JPH06321620A - High toughness ceramic material - Google Patents

Abstract

PURPOSE:To obtain a ceramic material excellent in toughness, wear resistance, etc., containing a specified amt. of distributed fine spherical pores by sintering the ceramic material at lower temp. for a shorter time than a conventional method. CONSTITUTION:In the production process of compacting ceramic material (e.g. silicon nitride), the sintering temp. is controlled lower than a conventional method by 20-50 deg.C and the sintering time is decreased than a conventional method by 0.5-4.5 hours. By this method, a high toughness ceramic material containing spherical pores of <=3mum diameter distributed at the ratio of 1-3vol.% to the whole ceramic sintered body can be obtd. As for the distribution state of pores in a high toughness ceramic material, uneven distribution of pores in the ceramic sintered body is preferable since pores have a pinning effect for cracks. To obtain uneven distribution of pores, a sintering aid having high melting point is added to that the compacted body is locally fast sintered and locally slowly sintered.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high toughness ceramic material, and in particular, to generate an appropriate amount of pores having a shape and size in ceramics that do not affect the strength derived from segregation or crystal growth. Thus, the present invention relates to a high toughness ceramic material having a fracture toughness value significantly improved as compared with conventional ceramics.

[0002]

2. Description of the Related Art In recent years,
As technology advances, materials that can be used in more harsh environments are needed.

Ceramics have been attracting attention due to their excellent functions and characteristics such as high temperature heat resistance, corrosion resistance, and abrasion resistance, and have been vigorously studied so far. In particular, ceramics having high strength and very excellent heat resistance. Materials are gradually being used in various fields, such as in-vehicle engine parts and members, instead of metal materials.

However, the fracture toughness value of ceramics is much lower than that of metal, and the fracture is brittle. Once the fracture starts somewhere, it progresses catastrophically without stopping. That is, since ceramics are brittle materials, they lack reliability and safety. This is the biggest problem of ceramics, and many researchers have attempted to increase the toughness of the ceramics, and have researched high toughness materials such as particle dispersion type, whisker reinforced type and long fiber reinforced type.

For example, Al ₂ O ₃ / ZrO ₂ , ZnO
/ ZrO ₂ , Si ₃ N ₄ / SiC (Tomita, Toughening of Ceramics by Particle Dispersion, Ceramics, 21, 198
6), then Si ₃ N ₄ / SiC _(W) , Al ₂ O ₃ / SiC
_(W) , Al ₂ O ₃ / ZrO ₂ / SiC _(W) (Inoue et al. Toughening ceramics by whiskers, ceramics, 2
1, 1986), and in SiC / SiC fiber,
High toughness has been achieved by using SiC / carbon fiber, Si ₃ N ₄ / carbon fiber (Shinbara, Superfine Ceramics Control Technology Handbook, Science Forum) and the like.

However, in each of the above-mentioned methods, since a reinforcing component is added, there is a possibility that the characteristics of conventional ceramics may be impaired in some cases, and there is a drawback that the production is not easy because it is not a single material.

On the other hand, in the conventional sintering of ceramics, the pores remaining in the sintered body are regarded as defects, and a study was made with a view to reducing the porosity and obtaining a dense sintered body. Development has been advanced. Therefore, although a single ceramic material can provide a dense and high-strength sintered body, the present situation is that the fracture toughness value does not increase.

The present invention has been made in view of the above circumstances, and it is possible to increase the toughness of a single material without adding a reinforcing component such as the high toughness material, and it is extremely easy to manufacture the high toughness ceramic material. The purpose is to provide.

[0009]

The high toughness ceramic material of the present invention is characterized in that spherical pores having a diameter of 3 .mu.m or less are dispersed in the whole ceramic fired body at a volume ratio of 1 to 3%. (Claim 1).

The ceramic material of the present invention may be of any type as long as it is a ceramic structural material which has been conventionally used. In particular, silicon nitride (Si ₃ N ₄ ),
Alumina (Al ₂ O ₃ ), mullite (3Al ₂ O ₃・ 2Si
O ₂ ) is preferable (claims 3 to 5).

The crystal grain size of the ceramic sintered body is 0.3 to 2.7 μm for Si ₃ N ₄ , 2.0 to 6.5 μm for Al ₂ O ₃ , and 3Al ₂ O ₃ .2SiO ₂ 1.
The range of 5 to 7.2 μm is desirable, especially Si
₃ N ₄ is 0.5 to 0.9 μm, and Al ₂ O ₃ is 3.3 to 5.8.
It is more desirable from the viewpoint of strength that the thickness of ₃ μm and 3Al ₂ O ₃ .2SiO ₂ be in the range of 3.2 to 6.4 μm.

