JPS59227725A - Preparation of powder of zirconium oxide having yttrium as solid solution - 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 new technology for producing zirconium oxide powder containing yttrium as a solid solution by a simple method not previously available.

Conventionally, zirconium oxide powder containing yttrium as a solid solution was
Various manufacturing methods have been proposed as materials for stabilized zirconia sintered bodies or partially stabilized zirconia sintered bodies.

In particular, stabilized zirconia sintered bodies are used as sensor materials that utilize their unique oxygen ion conductivity.
Automotive engine combustion chamber oxygen concentration regulator, or
It is incorporated into equipment such as oxygen concentration regulators in blast furnaces during steel production.
Demand has been increasing rapidly in recent years. In addition, partially stabilized zirconia sintered bodies can be made from two common ceramic materials, e.g.
It is attracting attention as a new ceramic material with high toughness that cannot be expected from sintered bodies such as alumina and magnesia, and its application to various mechanical parts is beginning to be considered. Both the stabilized zirconia sintered body and the 5-part stabilized zirconia sintered body have yttrium dissolved in the zirconium oxide crystal, so they do not undergo the phase transformation that occurs with temperature changes that occurs with ordinary zirconium oxide. In both cases, zirconium oxide powder containing yttrium as a solid solution is usually used as the raw material. Currently, there are two known industrial methods for manufacturing these sintered bodies: (1) powder mixing method and (2) coprecipitation mixing method. The powder mixing method (2) uses yttrium oxide powder and zirconium oxide powder as raw materials, mixes each in a predetermined ratio, and heats the mixed powder to a high temperature to dissolve the yttrium oxide into the zirconium oxide powder. Since this is a so-called reaction between solids, the reaction rate (-dissolution rate) is largely influenced by the contact area between the two types of rice bodies.

Therefore, in order to increase the contact area and increase the reaction rate (=dissolution rate) and increase productivity, the yttrium oxide powder and zirconium oxide powder used as raw materials are made with particle sizes as fine as practically possible. was desired. In addition, since uniformity is required for the composition of the product, the two types of raw material powders must be uniformly dispersed, and usually the two types of raw material powders are placed in a ball mill etc. at the same time and pulverized, dispersed, and mixed. After the above treatment, the general manufacturing method is to perform pressure molding if necessary to increase the degree of contact between the powders, and then heat to form a solid solution. However, even if the particle size of yttrium oxide powder and zirconium oxide powder produced on an industrial scale is small, only large secondary or tertiary agglomerated particles, which form the unit of grain, can be obtained. Yttrium oxide powder, which is usually said to be fine particles,
Even with zirconium oxide powder, the particle size is θ, /~7.0μm
That's about it. Even if these fine-particle-sized yttrium oxide and zirconium oxide powders are used as raw materials and subjected to pulverization, dispersion, and mixing operations using a ball mill, etc., each raw material powder becomes finer and finer to the size of the primary particles of each powder. cannot be expected,
Therefore, when producing zirconium oxide powder containing yttrium as a solid solution using the powder mixing method described in (2), the temperature required for solid solution must be at least 7300°C or higher, and the time required for solid solution must also be 20 to 50°C. In order to achieve complete solid solution over a long period of time, a higher temperature and a longer period of time were required.

Because the solid solution treatment is carried out at high temperatures, the resulting solid powder undergoes sintering in addition to solid solution, and tends to become highly agglomerated lumps5.Normally, the product after the solid solution must be pulverized several times. Otherwise, it could not be used as a practical raw material powder.

The coprecipitation mixing method (2) was proposed to improve the drawbacks of the powder mixing method described above. The coprecipitation mixing method uses water-bathable yttrium salts, such as yttrium chloride.

An aqueous solution of yttrium nitrate or the like and a water-soluble zirconium salt such as zirconium oxychloride or zirconium nitrate are mixed at a predetermined ratio, and yttrium and a precipitant common to zirconium, such as ammonia, are added to the mixed solution. Water is added to precipitate zirconium hydroxide and yttrium hydroxide at the same time to create a mixed hydroxide with uniform dispersion at the secondary particle level, and the mixed hydroxide is roasted to form a mixed oxide. This is a method of simultaneously performing solid solution.

