TW202114964A - Ceramic structure - Google Patents

Abstract

A ceramic structure of the present disclosure contains aluminum oxide as a main component. When the diffraction intensities of the (113) and (116) planes of aluminum oxide obtained by the X-ray diffraction method are set as I (113) and I (116), respectively, and I (113)/I (116) is set as the ratio of diffraction intensities, the ratio Ri, which is the ratio of the diffraction intensities in an internal region deeper than 0.7 mm in the depth direction from the surface, is larger than 1, and the ratio Rs, which is the ratio of the diffraction intensities in a surface layer region of 0.7 mm or less in the depth direction from the surface, is smaller than 1.

Description

Ceramic structure

The present disclosure relates to a ceramic structure with good processing efficiency such as grinding and polishing.

When measuring the surface or inside of a general alumina sintered body by X-ray diffraction, according to the ICDD (The International Centre for Diffraction Data) card, the surface showing the maximum peak intensity is (104) Noodles or (113) noodles. Furthermore, according to Japanese Patent Application Laid-Open No. 2007-254276, it has been described that the alumina sintered body manufactured by the press molding method or the like generally clearly appears opposite to the (110), (104), (113) or (116) The crystal orientation of the plane.

Since the conventional alumina sintered body clearly exhibits crystal orientation, it has high wear resistance. If a ceramic structure composed of such an alumina sintered body is a long strip with a length of 2 m or more in the longitudinal direction, or a large one with a diameter of 1 m or more, there is a problem that the efficiency of processing such as grinding and polishing is reduced.

The present disclosure provides a ceramic structure that has good processing efficiency such as grinding and polishing even if the ceramic structure is elongated or large.

The ceramic structure system of the present disclosure contains alumina as the main component, and the diffraction intensities of the (113) plane and (116) plane of the alumina obtained by the X-ray diffraction method are respectively set as I(113) and I( 116), and taking I(113)/I(116) as the ratio of the diffraction intensity, the aforementioned diffraction intensity ratio in the inner region exceeding 0.7mm from the surface to the depth direction, that is, the ratio of the Ri system is greater than 1, from The aforementioned diffraction intensity ratio in the surface layer region whose surface is 0.7 mm or less in the depth direction, that is, the ratio Rs is less than 1.

According to the present disclosure, it is possible to provide a ceramic structure with good processing efficiency such as grinding and polishing.

1,2: surface

3,4: surface area

5: Internal area

6, 7: Stoma

10, 20: Ceramic structure

Fig. 1 is a perspective view of a ceramic structure related to an embodiment of the present disclosure.

Fig. 2 is a perspective view of a ceramic structure according to another embodiment of the present disclosure.

Fig. 3 is a cross-section of the ceramic structure shown in Fig. 1, Fig. 3(a) is an example of an observation image of a cross-section in the surface area, and Fig. 3(b) is an observation view of a cross-section of the inner area near the surface area As an example, FIG. 3(c) is an example of an observation image of a cross-section of the inner region on the side away from the surface region.

Hereinafter, referring to the drawings, the ceramic structure of the present disclosure will be described in detail. Fig. 1 is a perspective view of a ceramic structure related to an embodiment of the present disclosure. Fig. 2 is a perspective view of a ceramic structure according to another embodiment of the present disclosure.

The ceramic structure 10 shown in FIG. 1 has a long strip shape, for example, a length of 2 m to 4 m, a width of 200 mm to 300 mm, and a height of 20 mm to 80 mm. The ceramic structure 20 shown in FIG. 2 has a large circular plate shape, for example, a diameter of 2 m to 4 m, and a height of 20 mm to 80 mm. Each of the ceramic structures 10, 20 is a dense body with a relative density of 95% or more, and has surface areas 3, 4 that are 0.7 mm or less from the surface 1 and 2 toward the depth direction, and the surface area toward the depth direction is Inner area over 0.7mm5.

The relative density is expressed as a percentage (ratio) of the apparent density of the ceramic structures 10, 20 obtained in accordance with JIS R 1634-1998 with respect to the theoretical density of the ceramic structures 10, 20 of the identified main component.

