JP2005336034A - Al2o3-based ceramic and its production method as well as substrate for use in magnetic head using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ceramic suitable for a head member, which is excellent in chipping resistance at the time of machining such as slicing or the like, and excellent in surface quality after ion milling or processing with a reactive ion etching method, and which exhibits little decline in thermal conductivity while comprising minute crystals and which can prevent crystal particles from falling off, and a substrate for use in a membrane magnetic head using it as well as its production method. <P>SOLUTION: The Al<SB>2</SB>O<SB>3</SB>-based ceramic comprises Al<SB>2</SB>O<SB>3</SB>of 50-95 wt% and at least one kind selected from among TiC and TiN of 5-50 wt%, and is characterized in that the average crystal particle diameter in the Al<SB>2</SB>O<SB>3</SB>-based ceramic is 0.5-1.2 μm and the smallest crystal particle diameter is 0.2 μm or larger. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention is, ion milling (RIE method) relates Al ₂ O ₃ based ceramics suitable for surface processing by ion irradiation, such as, Al ₂ used and a substrate for a magnetic head, a jig, such as the measurement instrument The present invention relates to a method for producing O ₃ ceramics.

  In recent years, a magnetic recording medium used for a hard disk drive or the like has been rapidly required to have a high density. In order to cope with this higher density, magnetic heads that use magnetic thin films that are suitable for higher density magnetic recording are attracting attention as magnetic heads for recording and reproduction, instead of conventional magnetic heads that use ferrite or the like. Yes. In particular, the attention of MR (Magneto Resistive) heads and GMR (Giant MR) heads using the magnetoresistive effect is increasing.

  Such a recording / reproducing magnetic head floats from the surface of the medium, and its flying height is as small as about 20 nm. For this reason, in Patent Document 1, a difference in the flying height of the magnetic head occurs due to the difference between the inner and outer peripheral speeds of the magnetic disk. Therefore, in order to reduce the difference, only a positive pressure portion is provided at the flying portion. In addition, a magnetic head has been proposed in which a minute groove (concave portion) is formed in a part of the air bearing surface to form a negative pressure portion so that the flying height is constant on the inner and outer circumferences of the magnetic disk.

  Further, there is a demand for a magnetic head material that does not drop off particles due to contact impact between the head and the medium when mounted on a hard disk device, and it is necessary to increase the bonding force between crystals, that is, to improve the sinterability. Yes.

  In order to improve the sinterability, there are methods of raising the firing temperature or adding a sintering aid component, but if the firing temperature is raised, crystal grains grow and it is difficult to obtain fine crystals.

  The addition of a sintering aid has caused a problem that the surface portion after processing is deteriorated due to a difference in processing rate during processing by ion milling or reactive ion etching, and has not yet been fully solved.

  In addition, along with the demand for higher recording density of the hard disk device, the magnetic head slider moves from the transducer as the heat generation during recording / reproduction increases due to the miniaturization of the shape of the transducer that reads and writes magnetic recording. The demand for suppression of temperature rise due to heat conduction has increased, and a thin film magnetic head having high thermal conductivity has become necessary.

In order to produce such a magnetic head, first, slicing processing is performed from the substrate, and the air bearing surface of the cut magnetic head slider is polished, and then a groove for a negative pressure portion is formed on the air bearing surface. Is recessed. The groove for the negative pressure portion has a very shallow depth of about several microns and high processing accuracy is required. Therefore, an ion beam such as Ar, CF ₄ , CCl ₄ , or BCl ₃ is usually used for the processing. A method using ion irradiation such as ion milling method or reactive ion etching method is used.

  Since such a processing method has been conventionally used, such a material for a magnetic head slider is required to have characteristics such as excellent wear resistance and excellent machinability.

  Here, FIG. 1 is a diagram showing an example of a TPC slider in a magnetic head, wherein 1 is a substrate, 2 is a slider floating surface, 3 is a rail, 4 is a groove, and 5 is a step portion.

As one may satisfy these requirements materials, _Al 2 _O 3 -TiC based ceramic containing TiC is frequently used against the _Al 2 _{O 3.} In order to satisfy the above characteristics, this Al ₂ O ₃ —TiC-based ceramic has a mirror finish by adding a sintering aid such as MgO, Y ₂ O ₃ , Yb ₂ O ₃ and making it a completely dense ceramic. The chipping resistance and the machinability during slicing processing have been improved by improving the thickness of the ceramics and growing the crystal grain size of the ceramic to about 1.5 to 3 μm (see Patent Document 1).

