JPH09183655A - Non-magnetic ceramic and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a non-magnetic ceramic low in generating rate of pores and good in sintering property by subjecting a compact to preburning in an oxidizing atmosphere and to hot hydrostatic pressing after forming a powdery mixture of a starting material containing CaO, Fe2 O3 and ZnO in a prescribed shape. SOLUTION: This non-magnetic ceramic is produced by subjecting a compact obtained by mixing and grinding a starting material containing 9-41wt.% CaO, 58-78wt.% Fe2 O3 and 0.3-21wt.% ZnO and containing at need 0.1-3 pts.wt. in total of >=1 kind among MgO, TiO2 , MnO, SiO2 , ZrO2 and Al2 O3 per 100 pts.wt. above main components and forming this mixture in a prescribed shape to the preburning in the oxidizing atmosphere and to the hot hydrostatic pressing. In this way, the ceramic having an excellent sliding characteristic is obtained by adding the ZnO small in the coefft. of thermal expansion to a Ca based ferrite large in the coefft. of thermal expansion since the coefft. of thermal expansion is freely controlled within a wide rang of 100-126×10<-7> / deg.C and both components are excellent in sliding characteristic.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic substrate for magnetic heads, sliders for various magnetic heads, spacers for magnetic heads, magnetic tape guides, non-magnetic ceramics used for parts for micromachines, and more particularly to computers. Non-ideal for hard disk (composite type, thin film type, laminated type, etc.), magneto-optical disk, floppy disk, magnetic tape, or magnetic head slider used for magnetic recording of audio recorders and video tape recorders. It relates to magnetic ceramics.

[0002]

2. Description of the Related Art In a magnetic recording apparatus using a magnetic head, the recording density and the capacity have been increasing, and accordingly, the magnetic head is required to have a high linear density and a high track density. Is required.

In recording on a magnetic disk using such a magnetic head, a composite slider is adopted as one of methods for achieving high linear density and high track density corresponding to high capacity. In a so-called composite type magnetic head, a magnetic head core is bonded to a ceramic slider. It should be noted that the magnetic head core and the slider are adhered by melting the glass placed between the two with the atmosphere kept at a high temperature of about 400 ° C.

As the head core, Mn-Zn type ferrite having a high magnetic permeability is generally used.
MIG (Metal In Ga) with a thin film formed on it
The p) type is mass-produced.

Further, a composite core in which a part of the head core is replaced with a non-magnetic substrate and a magnetic thin film is formed on the non-magnetic substrate is also adopted. As a non-magnetic substrate forming such a composite core, calcium titanate (C
An aTiO ₃ ) type material is used.

On the other hand, as a material of the slider holding the head core, for example, calcium titanate (CaT) is used.
iO ₃ ) and barium titanate (BaTiO ₃ ) are used.

[0007]

If the coefficient of thermal expansion of the slider is different from the coefficient of thermal expansion of the head core, thermal stress at the time of bonding the head core to the slider causes cracks and residual strain, resulting in insufficient bonding. Therefore, the head core may fall off the slider, and the magnetic head may become defective. In order to reliably prevent such defective products, it is necessary to match the thermal expansion coefficient of the slider with the thermal expansion coefficient of the head core.

However, the coefficient of thermal expansion of the high-permeability Mn-Zn ferrite, which is the material of the head core, is 105 to 105.
130 × 10 ^-7 / ° C, the coefficient of thermal expansion of the composite core is 1
To 00-120 in the range of × 10 ^-7 / ° C., calcium titanate which is used as a slider, the thermal expansion coefficient of the barium titanate, respectively 100 to 120 × 10 ^-7 /
There was no slider material having a temperature expansion coefficient of about 80 to 100 × 10 ⁻⁷ / ° C., which was smaller than the thermal expansion coefficient of the head core and could cover the entire range of the thermal expansion coefficient of the head core.

Further, a magnetic head for a hard disk or the like employs a method called CSS (Contact start / stop) in which the magnetic head floats as the disk rotates, so that the disk and the head are separated when the disk is started and stopped. Contact. Therefore, if there are pores (holes) in the slider part, lubricant or magnetic powder may adhere to the pore part when sliding, or the deposits may fall off from the pore part, thereby destroying the magnetic medium. However, there is a problem in that the data is destroyed and the head is damaged, and the reliability of the magnetic recording device is significantly reduced.

