KR20000012006A - Alumina sintered body and process for producing the same - Google Patents

Abstract

PURPOSE: A high-purity sintered body having an extremely fine pore and its preparation method by sintering specified alumina powder in the atmosphere are provided which are useful as a product which should not contain pores. CONSTITUTION: The process comprises a)a producing step of a slurry dispersed in a solvent by ultrasonic-irradiating in agitating alumina powder having a purity of above 99.99 weight% containing a polyhedral alpha alumina particle having a D/H ratio of 0.5-3.0, a number average particle diameter of 0.1-1.0 micrometer, and D90/D10 ratio of below 7 and containing a polyhedral particle having a substantially uncrushed surface without using a grinding media, or agitating it without using a grinding media after ultrasonic-irradiating; b)a manufacturing step of unprocessed goods by drying the slurry and moulding and c)a sintering step of the unprocessed goods at 1,400-1,800°C in the atmosphere. The alumina sintered body is useful for an element necessary to have corrosion resistance, a product susceptible to be influenced from an adhesion or an adsorption of a dust particle of instruments for manufacturing a semiconductor such as a vacuum chuck, pincers and hands using cleaning a silicon wafer, moving and surface- processing, a material for a hard disk and a magnetic head, a material for various mirrors for industrial use, and bioceramic material for the artificial teeth and an artificial femoral part.

Description

Alumina sintered body and manufacturing method thereof {Alumina sintered body and process for producing the same}

The present invention relates to an alumina sintered body and a method for producing the same. The alumina sintered body may be used in devices for semiconductor manufacturing, such as vacuum chucks, tweezers and hands used in applications involving cleaning, moving and surface processing of silicon wafers or devices that need to have corrosion resistance, which are primarily in contact with corrosive solutions and gases. Products easily affected by the adhesion or adsorption of dust particles; Or a material for which there should be no pores, such as materials for hard disks, materials for magnetic heads, materials for various industrial mirrors, and bioceramic materials for artificial teeth, artificial thigh heads, and the like.

As a component in the semiconductor manufacturing process, ceramic materials have generally been used to prevent the incorporation and contamination of metal components into silicon wafers. Sintered bodies of alumina and silicon carbide have been commonly used as ceramic materials. Sintered bodies of alumina and zirconia have also been used for bioceramics such as artificial teeth, artificial thigh heads and artificial knees in terms of incorporation of metals into living bodies, wear resistance and the like.

Conventional raw material powders such as alumina or silicon carbide in this application include fine particles having primary particles of 0.5 μm or less, which has the problem of being non-uniform powders having an elliptic form or an unbroken surface. In addition, each particle interior is heterogeneous and has a number of defects. The powder has a wide particle size distribution and contains a number of coarse aggregated particles. This causes the formation of pores in the sintering process. As a method of reducing such a pore, there is usually a method of adding some sintering agent. However, it was not possible to obtain a sintered body having a sufficiently high combustion density and few pores.

Ceramic sintered products for components of semiconductor manufacturing systems are used by mirror-polishing portions of them in contact with a silicon wafer. Ceramic sintered products manufactured from conventional raw material powders have a problem that the wafer is damaged by foreign matter such as dust particles adhering to the pores of the sintered body or the edges of the pores.

In addition, when a silicon wafer or the like supported on a ceramic sintered body having a large number of pores is subjected to a treatment such as heat treatment or plasma etching, this is caused by the reduction of particles or the elution of impurities such as Na from ceramics in the vicinity of the pores. Problem occurs.

In addition, the problem has become important as the achievement of higher density and higher integration of semiconductor devices proceeds. Therefore, there is a demand for a sintered body having high purity, high density, and few pores.

Also, in bioceramic such as artificial teeth, artificial thigh heads and artificial teeth, ceramic materials or polymeric materials used in pairs with them are worn by the edges of the pores on the polished surface. In addition, the pores become a starting point of crushing, thereby lowering the strength of the sintered compact and the reliability of the product.

In order to solve the above problems, plasma-resistant fluorine alumina ceramics and a manufacturing method thereof are described in Japanese Laid-Open Patent Publication No. 9-2864. In Japanese Laid-Open Patent Publication No. 9-2864, silicon oxide and calcium oxide are added thereto in a large amount of 0.3 to 0.7% by weight in order to reduce the area% of the green particles. As such, the problem regarding corrosion resistance in hot water, acid solutions or alkaline solutions remains. In addition, a sintered body having a few pores can be obtained by hot isostatic press. However, the industrial problem of sintering at high temperature and high pressure still remains.

The present inventors have found that a high-purity alumina sintered body having very few pores can be obtained by firing the alumina in an air atmosphere using a specific alumina powder as a raw material, and found that its productivity is high, thus completing the present invention.

That is, the present invention includes polyhedral particles having a surface that is substantially unbroken, wherein the D / H ratio (where D is the maximum particle diameter horizontal to the hexagonal lattice plane of the hexagonal dense lattice of α alumina, and H is α alumina). Is a maximum particle diameter perpendicular to the hexagonal lattice plane of the hexagonal dense lattice of;) is 0.5 or more and 3.0 or less; The number average particle size is 0.1 µm or more and 1.0 µm or less; Comprising α alumina particles in the form of polyhedron with a D90 / D10 ratio (where D10 and D90 are respectively 10% cumulative diameter from the smallest particle face and 90% cumulative diameter in the cumulative particle size distribution) , Alumina powder having a purity of 99.99% by weight or more is applied to ultrasonic irradiation while applying to mechanical stirring without using a grinding medium, or applied to ultrasonic irradiation and then to mechanical stirring without using a grinding medium to disperse it in a solvent. Producing a prepared slurry;

Drying and molding the slurry to prepare a green body; And

A method (1) for producing a polycrystalline alumina sintered body, comprising sintering the green body under an air atmosphere at a temperature in the range of 1400 ° C to 1800 ° C.

In addition, the present invention is applied to the ultrasonic irradiation while applying the alumina powder to which the sintering aid is applied to the mechanical stirring without using the grinding media, or applied to the ultrasonic irradiation and then to the mechanical stirring without using the grinding media. It relates to the method described in (1), which produces a slurry dispersed in a solvent.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

In the present invention, the alumina powder used as the raw material is alumina having a purity of at least 99.99% by weight and having a substantially unbroken surface, and when the wet sieving is carried out using a 5-μm-mesh filter, the residual amount of the sieve on the sieve is 100 ppm or more. The alumina powder has a D / H ratio (where D is the maximum particle diameter horizontal to the hexagonal lattice plane of the hexagonal dense lattice of α alumina and H is the maximum particle diameter perpendicular to the hexagonal lattice plane of the hexagonal dense lattice of α alumina) Α-alumina particles in the form of a polyhedron having a value of 0.5 or more and 3.0 or less, preferably 0.8 or more and 1.5 or less. The number average particle size of the α alumina particles is 0.1 μm or more and 1.0 μm or less, preferably 0.2 μm or more and 0.7 μm or less. In addition, the α alumina particles have a particle size distribution D90 / D10 ratio (where D10 and D90 are particle sizes at 10% cumulative diameter and 90% cumulative diameter from the smallest particle surface, respectively, in the cumulative particle size distribution). It is as follows.

