JPS6156185B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to polycrystalline ferrites, particularly ferrites suitable for magnetic heads.

Conventional configurations and their problems Magnetic head materials are required not only to have magnetic properties such as high magnetic flux density and high magnetic permeability, but also to have mechanical properties that can withstand fine precision machining during head processing. Furthermore, in order to meet the demand for higher recording densities, magnetic properties such as high permeability and low loss in high frequency bands, miniaturization of crystals due to reduction in track width, and improvement in mechanical strength are required.

However, the polycrystalline materials used so far,
The crystal grain size was around 20 μm, and it was not suitable for ultra-precision micromachining.

OBJECT OF THE INVENTION An object of the present invention is to provide polycrystalline ferrite, which has a smaller crystal grain size than conventional polycrystalline ferrites and has good ultra-precision micro-processability, at a low cost and can be mass-produced. Furthermore, it is an object of the present invention to provide polycrystalline ferrite with increased toughness and further improved ultra-precision micro-processability.

Structure of the Invention The present invention is a ferrite mainly composed of Mn-Zn or Ni-Zn, which contains 0.01 to 0.5% by weight of Na component, thereby making the crystal grains constituting the ferrite finer. be.

Furthermore, the present invention improves the toughness of the ferrite by adding 0.01 to 0.5% by weight of Na and 0.005 to 0.5% by weight of Zr to the ferrite whose main component is Mn-Zn or Ni-Zn. It is elevated. Furthermore, by including 0.01 to 0.5% by weight of Ca component, the toughness is further improved.

Description of Examples Hereinafter, details of the present invention will be explained based on Examples.

Example 1 Final composition ratio: 54.5 mol% Fe ₂ O ₃ , 29.0 mol%
MnO, purity 99.98 to be 16.5 mol% ZnO
% or more of high-purity iron oxide, high-purity manganese carbonate,
and high-purity zinc oxide, high-purity sodium carbonate (Na ₂ CO ₃ ) was added in various proportions, and wet-mixed in a stainless steel pot for 16 hours. Then, the precipitate was heated at 240℃ for 10
Dry for an hour. Pure water was added to the dry powder in an amount of 15% by weight of the total amount, and the powder was granulated using a sieve machine to make the particle size uniform, and then the granulated powder was molded at a molding pressure of 300 Kg/cm ² . This molded body was placed in the air at 1300℃ for 3 hours.
A sintered body was obtained by hot pressing while applying a pressure of 300 Kg/cm ² . A block with a width of 3 mm, a length of 6 mm, and a thickness of 3 mm was cut from the obtained sintered body, and the surface was polished for 20 minutes using the usual method, and then finished to a mirror surface with a paste containing diamond particles with a particle size of 3 μm. The block was placed in phosphoric acid kept at a temperature of 80°C for 30 minutes.
The sample was immersed for a second, the mirror surface portion was etched, and the crystal grain size was observed using an optical microscope.

FIG. 1 shows the relationship between the average grain size of the crystal grains of the obtained ferrite and the amount of Na added thereto. As you can see from this figure, Na is 0.01% by weight
When more than 20% of ferrite is added, the average crystal grain size of ferrite becomes smaller than 20 μm, which is 0.5% by weight.
reaches 5 μm. When the amount of Na is 0.5% by weight or more, the average crystal grain size becomes approximately constant at 4 to 5 μm. However, if the Na content exceeds 0.5% by weight, the saturation magnetic flux density of ferrite decreases and the coercive force increases, making it undesirable as a magnetic head material.

Therefore, in order to maintain the magnetic properties of ferrite within a practical range and to refine its crystal grain size, it is desirable that the amount of Na be 0.01 to 0.5% by weight. By selecting the amount of Na within this range, the average crystal grain size of ferrite can be adjusted to 5 to 20μ.
It can be controlled within the range of m.

By the way, when a Vickers indentation (load: 200 g, load application time: 30 seconds) 1 is applied to a ferrite sample finished into a mirror finish as described above, as shown in FIG. 2, a crack 2 occurs. This crack 2
The length C was measured, and the relative value of the critical stress intensity coefficient K _IC (proportional to the −2/3 power of C) was determined. According to the results, it was revealed that as the average crystal grain size of ferrite became smaller, the relative value of K _IC increased by 5 to 10%, and the mechanical properties of ferrite were improved.

