JPS6177665A - High tenacity zirconia 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 [Field of Industrial Application] The present invention relates to a high-toughness zirconia sintered body, and more specifically to ZrOt-Y2O-CeO-based zirconia containing ZrO□ and Y2O as a stabilizer, and CeO. At
20, and relates to a high-strength, high-toughness norconia sintered body that exhibits extremely little deterioration over time due to long-term use in a specific temperature range.

[Prior art]

A zirconia sintered body undergoes a phase transition from cubic to tetragonal to monoclinic in the high-temperature range, but this is accompanied by a change in volume, and the volume change during the phase transition from tetragonal to monoclinic is particularly large (because of this, There is a drawback that the sintered body is destroyed due to this volume change.In order to eliminate this drawback, Ca
A large number of stabilized zirconias made of cubic crystals or partially stabilized zirconias made of cubic and monoclinic crystals have been published by dissolving O + MtlO + Y 20, etc. in solid solution to prevent transitions. Furthermore, it has been announced that partially stabilized zirconia, in which a metastable phase of tetragonal crystals exists in a sintered body at room temperature, exhibits high strength. As described above, Y2O3 has conventionally been used as a stabilizer to obtain a sintered body mainly consisting of tetragonal or cubic crystals at room temperature, and it exhibits high toughness and strength. However, this partially stabilized zirconia, which is mainly composed of tetragonal crystals, is a metastable phase resulting from bringing a high temperature phase to a low temperature range, so its structure and properties change over time, especially when compared to temperatures between 200°C and 400°C. Heating at extremely low temperatures causes a phase transition to monoclinic crystals, resulting in extremely large deterioration of strength over time.

Since the aging of such a partially stabilized zirconia sintered body depends on the composition of the stabilizer, the composition of the sintered body, or the crystal grain size, we identified Y-OhfA as a stabilizer,
It has been reported that by obtaining a sintered body mainly consisting of square parts and controlling the crystal grain size during the manufacturing process of the sintered body, a sintered body with high strength and high toughness that exhibits little deterioration over time in a specific temperature range ( Nete Kai 56-13456'4).

In addition, based on the knowledge that At203 is dissolved and dispersed in Z r O2, it lowers the temperature at which the tetragonal Z r Ot transforms to monoclinic and suppresses the grain growth of Z r Ov. r At to Ov-based zirconia
It has been reported that the strength is improved by adding the 201 component (Japanese Unexamined Patent Publication No. 58-32066).
In the manufacturing process of a sintered body in which Z is dissolved and dispersed, Z
A sintered body with excellent strength and almost no micropores can be produced by combining the water-soluble salts of each component (rO2, stabilizer, and At203) in a predetermined ratio and using the raw material obtained by coprecipitation. It is disclosed that the obtained
-369761. On the other hand, as a method for producing fine powder used in the production of norconia-based sintered bodies, a method has been announced in which a monoclinic norconia secondary particle sol produced by heating and hydrolysis of a zirconia salt aqueous solution is used. It is disclosed that sintering at 1300°C under normal pressure produces a sintered body with almost theoretical density (
JP 58-135131).

Ce Or is the - of the stabilizer of Z r O2, but from the phase equilibrium diagram, the Cent Zr0z system is Y+0i-Z
Compared to the rO
It has been announced that it has high strength with an r content of 10 to 12 mol % and is more thermally stable than Y, O, systems (1983 Nitrogen Industry Basic Conference IA, p. 6.10). Also, Y2O5Zr
By adding CeO2 to the O, system, sintered bodies consisting only of square pieces can be obtained over a wide composition range, and the simultaneous addition of Ce0= allows for sintering that is stable and exhibits high toughness even after long-term thermal enlongation. (May 1984 Ceramics Association Annual Meeting, 124P46)
3).

[Problem that the invention seeks to solve]

However, in a zirconia sintered body in which Y 2031 was specified as a stabilizer and the grain size of the sintered body was controlled, although aging deterioration in a specific temperature range was improved, Zr0z stabilized with ittria was thermally is extremely unstable and still has insufficient strength, so its use as a groove material is limited. Also, At 20 s
Although the Y20) -ZrO2-based zirconia sintered body in which Y20)-ZrO2 is solid-dissolved and dispersed has high strength at room temperature, its thermal stability is similarly extremely insufficient and essentially unimproved, making it difficult to use in actual use. There are serious drawbacks such as a decrease in strength and deterioration of the crystal structure. Affi to this Y2O5ZrO+ system
Sintered bodies made from powders obtained by co-precipitation of water-soluble salts in the preparation of sintering powders in systems in which xO3 is dispersed as a solid solution also have high strength at room temperature, but there is no improvement in thermal performance. It is unstable.

