JPH09124362A - Nonmagnetic ceramic and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable sure bonding of a head core to a head slider without causing crack and residual strain when the head slider is bonded to the head core because of the thermal expansion coefficient capable of freely controlling in a prescribed range, by including CaO and Fe2 O3 in a specific molar ratio and including a specific amount of ZnFe2 O4 based on the total amount of CaO and Fe2 O3 . SOLUTION: This ceramic contains CaO and Fe2 O3 in a molar ratio of (45/55) to (67/33) and contains ZnFe2 O4 in an amount of 1-170 pts.wt. based on 100 pts.wt. total amount of CaO and Fe2 O3 . The ceramic contains further one or more kinds of MgO, TiO2 , MnO, SiO2 , ZrO2 and Al2 O3 in an amount of 0.1-3 pts.wt. based on 100 pts.wt. total amount of these three components. The method for producing the ceramic comprises carrying out wet type mixing of raw material powder comprising Fe2 O3 and CaO, calcining the mixture in an oxidative atmosphere, adding ZnO or ZnFe2 O4 thereto and pulverizing the mixture into <=2μm average particle diameter, forming the resultant powder and preliminarily sintering the formed article in an oxidative atmosphere at 1000-1200 deg.C and subjecting the preliminarily sintered material to hot isostatic treatment at the same temperature in an inert gas atmosphere.

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. Recording for hard disk (composite type, thin film type, laminated type, etc.), magneto-optical disc, floppy disc, magnetic tape, or magnetic head slider material used for magnetic recording of audio recorders and video tape recorders. The present invention relates to non-magnetic ceramics for reproducing heads.

[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 slider made of ceramics with glass or the like. 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, and MIG (Metal In Gap) provided with a thin film on the ferrite.
The type is mass-produced.

Further, a composite core in which a part of the core is replaced with a non-magnetic substrate and a magnetic thin film is formed on the non-magnetic substrate is adopted. As a non-magnetic substrate of such a composite core, calcium titanate (CaTiO ₃ ) having high mechanical strength is used.
The non-magnetic substrate of the system is adopted.

On the other hand, as a material of the slider for holding the head core, for example, calcium titanate or barium titanate is used.

[0007]

If the coefficient of thermal expansion of the slider material differs from the coefficient of thermal expansion of the head core,
There is a risk that cracks and residual strain will occur due to the thermal stress when the head core is bonded to the slider, and the bonding will be insufficient, and the head core will fall off the slider and become defective as a magnetic head. 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 thermal expansion coefficient of the high-permeability Mn-Zn ferrite of the material for the head core is 105 to 13
0 × 10 ⁻⁷ / ° C., the thermal expansion coefficient of the composite core is 100
Whereas a ~120 × 10 ^-7 / ℃, calcium titanate which is used as a slider, the thermal expansion coefficient of the barium titanate, respectively 100~120 × 10 ^-7 / ℃,
There was no slider material that was 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.

In a magnetic head for a hard disk or the like, CSS (Contact start / stop) in which the magnetic head floats as the disk rotates.
Since a method called "" is used, the disk and the head come into contact with each other when the disk is started and stopped. Therefore,
If there are pores (holes) in the slider part, lubricant or magnetic powder will adhere to the pore part when sliding, or the deposits will fall off from the pore part, thereby destroying the magnetic medium, data There is a problem in that the magnetic recording device 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 has been 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 calcium oxide and iron oxide to a predetermined value in calcium ferrite, a porcelain for slider of magnetic head having excellent sliding characteristics and excellent thermal expansion coefficient was obtained. It was found that this was caused (see JP-A-5-85807).

However, in this composition system, the coefficient of thermal expansion is 12
It was about 0 to 127 × 10 ⁻⁷ / ° C., which was suitable for the Mn—Zn ferrite core having a large coefficient of thermal expansion.
There is a problem that the coefficient of thermal expansion is too large for the composite core.

