JP5268565B2 - Grinding media particles, grinding media and ceramic powder grinding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a medium particle for crushing, a medium for crushing and a method of crushing a ceramic powder which enable crushing a ceramic powder efficiently with such a range of distribution of particle sizes as to cope with e.g. recent requirements for improvement of characteristics of electronic part elements. <P>SOLUTION: The medium particle 1 is spherical and is used to crush a ceramic powder. On the surface of the medium particle 1, circular plane portions 1a are formed at six positions arranged at nearly equal intervals on a large circle A and at six positions arranged at nearly equal intervals on each of two small circles B located in the middle of hemispheres divided by the large circle A. Since a ceramic powder can be efficiently held between the plane portions 1a of the medium particles 1 for crushing and crushed, achieving high crushing efficiency and enabling crushing while controlling the range of distribution of particle sizes. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a pulverizing medium particle used for pulverizing a ceramic powder in contact with the ceramic powder, a pulverizing medium containing the pulverizing medium particle, and a method for pulverizing the ceramic powder.

  Electronic component elements such as ceramic multilayer capacitors and ceramic piezoelectric elements are formed by attaching a predetermined conductor pattern such as a capacitor electrode to an insulating base made of a ceramic sintered body such as barium titanate.

  Such a ceramic sintered body is made of a plurality of ceramic greens prepared by pulverizing a raw ceramic powder with a pulverizer to a predetermined particle size and then forming the ceramic powder into a sheet with an organic solvent and a binder. It is produced by laminating sheets and firing them. The conductor pattern is formed by applying a metal paste such as nickel or copper to a ceramic green sheet in a predetermined pattern and simultaneously firing the laminated body of ceramic green sheets.

The pulverization of the ceramic powder is generally performed by contacting (collising) the pulverizing medium particles made of a zirconium oxide sintered body, an aluminum oxide sintered body, etc. with the ceramic powder while moving such as vibration and rotation. . Specifically, a pulverizing medium obtained by collecting a large amount of pulverizing medium particles is mixed with ceramic powder in a mill such as a vibration mill or a rotating mill, and the ceramic powder sandwiched between the pulverizing medium particles is mixed with the mill. It is carried out by generating a stress such as a shearing stress by friction or the like accompanying the vibration or rotation of the material and grinding.
JP 2001-205123 A

  The conventional pulverizing medium has a problem that it is difficult to efficiently pulverize ceramic powder while suppressing the distribution range of particle diameters. This is because the pulverizing medium particles are spherical, for example, when the pulverizing medium particles are filled in the mill, the range in which the pulverizing medium particles contact each other is narrow, and the gap between the particles is relatively wide. For this reason, it is difficult to increase the efficiency of contact between the pulverizing medium particles and the ceramic powder.

  In order to solve such a problem, for example, means for making the pulverizing medium particles into a polyhedron can be considered (for example, see Patent Document 1). However, in recent years, there has been a demand for improvement in characteristics such as further improvement in insulation in a multilayer ceramic capacitor which is an electronic component element, for example. In order to improve such characteristics, it has become necessary to pulverize ceramic powder more efficiently and to sharpen the pulverized particle size distribution (narrow the distribution range). And when the pulverizing medium particles are simply polyhedral, when the pulverizing medium is filled in a mill or the like, the planar portions of the adjacent pulverizing medium particles are not necessarily opposed to each other. There is a problem that it may be difficult to increase the efficiency of pulverizing the ceramic powder to such an extent that it can cope with such conditions.

  The present invention has been devised in view of such conventional problems, and the purpose thereof is to efficiently produce ceramic powder to such an extent that it can cope with, for example, improvement in characteristics required for recent electronic component elements. An object of the present invention is to provide a pulverizing medium particle, a pulverizing medium, and a method for pulverizing ceramic powder, which can be pulverized while suppressing the diameter distribution range.

  The pulverizing medium particles of the present invention are spherical pulverizing medium particles for pulverizing the ceramic powder, and the surface has a circular plane portion arranged at approximately equal intervals on one great circle. , And arranged on six small circles arranged at approximately equal intervals on two small circles parallel to the great circle located in the middle of each of the hemispherical parts on both sides divided by the great circle. It is a feature.

  Further, in the above-described configuration, the pulverizing medium particles of the present invention are arranged such that the plane portion on the small circle is on an arc connecting the plane portions adjacent to each other on the great circle and the apex of the hemisphere portion. It is characterized by being.

