JPH013071A - High strength zirconia ceramics - 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 application field) The present invention relates to high strength zirconia ceramics.

(Prior art) 1.5 to 5 mol of a stabilizer mainly composed of iso1 to ria
% of zirconia is called partially stabilized zirconia (PSZ) ceramic, and is being developed for use as a mechanical structural material as a high-strength zirconia ceramic. However, since the above-mentioned partially stabilized zirconia ceramics do not necessarily have sufficient bending strength, Japanese Patent Laid-Open No. 60-226457 discloses a method for producing high-strength zirconia ceramics that have even higher bending strength than the above-mentioned partially stabilized zirconia ceramics. has been done.

The manufacturing method disclosed in the publication is a method of hot isostatic pressing or uniaxial pressure sintering of a mixed powder obtained by mixing raw material fine powders having a specific average primary particle size in a specific ratio. In this production method, A1□0.
An example of ceramics containing MgO and MgO is shown as an example.

In general, zirconia ceramics undergoes a phase transition from cubic to tetragonal to monoclinic as it goes from a high temperature region to a room temperature region, accompanied by a volume change.

At this time, there is a problem in that the volume change is particularly large during phase transition from tetragonal to monoclinic, and zirconia ceramics are easily destroyed due to this. As a means to deal with this problem, a known method is to dissolve a stabilizer such as Can, M+;0, Y2O3, etc. in ZrO□ to suppress the phase transition. Currently, Y2O is mainly used as a stabilizer, and partially stabilized zirconia ceramics with high strength and high toughness having a single tetragonal crystal are produced at room temperature. However, such partially stabilized zirconia ceramics are in a metastable phase and easily change over time.
When heated at a relatively low temperature of 00 to 400°C, it undergoes a phase transition to monoclinic crystal, its strength deteriorates over time, and it lacks thermal stability.

In addition, Y2O3 and A are added to ZrO□ as a zirconia ceramic intended to improve strength and thermal stability.
A mixture of 12O and
6, further Y2O3, CeO2 and A1□0
JP-A-61-77665 discloses a mixture of 3 and 3.

(Problems to be Solved by the Invention) By the way, in Japanese Patent Application Laid-Open No. 60-226457, Al2O. The disclosure only discloses the mixing of oxides and MgO, and no detailed study is made on the mixing ratio of these two oxides. Also, JP-A-58
Among the zirconia ceramics disclosed in Japanese Patent Publication No. 32066 and Japanese Patent Application Laid-open No. 61-77665, the former zirconia ceramic has high strength but insufficient thermal stability; Although it has high thermal stability, there is a problem in that it does not have sufficient strength.

The inventors of the present invention focused on the mixing ratio of these two oxides and found that the mixing ratio of these two oxides has a particularly large effect on the strength of zirconia ceramics, and that when the mixing ratio deviates from the specified range. found that the strength of partially stabilized zirconia ceramics cannot be increased. Therefore, an object of the present invention is to provide a zirconia ceramic having high strength, high acid resistance, and excellent thermal stability by specifically specifying the mixing ratio of both of these oxides.

(Means for Solving the Problems) The present invention relates to high-strength zirconia ceramics. It is characterized in that a total of 1 to 30 wt% of the system component and the magnesium component are mixed in terms of Al2O3 and MgO. When the sintered body does not contain CeO□, Y2O in the sintered body.

The content of CeO is 1.5-5mo 1%, and CeO□
, the content of Y2O3 and CeO2 is 0.5-5n+o 1% and 0.5-12+++
Within the range of o1%, the sum of both of these is 1.0 to 15
It is mol%.

In the zirconia ceramic, the sintered body is Y
It contains 1.5-5a+o1%5n+o of 2O3 or 1.5-3.5mol% of Y2O3 and 2-5mol% of CeO2, and the aluminum-based component and the magnesium-based component are A1□0 in the sintered body. ．． It is preferable that 1 to 5 wt% of MgO and MgO are mixed. Regarding the aluminum-based component and the magnesium-based component in the sintered body, the mixing molar ratio of both these components is Al2O
3 and MgO conversion (AI203/Mg0) as follows (
It is preferably within the range of a) to (c).

