JP7022817B2 - Ceramic structure - Google Patents

Description

The present disclosure relates to ceramic structures.

In recent years, with the increase in size of manufacturing devices such as liquid crystals and semiconductors and precision measuring devices, the size of ceramic structures used for these devices, for example, supporting members of substrates has also been increased. As the enlarged support member, a long ceramic member having a length of 2 m or more in the longitudinal direction or a large ceramic member having a diameter of 1 m or more may be used.

As a method for manufacturing such a ceramic structure, in Patent Document 1, a cylindrical rubber mold is filled with a ceramic raw material, tension is applied in the longitudinal direction of the rubber mold, and static pressure pressing is performed while maintaining this state. A method has been proposed. On the other hand, according to Non-Patent Document 1, the ceramic molded body obtained by filling a rubber mold with a ceramic raw material and pressurizing it has an aggregate of powder inside, so that the pressure is uniformly transmitted from the outer surface 1 It is described that it is up to a position of up to 2 cm, and in a thick substrate, non-uniformity appears toward the inside.

Japanese Unexamined Patent Publication No. 4-27503

"Introduction to Fine Ceramics Manufacturing Technology" (Technique Hall Publishing Co., Ltd., May 25, 1984, p.187-188

As the ceramic compact becomes longer or larger, the non-uniformity is further increased. Therefore, the density of the ceramic structure obtained by firing such a ceramic molded body is significantly lower than that of the outer surface even in a portion where the depth from the outer surface is shallow. As a result, there may be parts with low mechanical properties such as strength and rigidity. The present disclosure provides a ceramic structure in which a portion having low mechanical properties is unlikely to be present even if the ceramic molded body is long or large.

In the observation image of the cross section of the present disclosure, the area occupancy of the pores in the surface layer region of 0.7 mm or less in the depth direction from the surface is A (%), and 0.7 mm in the depth direction from the surface. When the area occupancy of the pores in the deep internal region is B (%), B is larger than A, the ratio B / A is 1.5 or less, and the observation image is observed in both the surface layer region and the internal region. The value obtained by subtracting the average value of the circle-equivalent diameters of the pores from the average value of the distance between the centers of gravity of the pores is 5 μm or more and 10 μm or less .

According to the present disclosure, it is possible to provide a ceramic structure in which a portion having low mechanical properties is less likely to be present.

It is a perspective view which shows an example of the ceramic structure of this disclosure. It is a perspective view which shows the other example of the ceramic structure of this disclosure. It is a cross section of the ceramic structure shown in FIG. 1, (a) is an example of an observation image of a cross section in a surface layer region, and (b) is an example of an observation image of a cross section in an internal region near the surface layer region. (C) is an example of an observation image of a cross section in an internal region far from the surface layer region.

Hereinafter, the ceramic structure of the present disclosure will be described in detail with reference to the drawings. FIG. 1 is a perspective view showing an example of the ceramic structure of the present disclosure. FIG. 2 is a perspective view showing another example of the ceramic structure of the present disclosure.

The ceramic structure 10 shown in FIG. 1 has a long shape, and is, for example, 2 m to 4 m in length, 200 mm to 300 mm in width, and 20 mm to 80 mm in height. The ceramic structure 20 shown in FIG. 2 has a large disk shape, and has, for example, a diameter of 2 m to 4 m and a height of 20 mm to 80 mm. The ceramic structures 10 and 20 are all dense bodies having a relative density of 95% or more, and have surface layer regions 3 and 4 having a relative density of 0.7 mm or less in the depth direction from the surfaces 1 and 2 and surface regions 3 and 4 in the depth direction from the surface. It has an internal region 5 deeper than 0.7 mm.

The ceramic structures 10 and 20 are, for example, aluminum oxide, yttrium oxide, yttrium aluminum garnet, zirconium oxide, aluminum nitride, cordierite, aluminum titanate, mulite, alkali metal aluminosilicate (for example, LAS (lithium aluminum silicate)). Etc.), silicon carbide, silicon nitride or ceramics containing sialon as the main component.

