JPH0562118A - Manufacture of joined ferrite material - Google Patents

Abstract

PURPOSE:To integrally join a single-crystal ferrite material with a polycrystalline ferrite material at a low temperature in a short time so as to improve the productivity and reduce the cost of a joined ferrite material and, at the same time, to improve the controllability of the interface between both ferrite materials. CONSTITUTION:A single-crystal ferrite material and polycrystalline ferrite material are integrally jointed to each other by a discharge plasma sintering method while the joining surfaces of both materials are closely adhered to each other. It is possible to put coprecipitated ferrite power between the joining surfaces of the materials.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a bonded ferrite material used in, for example, a composite magnetic head,
In particular, the present invention relates to a method for manufacturing a novel bonded ferrite material that performs thermocompression bonding at a low temperature.

[0002]

2. Description of the Related Art In recent years, in magnetic heads such as video heads, in order to reduce sliding noise and improve the CN ratio, single crystal ferrite materials and polycrystalline ferrite materials have been used in comparison with conventional single crystal ferrite heads. It is being switched to a composite type magnetic head made of a ferrite material.

This composite magnetic head has a simple structure in which a single crystal ferrite having a high saturation magnetic flux density is arranged on the front gap side and a polycrystalline ferrite having a high magnetic permeability is arranged on the back gap side. It has an advantage that high density recording is possible and excellent electromagnetic conversion efficiency is exhibited.

As a joining ferrite material used as a magnetic core in such a composite magnetic head, for example, a single crystal ferrite material and a polycrystalline ferrite material are prepared, respectively, and then the two are integrally bonded by thermocompression bonding. Manufactured by. As a method for the above-mentioned thermocompression bonding, a hot-press firing method in which a heat treatment is performed while applying pressure from the outside is adopted.

[0005]

However, in order to bond and integrate the single crystal ferrite material and the polycrystalline ferrite material by the conventional hot press firing method, the solid state reaction becomes insufficient at low temperature treatment, and the bonding state becomes poor. Because it gets worse
Normally, the firing temperature is 1000 ° C or higher, preferably 1200
It is necessary to carry out at a considerably high temperature of ℃ or more. When the heat treatment is performed at a high temperature in this way, the phenomenon that single crystallization or crystal growth of the polycrystalline ferrite material occurs at a part of the interface between the single crystal ferrite material and the polycrystalline ferrite material, and the interface moves randomly Often observed. As a result, there arises a problem that the controllability of the interface is deteriorated such that a large undulation occurs on the interface, which causes sliding noise.

To solve this problem, for example, K ⁺ , Rb ⁺ ,
A method of controlling the interface by adding Cs ^+, etc.
As described in JP-A-137103, at a temperature equal to or lower than the temperature at which the polycrystalline ferrite material mass-transfers with a joining aid such as sodium silicate interposed at the interface between the single crystal ferrite material and the polycrystalline ferrite material. Although a method of heat treatment has been proposed, it is hard to say that it is a satisfactory method in terms of productivity and cost.

Therefore, the present invention has been proposed in view of such circumstances, and it is an object of the present invention to provide a method for producing a bonded ferrite material which can improve productivity and reduce cost. To aim.

[0008]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies as a result of achieving the above-mentioned object, and as a result, adopted a discharge plasma sintering method when bonding a single crystal ferrite material and a polycrystalline ferrite material. Then, they found that they can be joined and integrated at a relatively low temperature, and completed the present invention.

That is, the present invention is characterized in that in the method for producing a bonded ferrite material obtained by bonding a single crystal ferrite material and a polycrystalline ferrite material, the bonding is performed by a spark plasma sintering method. Further, the present invention is characterized in that a coprecipitated ferrite powder is interposed at the bonding interface between the single crystal ferrite material and the polycrystalline ferrite material during bonding.

In the present invention, the discharge plasma sintering method is used as the thermocompression bonding means for joining and integrating the single crystal ferrite material and the polycrystalline ferrite material. This spark plasma sintering method (also called plasma activation sintering method) is a method for holding a mirror-polished single crystal ferrite material and a mirror-polished polycrystalline ferrite material at a predetermined pressure and a predetermined heating temperature for a short time. By doing so, the single crystal ferrite material and the polycrystalline ferrite material are joined by a solid phase reaction. At this time, the heating temperature is preferably 900 ° C. or lower, and more preferably 900 ° C. Further, the holding time may be an extremely short time of about 3 to 5 minutes. By adopting such a discharge plasma sintering method, 900 ° C
The above-mentioned joining and integration can be achieved at such a low temperature, and productivity can be improved and cost can be reduced.

Further, when the single crystal ferrite material and the polycrystalline ferrite material are joined by this discharge plasma sintering method, it is desirable to perform a plasma activation treatment or the like as a pretreatment of the thermocompression bonding step.

