do not occur without dimensional fluctuation and deformation. A strong ferrite material can be obtained.

Comparison of the characteristics of the ferrite material (Sample 1) according to the first embodiment of the present invention with the conventional product (Table 1).
Is shown in.

[0017]

[Table 1]

Sample 1 is a ferrite material according to this embodiment,
Comparative product 1 is a ferrite material obtained by adding a binder to ferrite crystal grain powder, molding and firing, and comparative product 2 is a ferrite material in which an additive for supplying oxygen in the firing process is not mixed. When these ferrite materials were measured by an X-ray diffractometer, only peaks showing a spinel crystal structure were observed.

As is clear from Table 1, the magnetic characteristics,
The mechanical strength of Sample 1 was the same as that of Comparative Product 1. Further, in the dimensional change rate and the deformation amount, the comparative product 1 causes a dimensional shrinkage of about 3%, but the sample 1 and the comparative product 2 were able to obtain the ferrite material having substantially the same size as the molded body. The superiority of sample 1 over comparative product 1 is that a ferrite material that does not cause dimensional shrinkage is obtained, and the superiority of sample 1 over comparative product 2 is that a ferrite material with improved magnetic properties and mechanical strength is obtained. . As described above, in a molded body having a large size and shape such as Sample 1, in order to obtain a ferrite material having the same magnetic characteristics and mechanical strength as before without causing dimensional change after firing, MnO that supplies oxygen in the firing process. It was found that the addition of ₂ was effective.

(Second Embodiment) A second embodiment of the present invention will be described below. The ferrite material and its manufacturing method used in the second embodiment are substantially the same as those in the first embodiment, and will not be described. Hereinafter, the characteristics when the valence of the cation of the additive that supplies oxygen in the firing process is changed will be described. As the additive 3, a ferrite material obtained when at least one kind of MnO ₂ , Mn ₂ O ₃ , and Mn ₃ O ₄ is added in a total amount of 0.05 to 10.0 (wt%) (Samples 2 to 10) The characteristics are shown in (Table 2).

[0021]

[Table 2]

As is clear from (Table 2), MnO ₂ ,
Ferrite materials (Samples 2 to 8) obtained when at least one of Mn ₂ O ₃ and Mn ₃ O ₄ is added in a total amount of 0.05 to 10.0 (wt%) have small dimensional variation and deformation. Moreover, a ferrite material having excellent magnetic properties and mechanical strength could be obtained. Regarding sample 9 and sample 10, the oxygen supply was not appropriate and the sintering rate on the free surface and inside of the molded body became non-uniform, or due to the precipitation of different phases and the solid solution of defect spinel, the microstructure was formed. Although it has an influence and the dimensional variation is small, it is considered that the magnetic properties and mechanical strength are lowered. As in Example 1, Samples 2 to
When the ferrite material of No. 8 was measured using an X-ray diffractometer, only peaks showing a spinel crystal structure were observed.

The dimensional change rate, deformation amount, initial magnetic permeability, and mechanical strength (tensile strength) in Examples 1 and 2 were calculated and calculated as follows.

The dimensional change rate was calculated by measuring the outer diameters of the ring-shaped compact before heat treatment and the ring-shaped ferrite material after heat treatment, and calculating the ratio. The minus sign represents firing shrinkage. As the amount of deformation, the maximum value and the minimum value of the outer diameter dimension of the ring-shaped ferrite material after heat treatment were measured and the difference was calculated.

The initial permeability is measured by first winding one layer of insulating tape around the above-mentioned ring-shaped ferrite material, and then preparing a sample in which one layer of insulating copper wire having a wire diameter of 0.26 mm is evenly wound around the entire circumference. . Next, using an impedance analyzer, the self-inductance L was measured at 1 MHz at a measurement magnetic field strength of 0.8 (A / m), and the initial magnetic permeability was calculated.

The tensile strength was measured by passing two fine wires through the ring-shaped ferrite material once, fixing one of them, and then pulling the remaining one in the vertical direction at a speed of 5 mm / min or less. The tensile load at the moment of fracture was measured and determined.

[0027]

As described above, according to the present invention, a Ni-Zn system or N obtained by mixing and calcining ferrite raw material powders is used.
At least one additive that supplies oxygen during the firing process is added to the i-Zn-Cu-based ferrite crystal grain powder, the oxide powder that forms the ferrite, and the filling powder of the metal powder,
Since it is a ferrite material obtained by firing, the filler powder that promotes surface diffusion in the firing process suppresses the self-shrinking of the ferrite crystal grain powder, and of the metal powder in the oxidation diffusion on the inside and the free surface of the formed body. Oxidation and sintering reaction rate of ferrite crystal grain powder, oxide and metal powder are at the same level, and a uniform fine structure is formed, so there is little dimensional variation and deformation, and high dimensional accuracy without post-processing is required. It is possible to provide a ferrite material having a ferrite material and good magnetic properties and mechanical strength.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a microstructure during powder compression molding of a ferrite material according to an embodiment of the present invention.

FIG. 2 is a schematic diagram showing a fine structure of a ferrite material in an example of the present invention.

3 (a) and 3 (b) are schematic diagrams showing surface diffusion and sintering in which uniform oxygen diffusion occurs on the free surface and inside of the molded body.

[Explanation of symbols]

 1 Ferrite crystal grain powder 2 Filling powder 3 Additives 4 Voids

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasuyuki Aono 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (3)

[Claims] 1. A Ni-Zn-based or Ni-Zn-Cu-based ferrite crystal grain powder obtained by mixing and calcining a ferrite raw material powder, and a filling powder of an oxide and a metal powder forming ferrite in a firing process. A ferrite material obtained by adding at least one additive for supplying oxygen and firing the mixture. 2. MnO ₂ , Mn ₂ O ₃ and Mn ₃ as additives
The ferrite material according to claim 1, comprising at least one kind of O _4, and the total amount of addition is 0.05 to 10.0 (wt%). 3. Ni-Zn-based or Ni-Zn-Cu-based ferrite crystal grain powder obtained by mixing and calcining a ferrite raw material powder, and a filler powder of oxide and metal powder that constitute ferrite in a firing process. A ferrite obtained by mixing a powder and a binder to which at least one kind of additive for supplying oxygen is added, kneading and granulating, then forming a molded body of a predetermined shape, and firing the molded body. Material manufacturing method.