JPS62212224A - Production of zirconia solid solution crystal fine powder - Google Patents

Abstract

PURPOSE:To obtain the titled fine powder which is uniform ultrafine crystal and has improved dispersibility and compatibility, by heat-treating a hydrogen peroxide complex of a specific water-soluble zirconia and a hydrogen peroxide complex of an alkaline earth metal and/or a rare earth element. CONSTITUTION:Zr(OH)4 in a hydrous state and at least one hydroxide selected from an alkaline earth metallic element such as Ca, Mg, etc., and a rare earth element such as Y, Ce, etc., are dissolved in an aqueous solution of strong alkali and the solution is reacted with an aqueous solution of H2O2 to give (A) a hydrogen peroxide complex of water-soluble zirconium. Then, the component A and (B) a hydrogen peroxide complex of the alkaline earth metallic element and/or the rare earth element are heat-treated at 80-200 deg.C for 30min-4 hr and crystalline zirconia solid solution fine particles are precipitated.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a zirconia solid solution crystal stabilized by the addition of alkaline earth metal elements such as calcium and magnesium, and rare earth elements such as yttrium and cerium. The present invention relates to a method for producing a fine powder, and more specifically, to a method for producing the above-mentioned zirconia solid solution crystalline fine powder that has uniform ultrafine crystals and does not form secondary agglomerations.

(Prior art) As a general method for preparing zirconia-based solid solution fine powder, for example, ammonia water is added to an aqueous solution containing a water-soluble zirconium salt and an alkaline earth metal element such as magnesium or a rare earth element such as yttrium. A method of forming a precipitated hydroxide, separating it from the mother liquor, washing it, drying the amorphous precipitate by heating it in an organic solvent, and further calcining and thermally decomposing it; A method of hydrothermally treating materials at around 200°C in an alkaline region of pH 10, or zirconium and yttrium hydroxide in a hydrous state,
pH of coprecipitated hydroxide containing rare earth elements such as scandium
Make a mixed suspension in the range of 6 to 9, and heat it at about 100℃ for 10
A method is known in which the soluble amorphous portion is dissolved and separated using a strong acid after heat treatment for several days.

(Problems to be Solved by the Invention) However, in the first conventional method, since the precipitate obtained from the coprecipitation method is essentially amorphous, there is a significant The second method has the disadvantage of causing secondary agglomeration, and the second method requires the use of a pressure vessel, resulting in high equipment costs, impossibility of continuous operation, and the risk of high pressure. The third method has disadvantages of long manufacturing time and poor yield.

(Means for Solving the Problems) An object of the present invention is to provide a method for producing a zirconia-based solid solution crystalline fine powder that eliminates the above-mentioned disadvantages. Water-soluble zirconium hydroxide formed by reacting hydrogen peroxide with at least one of the hydroxides of alkaline earth metal elements such as calcium and magnesium, and rare earth elements such as yttrium and cerium in a strong alkali. It is characterized in that a hydrogen oxide complex and a hydrogen peroxide complex of an alkaline earth metal element and/or a rare earth element are heat-treated at 80 to 200°C to precipitate crystalline zirconia solid solution fine particles.

Zirconium hydroxide in a water-containing state can be obtained by preparing an aqueous solution of a water-soluble zirconium salt such as nitrate, hydrochloride, or acetate of zirconium, and then adding alkali such as aqueous ammonia or sodium hydroxide to the solution to precipitate it. However, it is optional, such as making a slurry of commercially available zirconium hydroxide. However, when using the above salts, in order to maintain the high purity of the zirconia solid solution crystalline fine powder, it is desirable to thoroughly wash the precipitated hydroxide and remove as much anions as possible. .

As the hydroxide of an alkaline earth metal such as calcium or magnesium, generally used is a commercially available salt, hydroxide, or oxide of an alkaline earth metal ion dissolved in an aqueous solution.

Hydroxides of rare earth elements such as yttrium and cerium are
An aqueous solution of a hydrochloride or nitrate of a rare earth element, or an aqueous solution in which an oxide of a rare earth element is directly dissolved in an acid, is precipitated by adding alkali such as aqueous ammonia or sodium hydroxide.

