JP2007015898A - Method for manufacturing zirconium oxide powder and zirconium oxide powder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a zirconium oxide powder being excellent in formability, sinterability and characteristics of a sintered compact and to provide the zirconium oxide powder. <P>SOLUTION: The method for manufacturing the zirconium oxide powder involves a step to obtain a zirconium compound aqueous solution by dissolving a water-soluble zirconium compound in water, a neutralization step to form zirconium hydroxide by adding an alkali to the zirconium compound aqueous solution, a washing step to wash the resultant zirconium hydroxide and a step to obtain a zirconium oxide powder by pulverizing zirconium oxide after drying and calcining the washed zirconium hydroxide, and is characterized in that in the washing step, a carboxylic acid solution, an ammonia solution or a carboxylic acid ammonium salt solution is used as a washing liquid. The zirconium oxide powder manufactured by the method is also provided. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing zirconium oxide powder and zirconium oxide powder.

  Zirconium oxide is widely used as an evaporation material tablet, structural ceramics, a solid electrolyte fuel cell member, a raw material for electronic ceramics, and the like. Such zirconium oxide is granulated after being mixed with other raw materials if necessary. This granulated zirconium oxide powder is generally led to a final product through the steps of molding, sintering and finishing. The properties of the final product are governed by the microstructure of the sintered body, and it is important to remove defects such as voids and cracks of the sintered body that may occur in the sintering process. Since most of the defects in the sintering process are caused by defects formed in the molding process and abnormal grain growth due to impurities, prevention of structural defects and high purity in the molding process are important.

For example, Patent Document 1 and Patent Document 2 are extraneous by reducing the electrical conductivity when the zirconium oxide powder is slurried (500 μS / cm or less in Patent Document 1 and 300 μS / cm or less in Patent Document 2). A method has been proposed in which ions are removed to make the powder in the slurry weakly agglomerated to produce a granulated powder excellent in formability and sintered body characteristics. In Patent Document 3, after hydrolyzing a zirconium salt aqueous solution, the pH is adjusted to 11 or more with an alkaline aqueous solution such as sodium hydroxide or potassium hydroxide to obtain a hydrated zirconia slurry, and then water in a solid-liquid separation step. We have proposed a method for producing zirconium oxide powder with excellent formability and sintered body characteristics by removing most of the anions in the zirconia slurry and then drying and calcining.
JP 2001-89145 A JP2003-192452 JP-A-6-171942

However, in Patent Document 1, there is a tendency that impurities originally contained in the raw material and ions added in the process of producing zirconium oxide cannot be completely removed by washing with water. The production method of Patent Document 2 requires a high-purity raw material and is not economically advantageous, and it is difficult to completely remove ions added in the process of producing zirconium oxide with water. In addition, in the production method of Patent Document 3, although anions are reduced, cations that induce liquid phase sintering such as Na ⁺ and K ⁺ are not completely removed by washing with hot water in the solid-liquid separation process. There is a tendency. These residual ions induce liquid phase sintering and non-uniform sintering, and as a result, cause segregation, warpage, and distortion, so that it is difficult to obtain a uniform sintered body.

  Accordingly, the present invention provides a method for producing a zirconium oxide powder that gives a sintered body with less ion elution during granulation and excellent moldability, sinterability and sintered body characteristics, and such zirconium oxide powder. With the goal.

  The present invention includes a step of dissolving a water-soluble zirconium compound in water to obtain an aqueous zirconium compound solution, a neutralizing step of adding an alkali to the aqueous zirconium compound solution to form zirconium hydroxide, and washing the zirconium hydroxide. In the method for producing a zirconium oxide powder comprising a washing step and a step of drying and calcining the zirconium hydroxide after washing to obtain zirconium oxide and then pulverizing to obtain a zirconium oxide powder, Provided is a method for producing a zirconium oxide powder, characterized by using an acid solution, an ammonia solution, or a carboxylic acid ammonium salt solution.

