JPH0678186B2 - Zirconia sintered body - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention has high strength and high toughness characteristics, and can reduce environmental deterioration and reliability by reducing deterioration of these characteristics over time. It relates to a sintered body.

[Prior art and its problems]

It is known that a ceramic sintered body is a material having poor toughness, whereas a partially stabilized zirconia sintered body is attracting attention as a material for improving this drawback. This partially stabilized zirconia (Partially Stabilized-Zirconia,
Hereinafter, this sintered body is abbreviated as PSZ). In manufacturing the sintered body, various stabilizers such as MgO, Y ₂ O ₃
Obtained by adding an appropriate amount of aO etc. and baking,
It is said that the crystal phase of this PSZ sintered body is mainly characterized by a tetragonal phase or a mixed phase of a tetragonal phase and a cubic phase.

Thus, since this PSZ sintered body has high strength and high toughness characteristics in addition to the excellent corrosion resistance of ceramics itself, it is widely used for various daily necessities such as scissors and knives, various members in vivo, parts for industrial machines, etc. Has been done.

However, if various members made of this PSZ sintered body are used for a long period of time, or if they are used at high temperature or in a steam atmosphere or with contact with water, the deterioration of strength and toughness becomes remarkable. It is believed that water and heat accelerate the transformation of the tetragonal phase to the monoclinic phase so far.

[Object of the Invention]

The present inventor, as a result of earnest research in view of the above circumstances, PSZ sintered bodies containing Dy ₂ O ₃ and CeO ₂ as stabilizers in a predetermined range are excellent in water resistance and heat resistance. I found that.

Therefore, the present invention has been completed based on the above findings, and its purpose is to have high strength and high toughness characteristics, as well as excellent thermal stability and water resistance, which results in high quality and high reliability of zirconia firing. To provide a union.

[Means for solving problems]

According to the invention, it consists mainly of ZrO ₂ and contains 0.5-4.5 mol% Dy ₂ O ₃ and 2-8 mol% CeO ₂ and also Dy ₂
A zirconia sintered body having a total content of O ₃ and CeO ₂ of 6 mol% or more and having a crystal phase mainly composed of a tetragonal phase or a mixed phase of a tetragonal phase and a cubic phase is provided.

The zirconia sintered body of the present invention is subjected to the severe test described below, that is,
Hot water treatment tests (such tests are typically performed by Process Cooker
It is called Test, and hereinafter, even if this is abbreviated as PCT), if the above stabilizer is blended within a predetermined range, the monoclinic phase in the ZrO ₂ crystal phase is suppressed to 50% by weight or less, As a result, a high-reliability PSZ sintered body in which the strength and toughness of the sintered body are less deteriorated over time is obtained.
It has a bending strength of not less than kg / mm ² ).

The PCT according to the present invention is to leave a PSZ sintered body in hot water under a boiling condition of 121 ° C. and 2 atm for 100 hours,
This is to follow the change in monoclinic phase content before and after PCT.

According to the present invention, it is important that the stabilizer contains 0.5 to 4.5 mol% of Dy ₂ O ₃ and ₂ to 8 mol% of CeO ₂ .
If the Dy ₂ O ₃ content is less than 0.5 mol%, the monoclinic phase is contained in an amount of 50% by weight or more even in a sintered body before PCT, and cracking is likely to occur during sintering. When it exceeds, the strength is remarkably reduced. Further, when CeO ₂ is less than 2 mol%, the monoclinic phase is increased to 50% by weight or more by PCT, and when it exceeds 8 mol%, the strength tends to be lowered.

The total content of Dy ₂ O ₃ and CeO ₂ is 6 mol%
It is also important that the amount is less than 6 mol%, and PCT increases the monoclinic phase to 50 wt% or more.

Further, the present inventors have found that the preferred contents of Dy ₂ O ₃ and CeO ₂ are
It was found to be in the range of 0.5-2.5 mol% and 5.5-7.5 mol%. Within this range, the amount ratio of the monoclinic phase can be reduced to 30% by weight or less even after PCT and 55 Kg / mm ²
The above high strength characteristics can be obtained.

For the main component ZrO _2, it is preferable to contain 80 mol% or more in the whole sintered body, preferably contained in the range of 87.5 to 94 mol%, and within this range, PSZ itself has high strength. Moreover, the high toughness characteristics become remarkable.

According to the present invention, in addition to the stabilizer and the compounding ratio thereof, the average crystal grain size in the sintered body is 2 μm or less, preferably 1 μm.
It is desirable to set it to m or less. If it is within this range, the precipitation of monoclinic phase is further suppressed, and PS of high strength and high toughness is obtained.
It becomes a Z-sintered body, and even after PCT, it is relatively easy to reduce the precipitation amount of the monoclinic phase to 50% by weight or less in the total ZrO ₂ crystal phase.

Furthermore, the PSZ sintered body of the present invention essentially comprises the above-mentioned _two components, the ZrO ₂ main component and the stabilizer, but does not exclude the inclusion of other components. For example, within 30% by weight of the stabilizer of Dy ₂ O ₃ or CeO ₂ , other stabilizers such as oxides of rare earth elements, CaO, MgO may be substituted, or mixed powder of zirconia and stabilizer. When a grinding medium such as a ball is used during body work, the components that make up this grinding medium will necessarily be contained in the mixed grinding product, such as alumina (Al ₂ O ₃ ), which is It is allowed to mix up to 3% by weight with respect to the entire sintered body. In addition, unavoidable impurities such as SiO ₂ and Fe _{2 which} are inevitably mixed when using the zirconia raw material.
O _3, etc. TiO _2, Nb ₂ O ₅ also be incorporated up to 3% by weight per total sintered body is allowed. The ZrO ₂ raw material may contain HfO ₂ which is difficult to separate.