Examples of the above-mentioned alumina powder include α alumina powder obtained by calcining transition alumina, or alumina powder which can be transferred to transition alumina by heat treatment under an air gas containing hydrogen chloride. (alpha) alumina can be obtained by the method described, for example in Unexamined-Japanese-Patent No. 6-191836.

When the average particle size of the primary particle of the alumina powder used as a raw material exceeds 1.0 micrometer, sintering degree falls and the number of the pores which remain in a sintered compact increases. In addition, if the particle size distribution is not as narrow as described above, the particle arrangement in the green body is not homogeneous, causing local growth of the particles, resulting in an increase in the number of residual pores. In addition, when the purity of the alumina is less than 99.99% by weight, this becomes a factor that can cause the incorporation of foreign matter into the semiconductor product, or the abnormal growth of the particles due to the foreign matter, thereby increasing the number of residual pores.

In addition, in the alumina powder having a primary particle size of 0.1 mu m or less, the interaction between the particles is strong to form aggregated particles, thereby increasing the number of pores.

As a raw material of the present invention, the average particle size of the alumina primary particles is preferably 0.2 µm or more and 0.7 µm or less.

Examples of the alumina raw material of the present invention include AA02 (primary particle size 0.2 μm), AA03 (primary particle size 0.3 μm), AA04 (primary particle size 0.4 μm) from SUMICORUNDUM (manufactured by Sumitomo chemical Co., Ltd.). And AA07 (primary particle size 0.7 μm). Its purity is at least 99.99% by weight.

In addition, when the purity of the alumina powder to be used as a raw material is 99.99% by weight or more, the alumina powder may contain an oxide or salt of an element other than aluminum in an amount of less than 0.01% by weight or may refer to a substance such as water, an organic substance, and a halogen element. It can contain in less than 1 weight part which can be removed from a raw material by heating at 1000 degrees C or less, without damaging the characteristic of the alumina sintered compact of this invention.

By using the above-mentioned high purity alumina powder as a raw material, it is possible to achieve uniform arrangement of particles in the green body, high combustion density, and uniform progress of particle growth in the whole sintered body. This reduces the pores that will remain at the sintered body assembly or assembly boundary. In addition, local abnormal growth of the particles due to impurities in the raw material does not proceed, and no pores remain. As a result, a high combustion density of 3.970 g / cm 3 can be obtained. In addition, a sintering agent is added when it is necessary to achieve higher combustion densities. This inhibits the growth of the assembly boundary in the final sintering step. As a result of such an effect, a sintered compact having a high combustion density of 3.975 g / cm 3 or more can be obtained.

Examples of sintering agents include one or more compounds selected from the group consisting of alkaline earth metal compounds and silicon compounds. Examples of alkaline earth metal compounds and silicon compounds include oxides, nitrates, acetates, hydrates, chlorides and alkoxides thereof. However, they are not limited to this as long as they become oxides at temperatures of 1200 ° C. or lower during sintering in the atmosphere. Specific examples of alkaline earth metals include Mg, Ca, Sr and Ba. As a sintering agent, a magnesium compound is preferable and magnesium nitrate is especially preferable. The addition amount thereof is generally 10 ppm or more and 2000 ppm or less, preferably 10 ppm or more and 700 ppm or less, in terms of oxide. Each of the above compounds becomes an oxide during sintering in the atmosphere and exerts its effect as a sintering agent. When a sintered compact having an alumina purity of 99.99% by weight or more is required according to its use, the sintering agent is added to the alumina powder in an amount of 10 ppm or more and 150 ppm or less, more preferably 10 ppm or more and 70 ppm or less in terms of oxide.

The method for producing the slurry is described below. First, the alumina raw material powder, the solvent and the dispersant described above are blended in a suitable amount under mechanical stirring and mixing. In this step, a mixing method using a grinding medium, that is, a grinding method using a device commonly referred to as a ball mill, a vibration mill, a pearl mill, a grinding machine, or the like has been commonly used. However, the slurry production method of the present invention is characterized in that the alumina powder used as a raw material in the present invention undergoes less aggregation and has a uniform particle shape and particle size. Therefore, the alumina powder can be dispersed by ultrasonic irradiation from the outside using an ultrasonic bath or ultrasonically irradiated with an ultrasonic homogenizer to form a uniform slurry. Dispersion methods that do not use a medium such as ceramic balls are preferred in view of avoiding mixing of oxides or salts other than aluminum. As for the ultrasonic wave, the irradiation power is preferably 10 kHz or more, more preferably 25 kHz or more when the volume of the bath is 40 liters. The stirring and mixing time depends on the volume of the slurry. For example, when the amount of the slurry is 10 L, stirring and mixing are preferably performed for at least 30 minutes. The raw powder is sufficiently dispersed and then the organic binder is mixed thereto. For example, when the amount of slurry is 10 L, mixing is preferably performed for at least 1 hour. Even in the absence of ultrasonic irradiation, it is sufficient to perform mechanical agitation using a stirring blade.

The slurry prepared as described above may be suitably defoamed under reduced pressure. Moreover, various defoamers can also be used. In addition, according to the subsequent molding method, the viscosity can be adjusted within the range of 50 to 10000 mPa / s by addition of various pH adjusting agents and flocculants. For example, in granulation with a spray dryer, the viscosity of the alumina slurry is preferably adjusted within the range of 300 to 400 mPa / s by pH adjustment using aqueous hydrochloric acid solution, aqueous ammonia and the like for producing spherical granules. In addition, the alumina concentration in the slurry can be increased by standing sedimentation, centrifugation and vacuum concentration by rotary evaporator.

As the solvent, this depends on the type of binder used and the molding method. For the polyvinyl alcohol and acrylic binder used when the granules are produced by a spray dryer, water is most preferred. Various organic solvents may be used depending on the formulation. For example, a mixed solvent of toluene and butanol is preferable in doctor blade molding (also called tape casting).

As a dispersing agent, the ammonium salt of polycarboxylic acid [for example, brand name; SN-D5468, San Nopco Co., Ltd.] is mainly used when the solvent is water. For organic solvents, ethyl oleate, sorbitan monooleate, sorbitan trioleate, polycarboxylic acid series and the like are used. In the case of alumina raw material powder to be used as a raw material in the present invention, polyester series [trade name; TEXAPHOR 3012, manufactured by San Nopco co., Ltd., is preferred, but is not limited to these examples. Methods that do not use a dispersant may provide a slurry having a lower viscosity depending on the organic binder to be used together.