In addition, the conventional manufacturing method for easily sinterable zirconia powder uses an aqueous solution of norconium salt, and the coprecipitation method is the most common manufacturing method. A method of manufacturing the fine powder used is disclosed. However, even with these raw material preparation methods, the obtained sintered bodies are not satisfactory in terms of density, strength, and toughness. It is believed that these properties would be further improved if a powder capable of providing these properties could be obtained. In addition, a system containing CeO2 as a stabilizer, that is, C
e O2-Z r O2M and Y 20, - Z ro
2- CeO2-based sintered bodies have insufficient strength, and although they exhibit thermal stability, they are not satisfactory, and even more important are the strength and thermal stability, especially the thermal stability in the presence of water, etc. If its properties are changed, it is thought that the range of use of zirconia as a viscous material can be greatly expanded.1 The present invention furthermore dramatically improves the thermal properties of high-toughness zirconia stabilized by Y 20 y. 1) It provides a thermally extremely stable sintered body that has excellent mechanical properties and is free from thermal deterioration.

Means for Solving Problem C] The high toughness zirconia sintered body of the present invention is made of ZrOt-YO
1.5 Consists of CeO2M composition, Y O1,s is 0
YOl, , and C/Ce Or
The total amount of Zr is 3.5 to 15.5 mol%, and the balance is Zr.
The sintered body is characterized in that partially stabilized norphea mainly composed of tetragonal crystals, designated as 01, contains At 203 in a range of 0.5 to 70 mfi%, and the average crystal grain size of the sintered body is 3 μm or less.

This partially stabilized zirconia is obtained by uniformly mixing a sol and/or a water-soluble salt of Z r Oz with a salt of an aqueous solution of Y 20 s and CeO2 in a solution state, and then separating it in the form of a precipitate. It is characterized by the fact that it uses fresh raw materials.

Furthermore, At 2 contained in the above partially stabilized zirconia
When mixing the 0 v component with Zr02t YzOl and the Cent component in a solution state, use a raw material obtained by uniformly mixing a sol and/or aluminum salt in a water-soluble state and then separating it in the form of a precipitate. It is meant to be kept as money.

[Effect]

The high toughness zirconia sintered body of the present invention is different from the conventional YHO5Z
By newly adding the Ceo2 component to the rO2-hetzoz-based high-91 norconia sintered body composition, it is more thermally unstable than before, even after long-term thermal deterioration tests in the temperature range. This is a tetragonal zirconia crystal stabilized by the addition of Cart. The structure is conventional Y
than tetragonal zirconia stabilized by 2O3.
This is thought to be because the crystal structure is closer to the cubic crystal structure, which is the high-temperature stable phase of zirconia. The reason why the composition ranges of YO1.5 and CeO2 are limited in the present invention is as follows. If YO,... is less than 0.5 mol%, its addition as a stabilizer has no effect;
This is because if YO1.5 exceeds 15 mol %, mechanical properties such as bending strength and toughness will decrease rapidly. This is because if CeO2 is less than 0.5 mol%, it is thermally unstable and its addition has no effect, and if CeO□ exceeds 15 mol%, mechanical properties such as toughness and bending strength are lost. Also,
This is because when the total amount of YO1.
This is because if the total amount of 5 and CeO2 is less than 15.5 mol%, mechanical properties such as toughness and bending strength will deteriorate.

Since the zirconia sintered body having the composition of the present invention is partially stabilized zirconia mainly composed of square pieces, it has high strength and
Since the tetragonal crystal, which exhibits high toughness, is a stable phase, part of it transforms into a monoclinic crystal by grinding the sample surface, 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 composed of tetragonal crystals according to the present invention is characterized in that, in the measurement of the crystal phase by X-ray diffraction, more than 90% of the crystal phase in the mirror state is occupied by the tetragonal system and/or the cubic system. The ratio of the system is 1=4
The above refers to Zr0z. If the total ratio of tetragonal and cubic crystal systems is less than 90%, the toughness will be low, so it is necessary that the cracking ratio between the tetragonal and cubic systems is 9()% or more. If the ratio is less than 1:4, the toughness will be low, so this ratio needs to be 1:4 or more.

Since the zirconia sintered body of the present invention contains At 20 s in a range of 0.5 to 70% by weight, it has excellent toughness and strength. This is 8Q, 0. This is thought to be because the effect of alumina as a sintering aid helps remove defects, and the addition of alumina increases the elastic modulus, contributing to an increase in fracture energy. Al□0. The reason for limiting the addition amount to 0.5 to 70 heavy weight galore is that 8N + Oy is 0°5! I! If the amount is less than 70% by weight, the addition effect will be poor, and if it is more than 70% by weight, the content of Z'02, which has toughness, will be lowered and sufficient values for both strength and toughness will not be obtained.