  Further, according to the present invention, when the zirconium oxide powder is produced by the production method of the present invention and made into a 15 wt% slurry with pure water, it exhibits an electric conductivity of 50 μS / cm or less, and ranges from 5 to 7 Zirconium oxide powder exhibiting a pH value of is provided.

  Furthermore, according to the present invention, the oxidation oxide characterized in that it is a zirconium oxide powder produced by the production method of the present invention, and exhibits a pH value in the range of 5 to 7 when made into a 15 wt% slurry with pure water. Zirconium powder is provided.

  According to the present invention, a zirconium oxide powder excellent in formability, sinterability, and sintered body characteristics can be obtained. Since the zirconium oxide powder according to the present invention has little ion elution during granulation, it contributes to a reduction in the product defect rate after sintering.

  Hereinafter, the present invention will be described in more detail.

  The method for producing a zirconium oxide powder according to the present invention comprises a step of preparing an aqueous zirconium compound solution, a neutralizing step of adding an alkali to the aqueous zirconium compound solution to produce zirconium hydroxide, a washing step of washing the zirconium hydroxide, The process includes a step of drying and pre-calcining the zirconium hydroxide after washing to obtain zirconium oxide and then pulverizing to obtain zirconium oxide powder.

As a main method for producing zirconium oxide (ZrO ₂ ), there are a hydrolysis method and a neutralization precipitation method. The basic process is already known, and any method can be applied to the present invention through zirconium hydroxide.

As the water-soluble zirconium compound as a starting material, those capable of generating zirconium hydroxide by neutralization with an alkali can be widely used. Among these, zirconium oxychloride is relatively inexpensive and rarely causes problems in the use of wastewater, so that it can be suitably used as the starting material of the present invention. Hereinafter, basic zirconium sulfate (Zr (OH) _(4-2x) (SO ₄ ) _x · nH ₂ O (where 0 <x <2), which is general as a neutralization precipitation method using zirconium oxychloride as a starting material) ) Will be described in detail. In the present specification, “zirconium hydroxide” refers to what is referred to as hydrated zirconia, crystalline hydrated zirconia, amorphous hydrated zirconia, and the like.

First, zirconium oxychloride is dissolved in water to prepare an aqueous solution thereof. The concentration of the zirconium oxychloride aqueous solution is about 10 to about 500 g / liter in terms of ZrO ₂ in consideration of the production efficiency and the slurry viscosity of basic zirconium sulfate produced in the next step, preferably about the converted value. A range of 20 to about 250 g / liter is desirable.

  Next, a substance containing sulfate ions is added to the zirconium oxychloride aqueous solution. The substance containing sulfate ions may be either solid or liquid, and is not particularly limited as long as the sulfate ions are stably present in the aqueous solution. Typically, sulfuric acid, ammonium sulfate, sodium sulfate, potassium sulfate, or the like can be used.

  These sulfate ion-containing materials can be added to the zirconium oxychloride aqueous solution in the form of an aqueous solution. The amount of sulfate ion-containing material added is sufficient to produce basic zirconium sulfate. Specifically, it is desirable that the amount of sulfate ions be 0.3 mol or more, preferably 0.4 mol or more, per 1 mol of zirconium. In addition, it is more preferable to avoid making the addition amount of a sulfate ion containing substance stoichiometrically excessive from an economical viewpoint.

  Thus, the zirconium zirconium oxychloride aqueous solution to which the sulfate ion-containing substance is added is heated to produce basic zirconium sulfate. The heating temperature is preferably 50 ° C. or higher. This is because when the temperature is lower than 50 ° C., the production rate of basic zirconium sulfate is small, which is industrially disadvantageous. The basic zirconium sulfate is generated sufficiently quickly if it is heated to 50 ° C. or higher in the presence of zirconium ions and sulfate ions, and there is no particular limitation on the heating means. Also, appropriate measures such as mixing after heating each of the zirconium oxychloride solution and the sulfate ion-containing substance solution can be employed.

