JPH04243960A - Composite ceramics - Google Patents

Abstract

PURPOSE:To provide composite ceramics having excellent strength as well as fracture toughness and suitable as a constituent material for tools such as cutting tool, guides such as yarn guide and magnetic tape guide, sliding parts such as dies part, bearing part and pump part and medical materials such as artificial joint. CONSTITUTION:The objective composite ceramics contain at least one kind of substance selected from an oxide such as Al2O3, a nitride such as Si3N4, a carbide such as SiC and a boride such as TiB2 as main component which does not form a compound with ZrO2. It contains 10-40wt.% of ZrO2 containing >=50vol.% of a tetragonal crystal in the crystal structure. The average crystal particle diameter of the main component is 1.5-10mum and that of ZrO2 is 1.5-3mum and at least 80% of ZrO2 is present on the crystal boundary of the main component.

Description

Detailed Description of the Invention [0001] [Industrial Application Field] This invention is applicable to tools such as cutting tools, thread guides, magnetic The present invention relates to composite ceramics suitable as constituent materials for guides such as tape guides, sliding members such as die parts, bearing parts, and pump parts, and medical components such as artificial joints. [0002] There are many types and varieties of composite ceramics containing at least two types of components, but ZrO
Items that contain 2 as a component have higher strength than those that do not contain it, so they are used in cutting tools, bearing parts,
It is used as a constituent material for pump parts, etc. By the way, in the above-mentioned applications, it is naturally better to have both high strength and fracture toughness, and therefore, in the invention of JP-A-54-61215, high melting point metal oxides are used. , nitrides, carbides or borides, especially in Al2O3 with an average particle size of 0
．． It is proposed to improve the strength by dispersing relatively small ZrO2 of 1 to 1.5 μm and utilizing the stress-induced transformation of ZrO2 from tetragonal to monoclinic. This conventional composite ceramic has an average crystal grain size of 0.1 to 1.5 to stabilize the tetragonal structure of ZrO2.
Although it is limited to the range of μm, in order to do so, A
It is necessary to reduce the crystal grain size of l2O3 to suppress grain growth due to coalescence with ZrO2. however,
When the crystal grain size is made finer in this way, resistance to crack propagation becomes smaller and fracture toughness decreases. On the other hand, when trying to improve fracture toughness, it is common to use whiskers together. for example,
The invention of JP-A No. 63-45182 is based on Al2 O3 -Z
It is proposed that SiC whiskers be dispersed in rO2-based composite ceramics and that the fracture toughness can be improved by utilizing the pulling effect. However, as is well known, whiskers inhibit sinterability, so products sintered at low temperatures have many defects and have low strength. In addition, in the case of products sintered at high temperatures, the grain growth of ZrO2 during sintering is significant, and the transformation from tetragonal to monoclinic is promoted during the subsequent cooling process, resulting in an improvement in strength due to stress-induced transformation. I can't expect that. [0005] In this way, conventional composite ceramics:
There are advantages and disadvantages in terms of strength and fracture toughness, and it is difficult to say that it has both in a well-balanced manner. SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of conventional composite ceramics and to provide a composite ceramic that has excellent strength and fracture toughness. Means for Solving the Problems In order to achieve the above object, the present invention provides at least one material selected from oxides, nitrides, carbides, and borides of high-melting metals that do not form compounds with ZrO2. ZrO2, which contains ZrO2 as a main component and whose crystal structure is at least 50% by volume tetragonal
