JPS6212662A - High toughness zirconia base sintered body - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention relates to a high-toughness zirconia sintered body, and more specifically, the present invention relates to a high-toughness zirconia sintered body, and more specifically, one or more selected from Y20ztceo □tMiro*CaO is used as a stabilizer. Zirconia and 3A120, 2Si, which are mainly composed of square parts, including
Oz (mullite) or A1□O5 and 3A! 20,・2
The present invention relates to a high toughness zirconia sintered body containing SiO2 (mullite).

[Conventional technology]

Zirconia has a high melting point (and is chemically stable, making it an excellent heat-resistant material. However, zirconia undergoes a phase change from a cubic crystal in the high-temperature region to a tetragonal crystal to a monoclinic crystal). The transition is accompanied by a volume change, especially the volume change during the phase transition from tetragonal to monoclinic, so if zirconia is used alone as a sintered body, it will break due to this volume change when the temperature is raised or lowered. There is a big fish that will do that.

In order to remove this deficiency, α, CaO, Mg
By dissolving divalent or trivalent metal oxides such as o+Y2O5 to prevent phase transition, stabilized zirconia consisting of cubic crystals or partially stabilized zirconia consisting of cubic crystals and monoclinic crystals can be produced even at room temperature. Many have been published. In addition, it has been announced that partially stabilized zirconia, in which a metastable tetragonal phase exists alone in a sintered body, exhibits high strength. It is thought that this is because the destruction effect caused by external stress is alleviated by transforming into a monoclinic crystal phase, which is a stable phase.

As described above, as a stabilizer for obtaining a sintered body mainly consisting of tetragonal or cubic crystals at room temperature, Y2O, which is mainly used as a stabilizer, has been used to exhibit high toughness and strength. However, this partially stabilized norphea, which is mainly composed of tetragonal items, is a metastable phase resulting from bringing a high temperature phase to a low temperature range, so its structure and properties change over time.
In particular, heating at a relatively low temperature of 200°C to 400°C causes a phase transition to monoclinic crystal, resulting in extremely large deterioration of strength over time.

Since the aging of such partially stabilized zirconia sintered bodies depends on the composition of the stabilizer, the structure of the sintered body, and the crystal grain size, the amount of Y2O3 as a stabilizer was specified, and It has been reported that a sintered body with high strength and high toughness with less deterioration over time in a specific temperature range can be obtained by obtaining a sintered body of During firing, thermal history is added by controlling the rate of temperature rise and cooling, and zirconia, which has a mainly cubic structure, has a temperature of 0.5 to 4.5
It has been reported that a zirconia sintered body that has strong thermal shock strength and does not break even after long-term use can be obtained by containing zirconia with a monoclinic structure in the amount of % by weight (Japanese Unexamined Patent Application Publication No. 1983-1991). -41873).

On the other hand, in order to obtain a sintered body containing tetragonal products that are metastable at room temperature, the sintered body must be mv and the sintered body particle size must be small. Two properties are required: solidity and fine powder. Various methods have been studied to obtain fine powders that are easily sinterable. Among them, ZrO2 fine powders are made by co-precipitating a mixture of Zr0c12 and YCl3, calcining the powder, and stabilizing it with Y2O. Ceramic Bulletin 1 published in the United States states that a high-strength ZrO2 sintered body can be obtained by sintering ZrO2.
Published in 1976, volume 55, page 77.

Mullite (3A1□0.2SiO2) is an excellent ceramic because it is heat resistant, has excellent thermal shock resistance, has good creep properties at high temperatures, and does not lose strength even at high temperatures.

However, since mullite is difficult to sinter densely, the strength of the sintered body is extremely low.Mullite, which is a ceramic that cannot be sintered densely, has high fracture resistance and good heat resistance fluctuation. For the purpose of obtaining a ceramic molded body, a powder mixture consisting of a ceramic matrix material such as mullite and a ZrO2-containing compound is once sintered, and then heat treated at a temperature higher than the sintering temperature. There is (Japanese Unexamined Patent Publication No. 158173)
.