The ceramic structure system of the present disclosure uses alumina as the main component, and the diffraction intensities of the (113) plane and (116) plane of the alumina obtained by the X-ray diffraction method are respectively set as I(113) and I( 116), and when I(113)/I(116) is used as the ratio of the diffraction intensity, the above-mentioned diffraction intensity ratio in the inner region, that is, the ratio of Ri is greater than 1, and the above-mentioned diffraction intensity ratio in the surface region is that It is less than 1 than the Rs line. In other words, when the diffraction intensities of the (113) plane and (116) plane of the alumina in the inner region are respectively referred to as Ii(113) and Ii(116), the ratio Ri is expressed as Ii(113)/Ii(116) . When the diffraction intensities of the (113) plane and the (116) plane of the alumina in the surface region are set to Is(113) and Is(116), respectively, the ratio Rs is expressed as Is(113)/Is(116).

If the ratio Ri and the ratio Rs of the diffraction intensity are set in such a relationship, the crystal orientation changes from the inner region to the surface region. Therefore, compared with the case where the crystal orientation is clearly displayed in the inner region and the surface region, the damage in the surface region tends to be lower and the processing efficiency to be higher.

The difference between the ratio Ri and the ratio Rs may be 0.4 or less. If the difference between the ratio Ri and the ratio Rs is within such a range, the deformation generated in the inner region will be reduced. As a result, the mechanical strength at high temperature (for example, 1000°C to 1300°C) will decrease in comparison with the mechanical strength at room temperature.

The so-called main component in the ceramic structure means a component that occupies more than 80% by mass among 100% by mass of the components constituting the ceramic structure. As long as the components constituting the ceramic structure are identified based on the measurement results obtained by the X-ray diffraction device using CuKα rays, use an ICP (Inductively Coupled Plasma) emission spectrometer or a fluorescent X-ray analyzer (XRF). ) Find the content of the element and convert it to the content of the identified component.

The respective diffraction intensities of the (113) plane and the (116) plane of alumina can be obtained by an X-ray diffraction device using CuKα rays. For example, the surface area is a heat-treated surface, and the internal area is a section cut with a grinding device. For example, the arithmetic average roughness Ra of the surface of the surface region is 0.4 μm or more and 0.6 μm or less, and the arithmetic average roughness Ra of the cross section of the internal region is 0.2 μm or more and 0.4 μm or less, as long as it is measured in accordance with JIS B 0601:1994. More specifically, just use a surface roughness measuring machine (SURFCORDER, SE500) manufactured by Kosaka Research Institute Co., Ltd., set the radius of the stylus to 5μm, the conveying speed of the stylus to 0.5mm/s, and measure the length Just set it to 4.0mm and the cutoff value λc to 0.8mm.

Fig. 3 is a cross-section of the ceramic structure shown in Fig. 1, and Fig. 3(a) is an example of an observation image of the cross-section in the surface region. Fig. 3(b) is an example of an observation image of a cross-section in the inner region on the side close to the surface region. Fig. 3(c) is an example of an observation image of a cross section in the inner region on the side away from the surface region.

As shown in FIG. 3(a), pores 6 are dispersedly arranged in the surface region 3 system. As shown in FIGS. 3(b) and (c), the pores 7 are dispersedly arranged in the internal region 5. When the area occupancy rate of the pores 6 in the surface region 3 is set to A (%), and the area occupancy rate of the pores 7 in the inner region 5 is set to B (%), in the example shown in FIG. 3(a) , The area occupancy rate A is 3.12%. The area occupancy rate B (%) of the pores 7 in the inner region 5 near the surface region 3 side (hereinafter, the area occupancy rate B (%) may be described as the area occupancy rate B ₁ (%)) is 3.46% . The area occupancy rate B (%) of the pores 7 in the inner region 5 on the side away from the surface region 3 (hereinafter, the area occupancy rate B (%) may be described as the area occupancy rate B ₂ (%)) is 4.16% .

In the observation image of the cross-section of the ceramic structure of the present disclosure, the ratio B/A may be 1.5 or less. When the ratio B/A is in this range, the internal region 5 reduces the number of voids in which mechanical properties such as strength and rigidity are reduced. Therefore, the parts with low mechanical properties are reduced, and the mechanical properties are high. 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 area of the ceramic structure to the inner area. Figure 3(a) is the polishing surface from the surface 1 to the depth direction of 0.7mm, Figure 3(b) is the polishing surface from the surface 1 to the depth direction of 7.5mm, and Figure 3(c) is from the surface 1 The polished surface at a position of 15 mm in the depth direction.