Further, at the time of joining, a coprecipitated ferrite powder synthesized by a coprecipitation reaction in an aqueous solution and having the same composition as these ferrite materials, or a coprecipitated ferrite powder, at the joint interface between the single crystal ferrite material and the polycrystalline ferrite material. By interposing the dispersed magnetic paste, it becomes possible to join and integrate at a low temperature of 600 to 700 ° C. At this time, the coprecipitated ferrite powder or magnetic paste may be interposed at the bonding interface between the single crystal ferrite material and the polycrystalline ferrite material by a method such as coating. Further, the coprecipitated ferrite powder or the magnetic paste may be applied to only one of the single crystal ferrite material and the polycrystalline ferrite material, or may be applied to the bonding interface between the two.

[0013]

The discharge plasma sintering method is a novel sintering method utilizing discharge plasma in the sintering reaction. In carrying out the sintering method, the sample 2 is subjected to heat resistance and impact resistance as shown in FIG. 1, for example. It is filled in a cylindrical container 1 having the same, electrodes 3 having protrusions are fitted and inserted into openings at both ends of the container 1, and a predetermined pressure is applied to the sample 2.

When a voltage is directly applied between the sample single crystal ferrite material and the polycrystalline ferrite material, the surface particle 4 gap of the sample 2 (that is, the single crystal ferrite material and the polycrystalline ferrite material gap, or the coprecipitated ferrite material). A discharge is generated in the powder particle space) and plasma is generated. The impact of this plasma evaporates and removes the oxide film and adsorbed gas impurities on the surface of the single crystal ferrite material and the polycrystalline ferrite material, and at the same time, heats the surface of the single crystal ferrite material and the polycrystalline ferrite material. And energy of strain is accumulated and activated. As a result, many vacancies are generated, the diffusion constant of atom transfer is increased to several hundred times the usual value, and Joule heat is generated between the single crystal ferrite material and the polycrystalline ferrite material, resulting in active thermal diffusion. Occur.
Therefore, even at a low temperature of about 900 ° C. (about 600 to 700 ° C. when the coprecipitated ferrite powder is interposed), a solid-phase reaction occurs at the interface between the single crystal ferrite material and the polycrystalline ferrite material, and both of them Joined and integrated. Therefore, the crystal growth and single crystallization of the polycrystalline ferrite material are suppressed, and the controllability of the above interface is improved.

[0015]

EXAMPLES The present invention will be described below with reference to specific examples, but it goes without saying that the present invention is not limited to these examples.

Example 1 This example is an example in which Mn-Zn ferrite material containing iron oxide, zinc oxide, and manganese oxide as main components was joined and integrated by a solid-state reaction by a discharge plasma sintering method. First, a polycrystalline Mn-Zn ferrite material was synthesized. That is, Fe raw materials (eg αFe ₂ O ₃ ), Zn raw materials (eg ZnO) and Mn raw materials (eg MnO) are used as raw materials, and these raw materials are Fe ₂ O ₃ : ZnO: MnO = 52: 20: 2.
8 (molar ratio), each was weighed, mixed and crushed in a stainless steel ball mill, and subsequently molded, followed by firing at a temperature of 1300 ° C. for 2 hours in a 1% oxygen gas atmosphere. As a result, a polycrystalline Mn-Zn ferrite material was obtained.

Next, a single crystal Mn-Zn ferrite material was synthesized. That is, a polycrystalline Mn-Zn based ferrite material was produced in the same manner as the above-described method for synthesizing the polycrystalline Mn-Zn based ferrite material, and the obtained polycrystalline Mn-Zn based ferrite material was subjected to a Bridgman method in a platinum crucible. After being melted at a temperature of 1700 ° C., it was single-crystallized by solidifying from the bottom to obtain a single-crystal Mn—Zn-based ferrite material.

Subsequently, the polycrystalline Mn-Zn based ferrite material and the single crystal Mn-Zn based ferrite material have a diameter of 20.
mm and a thickness of 2 mm, the polycrystalline Mn-Zn based ferrite material and the single crystal Mn-Z are processed.
The joint surface of the n-type ferrite material was finished to be a mirror surface.

Then, the mirror-finished joint surfaces were brought into close contact with each other, and plasma activation treatment was performed for 1 minute.
After that, the pressure is 500 kg / c by the spark plasma sintering method.
A bonded ferrite material was obtained by holding for 3 minutes under the conditions of m ² , current density of 570 A / cm ² , and firing temperature of 900 ° C. for solid phase reaction.

When the bonded ferrite material was produced in this manner, it was found that the above-mentioned polycrystalline Mn-Zn ferrite material and the single crystal Mn-Zn ferrite material were bonded and integrated with sufficient strength. Further, when the interface between the polycrystalline Mn—Zn based ferrite material and the single crystal Mn—Zn based ferrite material of this bonded ferrite material was observed, as shown in FIG. 1, the single crystal ferrite material and the polycrystalline ferrite material were It was found that the separation of the interface was very good and the waviness of the interface was extremely small.

