Ceramic raw sphere

Abstract

To provide a technique for improving polishing efficiency in a ceramic raw ball.SOLUTION: The ceramic sphere includes a surface layer portion located in an outer peripheral portion of the ceramic sphere, a central portion located inside the surface layer portion, and a glass phase segregation portion located between the surface layer portion and the central portion and containing a larger amount of a glass phase than each of the surface layer portion and the central portion.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a ceramic element sphere. [Background technology]

[0002] BACKGROUND ART Ceramic balls that can be made into ceramic balls by polishing their surfaces have been known (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-93789 Summary of the Invention [Problem to be solved by the invention]

[0004] However, even with prior art such as that disclosed in Patent Document 1, there is still room for improvement in the technology for improving the polishing efficiency of ceramic balls.

[0005] An object of the present invention is to provide a technique for improving the polishing efficiency of ceramic balls. [Means for solving the problem]

[0006] The present invention has been made to solve at least part of the above-mentioned problems, and can be realized in the following aspects.

[0007] (1) According to one aspect of the present invention, there is provided a ceramic element sphere comprising: a surface layer portion located on the outer periphery of the ceramic element sphere, a central portion located inside the surface layer portion, and a glass phase segregation portion located between the surface layer portion and the central portion, the glass phase segregation portion containing a larger amount of glass phase than either the surface layer portion or the central portion.

[0008] According to this configuration, a glass phase segregation portion is formed in the ceramic element sphere between a surface layer portion located on the outer periphery of the ceramic element sphere and a central portion located inside the surface layer portion. The glass phase segregation portion contains a larger amount of glass phase than either the surface layer portion or the central portion, making it more brittle than either the surface layer portion or the central portion. This protects the surface of the ceramic element sphere by covering it with a relatively hard surface layer portion, and when the surface of the ceramic element sphere is polished in the polishing process, the glass phase segregation portion breaks, allowing the surface layer portion and the glass phase segregation portion to be relatively easily separated from the central portion. This improves the polishing efficiency of the ceramic element sphere.

[0009] (2) In the ceramic sphere of the above embodiment, the sum of the thickness of the surface layer portion and the thickness of the glass phase segregation portion in the radial direction of the ceramic sphere may be 11% or less of the radius of the ceramic sphere. According to this configuration, the sum of the thickness of the surface layer portion and the thickness of the glass phase segregation portion is 11% or less of the radius of the ceramic sphere so that it is included in the polishing stock removal when polishing the ceramic sphere. This makes it easier to polish a portion of the polishing stock removal efficiently, thereby improving the polishing efficiency of the ceramic sphere.

[0010] (3) In the ceramic sphere of the above embodiment, the thickness of the surface layer portion in the radial direction of the ceramic sphere may be 10% or more but less than 100% of the sum of the thickness of the surface layer portion in the radial direction of the ceramic sphere and the thickness of the glass phase segregation portion. According to this configuration, a relatively hard surface layer portion is formed as the outer periphery of the ceramic sphere in the portion removed by polishing in the polishing process of the ceramic sphere. This makes it possible to protect the surface of the ceramic sphere while improving the polishing efficiency of the ceramic sphere.

[0011] (4) In the ceramic sphere of the above embodiment, the thickness of the glass phase segregation portion in the radial direction of the ceramic sphere may be 40 μm or less. With this configuration, the relatively brittle glass phase segregation portion is relatively thin and therefore easily broken by polishing in the polishing process of the ceramic sphere. Therefore, the polishing efficiency of the ceramic sphere can be improved.

[0012] (5) In the ceramic element sphere of the above embodiment, the surface layer portion, the glass phase segregation portion, and the central portion each have a plurality of ceramic crystal grains and the glass phase formed between the ceramic crystal grains, and the area of ​​one of the glass phases in a cross section of the surface layer portion or the central portion passing through the center of the ceramic element sphere is 0.2 μm or less. 2 The area of ​​one glass phase in the cross section of the glass phase segregation portion is 0.2 μm 2 or more. According to this configuration, the size of the glass phase contained in the glass phase segregation portion is larger than the size of the glass phase contained in the surface layer portion or the central portion. As a result, the glass phase segregation portion is likely to be more brittle than the surface layer portion or the central portion. Therefore, when the ceramic element sphere is polished in the polishing process of the ceramic element sphere, the glass phase segregation portion is more fragile, and the surface layer portion and the glass phase segregation portion can be more easily separated from the central portion. This further improves the polishing efficiency of the ceramic element sphere.