The main component in the ceramic structures 10 and 20 means a component that occupies 80% by mass or more of the 100% by mass of the components constituting the ceramic structures 10 and 20. After identifying the content of each component constituting the ceramic structures 10 and 20 from the measurement results by an X-ray diffractometer using CuKα rays, an ICP (Inductively Coupled Plasma) emission spectroscopic analyzer or a fluorescent X-ray analyzer ( The content of the element may be determined using XRF) and converted into the content of the identified component. The relative density is expressed as a percentage (ratio) of the apparent density of the ceramic structures 10 and 20 determined in accordance with JIS R 1634-1998 with respect to the theoretical density of the identified main component ceramic structures 10 and 20. To.

FIG. 3 is a cross section of the ceramic structure shown in FIG. 1, FIG. 3A is an example of an observation image of the cross section in the surface layer region, and FIG. 3B is a cross section in the internal region on the side close to the surface layer region. 3 (c) is an example of an observation image of a cross section in an internal region far from the surface layer region.

As shown in FIG. 3A, pores 6 are arranged in the surface layer region 3 and pores 7 are dispersed in the inner region 5 as shown in FIGS. 3B and 3C. When the area occupancy of the pores 6 in the surface layer region 3 is A (%) and the area occupancy of the pores 7 in the internal region 5 is B (%), in the example shown in FIG. 3A, the area occupancy is A. Is 3.12%. The area occupancy rate B (%) of the pores 7 in the inner region 5 on the side close to the surface layer region 3 (hereinafter, this area occupancy rate B (%) is referred to as an area occupancy rate B ₁ (%)) is 3.46%. Is. The area occupancy rate B (%) of the pores 7 in the inner region 5 far from the surface layer region 3 (hereinafter, this area occupancy rate B (%) is referred to as an area occupancy rate B ₂ (%)) is 4.16%. Is.

In the observation image of the cross section of the ceramic structure of the present disclosure, the ratio B / A is 1.5 or less. When the ratio B / A is in this range, there are few voids in the internal region 5 that deteriorate mechanical properties such as strength and rigidity. Therefore, there are few parts lacking in mechanical properties, and it has high mechanical properties. In particular, the ratio B / A is preferably 1.4 or less.

In the example shown in FIG. 3, the ratio B ₁ / A is 1.1 and the ratio B ₂ / A is 1.3. The cross section of the ceramic structure is a polished surface obtained by polishing from the surface layer region of the ceramic structure toward the internal region. FIG. 3A is a position 0.7 mm in the depth direction from the surface 1, FIG. 3B is a position 7.5 mm in the depth direction from the surface 1, and FIG. 3C is a position 15 mm in the depth direction from the surface 1. It is a polished surface in.

These polished surfaces are polished on a cast iron surface plate using diamond abrasive grains having an average particle size D ₅₀ of 4 μm or more, and then on a tin surface plate using diamond abrasive grains having an average particle size D ₅₀ of 2 μm or more. It is obtained by polishing to 0.7 mm, 7.5 mm and 15 mm in the depth direction, respectively. The arithmetic mean roughness Ra of these polished surfaces is, for example, 5 nm or less. The arithmetic mean roughness Ra may be measured using a 3D optical surface profiler "NEW VIEW" (registered trademark Zygo Corporation).

In the ceramic structure, the value obtained by subtracting the average value of the equivalent circle diameter of the pores 6 (7) from the average value of the distance between the centers of gravity of the pores 6 (7) is 5 μm in any of the surface layer regions 3, 4 and the internal region 5. It may be 10 μm or more and 10 μm or less. When the value obtained by subtracting the average value of the equivalent circle diameters of the pores 6 (7) from the average value of the distance between the centers of gravity of the pores 6 (7) is 5 μm or more, the voids are dispersed and arranged without being densely packed. Therefore, it has even higher mechanical properties. On the other hand, if the value obtained by subtracting the average value of the equivalent circle diameter of the pores 6 (7) from the average value of the distance between the centers of gravity of the pores 6 (7) is 10 μm or less, the surfaces 1 and 2 are ground and polished in the depth direction. Good processability can be obtained when processing such as. Further, since the distance between the adjacent pores is narrowed, the expansion of microcracks can be suppressed. By narrowing the distance between the adjacent pores, the effect of removing the charge is enhanced.