The average crystal grain size of the main component is in the range of 1.5 to 10 μm, the average crystal grain size of ZrO2 is in the range of 1.5 to 3 μm, and
To provide a composite ceramic characterized in that at least 80% of 2 is present in the grain boundaries of the main component. In other words, this invention improves fracture toughness by increasing the crystal grain size of the main component and promoting crack deflection, since the fracture of ceramics due to the occurrence of cracks progresses along the grain boundaries. It is also based on the idea of improving strength by dispersing ZrO2 at the grain boundaries of the main component. [0009] In this invention, the main component is selected from oxides, nitrides, carbides and borides. these are,
Generally, one type is selected, but it is also possible to select two or more types. Thus, the main component does not form a compound with ZrO2. If the main component and ZrO2 form a compound, the bonding strength at the interface between the main component and ZrO2 will drop significantly, or the compound phase will grow abnormally during sintering, making it impossible to obtain a high-strength composite ceramic. . [0010] Specific examples of main components include Al2 O3, Fe3 O4, and Cr2 O3 as oxides. In addition, as nitrides, Si3 N4 and TiN
, AlN. Furthermore, carbides such as SiC and T
There are iC and ZrC. Furthermore, as borides,
There are TiB2 and ZrB2. Among them, Al2O
3, Si3 N4, SiC, TiC, and TiB2 are preferred. Particularly preferred is Al2O3. The average crystal grain size of the main component mentioned above is 1.5
~10 μm. If the average grain size is less than 1.5 μm, crack deflection cannot be expected and fracture toughness will not improve. Moreover, when it exceeds 10 μm, the strength decreases significantly. A more preferable range of average grain size is 2 to 2.
It is 5 μm. On the other hand, ZrO2 is contained in a range of 10 to 40% by weight. In addition, ZrO2 has a crystal structure in which at least 50% by volume is tetragonal and the remainder cubic and/or monoclinic. If ZrO2 is less than 10% by weight and ZrO2 having a tetragonal crystal structure is less than 50% by volume, no effect of improving strength due to stress-induced transformation from tetragonal to monoclinic can be expected. Moreover, when ZrO2 exceeds 40% by weight, ZrO2
The strength decreases due to aggregation of crystal grains. [0013] The average crystal grain size of ZrO2 is 1.5 to 3
It is in the μm range. If the thickness is less than 1.5 μm, no crack deflection action can be expected and the fracture toughness will not improve. Also, 3 μm
If it exceeds this, ZrO2 having a monoclinic crystal structure increases, many microcracks are formed at the grain boundaries of ZrO2, and the strength decreases. [0014] The above-mentioned ZrO2 has at least 8
0% is distributed and present at the grain boundaries of the main component. Even if it exists within the crystal grains of the main component, it is only in small quantities. As a result, Z
rO2 effectively undergoes stress-induced transformation, which relieves stress at the crack tip and improves strength and fracture toughness. The composite ceramic of the present invention can be produced, for example, as follows. That is, first, a predetermined amount of ZrO2 powder is added to the main component powder and mixed thoroughly to obtain a mixed powder. The mixing operation may be wet or dry. After drying the mixed powder, if necessary, it is coarsely ground, sieved, or granulated. Note that the main component powder preferably has an average particle size in the range of 1 to 2 μm because dense sintering can be performed. In addition, the ZrO2 powder contains about 1.5 to 5 mol% of Y2O3 and C in order to obtain at least 50% by volume of tetragonal crystals in the composite ceramic.