[0013] (6) The ceramic ball of the above embodiment may be made of silicon nitride. In this configuration, the ceramic ball is made of silicon nitride, and the center portion is relatively hard and has excellent thermal conductivity. This allows the ceramic ball with a polished surface to be used in a wide range of technical fields.

[0014] The present invention can be realized in various forms, such as a method for manufacturing ceramic spheres, an apparatus for manufacturing ceramic spheres, or a computer program for causing the apparatus for manufacturing ceramic spheres to manufacture ceramic spheres. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a cross-sectional view of a ceramic sphere according to a first embodiment. [Figure 2] 1 is an image showing a cross section of a ceramic sphere. [Figure 3] FIG. 2 is a diagram illustrating the size relationship between a ceramic base sphere and a ceramic ball. [Figure 4] FIG. 2 is a schematic diagram showing a cross section of a surface layer portion. [Figure 5] FIG. 2 is a schematic diagram showing a cross section of a glass phase segregation portion. [Figure 6] 1 is a cross-sectional SEM image of a glass phase segregation region. [Figure 7] FIG. 2 is a diagram showing the distribution of silicon elements in a cross section of a glass phase segregation portion. [Figure 8] FIG. 2 is a diagram showing the distribution of lanthanum element in a cross section of a glass phase segregation portion. [Figure 9] FIG. 2 is a diagram showing the distribution of oxygen elements in a cross section of a glass phase segregation portion. [Figure 10] FIG. 1 is a first diagram illustrating the manufacturing conditions of the ceramic blank sphere. [Figure 11] FIG. 2 is a second diagram illustrating the manufacturing conditions of the ceramic blank sphere. DETAILED DESCRIPTION OF THE INVENTION

[0016] First Embodiment FIG. 1 is a cross-sectional view of a ceramic element sphere according to a first embodiment. The ceramic element sphere 1 of this embodiment is turned into a ceramic ball by polishing its surface. The ceramic ball is used, for example, as a bearing ball for a bearing. The ceramic element sphere 1 of this embodiment is made of silicon nitride (Si3N4). In addition to silicon nitride, the ceramic element sphere 1 of this embodiment also contains lanthanum (La), aluminum (Al), and tungsten (W). The ceramic element sphere 1 includes a surface layer portion 10, a central portion 20, and a glass phase segregation portion 30. Note that in the cross-sectional view of the ceramic element sphere 1 shown in FIG. 1, the thickness relationships among the surface layer portion 10, the central portion 20, and the glass phase segregation portion 30 differ from their actual thickness relationships.

[0017] The surface layer portion 10 is located on the outer periphery of the ceramic sphere 1. The surface layer portion 10 has a substantially spherical shell shape. The outer surface of the surface layer portion 10 becomes the surface 1a of the ceramic sphere 1.

[0018] The central portion 20 is located inside the surface layer portion 10. The central portion 20 has a substantially spherical shape. The central portion 20 is the portion of the ceramic base ball 1 that, when polished, becomes a ceramic ball that is used as a product in an actual field.

[0019] The glass phase segregation portion 30 is located between the surface layer portion 10 and the central portion 20. The glass phase segregation portion 30 contains a larger amount of glass phase than either the surface layer portion 10 or the central portion 20. Here, in the ceramic element sphere, "containing a larger amount of glass phase" refers to a relatively large area of ​​glass phase contained in a rectangular region with a side length of 500 μm per unit area in a cross section passing through the center C1 of the ceramic element sphere 1 as shown in FIG. 1 . That is, in the ceramic element sphere 1 of this embodiment, the glass phase ratio of the glass phase segregation portion 30 is larger than the glass phase ratios of the surface layer portion 10 and the central portion 20 in a cross section passing through the center C1 of the ceramic element sphere 1. This makes the glass phase segregation portion 30 more brittle than the relatively dense surface layer portion 10 and the central portion 20. The glass phase segregation portion 30 of this embodiment has a substantially spherical shell shape and is formed in a layered form between the surface layer portion 10 and the central portion 20.