The high toughness ceramic material of the present invention has a firing temperature of about 20 to 50 ° C. lower than that of the prior art and a firing time of about 0.5 to 4.5 than the prior art in the process of densifying and manufacturing the conventional ceramic material. Only by shortening the time, it is possible to manufacture in exactly the same manner as the conventional manufacturing method.

[0013] Also, hot pressing sintering, HI
When P sintering is used, the pressure condition is 3-10
Similarly, it can be manufactured by setting it to be lower by about%.

As for the distribution of pores in the high toughness ceramic material of the present invention, it is preferable that the pores are distributed non-uniformly in the ceramic sintered body because the pinning effect of cracks works (claim 2). .

In order to distribute the pores non-uniformly in the ceramic sintered body, a sintering aid having a high melting point is added to locally form a fast sintering portion and a slow sintering portion,
This can be achieved by locally changing the situation in which the pores are discharged and moved. Specifically, as the high melting point sintering aid, Nd ₂ O ₃ , Al ₂ O ₃ , La ₂ O ₃ , CeO ₂ , Y ₂ O _{3 can be used.}
However, Nd ₂ O ₃ and La ₂ O ₃ are particularly preferable, and the addition amount thereof is preferably about 8 to 12 wt% with respect to the total amount.

[0016]

The present inventors have found that the size of the pores remaining in the ceramic sintered body, which has been regarded as a defect in the past,
The present invention was devised by discovering the fact that the fracture toughness value can be increased by controlling the shape and amount. That is, the fracture toughness value can be improved by intentionally generating an appropriate amount of pores having a shape and size that have not been achieved until now and that do not affect the strength derived from segregation or crystal growth. is there.

The pores generated in the present invention are i) a shape that does not affect the strength, ii) a size that does not affect the strength, and iii) an extent that does not affect the strength. Must be in the amount range.

The above items i) to iii) will be described below.

I) Pore shape that does not affect strength In FIG. 1, when the pore diameter is spherical, the stress is isotropically dispersed, whereas when it is not spherical, the stress is distributed in a portion having a small curvature. The stress is concentrated and there is a high possibility of further destruction. Therefore, the shape that does not affect the strength needs to be spherical.

Ii) Pore size that does not affect strength In linear fracture mechanics, when a semi-infinite medium has a crack of length 2a as shown in FIG. 2, this material is destroyed. The required stress σ _f is given by the following equation.

[0021]

[Equation 1]

From the above equation, Table 1 shows the fracture toughness value (K _IC ), bending strength, and 2a of typical conventional ceramic structural materials.

[0023]

[Table 1] It can be seen from Table 1 that the pore size is preferably 3 μm or less so that the bending strength is not affected.

Iii) Range of porosity (porosity) that does not affect strength The relationship between porosity and ceramic strength is empirically given by the following equation. Δf = Δf ₀ exp [−kp] V is a porosity, and k is a dimensionless constant.

From the above equation, the relationship between porosity and strength is as shown in FIG.

From the graph of FIG. 3, the strength sharply decreases from the state where the porosity is 0%, and the decrease rate gradually decreases, and when the porosity exceeds a certain level (Graph-A), the strength is almost the same. The decrease disappears and converges.

However, since the porosity of 0% means a single crystal state, it is not possible in a polycrystalline ceramic, and a porosity of about 1% is inevitable. In fact,
It is empirically clear that many polycrystals have a porosity of about 1 to 3%, but the strength does not decrease so much, and it is considered that the strength is sufficiently higher than the strength at point A in the graph of FIG. Be done.

It can be seen that the pores satisfying the above conditions i) to iii) have no influence on the strength even if they are present in the ceramics. In the present invention, the toughness of ceramics is increased by controlling the amount (porosity) of the generation of such pores.

Next, the factors for improving the fracture toughness value can be roughly classified into the following two. (1) Direct interaction between main crack and dispersed particles (2) Mechanism of forming process zone near the tip of main crack

(1) is the curvature of the leading edge of the main crack, the deflection of the main crack surface, the crack pinning action, etc.
In (2), there are microcracking, stress-induced phase transition, fracture surface crosslinking, and the like.

