JPH0122229B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a nonmagnetic substrate material suitable for forming a magnetic thin film used in a magnetic head or the like. (Prior art) In recent years, there has been a strong demand for higher recording density in the field of magnetic recording, and the conventional γ-Fe ₂ O ₃
Co-doped materials are also used to obtain high coercive force when coated on disks with resin. Furthermore, in order to increase the magnetic recording density, Ni-P electroless plating and Co-
Recording media sputtered with Pt, Co-Ni-Pt, Co-Ni, etc. are beginning to be used. On the other hand, as recording media for perpendicular magnetic recording, coating type hexagonal Ba ferrite with large C-axis anisotropy,
Among thin film types, Co-Cr magnetic films are seen as promising and are being developed. Furthermore, since conventional magnetic heads formed from ferrite cores are not compatible with magnetic heads, development of magnetic heads with new configurations is underway. For magnetic heads for high-density magnetic recording, those using Co--Nb--Zr based materials as the core are considered promising. Although the addition of Nb to Co-Zr lowers the saturation magnetic flux density, it increases the magnetic permeability, which improves the magnetic properties in a comprehensive sense. Co-Nb-Zr was deposited on the magnetic substrate by sputtering.
A method has been put into practical use in which a film is formed and a gap portion is formed by bonding. Also,
Since a Co-Nb-Zr film alone lacks magnetic flux density, ferrite is often used as a backup material, but in any case, a nonmagnetic substrate must be used on the surface facing the magnetic disk surface. However, the glasses currently in use have problems in terms of wear resistance or sliding properties. Therefore, a new non-magnetic substrate other than glass is required. (Problems to be Solved by the Invention) As mentioned above, since a Co-Nb-Zr film is directly formed on a non-magnetic substrate for a magnetic head, it is necessary to satisfy the following characteristics. be. First, the coefficient of thermal expansion is 100× of the Co-Nb-Zr film.
It must be equivalent to 10 ^-7 °C ^-1 . If the difference in thermal expansion coefficient between the substrate material and the thin film is too large, problems such as peeling and cracking of the film may occur during cooling after film formation. Therefore, the difference in thermal expansion coefficient is at most ±10×
It is necessary that the temperature is 10 ^-7 °C ^-1 , preferably ±5×10 ^-7 °C ^-1 . Second, since the film is directly formed, the surface condition of the substrate is extremely important, and it is desirable that the pore size be within 1% at most, and that surface roughness and micro waviness be as small as possible. Thirdly, the magnetic disk must not be damaged during sliding, that is, it must have good sliding characteristics. Fourthly, good workability is required when processing into a head shape. SUMMARY OF THE INVENTION An object of the present invention is to provide a ceramic substrate for a magnetic head that satisfies the above-mentioned required characteristics for a substrate. (Means for Solving the Problems) In order to achieve the above object, the present invention contains 10 to 30 wt% of yttrium oxide and 10 to 30 wt% of aluminum oxide.
0.5 to 10 wt%, one or more of MnO ₂ , TiO ₂ , and Fe ₂ O ₃ or 0.2 to 10 wt % of SiO ₂ ,
This is a zirconia substrate for a magnetic head, characterized in that the remainder is substantially cubic zirconium oxide. The present invention was achieved by discovering that the first and third required characteristics can be satisfied by using stabilized (cubic crystal) zirconia as a substrate material. In other words, the coefficient of thermal expansion of zirconium oxide (ZrO ₂ ) varies somewhat depending on the amount of yttrium oxide (Y ₂ O ₃ ), but it is between 90 and 110.