[0020] FIG. 2 is an image showing a cross section of a ceramic element sphere according to this embodiment. FIG. 2 shows an image of a region including the outer periphery of the ceramic element sphere 1 according to this embodiment, taken using an optical microscope. The image shown in FIG. 2 reveals that a glass phase segregation portion 30 and a surface layer portion 10 are formed in layers outside a central portion 20. In the image taken using an optical microscope, the glass phase contained in the glass phase segregation portion 30 appears dark, so as shown in FIG. 2, the glass phase segregation portion 30 appears slightly darker than the surface layer portion 10 and the central portion 20.

[0021] FIG. 3 is a diagram illustrating the size relationship between the ceramic sphere and the ceramic ball. The ceramic sphere 1 of this embodiment becomes a so-called medium-diameter ceramic ball by polishing its surface. Specifically, as shown in FIG. 3, the ceramic sphere 1 before polishing has a diameter of 4.469 mm to 16.375 mm, and the ceramic ball after polishing has a diameter of 3.969 mm to 15.875 mm. In this embodiment, the polishing allowance of the ceramic sphere 1 is 0.500 mm in all cases, and the ratio of the polishing allowance to the diameter of the ceramic sphere 1 is 3.1% to 11.2%.

[0022] In the ceramic sphere 1 of this embodiment, the sum of the thickness of the surface layer portion 10 and the thickness of the glass phase segregation portion 30 in the radial direction of the ceramic sphere 1 is 11% or less of the radius of the ceramic sphere 1. Specifically, in FIG. 1 , which is a cross-sectional view of the ceramic sphere 1 including the center C1, if the thickness of the surface layer portion 10 in the radial direction of the ceramic sphere 1 is thickness d10, the thickness of the glass phase segregation portion 30 in the radial direction of the ceramic sphere 1 is thickness d30, and the radius of the ceramic sphere 1 is radius r1, the ceramic sphere 1 of this embodiment satisfies the relationship of the following formula (1). As a result, in the ceramic sphere 1 of this embodiment, the portions of the surface layer portion 10 and the glass phase segregation portion 30 are included in the polishing stock removal, which makes it easier to efficiently remove part of the polishing stock removal, and the polishing efficiency of the ceramic sphere 1 can be improved. In addition, when a band-shaped protrusion is formed on the surface of the ceramic sphere 1, the thickness d10 of the surface layer portion 10, the thickness d30 of the glass phase segregation portion 30, and the radius r1 of the ceramic sphere 1 are all values ​​for the portions where no protrusion is formed. {(d10+d30) / r1}×100≦11 ···(1)

[0023] In the ceramic sphere 1 of this embodiment, the thickness of the surface layer 10 in the radial direction of the ceramic sphere 1 is 10% or more and less than 100% of the sum of the thickness of the surface layer 10 in the radial direction of the ceramic sphere 1 and the thickness of the glass phase segregation portion 30. Specifically, using the thickness d10 of the surface layer 10 and the thickness d30 of the glass phase segregation portion 30 shown in FIG. 1 , the ceramic sphere 1 of this embodiment satisfies the relationship of the following formula (2). As a result, in the ceramic sphere 1 of this embodiment, the surface of the ceramic sphere 1 can be protected by the relatively hard surface layer 10, thereby preventing problems such as scratches on the surface of the ceramic sphere 1 when handling the ceramic sphere 1. 10≦{d10 / (d10+d30)}×100<100 (2)

[0024] In the ceramic sphere 1 of this embodiment, the thickness d30 of the glass phase segregation portion 30 in the radial direction of the ceramic sphere 1 is 40 μm or less. Because the ceramic sphere 1 of this embodiment has a relatively thin, brittle glass phase segregation portion 30, the ceramic sphere 1 is easily broken by polishing in the polishing process of the ceramic sphere 1, and the glass phase segregation portion 30 is easily removed together with the surface layer portion 10. This improves the polishing efficiency of the ceramic sphere 1.