  Next, a zirconium hydroxide slurry can be obtained by adding an alkali in the neutralization step. Basic zirconium sulfate has a pH of 7 or higher, and most of its sulfate ions are substituted to form zirconium hydroxide. Therefore, the neutralization operation may be carried out so that the pH is 7 or higher. As the alkali, alkalis commonly used in industry, such as sodium hydroxide, potassium hydroxide, aqueous ammonia, etc. can be used. In order to completely replace the sulfate ion with the hydroxyl group ion by neutralization, it is preferable to perform agitation operations commonly performed in industry, such as agitation with a stirring blade and circulation with a pump.

In the present invention, zirconium oxide can contain a rare earth element as a stabilizer. By adding these rare earth elements, a crystal of zirconium oxide, which is normally monoclinic at room temperature, can be made into a stable crystal structure in which a large number of tetragonal crystals are present. Such a rare earth element may be carried out by adding an appropriate compound containing a rare earth such as cerium chloride in the form of an aqueous solution before, during or after the neutralization step. it can. The rare earth element here refers to a lanthanoid element excluding scandium, yttrium, and promethium. The addition amount of these rare earth compounds is preferably determined according to the use of zirconium oxide. In general, the content is preferably 5 to 50% by weight of zirconium converted to ZrO ₂ . If the addition amount of the rare earth compound is 5% by weight or less, the tetragonal crystal of zirconium oxide is not stabilized, and the ratio of monoclinic crystals present at room temperature tends to be high, and the strength tends not to be high. If it is 50% by weight or more, the tetragonal crystal of zirconium oxide is completely stabilized, stress-induced transformation at room temperature hardly occurs, and there is a tendency that the strength is not increased.

  In addition, when it is necessary to reduce especially transition metals, such as iron and nickel, in a zirconium oxide powder, it is preferable to filter a basic zirconium sulfate precipitation before neutralization. By this operation, the precipitate and the mother liquor are separated so that most of the transition metal ions remain in the mother liquor, and the basic zirconium sulfate can be made to have a low content of these transition metal elements. The basic zirconium sulfate which has been filtered and separated is dispersed again in water and subjected to the above neutralization operation.

  Zirconium hydroxide is produced by the above neutralization operation, followed by filtration and washing with water to obtain a zirconium hydroxide cake from which most of the impurities such as sulfate ions and chloride ions have been removed. For filtration and washing, a filter press, a centrifuge, etc., which are usually used industrially can be used. It is desirable to repeat the filtration and washing until the impurity ions become 3 mol% or less with respect to zirconium.

Next, a carboxylic acid solution, an ammonia solution, or a carboxylic acid ammonium salt solution composed only of elements represented by the element symbols H, C, N, and O is used to remove contaminating ions still remaining after washing. In the same manner as the previous washing step, filtration and washing are performed. A carboxylic acid solution and an ammonia solution can be used in combination. As the carboxylic acid represented by the general formula R—COOH, formic acid, acetic acid, oxalic acid and the like can be used. Moreover, ammonium formate, ammonium acetate, etc. can be used as ammonium carboxylate. Carboxylic acid solution, the concentration of the ammonia solution or ammonium carboxylate salt solution, is may be determined by taking into consideration the concentration of contaminating ions, be 0.05 to 30 mol% with respect to zirconium in terms of ZrO ₂ preferable. If the concentration is 0.05 mol% or less, the contaminated ions tend not to be sufficiently removed. Moreover, it is unpreferable from an economical viewpoint that a density | concentration is 30 mol% or more.

The following effects can be obtained by washing zirconium hydroxide using a carboxylic acid solution, an ammonia solution, or a carboxylic acid ammonium salt solution. That is, the carboxyl ion R—COO ⁻ ion contained in the carboxylic acid solution or the ammonium carboxylate salt solution replaces the anion in the impurity ions, while the ammonium ion NH ⁴⁺ contained in the ammonia solution or the ammonium carboxylate salt solution. Replaces the cations in the contaminating ions. The mechanism by which the carboxyl ions and ammonium ions replace impurities such as Na ⁺ , K ⁺ , Cl ⁻ and SO ₄ ²⁻ is not clear, but is presumed to be due to the following reasons.