  The pulverizing medium of the present invention is a pulverizing medium composed of spherical pulverizing medium particles for pulverizing ceramic powder, and contains 10% by volume or more of the pulverizing medium particles of the present invention having any one of the above configurations. It is characterized by.

  Further, in the above-described configuration, the grinding medium of the present invention has, as the spherical grinding media particles, six locations in which circular planar portions are arranged at almost equal intervals on one great circle, and the great circle. Including pulverizing medium particles arranged at three points arranged at approximately equal intervals on two small circles parallel to the great circle located in the middle of each of the divided hemispherical parts. It is a feature.

  The ceramic powder pulverization method of the present invention is characterized in that the ceramic powder is pulverized in contact with the pulverization medium of the present invention having any one of the above structures in a pulverizer.

  According to the pulverizing medium particles of the present invention, each of the six portions where the circular flat surface portion is arranged on the surface of the large circle at almost equal intervals and the hemispherical portions on both sides divided by the large circle are provided. Since it is arranged in six places arranged at approximately equal intervals on two small circles parallel to the great circle located in the middle, such grinding media particles are used for grinding in the grinding device. When used as a medium, in one pulverizing medium particle, the plane portions are located at almost equal intervals in six places in the lateral direction and six places in the upper and lower oblique (small circle) directions. Here, in general, when a spherical object is to be arranged with a high density, other spherical objects are positioned laterally and vertically obliquely with respect to one spherical object. Therefore, the flat portions can be more reliably and efficiently brought into contact with each other between the pulverizing medium particles that are in contact with each other in the lateral direction and the oblique direction. Therefore, the ceramic powder can be effectively pulverized by applying a stress such as a shearing stress accompanying friction between the flat portions of the pulverizing medium particles and effectively applying the ceramic powder.

  Further, according to the pulverizing medium particle of the present invention, in the above configuration, the planar portion on the small circle is on an arc connecting between the planar portions adjacent to each other on the great circle and the apex of the hemispherical portion. When the spherical grinding media particles are arranged so as to form a so-called body-centered cubic or face-centered cubic lattice, the plane portions of each other are just opposite each other. It will be in a suitable position. Therefore, it is effective in increasing the packing density of the pulverizing medium particles in the pulverizing apparatus, and the ceramic powder can be pulverized more efficiently between the flat portions. Therefore, in this case, it is possible to provide pulverizing medium particles capable of pulverizing the ceramic powder more efficiently and suppressing the particle size distribution range.

  According to the pulverizing medium of the present invention, a pulverizing medium comprising spherical pulverizing medium particles for pulverizing the ceramic powder, the pulverizing medium particles of the present invention having any one of the above structures being 10% by volume or more. Therefore, a pulverizing medium capable of efficiently pulverizing the ceramic powder and suppressing the particle size distribution range can be provided.

  Further, in the above-described configuration, the grinding medium of the present invention has, as the spherical grinding media particles, six locations in which circular planar portions are arranged at almost equal intervals on one great circle, and the great circle. In the case of including pulverizing medium particles arranged in three places arranged at approximately equal intervals on two small circles parallel to the great circle located in the middle of each of the divided hemispherical parts. Can also be used as a pulverizing medium capable of increasing the efficiency and allowing the ceramic powder to be pulverized over a longer period of time.

  That is, the pulverizing medium particles in which the twelve flat portions are arranged, like the pulverizing medium particles in which the flat portions having the above-described configuration are arranged, pulverize the ceramic powder as compared with the spherical pulverizing medium particles. Can be performed efficiently. In addition, there is a possibility that a new flat portion may be formed between the flat portions arranged side by side at almost equal intervals on the small circle, due to the contact (friction) between the grinding medium particles. In this case, the pulverizing medium particles having such 12 plane portions (arranged) are newly replaced with the pulverizing medium particles of the present invention having the above-described configuration (the flat portion on the small circle). Can be made to function as 6). Therefore, the pulverizing medium can be stably and efficiently pulverized ceramic powder for a longer period of time.

  According to the method for pulverizing ceramic powder of the present invention, the ceramic powder is pulverized in contact with the pulverizing medium of the present invention having any one of the above structures in a pulverizer, so that the ceramic powder is efficiently dispersed in particle size distribution. It becomes possible to suppress and grind.

  First, the pulverizing medium particles and the pulverizing medium of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 is a perspective view showing an example of an embodiment of pulverizing medium particles of the present invention. In FIG. 1, reference numeral 1 denotes a pulverizing medium particle, and reference numeral 1 a denotes a flat portion disposed on the surface of the pulverizing medium particle 1.