These polishing surfaces use diamond abrasive grains with an average particle size D ₅₀ of 4 μm or more to grind with a cast iron flat disc, and then use _{diamond abrasive grains with an average particle size D 50} of 2 μm or more to grind in the depth direction with a tin flat disc. It can be obtained up to 0.7mm, 7.5mm and 15mm. The arithmetic average roughness Ra of these polished surfaces is, for example, 5 nm or less. The arithmetic average roughness Ra system can be measured using a 3D optical surface profiler "NEW VIEW" (registered trademark Zygo Corporation).

In any of the surface area 3, 4 and the inner area 5 of the ceramic structure 10, 20, the average value of the distance between the centers of gravity of the pores 6(7) minus the average value of the circle equivalent diameter of the pores 6(7) The value obtained can be 5 μm or more and 10 μm or less.

If the average value of the distance between the centers of gravity of the pores 6(7) is subtracted from the average value of the circle-equivalent diameter of the pores 6(7) to obtain a value of 5 μm or more, the voids are not arranged densely and dispersedly. Therefore, higher mechanical properties can be exerted. On the other hand, if the average value of the distance between the centers of gravity of stomata 6(7) is subtracted from the stomata The value of the average value of the circle equivalent diameter of 6(7) is 10 μm or less, and when the surfaces 1 and 2 are processed in the depth direction, such as grinding and polishing, good workability can be obtained. Furthermore, the interval between adjacent pores is narrowed, so the extension of microcracks can be suppressed. As the interval between adjacent pores becomes narrower, the effect of removing electrification becomes higher.

The circle equivalent diameter of pore 6(7) can be obtained by the following method. First, use a digital microscope to observe the above section at a magnification of 200 times. Then, for example, as long as the shooting area of the CCD camera ^{is 0.11 mm 2} (the length in the horizontal direction is 380.71 μm, the length in the vertical direction is 285.53 μm), the circle of each pore 6 (7) in the observation image is obtained. The equivalent diameter is sufficient. In addition, the threshold value, which is an indicator of the brightness and darkness of the displayed image, may be set so that the circle equivalent diameter of 0.27 μm or less is not the object of measurement. The circle-equivalent diameter of the pore 6 (7) obtained by the above-mentioned method is, for example, 1 μm or more and 3 μm or less.

The distance between the centers of gravity of stomata 6(7) can be obtained by the following method. As long as the circle equivalent diameter of the stomata 6(7) is obtained, and the observation image obtained by shooting is used as the object, use the image analysis software "A Xiangjun (ver2.52)" (registered trademark, manufactured by Asahi Kasei Enginerring Co., Ltd.) , And, when the following description is the image analysis software "A Xiangjun", it means the image analysis software manufactured by Asahi Kasei Enginerring Co., Ltd.) And the method of the distance between the centers of gravity of the so-called dispersion measurement method is used to obtain the stomata 6 ( 7) The distance between the centers of gravity is sufficient.

The setting conditions of this method are, for example, as long as the threshold value as an indicator of the brightness and darkness of the displayed image is set to 165 to 176, the brightness is set to dark, the small pattern removal area is set to 0.057μm ² , and the noise removal filter is set Just as there is. In the above measurement, the threshold is set to 165 to 176, but it is enough to adjust the threshold according to the brightness of the observed image, set the brightness to dark, and set the binarization method to manual, and set the small pattern removal area to 0.057 After setting the μm ² and noise removal filter to Yes, just adjust the threshold in such a way that the markers appearing in the observation image are consistent with 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 any of the surface area 3, 4 and the inner area 5 of the ceramic structures 10, 20, the maximum value of the circle equivalent diameter of the pore 6 (7) in the observation image may be 10 μm or less. If the maximum value of the circle-equivalent diameter of the pores 6 (7) is 10 μm or less, even if the surfaces 1 and 2 are polished in the depth direction, the parts that are likely to be locally worn will be reduced. As a result, partial wear can be suppressed.

