JP2005272291A - Aluminum oxide titanium nitride sintered body, magnetic head substrate, ultrasonic motor, hydrodynamic bearing using the same, and manufacturing method thereof - Google Patents

Abstract

A sintered body having excellent resistance to electrostatic breakdown and having a small variation in volume resistivity is provided.
An average of the total crystal grain size of both aluminum oxide crystal grains and titanium nitride crystal grains is 0.4 based on 65 to 85% by mass of aluminum oxide and the balance of titanium nitride. The average crystal grain size of the aluminum oxide is 0.5 to 2.2 μm, and the average crystal grain size of the titanium nitride is 0.2 to 1.6 μm.
[Selection] Figure 1

Description

  The present invention relates to an aluminum oxide titanium nitride-based sintered body and a manufacturing method thereof, and further to a magnetic head substrate, an ultrasonic motor, and a hydrodynamic bearing for a hard disk drive (hereinafter referred to as HDD) using the same.

  Conventionally, composite ceramics combining aluminum oxide with various metal / nonmetal carbides and nitrides have been proposed. For example, a combination of aluminum oxide and titanium carbide, or a combination of aluminum oxide and titanium nitride has a high hardness, so it has been used as an anti-static member because it is used for wear-resistant members and sliding members, and also has conductivity. .

  As a specific application thereof, for example, there is a magnetic head substrate 50 of an HDD shown in FIG. The magnetic head substrate 50 of the HDD is made of a composite ceramic mainly composed of aluminum oxide and titanium carbide or aluminum oxide and titanium nitride, and a plurality of magnetic heads are formed on the surface of the magnetic head substrate 50 through a plurality of film forming steps. After the element 51 is formed, the magnetic head 52 shown in FIG. Since the magnetic head substrate 50 forms the magnetic head slider 20 in the magnetic head 52 and slides on a recording disk (not shown), the magnetic head substrate 50 is required to have high wear resistance. The conductivity is necessary to prevent electrostatic breakdown of the element 51. Furthermore, since the flying height of the magnetic head slider 20 from the recording disk is currently several nanometers, it is also important that the flying surface 20a can be processed with high accuracy by ion milling or the like.

  As another application, it has been used for a pressing member of an ultrasonic motor, a contact surface of a movable member, and the like. Ultrasonic motors are friction-driven motors that use the vibration of piezoelectric elements as the drive source. Unlike general magnetic drive motors, high-resolution positioning that is not affected by magnetism is possible. It has features such as large size, and is used in a lens zoom mechanism of a camera, a medical magnetic resonance diagnostic imaging apparatus, and the like. Since the ultrasonic motor is friction driven, ceramics having excellent wear resistance and heat resistance have been used as a material used for a pressing member that transmits driving force and a contact surface.

  Here, FIGS. 6A and 6B show an example of an ultrasonic motor. As shown in (a), the ultrasonic motor 60 has an electrode film 60b divided into four on one main surface of the piezoelectric ceramic plate 60c, and is connected diagonally and is the other main surface (b ) Is formed as a vibrating body 60e by forming the electrode film 60d over the entire surface, and by applying voltages having different phases to the electrode films 60b and 60d, longitudinal vibration and lateral vibration are applied to the piezoelectric ceramic plate 60c. This is a mechanism in which the pressing member 60a is elliptically moved by synthesizing these vibrations. The movable member can be moved by transmitting the elliptical motion of the pressing member 60a to the contact surface of the movable member.

  FIG. 7 shows a conceptual diagram of a guide device 70 using the ultrasonic motor 60. The guide device 70 has a structure in which a stage 72 is installed on a guide member 71 and the ultrasonic motor 60 is disposed on a side surface of the stage 72a. The ultrasonic motor 60 transmits driving force from the pressing member 60a to the contact surface 72a to move the stage 72 to the left and right.

  As composite ceramics containing aluminum oxide and titanium nitride, there are those shown in Patent Documents 1 to 4. Further, as a magnetic head substrate material that has been conventionally used, there is a material as shown in Patent Document 5 or 6. Furthermore, there exist some as shown in patent document 7 as composite ceramics used for the press part of an ultrasonic motor.

In Patent Document 1, the matrix mainly composed of aluminum oxide contains one or more conductive compounds selected from nitrides and carbides of Ti, Zr, Hf, Nb, or Ta, and has a surface resistivity. There is shown a ceramic for charge removal characterized by being in the range of 10 ⁶ to 10 ¹⁰ Ω · cm ² .

  Further, the conductive compound is characterized in that it is 4 to 23% by volume, the balance is substantially aluminum oxide, and the average particle size is 5 μm or less. In the industrial application field, it has been proposed as a ceramic for electrification removal of electronic parts for preventing breakdown due to rapid discharge when handling charged electronic parts.

In Patent Document _2, Al 2 O 3 -10 mol% _MgO, Al _{2 O} 3 10 _mol% SiO 2, MgO-2.5 _{mol% Nb 2 O 5, Al 2} O 3 -5 mol% _Nb 2 _{O 5} In addition, one or two of SiC, ZrC, TaC, TiC, NbC, or TiN is added to any one of the composite sintered body of Al ₂ O ₃ -10 mol% TiO ₂ or the oxide of Nb ₂ O _5. A magnetic head slider characterized by including two or more is shown.

  This magnetic head slider has been shown to be effective in suppressing wear of carbon or a protective film mainly containing carbon of the magnetic disk. That is, since wear of carbon or a protective film mainly containing carbon is caused by oxidation of the carbon, it is proposed to form a magnetic head slider using a material having a small catalytic action that promotes oxidation of the carbon. -ing

In Patent Document 3, the main component is composed of Al ₂ O ₃ , TiO ₂ or Y ₂ O _{3, and} stabilized ZrO ₂ , and Er is contained in the main component in an amount of 2 to 10% by weight in terms of Er ₂ O _3. A head manufacturing substrate is shown. Furthermore, there is shown a thin film magnetic head manufacturing substrate characterized in that the main component contains at least one selected from SiC, ZrC, NbC, TaC, TiC or TiN in a range of 40% by weight or less. Yes. In this thin film magnetic head manufacturing substrate, the reason is not clear by adding Er ₂ O ₃ in the range of 2 to 10% by weight as the main component. In addition to the effect of suppressing the wear of the protective film mainly containing, it has been shown that chipping when machined and voids when surface polishing is reduced.

In Patent Document 4, _Al 2 _{O 3} and _Al 2 _{O 3} based ceramics 5-70 parts by weight of a plain or _Al 2 _{O 3} containing not less than 95 wt%, _ZrB 2, ZrC as a conductive material, ZrN, _TaB 2, A conductive ceramic obtained by sintering a composition obtained by mixing 30 to 95 parts by mass of at least one of TaC, TaN, TiB ₂ , TiC, and TiN (is it possible to differentiate in claim 6)? Has been.

  Further, since the conductive ceramic has a positive resistance temperature characteristic, when it is energized and heated, it has a feature that it does not cause fusing due to current runaway, and is shown to be suitable for a heater or an electric igniter. Yes.

  In Patent Document 5, 60 to 80% by weight of aluminum oxide and 20 to 40% by weight of titanium carbide are the main constituent parts, and the main constituent parts include zirconium oxide, magnesium oxide, yttrium oxide, and calcium oxide. A ceramic sintered body characterized by the above is shown (hereinafter referred to as Altic).

  This ceramic sintered body is shown to be a substrate for a magnetic head that has improved chipping resistance during slicing and reduced cutting resistance during machining.

Patent Document 6 discloses a magnetic head substrate made of a sintered body having a silicon carbide of 99% by weight or more, a free carbon content of 0.3% by weight or less, and a relative density of 99% or more. The magnetic head substrate has a thermal conductivity of 100 W / m · K or more, a Young's modulus of 400 GPa or more, an average crystal particle diameter of 10.0 μm or less, and a volume resistivity of 10 ⁶ to 10 ⁹ Ω · cm. It is also shown that there is. This silicon carbide magnetic head substrate has been shown to improve heat dissipation while maintaining the same mechanical strength and milling performance as the Altic magnetic head substrate disclosed in Patent Document 5.