It is also known to improve chipping resistance in machining by adding 0.5 to 5 parts by weight of a free-cutting property imparting agent such as MgO, NiO, Cr ₂ O ₃ , or ZrO ₂ (patent) Reference 2).

  Further, the average particle diameter of TiC in the ceramic is 1.0 to 2.5 μm, and TiC having a particle diameter of 0.1 μm is 10% by weight or less, and is resistant to chipping such as slicing processing. What improved the property is known (refer patent document 3).

According to the above methods, the chipping resistance in machining such as slicing is improved, but processing such as ion milling or reactive ion etching method in which ABS rail processing is applied to the air bearing surface of the current magnetic head. in, appears remarkably a step of Al2O3 and TiC and large particle size, also the machinability improving agents, with the generation of projections and holes due to the difference in milling rate of as Al ₂ O ₃ and TiC by the process, There was a problem that it was difficult to obtain satisfactory surface quality.

Therefore, in the Al ₂ O ₃ —TiC ceramics, the applicant of the present application previously has an average crystal grain size of Al ₂ O ₃ of 5 to 50% larger than that of TiC, and further the average crystal grain size of the entire crystal is 1 μm or less. Further, a ceramic having an average crystal grain size of TiC of 0.9 μm or less and a grain boundary layer content of crystal grains of 1.0% by weight or less has been proposed (see Patent Document 4).

According to this, the quality of the processed surface is improved by processing such as ion milling and reactive ion etching.
Japanese Patent Laid-Open No. 2-153860 JP-A-57-135773 JP-A-9-315848 JP-A-7-242463

However, by increasing the crystal grain size to improve processability, preventing particle dropout and improving thermal conductivity, or adding a sintering aid to improve processability and prevent particle dropout, Although there is a problem that the surface part deteriorates during processing by milling or reactive ion etching, the purity of Al ₂ O ₃ ceramics is improved in order to improve the quality of the surface part during processing by ion milling or reactive ion etching. There is a problem that chipping occurs at the time of slicing processing due to deterioration in thermal conductivity or by making the fine particle size finer, and the problem has been a conflicting problem.

Usually, when obtaining Al ₂ O ₃ ceramics that do not contain fine crystal grain size, some control is achieved by selecting the grain size of the raw material or adjusting the temperature during sintering to grow the grain. But still could not be completely removed.

Therefore, the present invention has good chipping resistance at the time of machining such as slicing processing, excellent surface quality after processing by ion ion milling or reactive ion etching method, and thermal conductivity while having fine crystals. An object of the present invention is to provide an Al ₂ O ₃ -based ceramic suitable for a head member that is less likely to drop and does not drop crystal grains, a method for manufacturing the same, and a magnetic head substrate using the same.

The present inventors have conducted extensive studies results, Al and ₂ O _3, and controlling the crystal grain size in the Al ₂ O ₃ based ceramics containing at least one selected from TiC and TiN, does not contain crystal grains of very small size Ceramics can relieve internal stresses inside the ceramics and improve toughness against fracture. Chipping resistance during slicing processing, prevention of particle dropout of magnetic head, processing by ion ion milling and reactive ion etching methods The quality of the surface portion at the time was improved, and it was found that there was little decrease in thermal conductivity while having fine crystals, and the present invention was achieved. That is, the ceramic of the present invention is an Al ₂ O ₃ ceramic containing 50 to 95% by weight of Al ₂ O ₃ and 5 to 50% by weight of at least one selected from TiC and TiN. The average crystal grain size is 0.5 to 1.2 μm and the minimum crystal grain size is 0.2 μm or more.

  Furthermore, according to the present invention, the ceramic is characterized in that a raw material slurry is obtained using an ultrafiltration method.

Further, the magnetic head substrate is made of Al ₂ O ₃ ceramics.

The ceramic of the present invention is a ceramic containing 50 to 95% by weight of Al ₂ O ₃ and 5 to 50% by weight of at least one selected from TiC and TiN, and the average crystal grain size in the ceramic is 0.00. 5 to 1.2 μm and the crystal grain size is 0.2 μm or more, the chipping resistance is good at the time of processing, particularly at the time of mechanical processing such as slicing processing, and after processing by ion ion milling or reactive ion etching method. While having excellent surface quality, there is little decrease in thermal conductivity while having fine crystals, and ceramics suitable for a head member that does not drop crystal grains can be obtained.