  Compared to strong acid and strong alkali ions such as hydrochloric acid, sulfuric acid, sodium hydroxide, potassium hydroxide and their salts, which are the source of contaminating ions, weak acid and weak alkali ions such as carboxylic acid, ammonia and their salts are more High affinity for zirconium hydroxide surface. Therefore, substitution of strong acid and strong alkali ion proceeds by such weak acid and weak alkali ions.

  Subsequently, the zirconium hydroxide obtained in this way is dried, and the adhering water is dehydrated. This drying can be performed by maintaining the temperature at 60 to 200 ° C. using an external combustion type or internal combustion type drying apparatus that is usually used industrially, but at a higher temperature in the subsequent calcination step. There is no particular upper temperature limit.

  Thereafter, the obtained zirconium hydroxide is calcined to obtain zirconium oxide. The calcination temperature can be appropriately selected according to the intended use of the zirconium oxide to be obtained. However, in order to decompose and remove carboxyl ions and ammonium ions substituted with impurity ions, the temperature is preferably set to 400 ° C. or higher. . In addition, since the zirconium oxide rapidly grows into coarse particles at a temperature exceeding 1300 ° C., the upper limit is preferably set to 1300 ° C.

  Next, the zirconium oxide obtained by calcining is pulverized as necessary to adjust the particle size. For pulverization, a stamp mill, a roller mill, a jet mill, a medium mill, a vibration mill, a ball mill, and the like that are usually used in industry can be used.

  The zirconium oxide powder obtained as described above exhibits an electric conductivity of 50 μS / cm or less and a pH in the range of 5 to 7 when made into a 15 wt% slurry with pure water. Such zirconium oxide powder is excellent in moldability, sinterability and sintering characteristics, and has little ion elution during granulation, which contributes to a reduction in the defective product rate after sintering.

  EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited to these.

“Electrical conductivity” refers to a 15 wt% zirconium oxide slurry obtained by adding 30 g of zirconium oxide powder to 170 g of pure water having an electric conductivity of 0.3 μS / cm and stirring and dispersing for 5 minutes with a stirrer unless otherwise specified. The electrical conductivity is measured with a conductivity meter SC-51 (manufactured by Yokogawa Electric Corporation). “PH” refers to a value obtained by measuring a 15 wt% slurry prepared in the same manner as in the case of measuring electric conductivity with a commercially available pH meter. The “average particle diameter” refers to a particle diameter D ₅₀ corresponding to 50% of the integrated volume measured using a particle size distribution measuring apparatus (SALD2000A manufactured by Shimadzu Corporation, refractive index 2.4 to 0.1i) by a laser diffraction method. . “Specific surface area” refers to a value calculated by the BET 1-point method using a pore distribution measuring device (manufactured by Yuasa Ionics, NOVA1000). “Sintered density” refers to the density measured by the Archimedes method. “Roundness” refers to a value obtained by a least square center method (LSC) using a roundness measuring device (RA-116D manufactured by Mitutoyo Corporation).

Example 1
2 liters of a zirconium oxychloride aqueous solution having a ZrO ₂ conversion concentration of 50 g / liter was prepared. To this solution was added 0.50 mol% of ammonium sulfate with respect to ZrO _2, the solution was heated to 95 ° C. with stirring to obtain a basic zirconium sulfate slurry. After cooling this slurry to 60 ° C., basic zirconium sulfate was separated from the mother liquor with Nutsche. The obtained basic zirconium sulfate solid content was dispersed in water and then neutralized by adding ammonia water to obtain a slurry containing zirconium hydroxide. Filtration and washing of the resulting slurry was repeated 3 times to obtain a zirconium hydroxide cake. The zirconium hydroxide cake was dispersed in a mixed solution of 1 liter of a 2 g / liter formic acid solution and 1 liter of a 0.5 g / liter ammonia solution with a stirrer, and then filtered to give a slurry. The zirconium hydroxide cake was dried at 120 ° C. to obtain zirconium hydroxide powder. This zirconium hydroxide powder was calcined at 800 ° C. in an external heating furnace and then pulverized with a jet mill to obtain zirconium oxide powder. The obtained zirconium oxide powder had an average particle size of 1.3 μm and a BET of 23 m ² / g. Further, when the zirconium oxide was used as a slurry with pure water and the electrical conductivity and pH were measured, the electrical conductivity was 1.37 μS / cm and the pH was 6.4.