In any of the surface area 3, 4 and the inner area 5 of the ceramic structures 10 and 20, the number of pores with a circle equivalent diameter of 5 μm or more in the observation image is set to a (number), and the observation image When the number of pores with a circle-equivalent diameter of less than 5 μm is set to b (number), the ratio b/a can be 50 or more. If the ratio b/a is in this range, the large pores formed by the accumulation of pores that were originally generated during the generation process will almost disappear, and small pores will be dispersedly arranged. Therefore, when placed in an environment where the temperature is raised and lowered repeatedly, even if microcracks are generated, the elongation can be suppressed by the pores 6(7).

The ratio b/a may be 80 or more, and in particular, the ratio b/a is preferably 100 or more. The number system of the pores 6(7) may be obtained by using a digital microscope with the above-mentioned observation image as an object.

In any of the surface regions 3, 4 and the inner region 5 of the ceramic structures 10 and 20, the kurtosis Ku of the circle-equivalent diameter of the pore 6 (7) in the observation image may be 0.5 or more and 5 or less. If the kurtosis Ku of the circle-equivalent diameter of the stomata 6(7) is in this range, the distribution of the circle-equivalent diameter of the stomata 6(7) becomes narrower, and the abnormally large circle-equivalent diameter stomata 6(7) Fewer. Therefore, 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 circle-equivalent diameter of the pore 6(7) is 2.7 in (a), 3.8 in (b), and 2.4 in (c).

The so-called kurtosis Ku is an index (statistic) that shows how much the peak and tail of the distribution differ from the normal distribution. When the kurtosis Ku>0, it will become a component with sharp peaks and long and thick tails. cloth. When kurtosis Ku=0, it will become a normal distribution. When kurtosis Ku<0, the distribution will become a distribution with rounded peaks and short tails. The kurtosis Ku of the circle-equivalent diameter of the pore 6(7) can be obtained by using the function Kurt provided in Excel (registered trademark, Microsoft Corporation).

In any of the surface regions 3 and 4 and the internal region 5 of the ceramic structures 10 and 20, the skewness Sk of the circle equivalent diameter of the pores may be 0.5 or more and 2 or less. If 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 abnormally large circle equivalent diameter of the pore 6(7) changes less. Therefore, 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 circle equivalent diameter of the pore 6(7) is 1.2 in (a), 1.4 in (b), and 1.1 in (c).

The so-called skewness Sk is how much the distribution is skewed from the normal distribution, that is, an index (statistic) that shows the left and right symmetry of the distribution. When the skewness Sk>0, the long tail of the distribution will face to the right. When the skewness Sk=0, the distribution will become symmetrical. When the skewness Sk<0, the tail of the distribution will be toward the left. The skewness Sk of the circle equivalent diameter of the pore 6(7) can be obtained by using the function SKEW provided in Excel (registered trademark, Microsoft Corporation).

In at least any one of the surface region 3, 4 and the inner region 5 of the ceramic structures 10 and 20, the average value of the particle size of the crystal particles in the observation image may be 1 μm or more and 4 μm or less. If the average particle diameter of the crystal particles is 1 μm or more, the production cost caused by finely pulverizing raw materials such as _{alumina (Al 2} O _{3) powder as the main component can be suppressed.} If the average particle size of the crystal particles is 4 μm or less, mechanical properties such as fracture toughness and rigidity can be improved. In particular, in any one of the surface layer regions 3, 4 and the inner region 5 of the ceramic structures 10 and 20, the average value of the particle size of the crystal particles in the observation image is preferably 1 μm or more and 4 μm or less.

In at least any of the surface regions 3, 4 and the inner region 5 of the ceramic structures 10 and 20, the kurtosis _Ku2 of the particle size of the crystal particles in the observation image may be 0 or more. If the kurtosis K _{u2 of} the particle diameter of the crystal particles is in this range, the variation of the particle diameter of the crystal particles can be suppressed. Therefore, the agglomeration of the pores is reduced, and the threshing generated from the outline or the inside of the pores can be reduced. In particular, for any of the surface regions 3 and 4 and the inner region 5 of the ceramic structures 10 and 20, the kurtosis _Ku2 of the particle size of the crystal particles in the observation image is preferably 5 or more.

