JPS6049150B2 - Manufacturing method of low magnetic loss Mn-Zn ferrite - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention has low magnetic loss characteristics and high density Mn.
-Regarding a method for manufacturing Zn ferrite.

Conventional low magnetic loss Mn-Zn ferrite has a density of about 99% of the theoretical density after sintering in the final process, and there are many pores in the sintered body. However, when the recording medium slides, the crystals fall off starting from the pores, resulting in poor wear resistance as a magnetic head and damage to the recording medium. Furthermore, when the magnetic powder of the recording medium accumulates in the pores and drop-off pores of the crystal, there is a problem in that the signal recorded on the recording medium is disturbed due to the magnetic field generated by the magnetic powder. In order to solve these problems, various methods have been proposed for reducing the porosity of Mn-Zn ferrite to increase its density.

The applicant of this application previously published Mn
- Perform primary sintering of the Zn ferrite molded body in an oxidizing atmosphere of nitrogen gas containing 2 to 10% oxygen, and then fill the sintered body with ferrite powder of the same composition in a single-layer container, It was proposed that Mn-Zn ferrite with a density of 99.95% or more can be obtained by hot isostatic pressing. However, the relative magnetic loss coefficient (tanδ/
μ) is 10× under the measurement conditions of 100 KH2 and 4 m0e,
10-6 or more and has low magnetic loss characteristics
No n-ferrite was obtained. In order to solve the above problem, the present inventor conducted various studies and found that by improving the sintering conditions, cooling conditions, and hot isostatic pressing conditions of the primary sintering process, the relative magnetic loss coefficient was reduced to 5 × 10. -0 or less, density is 1
00% low magnetic loss characteristic and high density Mn-Z
It was discovered that n-ferrite can be obtained.

That is, in this invention, Fe20350 to 56 mol%,
The main components are 23 to 40 mol% of MnO, 5 to 27 mol% of ZnO, and CaOO. Ol~0. Weight % and SiO2O. O
3% by weight or less, ZrO2O. 35% by weight or less, TiO2
O. 35% by weight or less, ■20.0. A molded Mn-Zn ferrite containing at least one of the following: After primary sintering in an atmosphere, cooling treatment is performed at an oxygen concentration 2 to 5 times higher than the equilibrium oxygen concentration, and the density of the primary sintered body in that case is 9.
5% or more, then the sintered body is filled in a container with a double or more structure together with ferrite powder having the same composition as the ferrite, and an inert gas such as argon gas is used as the pressure medium.
Temperature 1000°C ~ 1250°C, pressure 500k9/d ~
Hot isostatic pressing was performed under suitable conditions of 2000 k9/Cri, and the density was 99.95% or more, and the relative magnetic loss coefficient was 5 × 10- under the measurement conditions of 100 KHz and 4 m0e.
The present invention is characterized by obtaining a low magnetic loss Mn-Zn ferrite having a characteristic of 6 or less.

The reasons for limiting the components in this invention will be explained below. Main component composition Fe2O35O~56 mol%, MnO2
3 to 40 mol% and ZnO 5 to 27 mol% are regions that have soft magnetic properties with a Curie temperature of 70° C. or higher and a magnetic permeability of 1000 or higher; other regions are soft magnetic materials,
It's not practical.

CaO is an additive component that obtains low magnetic loss characteristics, and FIG. 1 shows the relationship between the magnetic loss characteristics when CaO is added alone and when CaO is added in combination with SiO2. As is clear from FIG. If less than 0.01% by weight is added, low magnetic loss characteristics cannot be obtained.

Furthermore, Fig. 2 shows a graph showing the relationship between the CaO content and the density of Mn-Zn ferrite after primary sintering, and as is clear from this, addition of more than 0.3% by weight Since the density after primary sintering is less than 95% and it is not possible to increase the density by hot isostatic pressing in the next step, Ca
O is 0.01-0. The weight is expressed as %. By adding SjO2 in combination with CaO, even better low magnetic loss characteristics can be obtained than when CaO is contained alone, but as shown in Figure 1,
If the amount of 41 exceeds 0.03% by weight, the effect cannot be obtained. Like SlO2, ZrO2, TlO2, and v2O5 obtain low magnetic loss characteristics by combined addition with CaO. Ol%SjO
This is a graph showing the relationship between the magnetic properties when the amounts added to ZrO2, TiO2, and V2 are changed under the conditions of 2. As is clear from this, ZrO2, TiO2,
2O5 is 0.35% by weight, 0.35% by weight, and 0, respectively.
．． If the amount of 5 is added in excess of the amount by weight, the above effect disappears.

In this invention, cooling after primary sintering must be performed under oxygen concentration conditions that are 2 to 5 times higher than the equilibrium oxygen concentration.

If this oxygen concentration is less than twice the equilibrium oxygen concentration, the relative magnetic loss coefficient of ferrite O after hot isostatic pressing will deteriorate, and if it exceeds five times the equilibrium oxygen concentration, the relative magnetic loss coefficient after primary sintering will deteriorate. Since the relative magnetic loss coefficient deteriorates and does not recover even after hot isostatic pressure pressing, the oxygen concentration is set to be 2 to 5 times higher. In addition, the reason why the density of the sintered body after primary sintering was set to 95% or more7 is that if the density is less than 95%, the pores become through holes that communicate with the surface of the ferrite and the inside, and during hot isostatic pressing. This is because the pressure medium invades the pores in the ferrite sintered body, making it impossible to obtain a high-density product. Therefore, Mn-Zn
It is necessary to appropriately select the molding density, primary sintering temperature, and primary sintering holding time of the ferrite molded body. Next, a container for hot isostatic pressing will be explained.