  Furthermore, according to the present invention, since the ceramic is obtained using an ultrafiltration method, the ultrafiltration is used at the stage of the raw material slurry before sintering to completely remove the fine particles. Therefore, there is no need to adjust the selection and the sintering temperature, and a ceramic containing no fine crystals can be easily obtained.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a view showing an example of a TPC slider in a magnetic head. 1 is a substrate, 2 is a slider floating surface, 3 is a rail, 4 is a groove, and 5 is a step portion.

Ceramic of the present invention, the _Al 2 _{O 3} 50 to 95 wt%, a _Al 2 _{O 3} based ceramic at least one kind of containing 5 to 50 wt% selected from TiC and TiN, _Al 2 _{O 3} system With an average crystal grain size of 0.5 to 1.2 μm and a crystal grain size of 0.2 μm or more in ceramics, chipping resistance during machining such as slicing is good, and ion ion milling and reactive ions Ceramics suitable for a head member that has excellent surface quality after processing by an etching method, has a small crystal and has little decrease in thermal conductivity, and does not drop crystal grains, and a substrate for a thin film magnetic head using the same, In addition, a manufacturing method thereof can be provided.

  The reason why each component is limited to the above range is that when at least one selected from TiC and TiN is less than 5% by weight, chipping resistance decreases and the volume resistivity value becomes an insulator, and 50% by weight. Exceeding sinterability decreases, chipping increases, speed during processing by ion ion milling and reactive ion etching decreases, and it becomes uneconomical, and more contacts with the media increase. This is because the sliding characteristics of the magnetic head slider deteriorate.

  For the measurement of the content, the elements contained in the ceramics are specified by fluorescent X-ray analysis, the crystal phase is identified by X-ray diffraction to confirm that the crystal phases of aluminum oxide and titanium carbide exist, and further, the fluorescent X Elemental analysis was performed by line analysis, and aluminum and titanium were converted into oxides and carbides, respectively.

The ceramic having the above composition is composed of Al ₂ O ₃ crystal grains and at least one kind of crystal grains selected from TiC and TiN in terms of composition. When a sintering aid component is included, ion ion milling or At the time of processing by the reactive ion etching method, there is a possibility that protrusions and holes are formed in a stepped shape due to a difference in processing rate, and the sliding characteristics are deteriorated. Therefore, in the present invention, a sintering aid may be included, but the content is preferably as small as 0.05 to 0.5 parts by weight. In addition, if the sintering aid component is less than 0.05 parts by weight, the sinterability is poor, and if it exceeds 0.5 parts by weight, the sinterability is improved, but by ion ion milling or reactive ion etching. Surface quality after processing deteriorates and sliding characteristics deteriorate. As the sintering aid, MgO, CaO, Y ₂ O ₃ , Yb ₂ O ₃ , Nb ₂ O ₅ or the like may be used.

  In addition, the average crystal grain size of ceramics crystals is limited because if the average crystal grain size is smaller than 0.5 μm, the processing load increases due to slicing and the addition of sintering aid components is extremely small. Chipping resistance decreases, and conversely, if it is larger than 1.2 μm, slicing processability is improved and chipping resistance is excellent. However, as described above, surface quality is improved by processing by ion ion milling or reactive ion etching. This is because the flying height of the thin film magnetic head is greatly affected, and the flying height of the thin film magnetic head is not stable, and the head characteristics are not stable. If the average crystal grain size is 0.5 to 1.2 μm, suitable processed surface quality can be obtained, and the head characteristics can be stabilized.

  In addition, when the crystal grain size of 0.2 μm or less is included in the ceramic crystal, slicing workability is deteriorated, chipping is increased, and the processed surface is roughened. Therefore, when the head receives an impact, the processed surface is rough, so that the crystal particles are likely to fall off.

  The measurement of the average crystal grain size is a value obtained by taking a photograph with a metal microscope and adopting the code method from the photograph.

  Further, if the crystal grain size of 0.2 μm or less is included in the ceramic crystal, the thermal conductivity tends to decrease due to the increase of crystal grain boundaries, and the temperature increase during recording / reproduction is caused by miniaturization of the transducer shape. There is a problem that it becomes impossible to respond to suppression.