Example 2
2 liters of a zirconium oxychloride aqueous solution having a ZrO ₂ conversion concentration of 50 g / liter was prepared. To this solution was added 0.50 mol% of ammonium sulfate with respect to ZrO _2, the solution was heated to 95 ° C. with stirring to obtain a basic zirconium sulfate slurry. After cooling this slurry to 60 ° C., basic zirconium sulfate was separated from the mother liquor with Nutsche. The obtained basic zirconium sulfate solid content was dispersed in water and then neutralized by adding ammonia water to obtain a slurry containing zirconium hydroxide. Filtration and washing of the resulting slurry was repeated 3 times to obtain a zirconium hydroxide cake. The zirconium hydroxide cake was dispersed in 2 liters of a 3 g / liter ammonium formate solution with a stirrer to form a slurry, filtered through Nutsche, and the resulting zirconium hydroxide cake was dried at 120 ° C. to obtain zirconium hydroxide powder. did. The zirconium hydroxide powder was calcined at 1200 ° C. in an external heating furnace and then pulverized with a jet mill to obtain zirconium oxide powder. The obtained zirconium oxide powder had an average particle size of 1.8 μm and a BET of 1.2 m ² / g. Furthermore, when the electrical conductivity and pH were measured using this zirconium oxide as a slurry with pure water, the electrical conductivity was 2.7 μS / cm and the pH was 6.2.

Example 3
2 liters of a zirconium oxychloride aqueous solution having a ZrO ₂ conversion concentration of 50 g / liter was prepared. To this solution was added 0.50 mol% of ammonium sulfate with respect to ZrO _2, the solution was heated to 95 ° C. with stirring to obtain a basic zirconium sulfate slurry. The slurry was cooled to 60 ° C. and then neutralized by adding ammonia water to obtain a slurry containing zirconium hydroxide. Filtration-washing of the obtained slurry was repeated twice to obtain a zirconium hydroxide cake. The zirconium hydroxide cake is dispersed in a mixed solution of 1 liter of a 5 g / liter formic acid solution and 1 liter of a 1 g / liter ammonia solution with a stirrer, and the slurry is filtered with a Nutsche. The cake was dried at 120 ° C. to obtain zirconium hydroxide powder. This zirconium hydroxide powder was calcined at 800 ° C. in an external heating furnace and then pulverized with a jet mill to obtain zirconium oxide powder. The obtained zirconium oxide powder had an average particle size of 1.4 μm and a BET of 21 m ² / g. Furthermore, when the product zirconium oxide was slurried with pure water and the electrical conductivity and pH were measured, the electrical conductivity was 8.8 μS / cm and the pH was 6.4.

Example 4
2 liters of a zirconium oxychloride aqueous solution having a ZrO ₂ conversion concentration of 60 g / liter was prepared. After adding 0.60% mol of ammonium sulfate to this solution with respect to ZrO ₂ , the solution was heated to 95 ° C. with stirring to obtain a basic zirconium sulfate slurry. The slurry was cooled to 60 ° C. and then neutralized by adding ammonia water to obtain a slurry containing zirconium hydroxide. The obtained slurry was filtered and cleaned once to obtain a zirconium hydroxide cake. The zirconium hydroxide cake was dispersed in a mixed solution of 1 liter of a 10 g / liter formic acid solution and 1 liter of a 5 g / liter ammonia solution with a stirrer, and this was filtered to give a slurry. The zirconium oxide cake was dried at 120 ° C. to obtain zirconium hydroxide powder. This zirconium hydroxide powder was calcined at 800 ° C. in an external heating furnace and then pulverized with a jet mill to obtain zirconium oxide powder. The obtained zirconium oxide powder had an average particle size of 3.8 μm and a BET of 11 m ² / g. Furthermore, when the product zirconium oxide was slurried with pure water and the electrical conductivity and pH were measured, the electrical conductivity was 9.8 μS / cm and the pH was 6.5.