(a): 35-45/65-55 (b): 60-75/40-25 (C): 85-99. /'15~! The preparation of raw materials for zirconia ceramics in the present invention includes a method of mixing alumina-magnesia-based oxide powder (spinel-based powder) with zirconia powder, a method of mixing each powder of alumina and magnesia with zirconia powder, a method of mixing zirconia powder with zirconium, iso-1 -By wet mixing method using an aqueous solution containing ions such as ion, cerium, aluminum, magnesium, etc.-
) to obtain a powder, any method can be adopted. Preferably, the following two methods are used. The first method is ZrO□-Y2O3 mixed powder, Zr02-Y
A method of adding Al203-MgO mixed powder or mixed salt aqueous solution to 2O3-Ce02 mixed powder, the second method is 7r02- Y2O3-Al2O3 mixed powder, Zr02
-Y2O3-Ce02-A120. This is a method of adding MgO powder or salt aqueous solution to mixed powder. In these preparation methods, Zr02-Y2O3, Zr02-Y2O
3-Ce02, Zr02-Y2O3-Al2O32r0
2 Y20g-Ce02-A1203, Al□O, may be a mixture of each powder, or may be a mixed powder obtained by hydrolysis and calcining from a mixed salt aqueous solution, or a mixed powder obtained by calcining the mixed powder. It would be good if it was a mixed powder that can be prepared.

Although 0.5 to 3.0 wt% of hafnia (IIfO□) is unavoidably mixed in the zirconia raw material, the zirconia ceramic according to the present invention maintains the same characteristics even if a part of ZrO2 is replaced with HfO2. This shows that.

(Actions and effects of the invention) (1) When Y2O3 is used as a stabilizer (bending strength, acid resistance) Figure 1 shows that aluminum and magnesium components are converted into Al2O3 and MgO, and the mixing ratio to the whole is kept constant. The results of the mixing molar ratio between these defined substances, the bending strength of the ceramic, and the acid resistance are shown. As is clear from the results, three peaks are observed in the bending strength when the mixing molar ratio between the defined substances is gradually changed. The first peak is A1203 (mol)/Mg0(
mole) is approximately 40/60, and the second peak is approximately 70 in the same molar ratio
/30, the third peak was observed at the same molar ratio of approximately 90/10, and the increase in bending strength due to the mixture of these two components was 35-45/65-55.
It is recognized in the range of 60-75/40-25.85-99/15-1. In addition, the acid resistance increases due to the coexistence of both of these components, and particularly increases as the aluminum component increases.

On the other hand, Fig. 2 shows the mixing weight ratio of both oxides to the total and the ceramics when the aluminum and magnesium components are converted into Al2O3 and MgO and the mixing molar ratio between these defined substances is the value at the above peak. Results of bending strength and acid resistance are shown. As is clear from the results, when the weight ratio of both oxides to the total exceeds a predetermined value, there is a tendency for the bending strength to gradually decrease as the weight ratio increases, and the maximum limit is 30 wt%. It is preferably 1 to 5 wt%.

(2) When Y2O3-CeO2 is used as a stabilizer (bending strength, acid resistance, thermal stability) Figure 3 shows Y2O3 mixed in zirconia ceramics.
The relationship between fl (mol%) and bending strength is shown,
Groups A to D, which are lower than the standard value for judging strength of 70Kgf 7mm2, have ZrO□ less than 85+oo1% and a total of Y2O and CeO□ exceeding 15 mol%, and Group H has Y2O3. There is one with 7mo 1%. In addition, groups E to G or I near the reference value of intensity
” group, ZrO□ is 85 mol%, Y2O3 and CeO2 are 15 mol% in total, or Y2O3 is 5 mol%.
It is 1%. Figure 4 shows C in zirconia ceramics.
The relationship between eO□mol% and bending strength is shown, and Ce
From the viewpoint of bending strength, O2 needs to be 12 mol% or less. This also applies when the mixing ratios of Y2O3, aluminum-based components, and red sea bream/sium-based components are different.

