JPH0121112B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to the composition of zirconia ceramics suitable for use in substrates of various electronic devices, such as sliders of thin film magnetic heads and substrates of magnetic recording disks, as well as heat insulating materials. Ceramics used in such applications are first required to have excellent machinability. That is, it is required that there is little cutting resistance during machining and that there is no clogging of the cutting blade or the like. Further, during processing, crystal grains may fall off in the processed portion, but it is desirable that this falling off portion be as small as possible. For this purpose, it is desirable that the crystal grains be small. In addition, in these applications, it is necessary to have excellent sliding properties, but
Al ₂ O ₃ -TiC ceramics had poor sliding properties. Therefore, the present invention proposes zirconia-based ceramics that have good workability and excellent sliding properties. The zirconia ceramics of the present invention contains 0.4 to 26.3 wt% of carbide of at least one element selected from groups a, a, and a of the periodic table, and 0.34 wt% of alumina.
~22.5wt%, with the remainder consisting essentially of zirconia. Desirably, the amount of carbide is 0.72 to 7.2wt%, and the amount of alumina is 0.8 to 8.1wt%.
include. It is thought that by dispersing carbide fine particles, particularly TiC fine particles and alumina fine particles, in the zirconia phase, the growth of the crystal grains of the zirconia phase is prevented and the crystal grains of the matrix are made finer. Normally acceptable level of impurity
SiO ₂ and Fe ₂ O ₃ can be contained, but
It is desirable that the amount of Fe ₂ O ₃ be 0.1 wt% or less.
The amount of SiO ₂ is not a problem up to 5wt%. Also,
Y ₂ O ₃ , CaO, MgO, etc., which are normally thought to be solid-solved in the zirconia phase, partially precipitate and become dispersed particles, or the added TiC
It may be dispersed in the zirconia phase as fine particles bonded or reacted with Al ₂ O ₃ or the like, but this is not a problem. As mentioned above, Al ₂ O ₃ and TiC are dispersed in the zirconia phase and prevent the crystal grains from becoming coarse, but at the same time, when cutting zirconia ceramics, the high hardness carbide acts as a dressing. , to prevent clogging of the diamond plate. The zirconia phase is preferably a stabilized zirconia phase, that is, cubic zirconia.
Cubic zirconia has excellent sliding properties. To stabilize the zirconia phase, Y ₂ O ₃ ,
Add stabilizers such as MgO and CaO. Zirconia without these stabilizers can be used at high temperatures (2400℃).
above), it is a cubic crystal (C-phase), but when the temperature is lowered in the range of 2400℃ to about 1200℃, it is a tetragonal crystal (t-phase).
It becomes a monoclinic crystal (m-phase) at room temperature (approximately 1200℃ or less). Therefore, when the amount of stabilizer is extremely small, zirconia becomes m-phase at room temperature, but when the amount of stabilizer is increased, t-phase exists at room temperature, and even more stabilizer is added. If it increases, it will exist in the C-phase even at room temperature. Therefore, in the zirconia ceramic of the present invention, it is desirable that the zirconia phase contains a stabilizer sufficient to exist as cubic zirconia even at room temperature. In the case of Y ₂ O ₃ , it is desirable that the zirconia phase contains 5 to 20 mol %, with the remainder being substantially ZrO ₂ . However, MgO
There is no problem even if CaO is also contained at the same time. If such a stabilizer is included in excess, ZrO ₂ such as Y ₄ Zr ₃ O ₁₂ may be present in cubic zirconia.
- Y ₂ O ₃ compounds precipitate, resulting in deterioration of sliding properties,
This leads to a decrease in strength. Therefore, more than 20 mol%
Containing Y ₂ O ₃ is undesirable. As stated above, when the amount of stabilizer decreases, t-phase and m-phase also occur, but when m-phase is generated at room temperature, it is accompanied by volumetric expansion. If the m-phase is generated due to heating or cooling up to several hundred degrees Celsius during film attachment or patterning to the substrate, there is a risk that the substrate will warp or the pattern will shift. Therefore, the lower limit of the stabilizer to produce stabilized zirconia is about 5 mol%. The content of Y ₂ O ₃ is preferably 5 mol % or more and as low as possible, and a more suitable amount is about 5 to about 10 mol %. The crystal grain size of the zirconia phase is preferably 12 μm or less. More preferably, it is 10 μm or less. The crystal grain size of tetragonal zirconia is usually about 15 μm.
However, by setting the thickness to 12 μm or less, machinability can be improved and the size of chipping can be reduced. Further, the relative density (compared to the theoretical density) of the zirconia ceramic of the present invention is desirably 99% or more, and has extremely few pores. Since it has such a high density, it has excellent sliding properties. To produce the zirconia ceramics of the present invention, ZrO ₂ fine powder, Y ₂ O ₃ powder, a, a, a
Group element carbides (e.g. TiC, ZrC, HfC, VC,