  The fine particle diameter preferably does not include 0.2 μm or less from the viewpoint of characteristics such as slicing processability and thermal conductivity, and desirably does not include 0.1 μm or less from the viewpoint of yield.

  Furthermore, according to the present invention, the ceramics are obtained by using an ultrafiltration method, so that it is not necessary to select raw materials and adjust the sintering temperature, and ceramics containing no fine crystals can be easily obtained.

  In addition, the measurement of the crystal grain size in which the minimum crystal grain size is 0.2 μm or more was taken with a transmission electron microscope (TEM), and it was confirmed whether or not there was a crystal of 0.2 μm or less in the crystal photograph. Is.

  In ultrafiltration, a non-target membrane consisting of a skin layer and a sponge layer, called an ultrafiltration membrane, is used to permeate water, ionic molecules, and low molecular weight materials without permeating high molecular weight materials. Excellent in sex. Usually, separation by a membrane for a high molecular weight substance having a molecular weight of about 1,000 to 300,000 is called ultrafiltration (UF), but this time, using this ultrafiltration membrane, a ceramic slurry is used. The fine particles having a size of 0.2 μm or less contained therein are removed.

  This is because the fine particles are completely removed by using ultrafiltration at the stage of the raw material slurry before sintering.

The ceramics of the present invention includes an Al ₂ O ₃ powder, at least one powder selected from TiC and TiN, and a predetermined sintering aid added at a predetermined ratio as described above, and then a ball mill or the like. After mixing by an arbitrary method, the finely pulverized particle region is cut using an ultrafiltration device, the slurry is dried and then molded, and the molded body is 1500-1750 ° C., Al ₂ O ₃ and TiC. When the weight ratio of at least one selected from TiN is approximately 7: 3 and the average grain size of the primary particles after ball mill mixing is 1.0 μm, it is preferably a hot press method in a temperature range of 1700 to 1730 ° C. May be fired. It can also be sintered by hot isostatic firing (HIP method) or the like.

As described above, in order to control Al ₂ O ₃ crystal grains and at least one kind of crystal grains selected from TiC and TiN, all of them have a small particle size as a starting material, preferably Al ₂ O ₃ has an average particle size of 0.3-1.0 micrometer and TiC and TiN use 0.3-1.5 micrometer. In addition, it is desirable to use a raw material with a uniform particle size and uniform shape, and to set the firing temperature as low as possible in order to prevent grain growth.

(Experimental example 1)
An Al ₂ O ₃ raw material (purity of 99.9% or more) having an average particle diameter of 0.3 μm and a TiC raw material (purity of 99.5% or more) having an average particle diameter of 1.0 μm were used, and these were used as ceramic compositions. ₂ O ₃ , TiC, and sintering aid were weighed so as to have the ratios shown in Table 1, respectively, and methanol was used as a solvent, and 80% by weight was added to the raw material solids, and a vibration mill was used. The mixture was pulverized and mixed for 120 hours. The average particle diameter of the obtained raw material slurry was 0.4 μm.

  After adding methanol to the slurry thus obtained and diluting it four times, filtration was performed using an ultrafiltration apparatus as shown in FIG. In the figure, the slurry 20 to be subjected to ultrafiltration is stirred in a stirring tank 21 using a stirrer 22, and sent to an ultrafiltration membrane device 24 using a liquid feed pump 23 for filtration to remove the fine particle-containing slurry 25. . As a result, the slurry subjected to ultrafiltration is concentrated because methanol containing fine particles is removed. In this way, concentration was carried out using an ultrafiltration device under the condition that the ceramics did not contain a crystal grain size of 0.2 μm or less until it returned to the volume before dilution, that is, ultrafiltration was performed.

FIG. 6 shows the particle size distribution measurement results of the slurry before and after ultrafiltration in the case of the composition of 70% Al ₂ O _{3 and} 30% TiC.

  It can be seen that the particle size distribution of the raw slurry subjected to ultrafiltration is shifted to the coarse particle side, and the fine particles are cut. Since the opening of the filtration membrane of the ultrafiltration device varies depending on the ratio of the composition and the properties of the slurry, it can be selected while looking at various conditions.