Furthermore, in order to improve the performance of these ceramic molded bodies, we have developed a compact, micro-crack-free A1□01
, mullite, spinel, etc., monoclinic or tetragonal ZrO2 particles that are not stabilized with the base matrix material, or ZrO2 particles that are stabilized with Y2O and are mainly tetragonal. It has been proposed to embed a compressed portion made of a mixture of

[Good luck that invention attempts to solve, α]

However, the zirconia sintered body mainly composed of square pieces that specifies Y2O as a stabilizer is also Zr02-Y2
Zirconia of O, ZrO2CaO, and Zr02-MgO systems, mainly having a cubic crystal structure and having a crystalline structure of 0.5 to 4
．． Although the zirconia sintered body containing 5% by weight of monoclinic crystals has been improved in terms of not deteriorating over time in a specific temperature range or in terms of thermal shock resistance, it still deteriorates in hot water, and It is also insufficient in strength.

Furthermore, zirconia sintered bodies using raw material powder obtained by coprecipitating a mixture of ZrO2 and YCl3 are not necessarily perfect in terms of similar characteristics. Moreover, the metastable tetragonal crystal stabilized by Y2O3 is
It has been observed that aging at 400°C causes a transformation from a tetragonal product to a monoclinic crystal, resulting in a decrease in material strength and toughness, and especially in the presence of water vapor and in a high-pressure hot aqueous solution, the stability of a tetragonal product is significantly reduced. However, there is a serious defect that causes grain boundary fracture,
There is a solution.

Additionally, partially stabilized zirconia has a coefficient of thermal expansion of approximately 11X.
IO-' level and other structural ceramics are 3-4
This is a large value compared to X 10 to 6, but this is both an advantage and a disadvantage, and it also has a high temperature ( For example, its use as a structural material is limited due to the severe decrease in strength.

On the other hand, in any of the proposals for ceramic sintered bodies containing zirconia in mullite, the amount of zirconia contained in the sintered bodies is small, the proportion of tetragonal items in zirconia is low, and there is a considerable amount of monoclinic crystals. include. Therefore, the amount of square zirconia contained in the sintered body as a whole is considerably small, and the effect of mitigating destruction caused by external stress is also small, resulting in a low strength of the sintered body. Furthermore, in mullite ceramics containing zirconia that does not contain a stabilizer, the metastable tetragonal shape easily undergoes a transition to monoclinic crystal under heat and hydrothermal conditions, reducing the strength of the sintered body. Due to the risk of corrosion, its use as a structural material is limited.

The present invention was made to solve the above-mentioned drawbacks of conventional partially stabilized zirconia sintered bodies and mullite ceramics, and has high strength, excellent thermal stability and hydrothermal stability, and is suitable for mechanical processing at high temperatures. The purpose of this invention is to provide a high-toughness zirconia sintered body having improved physical properties and a desired coefficient of thermal expansion, and to greatly expand the range of use of the zirconia sintered body.

[Means for solving the problems] The high-toughness zirconia sintered body of the present invention contains Y2O1, Ce
(3A+20.2SiO2) partially stabilized zirconia mainly consisting of square pieces containing one or more selected from O2, MgO, and CaO as a stabilizer in a range of 0.5 to 60% by internal weight Or mullite and AI
The gist is that the average crystal grain size is 3 μl or less in a sintered body containing .20.

The high-toughness zirconia sintered body of the present invention is obtained by uniformly mixing partially stabilized zirconia with a ZrO2 sol and/or a water-soluble salt together with a water-soluble salt as a stabilizer in a solution state. , raw materials obtained by separation in the form of precipitates can be used.

Ill N 1shi-7, r
(''), l2t・[1-yamaff1slIlo1%, Y20J:1-6u+o1%, CeO2 near-1
511o1%, MBO: 3. O-10too1%, C
aO: in the range of 2-8 mol%, 2! In the case of mixed addition of f1 or more, the respective mixing ratios are within the above fi range.

Further, part or all of 2r02 in the high toughness zirconia sintered body of the present invention can be replaced with HfO2.