A material containing a stabilizer such as eO2 and whose tetragonal crystal is in a metastable state at room temperature is used. The average particle size is preferably 1 μm or less in view of uniform dispersion in the main component. Next, the mixed powder is molded into a desired shape using a well-known molding method, such as a mold molding method or a rubber press molding method, and is sintered. For sintering, a pressure sintering method or a hot press method can be used, and there are cases where molding in advance is not required. The atmosphere during sintering is a non-oxidizing atmosphere when the main component is a carbide, nitride or boride. In the case of an oxide, an oxidizing atmosphere or a non-oxidizing atmosphere may be used. The sintering temperature and time are such that the average crystal grain size of the main component is in the range of 1.5 to 10 μm, and Z
The average grain size of rO2 is carefully controlled to be in the range of 1.5 to 3 μm. In addition, in order to have at least 80% of ZrO2 present in the grain boundaries of the main component, a temperature of 0.5°C near the sintering temperature is required to prevent the main component from rapidly growing grains and incorporating ZrO2 into the grains. Raise the temperature at a slow rate of less than /min. On the other hand, after sintering, if the cooling rate is too slow, a large amount of monoclinic ZrO2 will precipitate, making it impossible to achieve at least 50% by volume of tetragonal crystals, so cooling is performed at a rate of 5° C./min or more. [Examples and Comparative Examples] Example 1: ZrO2 powder with an average particle size of 1 μm and containing 2.5 mol% Y2 O3 as a stabilizer was added to Al2 O3 powder with an average particle size of 2 μm. 10% by weight was added, wet-mixed in ethanol for 24 hours using a ball mill, and then sprayed, granulated and dried to obtain a mixed powder. Next, this mixed powder was filled into a graphite mold and heated at 300 kgf/cm2 in an argon atmosphere.
The composite ceramics were sintered at 1700° C. for 1 hour under a pressure of The temperature increase rate is 5℃ up to 1200℃.
/min, above that 0.5℃/min, cooling rate is 7℃
/ minute. Regarding the composite ceramic thus obtained, the average crystal grain size of Al2O3 and ZrO2, the proportion of tetragonal ZrO2, the proportion of ZrO2 present in the grain boundaries of Al2O3, the bending strength, and the fracture toughness were determined. I asked for. The average crystal grain size was determined by polishing and etching the surface of the composite ceramic, measuring the maximum length of the crystal grains in several directions on a micrograph of the etched surface, and simply averaging them. Furthermore, when the surface of the composite ceramic was carefully mirror-polished and analyzed by X-ray diffraction, the proportion of tetragonal ZrO2 was found to be 2θ=30.2°.
The integrated intensity T(111) of the diffraction peak of the tetragonal (111) plane appearing nearby and the integrated intensity M(1) of the diffraction peak of the monoclinic (111) plane appearing around 2θ=28.2
11) and the monoclinic (
111- ) plane diffraction peak integrated intensity M(111-
), from the formula, {T(111)/[T(111)+M(111)+M(
111-)]×100. Note that 1- represents -1. Furthermore, the proportion of ZrO2 present at the grain boundaries of Al2O3 can be determined by reading the number Zb of ZrO2 present at the grain boundaries of Al2O3 and the number Zi of ZrO2 present within the grains from the above-mentioned micrograph. It was determined by the formula: [Zb / (Zb + Zi)] x 100. Furthermore, the bending strength of 10 pieces obtained by processing composite ceramics, length 36 mm, width 4 mm, thickness 3
A three-point bending test was performed on a test piece of mm in accordance with JIS R1601, and the value was calculated as a simple average value. Span length is 30mm, crosshead speed is 0.5m
m/min. In addition, the fracture toughness is JIS R160
7, a load of 10 was applied using a Vickers hardness tester to the longitudinal center of five test pieces similar to those used in the bending test.
kgf was made, and then a bending test was conducted in the same manner as above, and the fracture toughness was determined by measuring the fracture load, which was calculated as a simple average value. The test results are shown below. [0022] Average grain size of Al2O3
:6.2μm Average crystal grain size of ZrO2
:1.6μm Tetragonal ZrO2 ratio
:85% by volume ZrO2 present at grain boundaries of Al2O3
Ratio: 82% Bending strength
:
62.1kgf/mm2 Fracture toughness