Next, the slurry of the part which does not contain the fine particles in the previous period was dried to obtain a forming raw material. Next, it was molded into a desired shape and subjected to hot press firing at 1700 ° C. and a pressure of 250 kg / cm ₂ for 1 hour.

  The surface of the obtained ceramic was mirror-finished, the average crystal grain size, confirmation of the presence or absence of a crystal grain size of 0.2 μm or less, and K1c, thermal conductivity, and internal stress were measured as fracture toughness values. The average crystal grain size was measured by taking a photograph with a metal microscope at a magnification of 2,000 and employing the code method from the photograph.

  In addition, to confirm the presence or absence of a crystal grain size of 0.2 μm or less, a 20,000-fold photograph was taken with a transmission electron microscope (TEM), and it was confirmed whether or not a crystal of 0.2 μm or less was present in the crystal photograph. It was done by doing. The occupancy ratio of the crystal of 0.2 μm or less was obtained from the transmission electron micrograph with an image analyzer (Luzex-FS). The K1c was measured by the Indentation Fracture method (IF method) with a load of 98.065N. The thermal conductivity was determined by a laser flash method. About the measurement of internal stress, it evaluated by measuring the deformation amount of the block 11 shown to FIG. 2 (a) (b) by the procedure of following (1)-(4).

(1) The magnetic head substrate is cut by 11a, and the cut surface is mirror-finished as the measurement surface 11a.

(2) Measure the flatness of the measurement surface 11a with a surface roughness meter and measure a distance of A = 72 mm.

(3) The magnetic head substrate is cut at 11b parallel to the measurement surface 11a, and the parallel surface 11b is mirror-finished. The distance B between the parallel surface 11b and the measurement surface 11a was 13 mm.

(4) The flatness of the measurement surface 11a is again measured 72 mm with a surface roughness meter.

  In addition, this evaluation method is a method in which stress calculation is omitted from the method described in JP-A-1999-92213 and only the amount of deformation is studied. That is, it can be determined that the smaller the amount of deformation before and after the cutting of the block 11, the smaller the internal stress remaining on the magnetic head substrate. The deformation amount was measured using Talysurf series 2 manufactured by Taylor Hobson.

  For chipping resistance, the sample was cut into a 3 x 4 x 30 mm rectangle, polished with a tin plate etc. until the surface became a mirror surface, and then diamond foil (resin # 325, φ110 mm x 1 mmt) was rotated. It set to 5,500 rpm and feed 40mm / min, the rectangular body was cut | disconnected using this, and the evaluation of chipping was obtained from the cut surface. As an evaluation standard, the length of the portion removed by chipping from the interface through which the diamond foil passed was measured. Select an arbitrary 500 μm at the interface through which the diamond foil has passed, select 5 points with the maximum chipping width and the largest chipping width below it, and use the average chipping width of the 5 points as the evaluation criterion, and the average chipping width is large It was determined that the chipping resistance was poor. Evaluation criteria are as shown in Table 1.

  For the machinability, the ceramics were polished into a disk shape of φ76 mm and thickness φ4 mm, and then diamond foil (resin # 325, φ110 mm × 1 mmt) was set at a rotational speed of 5,500 rpm and a feed of 100 mm / min. When the disk was cut, the load current of the rotary drive motor connected to the main shaft of the diamond foil was measured, and the average current value during steady cutting was obtained. When this average current value is increased, the cutting resistance is increased, and accordingly, the machinability is lowered. The evaluation standard is divided into three stages of ○ mark, Δ mark, and X mark, and sequentially. Represents a decrease in machinability. Similarly, the results of the samples that were not subjected to ultrafiltration are also shown in Table 1 as 7 · 8 · 9.

  As is clear from Table 1, sample No1 has a large K1c, but the average crystal grain size is small, so the machinability is degraded. Further, since the internal stress is large, chipping resistance is poor. Sample No. 5 has low K1c and poor chipping resistance. Samples Nos. 2 to 4 do not contain fine particles of 0.2 μm or less by ultrafiltration, so the thermal conductivity is 18 to 23 W / m · k, and 15 to 17 W / m · k of Comparative Sample Nos. 7 to 9 It can be seen that the comparison is improved. Furthermore, also about internal stress, it turns out that sample No. 2-4 is improving compared with 2.1-2.8 MPa of 0.7-1.5 MPa and sample No. 7-9 for a comparison. Regarding the chipping resistance, X for sample No2 for comparison, Δ for sample No7 for comparison, Δ for sample No3, △ for sample No8 for comparison, and Δ for sample No4 for ◯ for sample No2. It can be seen that there is an improvement trend in all the samples.