In the present invention, as a stabilizer Y2O,, CeO2, M
The reason why one or more selected from gO and CaO is added to Zirphere is to dissolve these divalent or trivalent metal oxides in ZrO2, thereby creating a partially stable structure mainly composed of tetragonal crystals at room temperature. This is to obtain oxidized zirconia.

In the present invention, the amount of Y2O added is as follows:
1.0 to 6.0 of%, more preferably 1.5
~5.0 mol%. The amount of CeO2 added is zirconia (17.0 to 15.0++o1%, more preferably 8.0 to 14.0+ao1%.Mg
The amount of O added is 3.0 to 10. , Omo
1%, more preferably 4.0 to 9.1%. (lno1%
It is. Furthermore, the amount of CaO added is 2.
0 to 8,0 LIlo1%, more preferably 2.5
~6.0 mol%. When using a mixture of two or more of these, the mixing ratio of each should be within the above content range. For example, when using equal amounts of Y2O3 and CeO2, the amount of Y2O3 used is (1,0 ~6.0
) Xi/2 =0.5~3. Omol%, CeO2 usage amount is (7,0~15,0)XI/2=3.5~7.5m
It may be within the range of ol%.

In the present invention, the reason for limiting the amount of stabilizer added is as follows. This is because if the amount added is less than the lower limit, a tetragonal crystal phase cannot be obtained.

Furthermore, if the amount added exceeds the upper limit, there is a marked tendency for mechanical properties such as bending strength to deteriorate.

In addition, some or all of Y2O, may be replaced with La20. , Er
A similar effect can be obtained by replacing with rare earth M oxides such as 20=, Nd2O, yb, o, etc.

Furthermore, when selecting Y2O as a stabilizer, if it is necessary to further improve thermal stability and hydrothermal stability, it is preferable to coexist CeO2 as a stabilizer.

Since it is a partially stabilized zirconia made of square pieces,
Shows high strength and toughness. Originally, the tetragonal product is in a metastable phase, so when the sample surface is ground, a portion of the sample undergoes a transition to monoclinic crystal, and the residual compressive stress in the surface layer contributes to the strengthening of the sintered body. The degree of this strengthening depends on the surface roughness caused by grinding and the grain size of the sintered body. Therefore, the partially stabilized zirconia mainly consisting of tetragonal elements according to the present invention refers to zirconia that is in a mirror state and contains at least 20% or more of tetragonal elements when the crystal phase is measured by Xi diffraction. 2 square items
If it is less than 0%, the toughness will be low, so it is necessary that the tetragonal system be present in the proportion of 20% or more.

The high toughness zirconia sintered body of the present invention is a conventional partially stabilized zirconia sintered body of 3AI20.・By finely dispersing the acicular crystals that are the 2SiO2 (mullite) component and controlling the microstructure of the sintered body, it has excellent strength at room temperature and is resistant to deterioration due to the transition from tetragonal to monoclinic. It is extremely stable thermally, and exhibits high stability even in high-pressure hot aqueous solutions in the presence of water vapor, which causes more severe deterioration than in the past. Furthermore, it also improves the mechanical properties such as strength and creep of the partially stabilized zirconia sintered body at high temperatures.

In addition, for the high-toughness zirconia sintered body containing A1□03, Temo, 3 Al2O3.
) The above effect can be obtained by dispersing needle-like crystals. Furthermore, 3AI20.・2Si
By adjusting the amount of n, (mullite), it becomes possible to lower the thermal expansion coefficient of partially stabilized zirconia and control it to a desired value.

Here, 3AI□O0・2S102 (mullite) or A I20, Oyo (/ 3 A I20 s ・2
The reason for controlling the amount of S io 2 (A phyto) added is as follows. If the amount added is less than 0.5% by internal weight,
This is because the effect of addition is poor, and if the content exceeds 60% by internal weight, the content of ZrO2, which has toughness, is lowered and mechanical properties such as strength and toughness are sharply reduced. In order to make the present invention more effective, 3AI□O5・2SiOz(
Murai L) Tree Xbtl+A l-n-1rr') A
I/”1-Q C: Addition amount of ^2 (mullite) to 3
It is preferable to select the content within the range of 50 to 50% by internal weight.