The sintered body of the present invention needs to have an average crystal grain size of 3 μm or less. When the average crystal grain size exceeds 3μ, the tetragonal structure changes to a monoclinic structure and the toughness decreases.

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 with a water-soluble salt of Y2O5 and CeO□ in a solution state, and then separating it in the form of a precipitate. Since Y2O and CcO2 components are uniformly dispersed in ZrO2, an easily sinterable powder consisting of extremely fine particles can be used as a raw material. the result,
A sintered body having fine grains, a uniform I/L texture, and almost no micropores can be obtained, and desired values of strength and thermal stability can also be obtained.

The At 20 s component of the present invention has Z ro 2. Y 2
0 When mixing the y-CeO2 component in a solution state, we use a raw material obtained by homogeneously mixing the sol/aluminum salt in a water-soluble state and then separating it in the form of a precipitate. , fine particles can be uniformly dispersed in the zirconia sintered body. As a result, the effect of adding AI 203 to the zirconia sintered body as described above can be fully obtained.

Furthermore, even if one or more of the Z r O2 in the zirconia sintered body of the present invention is replaced with HfO, it exhibits exactly the same characteristics.

〔Example〕

Hereinafter, the present invention will be explained in detail with reference to Examples.

('J Kojima 1) I: The powder that is L is Ill'! To the norconiacyl solution obtained by hydrolysis of the okine norfnium chloride solution of purity 9":) and 996, yttrium chloride of purity 99.9% and purity 9" were added to the norconiacyl solution obtained by hydrolysis of okine norfnium chloride solution of purity 9":) so as to have the proportions shown in Tables 1 and 2.
9.9% cerium chloride was added and the uniformly mixed solution was coagulated to form a precipitate, which was dehydrated and dried at 850"C.
The mixture was calcined to obtain partially stabilized zirconia powder. This powder exhibits a specific surface area of 35 m"/g. At 203 with an average particle size of 0.3 μ and a purity of 99°9% was first added to this powder.
Add the powder in the proportions shown in Tables and Table 2 and dry it after wet mixing at a pressure of 1.5 ton/am2 t"!? Jf
The sample was fired in the atmosphere at 1400-1650°C for 2 hours. The average crystal grain size of the obtained sintered bodies was all 3 μm or less.

The obtained sintered body was cut and polished to a size of 3×4×40 mm, and the flexural strength, fracture toughness, crystal phase of the sintered body surface after the thermal deterioration test, and flexural strength were measured. In addition, as a method for measuring each physical property, the bending strength is 3X4X40 according to JIS regulations.
The average value of 10 specimens was determined by three-point bending at a span of 3011 mm and a crosshead speed of 0.5 mm. Fracture toughness was measured by making an indentation with a load of 50 kg using the micro-indente run method.
The KIC value was calculated using Shinryo et al.'s formula. Quantitative measurement of crystalline phase is
The analysis was carried out using the X-repetition diffraction method. That is, the monoclinic (111
) surface and (11 pieces) surface and the (1
The integrated intensity I T of the 111 plane and the cubic (111) plane,
From I C, the amount of monoclinic crystal is (amount of monoclinic crystal) = −”L−Y
1O0・・・・・・Determined by the formula (1) 1 unit IC”L
The integrated intensity of monoclinic ZrO2 and cubic ZrOr was determined by X-ray diffraction under the same conditions after pulverizing the sintered body.
IC9: Fc, that is, it is thought that all the tetragonal Z'0. existing in the sintered body during this pulverization process transforms into monoclinic Z'0. due to mechanical stress, Y1O0...
... (2) was determined, and from this, square items and mice were determined next. Thermal deterioration test was carried out at 250°C in an electric furnace at 300°C.
After holding for 0 hours, the sample was taken out and its physical properties were measured.

Heat deterioration test 9. The lit oblique crystallization of tl was similarly determined from the above equation (1) by X-ray diffraction of the sample surface.

In samples Nos. 1 to 36 in Table 1, the composition of 8t203 was 25
YO, S was fixed at 0.5 mol% to 15% by weight.
Ce O2 was added in various mol % in a stepwise manner up to mol %. Also, sample N in Table 2
For o37 to No671%, the mole% of Yl was fixed at 4%, and the m1% of At203 was increased stepwise from 0.5% to 80%, and CEO2 was added in various mole%. . As is clear from the results in Tables 1 and 2, the high toughness norconia sintered body of the present invention
, compared to the sintered body stabilized only by At
Regardless of the amount of the 101 component, the transition from a square product to a 3p diagonal product is significantly suppressed by the addition of Ce0, and the product maintains high strength even after a long-term thermal deterioration test in a specific temperature range. confirmed. In addition, it was found that the comparative example, which falls outside the composition range of the present invention, did not suppress the transition to monoclinic crystal and had poor strength after the thermal deterioration test.

