JPS60246261A - 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 The present invention relates to a zirconia-based sintered body having excellent thermal durability and high mechanical strength.

A zirconia sintered body consisting mainly of a tetragonal crystal phase (hereinafter referred to as 0θ-psz) to which OeO is added as a stabilizer.
(abbreviated as sintered compact) exhibits high strength and fracture toughness. However, this sintered body contains tetragonal particles, which is a thermodynamically unstable crystal phase at room temperature. Therefore,
When kept in a low humidity environment below 500°C for a long time, the tetragonal grains gradually transform into a stable monoclinic phase, and cracks occur in the sintered body due to the volume expansion associated with this transition. A so-called thermal aging phenomenon occurs. Therefore,
By eliminating these drawbacks, the uses of sintered bodies can be greatly expanded, and sintered bodies for this purpose are being sought.

In the Y,0)-Zr02-based sintered body, methods for suppressing this thermal aging deterioration include reducing the grain size of the tetragonal grains and increasing the amount of YvOs, which is a stabilizer. It has been known.

Such a method can also be applied to 0s-PSE sintered bodies.

That is, by reducing the particle size of the 0s-PSZ sintered body and increasing the content to 00,
A relatively stable sintered body with little thermal deterioration over time can be obtained.

The present inventors have conducted research on zirconia-based sintered bodies that do not cause such thermal aging deterioration and methods for suppressing thermal aging deterioration, and have found that thermal aging deterioration is only due to the size of the sintered body particles and the amount of stabilizer. The second component coexists in the sintered body, rather than depending on it.
It was found that it significantly depends on the presence of phase. That is, in addition to the first phase of 0e-PSZ, by making alumina, an alumina-based double oxide, a zirconia-based double oxide containing La, N (1, etc.) exist as a second phase, the conventional 0o-I It has been discovered that the present invention can be guaranteed even more thermal durability than the 'sz sintered body, and the present invention has been completed.

The sintered body of the present invention has not only high thermal durability but also high mechanical strength.

That is, the present invention uses a stabilizer mainly composed of OeQ.
Zr0.60 to 99% by weight containing ~50 mol% and A~
1 to 40% by weight of an oxide consisting of at least one of the following: MgO-based oxide, A-he-81-based oxide, and a double oxide of La, Pr, Nd, or Pm and Zr. The present invention provides a zirconia-based sintered body consisting of the following.

The present invention will be explained in more detail below.

The stabilizer mainly composed of OeQ used in the present invention means that OeO1 is the main component as a stabilizer, and in addition to this, MgO, Oak, Y, 01 and O
s.

Examples include oxides of lanthanum-based rare earth elements other than Pr, Nd, and Pm, but there is no harm in using a small amount of these.

The amount of the stabilizer is 5 to 30 mol% based on zirconia.
must be within the range. Within this range, zirconia is preferably composed mainly of tetragonal crystals or a mixed phase of tetragonal crystals and cubic crystals. However, there is no problem even if monoclinic crystals coexist in an amount of 30% by weight or less. If it is less than 5 mol % or more than 30 mol %, it is not preferable because tetragonal zirconia will not be produced or sufficient mechanical strength will not be obtained.

The oxides coexisting in the sintered body of the present invention are alumina-based or zirconia-based oxides, and the ratio of these is 1 to 4.
It is 0% by weight. If it exceeds 40% by weight, the strengthening mechanism based on the tetragonal zirconia is reduced, resulting in a decrease in strength, which is not preferable.

Moreover, if it is less than 1% by weight, thermal durability will not be sufficient.

For alumina-based oxides, A\IA1
ﾆ-MgO-based oxides or ＾-81-based oxides are mentioned, and Alzom MgO-based oxides have a spinel-type crystal phase, and ﾆ-1910. The mullite type crystal phase is the main component of the system oxide. On the other hand, in the zirconia system, La, Pr,
Examples include a double oxide of N(l or Pm and Zr), which mainly has a pyrochlore cubic crystal phase.

Furthermore, it is preferable that the average grain size of the crystals of the sintered body of the present invention is 5 μm or less. If it exceeds 5 μm, the strength decreases significantly due to crystal grain growth, which is not preferable.

The above-mentioned sintered body with excellent thermal durability is a sintered body with 20%
After aging for 1000 hours in an air environment with a temperature of 0 to 300°C and a partial pressure of water vapor of 4 to 20 degrees Hg, the monoclinic crystals on the surface of the sintered body account for 50% by weight or less of the total, and the bending strength value This means that the sintered body does not show a decrease of more than 20% of its value before aging.

Hereinafter, the method for manufacturing a sintered body of the present invention will be explained.

OeO! For ZRO containing a stabilizer mainly composed of Zr, there is a method of mixing the powder with the stabilizing oxide powder and Zr.

Any method may be used, including a method of obtaining a powder by a wet synthesis method using an aqueous solution containing a stabilizing agent element and Zr.