Examples of organic binders include, but are not limited to, polyvinyl alcohol, polyvinyl acetal, various acrylic polymers, methyl cellulose, polyvinyl acetate, polyvinyl butyral series, various waxes, and various polysaccharides.

The plasticizer depends on the organic binder to be used. Examples thereof include ethylene glycol, diethylene glycol, polyethylene glycol, glycerin, polyglycerine and various esters. In particular, when using an organic solvent, dibutyl phthalate, diethylhexyl phthalate and the like are used, but not limited to these examples.

In this invention, a mold release agent, a flocculant, and a pH adjuster can also be added as another additive. However, it is important that there are no inorganic impurities other than aluminum and additives in the solvent. It is most desirable for the form retention and processing of the green body to not add any organic material unless obstacles are present.

Examples of the molding method after drying the slurry include conventional methods such as slip casting, pressure slip casting, centrifugal casting, doctor blade molding, and extrusion molding. In addition, after the granules are produced by a spray dryer or various pellet makers, a dry molding method such as a pressurization method and a cold isostatic press can be used.

In the case of a cold isostatic press, the slurry is molded into granules by spray drying or the like. The resulting granules are preferably uniaxially pressed under pressure in the range of 50 to 500 kg / cm 2, more preferably under pressure in the range of 200 to 300 kg / cm 2. The product is then isotropically applied to a pressure in the range of 0.5 to 3t / cm 2, more preferably in the range of 0.8 to 1.5t / cm 2 by cold isostatic press. Next, the resulting green body is processed into the above-described form.

In addition, for example, in the case of a small green body having a size of 20 mm or less, the raw alumina powder may also be filled into the mold to perform a uniaxial press or cold isostatic press under the above pressure.

The green body obtained by the above method is subjected to the next step depending on its size. For example, in the case of a workpiece having a diameter of 300 mmФ and a thickness of 30 mmt, it is calcined at least 1 hour at a temperature in the range of 500 to 1000 ° C., preferably at least 3 hours at a temperature in the range of 800 to 900 ° C. to remove the organic material. do. The product is then sintered under an air atmosphere at a temperature in the range of 1400-1800 ° C. for at least 1 hour, preferably at least 3 hours. Specifically, when the size of the primary particles of the alumina raw material powder is 0.7 μm, the sintering temperature is preferably 1650 ° C. or more. When the size of a primary particle is 0.2 micrometer, 1450 degreeC or more is preferable for a sintering temperature.

Preferably the maximum pore diameter of the pores in the sintered compact obtained by this invention is 10 micrometers or less. The number of pores having a size of 1 µm or more and 10 µm or less is preferably 20 or less, more preferably 10 or less. A high combustion density of the alumina sintered body described above can be obtained. In the alumina sintered body of the present invention, due to the small number of pores, reduction of particles and less dissolution near the particles occur during use as a component of a semiconductor manufacturing system on a heat dissipation furnace, a plasma etching process or a CVD system. Moreover, the sintered compact of this invention has the outstanding corrosion resistance as an element which contacts a corrosive solution or gas. In addition, since a small number of defective pores exist, artificial ceramics, bioceramic elements such as artificial thigh heads, mechanical parts of bearings, thread guides, rolling rollers, pump parts, and the like, and frame rods and core tubes The present invention provides a product having high reliability in terms of strength and wear resistance as a component such as a shaft enclosing tube. In addition, since light scattering due to pores does not occur, decorative elements such as plates and cups having excellent surface smoothness can be provided.

Example

Hereinafter, the following is described as an example of the present invention, which is not to be construed as limiting the scope of the present invention.

Various measurements in the present invention were performed by the following method.

(1) Determination of the number average particle size of primary particles and D / H of primary particles

Photographs of powder particles are taken using a scanning electron microscope (SEM; manufactured by JEOL, Ltd., type T-300). 50-100 particles are selected from the photographs and their image analysis performed to determine the value as an average value.

(2) Measurement of D10 and D90 (measurement of weight cumulative particle size distribution (abbreviated as "particle size distribution"))

Measurement is made by laser diffraction scattering method using a master sizer (manufactured by Malvern Co.). Alumina slurry for measurement is prepared by the following method. That is, 25 g of 0.5% by weight aqueous sodium hexametaphosphate solution is added to 2.5 g of alumina powder. The resulting mixed solution is ultrasonically irradiated with a homogenizer for 2 minutes to prepare an alumina slurry.

(3) wet constitution

1 kg of distilled water is added to 1 kg of alumina. The resulting mixture was then irradiated with ultrasonic waves in a 6 L volume ultrasonic bath (frequency: 28 kHz, output: 200 W) for 30 minutes to prepare a slurry. In a beaker filled with distilled water, a 5 μm nylon mesh in the form of a bag is immersed. The total amount of the prepared alumina slurry is poured into the nylon bag. Next, the entire beaker is ultrasonically irradiated using an ultrasonic bath. This causes the alumina particles to pass through the nylon mesh and move into the beaker. After 20 minutes, the nylon mesh bag is pulled out and the outside of the bag is thoroughly cleaned and dried to measure the increase in weight. The increase in weight is divided by the 1 kg charge of alumina, and the value obtained is taken as the residual amount on the 5-μm sieve.

(4) Measurement of pore number and pore size on the polishing surface of the alumina sintered body

The pore number is measured as follows: That is, a photograph (magnification: 50 times) of the mirror polished surface of the sintered body is taken using an optical microscope (Olympus Optical Co., Ltd .; BH-2). The number of pores appearing as dark spots in the photograph is visually counted and converted into the number per mm 2. The alumina sintered body is first subjected to rough grinding using a # 800 diamond grinding wheel to make it flat. The mirror polishing is then performed using a 3-μm polycrystalline diamond slurry and a copper table polishing machine (high pressure lapping system; NIHON ENGIS Co.). The polishing is performed for 60 minutes or more while adjusting the surface pressure to 300 g / cm 2 or more during polishing. In order to remove scratches on the surface, a 1-μm polycrystalline diamond slurry is further polished for at least 30 minutes. For pores that are elliptical or amorphous rather than circular, the pore size is measured by taking the major axis of the pore's maximum diameter or diagonal as the pore size.

(6) Measurement of Combustion Density of Alumina Sintered Body

The burning density of the sintered compact is measured according to the Archimedes method.

(7) corrosion test

The corrosion test is measured as follows: the surface polished sintered body obtained by the above method is immersed in 80 ° C. nitric acid for 50 hours. Next, the pores on the surface are observed under a light microscope to measure an increase in the area of the pores with an image analysis device.

(8) Purity analysis (ICP-AES quantitative measurement method) of alumina sintered compact

The alumina sintered compact is pulverized in a boron nitride mortar, followed by alkali melting. The molten material is subjected to ICP radiation spectral analysis (ICP quantometer type SPS1200VR; manufactured by Seiko Electronic Industry Co., Ltd.).