Example 5
2 liters of a zirconium oxychloride aqueous solution having a ZrO ₂ conversion concentration of 60 g / liter was prepared. After adding 0.60% mol of ammonium sulfate to this solution with respect to ZrO ₂ , the solution was heated to 95 ° C. with stirring to obtain a basic zirconium sulfate slurry. The slurry was cooled to 60 ° C. and neutralized by adding caustic soda (NaOH) to obtain a slurry containing zirconium hydroxide. The obtained slurry was filtered and washed twice to obtain a zirconium hydroxide cake. A mixture of 1 liter of a 5 g / liter oxalic acid solution and 1 liter of a 3 g / liter ammonia solution was dispersed with a stirrer to make a slurry, and then filtered with a Nutsche. The cake was dried at 120 ° C. to obtain zirconium hydroxide powder. The obtained zirconium hydroxide powder was calcined at 800 ° C. in an external heating furnace and then pulverized with a jet mill to obtain zirconium oxide powder. The obtained zirconium oxide powder had an average particle size of 4.0 μm and BET of 10 m ² / g. Furthermore, when the product zirconium oxide was slurried with pure water and the electrical conductivity and pH were measured, the electrical conductivity was 7.7 μS / cm and the pH was 6.4.

Example 6
2 liters of a zirconium oxychloride aqueous solution having a ZrO ₂ conversion concentration of 120 g / liter was prepared. After adding 0.70 mol% of sulfuric acid to this solution with respect to ZrO ₂ , the solution was heated to 95 ° C. with stirring to obtain a basic zirconium sulfate slurry. The slurry was cooled to 60 ° C. and then neutralized by adding caustic soda to obtain a slurry containing zirconium hydroxide. Filtration and washing of the resulting slurry was repeated 3 times to obtain a zirconium hydroxide cake. A mixture of 1 liter of a 2 g / liter acetic acid solution and 1 liter of an ammonia solution of 1.5 g / liter was mixed with the above zirconium hydroxide with a stirrer to form a slurry, which was then filtered through a Nutsche. The zirconium hydroxide cake was dried at 120 ° C. to obtain zirconium hydroxide powder. This zirconium hydroxide powder was calcined at 800 ° C. in an external heating furnace and then pulverized with a jet mill to obtain a product zirconium oxide powder. The obtained zirconium oxide powder had an average particle size of 16 μm and a BET of 7 m ² / g. Furthermore, when the product zirconium oxide was slurried with pure water and the electrical conductivity and pH were measured, the electrical conductivity was 2.7 μS / cm and the pH was 6.3.

Example 7
2 liters of a zirconium oxychloride aqueous solution having a ZrO ₂ conversion concentration of 30 g / liter was prepared. After adding 0.60 mol% of ammonium sulfate to this solution with respect to ZrO ₂ , the solution was heated to 95 ° C. with stirring to obtain a basic zirconium sulfate slurry. The pH of this slurry was 1 or less. After adding an aqueous solution containing 0.05 mol of yttrium chloride (YCl ₃ ) to this slurry, the solution was cooled to 60 ° C. and neutralized by adding caustic soda to obtain a slurry containing zirconium hydroxide. Filtration and washing of the resulting slurry was repeated 3 times to obtain a zirconium hydroxide cake. The above zirconium hydroxide cake was dispersed in a mixed solution of 1 liter of 0.5 g / liter formic acid solution and 1 liter of 0.1 g / liter ammonia solution with a stirrer, and then filtered with Nutsche. The obtained zirconium hydroxide cake was dried at 120 ° C. to obtain zirconium hydroxide powder. This zirconium hydroxide was calcined at 800 ° C. in an external heating furnace and then pulverized with a jet mill to obtain zirconium oxide powder. The obtained zirconium oxide powder had an average particle size of 0.7 μm and a BET of 38 m ² / g. Further, when the product zirconium oxide was slurried with pure water and the electrical conductivity and pH were measured, the electrical conductivity was 0.8 μS / cm and the pH was 6.2.