Particularly in recent years, the magnetic film of the magnetic disk has become thin, and the reliability is deteriorated even if the sliding property is slight, so that a slider material having a small pore size is required. There is.

Further, there is also a problem that the calcium titanate type slider has a poor sliding property for some disk media.

On the other hand, the present inventor has conducted various studies in order to obtain a non-magnetic ceramic for a magnetic head slider which can be applied to a head core having a large thermal expansion coefficient and is excellent in slidability with a magnetic medium. As a result of stacking, by specifying the molar ratio of CaO and Fe ₂ O _{3 in} the Ca-based ferrite to a predetermined value, the non-magnetic ceramics for the magnetic head slider have excellent sliding characteristics and excellent thermal expansion coefficient. It has been found that the above can be obtained (see Japanese Patent Application Laid-Open No. 5-85807).

However, although this composition system was able to cope with the head core of Mn-Zn ferrite having a large thermal expansion coefficient, there was a problem that the thermal expansion coefficient was too large for the above composite core.

[0014]

Therefore, the present inventor has made various studies in order to obtain a non-magnetic ceramic for a magnetic head slider which can be applied to the above composite core and is excellent in slidability with a magnetic medium. As a result of stacking, Ca-based ferrite (CaO ・ Fe ₂ O ₃ or 2CaO
・ Fe ₂ O ₃ ) has a small coefficient of thermal expansion
O) is added to obtain a thermal expansion coefficient of 100 to 126 × 1.
It can be freely controlled in a wide range of 0 ^-7 / ° C, and since both Ca-based ferrite and zinc oxide (ZnO) have excellent slidability, the nonmagnetic ceramics obtained also have excellent sliding properties. It has been found to have characteristics.

That is, the composition of the nonmagnetic ceramics of the present invention is 58 to 78% by weight of iron oxide (Fe ₂ O ₃ ), 9 to 41% by weight of calcium oxide (CaO) and zinc oxide (Zn).
O) is contained in an amount of 0.3 to 21% by weight.

Further, the present invention is based on 100 parts by weight of the above main component, MgO, TiO ₂ , MnO, SiO ₂ and ZrO.
₂ , 0.1 to 3 parts by weight in total of at least one of Al ₂ O ₃ is contained.

Here, 58 to 78% by weight of Fe ₂ O ₃ and C
The content of aO is 9 to 41% by weight because CaO is 41% by weight.
When the amount is larger than the above, a small amount of CaO phase is generated in the ceramic, the pore size is increased, and the sinterability is remarkably deteriorated. On the other hand, if Fe ₂ O ₃ is more than 78% by weight, a magnetic ferrite phase is generated and it becomes unsuitable as a non-magnetic ferrite.

Furthermore, the ZnO content of 0.3 to 21% by weight means that the effect of reducing the coefficient of thermal expansion of the Ca-based ferrite is small if it is less than 0.3% by weight, while the coefficient of thermal expansion is more than 21% by weight. This is because the coefficient becomes too small, less than 100 × 10 ⁻⁷ / ° C., which causes cracks during glass bonding, which is not preferable.

Ferrite has different magnetic properties depending on its crystal structure, and Mn-Zn ferrite and Ni-Zn ferrite exhibit ferromagnetism because their crystals have an inverse spinel structure, but they have a positive spinel structure or a corundum type. Ferrite having a crystal structure does not exhibit ferromagnetism and becomes a non-magnetic material.
Since the Ca-based ferrite used in the present invention is generally a non-magnetic material, by using it as a main component,
It can be a non-magnetic ceramic.

Further, with respect to the above main components, MgO, Ti
The total content of at least one of O ₂ , MnO, SiO ₂ , ZrO ₂ , and Al ₂ O ₃ is 0.1 to 3 parts by weight.
This is to improve the sinterability. This total amount is within the above range because MgO, TiO ₂ , MnO, SiO ₂ , Z
This is because if at least one of rO ₂ and Al ₂ O ₃ is contained in a total amount of more than 3 parts by weight, the sinterability deteriorates and the pore size increases. These subcomponents are separately added as a sintering aid, and CaO, Fe ₂ O ₃ and ZnO are also added.
It may be contained in the raw material such as, or may be mixed due to abrasion of the crushed balls during the crushing and mixing steps.