Example 1

In the present Example 1, (alpha) alumina powder (brand name: SUMICORUNDUM AA04; manufacturer: Sumitomo Chemical Co., Ltd.) is used as a raw material. The alumina powder consists of polyhedral particles each having substantially no crushed surface and having 8 to 20 phases. It was found from the SEM photograph that its primary particle size was 0.4 μm. From the results of the particle size distribution measurement, D90 was found to be 1.48 μm, D10 was 0.31 μm, and D90 / D10 was 4.8. The residual amount of the sieve phase in the wet sieve was found to be 5 ppm.

5 kg of alumina powder AA04, 3 kg of water (solvent) and ammonium polycarboxylate as dispersant [San Nopco Co., Ltd .; Trade name: SN-D5468] 62.5 g of the mixture while stirring for 30 minutes while irradiating with ultrasound. Next, 750 g of a 10% by weight solution of polyvinyl alcohol as an organic binder (manufactured by Kuraray Corp .; trade name: PVA205c), 25 g of polyethylene glycol as a plasticizer (reagent; degree of polymerization 400) and a stearic acid emulsion as a lubricant [manufacturer: CHUKYO YUSHI Co. , Ltd .; 140 g of the trade name: CELOSOL 920) are added simultaneously in a total amount and then stirred and mixed for 60 minutes to form a slurry.

110 ml of 1N aqueous hydrochloric acid solution was added to the resulting slurry, and the viscosity was adjusted to 350 cP. The slurry thus prepared is spray dried with a spray dryer to prepare granules. The resulting granular powder is filled into a mold and then molded under a load of 1500 kg / cm 2 by a single screw press. This produces a columnar green body having a diameter of 200 mm and a height of 10 mm. The green body thus prepared is then removed with organic material at 900 ° C. for 3 hours and then sintered in air at 1650 ° C. for 2 hours.

The density of the sintered compact was found to be 3.974 g / cm 3. No pores larger than 10 μm were observed at all, and it was found that the number of pores each having a maximum diameter of 1 μm or more and 10 μm or less was 12 per mm 2 on the mirror polished surface of the sintered body.

In addition, the amount of impurities in the sintered body was found to be as follows: Fe: 5 ppm, Si: 5 ppm, Ca ≦ 1 ppm, Mg ≦ 1 ppm, Na ≦ 5 ppm and other elements: below the detection limit (less than 1 ppm) and elements other than Al Total amount: less than 50 ppm.

The pore occupation area after the corrosion test was found to be 0.02%.

Example 2

100 g of the alumina powder AA04 of Example 1, 60 g of water, and 1.3 g of the dispersant SN-D5468 were mixed with stirring for 30 minutes while irradiating with ultrasonic waves.

The resulting slurry was left to degas for 30 minutes under reduced pressure. In addition, a raw body having a width of 30 mm, a length of 50 mm, and a height of 5 mm is produced by slip casting using a plaster mold. The resulting green body is sintered at 1650 ° C. for 2 hours.

The density of the sintered compact was found to be 3.977 g / cm <3>. No pores larger than 10 μm were observed at all, and it was found that the number of pores each having a maximum diameter of 1 μm or more and 10 μm or less was 18 per mm 2 on the mirror polished surface of the sintered body.

In addition, the amount of impurities in the sintered body was found to be as follows: Fe: 9 ppm, Si: 5 ppm, Ca≤1 ppm, Mg≤1 ppm, Na≤5 ppm and other elements: below the detection limit (less than 1 ppm) and elements other than Al Total amount: less than 50 ppm.

The pore occupation area after the corrosion test was found to be 0.02%.

Example 3

In Example 3, α alumina powder (trade name: SUMICORUNDUM AA02; manufacturer: Sumitomo Chemical Co., Ltd.) is used as a raw material. The alumina powder consists of polyhedral particles each having substantially no crushed surface and having 8 to 20 phases. It was found from the SEM photograph that its primary particle size was 0.2 μm. From the results of the particle size distribution measurements, it was found that D90 was 1.08 μm, D10 was 0.18 μm, and D90 / D10 was 6.0. The residual amount of the sieve phase in the wet sieve was found to be 5 ppm.

Granules were prepared under the same conditions as in Example 1 except that alumina powder AA02 was used as a raw material. A cylindrical workpiece is prepared from granules under the same conditions as in Example 1. Next, the green body thus prepared is removed from the organic material at 900 ° C. for 3 hours and then sintered in air at 1550 ° C. for 2 hours.

The density of the sintered compact was found to be 3.975 g / cm 3. No pores larger than 10 μm were observed at all, and it was found that the number of pores each having a maximum diameter of 1 μm or more and 10 μm or less was 15 per mm 2 on the mirror polished surface of the sintered body.

In addition, the amount of impurities in the sintered body was found to be as follows: Fe: 6ppm, Si: 9ppm, Ca≤1ppm, Mg≤1ppm, Na≤5ppm and other elements: less than the detection limit (less than 1ppm) and elements other than Al Total amount: less than 50 ppm.

The pore occupation area after the corrosion test was found to be 0.02%.

Example 4

In Example 4, α alumina powder (trade name: SUMICORUNDUM AA03; manufacturer: Sumitomo Chemical Co., Ltd.) is used as a raw material. The alumina powder consists of polyhedral particles each having substantially no crushed surface and having 8 to 20 phases. It was found from the SEM photograph that its primary particle size was 0.33 μm. From the results of particle size distribution measurements, it was found that D90 was 1.38 μm, D10 was 0.26 μm, and D90 / D10 was 5.0. The residual amount of the sieve phase in the wet sieve was found to be 10 ppm.

An alumina powder having a primary particle size of 0.33 μm is charged into a mold and then molded under a load of 200 kg / cm 2 by a single screw press. This produces a columnar green body having a diameter of 200 mm and a height of 10 mm. Next, the green body thus prepared is subjected to a cold isostatic press under a pressure of 1.0 t / cm 2. The green body is degreased at 900 ° C. for 3 hours and then sintered in the air at 1600 ° C. for 2 hours.

The density of the sintered compact was found to be 3.980 g / cm <3>. No pores larger than 10 μm were observed at all, and it was found that the number of pores each having a maximum diameter of 1 μm or more and 10 μm or less was 5 per mm 2 on the mirror polished surface of the sintered body.

In addition, the amount of impurities in the sintered body was found to be as follows: Si: 8 ppm, Na≤5 ppm and other elements: less than the detection limit (less than 1 ppm) and the total amount of elements other than Al: less than 50 ppm.

The pore occupation area after the corrosion test was found to be 0.01%.

Example 5

In Example 5, α alumina powder (trade name: SUMICORUNDUM AA07; manufacturer: Sumitomo Chemical Co., Ltd.) is used as a raw material. The alumina powder consists of polyhedral particles each having substantially no crushed surface and having 8 to 20 phases. It was found from the SEM photograph that its primary particle size was 0.7 μm. From the results of the particle size distribution measurement, it was found that D90 was 2.08 μm, D10 was 0.57 μm and D90 / D10 was 3.6. The residual amount of the sieve phase in the wet sieve was found to be 4 ppm.

