JP2005029440A - Zirconium hydroxide and zirconium oxide having low alpha-ray emission rate and method of manufacturing them - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of economically manufacturing zirconium hydroxide and zirconium oxide obtained by calcining the zirconium hydroxide which are suitable for a raw material of glass for a solid-state image sensing device package such as a charge-coupled device (CCD) and filler for a semiconductor resin package and have low α-ray emission rate. <P>SOLUTION: A step for preparing a zirconium oxychloride solution, a step for producing basic zirconium sulfate by adding a sulfate ion into the resultant zirconium oxychloride solution in a quantity enough to produce basic zirconium sulfate (Zr(OH)<SB>4-2X</SB>SO<SB>X</SB>) and heating, a step for separating the resultant basic zirconium sulfate from the mother liquor while keeping the mother liquor to pH ≤7, a step for producing zirconium hydroxide by adding an alkali into the resultant basic zirconium sulfate and a step for separating and cleaning the resultant zirconium hydroxide are successively carried out. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention relates to zirconium hydroxide which is inexpensive and has a low α-ray emission rate of 0.5α / cm ² h or less, a zirconium oxide powder obtained by heating this, and a method for producing the same. In particular, the present invention has a low α-ray emission rate such as a glass material for a solid-state image sensor package such as a CCD, a raw material for electronic ceramics such as a filler for a semiconductor resin package, a piezoelectric element, a capacitor, a raw material for a vapor deposition material, The present invention relates to zirconium hydroxide that is required to be obtained, zirconium oxide obtained by calcining the same, and a method for producing them.

  Zirconium oxide has (1) no absorption band in the visible light region, (2) high refractive index of about 2.1, (3) high melting point, (4) partially stabilized with yttria, etc. has high toughness (5) A completely stabilized material has excellent properties such as a solid electrolyte, and is widely used in various industrial fields. However, it is well known that generally manufactured zirconium oxide is mixed with uranium and thorium from raw ores and becomes a source of alpha rays, and is a field where low alpha ray emission rate is required, for example, a solid-state imaging device such as a CCD. Its use has been limited in materials for packaging glass, fillers in semiconductor resin packages, and the like (for example, Patent Documents 1 and 2).

In such a field, in order to suppress the α-ray emission rate to a low level, a method of obtaining zirconium oxide by heating after dissolving zirconium metal with an electron beam (Patent Document 3) and zirconium oxychloride as a raw material are reused. A method of crystallizing (Patent Document 4) has been adopted.
Japanese Patent Application Laid-Open No. 6-121539 JP 2001-185710 A JP-A-9-137269 Japanese Patent Laid-Open No. 9-156955

  However, the heat treatment method after melting metal zirconium with an electron beam can reduce the α-ray emission rate, but the production equipment is expensive and the energy required for production is enormous. There is a problem that mass production is difficult. On the other hand, the method of recrystallizing zirconium oxychloride requires the use of a highly corrosion-resistant device in order to go through the steps of concentration and recrystallization of a high-concentration hydrochloric acid solution, and the hydrochloric acid generated in the manufacturing process. There are problems such as requiring environmental protection measures against steam and increasing product costs.

  The present invention relates to a raw material for glass for a solid-state image sensor package such as a CCD, zirconium hydroxide having a low α-ray emission rate suitable for a filler of a resin package for semiconductors, zirconium oxide obtained by calcining the same, and economically producing them. A manufacturing method is proposed.

In the zirconium hydroxide of the present invention, the contents of uranium and thorium are each limited to 0.2 mass ppm or less, and the α-ray surface emission rate when formed into a molded body is 0.5 α / cm ² h or less. _Yes , such a zirconium hydroxide is prepared in the stage of preparing a zirconium oxychloride solution. In the obtained zirconium oxychloride solution, sulfate ions are _converted into basic zirconium sulfate (Zr (OH) _(4-2X) (SO ₄ ) _X · nH _2. Adding a sufficient amount to produce O) and heating to form basic zirconium sulfate, separating the produced basic zirconium sulfate from the mother liquor while maintaining the pH of the mother liquor at 7 or less, and A step of adding an alkali to the basic zirconium sulfate to produce zirconium hydroxide, and separating and washing the produced zirconium hydroxide Phase, can be produced by sequentially performing.

  In the above zirconium hydroxide production process, a stabilizer-forming agent can be added before adding alkali to basic zirconium sulfate or after adding alkali to basic zirconium sulfate to form zirconium hydroxide. Thus, zirconium hydroxide having the above characteristics and containing a stabilizer can be produced.