In the ceramic of the present invention, an appropriate amount of pores having a shape and a size that do not affect the strength derived from segregation or crystal growth are generated in the ceramic.
It is presumed that the factors contributing to the improvement of the fracture toughness are pinning and deflection of cracks due to pores.

Next, FIG. 4 shows the relationship among the porosity, strength and fracture toughness value. Here, the porosity in FIG.
The porosity is in the range defined in iii).

Porosity in ceramics can be regarded as a kind of defects. Therefore, the conventional sintering technology has been advanced in consideration of how to obtain a dense sintered body. However, as described above, as long as the pores remaining in the ceramic have a shape and size that do not affect the strength, pores within a certain range do not affect the strength.

On the other hand, the fracture toughness value also increases as the density increases, but decreases if the pores are kept below a certain level. (Fig.-C point) Because cracks are pinned there if there is an appropriate amount of pores, and proceed while deflecting, but if there are too few pores, the cracks break brittlely without stopping. Because it reaches. Therefore,
There is a range of porosities that minimizes strength loss and has the highest fracture toughness values. (Points A to B in the figure)

In the present invention, by increasing the toughness by controlling the sintering conditions, an appropriate amount of pores having a shape and a size that do not affect the strength are intentionally formed in the ceramic. .

[0036]

Example 1 Si ₃ N ₄ -1 Si ₃ N ₄ raw materials were SN-E10 (center particle size 0.79 μm, α fraction> 95%) manufactured by Ube Industries, Ltd. and SN manufactured by Electrochemical Co., Ltd.
-P21C (center particle size: 0.69 μm, α fraction: 93.1%) was used.

As the sintering aid, E2 was Al ₂ O ₃ (AKP-30 manufactured by Sumitomo Chemical Co., Ltd., central particle size: 0.37 μm) and Y ₂ O.
₃ (Mitsubishi Chemical Co., Ltd. YF, central particle size 1.46 μm) was added at 3 mol% and 5 mol% respectively, or Nd ₂ O ₃ (Nissan Rare Element Chemical Co., Ltd.) and Y ₂ O ₃ (YF) were added at 5 m each.
ol%, 3 mol% each, and P21C contains CeO
₂ (manufactured by Nissan Rare Element Chemicals Co., Ltd.) and Y ₂ O ₃ (YF) at 5 mol% and 3 mol%, respectively, or La ₂ O
₃ (manufactured by Japan Yttrium Co., Ltd.) and Y ₂ O ₃ (YF) were added at 4 mol% and 4 mol% respectively.

The above raw materials were weighed in predetermined amounts as shown in Table 2 and wet-mixed with trichlene (Toa Gosei Co., Ltd., trichlene R) for 16 hours. At this time, as a dispersant, A
LM (Ajinomoto Co., Inc.) is used, and the cobblestone is made of Si ₃ N ₄ , φ
15 mm (Nikkato Co., Ltd.) and the boulder ratio was 1.5.

[0039]

[Table 2]

After wet mixing, it was dried in an oven at 100 ° C. for 18 hours, and then dry pulverization was carried out for 48 hours. At this time, the boulders used in the wet mixing were used in the same ratio. Further, it was passed through a stainless steel sieve having an opening of 500 μm to obtain a kneaded clay.

The kneaded material obtained had a temperature of 1750 ° C. and a pressure of 33.
0 kg / cm ^2, time 1 hour _{(Nd 2 O 3 -Y 2 O} 3 system) or 2 hours _{(Al 2 O 3 -Y 2 O} 3, La 2 O 3 -Y 2 O 3, C
eO ₂ —Y ₂ O ₃ system) HP sintering was performed (No. 1 to No. 1).
4).

As a comparative example, the temperature is 1800 ° C., the pressure is 330 kg / cm ² , the time is 2 hours (Nd ₂ O ₃ —Y ₂ O ₃
System) or 3 hours (Al ₂ O ₃ —Y ₂ O ₃ , La ₂ O ₃ —Y ₂
O ₃ and CeO ₂ —Y ₂ O ₃ system) HP sintered under conditions of porosity less than 1% (No. 5-8), temperature 175
0 ° C., pressure 330 kg / cm ² , time 45 minutes (Nd ₂ O ₃
-Y ₂ O ₃ system) or 90 minutes _{(Al 2 O 3 -Y 2 O} 3, La 2
O ₃ —Y ₂ O ₃ and CeO ₂ —Y ₂ O ₃ system) were also sintered, and HP sintering was performed to make the porosity 4% or more (No. 9 to 12).