5 kg of alumina powder AA07, 3 kg of water, and 62.5 g of SN-D5468, a dispersant, are mixed with stirring for 30 minutes while irradiating with ultrasound. Next, 250 g of a 40% by weight solution of an acrylic emulsion as an organic binder (manufactured by Dainippon Ink & Chemicals Inc .; trade name: BONCOAT3981) and 140 g of CELOSOL 920 as a lubricant were simultaneously added in a total amount, followed by stirring and mixing for 60 minutes, and then a slurry. Creates.

Granules and shaped bodies were prepared under the same conditions as in Example 1, except that the resulting slurry was used. The green body is then removed with organic material at 900 ° C. for 3 hours and then sintered in air at 1750 ° C. for 2 hours.

The density of the sintered compact was found to be 3.971 g / cm 3. No pores larger than 10 μm were observed at all, and it was found that the number of pores each having a maximum diameter of 1 μm or more and 10 μm or less was 15 per mm 2 on the mirror polished surface of the sintered body.

In addition, the amount of impurities in the sintered body was found to be as follows: Fe: 10 ppm, Na≤5 ppm and other elements: less than the detection limit (less than 1 ppm) and the total amount of elements other than Al: less than 50 ppm. The pore occupation area after the corrosion test was found to be 0.02%.

Example 6

In the process of preparing the slurry of Example 4, 6.4 g (200 ppm in terms of MgO) of magnesium nitrate hexahydrate (reagent grade) were added as a sintering agent. Granules and a green body were manufactured under the same conditions as in Example 4. The green body is then removed from the organic material at 900 ° C. for 3 hours and then sintered in air at 1550 ° C. for 2 hours.

The density of the sintered compact was found to be 3.984 g / cm 3. No pores larger than 10 µm were observed at all, and it was found that the number of pores each having a maximum diameter of 1 µm or more and 10 µm or less was 7 per mm 2 on the mirror polished surface of the sintered body.

The pore occupation area after the corrosion test was found to be 0.02%.

In addition, the amount of impurities in the sintered body was found to be as follows: Fe: 5 ppm, Si: 5 ppm, Ca ≦ 1 ppm, Mg: 125 ppm, Na ≦ 5 ppm and other elements: below the detection limit (less than 5 ppm) and elements other than Al Total amount: less than 170 ppm.

Example 7

In the process for preparing the slurry of Example 1, 16.0 g (500 ppm in terms of MgO) of magnesium nitrate hexahydrate (reagent grade) were added as a sintering agent. Granules and a green body were manufactured under the same conditions as in Example 1. The green body is then removed with organic material at 900 ° C. for 3 hours and then sintered in air at 1600 ° C. for 2 hours.

The density of the sintered compact was found to be 3.982 g / cm 3. No pores larger than 10 μm were observed at all, and it was found that the number of pores each having a maximum diameter of 1 μm or more and 10 μm or less was 4 per mm 2 on the mirror polished surface of the sintered body.

The pore occupation area after the corrosion test was found to be 0.01%.

In addition, the amount of impurities in the sintered body was found to be as follows: Fe: 9 ppm, Si: 8 ppm, Ca≤1 ppm, Mg: 305 ppm, Na≤5 ppm and other elements: below the detection limit (less than 1 ppm) and elements other than Al Total amount: less than 350 ppm.

Example 8

In the process for preparing the slurry of Example 3, 1.6 g (50 ppm in terms of MgO) of magnesium nitrate hexahydrate (reagent grade) were added as a sintering agent. Granules and green bodies were prepared under the same conditions as in Example 3. The green body is then removed with organic material at 900 ° C. for 3 hours and then sintered in air at 1600 ° C. for 2 hours.

The density of the sintered compact was found to be 3.982 g / cm 3. No pores larger than 10 μm were observed at all, and it was found that the number of pores each having a maximum diameter of 1 μm or more and 10 μm or less was 5 per mm 2 on the mirror polished surface of the sintered body.

The pore occupation area after the corrosion test was found to be 0.01%.

In addition, the amount of impurities in the sintered body was found to be as follows: Fe: 9 ppm, Si: 8 ppm, Ca≤1 ppm, Mg: 25 ppm, Na≤5 ppm and other elements: below the detection limit (less than 1 ppm) and elements other than Al Total amount: less than 50 ppm.

Example 9 (slip casting)

100 g of alumina powder AA04 of Example 1, 60 g of water, 1.3 g of dispersant SN-D5468 and 0.01 g of MgO (manufactured by Ube Material Co., Ltd .; trade name: 500A) are mixed with stirring for 30 minutes while irradiating with ultrasonic waves. . MgO is poured into the gypsum mold in about 1/2 the amount during slip casting, and then MgO is added in an amount of 1000 ppm corresponding to twice the amount of MgO added.

The resulting slurry was left to degas for 30 minutes under reduced pressure. In addition, a raw body having a width of 30 mm, a length of 50 mm, and a height of 5 mm is produced by slip casting using a plaster mold. The resulting green body is sintered at 1600 ° C. for 2 hours.

The density of the sintered compact was found to be 3.983 g / cm 3. No pores larger than 10 μm were observed at all, and it was found that the number of pores each having a maximum diameter of 1 μm or more and 10 μm or less was 4 per mm 2 on the mirror polished surface of the sintered body.

The pore occupation area after the corrosion test was found to be 0.02%.

In addition, the amount of impurities in the sintered body was found to be as follows: Fe: 5 ppm, Si: 12 ppm, Ca: 5 ppm, Mg: 305 ppm, Na≤5 ppm and other elements: below the detection limit (less than 5 ppm) and elements other than Al Total amount: less than 350 ppm.

Example 10

In the process of preparing the slurry of Example 7, granules were prepared by changing the amount of magnesium nitrate hexahydrate to be added as a sintering agent to 32.0 g (1000 ppm in terms of MgO). Next, a green body and also a sintered body were produced in the same manner as in Example 7.

The density of the sintered compact was found to be 3.980 g / cm <3>. No pores larger than 10 μm were observed at all, and it was found that the number of pores each having a maximum diameter of 1 μm or more and 10 μm or less was 5 per mm 2 on the mirror polished surface of the sintered body.

The pore occupation area after the corrosion test was found to be 0.01%.

In addition, the amount of impurities in the sintered body was found to be as follows: Fe: 5 ppm, Si: 8 ppm, Ca≤1 ppm, Mg: 600 ppm, Na≤5 ppm and other elements: below the detection limit (less than 5 ppm) and elements other than Al Total amount: less than 650 ppm.