In order to obtain excellent hot water stability in the sintered body of the present invention, a theoretical density of 97.5% or more is desirable, and a theoretical density of 99% or more is more preferable. For this reason, 3A1. used in the present invention. O,・2SiO2 (mullite) is
It is desirable that the particles be fine and easily sinterable. A fine and easily sinterable raw material powder for darning can be obtained, for example, by mixing solutions each containing an aluminum compound and a silicate compound in a liquid phase, drying the mixture, calcining it at 1100 to 1500°C, and pulverizing it. can get. In addition, 3Δ12o referred to in the present invention
, ・2SiO2 (mullite) is A I20 , /
It refers to a composition in which the S io m ratio is within the range of 65/35 to 75/25.

It is desirable that the sintered body of the present invention has an average crystal grain size of 3 μIII or less. When the average crystal grain size is 3 μω, the tetragonal product changes to a monoclinic system and the toughness decreases. Further, the average crystal grain size of the tetragonal Zylphere in the sintered body is preferably 0.5 μm or less in order to obtain excellent heat resistance and hot water stability.

The partially stabilized zirconia of the present invention is a raw material obtained by uniformly mixing a ZrO2 sol and/or a water-soluble salt together with a water-soluble salt as a stabilizer in a solution state, and then separating it in the form of a precipitate. Since the stabilizer is uniformly dispersed in ZrO2, an easily sinterable powder consisting of extremely fine particles can be used as a raw material.

As a result, a sintered body having fine grains, a uniform composition, and almost no micropores is obtained, and desired values for strength and VL properties are obtained.

Furthermore, even if part or all of ZrO2 in the high-toughness norconic sintered body of the present invention is replaced with 11fO2, it exhibits exactly the same characteristics.

〔Example〕

EXAMPLES Hereinafter, the present invention will be explained in detail with reference to Examples, and the effects of the present invention will be clarified.

(Example 1) Aluminum nitrate and ethyl silicate were mixed with water and ethanol to give a mullite composition, and the mixed solution was spray-dried at 600°C. 100% of the obtained synthetic powder
By calcining at 0~1300''C and pulverizing, specific surface Jfi50~10m27g, AI203
/5iOz ratio 7! l'71.8/28.2 (7) 3
A +202 .2 S io 2 (mullite) was prepared. Note that this synthetic mullite exhibited a density of 3.17 when sintered at 1600°C.

Next, as a stabilizer, Y2O1,
f) 3 A I203 ・2 S io 2 (mullite) and A with an average particle size of 0.3μ and a theoretical purity of 99.9%.
I20 was added in the proportions shown in Tables 1 and 2, and the powder was wet-mixed and dried, then isotropically molded at a pressure of 1.5 Lon/c+++2, and heated in the air at a temperature of 1400 to 1650°C for 2 hours. Fired. The average delivered particle size of the obtained sintered bodies was all 3 μm or less.

The obtained sintered body was cut and polished to a size of 3 x 4 x 40a++n, and its density, crystal phase, bending strength, and fracture toughness were measured and the results were reported! It is shown in Table 51 and Table tjS2.

The bending strength is 3 x 4 x 40mm according to JIS regulations.
Using sample pieces, the average value of 10 specimens subjected to 3-point bending with a span of 30u+- and a speed of 0.5+nm/vain was shown.

Fracture toughness was measured by micro-indentation by making an indentation under a load of 50 kg, and the KIC value was determined using the formula of Shinryo et al.

Quantitative measurement of the crystalline phase was performed by X-ray diffraction method. That is, the integrated intensity IM of the (1ii) plane and (111) plane of the monoclinic crystal of a sample piece mirror-polished with diamond paste, and the integrated intensity I of the (111) plane of the tetragonal product and the (111) plane of the cubic crystal. From T+IC, the amount of monoclinic crystal was determined by the following formula. Next, the sintered body was finely pulverized to 5 μm or less, and monoclinic Zro2 and cubic Z were determined by X-ray diffraction under the same conditions.
The integrated intensity IMyIC of rO2 was determined.