[0025] In the ceramic sphere 1 of this embodiment, the surface layer portion 10, the glass phase segregation portion 30, and the central portion 20 each have a plurality of silicon nitride crystal grains and a glass phase formed between the silicon nitride crystal grains. In the ceramic sphere 1 of this embodiment, the area of ​​one glass phase in the cross section of the surface layer portion 10 or the central portion 20 passing through the center C1 of the ceramic sphere 1 as shown in FIG. 1 is 0.2 μm 2 The area of ​​one glass phase in the cross section of the glass phase segregation portion 30 is 0.2 μm 2 That's all.

[0026] Fig. 4 is a schematic diagram showing a cross section of a surface layer portion of a ceramic element sphere according to this embodiment. The schematic diagram shown in Fig. 4 shows a cross section of the surface layer portion 10 among cross sections passing through the center C1 of the ceramic element sphere 1. Fig. 4 shows silicon nitride crystal particles C10 and glass phases Pv10 formed between the silicon nitride crystal particles C10, which are included in the surface layer portion 10. Each of the multiple glass phases Pv10 appearing in the cross section of the surface layer portion 10 shown in Fig. 4 has an area of ​​0.2 µm 2 In the ceramic sphere 1 of this embodiment, the area of ​​each of the plurality of glass phases Pv10 appearing in a cross section passing through the center C1 of the ceramic sphere 1 is smaller than 0.1 μm 2 The area size of each of the multiple glass phases as shown in FIG. 4 is the same in the central portion 20 of the ceramic sphere 1.

[0027] Fig. 5 is a schematic diagram showing a cross section of a glass phase segregation portion of a ceramic element sphere according to this embodiment. The schematic diagram shown in Fig. 5 shows a cross section of a glass phase segregation portion 30 in a cross section passing through the center C1 of the ceramic element sphere 1. Fig. 5 shows silicon nitride crystal particles C30 and glass phases Pv30 formed between the silicon nitride crystal particles C30, which are included in the glass phase segregation portion 30. The area of ​​each of the multiple glass phases Pv30 appearing in the cross section of the glass phase segregation portion 30 shown in Fig. 5 is 0.2 µm 2 In the ceramic sphere 1 of this embodiment, the area of ​​each of the plurality of glass phases Pv30 appearing in a cross section passing through the center C1 of the ceramic sphere 1 is 0.2 μm 2 ~5.5μm 2 Thus, the size of a single glass phase contained in the glass phase segregation portion 30 is larger than the size of a single glass phase contained in the surface layer portion 10 or the central portion 20. This makes the glass phase segregation portion 30 more likely to be a weaker layer than the surface layer portion 10 or the central portion 20. Therefore, when the ceramic element sphere 1 is polished in the polishing process of the ceramic element sphere 1, the glass phase segregation portion 30 is more fragile, and the surface layer portion 10 and the glass phase segregation portion 30 can be more easily separated from the central portion 20. This further improves the polishing efficiency of the ceramic element sphere 1.

[0028] Fig. 6 is a cross-sectional SEM image of a glass phase segregation portion of a ceramic element sphere according to this embodiment. Next, the characteristics of the glass phase contained in the glass phase segregation portion 30 will be described. In the cross-sectional SEM image of the glass phase segregation portion 30 shown in Fig. 6, the glass phase appears whitish compared to the surrounding area (for example, the area surrounded by dotted ellipses C1, C2, and C3 shown in Fig. 6).

[0029] FIG. 7 shows the distribution of silicon element in a cross section of a glass phase segregation region. FIG. 8 shows the distribution of lanthanum element in a cross section of a glass phase segregation region. FIG. 9 shows the distribution of oxygen element in a cross section of a glass phase segregation region. Each of FIGS. 7, 8, and 9 shows the results of EDS analysis (energy dispersive X-ray analysis) of the distributions of silicon element, lanthanum element, and oxygen element for the same portion as the cross-sectional SEM image of the glass phase segregation region 30 shown in FIG. 6. In the detection result of silicon element shown in FIG. 7, the areas surrounded by dotted ellipses C1, C2, and C3 shown in FIG. 6 are darker than the surrounding areas, indicating that silicon element is not present in large amounts. On the other hand, in the detection result of lanthanum element shown in FIG. 8 and the detection result of oxygen element shown in FIG. 9, the areas surrounded by dotted ellipses C1, C2, and C3 shown in FIG. 6 are brighter than the surrounding areas, indicating that lanthanum element and oxygen element are each present in larger amounts than the surrounding areas.