[0014]

Therefore, the present invention has been variously studied 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, calcium-based ferrite (CaFe ₂ O ₄ , Ca ₂ Fe) having a large coefficient of thermal expansion
₂ O ₅ ) has a small coefficient of thermal expansion
By adding Fe ₂ O ₄ ), the coefficient of thermal expansion is 100 to 1
It can be freely controlled in a wide range of 26 × 10 ^-7 / ° C. Moreover, since both calcium-based ferrite and zinc-based ferrite have excellent sliding characteristics, the obtained non-magnetic ceramics also have excellent sliding characteristics. It has been found to have characteristics.

Further, it has been found that a composition containing these non-magnetic ceramics and trace components has excellent sinterability, a small pore size, and excellent sliding characteristics.

That is, the nonmagnetic ceramic of the present invention is C
The molar ratio of aO to Fe ₂ O ₃ is 45/55 to 67.
The content of CaFe and Fe ₂ O ₃ is 100 to 100 parts by weight, and ZnFe ₂ O ₄ is contained in an amount of 1 to 17
It is characterized by containing 0 parts by weight.

Here, the molar ratio of CaO and Fe ₂ O ₃ is 4
5/55 to 67/33 is because CaO is 67 mol%
This is because when the amount of Fe ₂ O ₃ increases and Fe ₂ O ₃ decreases below 33 mol%, a small amount of CaO phase is generated in the ceramic, the pore size increases, and the sinterability deteriorates significantly. On the other hand, CaO is less than 45 mol% and Fe
_{This is because when 2} O ₃ is more than 55 mol%, a magnetic ferrite phase is generated and it becomes unsuitable as a non-magnetic ceramic.

Further, the content of ZnFe ₂ O ₄ is 1 to 1
If the amount is less than 1 part by weight, the effect of reducing the coefficient of thermal expansion is poor, while if the amount exceeds 170 parts by weight, the coefficient of thermal expansion becomes too small, less than 100 × 10 ⁻⁷ / ° C., and glass bonding is performed. This is because it may cause the occurrence of cracks.

Ferrite has different magnetic properties depending on the 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 nonmagnetic. Since the calcium-based ferrite and the zinc-based ferrite used in the present invention are generally non-magnetic, a non-magnetic ceramic can be obtained by using them as the main component.

In the non-magnetic ceramic of the present invention, CaFe ₂ O ₄ and Ca ₂ Fe are contained in the ceramic.
It is characterized by having at least one of ₂ O ₅ and a crystal phase of ZnFe ₂ O ₄ . This is because each of the above crystal phases is non-magnetic and is suitable as a material for a magnetic head slider. The presence of these crystal phases can be confirmed by an X-ray diffraction method.

Further, the non-magnetic ceramic of the present invention is
The total of CaO, Fe ₂ O ₃ and ZnFe ₂ O ₄ is 10
0 parts by weight of MgO, TiO ₂ , MnO, Si
It is characterized in that at least one of O ₂ , ZrO ₂ , and Al ₂ O ₃ is contained in a total amount of 0.1 to 3 parts by weight or less. The reason for including these components is to improve the sinterability, but the reason why the total amount of these components is within the above range is that if the total amount is more than 3% by weight, the sinterability deteriorates. , Because the pore size also increases. These sub-components are added separately as a sintering aid, as well as CaCO ₃ and Fe.
_It may be mixed in raw materials such as ₂ O ₃ , ZnO, and ZnFe ₂ O ₄ or due to abrasion of balls such as crushing and mixing.

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
(including a, Na, S, Cl, Mg, Cr, P, Nb, etc.)
Is used as the CaO source, CaCl ₂ , CaCO ₃ , Ca
Fe ₂ O ₄ , Ca ₂ Fe ₂ O _5, etc. are used, and MgO, TiO ₂ , MnO, SiO ₂ , ZrO ₂ and A are used as auxiliary components.
Using l ₂ O ₃ , these are weighed in predetermined amounts. The raw materials are wet-mixed using a ball mill, dried, and the dried raw material is calcined in an oxidizing atmosphere at a predetermined temperature for a predetermined time, and ZnO or separately synthesized ZnF is used as the calcined raw material.
A predetermined amount of e ₂ O ₄ raw material is added, and finely pulverized using an alumina ball, a zirconia ball, or a menor ball so that the average particle diameter becomes 2 μm or less.