This method works because the zirconium oxide powder and yttrium oxide powder are already dispersed and mixed at the primary particle level at the stage of the mixture of the precursor materials, zirconium hydroxide and yttrium hydroxide.

This method is more ideal than the powder mixing method described above. Therefore, the temperature required for solid solution is lower than that of the powder mixing method (-), and it is said that around 1,000 degrees Celsius is sufficient. However, the coprecipitated mixed hydroxide produced by this coprecipitation mixing method is It has the disadvantage that the mixture composition changes sequentially during the coprecipitation operation, that is, the process of adding the coprecipitant.This is because yttrium and zirconium cannot be precipitated as hydroxides at the same time and at the same rate. This is because subtle differences in the pH and temperature of the solution, the addition rate of the coprecipitant, and the stirring conditions of the reaction system independently affect the precipitation rate of each component. However, the composition of the mixed hydroxide co-precipitated at the beginning and the composition of the mixed hydroxide co-precipitated at the final stage may be quite different, which is causing production troubles and is not suitable for industrial use. Large-scale, batch-type coprecipitation operations are said to be difficult to manage.

In addition, the need to use coprecipitation mixed hydroxides obtained by the coprecipitation mixing method for a long time using centrifuges, filter presses, etc. is also one of the reasons for lowering the productivity of this method. .

Further, the coprecipitated mixed hydroxide described above contains a large amount of water even after being furnaced, and has the disadvantage that a large amount of heat is required for drying.

When the above-mentioned co-precipitated mixed hydroxide is dried, it becomes a highly agglomerated lump, which is heated.

The product after solid solution becomes a highly agglomerated lump, and as with the powder mixing method (2), it could not be used as a practical raw material powder unless it was pulverized.

In order to prevent the above-mentioned agglomeration, we also proposed a method in which the coprecipitated mixed hydroxide is washed with an organic solvent such as acetone or methanol, water is removed, and then dried and heated to form a solid solution. However, the operation is naturally complicated.

The present inventors have developed a method for producing zirconium oxide powder containing yttrium in solid solution (= low heating temperature required, no need for mechanical pulverization after solid solution, and the composition of the produced powder is uniform). As a result of intensive research, we decided to use gelled amorphous yttrium hydroxide as the yttrium raw material and ordinary zirconium oxide powder as the zirconia raw material.

The inventors discovered that the above objects could be achieved and completed the present invention.

That is, the present invention is a method for producing zirconium oxide powder containing yttrium as a solid solution, which is characterized by roasting zirconium oxide powder to which gelled amorphous yttrium hydroxide is attached to two surfaces.

Hereinafter, one aspect of the present invention will be described in detail.

The gel-like amorphous yttrium hydroxide used in the present invention is
Bathable inolium salts, such as yttrium chloride,
Aqueous solutions of mineral acid salts such as yttrium nitrate, organic acid salts such as yttrium acetate and yttrium formate, and alkalis,
For example, it is a translucent amorphous substance obtained by reacting an aqueous solution of ammonia, aqueous soda, aqueous potassium, etc., and has a paste-like appearance when dispersed in water.

In the reaction between an aqueous solution of yttrium salt and an aqueous alkali solution, the type of product changes by changing the temperature, concentration = pH, etc. As a method of making it, the reaction temperature is preferably adjusted to 4to℃ or less, and the yttrium concentration is preferably 0.2M as the yttrium ion concentration.
/ Adjust the pH to below, preferably ♂,! It is manufactured by maintaining the temperature above and performing one reaction.

Further, the required amount of alkali needs to be 3 equivalents or more with respect to yttrium/atom.

Of course, the gelled amorphous yttrium hydroxide used in the present invention does not have to be composed purely of gelled amorphous yttrium hydroxide, but may be partially mixed with yttrium hydroxide or a basic salt of yttrium. You can also use what you have.