In at least any of the surface regions 3 and 4 and the inner region 5 of the ceramic structures 10 and 20, the skewness _Sk2 of the particle size of the crystal particles in the observation image may be 0 or more. If the skewness _{Sk2 of} the particle size of the crystal particles is within this range, the distribution of the particle size of the crystal particles will move toward the smaller particle size. Therefore, the agglomeration of the pores will be reduced, and the threshing generated from the outline or the inside of the pores can be further reduced. In particular, in any one of the surface regions 3 and 4 and the internal region 5 of the ceramic structures 10 and 20, the skewness _Sk2 of the particle size of the crystal particles in the observation image is preferably 1.5 or more.

The particle size of the crystal particles can be obtained as follows. First, the inner surfaces of the ceramic structures 10, 20 that are separated from the surfaces 1 and 2 in the depth direction, for example, 0.6 mm and 5 mm in the depth direction, are polished with a copper disk using diamond abrasive grains with _{an average particle diameter D 50 of 3 μm.} Thereafter, diamond abrasive grains with an average particle diameter D ₅₀ of 0.5 μm were used for polishing with a tin plate. The polished surface obtained by such polishing is heat-treated at a temperature of 1480°C until the crystal particles and the grain boundary layer can be recognized to obtain a cross section as an observation surface. The heat treatment time is, for example, 30 minutes.

In addition, the heat-treated surface was photographed using an optical microscope at a magnification of 400 times. Then, among the captured images, the area of 4.8747×10 ² μm ² is used as the measurement range, and image analysis software (for example, manufactured by Mitani Corporation, Win ROOF) is used for analysis. Obtain the particle size of each crystal particle.

The threshold value of the circle equivalent diameter corresponding to the particle diameter of the crystal particles may be set to 1 μm. The average value, kurtosis K _u2 and skewness S _k2 of the crystal particle diameter can be obtained by using functions provided in Excel (registered trademark, Microsoft Corporation).

Next, an example of the method of manufacturing the ceramic structure of the present disclosure will be explained. _{First, prepare 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 a source of _{Mg, silicon oxide (SiO 2} ) powder as a source of Si, _{Strontium carbonate (SrCO 3} ) powder as a source of Sr.

Relative to 100 parts by mass of alumina (Al ₂ O ₃ ) powder, magnesium hydroxide (Mg(OH) ₂ ) powder is set to 0.03 parts by mass or more and 0.06 parts by mass or less, and silica (SiO ₂ ) powder is set to 0.02 parts by mass The strontium carbonate (SrCO ₃ ) powder is set to 0.03 parts by mass or more and 0.05 parts by mass or less. In addition, aluminum oxide (Al ₂ O ₃ ) powder, magnesium hydroxide (Mg(OH) ₂ ) powder, silicon _{oxide (SiO 2} ) powder, and strontium carbonate (SrCO ₃ ) powder, as well as dispersant, defoamer, and viscosity increase After the stabilizer and the binder are added to the mixing device and mixed/pulverized to form a slurry, a vacuum pump is used for defoaming.

In order to obtain a ceramic structure with a value of 5 μm or more and 10 μm or less by subtracting the average value of the distance between the centers of gravity of the pores from the average value of the pore circle equivalent diameter from the observation image, compared with alumina (Al ₂ O ₃ ) 100 parts by mass of the powder, as long as 0.05 parts by mass or more and 0.09 parts by mass or less of the defoamer are added. In order to obtain a ceramic structure in which the maximum value of the circle-equivalent diameter of the pores in the observation image is 10 μm or less, in order to suppress the increase in viscosity easily caused by pulverization, relative to 100 parts by mass of _{alumina (Al 2} O _{3) powder,} It is sufficient to add 0.03 parts by mass and 0.07 parts by mass of the chelating agent.

In order to obtain a ceramic structure with a ratio b/a of 50 or more, it is only necessary to perform degassing for 30 minutes or more. In order to obtain a ceramic structure having a kurtosis Ku of the circle-equivalent diameter of the pores of 0.5 or more and 5 or less, it is only necessary to add a chelating agent within the above-mentioned range and to make the mixing/grinding time be 10 hours or more. in order to To obtain a ceramic structure with a skewness Sk of the equivalent circle diameter of the pores of 0.5 or more and 2 or less, it is only necessary to add a chelating agent within the above range and make the mixing grid crushing time 15 hours or more.

In order to obtain a ceramic structure in which the average particle diameter of the crystal particles in the observation image of at least any one of the surface region and the internal region is 1 μm or more and 4 μm or less, the average particle diameter D of the mixed/pulverized powder ₅₀ may be set so as to be 0.3 μm or more and 0.7 μm or less, for example.