  In Patent Document 7, in an ultrasonic motor including a vibrating body and a pressing member that transmits vibration of the vibrating body to the movable member side, the pressing member is formed of a composite material of aluminum oxide and titanium carbide. An ultrasonic motor is shown.

It is shown that by forming the pressing member with this composite material, wear of the pressing member is suppressed and the contact state is stabilized. In addition, titanium carbide reacts with oxygen in the atmosphere due to frictional heat during sliding to become titanium oxide with a higher coefficient of friction than aluminum oxide or titanium carbide, reducing sliding between the pressing member and the movable member, driving It has been shown that power can be transmitted without loss.
JP-A-4-230904 JP-A-5-2730 JP-A-6-28632 JP 59-78973 A JP-A 1-219059 JP 2001-56919 JP2003-18870

  However, the ceramic for electrification removal of electronic parts disclosed in Patent Document 1 has an average crystal grain size of 5 μm or less, and a relatively large crystal grain size is included in the scope of claims as a substrate material for a magnetic head. Therefore, there was a problem described below.

  First, the HDD magnetic head slider cut out from the magnetic head substrate uses a laser with a spot diameter of about 4 to 6 μm when measuring the flying height from the magnetic disk (see FIG. 2). When the crystal grain size was 5 μm or more, there was a problem that the refraction, reflection, and angle of the irradiated laser differed for each place (crystal), and accurate measurement was impossible (see FIG. 3).

  Here, FIG. 2 shows a schematic view of a state in which the flying height of the magnetic head slider is measured. The magnetic head slider 20 is placed on a rotating transparent glass or sapphire disk 21 corresponding to a magnetic disk. In this state, the laser beam floats and the incident laser 22 is irradiated onto the floating surface 20a of the magnetic head slider 20 from below, and the reflection laser 23 is incident on the measurement unit 24.

  FIG. 3 shows an enlarged schematic view of the vicinity of the laser irradiation portion on the air bearing surface 20a of the magnetic head slider 20. If the crystal grain size of the magnetic head slider is too large, the crystal phase 11 depends on where the laser spot 30 is irradiated. It can be inferred that the refraction, reflection, and angle of the crystal phase 12 and the boundary between the crystal phase 11 and the crystal phase 12 change.

  Second, the magnetic head slider has a function of adjusting the flying height by forming a groove 53b or the like on the air bearing surface 53a by ion milling or the like. However, since the processing rate of ion milling differs for each crystal type, the average crystal When the grain size is large, there is a problem that the step of adjacent crystal grains reduces the shape accuracy of the air bearing surface 53a, and the flying characteristics are not stable. Specifically, the step such as the groove 53b of the air bearing surface 53a formed on the current magnetic head slider is usually about 0.1 to several μm, and the processing variation is suppressed when the average crystal grain size is 5 μm or more. It was difficult.

  Here, FIGS. 4A and 4B are conceptual diagrams showing the relationship between the crystal phase, crystal grain size, and processing rate on the surface of the magnetic head slider 20.

  In FIG. 4A, since the crystal grain size is large, the processing rate difference A is a large dent in a wide range, but FIG. 4B shows the processing rate difference A because the crystal grain size is small even in the same composition. It can be seen that the entire surface is uniformly dispersed and the air bearing surface 20a can be processed with high accuracy.

Furthermore, when used as a substrate material for a magnetic head, the sheet resistivity is in the range of 10 ⁶ to 10 ¹⁰ Ω · cm ² , so that the surface resistance of aluminum oxide titanium carbide, which is currently mainstream as a substrate material for a magnetic head, is used. There was also a problem that the conductivity was inferior compared with the rate (10 ⁻¹ Ω · cm ² or less).

  The magnetic head slider material disclosed in Patent Document 2 is a material obtained by adding carbide or nitride to a composite sintered body of oxide ceramics. This material is described in the specification of Patent Document 2 that a double oxide is generated between two kinds of oxides, and it can be assumed that this is a glass layer. However, if the oxide crystal phase, glass phase, carbide crystal phase or nitride crystal phase are mixed, the processing rate of ion milling differs as described above, and when used for a magnetic head slider, the groove on the air bearing surface, etc. There is a problem that it is difficult to form the film with high accuracy. That is, since this material has at least three crystal phases (including a glass phase), at least three steps are generated on the air bearing surface under one milling condition, and the processing accuracy is lowered.

  In addition, such a glass phase is usually subject to wear and corrosion, which lowers the durability of the magnetic head slider. Further, the abrasion powder generated from the glass phase reduces the cleanliness in the magnetic disk device. was there.

  In Patent Document 3, an oxide-carbide-based, oxide-nitride-based magnetic head manufacturing substrate with good machinability is shown, but erbium oxide contains 2 to 10% by weight. The problems described in Patent Document 1 and Patent Document 2 have not been overcome.

  Patent Document 4 discloses a conductive ceramic containing aluminum oxide containing at least 95% by mass of aluminum oxide or aluminum oxide and at least one of various borides, carbides and nitrides. Since this material was not devised as a substrate material for a magnetic head, the problem relating to the crystal grain size described in Patent Document 1 has not been solved.

  That is, in Example 10 of Patent Document 4, an aluminum oxide having an average particle diameter of 0.5 μm and a titanium nitride having an average particle diameter of 2 μm were prepared, hot pressed, and an aluminum oxide-titanium nitride composite material. However, it can be easily estimated that the average particle size of titanium nitride becomes 2 μm or more after hot pressing, and it is clear that it is not suitable for a magnetic head substrate.

  In addition, when using aluminum oxide containing 95% by mass or more of aluminum oxide, the sintering aid forms a glass phase, so that the durability of the magnetic head slider described in Patent Document 2 and wear powder are generated. The problem was unresolved.

  Patent Document 5 discloses that aluminum oxide titanium carbide ceramics are used as a magnetic head substrate.

However, Altic, which is currently the mainstream as a magnetic head substrate for HDDs, has a volume resistivity of ^10-3 or less and a low volume resistivity value. There was a risk that electric discharge would easily occur rapidly and the magnetic head element would cause electrostatic breakdown.

  Patent Document 6 discloses a magnetic head substrate made of silicon carbide having high thermal conductivity and excellent heat dissipation. However, since silicon carbide has a high Vickers hardness of 20 GPa or more, its machinability is very poor. In the process of cutting out the magnetic head element by slicing, there has been a problem that chipping occurs and the wear of the tool is accelerated.

  Furthermore, when amorphous alumina, which is an insulating film, is formed on the magnetic head substrate, there is a problem in that the thermal expansion coefficient is different, and therefore, peeling occurs due to a temperature change.

  As described above, the aluminum oxide titanium nitride-based material that has been conventionally provided cannot be sufficiently used as a magnetic head substrate.

  Further, other materials described above still have a problem as a magnetic head substrate.

  Further, in Patent Document 7, when the pressing member of the ultrasonic motor is formed of a composite ceramic of aluminum oxide and titanium carbide, titanium carbide reacts with oxygen in the atmosphere due to frictional heat during sliding to become titanium oxide, While it has the effect of suppressing the slip by increasing the coefficient of friction, there is a problem that the hardness and strength are lowered, so that the wear resistance is lowered and the life of the motor is shortened.

  In order to solve such a problem, the present invention has 65 to 85% by mass of aluminum oxide and the balance of titanium nitride as the main components, and the crystal grain size of both the crystal grains made of aluminum oxide and the crystal grains made of titanium nitride. The total average (hereinafter referred to as the total average crystal grain size) is 0.4 to 2.0 μm, the average crystal grain size of the aluminum oxide is 0.5 to 2.2 μm, and the average crystal grain size of the titanium nitride The aluminum oxide titanium nitride-based sintered body is characterized in that is 0.2 to 1.6 μm.

  Moreover, 0.005 to 1 part by weight of at least one of ytterbium oxide and yttrium oxide is contained with respect to 100 parts by weight of the main component.

  Further, 5 to 20 parts by weight of two or more selected from ytterbium oxide, magnesium oxide, zirconium oxide, titanium oxide, silicon oxide, and calcium oxide are contained with respect to 100 parts by weight of the main component.

The volume resistivity of the aluminum oxide titanium nitride sintered body is 10 ⁻³ or more and less than 10 ⁶ Ω · cm.