  The pulverizing medium particles 1 are made of a ceramic material having high mechanical strength such as a zirconium oxide sintered body and an aluminum oxide sintered body, and are spherical.

  Further, a large amount of the pulverizing medium particles 1 collected, for example, in a volume ratio of about 2: 1 to 10: 1 with respect to the ceramic powder to be pulverized is a pulverizing medium (not shown). To be used for grinding ceramic powder.

  The pulverization of the ceramic powder by the pulverizing medium particles 1 is performed by mixing the pulverizing medium and the ceramic powder in a pulverizer (not shown) such as a vibration mill or a rotary mill, and vibrating or rotating the mill. It is carried out in contact with the ceramic powder while moving the grinding media. For example, in the case of a vibration mill, a pulverizing medium is filled in a cylindrical mill body, ceramic powder is put into the pulverizing medium, and the mill body is vibrated at high speed to vibrate the pulverizing medium. . Along with this vibration, a shearing stress accompanying friction is generated in the ceramic powder sandwiched between the grinding medium particles 1, and the ceramic powder is pulverized by this shearing stress. The ceramic powder may be previously kneaded with an organic solvent, a binder or the like to form a slurry.

  Examples of the ceramic powder to be pulverized include various types such as barium titanate, strontium titanate, lead zirconate titanate, and aluminum oxide according to the electronic component element to be manufactured.

Such a pulverizing medium particle 1 and a pulverizing medium can be manufactured as follows, for example. That is, first, an organic binder and a solvent are added to a raw material powder containing 95.5 to 97.4% by mass of zirconium oxide and 2.6 to 4.5% by mass of yttrium oxide, kneaded, and then dried and granulated using a spray dryer. . Next, after this granulated material is filled into a spherical molding die, a load of, for example, 1 ton / cm ² is applied to obtain a press-molded body. And it can manufacture by baking this molded object at about 1200-1550 degreeC.

  This pulverizing medium particle 1 has six portions in which a circular flat surface portion 1a is arranged on the surface of a large circle A at almost equal intervals, and hemispherical portions on both sides divided by the large circle A (no symbol). ) On two small circles B parallel to the great circle A located in the middle of each of them, respectively, at six locations arranged at almost equal intervals. That is, when the spherical pulverizing medium particles 1 are placed in a pulverizing apparatus such as a vibration mill as a pulverizing medium, for example, as shown in FIGS. The plane portions 1a are located at six locations in the horizontal direction and six locations in the diagonal direction (small circle B). Therefore, the flat portions 1a can efficiently contact each other between the pulverizing medium particles 1 that are in contact with each other in the lateral direction and the oblique direction. 2A and 2B are a plan view (perspective view) schematically showing a state in which the pulverizing medium particles 1 of the present invention are put in a pulverizing apparatus such as a vibration mill as a pulverizing medium, respectively. It is a side view. In FIG. 2, the same parts as those in FIG.

  Here, in general, when a spherical object is to be arranged with a high density, normally, another spherical object is positioned laterally and vertically obliquely with respect to one spherical object. And the plane part 1a of the medium particle 1 for grinding | pulverization of this invention is located in such a position. Therefore, the ceramic powder can be pulverized by applying a stress such as a shearing stress associated with friction between the flat portions 1a of the pulverizing medium particles 1 by effectively sandwiching the ceramic powder (no symbol).

  Further, since the pulverizing medium particles 1 having the flat portion 1a are spherical in shape, and the surface of the portion other than the flat portion 1a is spherical, compared to a case where it is a polyhedron, A certain gap is secured between the pulverizing medium particles 1, and the slurry of the ceramic powder can be moved through the gap. Therefore, for example, when the pulverizing medium particles 1 are filled in the vibration mill as a pulverizing medium, when the ceramic powder (slurry or the like) is charged into the pulverizing medium from the upper side, The ceramic powder can be moved smoothly toward the medium by gravity, and pulverized one after another.