:5.2MPa ・m1/2 Example 2: Z
A composite ceramic was prepared and tested in the same manner as in Example 1, except that the amount of rO2 powder added was changed to 20% by weight. The test results are shown below. [0023] Average grain size of Al2O3
:5.1μm Average grain size of ZrO2
:1.8μm Tetragonal ZrO2 ratio
:79% by volume ZrO2 present at grain boundaries of Al2O3
Ratio: 85% Bending strength
:
65.3kgf/mm2 Fracture toughness

:5.3MPa ・m1/2 Example 3: Z
A composite ceramic was prepared and tested in the same manner as in Example 1, except that the amount of rO2 powder added was changed to 30% by weight. The test results are shown below. [0024] Average grain size of Al2O3
:3.6μm Average grain size of ZrO2
:2.1μm Tetragonal ZrO2 ratio
:75% by volume ZrO2 present at grain boundaries of Al2O3
Ratio: 93% Bending strength
:
70.2kgf/mm2 Fracture toughness

:5.8MPa ・m1/2 Example 4: Z
A composite ceramic was prepared and tested in the same manner as in Example 1, except that the amount of rO2 powder added was changed to 40% by weight. The test results are shown below. [0025] Average grain size of Al2O3
:3.0μm Average grain size of ZrO2
:2.5μm Tetragonal ZrO2 ratio
:68% by volume ZrO2 present at grain boundaries of Al2O3
Ratio: 95% Bending strength
:
68.7kgf/mm2 Fracture toughness

: 6.3 MPa ・m1/2 Comparative Example 1: Al2 O3 powder with an average particle size of 0.5 μm and 2.5 mol% Y2 O3 as a stabilizer with an average particle size of 1 μm.
A mixed powder was obtained in the same manner as in Example 1 by adding 5% by weight of ZrO2 powder containing ZrO2. Next, this mixed powder was filled into a graphite mold and heated at 300 kgf/cm2 in an argon atmosphere.
Composite ceramics were produced by sintering at 1700° C. for 1 hour under a pressure of The test results are shown below. The temperature increase rate during sintering was 1200
The cooling rate was 5°C/min up to 5°C and 2°C/min above that, while the cooling rate was 3.5°C/min. [0027] Average grain size of Al2O3
:7.1μm Average grain size of ZrO2
:1.2μm Tetragonal ZrO2 ratio
:88% by volume ZrO2 present at grain boundaries of Al2O3
Ratio: 72% Bending strength
:
42.8kgf/mm2 Fracture toughness

:4.8MPa ・m1/2 Comparative example 2: Z
The amount of rO2 powder added was changed to 20% by weight, and
A composite ceramic was produced and tested in the same manner as in Comparative Example 1, except that the sintering temperature was changed to 1450°C. The test results are shown below. [0028] Average grain size of Al2O3
:1.2μm Average crystal grain size of ZrO2
:0.3μm Tetragonal ZrO2 ratio
:99% by volume ZrO2 present at grain boundaries of Al2O3
Ratio: 81% Bending strength
:
60.1kgf/mm2 Fracture toughness

:4.1MPa ・m1/2 Comparative example 3: Z
The amount of rO2 powder added was changed to 30% by weight, and
A composite ceramic was produced and tested in the same manner as in Comparative Example 1, except that the sintering temperature was changed to 1450°C. The test results are shown below. Average grain size of Al2O3
:1.2μm Average crystal grain size of ZrO2
:0.4μm Tetragonal ZrO2 ratio
:99% by volume ZrO2 present at grain boundaries of Al2O3
Ratio: 79% Bending strength
:
64.6kgf/mm2 Fracture toughness

:4.2MPa・m1/2 Comparative example 4:Z
A composite ceramic was prepared and tested in the same manner as in Comparative Example 1, except that the amount of rO2 powder added was changed to 40% by weight. The test results are shown below. [0030] Average grain size of Al2O3
:6.4μm Average grain size of ZrO2
:3.1μm Tetragonal ZrO2 ratio
:43% by volume ZrO2 present at grain boundaries of Al2O3
Ratio: 69% Bending strength
:
45.0kgf/mm2 Fracture toughness