Further, the method for producing the non-magnetic ceramics of the present invention is as follows.

First, for example, commercially available Fe ₂ O ₃ having a purity of 99% or more (Si, Al, Mn, C as impurities
a, Na, S, Cl, Mg, Cr, P, Na, Nb, etc.) and CaCl ₂ and CaC as CaO sources.
O ₃ , CaFe ₂ O ₄ , Ca ₂ Fe ₂ O _5, etc. are used,
A predetermined amount of these are weighed, and then wet mixed using a ball mill. This is dried, and the raw material after drying is calcined at a predetermined temperature for a predetermined time in an oxidizing atmosphere, and the raw material after calcination is Z
A ZnO raw material is added in a predetermined amount as an nO source, and finely pulverized using an alumina ball, a zirconia ball, or a menoball so that the average particle diameter becomes 2 μm or less. Adding separately prepared ZnO to the calcined Ca-based ferrite here makes it possible to adjust the coefficient of thermal expansion by adjusting the amount of ZnO added, which makes it possible to easily manufacture materials having various coefficients of thermal expansion. Because.

The addition of ZnO is not limited to after calcination, and it is also possible to obtain a raw material powder by weighing out a predetermined amount of Fe ₂ O ₃ , CaO and ZnO, mixing and pulverizing them.

Then, a binder is added to this raw material powder to granulate it, followed by press molding at a predetermined pressure and firing to obtain the non-magnetic ceramic of the present invention. Particularly, at the time of this firing, 1000 to 1 in an oxidizing atmosphere
After firing at a normal pressure of 200 ° C. to obtain a pre-sintered body having a relative density of 95% or more, the pre-sintered body is hot isostatically pressed (HIP) at 1000 to 1200 ° C. in an inert gas atmosphere. Treatment is preferable, and a sintered body having a pore size of 1 μm or less can be obtained by such a firing method.

The nonmagnetic ceramics of the present invention can be used not only in sliders for various recording / reproducing heads but also in various fields such as magnetic head spacers, magnetic tape guides, and parts for micromachines.

[0026]

Example 1 Commercially available Fe ₂ O ₃ having a purity of 99% or more (Si, Al, Mn, Ca, Na, S, Cl, Mg as impurities,
Cr, P, Na, Nb, etc.), CaCl ₂ , CaCO _3, etc. are used as the CaO source, and ZnO having a purity of 99% or more is weighed in a predetermined amount so that the final composition is as shown in Table 1. The mixture was wet mixed using a ball mill, dried, and the dried raw material was calcined at a predetermined temperature for a predetermined time in an oxidizing atmosphere.

The raw material after calcination was finely pulverized using alumina balls, zirconia balls, or menor balls so that the average particle diameter was 2 μm or less. In addition, ZrO
₂ , Al ₂ O ₃ , SiO _2, etc. may be mixed in a total of 3% by weight or less.

A binder was added to the obtained raw material for granulation, and then press molding was performed at a pressure of 0.8 to 2.0 ton / cm ² . Then, it was fired at a predetermined temperature under normal pressure in an oxidizing atmosphere. 1000-120 the obtained sintered body
HIP treatment was performed at 0 ° C. in an argon atmosphere at 2000 atm. The obtained sample was examined for bulk specific gravity, coefficient of thermal expansion, porosity, and sinterability. The results are shown in Table 1.

Here, the bulk specific gravity was determined by the Archimedes method in water, and the thermal expansion coefficient was determined by a thermal expansion coefficient measuring device. The generation rate of pores was evaluated by measuring the pore diameter generated on the final lap surface by 1 μm diamond abrasive grains.

From the results of Table 1, No. 1 and 13 are CaO
The sinterability is inferior because there is a little more, and No. 6
Since Nos. 7 and 7 contained a large amount of Fe ₂ O _{3, they} were not suitable as nonmagnetic ceramics.