That is, during this pulverization process, all the tetragonal ZrO2 present in the sintered body was converted into monoclinic ZrO2 due to mechanical stress.
It is thought that it metamorphoses into 2. Therefore, the cubic crystal was determined by the following, and from this the square product amount was then determined.

1+HPLX 8A l/...h4 n % +/-h -1-14n% 1 Table 1 is as follows:
ZrO2 containing 2ωo1% of Y2O as a stabilizer,
The amount of 3 A I203 .2 S io 2 (mullite) added was gradually increased. Sample No. 1, which is a comparative example that does not contain any mullite, has a high density, but has low fracture toughness and bending strength, and has a large amount of transition to mullite monoclinic crystal. On the other hand, No. 2 to No. 5 containing mullite within the composition range of the present invention showed high values for both fracture toughness and bending strength, and it was confirmed that most of the crystal phases were made of tetragonal items. It was done. On the other hand, it became clear that in Comparative Examples No. 6, in which mullite was added in an amount exceeding the composition range of the present invention, both fracture toughness and bending strength deteriorated extremely.

Table 2 shows Z containing 2+ao1% of Y2O as a stabilizer.
3 A I203 .2 S io 2 (mullite) and Al2O3 are added to rO2 in various proportions and amounts. Samples No. 7, in which neither Murai Shigeru nor A1□O5 were added, did not have the desired strength, and the crystal phase also underwent a large transition to monoclinic. On the other hand, it was found that the addition of mullite and A I20 within the composition range of the present invention yielded a good flexural strength, and the crystal phase was also mostly tetragonal. On the other hand, No. 2 is a comparative example containing mullite and A I 20 ) in an amount above the composition range of the present invention.

Regarding No. 14, it was confirmed that satisfactory strength could not be obtained.

(Example 2) To a zirconia sol solution obtained by hydrolyzing zirconium oxychloride with a purity of 99.9%,
of indolium chloride was added, and the uniformly mixed solution was coagulated to form a precipitate, which was dehydrated and dried and calcined at 850°C to obtain Y, 20. A partially stabilized zirconia powder was obtained.

This powder exhibits a specific surface area of 35II12/g. This powder was added with 3Al□0.0% obtained by the method of Example 1.・2SiO
2 (mullite) and A1□O1 with an average particle size of 0.3μ and a purity of 99.9% were added in the proportions shown in Tables 3 and 4, and the powder was wet mixed and dried under a pressure of 1.5 ton/Cm2. It was shaped squarely and fired in air at a temperature of 1400-1600'C for 2 hours. The average crystal grain size of the obtained sintered body was all 3 uml2Ti·fu-bj,Anot.The obtained sintered body was cut and polished to 3X4X40+am, and the density, crystal phase, Transverse bending strength.

The fracture toughness was measured and the results are shown in Tables 3 and 4.

Table 3 shows ZrO2 containing 2I6o1% of Y2O as a stabilizer, in which large amounts of 3Al2O, 2SiO2 (mullite) were sequentially added.No. 15 is a comparative example in which no mullite was added. , fracture toughness.

Both the bending strength is low and the amount of transition to monoclinic crystal is large. On the other hand, N containing mullite within the composition range of the present invention
It was confirmed that samples No. 0, No. 16 to No. 20, showed high values for both fracture PJ toughness and bending strength, and that most of the crystal phases were made of tetragonal products. In particular, it is noteworthy that the strength is higher than that of Example 1.

Although No. 21 is a comparative example containing mullite in a content exceeding the composition range of the present invention, both fracture toughness and bending strength are extremely deteriorated.

Table tpJ4 shows the addition of various amounts of Zr0zl:3AI203.25i02 (mullite) and A12o3 containing 2n+o1% of Y2O as a stabilizer. No.