  Further, the thermal conductivity of the aluminum oxide titanium nitride sintered body exceeds 23 W / m · K.

  Further, the thermal expansion coefficient of the aluminum oxide titanium nitride-based sintered body is 7.2 to 7.8 ppm / ° C.

And the substrate for magnetic heads using the said aluminum oxide titanium nitride type sintered compact is provided.

  Furthermore, the ultrasonic motor characterized by using the said aluminum oxide titanium nitride type sintered compact for a press member is provided.

  Furthermore, the present invention provides a dynamic pressure bearing characterized in that the aluminum oxide titanium nitride sintered body is used for a sliding surface where dynamic pressure is generated.

  Also provided is a method for producing an aluminum oxide titanium nitride sintered body comprising the steps of preparing, forming and firing the titanium nitride powder synthesized by a vapor phase method in the method for producing an aluminum oxide titanium nitride sintered body. To do.

  Further, the present invention provides a method for producing an aluminum oxide titanium nitride sintered body characterized in that the firing step is a hot press, and the maximum temperature is 1530 to 1780 ° C. and the applied pressure is 30 to 60 MPa.

  The main component is 65 to 85% by mass of aluminum oxide and the remaining titanium nitride, the total average crystal grain size is 0.4 to 2.0 μm, and the average crystal grain size of the aluminum oxide is 0.5 to 2.2 μm. The aluminum nitride titanium nitride-based sintered body having an average grain size of titanium nitride of 0.2 to 1.6 μm is mirror-finished while suppressing a reduction in surface roughness due to ion milling or the like Therefore, the groove 20b and the like can be processed in the air bearing surface 20a with high accuracy. Further, when used for a magnetic head slider, the flying height from the magnetic disk can be measured accurately by a laser.

  Further, by setting the average crystal grain size of the aluminum oxide to 0.5 to 2.2 μm and the average crystal grain size of the titanium nitride to 0.2 to 1.6 μm, the total average crystal grain size is 0.4 μm or more. 1.2 μm or less, and the strength of the material can be 600 MPa or more.

Furthermore, the volume resistivity can be made 10 ⁻³ Ω · cm or more and less than 10 ⁶ Ω · cm by using 65 to 85 mass% of the aluminum oxide and the remaining titanium nitride.

  Further, it contains 0.005 to 1 part by weight of at least one of ytterbium oxide and yttrium oxide with respect to 100 parts by weight of the main component, and is fired by hot pressing, so that there is little glass phase and excellent milling accuracy. In addition, an aluminum oxide titanium nitride-based sintered body can be obtained, which is particularly preferable when used for a magnetic head slider.

  Further, by containing 5 to 20 parts by weight of two or more selected from ytterbium oxide, magnesium oxide, zirconium oxide, titanium oxide, silicon oxide, and calcium oxide with respect to 100 parts by weight of the main component, sinterability Thus, a dense aluminum oxide titanium nitride-based sintered body can be obtained without using a hot press.

Further, by setting the volume resistivity of the aluminum oxide titanium nitride-based sintered body to 10 ⁻³ or more and less than 10 ⁶ Ω · cm, static electricity can be prevented from being charged to the member.

  Further, when the thermal conductivity of the aluminum oxide titanium nitride sintered body exceeds 23 W / m · K, the heat generated from the magnetic head element can be radiated more rapidly than Altic.

  Moreover, when the thermal expansion coefficient of the aluminum oxide titanium nitride-based sintered body is set to 7.2 to 7.8 ppm / ° C., when amorphous alumina is formed on the sintered body, peeling due to the difference in thermal expansion coefficient Generation of cracks can be prevented.

  The magnetic head substrate characterized by using the aluminum oxide titanium nitride-based sintered body reduces the risk of electrostatic breakdown in the magnetic head element and provides high-precision milling with small variations in surface irregularities. Thus, the wear powder and corrosion generated from the glass phase can be reduced, and the magnetic head substrate can be suitably used.

  Furthermore, the ultrasonic motor using the aluminum oxide titanium nitride sintered body as the pressing member has high durability of the pressing member, and can extend the life of the motor.

  Furthermore, a hydrodynamic bearing characterized in that the aluminum oxide titanium nitride sintered body is used for a sliding surface where dynamic pressure is generated is a bearing member having excellent wear resistance and sliding properties.

  In addition, the present invention can obtain an aluminum nitride titanium nitride-based sintered body with few foreign matters by preparing, molding, and firing using titanium nitride powder synthesized by a vapor phase method. It is suitable for use as a substrate.

  Further, in the present invention, the sintering step is a hot press, and the aluminum oxide titanium nitride-based sintered material having a fine crystal structure is obtained by setting the maximum temperature to 1530 to 1780 ° C. and the applied pressure to 30 to 60 MPa. You can get a body.

  The best mode for carrying out the present invention will be described.

  The present invention is mainly composed of 65 to 85% by mass of aluminum oxide and the balance of titanium nitride, and the total average grain size of the crystal grains made of aluminum oxide and the crystal grains made of titanium nitride is 0.4 to 2.0 μm. The aluminum oxide has an average crystal grain size of 0.5 to 2.2 μm, and the titanium nitride has an average crystal grain size of 0.2 to 1.6 μm. Is the body.

  Here, aluminum oxide refers to the general α-type, but titanium nitride is an interstitial solid solution, so it does not follow the general bond law, and carbon and oxygen etc. are also mutually involved in the powder manufacturing process. May dissolve in In the present invention, when the total solid solution amount of nitrogen, carbon, oxygen and the like is 100 parts by weight, the solid solution amount of nitrogen is 80 parts by weight or more.

  The reason why aluminum oxide is used in the sintered body of the present invention is that aluminum oxide is inexpensive and it is easy to obtain high-purity raw materials. Titanium nitride is used because it has electrical conductivity, so that the sintered body can be prevented from being charged with static electricity. When sintered as a composite material with aluminum oxide, the thermal conductivity is the conventional substrate material for magnetic heads. This is because it has higher oxidation resistance than titanium carbide, which is higher than some Altic.

  Although depending on the manufacturing method, the oxidation temperature of powdered titanium carbide is about 400 ° C, whereas the oxidation temperature of titanium nitride is about 500 ° C, so it is used as a sliding member compared to Altic. If so, surface oxidation of the sintered body due to the chemomechanical reaction can be suppressed.

  In the present invention, the reason why the aluminum oxide is 65% by mass or more and 85% by mass or less and the balance is titanium nitride is to maintain appropriate electrical conductivity while maintaining the material strength.

  If the amount of aluminum oxide is less than 65% by mass, the amount of titanium nitride is too large, so that the sinterability is significantly reduced, the strength and void level of the sintered body are lowered, and the workability is also deteriorated, so that chipping during slicing is performed. The problem arises that increases.

  On the other hand, if the aluminum oxide exceeds 85% by mass, the amount of titanium nitride is too small, so that the hardness and wear resistance are reduced, and it becomes difficult to maintain the conductivity. As shown in FIG. The specific resistivity rapidly increases, which is not preferable from the viewpoint of static electricity removal.

  The reason why the volume resistivity is stabilized in this range is considered to be that the bonds between the conductive titanium nitride particles spread almost uniformly over the entire sintered body and are in a stable state. Furthermore, the content of aluminum oxide is more preferably in the range of 70% by mass to 82% by mass. In this range, since the volume resistivity is stable and the strength is sufficient, a sintered body that is stable in quality can be obtained even in an actual manufacturing process.

  Further, as a desirable characteristic of the aluminum oxide titanium nitride sintered body of the present invention, the total average crystal grain size is preferably in the range of 0.4 μm or more and 2.0 μm or less.

  The total average crystal grain size is set to 0.4 μm or more in order to produce a sintered body having a total average crystal grain size of less than 0.4 μm, the crystal grain size before sintering is 0.1 to 0.2 μm. This is because it needs to be pulverized to a certain extent, and there are few cost and time advantages. Furthermore, in order to suppress grain growth, firing is performed in a short time, sintering does not proceed sufficiently, voids remain, the strength decreases, and the surface roughness after milling also deteriorates.