NbC, TaC, WC) powder and Al ₂ O ₃ powder are blended in a predetermined ratio, thoroughly mixed, dried, and granulated with a small amount of binder added. This granulated powder is preformed into a compact using a press machine having a cavity of the desired shape. This molded body was heated to 1400 in a vacuum.
A zirconia ceramic is obtained as a sintered body by hot pressing at a temperature of 1600°C to 1600°C. The temperature at which this hot pressing is performed influences the performance of the obtained zirconia ceramics. 1400℃
The above temperature is necessary to increase the relative density of ceramics to 99% or higher. However, if the temperature is 1600°C or higher, the crystal grains of stabilized zirconia will grow significantly, so it is desirable to hot press at 1600°C or lower. Zirconia ceramics obtained by hot pressing are cut with a diamond blade into the required shape according to the application, and then finished with a grinder. Additionally, a magnetic core, signal coil, and insulating film may be attached as necessary. As this insulating film, there are several
Sputtered Al ₂ O ₃ to a thickness of 10 μm is used. As explained above, the zirconia ceramic of the present invention has excellent sliding properties and wear resistance. It is also highly dense and has almost no pores. Furthermore, it has good machinability and can be finely processed. Examples of the zirconia ceramics of the present invention are shown below. Example 1 Fine ZrO ₂ powder and Y ₂ O ₃ powder with an average particle size of 0.03 μm, as well as representative carbides of a, a, and a group transition elements (TiC, ZrC, HfC, VC, NbC, TaC, WC)
Blend the powder and Al ₂ O ₃ powder in the proportions shown in Table 1,
The mixture was mixed for 24 hours in an alumina ball mill using pure water as a solvent. Dry the mixed solution, add 10% PVA solution, granulate it with a sieve machine, and then granulate it at a pressure of 1 ton/cm ^2.
A molded body of 80φ×6 to 7 was preformed. Next, this was hot pressed in a vacuum at 1450° C. x 300 Kg/cm ² x 1 h. The density of the sintered body was measured by an underwater displacement method, and the relative density was determined by dividing the theoretical density. For the bending strength test, the sintered body was cut with a diamond blade and cut into 4mm x 3mm x 35mm pieces.
Measurements were made using a test piece of mm, bent at four JIS points. In addition, pore observation and Bitkers hardness measurement (load 200g)
This was done by mirror polishing a part of the specimen. Specific resistance was measured using a 1 cm square test piece using the Pau method, which is a type of four-terminal method.When the specific resistance was high, silver paste was applied to both sides to determine the insulation resistance. In addition, a wear test was conducted, the amount of wear was measured, and a relative comparison was made when the amount of wear of zirconia was taken as 100. Machinability was evaluated by making grooves on mirror-polished specimens with a diamond blade and comparing the size of chipping that occurred on the wrapping surface and the edge of the cut surface. The sliding properties were compared by cutting out the shape of an actual thin film magnetic head from the sintered body, bringing it into contact with a magnetic disk, and rotating the disk. The above measurement results are
Shown in the table. In Table 1, zirconia ceramics containing Al ₂ O ₃ and carbide are Nos. 1 to 8, and Nos. 9 to 10 are Al ₂ O ₃
This is zirconia ceramics with chisel added. In both cases, 2wt% of Al ₂ O ₃ was added as an auxiliary agent.
In addition, No. 11 added 0.5wt% MgO as an auxiliary agent,
It was hot pressed at 1650℃. The relative density of all materials except Al ₂ O ₃ -TiC is more than 99%, and almost no pores are observed even when observing pores on a mirror surface, and there are no pores on the surface, which is a basic characteristic of a substrate. It was found that the following conditions were met. This seems to be due to the fact that the matrix ZrO ₂ has inherently better sinterability than Al ₂ O ₃ and is sintered under pressure. The Bitkers hardness of ZrO ₂ is smaller than that of Al ₂ O ₃ -TiC, but by adding carbide, Hv can be reduced.
It increases by about 100-200 to 1400-1550. Therefore, the bending strength, which also improves wear resistance, is strongly affected by the strength of the matrix, so No. 7, which has a lot of residual tetragonal crystals,
In comparison, ZrO ₂ and ZrO ₂ -carbide systems have lower strength, but are strong enough to be used as substrate materials. Furthermore, when composited with 30vc1% carbide, there is a large difference in specific resistance depending on the average particle size and distribution state of the carbide particles, but even so, the conductivity is greatly improved compared to the ZrO ₂ matrix, and the charging It has a positive impact in terms of prevention. As for chipping during grooving, adding carbide reduced the amount and size of chipping and improved workability. In the case of Al ₂ O ₃ -TiC, it is not very desirable as a substrate material because it scratches the disk in a short period of time, whereas with stabilized zirconia containing a sufficient amount of Y ₂ O ₃ , the disk rotates for a long time. It has good sliding characteristics.