The obtained sintered body was evaluated for the shape and size of 100 pores with a scanning electron microscope (S-450, manufactured by Hitachi, Ltd.), and the porosity was measured by an image processing apparatus (Olympus Optical Industry Co., Ltd.). It was calculated from the area ratio of the pores and the dense parts using XL-500). Furthermore, three-point bending strength (JIS R1601) and fracture toughness value (JIS R16
07) was measured.

Table 3 below shows Si ₃ N ₄ of this embodiment and conventional S.
i ₃ shows a characteristic comparison of N _4.

[0045]

[Table 3]

Here, the porosity is a porosity by the Archimedes method, and the porosity is a value measured by using an image analyzer. In the Archimedes method, the porosity is only about 1/10 that of the porosity, while the open pores are assumed to be the pores in the total volume, while the measurement method using the image processing device includes the closed pores. This is because the porosity can be calculated. Hereinafter, in the characteristic table of ceramics, the porosity by the Archimedes method is shown as the porosity, and the porosity using the image processing apparatus is shown as the porosity. (Note that the porosity of 1 to 3% specified in the present invention means the porosity using an image processing apparatus.)

1 to 4 are Si ₃ obtained by this embodiment
N ₄ and 5 to 8 are Si ₃ N having a conventional porosity of less than 1%
_{Is 4} . From Table 3, in the case of this example, the fracture toughness value was significantly improved while the bending strength was almost the same. In particular, Si ₃ N ₄ using Nd ₂ O ₃ —Y ₂ O ₃ system and La ₂ O ₃ —Y ₂ O ₃ system sintering aid system is remarkably improved.

[0048] Comparing the 1-4 the Si ₃ N ₄ and Si ₃ N ₄ 5-8, while the pore size is consistent with the order of 2 to 3 [mu] m, porosity of from 1 to 4 Si ₃ N ₄ is slightly higher (1.8 to 2.4%), which is characteristic.

Further, 9 to 12 have a porosity of more than 3%, and it can be seen that the flexural strength and the fracture toughness values are both lower than those of this example.

Therefore, in the case of Si ₃ N ₄ of the present embodiment, the firing temperature is lowered by 50 ° C. and the firing time is reduced by 1 hour, so that the porosity is 1 to 1, as compared with the firing conditions of the conventional densified Si ₃ N ₄ . 3%
It was found that high toughness can be achieved by

Hereinafter, the process of generating pores and the process of increasing toughness according to the present invention will be described. (i) When Si ₃ N ₄ is sintered, Si in Si ₃ N ₄ reacts with O in the sintering aid to form SiO ₂ and become a liquid phase.
The pores are discharged through the liquid phase to the outside of the system, but the pores remain if the sintering is stopped before it is completely densified. Therefore, an appropriate amount of pores can be left by controlling the sintering conditions.

In the sintered body in which such pores remain, the cracks stop by hitting the pores as shown in FIG. 5 and proceed while deflecting (pinning effect), so that the fracture toughness value can be improved.

(Ii) Table 4 shows the approximate melting points of the sintering aids used for sintering Si ₃ N ₄ .

[0054]

[Table 4]

_{Two of} Nd ₂ O ₃ and La ₂ O ₃ have considerably higher melting points than the sintering temperature of Si ₃ N ₄ of 1750 ° C. Si
₃ Sintering of N ₄ is the surface of the Si ₃ N ₄ and sintering aids must be sufficiently activated. Since the melting points of Al ₂ O ₃ and CeO ₂ are close to the sintering temperature, they are sufficiently activated and the sintering proceeds uniformly. On the other hand, since Nd ₂ O ₃ and La ₂ O ₃ have considerably high melting points, locally the part where the sintering progresses early and the part where the sintering progresses slowly appear. Since the pores are discharged through the liquid phase, they are discharged first in the part that progresses first and then in the slow part.
Therefore, the distribution of pores in the sintered body becomes non-uniform.

FIG. 6 shows Si ₃ having non-uniformly distributed pores.
₄ shows the progress of cracking of Si ₃ N ₄ uniformly dispersed with N ₄ .

As shown in FIG. 6, Si ₃ with uniformly distributed pores
In N ₄ , the crack progresses almost linearly (FIG. 6 (b)), whereas in the unevenly distributed Si ₃ N ₄ , the crack is deflected (FIG. 6 (a)). .