  The total average crystal grain size was set to 2.0 μm or less in order to maintain a good mirror surface workability of the member and to uniformly disperse the processing rate difference for each crystal phase by ion milling or etching. is there.

  Furthermore, for example, when used as a magnetic head substrate, if the total average crystal grain size is 2.0 μm or less, the laser spot diameter used when measuring the flying height of the magnetic head described above is 4 to 6 μm. Even if the laser is irradiated to an arbitrary place on the air bearing surface, a plurality of crystal phases are always included in the spot, and a stable measurement condition can be obtained.

  Conversely, the case where the total average crystal grain size exceeds 2.0 μm is the case where the primary raw material is coarse or the firing temperature is too high, the material strength is reduced, and the mirror surface workability, ion milling property, etc. The problem of deteriorating arises.

  A more desirable range of the total average crystal grain size is 0.5 μm or more and 1.4 μm or less.

  The average crystal grain size of aluminum oxide is preferably 0.5 μm or more and 2.2 μm or less, and the average crystal grain size of titanium nitride is preferably 0.2 μm or more and 1.6 μm or less.

  The average crystal grain size of aluminum oxide is 0.5 μm or more and 2.2 μm or less, and the average crystal grain size of titanium nitride is 0.2 μm or more and 1.6 μm or less. This is because, when the firing temperature is set, the material becomes strong while maintaining the strength of the material while maintaining an appropriate conductivity, and having excellent mirror surface workability and ion millability.

  When the average crystal grain size of aluminum oxide is less than 0.5 μm, the bonding between aluminum oxide and titanium nitride in the sintering process becomes insufficient and the material strength decreases. Conversely, when it exceeds 2.2 μm, aluminum oxide Abnormal crystal growth occurs frequently, which also causes a decrease in strength and deteriorates the mirror surface workability.

  Furthermore, if the average crystal grain size of titanium nitride is less than 0.2 μm, the material characteristic advantage is not seen and the cost advantage is small for the longer raw material grinding time. On the other hand, if the average crystal grain size of titanium nitride exceeds 1.6 μm, the firing temperature becomes high, so that the aluminum oxide crystal grains tend to cause abnormal grain growth and cause a reduction in strength of the member. On the other hand, even if firing at a low temperature to suppress abnormal grain growth of aluminum oxide, the strength decreases because voids remain at the grain boundaries of titanium nitride and aluminum oxide. Further, when the titanium nitride crystal grains become large, the path through which static electricity passes is likely to be broken, resulting in a large variation in the conductivity of the sintered body and unstable quality.

  More preferably, the average crystal grain size of titanium nitride is smaller than that of aluminum oxide. This is because titanium nitride is difficult to sinter, so if the average crystal grain size is larger than that of aluminum oxide, voids are likely to be formed at the grain boundaries with the aluminum oxide crystal, causing a reduction in strength. . Further, when grinding or mirror finishing is performed on the sintered body, degranulation and chipping are likely to occur, and the deterioration of the surface properties also causes a decrease in strength.

  In order to make the total average crystal grain size within the range of the present invention, the pulverized grain sizes of aluminum oxide and titanium nitride are in the ranges of D50 = 0.1 to 1.8 and D50 = 0.1 to 1.4, respectively. The kind and amount of the sintering aid are appropriately adjusted, the firing temperature is 1530 to 1780 ° C., and the firing equipment may be a hot press or a vacuum furnace (argon atmosphere, nitrogen atmosphere).

  The total average grain size is measured by taking a mirror surface of the sintered body at a magnification of about 1000 to 5000 times using a scanning electron microscope (hereinafter referred to as SEM) and drawing a straight line at an arbitrary position on the photograph. Measure by the code method. If fire etching is performed at a temperature lower by 50 to 200 ° C. than the firing temperature before SEM, the grain boundary can be easily observed.

Further, the present invention contains 0.005 parts by weight or more and 1 part by weight or less of either ytterbium oxide or yttrium oxide as a sintering aid with respect to 100 parts by weight of aluminum oxide and titanium nitride as main components. The use of ytterbium oxide or yttrium oxide as a sintering aid can improve the sinterability of aluminum oxide and titanium nitride in a trace amount of 0.005 parts by weight or more and 1 part by weight or less. Because. And the sintered body of the present invention sintered with a small amount of sintering aid is excellent in mirror surface workability because the glass phase component at the grain boundary is extremely small, and even with ion milling, the surface roughness Does not drop drastically. In addition, when slicing the sintered body, there are advantages that chipping of the cut surface is reduced and that the amount of particles generated is small.

  Further, when the added amount is less than 0.005 parts by weight, there is a problem that the sinterability is not improved. When the added amount exceeds 1 part by weight, ytterbium oxide and yttrium oxide are aggregated to cause unevenness of the structure, and the above-described magnetic property Like the head, when measuring the flying height of the magnetic head using the reflectivity of light, in addition to the problem that it can not be measured accurately, a translucent thin film is formed on the surface of the sintered body, When measuring the thickness using light, there is a problem that the reflectance is partially changed and cannot be measured accurately, and there is a problem that aggregated particles become projections on the ion milling surface, which is preferable as a substrate for a magnetic head. Absent.

  And more preferable content of ytterbium oxide and yttrium oxide is 0.01 parts by weight or more and 0.5 parts by weight or less. In this range, the sinterability can be improved with a small amount of sintering aid, no agglomerates are generated, and the strength is excellent.

  When either ytterbium oxide or yttrium oxide is added to the sintering aid, it is necessary to use a hot press in order to densify the sintered body. This is because the amount of sintering aid is so small that sintering does not proceed even when a vacuum furnace is used. Moreover, you may use hot isostatic press baking (henceforth HIP) instead of a hot press.

  In the present invention, one or more of ytterbium oxide, yttrium oxide, magnesium oxide, zirconium oxide, titanium oxide, silicon oxide, and calcium oxide are used as sintering aids with respect to 100 parts by weight of aluminum oxide and titanium nitride as main components. It contains 5 parts by weight or more and 20 parts by weight or less.

  Ytterbium oxide and yttrium oxide improve the sinterability of aluminum oxide and titanium oxide in a trace amount, magnesium oxide has the effect of suppressing grain growth of the main component, zirconium oxide improves the workability of the sintered body, Titanium oxide densifies the sintered body, silicon oxide forms a glass phase to lower the sintering temperature, and calcium oxide has the effect of stabilizing the grain boundary phase.

  The sintered body of the present invention contains these sintering aids in an amount of 5 parts by weight or more and 20 parts by weight or less without using an expensive facility such as a hot press or HIP. This is because sufficient strength and hardness can be obtained even by firing in an atmospheric furnace. Note that there is no problem even if baking is performed using a hot press, and after baking in a normal vacuum furnace, the material properties such as strength and hardness can be improved by densification using HIP.

  Further, if the sintering aid is less than 5 parts by weight, the effect of improving the sinterability is low, and if it exceeds 20 parts by weight, the strength and wear resistance are lowered, which is not preferable. And the addition amount of a more preferable sintering aid is 8 parts by weight or more and 15 parts by weight or less.

Further, the present invention is the specific volume resistivity is ^{10 -3 Ω} · cm or more, the sintered body of the present invention, characterized in that less than 10 ⁶ Ω · cm, the volume resistivity ^{10 -3 Ω} · cm As described above, by using less than 10 ⁶ Ω · cm, for example, when used for a magnetic head substrate, Altic material (volume specific resistivity: about 10 ⁻³ Ω · cm), which is currently mainstream as a magnetic head substrate for HDD, is used. ), The sintered body of the present invention can be used as a substrate for a magnetic head for HDDs without adding countermeasures against static electricity in a conventional production line. It becomes possible. Further, it can be suitably used for a jig around an electronic component where electrostatic breakdown is a problem, such as a magnetic head element.

Also, when the volume resistivity is less than 10 ⁻³ Ω · cm, the amount of titanium nitride added exceeds 35% by mass as shown in FIG. There is a problem that the level and workability deteriorate.

In addition, when the volume resistivity is 10 ⁶ Ω · cm or more, particularly when used as a substrate material for a magnetic head, the conductivity is lowered. Therefore, it is necessary to separately add a countermeasure such as a static eliminating film to the member. As a result, the number of steps increases, which is not preferable in terms of cost. In view of electrostatic breakdown resistance, the volume resistivity is more preferably in the range of 10 ⁻³ Ω · cm to 10 ⁴ Ω · cm.