  Such a flat portion 1a is formed by, for example, filling the grinding media particles 1 as grinding media in a vibration mill and grinding the contact surfaces of the grinding media particles 1 by vibrating them at high speed. And can be formed on the surface of the pulverizing medium particles 1 in the above-described arrangement. In this case, the contact surfaces of the pulverizing medium particles 1 filled in the mill were divided by six large circles A and six locations arranged on one horizontal large circle A in one pulverizing medium particle 1. Three points are arranged on the two small circles B parallel to the great circle A located in the middle of each of the hemispherical portions on both sides, and are arranged at almost equal intervals, and the contact surface is ground to obtain the flat portion 1a. Become. Also, the three contact surfaces on the small circle B are ground by the movement such as rotation of the pulverized solvent body particles 1 accompanying the vibration, and the plane portion 1a is formed. Therefore, six plane portions 1a can be formed on the small circle B.

  Further, in such a pulverizing medium particle 1, the flat surface portion 1 a on the small circle B is arranged on an arc connecting between the adjacent flat surface portions 1 a on the large circle A and the apex of the hemispherical portion. In such a case, when the spherical pulverizing medium particles 1 are arranged so as to constitute a so-called body-centered cubic or face-centered cubic lattice, the plane portions 1a are just facing each other. become. The position when a plurality of spherical objects are arranged with increased density corresponds to the lattice points of the above-mentioned body-centered cubic lattice or face-centered cubic lattice. Therefore, it is effective in increasing the packing density of the pulverizing medium particles 1 in the pulverizing apparatus, and the ceramic powder can be pulverized more efficiently between the flat portions 1a. Therefore, in this case, it is possible to obtain the pulverizing medium particles 1 that can pulverize the ceramic powder more efficiently while suppressing the particle size distribution range.

  Moreover, it is preferable that the external dimensions of the pulverizing medium particles 1 be sufficiently large, about 500 to 50000 times the external dimensions of the ceramic powder to be pulverized. If the size is such a size, the size of the pulverizing medium particles 1 is sufficiently larger than the size of the ceramic powder to be pulverized. be able to.

  Further, for example, if the ceramic powder is a material having a high dielectric constant such as barium titanate used for a multilayer ceramic capacitor, the external dimensions of the grinding medium particles 1 are set to about 3 to 7 mm. What is necessary is just to grind | pulverize the ceramic (barium titanate) powder whose dimension is about 0.2-2 micrometers. This is because, for example, barium titanate powder can be pulverized satisfactorily in a range of about 0.1 to 0.7 [mu] m so that the particle size is normally distributed. The pulverized barium titanate powder can be used to produce an insulating base (dielectric layer of a multilayer ceramic capacitor) having good sinterability and high insulating properties.

  The plane portions 1a are arranged on the great circle A and the small circle B at almost equal intervals. In order to obtain the same pulverization effect in each plane portion 1a, the areas and shapes of the plane portions 1a are the same. It is preferable that it is a thing of a grade. If the area and shape (circularity etc.) of the six plane portions 1a in the great circle A and the small circle B are approximately the same, the plane portions 1a are arranged at intervals of about 60 degrees with respect to each other at the central angle. do it. In addition, the plane part 1a is not limited to a circular shape, and may be an elliptical shape or a portion having a concavity and convexity on a part of the circumference.

  The pulverizing medium of the present invention contains 10 or more volumes of the pulverizing medium particles 1 configured as described above. That is, the pulverization medium of the present invention using the pulverization medium particles 1 of the present invention described above does not necessarily have to have the flat portion 1a having the above-described configuration, but the pulverization efficiency is improved. In order to improve effectively, it is necessary to contain 10 volume% or more of the grinding | pulverization medium particle | grains 1 which have the plane part 1a of the said structure. In this case, the pulverization medium other than the pulverization medium particles 1 having the flat surface portion 1a is spherical (including one having irregularities on a part of the surface).

  Note that, in such a pulverizing medium, when the flat portions 1a of the pulverizing medium particles 1 are adjacent to each other, the occupied space in the vibration device is reduced. In other words, since the position energy is stable, once adjacent, there is a tendency to maintain the adjacent. Then, by adding kinetic energy such as vibration to the vibration medium, rearrangement of the entire grinding medium particles including the grinding medium particles 1 of the present invention occurs, and the grinding of the present invention is performed as time passes for applying the vibration. A gathering portion (not shown) in which many medium particles 1 are gathered is formed. For example, in the case of a vibration mill of a vertical vibration type (a type that vibrates in the vertical direction), the layer of the pulverizing medium particles 1 of the present invention is formed in the mill body. The ceramic powder can be efficiently pulverized by this layer.