The hydroxide is used after being sufficiently washed with water.

Zirconium ions and alkaline earth metal elements and/or
Or the concentration of rare earth element mixed hydrogen peroxide complex is 0.1~
It is preferably about 1.0 mol/L. 0.1
If it is less than mol/1, it is undesirable from the viewpoint of production efficiency, and if it exceeds 1.0 mol/A, the precipitated zirconia solid solution fine particles tend to aggregate.

In order to completely dissolve zirconium and the hydroxide of an alkaline earth metal element and/or rare earth element in a short time, it is preferable that the amount of hydrogen peroxide added is equal to or less than the equivalent molar ratio of the hydroxide.

As strong alkaline agents, aqueous ammonia, strong basic organic compounds, potassium hydroxide, etc. are used, but the pH value at which hydrogen peroxide complexes of soluble zirconium and rare earth elements begin to form is A base that can easily reach a pH of less than 13 is desirable, and since heat treatment is performed to precipitate the zirconia-based solid solution fine particles, it is desirable that the base is not a base that causes a decrease in pH due to an increase in the temperature of the reaction solution. The higher the concentration of strong alkali, the more crystalline and high-quality solid solution particles will be produced. Another advantage is that when the alkali concentration increases, the molar boiling point increases and heating to 100° C. or higher becomes possible at normal pressure, and the higher the treatment temperature, the better the crystallinity of the precipitated particles.

The reason why the heat treatment temperature of the hydrogen peroxide complex was set to 80 to 200°C is that if the temperature is less than 80°C, the precipitation rate is too slow to obtain monodisperse fine particles with a narrow particle size distribution, and the production time is too long. This is because if the temperature exceeds .degree. C., it is necessary to add a large amount of alkaline agent or use a pressure vessel, which is not economical. Therefore, from the viewpoint of manufacturing time and economy,
The heat treatment temperature is particularly preferably about 80 to 150°C, and about 30°C
A yield of approximately 100 tsp is deposited in a production time of minutes to 4 hours.

(Example) Next, examples of the method for producing the zirconia-based solid solution crystalline fine powder of the present invention will be described together with comparative examples thereof. Note that both the Examples and Comparative Examples contain Y2O6*3. It was assumed that zirconia-based solid solution fine powder of Owt% was produced.

Example 1 First, zirconium oxychloride (first rare element #) 0.
1 mol of ZrO2 and 0.003 mol of 3.0 mol % yttrium chloride (Shin-Etsu Chemical 'A) in terms of Y2O3 was dissolved in 200-mL pure water.

Next, add ammonia water (special grade reagent 3 Q) to the obtained aqueous solution.
wt%) to form a coprecipitated hydroxide precipitate, and the P solution was sufficiently washed with pure water until it no longer became cloudy due to the dropping of silver nitrate. 2.0 mol/t of the precipitate washed with
After dispersing it in a 200-ml aqueous solution of sodium hydroxide,
Approximately 20 mol/L hydrogen peroxide solution (special grade reagent 28
wt) 100- and stirred well. The pH of this solution was 13.6. Next, the obtained slurry preparation liquid was held at 90° C. for 2 hours to obtain a cloudy white precipitated product. After thoroughly washing and filtering this product with pure water, it was dispersed in water whose pH was adjusted to 10 with aqueous ammonia.
3 moly't of sodium oleate (500) was added and further dispersed. Since this dispersion has the property of agglomerating when the pH is lower than 4, the pH is lowered to lower than 4 with an organic acid, and after decanting the supernatant g, the above pH value is adjusted again.
IQKy4 conditioned water was added and redispersed. This work 8
This was repeated 4 to 5 times to sufficiently remove residual sodium ions.

Next, the resulting washed product was dissolved and removed with alcohol to remove the oleic acid, and the resulting cake was dried in an oven at 100°C for 5 hours, and then calcined at 700°C for 2 hours. This calcined powder 12 is mixed with a phosphate ester dispersant (product name: r).
Bnphos P8-1211J was added to alcohol 50- to which an appropriate amount was added, and a dispersion treatment was performed for 30 minutes using an ultrasonic cleaner. As a result of observing this dispersion state using a transmission electron microscope, it was found that the primary particles were ultrafine crystal particles of about 300A.