As shown in FIG. 4A, a conventional container consists of an alumina container 1 and an alumina lid 2, and is filled with ferrite powder 4 of the same composition as a ferrite sintered body 3. However, due to the internal structure of the container 1, The resulting ferrites have different magnetic loss characteristics. In contrast to the conventional single layer structure shown in FIG. 4A, the present invention has a multi-layer container 1, such as a double structure container 1 shown in FIG. 4B, or a triple structure container 1 shown in FIG. 4C. 1 is filled with ferrite sintered body 3 together with ferrite powder 4. When hot isostatic pressing is performed using a container with this double or more structure, oxygen is prevented from leaving the ferrite, thereby preventing deterioration of the magnetic loss characteristics of the obtained ferrite. The present invention will be explained below based on examples.

History Example 1 Fe203, MnC03, and Zn0 were weighed to have the composition of sample A in Table 1, thoroughly stirred and mixed in a ball mill, then calcined in air at 900°C, and pulverized in a Sarako ball mill. A raw material powder k having an average particle size of 1.0 μm was obtained. The additive components are as shown in Table 1, including CaO source and C
acO3 and ZrO2 were added during milling. Next, 1% by weight of PVA was added as a binder to the raw material powder, and after granulation, it was made into a molded body of 4" x 12 balls x 7 gourds, and primary sintering was performed. The conditions for the primary sintering were: 1250'C for 3 hours;
% of oxygen, and cooling was performed in an oxidizing atmosphere with an oxygen concentration four times higher than the equilibrium oxygen concentration. 2 at a cooling rate of 150° C./Hr. Further, as a comparative example, the steps up to the primary sintering were carried out under exactly the same conditions as above, and only the cooling was carried out in an atmosphere having an equilibrium oxygen concentration as shown by the straight line 1 in FIG. The two types of primary sintered bodies obtained were filled into a double-structured alumina container as shown in Figure 4(b) together with Mn-Zn ferrite powder of the same composition, and after the lid was closed, argon gas was applied under pressure. Using the medium as a medium, hot isostatic pressing was carried out for 3 hours at a temperature of 1150°C and a pressure of 1150 kg/d.

Table 2 shows the properties of the obtained Mn-Zn ferrite sample. As is clear from Table 2, Mn-Z according to the present invention
N-ferrite has extremely excellent low magnetic loss characteristics, and a large difference was observed compared to the magnetic loss characteristics of a comparative example in which the cooling conditions during primary sintering were outside the conditions of the invention method.

Example 2 Fe203, MnC03, and Zn0 were weighed to have the composition of sample B in Table 1, stirred and mixed thoroughly in a ball mill, pre-calcined in air at 900°C, and further ground in a ball mill to obtain an average particle size. A raw material powder of 0.95 μm was obtained.

As shown in Table 1, the additive components include CaCO3, SjO2,
TiO2 was added during milling.

Next, 1% by weight of PVA was added to the raw material powder as a binder.
After granulation, a molded body of 40 wr L x 12 yen x 7 yen was formed and primary sintering was performed. The conditions for primary sintering are 11
Heating was performed at 80° C. for 3 hours in nitrogen gas containing 0.5% oxygen, and cooling was performed at a cooling rate of 150° C./Hr in an oxidizing atmosphere with an oxygen concentration three times higher than the equilibrium oxygen concentration.

The obtained primary sintered body was filled into single, double, and triple structured alumina containers shown in FIGS. 4A, b, and c together with Mn-Zn ferrite powder having the same composition as the sample. After closing the lid, use Alcon gas as the pressure medium and increase the temperature to 1100℃.
A hot isostatic press treatment was carried out for 3 hours at a pressure of 900 kg/cm.

Table 3 shows the properties of the obtained Mn-Zn ferrite.
As is clear from the results in Table 3, if a container with a double or more multilayer structure is used for hot isostatic pressing,
There is a significant difference between the magnetic loss characteristics obtained in the case of Comparative Example 5 using a single-layered container, and the M
It can be seen that n-Zn ferrite has excellent low magnetic loss characteristics.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the relationship between CaO single content and CaO-SlO2 composite content and magnetic loss characteristics. FIG. 2 is a graph showing the relationship between CaO content and density after primary sintering. Figure 3 shows 0.1%CaO, 0.01%S
ZrO2, TiO2, v2c) when containing lO2. It is a graph showing the relationship between content and magnetic loss characteristics. FIG. 4 is an explanatory diagram of a container used for hot isostatic pressure pressing, and a
The figure shows a single-layer structure container, figure b shows a double-layer structure container, and figure c shows a triple-layer structure container. Figure 5 is a graph showing the relationship between oxygen concentration and temperature during cooling during primary sintering, where straight line 1 represents oxidation at an oxygen concentration four times higher than the equilibrium oxygen concentration. The figure shows the case of cooling in a static atmosphere. In the figure, 1... alumina container, 2... alumina lid, 3...
- Ferrite sintered body, 4... ferrite powder.

Claims (1)

[Claims] 1 Fe2O_350-56 mol%, MnO23-40
mol%, ZnO5 to 27 mol% as the main component, CaO0
．． 01 to 0.3% by weight and SiO_20.03% by weight or less, ZrO_20.35% by weight or less, TiO_20.35
1 Mn-Zn ferrite molded body containing at least one of V_2O_50.3% by weight or less
The sintered body is then sintered and then cooled at an oxygen concentration 2 to 5 times higher than the equilibrium oxygen concentration. The sintered body is then filled with ferrite powder of the same composition into a container with a double or more layered structure, and then hot-sintered. Low magnetic loss Mn- characterized by hydraulic pressing
A method for producing Zn ferrite.