_{In order to obtain a ceramic structure in which the kurtosis K u2} of the particle size of the crystal particles in the observation image of at least any one of the surface region and the inner region is 0 or more, it is only necessary to extend the grinding time to the kurtosis of the particle size of the powder What is necessary is just to become 0 or more. Likewise, in order to obtain the surface region and the interior region of slanting at least one of an observation image of the particle diameter of the crystal particles of S _k2 of 0 or more ceramic structure, as long as the prolonged pulverized to a powder of particle diameter The skewness should just become 0 or more.

The slurry obtained by such a method is injected from the height direction of the molded body into a mold made of a metal with high thermal conductivity, and then cured at a temperature of 50°C or more and 100°C in this state to form a cured body . Next, after the cured body is demolded, it is dried in a state of controlled temperature and humidity to become a dried body. In order to obtain a ceramic structure having a difference between the ratio Ri and the ratio Rs of 0.4 or more, the injection rate of the slurry should be set to 1×10 ³ cm ³ /min or more and 3×10 ³ cm ³ /min or less.

Then, after degreasing the dried body 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 maintained for 5 hours or more and 10 hours or less. In this way, the ceramic structure of the present disclosure having a ratio B/A of 1.5 or less can be obtained.

Even if the ceramic structure system obtained by the above-mentioned manufacturing method is long or large, the mechanical properties are hardly degraded. Therefore, it can be used as an application requiring high mechanical properties, such as 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

10: Ceramic structure

Claims (11)

A ceramic structure containing alumina as the main component, and the diffraction intensities of the (113) plane and (116) plane of the alumina obtained by the X-ray diffraction method are set to I(113) and I( 116), and taking I(113)/I(116) as the ratio of the diffraction intensity, the aforementioned diffraction intensity ratio in the inner region exceeding 0.7mm from the surface to the depth direction, that is, the ratio of the Ri system is greater than 1, from The aforementioned diffraction intensity ratio in the surface layer region whose surface is 0.7 mm or less in the depth direction, that is, the ratio Rs is less than 1. The ceramic structure according to claim 1, wherein the difference between the ratio Ri and the ratio Rs is 0.4 or less. The ceramic structure according to claim 1 or 2, wherein in the cross-sectional observation image, the area occupancy rate of the pores in the surface region is A (%), and the area of the pores in the inner region When the occupancy rate is set to B (%), the ratio B/A is 1.5 or less. The ceramic structure according to claim 3, wherein in any of the surface region and the inner region, the average value of the distance between the centers of gravity of the pores in the observation image is subtracted from the circle of the pores, etc. The value obtained by the average value of the effective diameter is 5 μm or more and 10 μm or less. The ceramic structure according to claim 3 or 4, wherein in any one of the surface layer region and the inner region, the maximum value of the circle equivalent diameter of the pores in the observation image is 10 μm or less. The ceramic structure according to any one of claims 3 to 5, wherein, in any one of the surface region and the internal region, the pores having the equivalent diameter of a circle in the observation image are 5 μm or more When the number of pores is set to a (number), and the number of pores whose circle equivalent diameter in the observation image is less than 5 μm is set to b (number), the ratio b/a is 50 or more. The ceramic structure according to any one of claims 3 to 6, wherein, in any one of the surface layer region and the inner region, the kurtosis Ku of the circle equivalent diameter of the pores in the observation image It is 0.5 or more and 5 or less. The ceramic structure according to any one of claims 3 to 7, wherein in any one of the surface layer region and the inner region, the skewness Sk of the circle equivalent diameter of the pores is 0.5 or more and 2 or less. The ceramic structure according to any one of claims 3 to 8, wherein in at least any one of the surface region and the inner region, the average value of the particle diameter of the crystal particles in the observation image is 1 μm or more Below 4μm. The ceramic structure according to any one of claims 1 to 9, wherein in at least any one of the surface region and the internal region, the kurtosis _Ku2 of the particle diameter of the crystal particles in the observation image is 0 or more. The ceramic structure according to any one of claims 1 to 10, wherein, in at least any one of the surface layer region and the inner region, the skewness _Sk2 of the particle size of the crystal particles in the observation image is 0 or more.

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