As shown in FIGS. 7 (a) and 7 (b), the cracks progressing in the portion (B) having many pores stop when they hit the dense portion (A) (pinning effect). It is thought that when a load is applied, it will deflect and proceed.

Therefore, by using a sintering aid having a high melting point and controlling the sintering conditions to disperse the pores non-uniformly, it is effective in improving the fracture toughness value both macroscopically and microscopically. is there.

[0060]

Example 2 Si ₃ N ₄ -Casting Molded Product As the Si ₃ N ₄ raw material, SN-ESP (center particle size 0.75 μm, α distribution rate> 95%) and SN-E10 manufactured by Ube Industries, Ltd. were used.

The sintering aids were Al ₂ O ₃ (AKP-30) and Y.
₂ O ₃ (YF) was added at 5 mol%: 3 mol%.

After predetermined amounts of the above raw materials were weighed as shown in Table 5, an organic binder (Chukyo Yushi Co., Ltd., Bind Serum) was added, and wet mixing was performed for 16 hours in water. At this time, the boulders were made of Al ₂ O ₃ and had a cylinder shape of φ12 × 13.5 l (Nippon Kagaku Sangyo), and the boulder ratio was 1.

[0063]

[Table 5]

The obtained slurry is poured into a gypsum mold (Nitto Gypsum, special grade gypsum), molded, dried and then heated at 550 ° C. for 2 hours.
Degreased for hours

The degreased compact was sintered under normal pressure at 1750 ° C. in an N ₂ atmosphere for 1.5 hours (Nos. 1 and 2).

As a comparative example, the temperature was 1750 ° C., N ₂
Conventional Si densified by pressureless sintering for 6 hours in atmosphere
₃ N ₄ was also manufactured (No. _{3, 4} ).

The evaluation method of the sintered body was the same as that of the example. Table 6 shows Si ₃ N ₄ (1 to ₃ obtained by this example.
2) and conventional Si ₃ N ₄ (3 to 4) characteristic tables are shown. still,
1 and 3 use ESP, 2 and 4 use E10.

[0068]

[Table 6]

The mechanism of increasing the toughness of the present sintered body is the same as in (i) of the example.

[0070]

Example 3 Al ₂ O ₃ Al ₂ O ₃ powder was AC160 (central particle size) manufactured by Showa Denko KK
0.41 μm) was used.

Al ₂ O ₃ powder was molded with a mold at a pressure of 200 kg / cm ^{2 so} as to have a shape of 25 × 60 × 15 mm, and further 1500 kg / cm ^{2 by} a cold isostatic press.
Was applied to form a molded body.

After degreasing the molded body at 400 ° C. for 2 hours,
Sintering was carried out under atmospheric pressure at 1650 ° C for 1 hour.

As a comparative example, 167
A conventional Al ₂ O ₃ obtained by performing normal pressure sintering at 0 ° C. for 2 hours was also manufactured.

The obtained sintered body was evaluated by using the same evaluation method as in the examples.

Table 7 shows a characteristic table of Al ₂ O ₃ (1) of this example and Al ₂ O ₃ (2) of the comparative example.

[0076]

[Table 7]

In the case of oxide ceramics such as Al ₂ O ₃ , grain growth occurs during the sintering process and the pores are discharged to the grain boundaries. The pores at the grain boundaries are easily diffused to form a mesh and are diffused out of the sintered body through the grain boundaries as passages. As a result, a sintered body having no pores is obtained.

The sintering conditions were controlled (in this example, the firing temperature was lowered by 20 ° C. and the firing time was reduced by 1 hour).
If sintering is completed while leaving an appropriate amount of pores before completely densifying, cracks are pinned by the pores and the fracture toughness value is improved by the effect of deflection.

[0079]

Example 4 3Al ₂ O ₃ .2SiO ₂ 3Al ₂ O ₃ .2SiO ₂ raw material was M manufactured by Chichibu Cement Co., Ltd.
P40 (central particle size 1.54 μm, Al ₂ O ₃ / SiO ₂ molar ratio = 1.50) was used.

25 × 60 3Al ₂ O ₃ .2SiO ₂ powder
Molded with a mold at a pressure of 200 kg / cm ^{2 so} as to have a shape of × 15 mm, and further 1500 at a cold isostatic press.
A pressure of kg / cm ² was applied to obtain a molded body.