No. 22 is a comparative example in which mullite and A120i are not added at all, but the desired strength is not obtained and the crystal phase also undergoes a large transition to monoclinic. On the other hand, N containing mullite and c/Al2O1 within the composition range of the present invention
Nos. 0, 23 to 29 have sufficiently high fracture toughness and bending strength, and most of the crystal phases are square. No. 30 is mullite and A1□0. Although it is a comparative example containing more than the composition range of the present invention, it was found that satisfactory strength could not be obtained.

(Example 3) Purity 9 was adjusted so that the composition of the powder obtained was in the proportions shown in Table 5.
A purity of 99% was added as a stabilizer to a zirconia sol solution obtained by hydrolysis of 9.9% norconium oxychloride.
．． 9% of iF chloride, cerium chloride, magnesium chloride, and calcium chloride were added, and the uniformly mixed solution was coagulated to form a precipitate, which was dehydrated and dried and calcined at 850°C to obtain a ratio of 35II12/g. A partially stabilized zirconia powder having a surface area was obtained.

To this powder, 3Al□0 obtained by the method of Example 1,
2SiO2 (mullite) and average particle size 0.3μ, purity 9
9.9% of A I20 was added in the ratio shown in Table 5, and the powder was wet mixed and dried, then isotropically molded at a pressure of 1.5 ton/cm2, and heated at a temperature of 1400 to 1650°C in the air at 2 Baked for an hour. The average crystal grain size of the obtained sintered bodies was all 3 μ' or less.

The obtained sintered body was cut and polished to 3 x 4 x 40 mm.
Density, crystal phase, bending strength, and fracture toughness were measured using the same measuring methods as in Example 1, and the results are shown in Table 5.

In Table 5, samples No. 31 to No. 37 contain Y 20 ) as a stabilizer in various proportions, and 3
Δ120.・2 S io 2 (mullite) 12.5%
, and Al2O, 12.5%. N
No. 31 is a comparative example in which the Y2O3 concentration was not sufficient, but it collapsed during the firing, and the crystal phase also completely changed to monoclinic. Y2 in the composition range of the present invention as a stabilizer
Sufficiently high fracture toughness and bending strength were obtained with No, 32-No, 38 to which O was added. On the other hand, No. 37 is a comparative example containing Y2O3 in a larger amount than the composition range of the present invention, but like No.:tl, it collapsed during firing.

No. 38- No. 42 contains CeO2 as a stabilizer, 12.5% each of mullite and AI203.
In this example, Ce below the composition range of the present invention is blended.
In No. 38 containing O2, it collapsed during firing and the characteristic values could not be measured. On the other hand, No. 2, to which CeO was added as a stabilizer within the composition range of the present invention,
39~No, 42 has high fracture toughness and bending strength,
No. 43 is an example containing MgO as a stabilizer within the composition range of the present invention, No. 44 is an example containing CaO as a stabilizer within the composition range of the present invention, and mullite and V A I, respectively. 20* in an amount of 12.5% each, satisfactory results were obtained in both cases.

No. 45 to No. 55 are examples in which Y2O3 and CeO2 were added as stabilizers in various ratios and amounts, and 12.5% of mullite and 81□O1 were each added. N
o.

45 is a comparative example in which the addition amounts of Y2O and CeO2 are both below the composition range of the present invention, but Y2O collapses during firing and the crystal phase changes to 100% monoclinic.
N containing 2O3 and CeO2 within the composition range of the present invention
o, 46-No, 51 and No, 53-No,
No. 54 showed high values for both fracture toughness and bending strength, and almost no transition to monoclinic crystal phase was observed. However, Y
This is a comparative example in which the amounts of 2O and CeO2 added exceed the range specified in the present invention in terms of mixing ratio.

In No. 52 and No. 55, the strength is seriously deteriorated and the force t1! (Example 4) Using the sintered bodies prepared by the methods of Examples 2 and 3, a hydrothermal deterioration test was conducted in steam at 145°C using an autoclave. The amount of monoclinic crystals on the sample surface was measured, and the relationship between the amount of monoclinic crystals and the retention time is shown in FIG. In addition, a thermal deterioration test was performed by holding the sample in an electric furnace at 300°C for a predetermined time, and the amount of monoclinic crystal on the surface of the sintered sample was similarly measured.
Similarly, the relationship between the monoclinic crystal 11t and the retention time is shown in FIG.