Comparative Example 1 Using the same reagent as in Example 1, Q, 5 mol/
Aqueous solution of zirconium oxychloride g, 200- and 0, 1
5 mol/L yttrium chloride in water g, 20-
were mixed to obtain a mixed solution. This mixed solution was gradually added dropwise with aqueous ammonia into a reaction tank designed to maintain the p)IIQ at all times to obtain a co-precipitated hydroxide of zirconium and yttrium. The obtained hydroxide was washed with pure water until the solution F was no longer cloudy due to dropwise addition of silver nitrate.

After dispersing the washed hydroxide f2t in the octatool, it was heated in an oil bath until most of the water in the dispersion evaporated and the heating was stopped at 140°C, when the temperature of the dispersion started to rise rapidly. , remove the dehydrated precipitate from the dispersion by filtration,
After drying in the oven at 200℃ for 3 hours, 850℃
It was calcined at ℃ for 2 hours.

The drawing is a heating loss characteristic diagram of the dried products obtained in Example 1 and Comparative Example 1, in which people indicate the heating loss curve of Example 1, B indicates the heating loss curve of Comparative Example 1, and the weight loss curve in the figure From the results of differential thermal analysis (not shown), it was confirmed that the material of Example-1 was crystalline.

Next, 1 portion of each dried product obtained in Example 1 and Comparative Example 1 was added.
, the tetragonal crystal ratio of the powder fired at 100℃ for 2 hours is powder X
1@diffraction and the impurity content was measured by emission analysis and shown in Table 1.

Furthermore, these calcined products are molded by hot press, and 1
A sample for bending strength was obtained by sintering at 400°C for 1 hour. The bending strength of this sample was measured according to the method of J18-I'L-1603 and is shown in the table. The samples were heated and placed in water at room temperature to measure their thermal shock resistance, and the temperature at which they broke was shown in the table.

As is clear from the table, Example 1 is better than Comparative Example 1.
It was confirmed that the tetragonal crystal ratio, bending strength, and thermal shock resistance were excellent, and the content of impurities was also low.

(Effects of the Invention) As described above, according to the method for producing a zirconia-based solid solution crystalline fine powder of the present invention, a water-soluble hydrogen peroxide complex of zirconium ions and alkaline earth metal element ions and/or rare earth element ions is formed. This is due to the homogeneous nucleation reaction of crystalline particles, in which fine grains of crystalline solid solution are precipitated directly without passing through amorphous hydroxide by desorption again. It has the advantage that crystalline fine powder consisting of primary particles can be produced in a short time and with a high yield.

In addition, the zirconia-based solid solution crystalline fine powder obtained by the present invention consists essentially of primary particles that are close to monodisperse,
Since it has excellent dispersibility and mixability, it is particularly useful as a raw material powder for dispersion-strengthened ceramics and dispersion-strengthened alloys. Furthermore, since the zirconia-based solid solution crystalline fine powder obtained by the present invention has excellent compositional uniformity, the bending strength and thermal shock strength of the sintered body are higher than those of the sintered body made of raw material powder obtained by the conventional method. Therefore, it is also useful as a reinforced zirconia solid electrolyte used in applications where usage conditions such as vibration are severe, such as oxygen sensors for automobiles or steel manufacturing, and as a raw material powder for cutting tools such as knives.

[Brief explanation of drawings]

The drawing is a heating loss characteristic diagram of dried products obtained in Examples and Comparative Examples of the present invention. 2 people outside

Claims (1)

[Claims] Zirconium hydroxide in a hydrated state and at least one of the hydroxides of alkaline earth metal elements such as calcium and magnesium and rare earth elements such as yttrium and cerium.
A water-soluble zirconium hydrogen peroxide complex formed by reacting hydrogen peroxide with hydrogen peroxide in a strong alkali, and an alkaline earth metal element and/or rare earth element hydrogen peroxide complex at 80 to 200°C. A method for producing a zirconia-based solid solution crystalline fine powder, which comprises precipitating crystalline zirconia-based solid solution fine particles through heat treatment.