Example 11 (Doctor Blate Molding Method Also Called Tape Casting)

In Example 11, α alumina powder (trade name: SUMICORUNDUM AA05; manufacturer: Sumitomo Chemical Co., Ltd.) is used as a raw material. The alumina powder consists of polyhedral particles each having substantially no crushed surface and having 8 to 20 phases. It was found from the SEM photograph that its primary particle size was 0.5 μm. From the results of the particle size distribution measurement, it was found that D90 / D10 was 4.5. The residual amount of the sieve phase in the wet sieve was found to be 3 ppm.

500 g AA05, 0.25 g MgO, 308 g toluene, 90 g ethanol, 43 g cyclohexanone and 10 g polyester dispersant (San Nopco Co., Ltd .; TEXAPHOR 3112) are mixed for 16 hours in a ball mill. In addition, 36 g of polyvinyl butyral (manufactured by Sekisui Chemical Co., Ltd .; trade name: BL-S) and 18 g of dibutyl phthalate are added and mixed in a ball mill for 6 hours to obtain a homogeneous slurry. The viscosity of the slurry is adjusted by solvent removal and then film molded according to the doctor blade molding method.

The resulting film is air dried at room temperature for 96 hours and then cut into pieces each having the size described above. The resulting pieces are fired in an electric furnace under an air atmosphere. The calcined body is then degreased at 500 ° C. for 1 hour and then sintered in air at 1550 ° C. for 1 hour.

The density of the sintered compact was found to be 3.982 g / cm 3. No pores larger than 10 µm were observed at all, and it was found that the number of pores each having a maximum diameter of 1 µm or more and 10 µm or less was 6 per mm 2 on the mirror polished surface of the sintered body.

The pore occupation area after the corrosion test was found to be 0.02%.

In addition, the amount of impurities in the sintered body was found to be as follows: Fe: 5 ppm, Si: 8 ppm, Ca ≦ 1 ppm, Mg: 305 ppm, Na ≦ 5 ppm and other elements: below the detection limit (less than 1 ppm) and elements other than Al Total amount: less than 350 ppm.

Example 12

In the process of preparing the slurry of Example 5, 3.6 g (100 ppm in terms of MgO) of magnesium nitrate hexahydrate (reagent grade) were added as a sintering agent to prepare a slurry. Granules and the green body were prepared in the same manner as in Example 5. The green body is then removed from the organic material at 900 ° C. for 3 hours and then sintered in air at 1700 ° C. for 2 hours.

The density of the sintered compact was found to be 3.980 g / cm <3>. No pores larger than 10 µm were observed at all, and it was found that the number of pores each having a maximum diameter of 1 µm or more and 10 µm or less was 6 per mm 2 on the mirror polished surface of the sintered body.

The pore occupation area after the corrosion test was found to be 0.01%.

In addition, the amount of impurities in the sintered body was found to be as follows: Fe: 5 ppm, Na ≦ 5 ppm, Mg: 60 ppm and other elements: below the detection limit (less than 1 ppm) and the total amount of elements other than Al: below 110 ppm.

Example 13

A green body and a sintered body were prepared in the same manner as in Example 7, except that the amount of magnesium nitrate hexahydrate to be added as a sintering agent was changed to 3.6 g (50 ppm in terms of MgO) to prepare granules.

The density of the sintered compact was found to be 3.981 g / cm 3. No pores larger than 10 µm were observed at all, and it was found that the number of pores each having a maximum diameter of 1 µm or more and 10 µm or less was 7 per mm 2 on the mirror polished surface of the sintered body.

The pore occupation area after the corrosion test was found to be 0.01%.

In addition, the amount of impurities in the sintered body was found to be as follows: Fe: 5 ppm, Si: 8 ppm, Ca ≦ 1 ppm, Mg: 35 ppm, Na ≦ 5 ppm and other elements: below the detection limit (less than 1 ppm) and elements other than Al Total amount: less than 80 ppm.

Example 14

A green body and a sintered body were prepared in the same manner as in Example 7, except that the amount of magnesium nitrate hexahydrate to be added as a sintering agent was changed to 1.8 g (25 ppm in terms of MgO) to prepare granules.

The density of the sintered compact was found to be 3.982 g / cm 3. No pores larger than 10 μm were observed at all, and it was found that the number of pores each having a maximum diameter of 1 μm or more and 10 μm or less was 4 per mm 2 on the mirror polished surface of the sintered body.

The pore occupation area after the corrosion test was found to be 0.01%.

In addition, the amount of impurities in the sintered body was found to be as follows: Fe: 5 ppm, Si: 8 ppm, Ca≤1 ppm, Mg: 20 ppm, Na≤5 ppm and other elements: less than the detection limit (less than 1 ppm) and elements other than Al Total amount: less than 70 ppm.

Comparative Example 1 (slip casting)

In Comparative Example 1, alumina raw material powder having a purity of 99.99% by weight and a primary particle size of 0.3 μm was manufactured by Showa Denko K. K .; UA5055]. The primary particles of the alumina powder are amorphous particles that are not polyhedral. D / H was found to be greater than 2. From observation of the particles by tunnel electron microscopy, the particles were found to have a number of defects in the particles. From the results of particle size distribution measurements, it was found that D90 was 2.55 μm, D10 was 0.44 μm and D90 / D10 was 5.8. The residual amount of the sieve phase in the wet sieve was found to be 120 ppm.

100 g of alumina powder, 60 g of water and 1.3 g of dispersant SN-D5468 are mixed with stirring for 30 minutes while irradiating with ultrasonic waves. Using the resulting slurry, molding and sintering were carried out under the same conditions as in Example 2.

The density of the sintered compact was found to be 3.935 g / cm 3. 65 pores each having a size larger than 10 mu m per square millimeter and countless pores having a maximum diameter of 10 mu m or less were observed on the mirror polished surface of the sintered body.

Comparative Example 2

5 kg of alumina powder UA5055 of Comparative Example 1, 3 kg of water and 65 g of dispersant SN-D5468 were irradiated with ultrasonic waves and mixed with stirring for 30 minutes. The resulting slurry is subjected to a ball mill treatment with 2 mm Alumina balls. The ball milling time is set to 2 hours. In addition, 1000 g of PVA205c 10% by weight solution as the organic binder and the lubricant Cellosol 920 are added simultaneously in total amounts, followed by stirring and mixing for 60 minutes. This produces a slurry.

The resulting slurry was used to produce granules and a green body under the same conditions as in Example 1. Next, the green body is sintered under the same conditions as in Example 1.

The density of the sintered compact was found to be 3.945 g / cm 3. Fifty pores each size larger than 10 mu m are observed on the mirror polished surface of the sintered body, with 50 pores per mm 2 and a respective maximum diameter of 10 mu m or less.

