JPS583994B2 - Huerito no Seizouhouhou - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing ferrite, in which ferrite powder obtained by a wet method is fired by a hot press method.

Recently, the field of magnetic recording has made remarkable progress, and with the increase in recording density, magnetic materials for magnetic heads, which are resistant to wear and have excellent high frequency characteristics, use wavelengths of about 1μ.
A ferrite with few pores is required.

The conventional manufacturing method for ferrite is called the dry method.
Be205 and Mn, Zn, Ni, Cu, and divalent,
Oxides containing trivalent metal ions are weighed and blended in an appropriate molar ratio, stirred and mixed in a mixer for a certain period of time, and then dried, granulated, and molded.

In such a method for producing an oxide, a densification phenomenon progresses as well as caking, and the porosity is affected by the production conditions, but normally a porous body with pores is obtained.

As described above, it has been difficult to reduce the porosity using ordinary sintering methods, but it is possible to produce ferrite with fewer pores using the high temperature and high pressure method (hereinafter referred to as the hot press method).

Although it is possible to reduce the number of pores using the hot press method using the conventional dry method, the state in which pores called micropores are retained between crystal grains, that is, at grain boundaries. becomes.

When a magnetic head is made of such ferrite, the presence of pores causes the ferrite surface to become rough during tape running, causing crystal grains to peel off.

Furthermore, when a ferrite raw material produced by a wet method (hereinafter referred to as coprecipitated ferrite powder) is hot pressed, sintering cracks occur and the desired product cannot be obtained.

The present invention eliminates these drawbacks and provides a method for producing ferrite that has almost no pores and does not cause sintering cracks.

First, a comparative example will be explained. Comparative example Fe20352 molar ratio, Mn030 molar ratio and Zn0
A coprecipitated ferrite powder having a composition ratio of 18 moles was molded into a disk shape by a commonly used method.

As shown in FIG. 1, this molded body 5 is
It was placed in a press mold consisting of a lower punch 2 and an outer mold 3 and embedded in alumina powder 4.

Next, this mold was held at a temperature of 1,300°C for 1 hour and heated to 300°C.
Hot pressing was performed by applying a pressure of kg/cm2.

Sintering cracks were observed in the obtained sintered body.

Sintering cracks occurred in all of the samples obtained, and no good quality sintered bodies were obtained.

On the other hand, as a result of thermal analysis of this coprecipitated ferrite powder, 200 ~
A third example will be described in which it was revealed that exothermic reactions occurred at temperatures of 300° C. and 600 to 700° C., and the latter reaction was particularly remarkable, and the reaction occurred in the presence of oxygen.

Example 1 Co-precipitated ferrite powder having the same composition as the above Comparative Example was first heat treated in air at a temperature of 800° C. for 1 hour, and then hot pressed under the same conditions as the above Comparative Example.

No sintering cracks were observed in all of the obtained sintered bodies, and they were completely fired products.

The porosity was 0.1% or less.

On the other hand, as a result of thermal analysis of the coprecipitated ferrite powder heat-treated at a temperature of 800°C, no exothermic reaction was observed at all as observed in the comparative example.

Example 2 Co-precipitated ferrite powder with the same composition as the comparative example was mixed with 100 to 100
Heat treatment was performed at each temperature for 40 minutes at 100°C intervals up to 0°C, and hot pressing was performed under the same conditions as the comparative example.

Figure 2 shows the degree of sintering cracking in the sintered body. In addition, the results of X-ray analysis of the powder heat-treated at each temperature are also shown in FIG.

Precipitation of Fe203 was observed at a temperature of 400° C. or higher, and the number of cracks in the sintered body decreased rapidly.

The amount of Fe203 precipitated increases as the heat treatment time increases.

As a typical example, a case of heat treatment at 500° C. is shown in FIG.

Example 3 Fe203 52 mol%, Mn024 mol%, and Z
A coprecipitated ferrite powder having a composition of n024 mol was hot pressed under the same conditions as the comparative example.

In addition, hot pressing was similarly performed on coprecipitated ferrite powders that had been heat treated at temperatures of 600°C, 700°C, and soo°C.

No sintering cracks were observed in the sintered body thus obtained, and it was a perfect sintered body.

Moreover, the results of measuring the initial magnetic permeability are shown in FIG.

It has now become clear that hot-pressed sintered bodies made from heat-treated raw materials exhibit significantly superior properties compared to raw materials that are not heat-treated.

As described above in detail according to the examples, in the method of the present invention, ferrite powder is treated in advance at a temperature higher than the temperature at which Fe203 precipitation begins, so sintering cracks are effectively prevented and magnetic properties are improved. In addition, high-density ferrite can be manufactured easily and efficiently, and its usefulness as a material for magnetic heads is excellent.

[Brief explanation of drawings]

Figure 1 is a conceptual diagram of the main parts of the hot press equipment, and Figure 2 is for explaining the method according to the present invention, and shows the relationship between the heat treatment temperature of the coprecipitated ferrite raw material, the degree of Fe203 precipitation, and the degree of sintering cracking. Figure 3 is a diagram showing the relationship between the heat treatment time of the coprecipitated ferrite raw material and the precipitation amount of Fe203, and Figure 4 is a diagram showing the relationship between the heat treatment temperature and the initial permeability of the coprecipitated ferrite raw material. .

Claims (1)

[Claims] 1. A method for producing ferrite, which comprises heat-treating coprecipitated ferrite powder at a temperature equal to or higher than the temperature at which precipitation of Fe203 begins, followed by hot pressing and firing.