[0030] FIG. 10 is a first diagram illustrating the manufacturing conditions for ceramic spheres. Next, a manufacturing method for the ceramic spheres 1 of this embodiment will be described. In the manufacturing method for the ceramic spheres 1, first, silicon nitride (Si3N4) as the main raw material, lanthanum oxide (La2O3) or lanthanum hydroxide (La(OH)3) as the sintering aid, tungsten oxide (WO3), and aluminum oxide (Al2O3) are weighed out so that the raw material proportions are as shown in FIG. 10. The weighed materials are placed in a ball mill and pulverized and mixed for approximately 40 hours to produce a slurry. Next, the produced slurry is spray-dried to obtain a granulated powder. The obtained granulated powder is dried at 60°C for several hours and then pressed using a mold to form a preformed sphere. The preformed spheres are isostatically pressed at a pressure of approximately 200 MPa. The isostatically pressed spheres are heated to approximately 550°C in a nitrogen atmosphere and then degreased by maintaining the temperature at approximately 350°C for one hour. Thereafter, the spherical bodies are calcined in an air atmosphere by maintaining the temperature at 350°C for 1 hour, then increasing the temperature to 550°C and maintaining the temperature for 6 hours, and then lowering the temperature.

[0031] FIG. 11 is a second diagram showing the manufacturing conditions for ceramic spheres. FIG. 11 shows the details of the sub-steps, the temperature conditions, atmospheric conditions, and time for each of the primary and secondary firing steps, which are the major steps after the calcination step in the manufacturing method for ceramic spheres. In the primary firing step, the calcined spheres are heated from room temperature to approximately 1600°C in a vacuum atmosphere, then switched to a nitrogen atmosphere and maintained at approximately 1600°C for three hours, and then cooled. In the secondary firing step after the primary firing step, the temperature is raised to 1710°C in a nitrogen atmosphere, then maintained at 1710°C for two hours, and then cooled. This produces ceramic spheres 1. Note that the manufacturing method for ceramic spheres 1 shown here is merely an example and is not limited to this manufacturing method.

[0032] According to the ceramic sphere 1 of this embodiment described above, the ceramic sphere 1 has a glass phase segregation portion 30 formed between the surface layer portion 10 located on the outer periphery of the ceramic sphere 1 and the central portion 20 located inside the surface layer portion 10. The glass phase segregation portion 30 contains a larger amount of glass phase than either the surface layer portion 10 or the central portion 20, making it more brittle than either the surface layer portion 10 or the central portion 20. This protects the surface of the ceramic sphere 1 by covering it with the relatively hard surface layer portion 10. During the polishing process of the ceramic sphere 1, the glass phase segregation portion 30 breaks, allowing the surface layer portion 10 and the glass phase segregation portion 30 to be relatively easily separated from the central portion 20, which will become the ceramic ball. This improves the polishing efficiency of the ceramic sphere 1.

[0033] Furthermore, according to the ceramic sphere 1 of this embodiment, the sum of the thickness d10 of the surface layer portion 10 and the thickness d30 of the glass phase segregation portion 30 is 11% or less of the radius r1 of the ceramic sphere 1 so that it is included in the polishing stock removal when polishing the ceramic sphere 1. This makes it easier to polish part of the polishing stock removal efficiently, thereby improving the polishing efficiency of the ceramic sphere 1.

[0034] Furthermore, according to the ceramic sphere 1 of this embodiment, the thickness d10 of the surface layer 10 is 10% or more but less than 100% of the sum of the thickness d10 of the surface layer 10 and the thickness d30 of the glass phase segregation portion 30, and the relatively hard surface layer 10 forms the outer periphery of the ceramic sphere 1 in the portion removed by polishing in the polishing process of the ceramic sphere 1. This makes it possible to improve the polishing efficiency of the ceramic sphere 1 while protecting the surface of the ceramic sphere 1.