In Figures 1 and 2, No, 15 is 3A +2
This is a comparative example outside the composition range of the present invention, which does not contain all 0, -28iO2 (mullite), No.
This is a comparative example in which a zirconia sintered body containing no 20,.2SiO2 (mullite) was fired at 1500° C. for 2 hours and yielded no C2. No, 18 is 2m as a stabilizer
ol% of Y2O, and 25% by weight of 3AI□O
This is an example of the present invention containing 1.2SiO2 (mullite), and No. 48 contains 2 mol% of Y2O3 as a stabilizer and 1% of CeO2 as a stabilizer, and 12.5% by weight of 3AI203.2SiO2 (mullite). and 12.5% by weight of Δ1□O1.

As is clear from FIGS. 1 and 2, the comparative example N
In No. 15, the amount of monoclinic crystals increased in a very short time on the surface of the sintered body due to the hydrothermal deterioration test in an autoclave, and the amount of monoclinic crystals increased the most in the thermal deterioration test. and,
It was observed that fine cracks and intergranular fracture occurred on the surface of the sintered body, while fine monoclinic ZrO2 particles precipitated and turned white.

On the other hand, in No. and X, the amount of monoclinic crystals increases at once in a relatively short period of time in hot water, and thereafter increases somewhat gradually. Similar results were also shown in the thermal deterioration test, with a significant increase in the amount of monoclinic crystals on the surface of the sintered body, cracks occurring at the sample edges, and deterioration was severe.

On the other hand, invention examples No. 18 and No. 48 are:
Even after hydrothermal deterioration and thermal deterioration tests, the increase in the amount of monoclinic crystals on the sample surface was extremely small, only a few dozen percent or less, and it was found that the sample exhibited extremely high stability in heat and hot water.

(Example 5) Samples No. 19 and N obtained by the methods of Examples 2 and 3
o, 48 and sample No. X, which is a comparative example used in Example 4.
The high temperature strength was measured using No. 19 is an example of the present invention in which 40% mullite was added to the raw material obtained by co-precipitating a zirconia sol solution and yttrium chloride.
No. 48 is an example of the present invention in which 12.5% each of alumina and mullite was added to the raw material obtained by co-precipitating a norconiacyl solution with yttrium chloride and cerium chloride.

The high-temperature strength was measured in the same manner as the bending strength measurement in Example 1, by holding the sample at 500°C, SOO°C, and 1000°C, and measuring the bending strength. The measurement results are shown in FIG. 3, with the vertical axis representing the bending strength and the horizontal axis representing the holding temperature.

As is clear from Figure i3, No. 19 of the present invention example.
It was confirmed that the high-temperature strength of samples No., No. 48, and No. 48 were all improved compared to the comparative examples No. and X. In particular, No. 48 was found to have little decrease in strength at high temperatures.

(Example 6) A piece of blood child 112 in 1 > P in M818, No, 19, No, 26 and Comparative example No, X in Example 4 25 The coefficient of thermal expansion was measured from °C to 1000 °C and shown as a thermal expansion curve in Figure 54. The coefficient of thermal expansion is also shown for each sample.

Comparative examples No. and X do not contain mullite at all, so their thermal expansion coefficients are 11. The highest is 1Xl0~', while No. 26, which contains 12.5% mullite, is 9.4X10~', and No. 18, which contains 25% mullite, is 8.9X10~'.
, No containing 40% mullite, 19 is 7,9X10
~', and it was confirmed that the value of the thermal expansion coefficient decreases depending on the amount of mullite added.

In addition, in all of the examples of the high-toughness zirconia sintered bodies of the present invention shown above, the desired characteristics were obtained by firing in the air at 1400 to 1650°C for several hours.
In a vacuum, in an inert gas such as N2 or Ar, in a carbon atmosphere,
Firing in an atmosphere such as hydrogen or oxygen, hot pressing, H
Similar results can be obtained by using ceramic firing techniques such as IP.