On the other hand, the polycrystalline Mn-Zn ferrite material and the single crystal Mn-Zn ferrite material obtained as described above are replaced by the conventional hot pressing method instead of the above-mentioned spark plasma sintering method. When heat-pressed by, the polycrystalline Mn-Zn ferrite material and the single-crystal Mn-Z
The n-type ferrite material did not join together and was peeled off.

Next, in order to examine the firing conditions after the plasma activation treatment by the above-mentioned discharge plasma sintering method, the firing temperature and the holding time were changed as shown in Table 1 below.
Others were joined and integrated by the same method as described above, and the joining state of the obtained joined ferrite material was examined. The results are shown in Table 1. The current density is 450 to 640 A /
It was adjusted to be cm ² .

[0023]

[Table 1]

As shown in Table 1, when the present invention is applied, polycrystalline Mn-Z is produced in a short time even at a relatively low temperature of 900 ° C.
It has been found that the n-type ferrite material and the single crystal Mn-Zn-based ferrite material can be joined and integrated. When the firing temperature was 700 ° C., good joining and integration could not be achieved, but when the firing temperature was 800 ° C., the joining and integration could be sufficiently performed.

From the above experimental results, when the polycrystalline Mn-Zn based ferrite material and the single crystal Mn-Zn based ferrite material are fired by the discharge plasma firing method, they are well joined and integrated at a low temperature of about 900 ° C. It became clear.

Example 2 First, Mn-Zn ferrite powder was wet-synthesized by coprecipitation reaction in an aqueous solution. Examples of this method include, as raw materials, MnSO ₄ .5H ₂ O and ZnSO _4.
7H ₂ O, FeSO ₄ · 7H ₂ O, MnO: Zn
A solution containing O: Fe ₂ O ₃ = 28: 20: 52 was prepared. To this aqueous solution, potassium hydroxide KOH was added as an alkali to adjust the pH to 9.

Furthermore, while sufficiently stirring this solution, potassium chlorate KClO ₃ was added as an oxidizing agent, and then the temperature of the reaction solution was maintained at 100 ° C. for 1 hour to allow the reaction to proceed. After the reaction was completed, the obtained product was thoroughly washed with water, filtered, and dried to obtain a coprecipitated ferrite powder of Mn-Zn ferrite.

Then, the Mn-Z thus obtained was obtained.
The n-ferrite coprecipitated ferrite powder was thoroughly mixed and dispersed in water to prepare a paste. This paste was applied to the joint surfaces of the polycrystalline Mn—Zn based ferrite material and the single crystal Mn—Zn based ferrite material prepared in Example 1 above, and dried.

Polycrystalline Mn-Zn prepared in this way
System ferrite material and single crystal Mn-Zn system ferrite material are adhered to each other at their joint surfaces, and plasma activation treatment is performed for 1 minute by a discharge plasma sintering method at a pressure of 500 kgf / cm ² ,
Under the condition that the current density was 400 to 650 A / cm ² , the bonding temperature was changed from 500 ° C. to 700 ° C. to carry out the solid phase reaction. Table 2 shows the bonding state depending on the bonding temperature.

[0030]

[Table 2]

As a result, it was found that the joining can be performed with sufficient strength at a joining temperature of 600 ° C. or higher. Thus, by interposing the coprecipitated ferrite powder, 60
It was confirmed that the joining and integration can be performed at a low temperature of 0 to 700 ° C.

[0032]

As described above, in the present invention, since the single crystal ferrite material and the polycrystalline ferrite material are joined and integrated by the discharge plasma sintering method, the temperature is 900 ° C. or less, which is far higher than the conventional method. It becomes possible to perform the treatment at a low temperature. In particular, when the coprecipitated ferrite powder is interposed at the joint interface, the joint can be integrated at a low temperature of 600 to 700 ° C. Therefore, along with this, productivity is improved and at the same time cost is reduced.

Further, in the sintering process by the above-mentioned discharge plasma sintering method, since the time required for the completion of sintering is only a few minutes, which is an extremely short time, the interface between the single crystal ferrite material and the polycrystalline ferrite material is very small. Is very good, and the undulation of the interface is extremely small, and the controllability of the interface is excellent.

[Brief description of drawings]

FIG. 1 is a schematic perspective view for explaining a discharge plasma sintering method.

FIG. 2 is a schematic diagram for explaining a mechanism of a sintering reaction by a discharge plasma sintering method.

FIG. 3 is a micrograph showing a crystal structure of an interface of a bonded ferrite material produced by applying the present invention.

Claims (2)

[Claims] 1. A method for manufacturing a bonded ferrite material, which comprises bonding a single crystal ferrite material and a polycrystalline ferrite material, wherein the bonding is performed by a spark plasma sintering method. 2. The method for producing a bonded ferrite material according to claim 1, wherein a coprecipitated ferrite powder is interposed at a bonding interface between the single crystal ferrite material and the polycrystalline ferrite material during bonding.