  In order to make the volume resistivity within the range of the present invention, the total average grain size of the sintered body is 0.4 μm or more and 2.0 μm or less, and aluminum oxide is 65% by mass or more and 85% by mass or less. The remainder may be formed of titanium nitride.

  Specifically, the volume resistivity is smaller as the content of titanium nitride is larger and the total average crystal grain size is smaller. Since titanium nitride has electrical conductivity, the volume resistivity of the sintered body decreases as the content increases. When the total average crystal grain size decreases, the titanium nitride is tertiary between the insulating aluminum oxide crystal grains. It becomes easy to form an original network structure, and the volume resistivity decreases.

The measurement of the specific volume resistivity, if it is less than 10 ⁶ Ω · cm for low-resistance measured by the four-terminal method conforming to JIS K 7194, in the case of more than 10 ⁶ Ω · cm high resistance JIS K 6911 The measurement may be performed by the double ring method in accordance with the above.

  The sintered body of the present invention is characterized in that the thermal conductivity exceeds 23 W / m · K.

  For example, when conventional Altic is mixed at a ratio of 70% by mass of aluminum oxide and 30% by mass of titanium carbide and sintered at 1750 ° C. for 1 hour using a hot press, the thermal conductivity is 23 W / (m · K). In contrast, when the sintered body of the present invention is mixed at a ratio of 70% by mass of aluminum oxide and 30% by mass of titanium nitride and sintered under the same conditions, the thermal conductivity is 24 to 27 W / m · K. Thus, higher thermal conductivity than Altic can be obtained. This is because the thermal conductivity of titanium nitride is larger than that of titanium carbide.

  In addition, as shown in Table 4, the thermal conductivity can be improved up to 30 W / (m · K) in the composition range of the present invention.

  In order to adjust the thermal conductivity, there are mainly a method of adjusting the mass ratio of aluminum oxide and titanium nitride and a method of adjusting the crystal grain size. In order to increase the thermal conductivity, the ratio of aluminum oxide is increased, the crystal grain size is increased, or both. That is, aluminum oxide has a higher thermal conductivity than titanium nitride, and when the crystal grain size is increased, grain boundaries that are factors that hinder thermal conduction are reduced. There is also a method of adjusting the sintering aid, but the effect is small in the sintered body of the present invention.

  And when the thermal conductivity becomes higher than Altic, for example, when the sintered body of the present invention is used for a magnetic head substrate, the heat generated from the magnetic head element is quickly dissipated and malfunction due to heat. And has the effect of suppressing overheating. Further, when used for the sliding member, similarly, the heat generated on the sliding surface is released to the surroundings to suppress the temperature rise of the member and to reduce the dimensional change due to thermal expansion.

  The thermal conductivity may be measured by a laser flash method in accordance with JIS C 2141.

  Furthermore, the sintered body of the present invention has a thermal expansion coefficient of 7.2 ppm / ° C. or more and 7.8 ppm / ° C. or less.

  By making the coefficient of thermal expansion within the range of the present invention, for example, when used for a magnetic head substrate, when an amorphous alumina of an insulating film is formed on the magnetic head substrate, it becomes a material having excellent adhesion. The production equipment used for the Altic material can be diverted as it is.

  In order to set the coefficient of thermal expansion to 7.2 ppm / ° C. or more and 7.8 ppm / ° C. or less, the mass ratio of aluminum oxide, titanium nitride, and sintering aid may be adjusted within the scope of the present invention. Specifically, as the mass ratio of aluminum oxide increases, the coefficient of thermal expansion increases.

  The coefficient of thermal expansion may be measured by a thermomechanical analysis method based on JIS R 1618.

  The present invention also provides a magnetic head substrate using an aluminum oxide titanium nitride sintered body.

  The magnetic head substrate using the sintered body of the present invention has higher thermal conductivity and better heat dissipation than the current mainstream Altic magnetic head substrate, and the oxidation resistance of titanium nitride compared to titanium carbide. It has an excellent effect that the existing equipment can be diverted because it has a high thermal expansion coefficient equivalent to Altic.

  In particular, a sintered body containing 0.005 part by weight or more and 1 part by weight or less of either ytterbium oxide or yttrium oxide as a sintering aid can process the air bearing surface 20a with high accuracy by ion milling or the like. When the subsequent surface roughness is measured with an atomic force microscope (hereinafter referred to as AFM), it becomes Ra 20 nm or less and can be suitably used as the magnetic head slider 20. That is, since the glass phase component at the grain boundary is extremely small, there are very few harmful irregularities on the air bearing surface 20a after processing, and the vehicle can float and travel in a stable state.

  In Altic, there is no void of 1 μm or more on the surface of the magnetic head substrate, and even when the sintered body of the present invention is used for the magnetic head substrate, the void level is equal to or higher than this. preferable.

  Further, the magnetic head substrate according to the present invention has a small chipping 90 (FIG. 9) generated on the cut surface when the magnetic head element formed on the substrate is separated by slicing, and interferes with the magnetic head element to hinder its function. There is nothing.

  And this invention is an ultrasonic motor characterized by using the aluminum oxide titanium nitride type sintered compact for the press member.

  The sintered body of the present invention is excellent in wear resistance and oxidation resistance, and when used in a pressing portion of an ultrasonic motor, the sintered body is superior in durability than the conventionally proposed Altic. Furthermore, since the thermal conductivity is higher than that of Altic, it is possible to dissipate frictional heat at the time of driving faster, reduce deformation due to thermal expansion of the pressing portion, and realize accurate feeding. 6 and 7 show a rod-shaped ultrasonic motor and a guide device using the same, it can also be used for an annular ultrasonic motor.

  The present invention also provides a hydrodynamic bearing characterized in that an aluminum oxide titanium nitride sintered body is used for a sliding surface where dynamic pressure is generated.

  Since the sintered body of the present invention is excellent in wear resistance and oxidation resistance, it can be suitably used for a sliding surface of a hydrodynamic bearing that contacts and slides at high speed. For example, Altic's hydrodynamic bearings that have been proposed in the past (JP-A-8-121467, etc.) are materials that are superior in wear resistance and slidability compared to conventional aluminum oxide hydrodynamic bearings. . However, titanium nitride contained in the sintered body of the present invention is superior in oxidation resistance compared to titanium carbide existing on the sliding surface of Altic's dynamic pressure bearing, so the surface composition changes due to frictional heat. Can be used stably even in a use environment where the member is at a high temperature.

  Further, the titanium nitride used in the present invention is preferably synthesized by a vapor phase method capable of obtaining a fine powder material with high purity as compared with conventional metal nitriding methods and thermal carbon nitriding methods. Here, the vapor phase method is a method of synthesizing titanium nitride by heating gaseous titanium chloride in a reaction gas in which a nitriding reaction occurs. Examples of the reactive gas include a mixed gas of hydrogen and nitrogen and ammonia.

  In addition, the metal nitriding method is a method of synthesizing titanium nitride by heating metal powder in a reaction gas, but for safety reasons during production, after synthesizing coarse titanium nitride, it is pulverized and pulverized. The manufacturing method to be taken is taken. Since impurities are mixed during the pulverization after the synthesis, it is not suitable for use in the magnetic head substrate of the present invention.

  The thermal carbon nitriding method is a method of synthesizing titanium nitride by heating a mixed powder of titanium oxide and carbon in a reaction gas. Titanium nitride synthesized by this method is inexpensive but is not suitable for use in the magnetic head substrate of the present invention because of its low purity.

  In the present invention, in order to reduce impurities, it is more preferable to use alumina balls having a purity of 99.9% or more for pulverizing the raw material. For example, when a cemented carbide ball or a zirconia ball is used in consideration of grinding efficiency, for example, when the sintered body of the present invention is used for a magnetic head substrate, impurities are mixed from the grinding ball, and ion milling is performed. There is a problem that harmful irregularities occur on the surface, which is not preferable.

  However, titanium nitride obtained by a manufacturing method other than the vapor phase method can also be used when used for a wear-resistant jig or sliding member which is another application.