【table】

[Table] Example 2 Zirconia ceramics having the composition shown in Table 2 were produced under the same manufacturing conditions as in Example 1. This was processed and wrapped to a mirror surface to make a 3" diameter wafer. This sample was measured for crystal diameter, chipping resistance, cutting resistance machinability, texture of the cut surface, and sliding characteristics. The chipping resistance was measured by the size of chipping that occurs at the edge during grooving with a dicer (indicated by the maximum chipping depth in the table) and by the chipping of the alumina film.The alumina film was formed on a ceramic substrate with a thickness of approximately 40 μm. The width of the chip is shown by the width of the chip when the alumina film is chipped along with the substrate when the alumina film is formed with a sputter ring and then grooved with a dicer.Cutting resistance is measured by a peripheral slicer, and the stress applied to the slicer is The sliding properties were determined by a CSS test in which a magnetic disk was rotated and a _zirconia ceramic was slid against _it . In the case of zirconia, the cutting resistance was very large, and the surface condition of the cut surface was not good.The chipping depth was small for No. 12, which has a small crystal grain size, but when the amount of Y ₂ O ₃ was increased, coarse cubic crystals were formed. There were a lot of them, and they got bigger in No.14.
In Nos. 15 and 16, in which TiC and Al ₂ O ₃ were added alone, the crystal grains were refined to some extent, so the chipping depth was reduced to some extent, but the size of the texture of the cut surface was not improved. On the other hand, in the case of No. 13 and No. 17 to 25, which added TiC and Al ₂ O ₃ at the same time, the amount of chipping was reduced to about 1/3 compared to No. 14. The cutting resistance was also small and the texture of the cut surface was reduced. It is in good condition, and even after machining 90 sliders, the cutting surface is almost the same as it was at the beginning. In addition, chips in the alumina film are also very small. No. 25 is a case in which a very large amount of TiC is added at 40 Vol%, but the chipping cutting resistance is small, but the sliding properties are poor. As is clear from the above experiments, zirconia ceramics have excellent sliding properties. However, when carbide is added in excess of 30 Vol%, the sliding properties deteriorate slightly. Still, it is superior to the Al ₂ O ₃ -TiC system. Zirconia ceramics with carbide and alumina dispersed have excellent wear resistance. Even in the case of C-phase zirconia, when Al ₂ O ₃ and TiC are dispersed, the crystal grain size becomes smaller and the amount of chipping becomes smaller. This improves workability.

【table】

Claims (1)

[Scope of Claims] 1. 0.4 to 26.3 wt% of carbide of at least one element selected from groups a, a, and a of the periodic table;
A zirconia ceramic containing 0.34 to 22.5 wt% of alumina, with the remainder consisting essentially of a zirconia portion. 2. The zirconia ceramic according to claim 1, wherein the zirconia portion is substantially cubic zirconia. 3. The zirconia ceramic according to claim 2, wherein the carbide of an element in groups a, a, a of the periodic table is titanium carbide. 4 The zirconia part contains yttrium oxide from 5 to
The zirconia ceramic according to claim 3, wherein the zirconia ceramic contains 20 mol % and the remainder is substantially zirconium oxide. 5. The zirconia ceramic according to claim 4, which is hot-pressed to a density of 99% or more of the theoretical density.