On the other hand, Figures 5 and 6 show the aluminum component and the mago-silam component (
The relationship between the amount (wt%) of Al2O (converted to JO) and the bending strength, and the A of the same zirconia ceramics.
The relationship between the mixing molar ratio of l2O3 and MgO and the bending strength is shown. From these relationships, person 1□0. and M
The combined amount of gO must be 30 wt% or less, and the mixing molar ratio of Al2O3 and MgO is (a): 35-45/65-55 (b) = 60-75/
It is preferable that 40-25(c)=85-99/15-1. This means that z “02, Y2O
3. The same applies to cases where the mixed amounts of CeO2, Al2O3, and MgO are in other proportions.

In addition, Fig. 7 shows CeO□ in zirconia ceramics.
The relationship between the mixed imol % of the ceramic and the transition rate % from tetragonal and cubic to monoclinic after thermal deterioration of the same ceramic is shown. From this relationship, Y2O and C are important for suppressing thermal deterioration of zirconia ceramics, that is, for thermal stability.
It is clear that both eO2 play a major role, and the larger the amount of both of them mixed, the better the thermal stability is. Note that acid resistance when Y2O3-CeO2 is used as a stabilizer has also been confirmed.

In this way, Y2O3 or Y2O3-C in ZrO2
By specifying the weight ratio of the aluminum-based component and magnesium-based component to the total mixed in the sintered body containing eO2 as a stabilizer, and the molar ratio of these two components to each other, high strength and acid resistance can be achieved. This makes it possible to provide zirconia ceramics with poor thermal stability.

(Example) Original JIL - Zr02-Y2 obtained from a salt aqueous solution by a hydrolysis method
Calcinate the 03 coprecipitate at 900°C to obtain a zirconia mixed powder with a particle size of 1 μm or less. A1□03 powder and MgO powder were added to this mixed powder, pulverized and mixed in a bot mill, and spray-dried to obtain a starting material.

Using the various starting materials obtained, 200 kg/g of these were added to K1.
Preforming at a pressure of cm2, then molding using a rubber press method at a pressure of 3 tons/cm2 to form 60x 60x 8
(mn+) various square plates were obtained. These square plates were fired at 1400° C. for 5 hours using an ordinary pressure firing method, and used as samples.

J Drama 1 (1) Bending strength test: Based on the JIS-RI601.4-point bending strength test method (gf/mm"). However, the sample was 3 x 4 x 40 (mm) and the crosshead speed was 0.
5mm/win, upper span 10mm, lower span 3
0Il111゜(2) Acid resistance: test piece and 36wt%
The HCI solution was placed in a sealed container and left at 150°C for 200 hours.The weight was measured and the weight loss per unit area was calculated (+sg/cm2).

The test results for the LLL1 2 test piece are shown in Tables 1 and 2, and the test results shown in these tables are shown in FIGS. 1 and 2.

The test results for N001 to N0.27 are based on the molar ratio of the stabilizer (
Based on test pieces in which the mixing molar ratio between the sintering aids (AI□(b/Mg0) or the added amount (wt%) of the sintering aids was varied while Y2O3/ZrO2・3/97) was kept constant. It is something.

Figure 1 shows the test results for test pieces in which the amount of sintering aid added (2wt%) was kept constant and the molar ratio of the sintering aid was varied. Figure 2 shows the molar ratio between sintering aids (40/60, TO
/30.90/10) were kept constant and the amount of the sintering aid added was varied.

In addition, the straight dashed-dotted line in each figure shows the bending strength and acid resistance values of the test piece in which no sintering aid was mixed.

As is clear from these results, the acid resistance of the test piece containing the sintering aid according to the present invention is significantly improved, especially when the molar ratio of the sintering aid exceeds 30 to 60. This tendency is remarkable. On the other hand, regarding bending strength,
The mixing molar ratio between the sintering aids is approximately 40/60.70/30.
A peak was observed at 90/10, especially when the same temperature molar ratio was 35-45/65-55.60-75/40-25
．． An increase is observed in the range of 85 to 99/15 to 1. In addition, the amount of sintering aid added is 20wt%.
An increase in bending strength is observed below, preferably at 10 wt% or less.