×10 ^-7 °C, and the adhesion when an amorphous Co-Nb-Zr film is formed is very good. Furthermore, ZrO ₂ has extremely superior sliding properties compared to other ceramics such as aluminum oxide (Al ₂ O ₃ ), and also has good wear resistance. As is well known, there are two main existing uses for ZrO ₂ . One is to add a small amount of stabilizers such as MgO, CaO, and Y ₂ O ₃ to fine ZrO ₂ powder so that the high-temperature phase, tetragonal, remains until room temperature, and its stress-induced transformation provides high strength and toughness. The resulting partially stabilized zirconia. The other type is stabilized zirconia, which is used in oxygen sensors that utilize oxygen ion conductivity at high temperatures by adding a large amount of stabilizer. As described above, the properties of ZrO ₂ vary greatly depending on the amount of stabilizer. Partial stabilization
Although ZrO ₂ has fine grains and can easily be obtained with high density, it is unsuitable as a substrate material because the resistance during cutting is too high, which violates the fourth requirement of good workability. It is. On the other hand, the workability of stabilized zirconia, which is mainly composed of cubic crystals, is significantly improved compared to partially stabilized zirconia, but cubic crystals tend to cause grain growth and leave pores inside the grains, so high-density products cannot be used. The disadvantage is that it is difficult to obtain. In the present invention, stabilized zirconia contains MnO ₂ ,
High density is achieved by adding TiO ₂ , Fe ₂ O ₃ , or SiO ₂ sintering aid.
That is, all of these oxides form a solid solution in ZrO ₂ and promote sintering of ZrO ₂ , so they are effective in increasing the density. On the other hand, since the addition of the above-mentioned oxide promotes grain growth, there is a possibility that large pores that cannot be eliminated remain within the grains. Therefore, in the present invention, Al ₂ O ₃ that does not form a solid solution with ZrO ₂ is added, and the grain growth of cubic ZrO ₂ is suppressed by its dispersion. In this way, in the present invention, by using Al ₂ O ₃ and a sintering aid in combination, the effects of both promoting sintering and suppressing grain growth can be seen, so even pressureless sintering alone can achieve a relative density of 96 to 97%. A sintered body of about 100% can be obtained. By further HIPing this, we were able to achieve a relative density of over 99%. Furthermore, in implementing the present invention, in order to obtain desired effects, it is necessary to select the composition, sintering conditions, etc. within predetermined ranges, as described below. The amount of Y ₂ O ₃ added as a stabilizer is preferably 10 to 30 wt%, but the reason is that if it is less than 10 wt % _, residual tetragonal crystals will exist, resulting in _increased cutting resistance. If it exceeds 30wt%, it becomes difficult to increase the sintered density and the cubic crystal structure
This is because Y ₄ Zr ₃ O ₁₂ and the like precipitate and adversely affect the sliding properties. The amount of Al ₂ O ₃ added is preferably 0.5 to 10 wt%. This is because if it is less than 0.5wt%, it will not be dispersed in ZrO ₂ and will not have the effect of suppressing grain growth, and if it exceeds 10wt%, the hardness will increase and ZrO ₂
This is because the sliding properties of the material will be impaired.
The amount of sintering aids such as MnO ₂ , TiO ₂ , Fe ₂ O ₃ or SiO ₂ must be limited to 0.2 to 10 wt%.
This is because if it is less than 0.2wt%, it has no effect on improving the sintered density as an auxiliary agent, and if it exceeds 10wt%, contrary to the case of Al ₂ O ₃ , it decreases the hardness of ZrO ₂ . It is. Further, in the present invention, Al ₂ O ₃
If a large amount of sintering aid is added, the thermal expansion coefficient will decrease to 90×10 ^-7 ℃ ^-1 or less, and 100±10×10 ^-7 ℃
It is inappropriate to add too much because it exceeds the target range of ^-1 of the present invention. As for the sintering conditions, firing in the air at 1300 to 1600°C is desirable. This is because sintering is insufficient below 1300℃,
This is because the density does not increase, and above 1600℃
This is because grain growth cannot be suppressed even if Al ₂ O ₃ is contained. In addition, the HIP condition is 1200 ~
Preferably 1500℃ and 1000 to 1500 atm. In addition, the zirconia ceramics in the present invention contains impurities such as MgO, HfO ₂ and CaO in total.
