JPH04240193A - Production of combined ferrite - Google Patents

Abstract

PURPOSE:To obtain combined ferrite in a high yield by joining single-crystalline ferrite to polycrystalline ferrite by a solid phase reaction. CONSTITUTION:Starting material for polycrystalline ferrite mixed with 0.003-0.3wt.% at least one kind of additive selected among salts contg. K, Sr, Pb and Ba and oxides of them is molded and this molded body is treated in vacuum and calcined in He contg. oxygen to produce polycrystalline ferrite. This ferrite is brought into contact with single-crystalline ferrite and the resulting temporarily joined body is joined by heating in an N2 atmosphere contg. oxygen to obtain combined ferrite.

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 composite ferrite consisting of a single crystal ferrite and a polycrystalline ferrite, which is used, for example, in a junction type magnetic head.

0002

2. Description of the Related Art In recent years, composite ferrites have been attracting attention as magnetic heads, such as video heads. Compared to conventional single-crystal ferrite, this composite ferrite has lower sliding noise and better S/N and C/N ratios, making it particularly suitable for use in high-band magnetic heads. .

[0003] This composite type ferrite has a shape in which a single crystal ferrite and a polycrystalline ferrite are bonded together, and as an example of its manufacturing method, the applicant has disclosed Japanese Patent Publication No. 10438/1986.
No. 61-3313 discloses a technique in which a single crystal ferrite and a polycrystalline ferrite are brought into contact with each other, heat treated, and bonded by a solid phase reaction.

0004

[Problems to be Solved by the Invention] However, in the above-mentioned bonding method using the solid phase reaction, the temperature range for heating the temporary bonded body to cause the solid phase reaction is, for example, 129°C.
Single crystal ferrite and polycrystalline ferrite bond only in a very limited range from 0℃ to 1310℃, and at 1290℃
If it is less than 1,310° C., bonding failures occur frequently, and if it exceeds 1,310° C., single crystallization progresses, making it difficult to control the firing temperature range and making it unsuitable for mass production.

[0005] In addition, the applicant previously disclosed the Japanese Patent Publication No. 62-
No. 49647 requires cutting to a predetermined thickness after single crystallization, and there is a problem that it is not suitable for mass production when finishing desired single crystals and polycrystals into specified shapes.

[0006] The purpose of the present invention is to solve the above-mentioned problems,
The object of the present invention is to provide a composite ferrite that enables solid-phase reaction over a wide range, improves the bonding yield between single-crystal ferrite and polycrystalline ferrite, and has good quality, as well as a method for producing the same.

[0007]

[Means for Solving the Problems] The composite ferrite of the present invention contains salts containing K, Sr, Pb, and Ba and at least one of their oxides from 0.003% by weight to 0.3% by weight.
% by weight of polycrystalline ferrite and single crystal ferrite.

[0008] The method for manufacturing composite ferrite of the present invention includes:
The main component is iron oxide that has a spinel structure or a history of spinel structure, and contains K, Sr, Pb, and Ba.
At least one of salts and their oxides containing 0
．． A molded body is produced from a ferrite raw material containing from 0.03% by weight to 0.3% by weight as an additive, and the obtained ferrite molded body is vacuum treated and then fired in a helium atmosphere containing oxygen to produce polycrystalline ferrite, The obtained polycrystalline ferrite is brought into contact with single crystal ferrite to obtain a temporary bonded body,
This temporary bonded body is characterized by being heat-treated and bonded in a nitrogen atmosphere containing oxygen.

[0009]

[Operation] In the above-mentioned structure, at least one of salts containing K, Sr, Pb, and Ba and their oxides is added from 0.003% by weight to 0.3% by weight in the raw material of polycrystalline ferrite.
By including it as a weight percent additive, it induces interdiffusion between single crystal ferrite and polycrystalline ferrite at low temperatures, and at high temperatures the crystal grain size obtained by firing is 7.6 μm, which increases to 9 by 1360°C treatment. .1 μm, the grain growth effect maintains the polycrystalline state even at high temperatures. Therefore, the actual junction temperature range is 1200
℃ to 1360℃, and the bonding yield between single-crystal ferrite and polycrystalline ferrite can be greatly improved compared to conventional additive-free products.

[0010] Here, the reason why at least one of the salts containing K, Sr, Pb, and Ba and their oxides is limited to 0.003% by weight to 0.3% by weight is that less than 0.003% by weight cannot be added. This is because it is not effective, and if it exceeds 0.3% by weight, the crystal grains of polycrystalline ferrite will become 40 μm or more, and pores will increase, which is not preferable. The bonding atmosphere was an atmosphere in which the oxygen partial pressure was almost in equilibrium with the oxygen partial pressure of the ferrite so that the ferrite properties were not deteriorated, and the growth was performed in the same crystal axis direction.