Comparative Example 1
2 liters of a zirconium oxychloride aqueous solution having a ZrO ₂ conversion concentration of 50 g / liter was prepared. To this solution was added 0.50 mol% of ammonium sulfate with respect to ZrO _2, the solution was heated to 95 ° C. with stirring, to obtain a basic zirconium sulfate slurry. After cooling this slurry to 60 ° C., basic zirconium sulfate was separated from the mother liquor with Nutsche. The obtained basic zirconium sulfate solid content was dispersed in water and then neutralized by adding ammonia water to obtain a slurry containing zirconium hydroxide. Filtration and washing of the resulting slurry was repeated 4 times to obtain a zirconium hydroxide cake. This zirconium hydroxide cake was dried at 120 ° C. to obtain zirconium hydroxide powder. The obtained zirconium hydroxide powder was calcined at 800 ° C. in an external heating furnace and then pulverized by a jet mill to obtain zirconium oxide powder. The obtained zirconium oxide powder had an average particle size of 1.3 μm and a BET of 24 m ² / g. Further, when the zirconium oxide was slurried with pure water and the electrical conductivity and pH were measured, the electrical conductivity was 58 μS / cm and the pH was 4.5.

Comparative Example 2
2 liters of a zirconium oxychloride aqueous solution having a ZrO ₂ conversion concentration of 50 g / liter was prepared. After 0.50% mol of ammonium sulfate was added to this solution with respect to ZrO ₂ , the solution was heated to 95 ° C. with stirring to obtain a basic zirconium sulfate slurry. The slurry was cooled to 60 ° C. and then neutralized by adding ammonia water to obtain a slurry containing zirconium hydroxide. Filtration and washing of the resulting slurry was repeated 4 times to obtain a zirconium hydroxide cake. This zirconium hydroxide cake was dried at 120 ° C. to obtain zirconium hydroxide powder. The obtained zirconium hydroxide powder was calcined at 800 ° C. in an external heating furnace and then pulverized with a jet mill to obtain zirconium oxide powder. The obtained zirconium oxide powder had an average particle size of 1.4 μm and a BET of 21 m ² / g. Furthermore, when the electric conductivity and pH were measured using this zirconium oxide as a slurry with pure water, the electric conductivity was 64 μS / cm and the pH was 4.3.

Comparative Example 3
2 liters of a zirconium oxychloride aqueous solution having a ZrO ₂ conversion concentration of 60 g / liter was prepared. After adding 0.60% mol of ammonium sulfate to this solution with respect to ZrO ₂ , the solution was heated to 95 ° C. with stirring to obtain a basic zirconium sulfate slurry. The slurry was cooled to 60 ° C. and then neutralized by adding caustic soda to obtain a slurry containing zirconium hydroxide. Filtration and washing of the resulting slurry was repeated 3 times to obtain a zirconium hydroxide cake. This zirconium hydroxide cake was dried at 120 ° C. to obtain zirconium hydroxide powder. The obtained zirconium hydroxide powder was calcined at 800 ° C. in an external heating furnace and then pulverized with a jet mill to obtain zirconium oxide powder. The obtained zirconium oxide powder had an average particle size of 4.0 μm and BET of 10 m ² / g. Furthermore, when the electrical conductivity and pH were measured using this zirconium oxide as a slurry with pure water, the electrical conductivity was 138 μS / cm and the pH was 7.6.