The test results for No. 28 to No. 43 in Table 2 are the molar ratio of the stabilizer (1.5/9g, 5.2/98.5/95)
and test pieces in which the amounts of sintering aids added (2wt%, 5wt%) were kept constant and the mixing molar ratio of the sintering aids was varied, and the bending strength and acid resistance of all of these is improved compared to the test piece that does not contain the same sintering aid.

As described above, the zirconia ceramic according to the present invention is a high-strength and highly acid-resistant zirconia ceramic,
It is particularly useful as a mechanical structural material that requires high acid resistance.

In this example, as a sintering aid, ^1203 powder was used as a compound containing an aluminum component, and MgO powder was used as a compound containing a magnesium component, but the amounts of these components varied depending on the ceramic after firing. 4
The values almost match those of the aluminum-based components and magnesium-based components measured by X-ray fluorescence analysis after pulverizing to 4 μm or less. Therefore, people with aluminum-based components and magnesium-based components mixed in ceramics 1□0. , Mg
The value converted to O is Al2O3, M used as a sintering aid.
Since it almost matched the amount of gO added, the same amount was taken as the value of the mixed amount.

In addition, in the zirconia ceramic of this example,
The following impurity 5i02:2.0w was detected by fluorescent X-ray analysis.
Less than t%, T! 02: 2.0wt% or less, CaO: 0.
5 wt% or less, 20: 0.5 wt% or less, Na2O:
0.5wt% or less, '1foz: 3. It was confirmed that the content was less than Owt%.

(Example 2) Raw material 1 ZrO□-Y2O obtained from a salt aqueous solution by a hydrolysis method
3-ceo□ Co-precipitate was calcined at 900℃, and the particle size was 1 μm.
Obtain the following zirconia mixed powder. This mixed powder ^
1203 powder and MgO powder were added, chopped and mixed using a bot mill, and this was spray-dried to obtain a starting material.

■1 day Molded with.

The obtained square plate was fired at 1400° C. for 5 hours using an ordinary pressure firing method to prepare a sample.

(1) Bending strength test: Based on JIS-RI601.4-point bending strength test method (in gr/mm2). However, the sample size is 3 x 4 x 40 (mm), and the crosshead speed is 0.5.
mm/win, upper span 10mm, lower span 30
IIIIIIl.

(2) Thermal deterioration test: Based on the "Test method for ceramics" disclosed in Japanese Patent Application Laid-open No. 60-350, the sample was placed in hot water in an autoclave (hot water temperature 250°C, steam pressure inside the autoclave approximately 39 kg/c++2 ) for 50 hours, and the transition rate (%) of tetragonal and cubic crystals to monoclinic crystals in the sample is calculated by the following method.

The sample was mirror-polished with diamond paste in advance and subjected to X-ray diffraction.
From the sum of the integrated intensity of the diffraction peak of the surface (IT+IC), the tetragonal and cubic crystals ff1(VO) are calculated as Vo=(IT+IC)
)BaIM+IT+IC).

In addition, the sample after heat treatment was subjected to X-ray diffraction to calculate the tetragonal and cubic fi(V+) in the same manner as above, and these V
O, V 1 to transition rate (%) = (Vo-V+)/
V.

Calculate xlOO.

The test results for each sample are shown in Tables 3 to 11, and
Part of the results are shown in FIGS. 3 to 7.

Among these test results, the standard value for determining bending strength was set at 7.
The temperature was set at 0 Kgf/lerm2, and the criterion value (transition rate) for determining thermal stability was set at 25%.