Here, the zinc-based ferrite prepared separately is added to the calcined calcium-based ferrite because the coefficient of thermal expansion can be adjusted by the amount of the zinc-based ferrite added, and materials having various coefficients of thermal expansion are added. Is easily manufactured. In addition, MgO, TiO ₂ , Mn
The addition of O, SiO ₂ , ZrO ₂ , and Al ₂ O ₃ subcomponents is not limited to before calcination, but may be included in the raw materials used, added after calcination, or contaminated with balls and liners during the grinding process. Can be added by.

Then, a binder is added to the raw material powder to granulate, followed by press molding at a predetermined pressure and firing, whereby the non-magnetic ceramic of the present invention can be obtained. 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 subjected to hot isostatic pressure (HIP) treatment at 1000 to 1200 ° C. in an inert gas atmosphere. Preferably, such a firing method makes it possible to obtain a sintered body having a pore size of 1 μm or less.

The non-magnetic ceramic of the present invention is not limited to the magnetic head slider, but may be used for a magnetic head spacer,
It can be used in various fields such as magnetic tape guides and parts for micromachines.

[0027]

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,
(Including Cr, P, Nb, etc.) and C as the source of CaO
ACl ₂ , CaCO _3, etc. are used, weighed a predetermined amount so that the final composition is as shown in Table 1, wet-mixed with a ball mill, and dried this raw material at a predetermined temperature in an oxidizing atmosphere at a predetermined temperature. I calcined for an hour.

99% purity synthesized separately for the raw material after calcination
A predetermined amount of the above ZnFe ₂ O ₄ raw material is added, and finely pulverized using an alumina ball, a zirconia ball, or a menoball so that the average particle diameter becomes 2 μm or less. In addition, zirconia, alumina, silica, etc. are converted into 3 by this pulverization.
May be mixed by weight% or less. After adding a binder to this and granulating, it was press-molded at a pressure of 0.8 to 2.0 ton / cm ² .

Then, it was fired at a predetermined temperature under atmospheric pressure in an oxidizing atmosphere. The obtained sintered body is heated from 1000 ° C to 1
HIP treatment was carried out at 2000 ° C. in an argon atmosphere at 200 ° C.

[0030]

[Table 1]

The obtained sample was examined for bulk specific gravity, coefficient of thermal expansion, porosity and sinterability, and the results are shown in Table 2.

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 using 1 μm diamond abrasive grains, and the sinterability was evaluated by the water absorption rate.

From this result, it is clear that No. 3 which is within the scope of the present invention. 2, 5 to 11 and 13 have a coefficient of thermal expansion of 100.
The average diameter of the pores is 2 to 126 × 10 ^-7 / ° C.
It was as small as μm or less and had good sinterability. On the other hand, no. No. 1 was inferior in sinterability because CaO was slightly large, and No. No. 14 was not suitable as a nonmagnetic ceramic because it contained a large amount of Fe ₂ O ₃ .

[0034]

[Table 2]

Next, each sample in Table 2 was processed into a slider shape having two rails and set on a disk via a mounting metal fitting. Then, the maximum number of rotations of the magnetic disk is set to 3600 rpm, and rotation and stop are repeated (CSS).
The test was performed. The presence or absence of scratches on the medium and the slider on the magnetic disk side was examined every 5000 CSS cycles, and the results are shown in Table 3.

From this result, N within the range of the present invention is obtained.
o. It can be seen that Nos. 2, 5 to 11 and 13 have excellent sliding characteristics.

[0037]

[Table 3]

Example 2 Fe ₂ O ₃ , CaO and ZnFeO similar to those in Example 1 were used.
_For 100 parts by weight of the main component consisting of ₄ , MgO, TiO
_{At least one of 2} , MnO, SiO 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. Thereafter, each sample was obtained in the same manner as in Example 1 above.