(Example 2) The purity was adjusted to 99.9 so that the powder obtained had the proportions shown in Table 3.
A zirconia sol solution obtained by hydrolyzing a silconium oxychloride solution of 99.9% purity and 99.9% purity cerium chloride, and further added aluminum with a purity of 99% or more. Add alumina sol prepared from isopropylate to coagulate the uniformly mixed solution, dehydrate and dry this as a precipitate, and precipitate at 800°C.
A raw material powder was obtained by baking. This powder has a primary particle size of 200 A. This powder was isotropically molded at a pressure of 1.5 ton/am" and fired in the air at a temperature of 1400 to 1650°C for 2 hours. The solids were measured in the same manner as in Example 1. For comparison, the specific surface M
Using Zr01 powder with a purity of 99% or more of i25+s''/g, CeO2,y,0. A
The results are shown for a sample in which 12O was added in the proportion shown in the m3 table, and the powder was wet-mixed and then dried, and then molded and fired in the same manner. From the results in Table 3, the sintered body using the raw material prepared from the sol does not contain micropores and has a uniform dispersion of each component, resulting in a higher density and higher density compared to the powder mixture.
It can be seen that it exhibits high strength and higher thermal stability.

(Example 3) Using a 311Sl sintered body by the method of Example 1, using an autoclave, in distilled water at 145 ° C.
A thermal deterioration test was carried out to determine the amount of monoclinic crystal on the surface of the sintered sample. (Y)
O, , mol%, CeO mol%.

At20, 11t%), and NoA and NoB are partially stabilized zirconia/2 solids made only of Y2O in the comparative example. As a result, it was found that the sintered body of the present invention, which contains CeO2 and At201 components and has almost no thermal deterioration in a specific temperature range of 171, exhibits markedly high stability even in hot water.

In addition, in all of the examples of the high-toughness zilphnia sintered bodies of the present invention shown above, the desired characteristics were obtained by firing at 1400-1650°C for several hours in the air.
Similar results can be obtained by using atmosphere firing in vacuum, hydrogen, or oxygen, hot pressing, or HIPk4 cetemic firing techniques.

〔Effect of the invention〕

The high toughness norconia sintered body of the present invention is a conventional Y2O5~Z
r0a High toughness of the AlaOs system: y = 7a Aggregate composition composition By newly adding the O2 component, thermal deterioration V over a long period of time in a temperature range that is conventionally considered to be thermally unstable, even after testing. The high-toughness norconia sintered body of the present invention exhibits extremely high strength with almost no change, and exhibits extremely high stability even in hot water where VF is said to cause severe deterioration. It is a raw material obtained by mixing uniformly with the water-soluble salt of the additive component and then separating it in the form of a precipitate. Since the raw material obtained by mixing 202 sols and separating them in the form of precipitate is used, it does not contain micropores and each component is uniformly dispersed, resulting in high density, high strength, and higher thermal stability. A sintered body can be obtained. The high-toughness zirconia of the present invention, which satisfies not only high strength and high toughness but also thermal stability, can be put to practical use in cutting tools, dies, internal combustion engines, pumps, artificial bones, M-density mechanical engineers, etc. This greatly contributes to improved performance.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between the time of the thermal deterioration test and the amount of monoclinic crystals in Example 3.

Claims (1)

[Claims] 1 ZrO_2-YO_1_. _5-CeO_2 system composition, YO_1_. _5 0.5 to 15 mol%, C
In the composition range containing eO_2 from 0.5 to 15 mol%, YO_1_. The total amount of _5 and CeO_2 is 3.5
~15.5 mol%, with the balance being ZrO_2, partially stabilized zirconia mainly consisting of tetragonal crystals, and 0.5~15.5 mol%
A high-toughness zirconia sintered body containing Al_2O_3 in a range of 70% by weight, and having an average crystal grain size of 3 μm or less. 2. Partially stabilized zirconia uses a raw material obtained by uniformly mixing ZrO_2 sol and/or water-soluble salt with Y_2O_3 and CeO_2 water-soluble salts in a solution state, and then separating it in the form of a precipitate. A high-toughness zirconia sintered body according to claim 1, characterized in that: 3 Al_2O_3 is ZrO_2, Y_2O_3, C
When mixing with the eO_2 component in a solution state, the sol and/or
Alternatively, the high toughness zirconia sintered body according to claim 1, characterized in that a raw material obtained by uniformly mixing an aluminum salt in an aqueous solution and then separating it in the form of a precipitate is used. 4. The high-toughness zirconia sintered body according to claim 1, wherein part or all of ZrO_2 is replaced with HfO_2.