[0035] Furthermore, in the ceramic sphere 1 of this embodiment, the thickness d30 of the glass phase segregation portion 30 is 40 μm or less, and the relatively brittle glass phase segregation portion 30 is thin. This makes the glass phase segregation portion 30 more brittle during polishing in the polishing process of the ceramic sphere 1, thereby improving the polishing efficiency of the ceramic sphere 1.

[0036] Furthermore, in the ceramic sphere 1 of this embodiment, the size of the glass phase contained in the glass phase segregation portion 30 is larger than the size of the glass phase contained in the surface layer portion 10 or the central portion 20. As a result, the glass phase segregation portion 30 is likely to be more brittle than the surface layer portion 10 or the central portion 20. Therefore, when the ceramic sphere 1 is polished in the polishing process of the ceramic sphere 1, the glass phase segregation portion 30 is more fragile, and the surface layer portion 10 and the glass phase segregation portion 30 can be more easily separated from the central portion 20. This further improves the polishing efficiency of the ceramic sphere 1.

[0037] Furthermore, because the ceramic sphere 1 of this embodiment is made of silicon nitride, the center portion 20 is relatively hard and has excellent thermal conductivity. This allows the ceramic balls manufactured by polishing the surface of the ceramic sphere 1 to be used in a wide range of technical fields, taking advantage of these characteristics of silicon nitride.

[0038] <Modification of this embodiment> The present invention is not limited to the above-described embodiment, and can be embodied in various forms without departing from the spirit of the invention. For example, the following modifications are also possible.

[0039] [Variation 1] In the above-described embodiment, the sum of the thickness d10 of the surface layer portion 10 in the radial direction of the ceramic sphere 1 and the thickness d30 of the glass phase segregation portion 30 is set to 11% or less of the radius of the ceramic sphere 1. However, the relationship between the thickness of the surface layer portion, the thickness of the glass phase segregation portion, and the radius of the ceramic sphere is not limited to this. It is sufficient that the sum of the thickness of the surface layer portion and the thickness of the glass phase segregation portion is included in the polishing allowance of the ceramic sphere.

[0040] [Variation 2] In the above-described embodiment, the thickness of the surface layer portion 10 in the radial direction of the ceramic sphere 1 is set to 10% or more and less than 100% of the sum of the thickness of the surface layer portion 10 in the radial direction of the ceramic sphere 1 and the thickness of the glass phase segregation portion 30. The relationship between the thickness of the surface layer portion and the thickness of the glass phase segregation portion is not limited to this. If the thickness of the glass phase segregation portion is less than 10% of the sum of the thickness of the surface layer portion and the thickness of the glass phase segregation portion, polishing becomes difficult and polishing efficiency may be somewhat reduced. Therefore, it is desirable that the thickness be 10% or more.

[0041] [Variation 3] In the above-described embodiment, the thickness d30 of the glass phase segregation portion 30 in the radial direction of the ceramic element sphere 1 is set to 40 μm or less. The thickness of the glass phase segregation portion 30 may be greater than 40 μm, but if the thickness is too large, polishing becomes difficult and polishing efficiency may decrease somewhat. Therefore, the thickness is preferably 40 μm or less.

[0042] [Variation 4] In the above-described embodiment, the area of ​​one glass phase in the cross section of the surface layer portion 10 or the central portion 20 of the ceramic sphere 1 passing through the center C1 is 0.2 μm 2 The area of ​​one glass phase in the cross section of the glass phase segregation portion 30 is 0.2 μm 2The area of ​​one glass phase in the cross section of the surface layer portion 10 or the central portion 20 and the area of ​​one glass phase in the cross section of the glass phase segregation portion 30 are not limited to these values. However, it is desirable for the area of ​​one glass phase in the cross section of the surface layer portion 10 or the central portion 20 to be smaller than the area of ​​one glass phase in the cross section of the glass phase segregation portion 30, because this makes the glass phase segregation portion 30 a more brittle layer, thereby improving the polishing efficiency of the ceramic blank sphere 1.

[0043] [Variation 5] In the above-described embodiment, the ceramic sphere 1 is made of silicon nitride. However, the material for forming the ceramic sphere 1 is not limited to this. The ceramic sphere 1 may be made of a material other than silicon nitride.