Comparative Example 3

5 g of the alumina powder UA5055 of Comparative Example 1 was filled into a mold and then molded under a load of 300 kg / cm 2 by a single screw press. This produces a cylindrical green body having a diameter of 20 mm and a height of 10 mm. Next, the green body thus prepared is subjected to a cold isostatic press under a pressure of 3.0 t / cm 2. The obtained green body is degreased at 900 ° C. for 3 hours and then sintered in air at 1750 ° C. for 2 hours.

The density of the sintered compact was found to be 3.950 g / cm 3. 35 pores each mm larger than 10 mu m per square millimeter and countless pores each having a maximum diameter of 10 mu m or less were observed on the mirror polished surface of the sintered body.

Comparative Example 4

Granules and a green body were produced in the same manner as in Example 7, except that the alumina powder UA5055 of Comparative Example 1 was used as a raw material. Sintering is then performed at 1550 ° C. for 2 hours.

The density of the sintered compact was found to be 3.972 g / cm <3>. Thirty-four pores of each size larger than 10 mu m are observed on the mirror polished surface of the sintered body with 34 pores per mm 2 and a maximum diameter of 10 mu m or less each.

The pore occupation area after the corrosion test was found to be 0.5%.

Comparative Example 5

In this comparative example 5, (alpha) alumina powder (brand name: SUMICORUNDUM AA2; manufacturer: Sumitomo Chemical Co., Ltd.) is used as a raw material. The alumina powder consists of polyhedral particles each having substantially no crushed surface and having 8 to 20 phases. It was found from the SEM photograph that its primary particle size was 2 μm. From the results of the particle size distribution measurement, it was found that D90 was 2.08 μm, D10 was 0.57 μm and D90 / D10 was 3.6. The residual amount of the sieve phase in the wet sieve was found to be 50 ppm. Granules and a green body were prepared in the same manner as in Example 7 using the alumina powder of this comparative example, followed by sintering at 1700 ° C. for 2 hours.

The density of the sintered compact was found to be 3.900 g / cm <3>. 46 pores of each size larger than 10 mu m per square millimeter and countless pores each having a maximum diameter of 10 mu m or less are observed on the mirror polished surface of the sintered body.

The pore occupation area after the corrosion test was found to be 0.7%.

Comparative Example 6

The alumina powder AA04 of Example 1 is heat treated at 1400 ° C. The primary particles of the alumina are polyhedrons, which aggregate by heat treatment. The D90 / D10 of the particle size distribution was found to be 10.

The residual amount of the sieve phase in the wet sieve was found to be 209 ppm. Granules, green bodies, and sintered bodies were produced in the same manner as in Example 7, except that the alumina powder of this comparative example was used as a raw material.

The density of the sintered compact was found to be 3.900 g / cm <3>. 69 pores of each size larger than 10 mu m are observed on the mirror polished surface of the sintered body, with 69 pores per mm 2 and a respective maximum diameter of 10 mu m or less.

The pore occupation area after the corrosion test was found to be 0.9%.

Comparative Example 7

In Comparative Example 7, Bayer processed alumina powder having a purity of 99.99% by weight and a primary particle size of 0.6 µm was used as a raw material. The primary particles of the alumina powder are amorphous particles that are not polyhedral. D / H was found to be greater than 3. As a particle size distribution, D90 / D10 was found to be 6.6. The residual amount of the sieve phase in the wet sieve was found to be 790 ppm. Granules, green bodies, and sintered bodies were produced in the same manner as in Example 7, except that the alumina powder of this comparative example was used as a raw material.

The density of the sintered compact was found to be 3.870 g / cm 3. A number of pores each larger than 10 μm are observed on the mirror polished surface.

The pore occupation area after the corrosion test was found to be 2.1%.

Comparative Example 8

In this comparative example 8, the organoaluminum compound was hydrolyzed to produce aluminum hydrate, followed by sintering at 1000 ° C. The resulting alumina powder with a purity of 99.99% by weight and a primary particle size of 0.5 μm is used as raw material. The primary particles of the alumina powder are amorphous particles that are not polyhedral. D / H was found to be at least 5. As cumulative particle size distribution of the alumina powder, D90 / D10 was found to be 5.8. Wet constitution is impossible. Granules, green bodies, and sintered bodies were produced in the same manner as in Example 7, except that the alumina powder of this comparative example was used as a raw material.

The density of the sintered compact was found to be 3.800 g / cm 3. Countless pores each larger than 10 μm are observed on the mirror polished surface.

The pore occupation area after the corrosion test was found to be 2.3%.

The above examples and comparative examples suggest the following facts:

(1) When the above-mentioned alumina particles are used as a raw material, a high density and high purity alumina sintered body having very few pores can be produced by a dispersion method that does not use a grinding medium.

(2) When alumina particles other than those described above are used as raw materials in the present invention, a high density and high purity alumina sintered body having extremely few pores cannot be produced by a dispersion method that does not use a grinding medium. Even when the molding pressure and the sintering temperature are increased, the desired alumina sintered body cannot be produced (Comparative Examples 1, 2, 4, 7 and 8).

(3) When alumina particles other than those described above are used as raw materials in the present invention, a high density and high purity alumina sintered body having extremely few pores cannot be produced even by a dispersion method using a grinding medium (Comparative Example 3) .

(4) Even in the case of using the alumina particles of the form described above in the present invention, when the particle size is large (Comparative Example 5) and when the particle size distribution is wide and contains a large number of coarse particles (Comparative Example 6) High density and high purity alumina sintered bodies having few pores cannot be produced.

Alumina water Primary particles D90 / D10 shape D / H > 10 μm Sintering agent Amount % Μm ppm ppm Example 1 AA04 99.99 0.40 4.8 Polyhedron One 5 Example 2 AA04 99.99 0.40 4.8 Polyhedron One 5 Example 3 AA02 99.99 0.20 6.0 Polyhedron One 15 Example 4 AA03 99.99 0.30 5.0 Polyhedron One 10 Example 5 AA07 99.99 0.70 3.6 Polyhedron One 4 Example 6 AA03 99.99 0.30 5.0 Polyhedron One 10 Magnesium nitrate 200 Example 7 AA04 99.99 0.40 4.8 Polyhedron One 5 Magnesium nitrate 500 Example 8 AA02 99.99 0.20 6.0 Polyhedron One 5 Magnesium nitrate 50 Example 9 AA04 99.99 0.40 4.8 Polyhedron One 5 magnesia 500 Example 10 AA04 99.99 0.40 4.8 Polyhedron One 5 Magnesium nitrate 1000 Example 11 AA05 99.99 0.50 4.5 Polyhedron One 3 magnesia 500 Example 12 AA07 99.99 0.70 3.6 Polyhedron One 4 Magnesium nitrate 100 Example 13 AA04 99.99 0.40 4.8 Polyhedron One 5 Magnesium nitrate 50 Example 14 AA04 99.99 0.40 4.8 Polyhedron One 5 Magnesium nitrate 25 Comparative Example 1 UA5055 99.99 0.30 5.8 Heterogeneity 2 120 Comparative Example 2 UA5055 99.99 0.30 5.8 Heterogeneity 2 120 Comparative Example 3 UA5055 99.99 0.30 5.8 Heterogeneity 2 120 Comparative Example 4 UA5055 99.99 0.30 5.8 Heterogeneity 2 120 Magnesium nitrate 500 Comparative Example 5 AA2 99.99 2.00 3.0 Polyhedron One 50 Magnesium nitrate 500 Comparative Example 6 AA04 99.99 0.40 10.0 Polyhedron One 209 Magnesium nitrate 500 Comparative Example 7 Bayer 99.50 0.60 6.6 Heterogeneity 3 790 Magnesium nitrate 500 Comparative Example 8 Particulate alumina 99.99 0.05 3.0 Heterogeneity 5 Infiltration Magnesium nitrate 500