The equivalent circle diameter of the pore 6 (7) can be obtained by the following method. First, the cross section is observed at a magnification of 200 times using a digital microscope, and the area is, for example, 0.11 mm ² (horizontal length is 380.71 μm, vertical length is 285.53 μm). The range may be photographed with a CCD camera to obtain the equivalent circle diameter of each pore 6 (7) in the observation image. The threshold value, which is an index indicating the brightness of the image, may be set so that the equivalent circle diameter of 0.27 μm or less is excluded from the measurement. The circle-equivalent diameter of the pore 6 (7) obtained by the above method is, for example, 1 μm or more and 3 μm or less.

The distance between the centers of gravity of the pores 6 (7) can be obtained by the following method. Dispersity using image analysis software "A image-kun (ver2.52)" (registered trademark, manufactured by Asahi Kasei Engineering Co., Ltd.) for observation images taken to obtain the equivalent circle diameter of pore 6 (7). The distance between the centers of the pores 6 (7) may be obtained by a method called the distance between the centers of measurement. Hereinafter, when the image analysis software "A image-kun" is described, the image analysis software manufactured by Asahi Kasei Engineering Co., Ltd. is shown.

As the setting conditions of this method, for example, a threshold value indicating the brightness of the image may be 165 to 176, the brightness may be bright, the small figure removal area may be 0.057 μm ² , and a noise removal filter may be provided. In the above measurement, the threshold value was set to 165 to 176, but the threshold value may be adjusted according to the brightness of the observed image. After setting the area to 0.057 μm ² and having a noise reduction filter, the threshold value may be adjusted so that the marker appearing in the observation image matches the shape of the pores. The distance between the centers of gravity of the pores 6 (7) obtained by the above method is, for example, 7 μm or more and 14 μm or less.

In the ceramic structures 10 and 20, in any of the surface layer regions 3, 4 and the internal region 5, the maximum value of the equivalent circle diameter of the pores 6 (7) in the observation image may be 10 μm or less. When the maximum value of the equivalent circle diameter of the pores 6 (7) is 10 μm or less, even if polishing is performed in the depth direction from the surfaces 1 and 2, the parts that are easily worn locally are reduced, so that uneven wear is suppressed. be able to. In the ceramic structures 10 and 20, the number of pores having a circle equivalent diameter of 5 μm or more in the observed image is a (pieces) in any of the surface layer regions 3, 4 and the internal region 5, and the circle equivalent diameter in the observed image is less than 5 μm. When the number of pores in the above is b (pieces), the ratio b / a may be 50 or more.

When the ratio b / a is in this range, there are almost no large pores formed by gathering pores generated in the generation process, and small pores are dispersed and arranged. Therefore, even if it is placed in an environment where the temperature rises and falls repeatedly and microcracks occur, their progress can be suppressed by the pores 6 (7). The ratio b / a may be 80 or more, and in particular, the ratio b / a may be 100 or more. The number of pores 6 (7) may be determined by using a digital microscope for the above-mentioned observation image.

In the ceramic structures 10 and 20, in any of the surface layer regions 3, 4 and the internal region 5, the kurtosis Ku of the equivalent circle diameter of the pores 6 (7) in the observation image may be 0.5 or more and 5 or less. .. When the kurtosis Ku of the equivalent circle diameter of the pore 6 (7) is in this range, the distribution of the equivalent circle diameter of the pore 6 (7) is narrow, and there are few pores 6 (7) having an abnormally large equivalent circle diameter. Become. As a result, even if the surface 1 (2) is polished in the depth direction, uneven wear can be suppressed. In particular, the kurtosis Ku is preferably 2 or more and 4 or less. In the example shown in FIG. 3, the kurtosis Ku of the equivalent circle diameter of the pore 6 (7) is 2.7 in FIG. 3 (a), 3.8 in FIG. 3 (b), and FIG. 3 (c). ) Is 2.4.