The gel-like amorphous yttrium hydroxide produced by the above method exhibits a broad diffraction pattern, which is characteristic of an amorphous material, as shown in the X-ray diffraction chart in Figure 1, and a crystalline one, as shown in Figure 2. This is clearly different from the sharp diffraction pattern shown in the X-ray diffraction chart of yttrium hydroxide. Also,
Looking at the infrared absorption spectrum of gel-like amorphous yttrium hydroxide after vacuum drying at room temperature, the absorption peak due to hydroxyl groups is broad, as shown in Figure 3, and the crystalline substance shown in Figure 9 is It is clearly different from the infrared absorption spectrum of yttrium hydroxide, which has clear absorption peaks due to hydroxyl groups. Furthermore, after washing the gel-like amorphous yttrium hydroxide with water and dissolving it in acid, the components of the solution were analyzed. As a result, there was no alkali component and no acid residues of yttrium salt were present. It turns out that it is made up of water and water.

Furthermore, although the gel-like amorphous yttrium hydroxide is translucent in water, it can be centrifugally sedimented with a G value of about 5.2 oooG, and can be separated from water using a G-3 glass filter.

Judging from these facts, it is expected that it is a polymer in which many yttrium hydroxide molecules are condensed and polymerized.

This gel-like amorphous yttrium hydroxide is produced by adding zirconium oxide powder to water in which gel-like yttrium hydroxide is suspended in the same manner as ordinary organic polymers, especially poval, which has many hydroxyl groups, and stirring. When left to stand, the gel-like amorphous yttrium hydroxide that is freely dispersed in the solution disappears and adsorbs onto the surface of the zirconium oxide powder. As a result, the rising liquid of the bath liquid becomes transparent. The sedimentation volume of solids in this case is almost the same as the sedimentation volume of a slurry of only zirconium oxide powder, and of course,
It is smaller than the sedimentation volume exhibited only by gel-like amorphous yttrium hydroxide.

The method for attaching gelled amorphous yttrium hydroxide to the surface of the zirconium oxide powder of the present invention is to first prepare a predetermined amount of gelled amorphous yttrium hydroxide and mix it with the zirconium oxide powder.

After suspending zirconium oxide powder in an alkaline hydroxide solution, a predetermined amount of yttrium salt aqueous solution is added to the suspension to precipitate gel-like amorphous yttrium hydroxide, which simultaneously adheres to the surface of the zirconium oxide powder. Alternatively, zirconium oxide powder is suspended in a water bath solution of yttrium salt, and an aqueous alkali solution is added to the suspension to precipitate gel-like amorphous yttrium hydroxide. There are methods to attach it to the powder surface. In addition, the amount of gel-like amorphous yttrium hydroxide to be attached to the surface of the zirconium oxide powder may be determined based on the amount of yttrium dissolved in the zirconium oxide.
Laws may be regulated at will depending on the intended use of the product. For example, in the case of raw material powder for partially stabilized zirconia sintered bodies, gel-like amorphous yttrium hydroxide to be attached to the surface of the zirconia powder is converted to yttrium oxide, and Y2 (%/
The molar ratio of Z r Q2 is (3~,t)/(y7~9.5
’), and in the case of raw material powder for stabilized zirconia sintered bodies, the molar ratio of Y2O1/ZrO2 is
A certain proportion of the amount selected from the range of ~/2)/(octopus ~ male?) may be used.

Furthermore, it can be seen from the examples that the method of the present invention can be applied to compositions having a large molar ratio of Y2O3/ZrO2.

The gel-like amorphous yttrium hydroxide-adsorbed zirconium oxide powder is separated from the aqueous solution by a commonly used method, such as solid-liquid separation using a centrifugal filter, press filter, or the like.