〔Effect of the invention〕

The high toughness zirconia sintered body of the present invention comprises Y, O, Ce.
3A1203.2SiOz (mullite) component or 3A1203.2Si○2 (mullite) and A1□0. By adding new components, it shows excellent strength at room temperature, and has excellent heat and hot water stability at 200 to 400 °C, which is conventionally considered unstable. (mullite) component or 3A+□03.2 S io 2 (mullite) and A1□0. The ingredients have a significant suppressive effect on thermal and hydrothermal degradation.

Also, 3A120.・Acicular crystals, which are the 2SiOz (mullite) component, are finely dispersed in the partially stabilized zirconia sintered body and control the microstructure of the sintered body, so they improve the strength and strength of the partially stabilized zirconia sintered body at high temperatures. Mechanical properties such as creep properties can be significantly improved.

Furthermore, 3Al□O1・2Si02 contained in the sintered body
(Mullite) By controlling the amount of heat, it is possible to lower the thermal expansion coefficient of partially stabilized norphea and control it to a desired value.

On the other hand, from the perspective of a sintered body of 3A+203.2SiO2 (mullite), the strength of mullite, which conventionally only has a room temperature strength of 20 to 30 Kg/Ia+12, can be increased to more than four times the strength. .

In addition to this, the high toughness zirconia sintered body of the present invention contains Zr.
Since the raw material obtained by uniformly mixing O2 sol and/or water-soluble salt with the water-soluble salt as a stabilizer and separating it in the form of precipitate is used, it does not contain micropores, has high density and high strength. It is possible to obtain a sintered body of.

The high-toughness zirconia of the present invention, which satisfies not only high strength and toughness but also thermal stability, especially hot water stability, can be used, for example, in injection molding (composition) of thermoplastic resins and ceramics that are subjected to heat and pressure. In addition to wear-resistant ceramic screws and nozzles, it is also ideal for dies such as brass rods and copper tube shells.In addition, it is suitable for cutting tools, industrial power caps, dies,
Internal combustion engines, pumps, artificial bones, artificial teeth, artificial tooth roots, sliding parts, bridge core materials for artificial teeth made of artificially cast ceramics,
This will greatly contribute to the practical application and performance improvement of precision machine tools, high-temperature furnace parts, etc.

[Brief explanation of the drawing]

Figure 1 shows the time and monoclinic j7t of the hydrothermal deterioration test in Example 4.
Figure 2 is a diagram showing the relationship between the time of the thermal deterioration test and the amount of monoclinic crystal in Example 4, and fjS3 is a diagram showing the relationship between Example 5.
Figure f54 is a diagram showing the relationship between the holding temperature and bending strength in the high-temperature strength test.

Claims (1)

[Scope of Claims] 1 Partially stabilized zirconia mainly consisting of tetragonal crystal containing one or more selected from Y_2O_3, CeO_2, MgO, and CaO as a stabilizer, and 0.5 to 6
3Al_2O_3・2SiO_2 in the range of 0 internal weight%
(mullite) or Al_2O_3 and 3Al_2O_3
- A high toughness zirconia sintered body containing 2SiO_2 (mullite) and having an average crystal grain size of 3 μm or less. 2 Partially stabilized zirconia is produced by uniformly mixing ZrO_2 sol and/or water-soluble salt with a water-soluble salt of a stabilizer in a solution state, and then separating the resulting raw material in the form of a precipitate. Claim 1 characterized in that the use of
High-toughness zirconia sintered body as described in . 3 The amount of stabilizer added is internal mol relative to ZrO_2.
%, Y_2O_3 is 1 to 6 mol%, CeO_
2 is 7-15 mol%, MgO is 3.0-10 mol%
The high-toughness zirconia sintered body according to claim 1, wherein CaO is in the range of 2 to 8 mol%, and when two or more types are mixed and added, the content is within the above content range in the respective mixing ratios. 4. The high toughness zirconia sintered body according to claim 1, wherein part or all of ZrO_2 is replaced with HfO_2.