Figure 3 shows the mixture f of Y2O3 in zirconia ceramics.
It shows the relationship between fi (mol%) and bending strength, and in the figure, eight groups from (^) to (( Groups A to D have ZrO2 of 82 to
85 n+o1%, Y2O, and those in which the combined amount of CeO2 exceeds 15 mol%, Group E and Group F are ZrO2
is 85mo 1%, the combined amount of Y2O, and CeO2 is 1511o1%, O1 is 5n+o of Y2O3
Group I% and Group H contain 7 mo I% of Y2O3, respectively. Also, in Figure 4, Y2O3 is 3n+o
I%, CeO2 mixed fi(+
++o1%) and bending strength, and the strength gradually decreases as the amount of CeO2 exceeds a predetermined value, and
When it exceeds 2 mol%, it tends to decrease rapidly. Considering the results of these two figures, in order to obtain zirconia ceramics with high bending strength, Y2O3 in ZrO□ must be 0,
5-5mol%, CeO2 0.5-12mol%
Both of these together within the range of 1.0 to 15+eo
It is necessary that Al2O3 and MgO are mixed at 1% and Al2O3 and MgO are mixed.

Figure 5 shows Y2O3 at 3m01% and CeO2 at 2moI.
%^120. in zirconia ceramics. and Mg
Mixed amount of O (wt%...The mixed amount is a value obtained by converting aluminum-based components and magnesium-based components into Al2O3 = Mho, and in this example, Al is added to each of these values.
The value of the addition amount of 2O3 and lllgo was applied. ) and bending strength, and the strength is between Al2O3 and MgO
When the amount of both mixed exceeds a predetermined value, it gradually decreases to 30w.
When it exceeds t%, it tends to decrease rapidly. Also, the 6th
The figure shows Y2O3 at 3n+o 1% and CeO2 at 2mo I
%, the mixing molar ratio of A1□03 and MgO in zirconia ceramics in which both Al2O3 and MgO are 2 wt% (
It shows the relationship between ^h(b/Mg0) and bending strength,
For strength, the mixing molar ratio is approximately 40/60.70/30.90
A peak is observed at each value of /10, and the first good range is 35-45/65-55, and the second is 60.
-75/40-25, and the third range is 85-99/15-1. Based on the results of these two figures, in order to obtain zirconia ceramics with high bending strength, Al2O3 and M
It is necessary that the mixed amount of both gO and O is 30 wt% or less, and the mixing molar ratio of both is as follows (a), (
b) , (c) (a): 35-45/65-55 (b)
=60~75740~25(c):85~99/15~
It is preferably in the range of 1.

Further, as is clear from FIGS. 3 to 5, Y2O3 is 2mo 1% and 3mol%, CeO2 is 5mo 1% or less, A1□0. Zirconia ceramics containing 1 to 5 wt% of both MgO and MgO have particularly high bending strength.

Figure 7 shows Al□0. and MgO are both 2wt% Al2O
3/CeO at a given Y2O3+oo I% in
2 shows the relationship between 1% of both and the transition rate (%) of tetragonal and cubic crystals, indicating that the larger the amount of both Y2O3 and CeO2 mixed, the lower the transition rate, that is, the better the thermal stability. It shows.

(Example 3) Example 1.2 except that the raw materials were prepared in the following manner.
Samples were prepared and tested in the same manner as in Tables 12 to 1.
The results shown in Table 5 were obtained.

"1 Random Compound 1 containing an aluminum-based component and a magnesium-based component
Of course ^+ (oH), , AlCl3, ^l (NO
3)3,^1□(C204)5,Mg(OHh,M
gCl□, Mg(NO3h, MgC204, MgC0,
These compounds were obtained by the method of Examples 1 and 2 using Zr02-Y2O3 = 7. r02- Y2O3-C
Each of the above-mentioned components in the ceramics is added to each powder of eO2.
1□0, , is added and mixed to a specific value in terms of MgO. The resulting mixture was heat-treated at 1000°C,
The mixture was ground in a bot mill, mixed, and spray-dried to obtain a starting material.

Presentation 1 As is clear from Tables 12 to 15, even if an aqueous salt solution containing an aluminum-based component and a magnesium-based component is used as a sintering aid, the results will be lower than those using ^120 powder and MgO powder. It has a similar effect.