Regarding the machinability, the comparison of sample No7 for the sample No2 and the comparison for the sample No7 for the sample No3, the comparison for the sample No8 for the comparison No. As a result of the evaluation, it can be seen that all the samples are equal to or higher than those of the samples. Regarding the difference between chipping resistance and machinability, it is considered that even if the average crystal grain size is almost the same, if fine particles are included, a load is applied during processing and chipping is likely to occur. FIG. 3 shows a transmission electron micrograph (magnification × 20,000) of sample No. 3 in the present invention, and FIG. 4 shows a transmission electron micrograph (magnification × 20,000) of sample No. 8 of a comparative example. As shown, FIG. 3 of the present invention does not include a crystal grain size of 0.2 μm or less. This seems to be related to the internal stress, and the samples No. 2 to 4 in which the fine particle region is cut generally have excellent chipping resistance and machinability, and the value of the internal stress is small.

(Experimental example 2)
An Al ₂ O ₃ raw material (purity 99.9% or more) having an average particle diameter of 0.3 μm and a TiN raw material (purity 99.5% or more) having an average particle diameter of 1.2 μm were used, and these were used as ceramic compositions as Al. ₂ O ₃ , TiN, and sintering aid are weighed so as to have the ratios shown in Table 2, respectively. Using methanol as a solvent, 80 wt% is added to the raw material solids, and using a vibration mill. The mixture was pulverized and mixed for 120 hours. The average particle diameter of the obtained raw material slurry was 0.5 μm.

After adding methanol to the slurry thus obtained and diluting it 4 times, using an ultrafiltration device, the ceramic is concentrated until it returns to the volume before dilution under the condition that does not contain a crystal grain size of 0.2 μm or less, That is, ultrafiltration was performed. Then, the slurry of the part which does not contain a fine particle in the previous period was dried and the raw material for shaping | molding was obtained. Next, it was molded into a desired shape and subjected to hot press firing at 1650 ° C. and a pressure of 250 kg / cm ² for 1 hour.

  As in the case of Experimental Example 1, the obtained ceramics were confirmed to have an average crystal grain size, a crystal grain size of 0.2 μm or less, measurement of K1c as a fracture toughness value, measurement of thermal conductivity, internal stress Evaluation, chipping resistance, and machinability were evaluated. The results are shown in Table 2.

  As is clear from Table 2, sample No. 10 has a large K1c, but the machinability is low because the average crystal grain size is small.

  Further, since the internal stress is large, chipping resistance is poor. Sample No. 14 has low K1c and poor chipping resistance. Since sample Nos. 11-13 do not contain fine particles of 0.2 μm or less by ultrafiltration, the thermal conductivity is 23-28 W / m · k and 20-22 W / m · k of sample Nos. 15-17 for comparison. It can be seen that the comparison is improved.

  Furthermore, also about internal stress, it turns out that sample No. 11-13 has improved compared with 2.4-3.6 MPa of sample No. 15-17 for comparison, and 1.6-2.6 MPa.

  Regarding the chipping resistance, X for sample No11 for comparison, Δ for sample No15 for comparison, Δ for sample No12, Δ for comparison sample No16, Δ for sample No13, × for sample No17 for comparison It can be seen that there is an improvement trend in all the samples.

  As for the machinability, the sample No11 of ○ for comparison, the sample No15 for comparison, the sample No12 of ○, the comparison of sample No16 of Δ, the sample of No13 of ◯ of ○ for comparison. It can be seen that all the samples have the same or better or improved tendency.

Regarding the difference between chipping resistance and machinability, it is considered that even if the average crystal grain size is almost the same, if fine particles are included, a load is applied during processing and chipping is likely to occur. This seems to be related to the internal stress, and Samples Nos. 11 to 13 in which the fine particle region is cut are generally excellent in chipping resistance and machinability and have a small internal stress value.