Example 2 Final composition ratio: 54.5 mol% Fe ₂ O ₃ , 29.0 mol%
MnO, coprecipitated ferrite synthesized by wet method to have 16.5 mol% ZnO (0.0049% SiO ₂ as impurity)
% by weight, including 0.004% by weight of Ca and 0.008% by weight of Na), added Na ₂ CO ₃ to 0.023% by weight based on the total amount, and then calcined at 800°C for 2 hours.
This was wet-milled in a stainless steel pot for 16 hours, and the precipitate was dried at 240°C for 10 hours. After that, add pure water to a ratio of 15% by weight, granulate it with a sieve machine, make the particle size uniform, and make 300Kg/
Molded by applying pressure of cm ² and molded at 1300℃ in air.
A sintered body containing 0.01% by weight of Na was obtained by hot pressing under a pressure of 300 kg/cm ² for an hour. The obtained sintered body was mirror-finished in the same manner as in Example 1, and the average crystal grain size was measured.
It was 15 μm.

Furthermore, 1.16% of Na ₂ CO ₃ was added to the above coprecipitated ferrite.
Add 0.5% by weight of Na using the same procedure as above.
When ferrite containing the additive was produced, its average crystal grain size was 5 μm.

In addition, when ferrite was produced by the same procedure without adding Na ₂ CO ₃ to the coprecipitated ferrite, its average crystal grain size was 20 μm.

Added Na content in ferrite is 0.5% by weight
Beyond this, a 15% decrease in saturation magnetic flux density was observed, and a 20% increase in coercive force.

In this way, Na is also added to coprecipitated ferrite.
By adding 0.01 to 0.5% by weight, the average crystal grain size can be reduced to 20 μm or less without deteriorating the magnetic properties.

Example 3 Final composition ratio: 51.0 mol% Fe ₂ O ₃ , 18.8 mol%
High-purity iron oxide, nickel oxide, and zinc oxide are blended to give NiO, 30.2 mol% ZnO, and 0.023% and 1.16% by weight of Na ₂ CO ₃ are added.
These two materials were wet mixed in a stainless steel pot for 16 hours. Then, the precipitate was heated to 240℃.
Let dry for 10 hours. Pure water was added to each at a ratio of 15% by weight, granulated with a sieve machine, and the particle size was made uniform. After that, molding was performed at a molding pressure of 300 kg/cm ² , and Na was added using the same procedure as in Example 1. Ferrite samples containing 0.01% by weight and 0.5% by weight were prepared. These samples were immersed in phosphoric acid at 130°C for 5 minutes to etch the mirror surface, and the crystal grain size was observed using an optical microscope. As a result, the average crystal grain size was 10 μm for the former and 4 μm for the latter.

Incidentally, a sintered body produced by the same procedure without adding Na ₂ CO ₃ had an average crystal grain size of 12 μm.

Furthermore, in those containing more than 0.5% by weight of Na, a decrease in saturation magnetic flux density and an increase in coercive force were observed.

The above is an example of typical ferrite compositions.
Although the effect of adding and containing Na has been described, the composition of the ferrite is not limited to that shown in the examples, and Mn-Zn ferrite with other compositions and Ni
-The same tendency was observed for Zn ferrite.

In the above-mentioned Na-containing Mn-Zn ferrite and Ni-Zn ferrite, it is desirable to further improve the toughness depending on the purpose of use. Next, improvement in toughness will be explained by giving examples.

Example 4 Final composition ratio: 54.5 mol% Fe ₂ O ₃ , 29.0 mol%
MnO, purity 99.98 to be 16.5 mol% ZnO
% high purity iron oxide, _high purity manganese carbonate, and high purity zinc, plus _Na2CO3 and _ZrO2
was added and wet mixed in a stainless steel pot for 16 hours. Thereafter, a ferrite sample was produced using the same procedure as in Example 1.

On the other hand, for comparison, a ferrite sample was prepared using the same procedure without adding Na ₂ CO ₃ and ZrO ₂ .

A Vickers impression was made on each sample under a load of 200 g for 30 seconds, and the length of the crack that occurred was measured. Then, the relative value of the critical stress intensity factor for each composition was determined, using the value when no Na and Zr were added as a reference (100). The results are shown in FIG. The figures in the figure are relative values.

As is clear from FIG. 3, when Na was in the range of 0.01 to 0.5% by weight and Zr was in the range of 0.005 to 0.5% by weight, the critical stress intensity factor was 105 or more, and the toughness and workability were improved.