  The method for producing a sintered body according to the present invention uses a hot press to have a maximum temperature of 1530 ° C. or more and 1780 ° C. or less, a maximum temperature holding time of 30 minutes or more and 3 hours or less, and a maximum pressure of 30 MPa or more and 60 MPa or less. And it is sufficient.

  The reason why the maximum temperature is set to 1530 ° C. or higher and 1780 ° C. or lower is that the sinterability is lowered at 1530 ° C. or lower, and the reason why the maximum temperature is set to 1780 ° C. or lower is to suppress the growth of crystal grain size.

  The reason why the maximum pressure is set to 30 MPa or more and 60 MPa or less is that the sinterability decreases when the pressure is 30 MPa or less. The reason why the maximum pressure is set to 60 MPa or less is that the sinterability is greatly improved although the apparatus cost increases. It is because it is not possible.

  Furthermore, the maximum temperature holding time is desirably 30 minutes or more and 3 hours or less. That is, if the time is less than 30 minutes, the time is too short, so that there is a problem that uneven sintering occurs in the sintered body. If the time exceeds 3 hours, the crystal grain size tends to cause abnormal grain growth.

  Further, when hot pressing is performed, it is preferable to apply a boron nitride or graphite release agent to the mold or spacer in order to prevent reaction between the sintered body and carbon used in the mold or spacer.

  Furthermore, the sintered body using the sintered body of the present invention is further densified by performing HIP on the sintered body obtained by the above-described manufacturing method in an inert gas to eliminate the remaining voids. Is also possible.

  In addition, when the sintered body of the present invention is used for a magnetic head substrate, annealing can be performed after hot pressing or after HIP in order to reduce internal stress remaining in the magnetic head substrate. Here, annealing is performed in a vacuum or in an inert gas such as helium, argon, nitrogen, etc. In order to prevent the reaction between the magnetic head substrate and the setter, a floor plate or case made of the same material as the magnetic head substrate is used. preferable.

  The sintered body of the present invention can also be used for tweezers, cases, processing jigs, sliding members and the like for holding electronic components.

(Example 1)
Next, the relationship between the total average crystal grain size, milling property, and void level of the sintered body of the present invention will be described.

  First, 0.1 parts by weight of aluminum oxide having a purity of 99.99% by mass or more, titanium nitride having a purity of 95% by mass or more, and ytterbium oxide as a sintering aid were prepared as the main components. Then, aluminum oxide as a main component and titanium nitride are mixed at a ratio of 75% by mass: 25% by mass, 0.1 part by weight of ytterbium oxide is added as a sintering aid to 100 parts by weight of the main component, and IPA (Isopropyl alcohol) was added to a vibration mill and wet pulverized using pulverized balls made of zirconium oxide. Here, the reason why IPA was used instead of water for pulverization is to prevent the oxidation of TiN as much as possible.

  The particle size distributions of aluminum oxide and titanium nitride after completion of pulverization were adjusted in the ranges of D50 = 0.12 to 1.45 and D50 = 0.15 to 1.1. The particle size distribution was measured by a laser diffraction method, and the device used was Microtrack (manufactured by Nikkiso Co., Ltd .: 9320-X100).

  And after adding a small amount of binder to the slurry after pulverization and mixing, IPA was evaporated and used as a powder raw material through a mesh pass.

  Next, the obtained powder material is press-molded to form a molded body, degreased, and then hot-pressed by induction heating under the conditions of a set temperature of 1400 to 1800 ° C., a pressure of 30 to 60 MPa, and a keep time of 0.1 to 4 Hr. A plurality of samples of φ127 × T2.5 to 3.5 mm were prepared, and these samples were further processed to a thickness of 2 mm with a surface grinder and mirrored with a lapping machine.

  And the mirror surface was observed by 3000 times using SEM (the JEOL Co., Ltd. product: JSM6700F), the total average crystal grain diameter was measured using the code | cord | chord method, and the value below two decimal places was rounded off. Prior to SEM, fire etching was performed using a vacuum furnace at a temperature lower by 50 to 200 ° C. than the firing temperature to facilitate observation of grain boundaries.

  Moreover, the evaluation method of milling property performed the milling process using the argon ion to the mirror-finished sample, and measured the surface roughness by AFM. The milling process conditions were an acceleration voltage of argon ions of 600 V and a milling rate of 200 Å / min for 10 minutes. The surface roughness Ra before milling of each sample was 1 to 2 nm, the surface state was measured after processing about 0.5 μm, and samples with Ra of 20 nm or less were accepted.

  The void level was evaluated by taking a 3000 times photograph with a SEM and passing 50 or less voids with a diameter of 1 μm or less in the range of 30 μm × 30 μm. Those with 51 or more voids having a diameter of 1 μm or less and those containing voids with a diameter exceeding 1 μm were disqualified and marked as x. Here, as the diameter of the void, a value obtained by dividing the sum of the major axis and minor axis of the void by 2 was used.

The results are shown in Table 1.

  From Table 1, sample No. which is an example of the present invention is shown. It can be seen that 2 to 7 are good in milling property and void level. Milling properties are No. No significant difference appeared between 2 and 7, but no. Nos. 3 to 6 have excellent void levels, and can be suitably used for sliding members such as magnetic head sliders.

  In addition, sample No. No. 1 has a small total average crystal grain size, but it is considered that milling property and void level were lowered because sintering did not proceed sufficiently. Similarly, sample No. Nos. 8 and 9 passed the void level, but no. Compared with 2-7, many marks of degranulation were seen, and in addition, the time required for mirror finishing was 10-50% longer. Furthermore, the milling property is also deteriorated, and it is considered that the difference in the milling rate for each crystal phase has appeared remarkably.

  Next, the relationship between the total average crystal grain size of aluminum oxide and titanium nitride and the strength will be described.

  In the same manner as described above, the sample No. 12 to 21 and Comparative Sample No. 10, 65, and 22 as aluminum oxide and titanium nitride 35% by mass separately with a vibration mill, adjusting the particle size, mixing and stirring, evaporating IPA, and forming the compact from the powder raw material Then, a sample was prepared by hot pressing.

  The sintering aid ytterbium oxide was pulverized at the same time as aluminum oxide, and was prepared so as to be 0.1 part by weight with respect to 100 parts by weight as the main components of aluminum oxide and titanium nitride.

  Similarly, the sample No. used as an example of the present invention. 27-36 and Comparative Sample No. As 25, 26, 37 to 39, 0.1 part by weight of ytterbium oxide was prepared with respect to a total of 100 parts by weight of 85% by weight of aluminum oxide and 15% by weight of titanium nitride, and samples were prepared by hot pressing.

  In addition, the temperature and pressure conditions were set so that the hot press had the total average crystal grain size shown in Table 2. At this time, the average crystal grain size of titanium nitride was in the range of 30 to 100% with respect to the average crystal grain size of aluminum oxide.

  The crystal grain size was measured by the method described above, and the bending strength was determined by a three-point bending test (JIS R 1601).

The results are shown in Table 2 and graphed in FIG. D in FIG. 8 is the range of the total average grain size of the present invention.

  From Table 2 and FIG. 8, sample No. which is an example of the present invention is shown. 12-21, no. Nos. 27 to 36 have a total average crystal grain size of 0.4 μm or more and 2.0 μm or less, have a bending strength of 600 MPa or more, and have the same strength as Altic. Furthermore, when the total average crystal grain size is in the range of 0.4 μm or more and 1.6 μm or less, the bending strength is 700 MPa or more, which is a more preferable range.

  Moreover, No. which is a comparative example. Nos. 10, 11, 25, and 26 have a small total average crystal grain size, but it was considered that the strength was lowered because sintering did not proceed sufficiently. And No. which is a comparative example. 22-24, no. 37-39 were not greatly reduced in strength, but were outside the scope of the present invention due to the above-mentioned problem of millability.

(Example 2)
In Example 2, the average crystal grain size of aluminum oxide, the average crystal grain size of titanium nitride, and the strength of the sintered body will be described.