Even if the content is 2wt% or less, the effects of the present invention will not be diminished in any way. In the present invention, in order to stabilize ZrO ₂
Y ₂ O ₃ is added, but the method of addition is
ZrO ₂ and Y ₂ O ₃ powders may be mixed and sintered directly, or a powder obtained by coprecipitation and calcining from a solution state may be used. (Example) The zirconia substrate for a magnetic head of the present invention will be explained in more detail with reference to Examples. Y ₂ O ₃ to fine ZrO ₂ powder with a secondary particle size of 0.5 μm,
Al ₂ O ₃ , MnO ₂ , TiO ₂ , SiO ₂ as sintering aids,
Fe ₂ O ₃ was blended in the proportions shown in the table and mixed in a ball mill using ethanol as a solvent. Polyvinyl alcohol (PVA) and polyethylene glycol (PEG) were added as binders to this, granulated with a spray dryer, molded, and then sintered under the conditions shown in Table 1. After measuring the density using the underwater displacement method, it was made into a 3" wafer by surface grinding and mirror lapping. After measuring the surface roughness, amorphous Co-10at%Nb-3.5at
%Zr film (the remainder being Co) was formed by sputtering, and the adhesion of the film was evaluated. The cutting resistance was measured by measuring the stress applied to the blade of the peripheral slicer using a piezoelectric element. The above results are shown in Table 2. Nos. 1, 5, 6, 9, 10, 13, 14, and 17 in the table are comparative examples.

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[Table] In Nos. 1 to 5, 5wt% of Al ₂ O ₃ and 5wt% of TiO ₂ were added.
This is a case where the amount of Y ₂ O ₃ is changed. In No. 1, which has a small amount of Y ₂ O ₃ , the relative density is close to the theoretical density and the grain size is fine, but the cutting resistance is significantly larger than in other cases, making it unsuitable as a substrate material. be. When the amount of Y ₂ O ₃ is increased, the cutting resistance decreases, but when it is too large as in No. 5, the density decreases rapidly. In Nos. 6 to 9, 15 wt% of Y ₂ O ₃ and 5 wt % of TiO ₂ were added, and the amount of Al ₂ O ₃ was changed. When the amount of Al ₂ O ₃ is small as in No. 6, the crystal grain size is 15 to 20 μm.
However, as Al ₂ O ₃ is increased, the crystal grains become finer and chipping during cutting becomes smaller. However, if the amount is too large, the coefficient of thermal expansion becomes small and the adhesion of the film deteriorates. No.10 to ₁₃ added 15wt% of _{Y2O3 and} 5wt% of _Al2O3 .
The amount of TiO ₂ was changed. If the amount of TiO ₂ is small, sufficient sintered density cannot be obtained. _TiO2
If the amount is increased, sufficient density will be obtained, but if it is too large, the coefficient of thermal expansion will become small and the hardness will also become small. Nos. 14 to 17 are cases where the sintering temperature was changed.
At 1200℃, the density is as low as 95%. At 1,300°C, it is sufficiently densified to the extent required for HIP, but at temperatures above 1,600°C, grain growth cannot be suppressed even if Al ₂ O ₃ is added. In No. 18 to 21 _{, MnO 2 ,} SiO ₂ ,
Although there were differences in particle size and color of the sintered bodies when Fe ₂ O ₃ etc. were added, sufficient density was obtained in all cases. (Effects of the Invention) As described above, the zirconia substrate of the present invention has excellent sliding properties, high density, workability, etc., and is a suitable material as a substrate for a magnetic head.

Claims (1)

[Claims] 1. 10 to 30% yttrium oxide, 0.5 to 10% aluminum oxide, one or more of MnO ₂ , TiO ₂ , and Fe ₂ O ₃ , or 0.2 _% SiO 2 by weight.
A zirconia substrate for a magnetic head, characterized in that the zirconia substrate contains ~10% of zirconium oxide, with the remainder being substantially cubic zirconium oxide. 2. The zirconia substrate for a magnetic head according to claim 1, which has a coefficient of thermal expansion of 90 to 110×10 ^-7 °C. 3. The zirconia substrate for a magnetic head according to claim 1 or 2, which has a density of 99% or more of the theoretical density.