  The ceramic powder (slurry) is, for example, introduced from the upper part of the mill body and taken out from the lower part. When this operation is repeated (circulated), the slurry forms a plurality of layers of the above-mentioned grinding media particles 1 of the present invention. Since it passes through once, it can grind | pulverize to a more uniform particle size. Further, in forming such a layer of the pulverizing medium particles 1 of the present invention, it is sufficient that the pulverizing medium particles 1 are contained in an amount of 10% by volume or more. It is still desirable if it is.

  Further, in this pulverizing medium, as a spherical shape other than the pulverizing medium particles 1, circular flat portions 2a as shown in FIG. 3, for example, are arranged on one great circle A at approximately equal intervals. 3 points each arranged at approximately equal intervals on two small circles B parallel to the large circle A located in the middle of each portion and the hemispherical part (not indicated) on both sides divided by the large circle A The following effects can be obtained when the pulverizing medium particles 2 are included. FIG. 3 is a perspective view showing an example of pulverizing medium particles 2 used together with the pulverizing medium particles 1 in the pulverizing medium of the present invention.

  That is, in this way, the pulverizing medium particles 2 in which the planar portions 2a are arranged at twelve locations are laterally and obliquely used when used as a pulverizing medium in the pulverizing apparatus, similarly to the pulverizing medium particles 1 described above. Since the other pulverizing medium particles 2 and the respective flat portions 2a face each other in the vertical direction, the ceramic powder can be pulverized more efficiently than the spherical pulverizing medium particles.

  Further, between the flat portions 2a arranged on the small circle B at approximately equal intervals, a new flat portion (not shown in FIG. 3) is brought into contact with the pulverizing medium particles 2 (friction). May be formed. In this case, the pulverizing medium particles 2 in which the twelve planar portions 2a are arranged (arranged) are newly replaced with the pulverizing medium particles having the above-described configuration (the planar portion on the small circle). 1a can be made to function as 1). Therefore, the pulverizing medium can be stably and efficiently pulverized ceramic powder for a longer period of time.

  The method for pulverizing ceramic powder of the present invention is to pulverize ceramic powder by bringing it into contact with the pulverizing medium of the present invention having any one of the above structures in a pulverizer. According to such a pulverizing method, since the pulverizing medium of the present invention having the above-described configuration is used, the ceramic powder can be efficiently pulverized while suppressing the particle size distribution.

  For example, when the ceramic powder is a barium titanate powder used for a multilayer ceramic capacitor and is pulverized using a vibration mill, the following may be performed.

  As a grinding medium, a grinding medium comprising spherical grinding media particles comprising 10% by volume or more of grinding media particles 1 having a plane portion 1a made of a zirconium oxide sintered body is used. The inside of the shaped mill body is filled so that it is almost filled. Then, the slurry produced by kneading the ceramic powder together with the organic solvent and the binder is put into the mill from the upper part of the mill body while vibrating the mill body at high speed so that the grinding media particles 1 are rubbed with each other. . At this time, the ceramic powder is sandwiched and brought into contact with the pulverizing medium particles 1, and the ceramic powder is pulverized by the shear stress generated by friction with the pulverizing medium particles 1. The pulverized ceramic particles are sequentially taken out from a take-out port provided on the lower side of the mill main body, and are formed into a ceramic green sheet by using, for example, a tape forming method.

  In this case, the external dimensions of the grinding medium particles 1 are about 5 mm in diameter, and the ceramic powder has a diameter before grinding of about 0.1 to 5 μm, for example. The time required for pulverization is, for example, about 10 to 15 hours under the above conditions.

  In order to confirm the effect of the grinding medium of the present invention, the following experiment was conducted. In addition, barium titanate powder was used as the ceramic powder, spherical particles made of zirconium oxide were used as the grinding media particles, and a vibration mill (longitudinal vibration type) was used as the grinding device. The pulverizing medium contains 30% by volume of pulverizing medium particles on which the flat portion of the present invention is arranged.

First, about 65 kg of the grinding medium was put in a vibration mill, and then the vibration mill was vibrated so that the grinding medium particles were in closer contact with each other. Moreover, about the barium titanate powder (a particle size is about 1-2 micrometers), it knead | mixed with the organic solvent and the binder as a slurry, and this slurry was supplied into the mill from 16 kg upper side. Then, the vibration mill was vibrated for about 15 hours under conditions of an acceleration of 5 m / s ² and a displacement of 0.1 mm to grind the ceramic powder, and the particle size distribution of the ground ceramic powder was measured with a laser diffraction scattering particle size meter.

  Further, as a comparative example, pulverization was performed in the same manner as described above using only a spherical pulverizing medium having no flat portion. The measurement results are shown in Table 1.