The total average crystal grain size of the sintered body is within the scope of the present invention, but when the average crystal grain size of aluminum oxide is less than 0.5 μm, the sintered body in the case of exceeding 2.2 μm, similarly sintered The total average crystal grain size of the body is within the scope of the present invention, but when the average crystal grain size of titanium nitride is less than 0.2 μm, a sintered body is produced when the average crystal grain size exceeds 1.6 μm and the strength thereof is increased. It is shown in Table 3. The sample preparation method and the crystal grain size and bending strength measurement method are the same as in Example 1.

  From Table 3, sample No. which is an example of the present invention is shown. 41-43, 46, 47, 50-52, 55, 56 have a bending strength of 600 MPa or more, and it is understood that these are materials having a bending strength equivalent to Altic. No. 42 and 43 are No. The bending strength is higher than that of 41 by 100 MPa or more. This is presumably because the average crystal grain size of aluminum oxide is larger than the average crystal grain size of titanium nitride, and minute voids remaining at the crystal grain boundaries during sintering are reduced.

  Moreover, No. which is a comparative example. In Nos. 40 and 54, since sintering did not proceed sufficiently, it was considered that the average crystal grain size of aluminum oxide was small and the bending strength was lowered. On the contrary, No. which is a comparative example. Nos. 44 and 57 were considered to have been sintered too much, so that the average crystal grain size of aluminum oxide exceeded the range of the present invention and the bending strength was lowered.

  Furthermore, No. which is a comparative example. Nos. 45 and 53 are Nos. Compared with 46 and 52, it takes twice or more time to grind titanium nitride, but there is a problem that almost no improvement effect is seen in material properties.

  And No. which is a comparative example. 48 and 49 show that the average crystal grain size of titanium nitride is outside the range of the present invention, and the bending strength is lowered. That is, it is considered that because the average crystal grain size of titanium nitride is too large, the sinterability is lowered and minute voids remain in the crystal grain boundaries.

(Example 3)
Next, the mass ratio of aluminum oxide and titanium nitride in the sintered body of the present invention will be described.

  The mass ratio of aluminum oxide, titanium nitride, and ytterbium oxide, the set temperature, and the hot press pressure were adjusted to the conditions shown in Table 4 to prepare a sintered body.

Then, the volume resistivity, thermal conductivity, bending strength, and total average grain size were measured, and the void level and millability were also evaluated. The results are shown in Table 4.

From Table 4, sample No. which is an example is shown. 61 to 65 and 69 to 73 have a volume resistivity in the range of 10 ⁻³ Ω · cm or more and less than 10 ⁶ Ω · cm, and the thermal conductivity is Altic (20 to 23 W / (m · K)). It can be seen that, for example, it can be used as a magnetic head substrate having better heat dissipation than Altic.

  In addition, the coefficient of thermal expansion is 7.2 ppm / ° C. or more and 7.8 ppm / ° C. or less, and even when amorphous alumina is formed on the ceramic sintered body of the present invention by sputtering, the coefficient of thermal expansion is the same. There is little risk of peeling during heating and cooling.

  Further, when the void level was evaluated in the same manner as in Example 1, No. of the comparative example. 66 and 74 were out of the scope of the present invention because the void level was deteriorated.

  No. which is a comparative example. No. 58 is a comparative example of No. 58, because the hot press pressure is too high, cracks may occur and the yield is low. On the other hand, it was found that No. 75 had poor sinterability because the hot press pressure was too low, resulting in a low yield. Accordingly, the hot press pressure of the sintered body of the present invention is preferably in the range of 30 MPa to 60 MPa and the firing temperature is in the range of 1530 ° C. to 1780 ° C.

  Further, when the milling property was evaluated under the conditions of Example 1, No. 1 as an example. In the samples 61 to 65 and 69 to 73, the surface roughness was Ra 4 to 7 nm, which was almost the same level and passed. No. which is a comparative example. It has been found that 66 and 75 are not suitable for use as, for example, a magnetic head substrate because a large number of voids remain, the measured values vary greatly, and the surface roughness of the milling property is Ra 20 nm or more.

Example 4
Next, the case where a sintering aid is added to the sintered body of the present invention will be described.

  The mass ratio of the main component of aluminum oxide and titanium nitride was 65:35, which was the ratio at which the sinterability was most reduced within the scope of the present invention.

  Then, the case where only ytterbium oxide is added as a sintering aid to 100 parts by weight of the main components of aluminum oxide and titanium nitride is used as a sintering aid A, and three types of ytterbium oxide, magnesium oxide, and zirconium oxide. Is added at a mass ratio of 2: 5: 2 as a sintering aid B, and five types of ytterbium oxide, magnesium oxide, zirconium oxide, silicon oxide, and calcium oxide are used at 1: 2: 1: 2: The case of adding in 1 was designated as sintering aid C, and the material properties were investigated by changing the amount of the sintering aid added and the firing method. Moreover, even if yttrium oxide is added instead of ytterbium oxide, the same effect is obtained, and it may be selected as appropriate. Furthermore, a sample to which no sintering aid was added was also prepared for comparison.

  A hot press and a vacuum furnace were used for firing. The hot press pressure was fixed at 40 MPa for comparison, and the firing temperature was controlled by a B thermocouple built in the graphite mold. In the vacuum furnace, argon was introduced at a pressure of 30 to 80 kPa at 500 ° C. or higher, and a low temperature region of 1400 ° C. or lower was controlled by an R thermocouple, and a high temperature region above 1400 ° C. was controlled by a tungsten-rhenium thermocouple.

  Argon is introduced into the furnace in order to suppress deterioration of the surface of the sintered body, and nitrogen or helium may be substituted.

The results are shown in Table 5.

  Sample No. with no sintering aid added. Nos. 76-78 are examples No. Nos. 76 and 77 have a total average crystal grain size within the range of the present invention. Since the firing temperature of 78 was too high, the total average crystal grain size was out of the range of the present invention, and the strength was also lowered. That is, when no sintering aid is added, the firing temperature is desirably 1780 ° C. or lower.

  Sample No. as an example. Nos. 79 to 83 were found to be easy to sinter even at a low temperature as compared with the additive-free sample because the sintering aid A was added. Since these samples are sintered at a low temperature and become a dense sintered body, the total average crystal grain size is small, the strength is high, and the aggregate of the sintering aid is small. It can be used suitably. No. as an example. No. 84 is unsuitable for a substrate for a magnetic head because it has a larger amount of aggregated particles than a sample having a sintering additive added of 1 part by weight or less, and is preferably used for a jig or a sliding member. Moreover, No. which is a comparative example. When 85 was fired in a vacuum furnace, sintering did not proceed even at a firing temperature of 1800 ° C., and the strength did not increase. Therefore, when the sintering aid is 1.0 part by weight or less, it is preferable to use a hot press.

Here, the observation of the agglomerated particles of ytterbium oxide was performed by observing a 1 cm ² range at 750 times using SEM. In Table 5, a sample having 50 or less agglomerated grains was indicated by ◯, and a sample having more than 50 agglomerates was indicated by ×.

  Next, sample No. 86-92 added sintering aid B, and baked mainly in the vacuum furnace. No. which is a comparative example. In No. 86, 2 parts by weight of sintering aid B is added to 100 parts by weight of the main component. However, since a vacuum furnace is used, sintering does not proceed even when fired at 1800 ° C. Although it grew, it did not become a dense sintered body, and the total average grain size did not fall within the scope of the present invention.

  No. as an example. In Nos. 87 to 91, by adding 5 to 20 parts by weight of the sintering aid B, the sinterability was improved and the total average crystal grain size could be within the range of the present invention. In addition, by using a hot press, No. which is an example. 91 could also be sintered at low temperatures.

  No. as an example. 92 was found to be lower in strength than other samples, although within the scope of the present invention. This is considered to be because the amount of the sintering aid is increased and the strength of the grain boundary is lowered.

  Sample No. Nos. 93 to 99 were added with sintering aid C and fired mainly in a vacuum furnace. No. which is a comparative example. No. 93 has 2 parts by weight of sintering aid C added to 100 parts by weight of the main component, but since a vacuum furnace is used, sintering does not proceed even when fired at 1800 ° C. Although it grew, it did not become a dense sintered body, and the total average grain size did not fall within the scope of the present invention.