Here, kurtosis Ku is an index (statistic) indicating how much the peak and tail of the distribution differ from the normal distribution. When the kurtosis Ku> 0, the distribution has a sharp peak and a long and thick hem. When the kurtosis Ku = 0, the distribution is normal. When the kurtosis Ku <0, the distribution has a rounded peak and a short, thin tail. The kurtosis Ku of the diameter equivalent to the circle of the pore 6 (7) may be obtained by using the function Kurt provided in Excel (registered trademark, Microsoft Corporation).

Further, in the ceramic structures 10 and 20, the skewness Sk of the diameter corresponding to the circle of the pores may be 0.5 or more and 2 or less in any of the surface layer regions 3, 4 and the internal region 5. When the skewness Sk of the circle-equivalent diameter of the pore 6 (7) is in this range, the average value of the circle-equivalent diameter of the pore 6 (7) is small, and the pore 6 (7) having an abnormally large circle-equivalent diameter is formed. Less. As a result, even if the surface 1 (2) is polished in the depth direction, uneven wear can be suppressed. In particular, the skewness Sk is preferably 1 or more and 1.8 or less. In the example shown in FIG. 3, the skewness Sk of the equivalent circle diameter of the pore 6 (7) is 1.2 in FIG. 3 (a), 1.4 in FIG. 3 (b), and FIG. 3 (c). ) Is 1.1.

Here, the skewness Sk is an index (statistic) indicating how much the distribution is distorted from the normal distribution, that is, the left-right symmetry of the distribution. When the skewness Sk> 0, the tail of the distribution goes to the right. When the skewness Sk = 0, the distribution is symmetrical. When the skewness Sk <0, the tail of the distribution goes to the left. The skewness Sk of the equivalent circle diameter of the pore 6 (7) may be obtained by using the function SKEW provided in Excel (registered trademark, Microsoft Corporation).

In the ceramic structures 10 and 20, the average value of the particle size of the crystal particles in the observed image may be 1 μm or more and 4 μm or less in at least one of the surface layer regions 3, 4 and the internal region 5. When the average value of the particle size of the crystal particles is 1 μm or more, it is possible to suppress the manufacturing cost by finely pulverizing the raw material as a main component such as aluminum oxide (Al ₂ O ₃ ) powder. When the average value of the particle size of the crystal particles is 4 μm or less, mechanical properties such as fracture toughness and rigidity can be enhanced. In particular, in the ceramic structures 10 and 20, it is preferable that the average value of the particle size of the crystal particles in the observed image is 1 μm or more and 4 μm or less in each of the surface layer regions 3, 4 and the internal region 5.

In the ceramic structures 10 and 20, the kurtosis K _u2 of the particle size of the crystal particles in the observed image may be 0 or more in at least one of the surface layer regions 3, 4 and the internal region 5. When the kurtosis K _u2 of the grain size of the crystal particles is 0 or more, the variation in the grain size of the crystal particles is suppressed. As a result, the agglomeration of the pores is reduced, and the shedding that occurs from the contour and the inside of the pores can be reduced. In particular, in the ceramic structures 10 and 20, it is preferable that the kurtosis K _u2 of the grain size of the crystal particles in the observed image is 5 or more in each of the surface layer regions 3, 4 and the internal region 5.

In the ceramic structures 10 and 20, the skewness _Sk2 of the grain size of the crystal particles in the observed image may be 0 or more in at least one of the surface layer regions 3, 4 and the internal region 5. When the skewness _Sk2 of the grain size of the crystal particles is 0 or more, the distribution of the grain size of the crystal particles moves in the direction of the smaller grain size. As a result, the agglomeration of the pores is reduced, and the shedding that occurs from the contour and the inside of the pores can be further reduced. In particular, in the ceramic structures 10 and 20, it is preferable that the skewness _Sk2 of the grain size of the crystal particles in the observed image is 1.5 or more in each of the surface layer regions 3, 4 and the internal region 5.