: 4.6 MPa ・m1/2 Example 5: Si3 N4 powder with an average particle size of 1.5 μm and 2.5 mol% Y2 O3 as a stabilizer with an average particle size of 1 μm
15% by weight of ZrO2 powder was added thereto, wet mixed in a ball mill for 24 hours, dried in a rotary evaporator, coarsely ground, and sieved through a 50 μm mesh to obtain a mixed powder. Next, this mixed powder was filled into a graphite mold and heated to 1×10 −5 torr. 300 during the decompression of
A composite ceramic was produced by sintering at 1600° C. for 1 hour under a pressure of kgf/cm 2 and tested in the same manner as in Example 1. The test results are shown below. The temperature increase rate during sintering was 5°C/min up to 1200°C and 0.5°C/min above that, and the cooling rate was 7°C/min. [0032] Average grain size of Al2O3
:6.5μm Average crystal grain size of ZrO2
:1.8μm Tetragonal ZrO2 ratio
:83% by volume ZrO2 present at grain boundaries of Al2O3
Ratio: 86% Bending strength
:
67.2kgf/mm2 Fracture toughness

:5.8MPa ・m1/2 Example 6: Z
A composite ceramic was prepared and tested in the same manner as in Example 5, except that the amount of rO2 powder added was changed to 20% by weight. The test results are shown below. [0033] Average grain size of Al2O3
:6.1μm Average grain size of ZrO2
:1.9μm Tetragonal ZrO2 ratio
:83% by volume ZrO2 present at grain boundaries of Al2O3
Ratio: 85% Bending strength
:
68.5kgf/mm2 Fracture toughness

:6.0MPa ・m1/2 Example 7: Z
A composite ceramic was prepared and tested in the same manner as in Example 5, except that the amount of rO2 powder added was changed to 35% by weight. The test results are shown below. [0034] Average grain size of Al2O3
:5.3μm Average grain size of ZrO2
:2.2μm Tetragonal ZrO2 ratio
:75% by volume ZrO2 present at grain boundaries of Al2O3
Ratio: 85% Bending strength
:
73.3kgf/mm2 Fracture toughness

:6.3MPa・m1/2 Comparative example 5:Z
The amount of rO2 powder added was changed to 20% by weight, and
A composite ceramic was produced and tested in the same manner as in Example 5, except that the sintering temperature was changed to 1500°C. The test results are shown below. [0035] Average grain size of Al2O3
:2.8μm Average grain size of ZrO2
:0.5μm Tetragonal ZrO2 ratio
:95% by volume ZrO2 present at grain boundaries of Al2O3
Ratio: 90% Bending strength
:
78.9kgf/mm2 Fracture toughness

:4.3MPa ・m1/2 Comparative example 6: Z
The amount of rO2 powder added was changed to 20% by weight, and
A composite ceramic was produced and tested in the same manner as in Example 5, except that the sintering temperature was changed to 1700°C. The test results are shown below. Average grain size of Al2O3
:10.5μm ZrO2
average grain size of
:3.7μm Tetragonal ZrO2 ratio
:41% by volume ZrO2 present at grain boundaries of Al2O3
Ratio: 73% Bending strength

:38.2kgf/mm2 Fracture toughness

:3.8MPa・m1/2 Example 8:
Z containing 2.5 mol% Y2O3 as a stabilizer with an average particle size of 1 μm in SiC powder with an average particle size of 1 μm.
Add 15% by weight of rO2 powder and mill with a ball mill for 24 hours.
After wet mixing for a period of time, the mixture was dried using a rotary evaporator, coarsely pulverized, and sieved through a 50 μm mesh to obtain a mixed powder. Next, this mixed powder was filled into a graphite mold and heated to 1×10 −5 torr. 300 during the decompression of
A composite ceramic was prepared by sintering at 1750° C. for 1 hour under a pressure of kgf/cm 2 and tested in the same manner as in Example 1. The test results are shown below. The temperature increase rate during sintering was 5°C/min up to 1200°C and 0.5°C/min above that, and the cooling rate was 7°C/min. Average grain size of Al2O3
:3.8μm Average grain size of ZrO2
:1.5μm Tetragonal ZrO2 ratio
:92% by volume ZrO2 present at grain boundaries of Al2O3
Ratio: 95% Bending strength
:
53.7kgf/mm2 Fracture toughness