Molding method Sintering Temperature Density of Sintered Body Purity of Sintered Body Handwork Handwork Corrosion test Corrosion Work Area Post-corrosion work area ℃ g / cm 3 Alumina% ≤10 μm ≥10 μm % % Example 1 Press molding 1650 3.974 99.99 12 0 ○ ≤0.01 0.02 Example 2 Slip press molding 1650 3.977 99.99 18 0 ○ ≤0.01 0.02 Example 3 Press molding 1550 3.975 99.99 15 0 ○ ≤0.01 0.02 Example 4 Press molding 1600 3.980 99.99 5 0 ○ ≤0.01 0.01 Example 5 Press molding 1750 3.871 99.99 15 0 ○ ≤0.01 0.02 Example 6 Press molding 1550 3.984 99.98 7 0 ○ ≤0.01 0.02 Example 7 Press molding 1600 3.982 99.95 4 0 ○ ≤0.01 0.01 Example 8 Press molding 1600 3.982 99.99 5 0 ○ ≤0.01 0.01 Example 9 Slip press molding 1600 3.983 99.99 4 0 ○ ≤0.01 0.02 Example 10 Press molding 1600 3.980 99.90 5 0 ○ ≤0.01 0.01 Example 11 Tape molding 1550 3.982 99.95 6 0 ○ ≤0.01 0.02 Example 12 Press molding 1700 3.980 99.99 6 0 ○ ≤0.01 0.01 Example 13 Press molding 1600 3.981 99.99 7 0 ○ ≤0.01 0.01 Example 14 Press molding 1600 3.982 99.99 4 0 ○ ≤0.01 0.01 Comparative Example 1 Slip press molding 1600 3.935 99.99 many 65 × 0.08 0.5 Comparative Example 2 Press molding 1650 3.945 99.99 many 50 × 0.11 0.7 Comparative Example 3 Press molding 1750 3.950 99.99 many 35 × 0.15 0.9 Comparative Example 4 Press molding 1550 3.972 99.95 many 34 × 0.08 0.5 Comparative Example 5 Press molding 1700 3.900 99.95 many 46 × 0.11 0.7 Comparative Example 6 Press molding 1600 3.900 99.95 many 69 × 0.15 0.9 Comparative Example 7 Press molding 1600 3.870 99.50 many many × 0.17 2.1 Comparative Example 8 Press molding 1500 3.800 99.95 many many × 0.2 2.3

The present invention contains an extremely small amount of impurities and pores, so that the following items are required, i.e. devices which require corrosion resistance in contact with corrosive solutions, gases, etc., for example, incorporation of other metal elements and dust particles in the semiconductor industry, etc. For products that require the prevention of adhesion or adsorption of metals (eg, vacuum chucks, vacuum tweezers and hands for use in operations involving cleaning, moving and surface processing of silicon wafers, and additionally for products such as abrasives for magnetic materials) material); Or alumina sintered bodies suitable for materials for products requiring prevention of pore presence itself (eg materials for hard disk substrates and magnetic head substrates, materials for various industrial mirrors and materials for dummy wafers) can do. Further, the small amount of pores, i.e., defects, can provide products having high reliability in terms of strength and wear resistance as bioceramic elements and various component parts. In addition, since light scattering due to pores does not occur, decorative elements such as plates and cups having excellent surface smoothness can be provided.

Claims (12)

A polyhedral particle having a substantially unbroken surface, the D / H ratio (where D is the maximum particle diameter horizontal to the hexagonal lattice plane of the hexagonal dense lattice of α alumina, and H is the hexagonal dense lattice of α alumina). The maximum particle diameter perpendicular to the hexagonal lattice plane) is 0.5 or more and 3.0 or less; The number average particle size is 0.1 µm or more and 1.0 µm or less; Comprising α alumina particles in the form of polyhedron with a D90 / D10 ratio (where D10 and D90 are respectively 10% cumulative diameter from the smallest particle face and 90% cumulative diameter in the cumulative particle size distribution) , Alumina powder having a purity of 99.99% by weight or more is applied to ultrasonic irradiation while applying to mechanical stirring without using a grinding medium, or applied to ultrasonic irradiation and then to mechanical stirring without using a grinding medium to disperse it in a solvent. Producing a prepared slurry; Drying and molding the slurry to prepare a green body; And Sintering the green body under an air atmosphere at a temperature in the range of 1400 ° C. to 1800 ° C., to produce a polycrystalline alumina sintered body. The alumina powder to which the sintering agent is applied is subjected to ultrasonic irradiation while applying to mechanical stirring without using the grinding medium, or to ultrasonic irradiation and then to mechanical stirring without using the grinding medium. A method of producing a slurry dispersed in a solvent. The method of claim 1, wherein the maximum diameter of the pores in the polycrystalline alumina sintered compact is 10 µm or less, the number of particles having 1 µm or more and 10 µm or less per mm 2 is 20 or less, the alumina purity is 99.99% by weight or more, The density is at least 3.970 g / cm 3. The method of claim 2, wherein the maximum diameter of the pores in the polycrystalline alumina sintered compact is 10 µm or less, the number of particles having 1 µm or more and 10 µm or less per mm 2 is 10 or less, the alumina purity is 99.99% by weight or more, The density is at least 3.975 g / cm 3. The method according to claim 2, wherein the sintering agent is added to the alumina powder in an amount of 10 ppm or more and 2000 ppm or less in terms of oxide. The method according to claim 2, wherein the sintering agent is added to the alumina powder in an amount of 10 ppm or more and 70 ppm or less in terms of oxide. The method of claim 2 wherein the sintering agent is at least one compound selected from the group consisting of alkaline earth metal compounds and silicon compounds. The method of claim 2 wherein the sintering agent is a magnesium compound. The device element for manufacturing a semiconductor obtained from the alumina sintered body according to claim 1. A bioceramic obtained from the alumina sintered body according to claim 1. Device for manufacturing a semiconductor obtained from the alumina sintered body according to claim 2. Bioceramic obtained from the alumina sintered body according to claim 2.