[0044] [Variation 6] In the above embodiment, the ceramic ball obtained by polishing the surface of the ceramic base ball 1 is used as, for example, a bearing ball provided in a bearing. However, the technical field to which the ceramic ball is applied is not limited to this.

[0045] This aspect has been described above based on embodiments and modifications. However, the above-described embodiments are intended to facilitate understanding of this aspect and are not intended to limit this aspect. This aspect may be modified or improved without departing from the spirit and scope of the claims, and equivalents thereof are included in this aspect. Furthermore, if a technical feature is not described as essential in this specification, it may be deleted as appropriate.

[0046] <Application example 1> A ceramic element ball, a surface layer portion located on the outer periphery of the ceramic element sphere; a central portion located inside the surface portion; a glass phase segregation portion located between the surface layer portion and the central portion, the glass phase segregation portion containing a larger amount of glass phase than either the surface layer portion or the central portion, Ceramic ball. <Application example 2> The ceramic sphere according to Application Example 1, the sum of the thickness of the surface layer portion and the thickness of the glass phase segregation portion in the radial direction of the ceramic element sphere is 11% or less of the radius of the ceramic element sphere. Ceramic ball. <Application example 3> The ceramic sphere according to Application Example 1 or Application Example 2, a thickness of the surface layer portion in the radial direction of the ceramic element sphere being 10% or more and less than 100% of the sum of the thickness of the surface layer portion in the radial direction of the ceramic element sphere and the thickness of the glass phase segregation portion. Ceramic ball. <Application Example 4> The ceramic sphere according to any one of Application Examples 1 to 3, The thickness of the glass phase segregation portion in the radial direction of the ceramic element sphere is 40 μm or less. Ceramic ball. <Application example 5> The ceramic sphere according to any one of Application Examples 1 to 4, the surface layer portion, the glass phase segregation portion, and the central portion each have a plurality of ceramic crystal grains and the glass phase formed between the ceramic crystal grains, In a cross section passing through the center of the ceramic element sphere, The area of ​​one of the glass phases in the cross section of the surface layer portion or the central portion is 0.2 μm 2 Smaller, The area of ​​one of the glass phases in the cross section of the glass phase segregation portion is 0.2 μm 2 The above is characterized by the above. Ceramic ball. <Application Example 6> The ceramic sphere according to any one of Application Examples 1 to 5, It is characterized in that it is formed of silicon nitride. Ceramic ball. [Explanation of symbols]

[0047] 1...Ceramic ball 10...Surface layer 20...Central part 30...Glass phase segregation area C10, C30...ceramic crystal particles Pv10, Pv30...glass phase

Claims

1. A ceramic element ball, a surface layer portion located on the outer periphery of the ceramic element sphere; a central portion located inside the surface portion; a glass phase segregation portion located between the surface layer portion and the central portion, the glass phase segregation portion containing a larger amount of glass phase than either the surface layer portion or the central portion, Ceramic ball.

2. 2. The ceramic element sphere according to claim 1, a sum of a thickness of the surface layer portion and a thickness of the glass phase segregation portion in a radial direction of the ceramic element sphere being 11% or less of a radius of the ceramic element sphere; Ceramic ball.

3. 3. The ceramic sphere according to claim 2, a thickness of the surface layer portion in the radial direction of the ceramic element sphere being 10% or more and less than 100% of a sum of a thickness of the surface layer portion in the radial direction of the ceramic element sphere and a thickness of the glass phase segregation portion. Ceramic ball.

4. The ceramic sphere according to claim 1 or 2, a thickness of the glass phase segregated portion in the radial direction of the ceramic element sphere being 40 μm or less; Ceramic ball.

5. The ceramic sphere according to claim 1 or 2, the surface layer portion, the glass phase segregation portion, and the central portion each have a plurality of ceramic crystal grains and the glass phase formed between the ceramic crystal grains, In a cross section passing through the center of the ceramic element sphere, The area of ​​one of the glass phases in the cross section of the surface layer portion or the central portion is 0.2 μm 2 Smaller, The area of ​​one of the glass phases in the cross section of the glass phase segregation portion is 0.2 μm 2 The above is characterized by the above. Ceramic ball.

6. The ceramic sphere according to claim 1 or 2, It is characterized in that it is formed of silicon nitride. Ceramic ball.

Images