In addition, when the amount of Zr exceeds 0.5% by weight, the saturation magnetic flux density of ferrite decreases by more than 10%, and the coercive force decreases by 10%.
% or more. Therefore, in conjunction with the results of Example 1, it is desirable that the amounts of Na and Zr be 0.01 to 0.5% by weight and 0.005 to 0.5% by weight, respectively.

Example 5 Final composition ratio: 54.5 mol% Fe ₂ O ₃ , 29.0 mol%
The same raw materials as in Example 4 were blended so that MnO and ZnO were 16.5 mol%, and Na ₂ CO ₃ was blended so that Na and Zr were 0.01% by weight and 0.005% by weight, respectively.
and ZrO ₂ and changing the amount of Ca,
Various ferrite samples were prepared in the same manner as in Example 4.

Figure 4 shows the relationship between the amount of Ca in ferrite and the critical stress intensity factor (relative value) K. As is clear from the figure, the critical stress intensity factor increases when the amount of Ca is 0.01% by weight. When the amount of Ca was 0.5% by weight, the relative value was 120, which was 20% larger than when no Ca was added. When the amount of Ca is 1% by weight, the value is 121, which not only saturates the effect of improving ductility, but also increases the saturation magnetic flux density by 10 to 10% compared to when no Ca is added.
It decreased by 20%, and the holding power more than doubled.

Therefore, when the amount of Ca is within the range of 0.01 to 0.5% by weight, the toughness of the ferrite containing Na and Zr can be further improved, and a magnetic head material with excellent workability can be obtained.

Example 6 Using the coprecipitated ferrite in Example 2,
A ferrite containing 0.01% by weight of Na, 0.05% by weight of Zr, and 0.01% by weight of Ca was produced in the same manner as in Example 2 by adding Na ₂ CO ₃ , ZrO ₂ and CaCO ₃ . The critical stress intensity factor is set to 100 for ferrite made without Ca,
It was 110. By the way, when the value of ferrite which does not contain Na or Zr is taken as 100, it is 125.

Example 7 Final composition ratio: 51.0 mol% Fe ₂ O ₃ , 18.8 mol%
The raw material was oriented to have NiO and 30.2 mol% ZnO, and Na ₂ CO ₃ , ZrO ₂ , and CaCO ₃ were added thereto, and Na 0.01 wt % and Zr were added using the same procedure as in Example 3.
Ferrite containing 0.05% by weight of Ca and 0.01% by weight of Ca was prepared. The critical stress intensity factor of this ferrite was 105, when that of ferrite without Ca addition was taken as 100. By the way, when the value without the addition of Na, Zr, and Ca was taken as 100, it was 115.

As mentioned above, Na and Zr, as well as Na and Zr, Ca
The toughness of Mn-Zn ferrite and Ni-Zn ferrite can be improved by adding .

Effect of the invention According to the present invention, Mn-Zn ferrite or
Since the Na component is added to the Ni-Zn ferrite, the average crystal grain size of the ferrite can be reduced, and the crystal grain size can be controlled by selecting the amount of Na, so the processing conditions The optimum crystal grain size can be obtained according to the

In addition to the above ferrite, Zr component, Zr component and Ca
By adding the components, the toughness of the ferrite can be further improved and its workability can be improved.

[Brief explanation of the drawing]

Figure 1 shows the relationship between Na content and average grain size in Mn-Zn ferrite, Figure 2 shows the occurrence of cracks due to Vickers indentations, and Figure 3
Figure 4 shows the relationship between Na content, Zr content, and critical stress intensity factor in Mn-Zn ferrite.
FIG. 3 is a diagram showing the relationship between the Ca content and the critical stress intensity factor when the Na content and Zr content are constant in ferrite.

Claims (1)

[Scope of Claims] 1. A polycrystalline ferrite characterized in that 0.01 to 0.5% by weight of Na component is added to Mn-Zn ferrite or Ni-Zn ferrite. 2. A polycrystalline ferrite characterized in that 0.01 to 0.5% by weight of Na component and 0.005 to 0.5% by weight of Zr component are added to Mn-Zn ferrite or Ni-Zn ferrite. 3 Mn-Zn ferrite or Ni-Zn ferrite with 0.01 to 0.5% by weight of Na component and 0.005% of Zr component.
~0.5% by weight, and a polycrystalline ferrite characterized by containing an additional Ca component of 0.01 to 0.5% by weight.