Comparative Example 4
2 liters of a zirconium oxychloride aqueous solution having a ZrO ₂ conversion concentration of 120 g / liter was prepared. After adding 0.70 mol% of sulfuric acid to this solution with respect to ZrO ₂ , the solution was heated to 95 ° C. with stirring to obtain a basic zirconium sulfate slurry. The slurry was cooled to 60 ° C. and then neutralized by adding caustic soda to obtain a slurry containing zirconium hydroxide. The obtained slurry was filtered and washed three times to obtain a zirconium hydroxide cake. This zirconium hydroxide cake was dried at 120 ° C. to obtain zirconium hydroxide powder. The obtained zirconium hydroxide powder was calcined at 800 ° C. in an external heating furnace and then pulverized with a jet mill to obtain a product zirconium oxide powder. The obtained zirconium oxide powder had an average particle size of 15 μm and a BET of 7 m ² / g. Furthermore, when the product zirconium oxide was slurried with pure water and the electrical conductivity and pH were measured, the electrical conductivity was 258 μS / cm and the pH was 7.8.

Zirconium oxide powders obtained in the examples and comparative examples, to which no rare earth was added in the production process, were added with 5 mol% of yttria powder with respect to zirconium oxide, and then made into 15 wt% slurry with pure water. After spray drying, uniaxial molding was performed using a circular mold having a diameter of 20 mm at a pressure of 1000 kgf / cm ² . After forming, the sintered body was obtained by firing at 1500 ° C. for 3 hours. The density of the obtained sintered body was measured by the Archimedes method. Furthermore, after setting the thickness to 3 mm with a surface grinder, the least square center method (LSC) was used using a roundness measuring device RA-116D manufactured by Mitutoyo Co., Ltd. ) To measure the roundness. The average results of 50 samples are shown in Table 1.

Claims (12)

  A step of dissolving a water-soluble zirconium compound in water to obtain a zirconium compound aqueous solution, a neutralization step of adding an alkali to the zirconium compound aqueous solution to produce zirconium hydroxide, a washing step of washing the zirconium hydroxide, In the method for producing zirconium oxide powder, comprising the step of drying and calcining the zirconium hydroxide after washing to obtain zirconium oxide and then pulverizing to obtain the zirconium oxide powder. In the washing step, in the washing step, carboxylic acid solution, ammonia A method for producing zirconium oxide powder, characterized by using a solution or a carboxylic acid ammonium salt solution.   The method according to claim 1, wherein the carboxylic acid solution and the ammonia solution are used in combination. _3. The concentration of the carboxylic acid solution, ammonia solution, or carboxylic acid ammonium salt solution is in the range of 0.05 to 30 mol% with respect to zirconium in terms of ZrO _2. Manufacturing method.   The said water-soluble zirconium compound is a zirconium oxychloride, The manufacturing method as described in any one of Claims 1-3 characterized by the above-mentioned.   The method for producing a zirconium oxide powder according to any one of claims 1 to 4, wherein a water-soluble rare earth compound is added before, during or after the neutralization step. .   6. The production method according to claim 5, wherein the rare earth is selected from lanthanoid elements excluding scandium, yttrium, and promethium. The method according to claim 5 or 6, characterized in that the addition in a proportion of 5 to 50 wt% with respect to zirconium in terms of the rare earth compound in ZrO _2.   The said calcining is performed at the temperature of 400-1300 degreeC, The manufacturing method as described in any one of Claims 1-7 characterized by the above-mentioned.   The method according to any one of claims 1 to 8, wherein the zirconium oxide powder exhibits an electric conductivity of 50 µS / cm or less when made into a 15 wt% slurry with pure water.   The manufacturing method according to any one of claims 1 to 9, wherein the zirconium oxide powder exhibits a pH value in a range of 5 to 7 when a 15 wt% slurry is formed with pure water.   A zirconium oxide powder produced by the method according to any one of claims 1 to 10 and having an electrical conductivity of 50 µS / cm or less when made into a 15 wt% slurry with pure water.   Zirconium oxide produced by the method according to any one of claims 1 to 10, wherein when it is made into a 15 wt% slurry with pure water, it exhibits a pH value in the range of 5-7. Zirconium oxide powder.