:5.3MPa・m1/2 Example 9:Z
A composite ceramic was prepared and tested in the same manner as in Example 8, except that the amount of rO2 powder added was changed to 20% by weight. The test results are shown below. [0039] Average grain size of Al2O3
:3.3μm Average grain size of ZrO2
:1.5μm Tetragonal ZrO2 ratio
:93% by volume ZrO2 present at grain boundaries of Al2O3
Ratio: 93% Bending strength
:
56.5kgf/mm2 Fracture toughness

:5.3MPa・m1/2 Example 10:
A composite ceramic was prepared and tested in the same manner as in Example 8, except that the amount of ZrO2 powder added was changed to 35% by weight. The test results are shown below. [0040] Average grain size of Al2O3
:2.8μm Average grain size of ZrO2
:1.7μm Tetragonal ZrO2 ratio
:85% by volume ZrO2 present at grain boundaries of Al2O3
Ratio: 95% Bending strength
:
60.0kgf/mm2 Fracture toughness

:5.7MPa・m1/2 Comparative example 7:Z
The amount of rO2 powder added was changed to 20% by weight, and
A composite ceramic was produced and tested in the same manner as in Example 8, except that the sintering temperature was changed to 1500°C. The test results are shown below. [0041] Average grain size of Al2O3
:1.3μm Average grain size of ZrO2
:0.3μm Tetragonal ZrO2 ratio
:96% by volume ZrO2 present at grain boundaries of Al2O3
Ratio: 96% Bending strength
:
58.6kgf/mm2 Fracture toughness

:4.1MPa・m1/2 Comparative example 8:Z
The amount of rO2 powder added was changed to 20% by weight, and
A composite ceramic was produced and tested in the same manner as in Example 8, except that the sintering temperature was changed to 1700°C. The test results are shown below. [0042] Average grain size of Al2O3
:3.7μm Average grain size of ZrO2
:1.3μm Tetragonal ZrO2 ratio
:85% by volume ZrO2 present at grain boundaries of Al2O3
Ratio: 70% Bending strength
:
51.0kgf/mm2 Fracture toughness

:4.0MPa・m1/2 Example 11:
TiB2 powder with an average particle size of 2 μm and an average particle size of 1 μm
15% by weight of ZrO2 powder containing 2.5 mol% Y2O3 as a stabilizer was added, wet-mixed in a ball mill for 24 hours, dried in a rotary evaporator, coarsely ground, and milled with a 50 μm mesh. A mixed powder was obtained by sieving. Next, this mixed powder was filled into a graphite mold and heated to 1×10 −5 torr. 300 during the decompression of
A composite ceramic was produced by sintering at 1800° C. for 1 hour under a pressure of kgf/cm 2 and tested in the same manner as in Example 1. The test results are shown below. The temperature increase rate during sintering was 5°C/min up to 1200°C and 0.5°C/min above that, and the cooling rate was 7°C/min. [0044] Average grain size of Al2O3
:8.5μm Average grain size of ZrO2
:2.1μm Tetragonal ZrO2 ratio
:78% by volume ZrO2 present at grain boundaries of Al2O3
Ratio: 83% Bending strength
:
51.4kgf/mm2 Fracture toughness

:5.6MPa・m1/2 Example 12:
A composite ceramic was prepared and tested in the same manner as in Example 11, except that the amount of ZrO2 powder added was changed to 20% by weight. The test results are shown below. [0045] Average grain size of Al2O3
:7.7μm Average grain size of ZrO2
:2.3μm Tetragonal ZrO2 ratio
:75% by volume ZrO2 present at grain boundaries of Al2O3
Ratio: 81% Bending strength
:
58.0kgf/mm2 Fracture toughness