In contrast to these, 2-5, 8-12,
15 to 18 are non-magnetic ceramics within the scope of the present invention, and have a coefficient of thermal expansion of 128 to 100 × 10 ⁻⁷ / ° C., respectively.
, And the rate of occurrence of pores and sinterability were good.

[0032]

[Table 1]

Next, each sample in Table 1 was processed into a slider shape having two rails and set on a disk through a mounting metal fitting. Then, the maximum rotation number of the disk was set to 3600 rpm, and rotation and stop (CSS) were repeated. The presence or absence of scratches on the disk and the head was checked every 5000 times of this CSS. The results are shown in Tables 2 and 3.

From this result, No. 2-5, 8-12,
It can be seen that in Examples 15 to 18 of the present invention, the number of CSS times until scratches are generated on the medium or the slider is large, and the sliding characteristics are excellent.

[0035]

[Table 2]

[0036]

[Table 3]

Example 2 Similar to Example 1, the main components of Fe ₂ O ₃ , CaO and ZnO were used, but MgO, TiO ₂ , MnO and Si were used.
At least one of O ₂ , ZrO ₂ , and Al ₂ O ₃ was weighed so as to have the content shown in Table 4, and then wet mixed using a ball mill. Others were obtained in the same manner as in Example 1 above. The obtained sample was examined for bulk specific gravity, coefficient of thermal expansion, porosity, and sinterability in the same manner as in Example 1.
The results are as shown in Table 5.

According to Table 5, MgO, TiO ₂ , MnO, S
It was found that the sinterability was improved and the pore size was decreased by containing 0.1 to 3 parts by weight of iO ₂ , ZrO ₂ , and Al ₂ O ₃ .

Further, as shown in Table 6 as a result of the CSS test performed in the same manner as in Example 1, it was found that the sliding characteristics were also good.

[0040]

[Table 4]

[0041]

[Table 5]

[0042]

[Table 6]

[0043]

As described in detail above, the nonmagnetic ceramics of the present invention contain 9 to 41% by weight of CaO, 58 to 78% by weight of Fe ₂ O ₃ , and 0.3 to 21% by weight of ZnO. By including it, the coefficient of thermal expansion can be made close to that of the material for the head core.Therefore, if the slider for the magnetic head is configured, the head core can be securely bonded without causing cracks or residual strain when bonding. be able to.

Further, since a non-magnetic ceramic having a good generation rate of pores and good sinterability can be obtained, a slider for a magnetic head does not cause a lubricant, magnetic powder, or the like to adhere during CSS, so that recording data can be recorded. It is possible to reliably prevent breakage and breakage of the head and significantly improve the reliability of the magnetic recording device.

Further in accordance with the present invention, the above main component 100
For parts by weight, MgO, TiO ₂ , MnO, SiO ₂ , Z
At least one of rO ₂ and Al ₂ O ₃ is 0.1 to 3 in total.
By including the weight part, the sinterability is improved, the pore size is reduced, and the sliding property can be improved.

Claims (3)

[Claims] 1. A nonmagnetic ceramic containing 9 to 41% by weight of CaO, 58 to 78% by weight of Fe ₂ O ₃ , and 0.3 to 21% by weight of ZnO. 2. MgO, T based on 100 parts by weight of the main component
The non-magnetic ceramics according to claim 1, which contains 0.1 to 3 parts by weight in total of at least one of iO ₂ , MnO, SiO ₂ , ZrO ₂ , and Al ₂ O ₃ . 3. Contains 9 to 41% by weight of CaO, 58 to 78% by weight of Fe ₂ O ₃ , and 0.3 to 21% by weight of ZnO, and if necessary, to 100 parts by weight of these main components. M
gO, TiO ₂ , MnO, SiO ₂ , ZrO ₂ , Al ₂
A raw material containing 0.1 to 3 parts by weight in total of one or more kinds of O ₃ is mixed and pulverized, and the mixed powder is molded into a predetermined shape, and the obtained molded body is pre-fired in an oxidizing atmosphere to obtain hot isostatic pressure. A method for producing a non-magnetic ceramic, comprising a step of applying a pressure treatment.