(Experimental example 3)
Al ₂ O ₃ raw material having an average particle diameter of 0.3 μm (purity 99.9% or more), TiC raw material having an average particle diameter of 1.0 μm (purity 99.5% or more), TiN raw material having an average particle diameter of 1.2 μm ( These were weighed so that the composition of ceramic was Al ₂ O ₃ , TiN, and sintering aid in the proportions shown in Table 3, and methanol was used as the solvent. 80% by weight based on the solid content of the raw material was added, and pulverized and mixed for 120 hours using a vibration mill. The average particle diameter of the obtained raw material slurry was 0.5 μm.

After adding methanol to the slurry thus obtained and diluting it 4 times, using an ultrafiltration device, the ceramic is concentrated until it returns to the volume before dilution under the condition that does not contain a crystal grain size of 0.2 μm or less, That is, ultrafiltration was performed. Then, the slurry of the part which does not contain a fine particle in the previous period was dried and the raw material for shaping | molding was obtained. Next, it was molded into a desired shape and subjected to hot press firing at 1675 ° C. and a pressure of 250 kg / cm ² for 1 hour.

  As in the case of Experimental Example 1, for the obtained ceramics, the average crystal grain size, confirmation of the presence or absence of a crystal grain size of 0.2 μm or less, measurement of K1c as a fracture toughness value, measurement of thermal conductivity, internal stress Evaluation, chipping resistance, and machinability were evaluated. The results are shown in Table 3.

  As is apparent from Table 3, sample No. 18 has a large K1c, but the machinability is degraded because the average crystal grain size is small.

  Further, since the internal stress is large, chipping resistance is poor. Sample No. 22 has low K1c and poor chipping resistance. Samples Nos. 19 to 21 do not contain fine particles of 0.2 μm or less by ultrafiltration, so the thermal conductivity is 21 to 25 W / m · k and 18 to 20 W / m · k of the comparative sample Nos. 23 to 25. It can be seen that the comparison is improved.

  Furthermore, also about internal stress, it turns out that sample No. 19-21 is improved compared with 2.4-3.2 MPa of sample No. 23-25 for comparison, and 1.2-2.1 MPa.

  Regarding the chipping resistance, the comparison of sample No. 23 for comparison No. Δ for comparison No. 23, comparison for sample No 20 ◎ for comparison No. 24 for comparison sample No. It can be seen that there is an improvement trend in all the samples and evaluation.

  Regarding the machinability, the comparison of sample No. 23 was compared with the comparison of sample No. 23, the comparison of sample No. 20 was compared with the comparison of sample No. 24, and the comparison of sample No. 21 was. It can be seen that all the samples have the same or better or improved tendency.

Regarding the difference between chipping resistance and machinability, it is considered that even if the average crystal grain size is almost the same, if fine particles are included, a load is applied during processing and chipping is likely to occur. This seems to be related to the internal stress, and sample Nos. 19 to 21 in which the fine particle region is cut are generally excellent in chipping resistance and machinability, and the value of the internal stress is also small.

It is a figure which shows an example of the TPC slider in a magnetic head. It is a figure which shows the evaluation method of the internal stress (deformation amount) of the board | substrate for magnetic heads. It is a photograph which shows an example of the crystal | crystallization photograph of the Example in this invention. It is a photograph which shows an example of the crystal | crystallization photograph of the comparative example in this invention. It is a figure which shows an example of the ultrafiltration apparatus in this invention. It is a figure which shows the difference of the particle size distribution of the slurry before and behind ultrafiltration.

Explanation of symbols

1: Substrate 2: Slider floating surface 3: Rail 4: Groove 5: Step part 10: Magnetic head substrate 11: Block 11a: Measurement surface 11b: Parallel surface 20: Slurry 21: Stirring tank 22: Stirrer 23: Liquid feed pump 24: ultrafiltration membrane device 25: the fine particle containing slurry _{Al 2 O 3: Al 2 O} 3 crystal TiC: TiC crystal Al: _Al 2 _{O 3} crystal Ti: TiC crystal

Claims (3)

Al ₂ O ₃ ceramics containing 50 to 95% by weight of Al ₂ O ₃ and 5 to 50% by weight of at least one selected from TiC and TiN. An Al ₂ O ₃ based ceramic characterized by having a minimum crystal grain size of 0.2 μm or more and a thickness of 5 to 1.2 μm. Ceramics according to claim 1, the production method of Al ₂ O ₃ based ceramics, characterized in that the raw material slurry obtained by ultrafiltration. A magnetic head substrate comprising the Al ₂ O ₃ ceramic according to claim 1.

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