The temperature at which the zirconium oxide powder with the gelled amorphous yttrium hydroxide attached to the surface of the present invention is roasted may be lower than that in the powder mixing method, and specifically, the temperature is 900 to 7300.
It should be around ℃. Further, a roasting time of θ8.2° to 1 hour is sufficient.

One possible reason for this is that the zirconium oxide powder used in the present invention, which has a structure in which 9 um (gel-like amorphous yttrium hydroxide) is attached, has a large portion of the surface of the zirconium oxide powder covered with gel-like amorphous yttrium hydroxide. This is thought to be due to the fact that the solid solution rate increases because the powder is coated in a thin layer and has a much larger contact area than the contact area between yttrium oxide and zirconium oxide powders used in conventional powder mixing methods.

In addition, the gel-like amorphous yttrium hydroxide that adhered to the surface of the zirconium oxide powder was quite firmly attached.
Even if the slurry is vigorously stirred.

It does not separate even when water is filtered or dried. Follow. Therefore, no change in composition was observed due to these operations.

What is even more surprising is that zirconium oxide powder and gel-like amorphous hydroxide are mixed in a suspended state in water, and the zirconium oxide powder with gel-like amorphous yttrium hydroxide attached to the surface is separated in a furnace! Zirconium oxide powder containing yttrium as a solid solution produced by the method of the present invention is a powder that is free from agglomeration and has fluidity when dried in a hot air dryer at θ℃~/θO℃. There is no agglomeration at the stage of completion of roasting for solid solution, and there is no need for a pulverization operation, and it can be used as it is as a raw material powder for molding materials. Moreover, its particle size distribution is almost the same as the particle size distribution of the zirconium oxide powder used as a raw material, which means that the particle size distribution of the zirconium oxide powder used as a raw material can be selected according to its intended use.

In the present invention, the zirconium oxide powder containing yttrium as a solid solution has an elementary composition of zirconium, oxygen, and yttrium, and the X-ray diffraction chart of the powder shows that yttrium is Almost no independent diffraction peaks appear.

Example/ A] Production of gel-like amorphous yttrium hydroxide.

Each of yttrium chloride, yttrium nitrate, and yttrium acetate was added to an aqueous solution yt with a concentration of 3 M/l.
A degree of ammonia water θ and 4tJ-t were added at once, and the mixture was stirred at room temperature for 30 minutes, and then the resulting gel was filtered out using an O-3 glass filter. A portion of each gel material was taken out and washed with water.

When X-ray diffraction was measured for each gel-like material, the results were as shown in the chart shown in FIG.

In addition, 7 parts of each gel-like material was washed with water and vacuum-dried at room temperature, and the infrared absorption spectra of each were measured, and the results were as shown in the chart shown in FIG. 3 for each gel-like material. In addition, after washing 7 parts of each gel with water, dissolve it in dilute sulfuric acid,
Ammonia ions, chloride ions, nitrate ions, and acetate ions in the solution were quantified by conventional methods, but none of the components were observed in each gel.

B] Adhesion of gel-like yttrium hydroxide to the surface of zirconium oxide powder.

Each of the above-mentioned gel-like substances was added to <11 water and stirred to prepare a suspension of the gel-like substances. When the suspension was left standing day and night with stirring, each gel-like substance slightly settled, and the sedimentation volume was approximately 3.61. While stirring the famous powder again, zirconium oxide powder (average particle size/μ
m, purity 99. 9.6 mol (/, /1rKq) of J″w + %) was added to the well, stirring was stopped after 70 minutes,
It was left for 2 hours. With great performances, solid matter settles to the bottom of the container,
The upper part was a clear liquid.

The sedimentation volume of solids at the bottom was 0.21 in both cases.

After the solids were separated using a G-4 glass filter, each of the water-containing cakes was dried in a hot air dryer whose temperature was adjusted to 700°C. Each cake was a powder with good fluidity and no agglomeration.

C] Roasting for solid solution.

Each of the dry powders described above was divided into 70 equal parts and processed under the following conditions.
Roasted.