[0011] In the present invention, good quality means
In the case of a magnetic head for a VTR, when the single crystal ferrite portion is 100 μm with respect to the media running chip width of 2 mm, the waviness at the interface between the single crystal ferrite and the polycrystal ferrite is 10 μm.
This refers to the case where the distance is from μm to 30 μm, and in this case, extremely low sliding noise is exhibited. Therefore, from a sliding perspective, it exhibits excellent bonding strength and has excellent electromagnetic conversion characteristics.

[0012] Furthermore, as is conventionally known, the iron oxide raw material used to produce the ferrite molded body must have a spinel structure or have a history thereof, since it is essential for the production of single crystal ferrite. The raw materials are also specified in the present invention.

[0013]

[Example] An actual example will be explained below. Example 1
Wet-synthesized magnetite is roasted as a raw material for iron oxide,
This was mixed with MnO 31 mol%, ZnO 16 mol%, F
E2O3 was mixed to a composition of 53 mol%, potassium nitrate was added as an additive in the amount listed in Table 1 in terms of oxide, and the mixture was mixed, calcined at 1050°C, and pulverized.
Molded at a pressure of 5000 psi. Thereafter, this compact was subjected to vacuum treatment at 1200° C. for 2 hours, and then fired in He containing 10% oxygen at 1320° C. for 8 hours.

The polycrystalline ferrite thus obtained was processed into a plate having a length of 27 mm, a width of 5 mm, and a thickness of 10 mm, and the portion in contact with the single crystal was mirror-polished. The length of this is 27 by mirror polishing the touching part in the same way.
It was temporarily bonded to a single crystal ferrite having a width of 5 mm, a width of 5 mm, and a thickness of 1 mm by coating with nitric acid so that the polished surfaces faced each other.

The temperature of the obtained temporary bonded body was raised to 1150°C at a heating rate of 300°C/h in a nitrogen atmosphere, and 5% oxygen was added.
The temperature was changed to nitrogen gas containing 1,350°C for 2 hours, and then cooled in a nitrogen gas atmosphere.

The distance over which the single crystallization of the obtained bonded body had progressed was measured, and in Table 1, those with a distance of 10 μm to 30 μm were marked as good bonding, and those with a distance of 40 μm or more were marked with ▲.
Separated particles are considered to be defective and marked with ▼, one particle size is 4.
Those with grain growth of 0 μm or more are marked with an x mark.

[0017]

[Table 1]

From the results in Table 1, potassium nitrate was added to 0.00
The compound added in the range of 3% by weight to 0.3% by weight makes the actual bonding temperature 100°C lower than the conventional 1300°C, that is, a good composite ferrite in a wide temperature range from 1200°C to 1360°C. It can be seen that the following can be obtained.

Example 2 Composite ferrite was produced using the same process as in Example 1, using potassium oxide, strontium nitrate, lead oxide, and barium oxide as additives instead of potassium nitrate. As in Example 1, the amount added was 0.
．． In the range of 0.003% to 0.3% by weight, it was possible to bond composite ferrite with good bonding in which the distance of single crystallization progressed from 10 μm to 30 μm over a wide temperature range.

[0020] Figure 1 also shows that when 0.01% of potassium nitrate was added in terms of oxide, the distance over which single crystallization progressed was 10.
Figure 2 shows a micrograph of the cross-section of the bonding interface of a composite ferrite with good bonding from μm to 30μm. A micrograph of each cross section is shown.

[0021]

As is clear from the above explanation, according to the present invention, when obtaining a composite ferrite using a solid phase reaction, K, Sr, Pb,
Since a predetermined amount of an additive consisting of Ba is added, the temperature range in which single crystal ferrite and polycrystalline ferrite can be bonded can be widened, and the bonding yield can be greatly improved compared to conventional products. Composite ferrite can be mass-produced.

[0022] Furthermore, since the bonding is performed using a solid phase reaction, there is no need for special means such as pressurization, and there is no need to insert an inclusion between the single crystal ferrite and the polycrystal ferrite. Therefore, it is possible to increase productivity and reduce costs.

[Brief explanation of the drawing]

FIG. 1 is a micrograph showing the metal structure of a cross section of a bonded interface of composite ferrite with good bonding.

FIG. 2 is a micrograph showing a polycrystalline ferrite structure in which grain growth of 40 μm or more has occurred.

Claims (1)

[Claims] Claim 1: The main component is iron oxide having a spinel structure or a history of spinel structure, K,
A molded body is manufactured from a ferrite raw material containing salts containing Sr, Pb, and Ba and at least one of their oxides as an additive of 0.003% to 0.3% by weight, and the obtained ferrite molded body is vacuum treated. After that, it is fired in a helium atmosphere containing oxygen to produce polycrystalline ferrite, the obtained polycrystalline ferrite is brought into contact with single crystal ferrite to obtain a temporary bonded body, and this temporary bonded body is heated in a nitrogen atmosphere containing oxygen. A method for producing composite ferrite characterized by heat treatment and bonding.