Further, the amount of monoclinic phase of the PSZ sintered body according to the present invention is RC Gar
vie and PS Nicholson's J. Amer. Ceram. Soc., vol.55,
It was determined by the X-ray diffraction measurement method described in No. 6, 303-305 (1972). That is, the diffraction peak intensity of the monoclinic phase is Im
The diffraction peak intensities of (111), Im (11), and cubic phase are Ic
(111), assuming that the diffraction peak intensity of the tetragonal phase is It (111), The amount (% by weight) of the monoclinic phase was calculated from the equation. In addition, although It (111) is not described in the formula described in the above-mentioned paper, this is added in this measurement method.

[Examples] Next, the present invention will be described with reference to Examples.

A powder obtained by calcining zirconyl hydroxide is a zirconia raw material (purity 99.8%, average primary particle size is about several hundred Å, but according to the sedimentation method, average particle size is about 0.9 μm) Dy ₂ O ₃ powder (average particle size 1 μm, purity 99.9%) and CeO ₂ powder (average particle size) so that the content of the stabilizer in the PSZ sintered body in this raw material is as shown in Table 1. Diameter 0.7 μm,
(99.9% purity), then put this mixture in an alumina pot, crush and mix using alumina balls, and further add a binder such as paraffin wax to this raw material to granulate. It was pressure-molded to a size of 5 × 4 × 40 mm, and this compact was sintered under the firing conditions shown in Table 1.

The surface of the thus obtained sintered body was polished with a diamond grindstone to prepare a sample for characteristic evaluation.

For the evaluation of the characteristics, the amount ratio of the crystal phase and the monoclinic phase, the bending strength, the bulk specific gravity, and the amount ratio of the monoclinic phase after PCT and the bending strength were obtained as 10 average values. This bending strength is
Obtained from the three-point bending test method of JIS-R-1601, the crystal phase is based on the X-ray diffraction method, the monoclinic phase is (11) diffraction peak intensity,
The tetragonal phase was obtained from the diffraction peak intensities of (111), (004) and (400), and the cubic phase was obtained from the diffraction peak intensities of (111) and (400).

The measurement results thus obtained are as shown in Table 1, and FIG. 1 shows the ratio of the amount of the monoclinic phase to the composition of the PSZ sintered body after PCT. 30% by weight of monoclinic phase
Below, ▲ indicates 30 to 50% by weight, and ■ indicates above 50% by weight.

The region surrounded by A-B-C-D-E in FIG. 1 is shown to be within the scope of the present invention, and F-B-G-
The region surrounded by H indicates that the composition is suitable for the present invention.

In Table 1, the crystalline phase column before PCT shows the approximate quantitative ratio of crystalline phases, and c, t, and m represent cubic phase, tetragonal phase, and monoclinic phase, respectively.

As is clear from Table 1, Sample Nos. 1, 2, 5 to 14, 18 which are PSZ sintered bodies of the present invention show a large bending strength before PCT, and even after PCT, they are monoclinic. The amount ratio of phases is suppressed to 50% by weight or less, and the bending strength is 41 Kg / mm ² or more. In particular, in sample Nos. 1, 2, 6, and 7, even after PCT, the amount ratio of monoclinic phase was 23% by weight or less and 60% or less.
Bending strength of Kg / mm ² or more is obtained.

In addition, great toughness was obtained for all of these samples.

On the other hand, sample Nos. 3, 4, 15 to 17 are outside the scope of the present invention, and monoclinic phase after PCT exceeds 50% by weight and cracks occur, or less than 40 Kg / mm ^2. Only the bending strength of was obtained.

Further, Sample Nos. 18 and 19 are the cases where CeO ₂ was used alone as the stabilizer, and the occurrence of cracks was observed after sintering. Sample N
o.20,21 is the case where Dy ₂ O ₃ is used alone as a stabilizer,
PCT caused cracks and markedly deteriorated strength.

Samples Nos. 1 to 21 of this example are all made of Al ₂ O in the sintered body.
₃ contained about 0.5% by weight, and the average crystal grain size of each sintered body was about 1 μm.

〔The invention's effect〕

As described above, according to the zirconia sintered body of the present invention, it is possible to maintain high strength and high toughness with time because it has high strength and high toughness characteristics and is excellent in water resistance and heat resistance. With these, a PSZ sintered body of high quality and high reliability can be obtained. As a result, the PSZ sintered body can be applied to a wide range of applications such as tweezers, scalpels, scissors, knives, knives and other daily necessities, in-vivo members, industrial machine parts and the like.

[Brief description of drawings]

FIG. 1 is an explanatory view showing the composition of the zirconia sintered body after the hot water treatment test.

Claims (1)

[Claims] 1. Mainly consisting of ZrO ₂ and containing 0.5 to 4.5 mol%.
Dy ₂ O ₃ and 2 to 8 mol% of CeO ₂ and Dy ₂ O ₃ and
A zirconia sintered body having a total content of CeO ₂ of 6 mol% or more and a crystal phase mainly composed of a tetragonal phase or a mixed phase of a tetragonal phase and a cubic phase.