A) 9θθ℃×1 hour (mouth) l x g time C) //θθ℃×/hour 2) ×2 # e) H) ×O,j #S)×/ N)×2N The composition ratio of yttrium and zirconia in each roasted product was measured by fluorescent X-ray method, and the results were as follows.

Expressed as the molar ratio of Y2O3/ZrO2 (θ, θg
, oθ/)/(o, 9t±θ, 00.:2).

In addition, when X-ray diffraction was performed on each roasted product, a single peak of yttrium oxide, which was not solidly dissolved in zirconium oxide, was measured.
, C), and 2), and were not observed in the roasted products under other conditions.

In addition, we collected a certain amount of each of the roasted products of a), 口), ＼), and 2), added a certain amount of bismuth oxide as an internal standard, and created an X-ray diffraction chart of the mixed sample. This method measures the ratio of the height of the diffraction peak of the (222) plane to the height of the diffraction peak of the (/, 2/) plane of bismuth oxide, which roughly estimates the amount of undissolved yttrium oxide present in each sample. It was measured.

The results for each sample are approximately θwL% for the sample under condition a), 20wt1% for the sample under condition a), and 72w for the sample under condition c).
In the case of condition t4-2), the male W was 1%.

In addition, the structure of each yttrium bathed zirconium oxide powder obtained is not a single monoclinic structure, which is the structure of the zirconium oxide used as a raw material, but a mixture of tetragonal, cubic, and monoclinic, and the presence of It was found that the ratio does not change depending on the gel-like amorphous yttrium hydroxide used, but changes somewhat depending on the roasting conditions. As an example, here is an X-ray diffraction chart of the product roasted under the conditions of (1) and (5). It is shown in Figure (a) and Figure J fbl.

In addition, each product obtained is a powder with good fluidity without agglomeration, and the average particle size of each powder is θ, 91 μm ~ /, /4
It was between tltrn.

Example 0.0 of co-yttrium chloride. A gelatinous material similar to Example 2 was prepared by adding -3M/l strength soda water at once to a water bath solution 411/M/l@degrees. The composition and structure of the gel-like material were measured in the same manner as in Example 1, and it was found that it was the same as the gel-like amorphous yttrium hydroxide produced in Example 2. This gel-like material was used to adhere to zirconium oxide in the same manner as in Example, followed by drying.

Roasting (temperature: 7,700° C., time: 7 hours) was performed. The obtained powder was equivalent to that produced in Example/in terms of composition, structure, and average particle size.

Example 3 The same zirconium oxide powder as used in Example 1 was added to an aqueous solution of yttrium chloride at a concentration of 9.
6 mol (/, 1 rKy) was added and stirred to make a uniform suspension. Aqueous ammonia θ, <t J-t with a concentration of 3 M/ was added at once to the suspension, stirring was continued for 3 θ minutes, and then left for 1 hour. A white solid was precipitated at the bottom of the container, and the precipitated volume was θ,/l. The upper part is a transparent liquid, and the yttrium concentration in the liquid was measured using a normal method.

Yttrium was not detected.

The resulting precipitate was filtered through a glass filter of G-4, dried and roasted in the same manner as in Example (temperature: 710°C).
The test was carried out at 0° C. for several hours.

The obtained powder was equivalent to that produced in Example/in terms of composition, structure, and average particle size.

Further, the obtained powder showed no agglomeration and had good fluidity.

Example: Aqueous ammonia with a concentration of 0.3 M/l<1.11 and 966 mol of the same zirconium oxide powder as used in Example/
/, 11Kg) and stirred, then θ, 2M/
2 tons of yttrium chloride aqueous solution with a concentration of

Stirring was stopped after 70 minutes. When the yttrium concentration in the supernatant liquid was measured after being left for 2 hours, no yttrium was detected.

After weighing the solid content obtained above, it was dried and roasted (temperature: 7,700°C, occasional heating time) in the same manner as in Example, and a powder with good fluidity without agglomeration was obtained. The composition, structure, and average particle diameter of the contact material were measured in the same manner as in Example/, and it was found to be equivalent to the product made in Example/.