:6.0MPa・m1/2 Example 13:
A composite ceramic was prepared and tested in the same manner as in Example 11, except that the amount of ZrO2 added was changed to 35% by weight. The test results are shown below. [0046] Average grain size of Al2O3
:7.0μm Average grain size of ZrO2
:2.5μm Tetragonal ZrO2 ratio
:70% by volume ZrO2 present at grain boundaries of Al2O3
Ratio: 81% Bending strength
:
62.2kgf/mm2 Fracture toughness

:6.1MPa・m1/2 Comparative example 9:Z
A composite ceramic was produced and tested in the same manner as in Example 11, except that the amount of rO2 added was changed to 20% by weight and the sintering temperature was changed to 1500°C. The test results are shown below. [0047] Average grain size of Al2O3
:3.2μm Average grain size of ZrO2
:1.3μm Tetragonal ZrO2 ratio
:88% by volume ZrO2 present at grain boundaries of Al2O3
Ratio: 80% Bending strength
:
61.3kgf/mm2 Fracture toughness

:4.3MPa・m1/2 Comparative example 10:
A composite ceramic was produced and tested in the same manner as in Example 11, except that the amount of ZrO2 added was changed to 20% by weight and the sintering temperature was changed to 1700°C. The test results are shown below. [0048] Average grain size of Al2O3
:5.8μm Average grain size of ZrO2
:1.8μm Tetragonal ZrO2 ratio
:78% by volume ZrO2 present at grain boundaries of Al2O3
Ratio: 71% Bending strength
:
52.5kgf/mm2 Fracture toughness

:4.0MPa・m1/2 Comparative example 11:
Al2O3 powder with an average particle size of 1 μm, 10% by weight of TiO2 powder with an average particle size of 0.7 μm, and 2.5 mol% Y2O3 with an average particle size of 1 μm as a stabilizer.
20% by weight of ZrO2 powder was added thereto, wet-mixed in ethanol for 24 hours using a ball mill, and then sprayed, granulated and dried to obtain a mixed powder. Next, this mixed powder was filled into a graphite mold and heated at 300 kgf/cm2 in an argon atmosphere.
The composite ceramics were sintered at 1700° C. for 1 hour under a pressure of The temperature increase rate is 5℃ up to 1200℃.
/min, higher than that was 0.5°C/min, while the cooling rate was 5°C/min. [0050] The composite ceramic thus obtained has the following properties:
As a result of microstructural observation, ZrO2 and TiO2
There are needle-shaped crystals of ZrTiO4, which is a compound with
It was confirmed that cracks were selectively propagating along the grain boundaries of ZrTiO4. In addition, the results of testing in the same manner as in Example 1 were as follows, and both the bending strength and fracture toughness were extremely low. Bending strength: 23.3 kgf/mm2 Fracture toughness: 3.
8MPa・m1/2 [Effect of the invention] The composite ceramics of the present invention has ZrO
ZrO2 containing as a main component at least one selected from oxides, nitrides, carbides, and borides of high melting point metals that do not form compounds with ZrO2 and whose crystal structure is at least 50% by volume tetragonal. The average crystal grain size of the main component is in the range of 1.5 to 10 μm, and the average crystal grain size of ZrO2 is in the range of 1.5 to 3 μm.
m and at least 80% of ZrO2
% is present in the grain boundaries of the main components,
As is clear from the comparison between Examples and Comparative Examples, both strength and toughness are excellent.

Claims (2)

[Claims] Claim 1: Contains as a main component at least one selected from oxides, nitrides, carbides, and borides of high-melting metals that do not form compounds with ZrO2, and has a crystal structure in which at least 50% by volume is tetragonal. A certain ZrO2 is 1
The average crystal grain size of the main component is in the range of 1.5 to 10 μm, the average crystal grain size of ZrO2 is in the range of 1.5 to 3 μm, and
1. A composite ceramic characterized in that at least 80% of the ceramic is present in the grain boundaries of the main component. Claim 2: The main components are Al2 O3, Si3 N4
2. The composite ceramic according to claim 1, wherein the composite ceramic is at least one selected from , SiC, TiC, and TiB2.