The molded body was degreased at 400 ° C. for 2 hours, and then
Sintering was carried out under atmospheric pressure at 1650 ° C for 1 hour.

The obtained sintered body was evaluated by the same evaluation method as in the examples.

Table 8 shows 3Al ₂ O ₃ .2SiO of this example.
₂ (1) and a conventional 3A 1 ₂ O ₃ .2SiO ₂ (2) (those subjected to atmospheric pressure sintering at 1650 ° C. for 90 minutes in an air atmosphere) are shown in characteristic tables.

[0084]

[Table 8]

The mechanism for improving the fracture toughness of the present sintered body is the same as in the example.

[0086]

According to the present invention, high toughness ceramics can be obtained by forming pores to the extent that they do not affect the strength due to segregation. Since this ceramic does not impair the properties of conventional ceramics such as strength and heat resistance, it can be used for a wide variety of applications including in-vehicle engine parts.

Further, the ceramics obtained by the present invention have the following effects in addition to the improvement of K _{IC due} to its structure.

Improvement of abrasion resistance The ceramics obtained by the present invention have pores of about several μm. When such a material is used as a sliding member with a lubricant, the lubricant is stored in the pores. This lubricant is supplied from the pores in extremely small amounts during sliding of the component, and as a result, the wear resistance of the ceramic component is improved.

Improvement of thermal shock resistance The pores generated by the present invention have a shape that can most effectively disperse stress with respect to stress. Therefore, when stress due to thermal shock occurs, the pores disperse the stress,
Less likely to be absorbed and destroyed.

Taking advantage of such characteristics, starting with structural materials,
It is possible to develop applications such as cemented carbide tools for processing, sliding members, and die casting members for molten metal.

Further, since the high toughness ceramic material of the present invention can be easily obtained by controlling only the sintering conditions, the conventional sintering methods such as hot press sintering, HIP sintering and atmospheric pressure sintering can be applied. It can be easily manufactured by utilizing. Further, a molding process such as press molding or cast molding can be used as long as pores are present in the molded body.

[Brief description of drawings]

FIG. 1 is a diagram for explaining the relationship between pore shape and strength.

FIG. 2 is a diagram for explaining the relationship between pore size and strength.

FIG. 3 is a graph showing the relationship between porosity and strength.

FIG. 4 is a graph showing the relationship between porosity, strength, and fracture toughness value.

FIG. 5 is a view showing a traveling direction of a crack due to pores.

FIG. 6 is a micrograph showing the progress of cracking in Si ₃ N ₄ , where (a) is Si ₃ N ₄ with non-uniformly distributed pores,
(B) is Si ₃ N ₄ in which pores are uniformly dispersed.

FIG. 7A is a diagram showing the progress of cracks when there are a lot of pores and a dense portion, and FIG. 7B is an enlarged view of a portion C of FIG. 7A.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inoue, Seio No. 1-36 Noritake Shinmachi, Nishi-ku, Nagoya-shi, Aichi Prefecture Noritake Company Limited Limited (72) Inventor Masahiko Saito 3-chome, Noritake-shinmachi, Nishi-ku, Nagoya, Aichi Prefecture No. 1-36 Noritake Company Limited (72) Inventor Seiji Shimanoue No. 1-336 Noritake Shinmachi, Nishi-ku, Nagoya-shi Aichi Prefecture No. 1-36 Noritake Company Limited (72) Inventor Misao Iwata Nishi-ku, Nagoya, Aichi Prefecture Noritake Shinmachi 3-chome 1-36 Noritake Company Limited Limited

Claims (5)

[Claims] 1. A high toughness ceramic material, characterized in that spherical pores having a diameter of 3 μm or less are dispersed in a volume ratio of 1 to 3% with respect to the entire ceramic sintered body. 2. The high toughness ceramic material according to claim 1, wherein the pores are nonuniformly dispersed in the ceramic sintered body. 3. The high toughness ceramic material according to claim 1, wherein the ceramic sintered body is silicon nitride (Si ₃ N ₄ ). 4. The ceramic sintered body is made of alumina (Al ₂
The high toughness ceramic material according to claim 1 or 2, which is O ₃ ). 5. The ceramic sintered body is mullite (3Al
The high toughness ceramic material according to claim 1 or 2, wherein the high toughness ceramic material is ₂ O ₃ · 2SiO ₂ ).