  The comparison of the particle size variation is based on the particle size distribution of the ceramic powder from the smallest particle size of 10% to the particle size of D10 (μm), 50% (that is, the median). D50 (μm) was carried out by a method in which the particle diameter of the 90% position was D90 (μm).

  As can be seen from the results shown in Table 1, the difference in particle diameter is 0.12 μm to 0.17 μm with respect to D50 indicating the center of the distribution of both D10 indicating the fine powder portion and D90 indicating the coarse powder portion of the ceramic powder distribution. The difference is small. In other words, the distribution range is narrow. On the other hand, in the comparative example, D50 was 0.50 μm, which was the same as the example, whereas D10 was 0.29 μm, D90 was 0.96 μm, and the difference in particle size was as large as 0.21 to 0.46 μm (Example) Compared to about 1.2 to 3.8 times). That is, in the examples, compared to the comparative example, both fine powder and coarse powder were distributed in a particle size close to that of the intermediate particle size distribution, and the grinding medium of the present invention was used. In this case, both fine powder and coarse powder were less than in the comparative example, and the particle size distribution was sharp. On the other hand, in the comparative example, both the fine powder and the coarse powder have a large difference from the median, and the particle size is dispersed in a wide range, and the dispersion of the particle size of the ceramic powder is suppressed (the particle size distribution is sharpened). ) I found it difficult to grind.

  Further, dielectric loss values were measured and high-temperature load tests were performed on the insulating bases of electronic component elements manufactured using the pulverized ceramic powder. As a result, the dielectric loss value (tan δ (%)) was about 2.0% when the ceramic powder according to the example was used, whereas it was about 3.6% when the ceramic powder according to the comparative example was used. became. Thus, it was found that when the ceramic powder pulverized using the pulverizing medium of the present invention is used, it is possible to produce an insulating substrate having a dielectric loss value lower than that of the conventional one.

  In the high temperature load test, the insulating base is composed of a laminate of insulating layers having a thickness of about 3 μm, and rectangular conductors made of a nickel sintered material are respectively formed on the upper and lower surfaces of the insulating layer. This was carried out by confirming the presence or absence of an electrical short circuit between adjacent conductors after performing a high-temperature load test for 1000 hours at 125 ° C. and a bias voltage of 12.5 V. As a result, dielectric breakdown did not occur between the conductors when using the ceramic powder pulverized using the pulverizing medium of the example, whereas between the adjacent conductors when using the ceramic powder according to the comparative example Insulation breakdown occurred.

  As described above, according to the pulverizing medium of the present invention, ceramic powder is efficiently pulverized to a degree that can cope with, for example, improvement in characteristics required for recent electronic component elements, while suppressing the particle size distribution range. We were able to.

It is a perspective view which shows an example of embodiment of the medium particle for grinding | pulverization of this invention. (A) is a top view which shows typically the state which put the medium particle for grinding | pulverization shown in FIG. 1 in the grinding | pulverization apparatus, (b) is the side view. It is a perspective view which shows an example of the pulverization medium particle which comprises the pulverization medium of this invention.

Explanation of symbols

1, 2... Medium particles for grinding 1a, 2a,.

Claims (5)

Spherical pulverizing medium particles for pulverizing ceramic powder, and having a circular plane portion on the surface arranged at approximately equal intervals on one great circle, and both sides divided by the great circle A pulverizing medium particle, characterized in that it is arranged at six places arranged at approximately equal intervals on two small circles parallel to the great circle located in the middle of each hemispherical portion. 2. The pulverizing apparatus according to claim 1, wherein the planar portion on the small circle is disposed on an arc connecting between the planar portions adjacent to each other on the great circle and an apex of the hemispherical portion. Medium particles. A pulverizing medium comprising spherical pulverizing medium particles for pulverizing ceramic powder, the pulverizing medium comprising 10% by volume or more of the pulverizing medium particles according to claim 1 or 2. As the spherical pulverizing medium particles, circular plane portions are located in the middle of each of six locations arranged on a single great circle at approximately equal intervals and the hemispherical portions on both sides divided by the great circle. The pulverizing medium according to claim 3, comprising pulverizing medium particles arranged at three points arranged at approximately equal intervals on two small circles parallel to the great circle. A method for pulverizing ceramic powder, wherein the ceramic powder is pulverized in contact with the pulverizing medium according to claim 3 or 4 in a pulverizer.

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