Here, the particle size of the crystal particles can be obtained as follows. First, each inner surface of the ceramic structures 10 and 20 in the depth direction from the surfaces 1 and 2, for example, at 0.6 mm and 5 mm, is polished on a copper plate using diamond abrasive grains having an average particle size D ₅₀ of 3 μm. Then, it is polished on a tin plate using diamond abrasive grains having an average particle size D ₅₀ of 0.5 μm. The polished surface obtained by these polishings is subjected to heat treatment at 1480 ° C. until the crystal particles and the grain boundary layer can be distinguished, and a cross section as an observation surface is obtained. The heat treatment is performed for, for example, about 30 minutes.

The heat-treated surface is observed with an optical microscope, and an image is taken at a magnification of, for example, 400 times. Of the captured images, the measurement range is an area of 4.8747 × 10 ³ μm. By analyzing this measurement range using image analysis software (for example, Win ROOF manufactured by Mitani Corporation), the particle size of each crystal particle can be obtained. The average value of the grain sizes of the crystal particles, the kurtosis K _u2 and the skewness _Sk2 may be obtained by using the functions provided in Excel (registered trademark: Microsoft Corporation).

Next, an embodiment of the method for manufacturing the ceramic structure of the present disclosure will be described. First, aluminum oxide (Al ₂ O ₃ ) powder with an average particle size of 0.4 to 0.8 μm, magnesium hydroxide (Mg (OH) ₂ ) powder as the Mg source, and silicon oxide (SiO ₂ ) powder as the Si source. Prepare strontium carbonate (SrCO ₃ ) powder as an Sr source. Each powder has an average particle size of, for example, about 0.4 to 0.8 μm. The other powder is mixed, for example, in the following ratio with respect to 100 parts by mass of the aluminum oxide (Al ₂ O ₃ ) powder.
Mg (OH) ₂ powder: 0.03 parts by mass or more and 0.06 parts by mass or less SiO ₂ powder: 0.02 parts by mass or more and 0.04 parts by mass or less SrCO ₃ powder: 0.03 parts by mass or more and 0.05 parts by mass Less than.

Al ₂ O ₃ powder, Mg (OH) ₂ powder, SiO ₂ powder and SrCO ₃ powder are put into a mixing device, and a dispersant, a defoaming agent, a thickening stabilizer and a binder are further added. Then, it is mixed and pulverized to obtain a slurry. The obtained slurry is defoamed using a vacuum pump.

Here, in order to obtain a ceramic structure in which the value obtained by subtracting the average value of the equivalent circle diameters of the pores from the average value of the distance between the centers of gravity of the pores in the observed image is 5 μm or more and 10 μm or less, aluminum oxide (Al ₂ O ₃ ) is obtained. ) The defoaming agent may be added in an amount of 0.05 parts by mass or more and 0.09 parts by mass or less with respect to 100 parts by mass of the powder. In order to obtain a ceramic structure in which the maximum value of the equivalent circle diameter of the pores in the observation image is 10 μm or less, in order to suppress the thickening that tends to occur in pulverization, a chelating agent is used as an aluminum oxide (Al ₂ O ₃ ) powder 100. 0.03 parts by mass and 0.07 parts by mass may be added to the parts by mass.

In order to obtain a ceramic structure having a ratio b / a of 50 or more, defoaming may be performed for 30 minutes or more. In order to obtain a ceramic structure having a kurtosis Ku of the equivalent circle diameter of the pores of 0.5 or more and 2 or less, for example, a chelating agent may be added in the above range, and mixing and pulverization may be carried out for 10 hours or more. In order to obtain a ceramic structure having a skewness Sk of 0.5 or more and 2 or less of the equivalent circle diameter of the pores, for example, a chelating agent may be added in the above range, and mixing and pulverization may be carried out for 15 hours or more.

To obtain a ceramic structure in which the average particle size of the crystal particles in at least one observation image of the surface layer region and the internal region is 1 μm or more and 4 μm or less, the average particle size D ₅₀ of the mixed and crushed powder is, for example, 0. It may be set to be .3 μm or more and 0.7 μm or less.

To obtain a ceramic structure in which the _kurtosis of the grain size of the crystal particles is 0 or more in at least one observation image of the surface layer region and the internal region, the powder is pulverized until the kurtosis of the particle size of the powder is 0 or more. You just have to extend the time.