[0039]

[Table 4]

The obtained sample was examined for bulk specific gravity, thermal expansion coefficient, pore ratio and sinterability in the same manner as in Example 1. The results were as shown in Table 5.

According to Table 5, MgO, TiO ₂ , MnO, S
It was found that the inventive examples (Nos. 15 to 24) containing 3 parts by weight or less of iO ₂ and ZrO ₂ had good sinterability and a small pore size.

[0042]

[Table 5]

Further, Table 6 shows the results of the CSS test performed in the same manner as in Example 1. From this result, No. within the scope of the present invention. It was found that the sliding characteristics of 15 to 24 were good.

[0044]

[Table 6]

[0045]

As described in detail above, the non-magnetic ceramic of the present invention is used.
The mix is CaO and Fe_TwoO_ThreeThe molar ratio of each other is 45
/ 55-67 / 33 content, these CaO and F
e_TwoO _ThreeZnFe to 100 parts by weight in total_TwoO_FourTo
By including 1 to 170 parts by weight, the coefficient of thermal expansion is 10
0 to 126 x 10^-7Can be freely adjusted within the range of / ° C.
Therefore, when a magnetic head slider is formed, the head core
The difference in thermal expansion between the head core and the slider is reduced.
When wearing it, the head core is slid without causing cracks or residual strain.
It can be surely adhered to the idder.

Further, since a non-magnetic ceramic having a good generation rate of pores and good sinterability can be obtained, if a slider for a magnetic head is formed from this ceramic, lubricant, magnetic powder, etc. will not adhere during CSS. Therefore, it is possible to reliably prevent the destruction of the recording data and the damage of the head, and to significantly improve the reliability of the magnetic recording device.

Further, according to the present invention, MgO, TiO ₂ , MnO, SiO ₂ , ZrO ₂ , and A are added to the above components.
By including at least one type of l ₂ O _{3 in} a total amount of 3 parts by weight or less, the sinterability is improved, the pore size is reduced, and the sliding characteristics can be improved.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location H01F 1/00 H01F 1/00 B

Claims (6)

[Claims] 1. A molar ratio of CaO and Fe ₂ O ₃ to each other is 45.
/ 55-67 / 33 content, these CaO and F
A non-magnetic ceramic containing 1 to 170 parts by weight of ZnFe ₂ O ₄ with respect to 100 parts by weight of e ₂ O ₃ in total. 2. CaFe ₂ O ₄ and Ca ₂ Fe _{2 in the} sintered body
The nonmagnetic ceramic according to claim 1, which has at least one kind of O ₅ and a crystal phase of ZnFe ₂ O ₄ . 3. CaO, Fe ₂ O ₃ and ZnFe ₂ O
₄ to 100 parts by weight in total, MgO, TiO ₂ , M
The non-magnetic ceramics according to claim 1, which contains 0.1 to 3 parts by weight in total of at least one of nO, SiO ₂ , ZrO ₂ , and Al ₂ O ₃ . 4. The molar ratio of CaO and Fe ₂ O ₃ to each other is 45.
The mixture is added and mixed in the range of / 55 to 67/33 and calcined, and ZnFe ₂ O ₄ is added to 1 to 100 parts by weight of the obtained calcined body.
A method for producing non-magnetic ceramics, which comprises the steps of adding 170 parts by weight and mixing and pulverizing, and the step of molding and firing this mixed powder. 5. The method for producing a non-magnetic ceramic according to claim 4, wherein the firing step comprises a step of pre-firing the molded body in an oxidizing atmosphere and then subjecting it to hot isostatic pressing. 6. The above CaO, Fe ₂ O ₃ and ZnFe ₂ O
₄ to 100 parts by weight in total, MgO, TiO ₂ , M
_{nO, SiO 2, ZrO 2,} Al 2 production process according to claim 4 nonmagnetic ceramic according to at least one of O ₃ characterized by mixing comminuted with addition total 0.1 to 3 parts by weight.