(Example 4) Samples were prepared and tested in the same manner as in Example 1.2, except that the raw materials were prepared using the following methods (1) and (2>), and the results shown in Table 16 were obtained. Good value.

(11) A sol solution obtained by adding yttrium chloride to zirconium oxychloride and hydrolysis, or a sol solution obtained by adding yttrium chloride and cerium chloride to zirconium oxychloride and hydrolyzing A I (OH )
3 and Mg (OFlh as A1□O, , Al in terms of MgO
2O,/MgO is added so as to have a predetermined molar ratio, and 1
The powder obtained by heat treatment at 000° C. was pulverized in a pot mill and spray-dried to obtain the starting material. Table 16 No.
1~No. 6).

12+ AI (0
11) Mg was added to the resulting powder by heat treatment by adding 3 so that the molar ratio with MgO (described later) in terms of Al2O was 90/In.

Add powder and pulverize in a bot mill (Table 16 No. 7゜8), or add MgC+2 solution instead of MgO powder and pulverize it with heat treatment. Table 16 No. 9. IO) was spray dried and used as a starting material.

Left Seed 1 As is clear from Table 16, zirconium ions are used to prepare the starting materials. - Even if a mixed salt aqueous solution containing lium ions and cerium ions is used, ZrO2Y2
The same effect as when using O3, ZrO2Y2O3CeO2 coprecipitate is achieved.

(Margin below)

[Brief explanation of drawings]

FIG. 1 shows the molar ratio between the sintering aids (AI□
Figure 2 is a graph showing the relationship between the molar ratio of h/MgO), bending strength, and acid resistance. Figure 3 is a graph showing the relationship between the amount of binder mixed in, bending strength, and acid resistance. Figure 1 is a graph showing the relationship between the amount of CeO2 mixed in the same ceramic and the bending strength, and Figure 5 is a graph showing the relationship between the amount of CeO2 mixed in the same ceramic and the bending strength.
O. Figure 6 is a graph showing the relationship between the amount of mixture of both Al2O3 and MgO in the past and bending strength.
A graph showing the relationship between JO molar ratio and bending strength, Figure 7 shows the mixture of Y2O3 and CeO2 in the same ceramic.
It is a graph showing the relationship between t and the transition rate of a tetragonal product and a cubic crystal. Figure 1 M2O(A)x(b mol'/-)
AIJOj solid line ° curve solid line inflection broken line acid resistance

Claims (6)

[Claims] (1) In the ZrO_2 sintered body containing Y_2O_3 as a stabilizer in a range of 5 mol% or less, aluminum-based components and magnesium-based components are A
A total of 1 to 30 wt% in terms of l_2O_3 and MgO
High-strength zirconia ceramics characterized by being mixed. (2) The sintered body contains 1.5 to 5 mol% of Y_2O_3
The high-strength zirconia ceramic according to claim 1, which contains the high-strength zirconia ceramic according to claim 1. (3) The sintered body has an aluminum component and a magnesium component of 1 to 5 in terms of Al_2O_3 and MgO.
The high-strength zirconia ceramic according to claim 2, in which wt% is mixed. (4) 0.5-5 mol of Y_2O_3 as a stabilizer
%, CeO_2 in the range of 0.5 to 12 mol%, and in the ZrO_2 sintered body containing both of these in the range of 1.0 to 15 mol%, based on the same sintered body, aluminum-based components and magnesium-based components are Al_2O_3 and MgO. A high-strength zirconia ceramic characterized by containing a total of 1 to 30 wt% in terms of conversion. (5) The sintered body has an aluminum component and a magnesium component of 1 to 5 in terms of Al_2O_3 and MgO.
The high-strength zirconia ceramic according to claim 4, in which wt% is mixed. (6) The mixing molar ratio of aluminum-based components and magnesium-based components is Al_2O_3 and MgO equivalent (Al_2O
_3/MgO) below (a), (b), (c) (a): 35-45/65-55 (b): 60-75/
40-25(c): Claims 1 and 2 falling within the range of 85-99/15-1
The high-strength zirconia ceramic according to item 3, item 4, or item 5.