Similarly, in order to obtain a ceramic structure in which the skewness _Sk2 of the grain size of the crystal particles in at least one observation image of the surface layer region and the internal region is 0 or more, the skewness of the particle size of the powder is 0 or more. You can extend the crushing time to.

The slurry obtained by such a method is injected into a molding die made of a metal having high thermal conductivity, and then solidified at a temperature of 50 ° C. or higher and 100 ° C. or lower in this state to obtain a solidified body. Then, after the solidified body is demolded, it is dried under the controlled temperature and humidity to obtain a dried body. Next, after degreasing the dried product at 400 ° C. or higher and 550 ° C. or lower, the firing temperature is set to 1550 ° C. or higher and 1650 ° C. or lower, and the dried product is held for 5 hours or longer and 10 hours or lower. In this way, the ceramic structure of the present disclosure having a ratio B / A of 1.5 or less can be obtained.

The ceramic structure obtained by the above-mentioned manufacturing method has almost no deterioration in mechanical properties even if it is long or large. Therefore, it can be used for applications requiring high mechanical properties, for example, a member for a semiconductor manufacturing device and a member for a liquid crystal manufacturing device.

1, 2 Surface 3, 4 Surface area 5 Internal area 6, 7 Pore 10, 20 Ceramic structure

Claims (10)

It ’s a ceramic structure.
In the observation image of the cross section, the area occupancy of the pores in the surface layer region of 0.7 mm or less in the depth direction from the surface is defined as A (%), and the area occupancy of the pores in the internal region deeper than 0.7 mm in the depth direction from the surface. When the ratio is B (%), B is larger than A, and the ratio B / A is 1.5 or less .
In both the surface layer region and the internal region, the value obtained by subtracting the average value of the equivalent circle diameter of the pores from the average value of the distance between the centers of gravity of the pores in the observation image is 5 μm or more and 10 μm or less .
Ceramic structure. A ceramic structure composed of a dense body having a relative density of 95% or more.
In the observation image of the cross section, the area occupancy of the pores in the surface layer region of 0.7 mm or less in the depth direction from the surface is defined as A (%), and the area occupancy of the pores in the internal region deeper than 0.7 mm in the depth direction from the surface. When the ratio is B (%), B is larger than A and the ratio B / A is 1.5 or less.
Ceramic structure. Claim 2 is that in both the surface layer region and the internal region, the value obtained by subtracting the average value of the equivalent circle diameter of the pores from the average value of the distance between the centers of gravity of the pores in the observation image is 5 μm or more and 10 μm or less. The ceramic structure described in. The ceramic structure according to any one of claims 1 to 3 , wherein the maximum value of the equivalent circle diameter of the pores in the observation image is 10 μm or less in both the surface layer region and the internal region. In both the surface layer region and the internal region, the number of the pores having a circle equivalent diameter of 5 μm or more in the observation image is a (pieces), and the number of the pores having a circle equivalent diameter of less than 5 μm in the observation image is b. The ceramic structure according to any one of claims 1 to 4 , wherein the ratio b / a is 50 or more in the case of (pieces). The ceramic structure according to any one of claims 1 to 5 , wherein the kurtosis Ku of the equivalent circle diameter of the pores in the observation image is 0.5 or more and 5 or less in both the surface layer region and the internal region. .. The ceramic structure according to any one of claims 1 to 6 , wherein the skewness Sk of the equivalent circle diameter of the pores is 0.5 or more and 2 or less in both the surface layer region and the internal region. The ceramic structure according to any one of claims 1 to 7 , wherein at least one of the surface layer region and the internal region has an average value of the particle size of crystal particles in the observation image of 1 μm or more and 4 μm or less. The ceramic structure according to any one of claims 1 to 8 , wherein at least one of the surface layer region and the internal region has a kurtosis K _u2 of the particle size of the crystal particles in the observation image of 0 or more. The ceramic structure according to any one of claims 1 to 9 , wherein at least one of the surface layer region and the internal region has a skewness _Sk2 of the grain size of the crystal particles in the observation image of 0 or more.

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