The methods of adding oxides to coexist are AI, O, and powder.

For Altol-wgo oxides, spinel powder, Alt
He-81 He-based oxides are mixed with zirconia powder as mullite powder, alumina, and magnesia.

A method of adding and mixing a predetermined amount of each powder of silica to zirconia powder, or zirconium or aluminum.

Any method of obtaining powder by wet synthesis using an aqueous solution containing ions such as magnesium and silicon can be applied.

For a double oxide consisting of La, Pr, Na, or Pm and Zr, it is of course possible to add and mix it as a pyrochlore type oxide powder, but if the lanthanum-based rare earth metal oxide is mixed with zirconia, During the crystallization process, a spontaneous reaction between these oxides and zirconia occurs, forming a pyrochlore-type cubic compound. It is also a good method to obtain a powder from a solution containing zirconium and the above-mentioned lanthanum-based rare earth metal by a wet synthesis method.

The sintered body of the present invention can be obtained by molding the powder containing each of these components by a rubber press method or the like and then firing it at a temperature of 1400 to 1650°C.

As explained above, the sintered body of the present invention is resistant to thermal aging deterioration, that is, has good thermal durability. The relationship between the average particle diameter of sintered body crystals and the amount of stabilizer is shown in FIG.

In the sintered body consisting only of oa-psz, the region marked ■ to the right of the dotted line a was the composition range showing thermal durability, but La! It can be seen that in the example in which ZrO containing 01 and 2 mol% of NdtOs was added, the range of thermal durability was significantly expanded to the shaded area (2) surrounded by the solid line (2) and the dotted line (a). Furthermore, it is a sintered body that does not deteriorate over a longer period of time than conventional sintered bodies.

In this way, the sintered body of the present invention has not only mechanical strength but also
Due to its excellent thermal durability, dice,
It is suitable not only for use in nozzles, grinding, media, bearings, etc., but also for a wide range of applications, such as in areas subject to heat, such as engine parts.

EXAMPLES Hereinafter, the present invention will be further explained with reference to Examples, but the present invention is not limited thereto.

Example 1 A solution containing a predetermined amount of zirconium oxychloride, cerium chloride, and lanthanum chloride or neodymium chloride was mixed with pH=9.
Aqueous ammonia was added to obtain a precipitate. This precipitate was separated by mouth, dried, and then fired at a temperature of 950° C. for 2 hours to obtain a fine raw material powder for a sintered body. Also, for comparison, 0@hemorrhoids and ZrO.

A powder consisting of

The obtained powder was made into a molded body by a rubber press method, and 1
A sintered body was obtained by firing at a temperature of 400 to 1650°C for 2 hours.

The bending strength of the sintered body was measured according to the method specified in J Engineering 8 R1601-1981. In addition, the thermal deterioration test due to aging was performed by placing the sintered body in an electric furnace at a temperature of 200°C.
The bending strength was measured after holding for 1000 hours while circulating air with a dew point of 20°C.

The results obtained are shown in Table 1.

Example 2 A predetermined amount of high-purity alumina powder was added to 0e-PSZ powder with an average primary particle size of 30 OA, wet-mixed and pulverized in a ball mill, and the resulting powder was molded by a rubber press method. A sintered body was produced by sintering at a temperature of 1650° C. for 2 hours. The presence or absence of thermal deterioration of this sintered body was determined according to the method described in Example 1. The results are shown in Table 2.

Also, instead of alumina powder, the average particle size is α2μ
The same sintered body preparation and thermal deterioration test as above were performed using AltO, -MgO-based oxide (spinel powder) or human-1tos-8101-based oxide (mullite powder), and the results are shown in Table 2. I got it.

358-

[Brief explanation of the drawing]

FIG. 1 shows the range in which the Oa-P SZ sintered body and the sintered body of the present invention exhibit their respective effects regarding thermal durability. ■... Effective range of 0-psz sintered body ■... Effective range expanded by the sintered body of the present invention 1...0θ-PEI
Boundary line of effect of Z sintered body)...Boundary line of effect of sintered body of the present invention Patent applicant Toyo Soda Kogyo Co., Ltd. District 1 (': (I02 content (thousands) (嗟)

Claims (3)

[Claims] (1) 60 to 99% by weight of ZrO containing 5 to 60 mol% of a stabilizer mainly composed of 0eC4 and 1 to 99% of the following A component
A zirconia-based sintered body characterized by comprising 40% by weight. A component: All0I, AI4os-MgO-based oxide, shoulder^-8iO,-based oxide, and La, Pr, N
d or an oxide consisting of at least one kind of double oxide of Pm and Zr (2) Claim (1) in which the zirconia sintered body in the sintered body mainly consists of tetragonal crystals or tetragonal crystals and cubic crystals
The zirconia-based sintered body described in . (3) The zirconia-based sintered body according to claim (1) or (2), wherein the average particle diameter of crystals in the sintered body is 5 μm or less.