  No. as an example. Nos. 94 to 98 were able to improve the sinterability by setting the addition amount of the sintering aid C to 5 to 20 parts by weight, and the total average crystal grain size could be within the range of the present invention. Further, by using a hot press, No. 98 could also be sintered at low temperatures.

  No. as an example. 99 was found to be lower in strength than other samples, although it was within the scope of the present invention. This is considered to be because the amount of the sintering aid is increased and the strength of the grain boundary is lowered.

  In addition, the sintering aid C tends to have a lower firing temperature than the sintering aid B, which is considered to be an effect of containing silicon oxide and calcium oxide.

  From the above, it was found that the sintered body of the present invention can be sintered in both a hot press and a vacuum furnace by adding a sintering aid in an appropriate range.

  Moreover, although Example 4 showed and demonstrated an example of the mixing ratio of the sintering aid, the present invention is not limited to this.

(Example 5)
Next, the amount of particles generated from the sintered body of the present invention will be described.

  First, the sample No. of Example 4 was used as a measurement sample. 76, 78, 80, 82, 83, 84 were used. The sample was a disk shape of φ127 × T2 mm and both surfaces were mirror-finished. The mirror surface was set to Ra 5 nm or less when measuring 20 × 20 μm by AFM. The outer diameter end face was processed with a # 400 diamond grindstone using a grinding machine so as to have a predetermined size, and a 0.3 C face was formed.

  Before measuring the amount of particles, the particles are measured by ultrasonically cleaning the sample in pure water (38 kHz, 1200 W) to remove dirt adhering to the surface layer, and then ultrasonicating the sample in pure water. After washing, the amount of particles of 1 μm or more contained in the pure water was measured by a liquid particle counter (manufactured by Lion Co., Ltd .: PARTICLE COUNTER KL-11) for 10 ml. The number of measurements was 3 each, and the average value thereof was determined. Those having a particle amount of 10,000 or less were regarded as acceptable (◯) and those exceeding 10,000 were regarded as unacceptable (x).

  Furthermore, the state of occurrence of chipping 90 (FIG. 9) on the cut surface when slicing was performed on the same sample was observed.

  The slicing conditions were as follows: the wheel was 100 mm in diameter x 0.18 mm in width, the rotation speed was 7000 rpm, the feed rate was 60 mm / min, and the cut was down, and a plurality of lines were formed so that the total length was 1000 mm. Thereafter, 100 locations were observed at 500 times using a metal microscope, and the maximum value of the chipping size E was measured. As for the chipping size E, 10 μm or less was regarded as acceptable (◯), and those exceeding 10 μm were regarded as unacceptable (x).

  The acceptance criteria for the amount of particles and the chipping size were based on the case where the Altic substrate was measured under the same conditions.

Table 6 shows the measurement results of particles and chipping.

  From Table 6, it can be seen that the amount of particles tends to decrease as the amount of the sintering aid added decreases. This is considered because there is almost no glass phase in the grain boundary phase of aluminum oxide and titanium nitride.

  The chipping size is No. In 78 and 84, those exceeding 10 μm were generated. No. No. 78 has a total average crystal grain size of 2.3 μm or more, and it is considered that the graining at the time of cutting greatly affected the chipping size. No. In No. 84, it is considered that the chipping 90 was increased because the amount of the sintering aid added was large and many agglomerated grains were present (Example 4).

  In addition, the samples of Examples and Comparative Examples in Examples 1 to 5 described above have an average crystal grain size of titanium nitride in the range of 20 to 95% with respect to the average crystal grain size of aluminum oxide, unless otherwise specified. there were.

  When the average crystal grain size of titanium nitride is less than 20% with respect to the average crystal grain size of aluminum oxide, titanium nitride tends to agglomerate, resulting in insufficient formation of conductive paths in the sintered body and a large volume resistivity value. turn into. Furthermore, even when not aggregated, it is included in alumina during the sintering process, and the formation of the conductive path is hindered.

  In addition, when it is larger than 95%, titanium nitride is difficult to sinter. Therefore, when the average crystal grain size is larger than that of aluminum oxide, voids are easily formed at the grain boundary with the aluminum oxide crystal, and the strength is reduced. This is because it becomes a factor. Further, when grinding or mirror finishing is performed on the sintered body, degranulation and chipping are likely to occur, and the deterioration of the surface properties also causes a decrease in strength.

  As described above, the sintered body of the present invention has an appropriate volume resistivity, excellent millability and void level, strength is equivalent to Altic, and thermal conductivity is higher than Altic. For example, it can be used as a pressing member for a magnetic head substrate or an ultrasonic motor.

It is a graph which shows the relationship between the ratio of the titanium nitride of this invention, and a volume specific resistivity. It is a fragmentary sectional view which shows the measuring method of the flying height of the normal magnetic head slider. It is a surface view showing the relationship between the normal crystal grain size and the laser spot diameter It is sectional drawing which shows the relationship between a crystal grain size and a processing rate, (a) is a case where it is a large particle size, (b) is a case where it is a small particle size. FIG. 2A is a perspective view of a magnetic head, and FIG. 2B is a magnetic head substrate on which a magnetic head element is formed. (A) is a main surface of an ultrasonic motor, and (b) is a top view of the other main surface of the ultrasonic motor. It is a guide device top view using a normal ultrasonic motor. It is a graph of the relationship between the total average crystal grain size and bending strength of the present invention. It is a schematic diagram of normal chipping.

Explanation of symbols

11, 12 Crystal phase 20 Magnetic head slider 20a Air bearing surface 20b Rail 21 Magnetic disk 22 Incident laser 23 Reflected laser 24 Measuring unit 25 Laser transmission rod 26 Arm 30 Laser spot 41 Crystal phase 42 Crystal phase 43 Surface 50 before processing Magnetic head 51 Magnetic head element 60 Ultrasonic motor 60a Press member 60b Electrode film 60c Piezoelectric ceramic plate 60d Electrode film 60e Vibrator 70 Guide device 71 Guide member 72 Stage 72a Contact surface 90 Chipping 91 Cutting surface 92 Slicing direction

Claims (11)

The average crystal grain size, which is mainly composed of 65 to 85% by mass of aluminum oxide and the balance of titanium nitride, is 0.4 to 2.0 μm, and is the sum of both the crystal grains made of aluminum oxide and the crystal grains made of titanium nitride. The aluminum oxide has an average crystal grain size of 0.5 to 2.2 μm, and the titanium nitride has an average crystal grain size of 0.2 to 1.6 μm. . The aluminum oxide titanium nitride-based sintered body according to claim 1, wherein 0.005 to 1 part by weight of at least one of ytterbium oxide and yttrium oxide is contained with respect to 100 parts by weight of the main component. 2 to 5 parts by weight of two or more selected from ytterbium oxide, magnesium oxide, zirconium oxide, titanium oxide, silicon oxide, and calcium oxide are contained with respect to 100 parts by weight of the main component. The aluminum oxide titanium nitride-based sintered body described in 1. The aluminum oxide titanium nitride-based sintered body according to any one of claims 1 to 3, wherein the volume resistivity is 10 ^-3 or more and less than 10 ⁶ Ω · cm. The aluminum oxide titanium nitride-based sintered body according to any one of claims 1 to 4, wherein the thermal conductivity exceeds 23 W / m · K. The thermal expansion coefficient is 7.2 to 7.8 ppm / ° C., The aluminum oxide-titanium nitride sintered body according to claim 1, A substrate for a magnetic head, wherein the aluminum oxide titanium nitride sintered body according to any one of claims 1 to 6 is used. An ultrasonic motor using the aluminum oxide titanium nitride sintered body according to any one of claims 1 to 6 as a pressing member. A hydrodynamic bearing using the aluminum oxide titanium nitride sintered body according to any one of claims 1 to 6 on a sliding surface where dynamic pressure is generated. 7. The method for producing an aluminum oxide titanium nitride sintered body according to claim 1, wherein said aluminum oxide titanium nitride nitride has a step of preparing, molding and firing using titanium nitride powder synthesized by a vapor phase method. A method for producing a sintered body. 11. The method for producing an aluminum oxide titanium nitride sintered body according to claim 10, wherein the firing step is a hot press, wherein the maximum temperature is 1530 to 1780 [deg.] C. and the applied pressure is 30 to 60 MPa.

Images