Example J A gel-like amorphous ino)licum hydroxide was prepared in the same manner as in Example/, and the same zirconium oxide powder as used in Example/ was added in the same manner as in Example 1 to have the following composition ratio. Attached by method.

b) Y2O3/Zr02 (molar ratio) = 1/2 units)
=/ Otsu/l Guha) =3.2/l
♂2) =gθ/6θ
Each sample was dried in the same manner as in Example 1, and then roasted (temperature: 7100°C, time: 1 hour).

The obtained powders were free-flowing powders without agglomeration. In addition, the average particle size of each powder is /,0
It was in the range of μm to /, /\μm.

Each of the obtained powders was subjected to X-ray diffraction, and the state of solid solution of yttrium was measured in the same manner as in Example.

The results were as shown in FIG. 6, with no single peak of undissolved yttrium oxide in both a) 1 mouth) and c). The product made under the conditions of 2) contained 14% of undissolved yttrium oxide.

Comparative Example/Yttrium oxide powder with a purity of 1.5 wt% and an average particle size of θ, t μm and the same zirconium oxide powder as used in Example/ were used in a 2 molar ratio of Y2O3/Zr02-g/R. Weigh and mix so that Otsu, and ZA are /92, put them in a ball mill, and mix them. A mixed powder was made by dispersing and mixing for a while.

Each mixed powder was roasted under the following conditions.

B) No roasting) I10θ℃ x 1 hour C) / 3θO℃ x 2 hours 2) x 24 hours The product obtained under the above conditions C) and 2) has a large amount of agglomeration and is not in powder form. There were no lumps.

Further, each roasted product was subjected to X-ray diffraction, and the degree of solid solution of yttrium was measured using the same internal standard method using bismuth oxide as in Example 2, and the results were as shown in Table 7.

Also, Y2O5/Zr02= / / 92 f)1
X of the product treated under the conditions of
Two line diffraction charts are shown in Figure 7-(alib)i.

Table-/ As can be seen from the Examples and Comparative Examples, the method of the present invention:
The solid solution rate of yttrium is fast and.

No agglomeration was observed in the obtained product, and the particle size of the zirconium oxide powder used as the raw material was almost maintained.

Furthermore, examples! As can be seen from C2, in the method of the present invention, yttrium oxide is added to zirconium oxide as Y2O3/
ZrO2 (mole ratio) = 3'0/70 approximately.

It can be dissolved in solid solution very easily.

[Brief explanation of drawings]

Figure 1 is an X-ray diffraction chart of gelled amorphous yttrium hydroxide, Figure 2 is an X-ray diffraction chart of crystalline yttrium hydroxide, and Figure 3 is the red color of gelled amorphous yttrium hydroxide after vacuum drying at room temperature. External absorption spectrum, Figure 9 is the infrared absorption spectrum of crystalline yttrium hydroxide, Figure 9! Figure +
3+ is an X-ray diffraction chart of the product obtained by roasting under the conditions (B) (for a time of 2θO℃) in Example/.
X-ray diffraction chart of the product obtained by roasting at
FIG. 6 shows the conditions (A) (Y2O:l/
Zr02 (molar ratio) -179, X-ray diffraction chart of the product obtained by ri, Figure 7. Figure 7 (BL is 1 mouthful in Comparative Example 11'-)
This is an X-ray diffraction chart of a product treated under the following conditions (I10θ°C, double the weight). Patent Applicant: Asahi Kasei Industries, Ltd. Figure 1 (2e) Figure 2 (2e) Figure 3 Wave &(xlo2cm-') Figure 4 5 Skin R1 (x 10"cm-') Figure 6 30, 40 50
600 Figure 7 (0) 27 29 3+ 33 350 (b)

Claims (1)

[Claims] Surface 1: A method for producing zirconium oxide powder containing yttrium as a solid solution, characterized by roasting zirconium oxide powder to which gelatinous amorphous yttrium hydroxide is attached.