Moreover, by calcining the zirconium hydroxide obtained as described above, the content of uranium and thorium is limited to 0.2 mass ppm or less, respectively, and the α-ray surface emission rate when formed into a molded body is 0. Zirconium oxide powder having a thickness of 5α · cm ² h or less can be produced.

In the above, the molded product refers to a product obtained by uniaxially molding zirconium hydroxide or zirconium oxide with a mold to obtain a density of 2 to 4 Mg / m ³ .

Zirconium hydroxide and zirconium oxide according to the present invention have a low content of radioactive elements such as uranium and thorium, and the α-ray surface emission rate of the molded product is 0.5α / cm ² h or less. When used as a raw material for glass for device packages, fillers for resin packages for semiconductors, etc., the occurrence of α-ray interference is extremely low. Further, according to the production method of the present invention, zirconium hydroxide and zirconium oxide having the above characteristics can be produced very economically.

In the zirconium hydroxide of the present invention, the content of uranium and thorium is limited to 0.2 mass ppm or less, respectively, and the α-ray surface emission rate when formed into a molded body is 0.5 α / cm ² h or less. is there. In order to produce such zirconium hydroxide, first, zirconium oxychloride (ZrOCl ₂ · 8H ₂ O) is used as a starting material, and sulfate ions are added to the aqueous solution to obtain basic zirconium sulfate (Zr (OH) _{(4 -2X)} (SO ₄ ) _X · nH ₂ O), where (0 <X <2) precipitate is formed, and then alkali is added to the obtained basic sulfuric acid precipitate to obtain zirconium hydroxide. In this case, when separating the basic zirconium sulfate from the mother liquor, by maintaining the pH at 7 or less of the mother liquor, uranium and thorium are transferred to the mother liquor in the form of, for example, uranyl ions, and thus the basic sulfuric acid is used. Zirconium (Zr (OH) _(4-2X) (SO ₄ ) _X · nH ₂ O), where the step of separating from the precipitate of 0 <X <2 is taken. This will be specifically described below.

First, an aqueous solution of zirconium oxychloride (ZrOCl ₂ · 8H ₂ O) as a starting material is prepared. Its concentration is calculated as Zr0 _2, production efficiency, and basic zirconium sulphate produced in the next step _{(Zr (OH) (4-2X)} (SO 4) X · nH 2 O), provided that 0 <X < In consideration of the slurry viscosity of 2, the range is from about 10 to about 500 g / l (liter), preferably from 20 to 250 g / l (liter) in terms of the converted value.

  A substance containing sulfate ions is added to the zirconium oxychloride aqueous solution having the above concentration. 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 and the like can be used. In particular, sulfuric acid and ammonium sulfate produce favorable results because the subsequent washing step can be performed in a short time.

These sulfate ion-containing substances are added to an aqueous solution of zirconium oxychloride in the form of an aqueous solution, and the amount added is basic zirconium sulfate (Zr (OH) _(4-2X) (SO ₄ ) _X · nH ₂ O), However, the amount may be sufficient to generate (0 <X <2). Specifically, it may be 0.3 mol or more, preferably 0.4 mol or more as sulfate ions with respect to 1 mol of zirconium. In addition, it is preferable to avoid making the addition amount of a sulfate ion-containing substance stoichiometrically excessive from an economical viewpoint.

  Thus, the aqueous solution of zirconium oxychloride to which the sulfate ion-containing substance is added is heated to produce basic zirconium sulfate. Heating is preferably 50 ° C. or higher. This is because when the heating is less than 50 ° C., the production rate of basic zirconium sulfate is small, which is industrially disadvantageous. 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. Zirconium oxychloride solution, sulfate ion-containing substance Appropriate means such as mixing after heating each solution can be taken.

  In the above reaction process, the bulk density of zirconium oxide finally obtained can be changed by adjusting the degree of stirring of the mixed solution. For example, if strong stirring is performed by a method generally performed on an industrial scale, the bulk density of the finally obtained zirconium oxide can be reduced, whereas if the stirring is not performed, the bulk density is reduced. Get higher. Therefore, the degree of stirring can be selected according to the required characteristics of zirconium oxide, and the zirconium oxide can be made separately.

The basic zirconium sulfate precipitate obtained is separated from the mother liquor by filtration. At this time, it is necessary to filter while maintaining the pH of the mother liquor at 7 or less, and as a result, most of uranium and thorium, which are the sources of α-ray emission, remain in the mother liquor, and basic zirconium sulfate is removed from these radiation sources. The content can be low. The reason why basic zirconium sulfate and uranium and thorium-containing salts can be separated in this manner is that, on the acidic side, UO ₂ is oxidized to produce water-soluble ions such as uranyl ions (UO ₂ ²⁺ ) and escape to the mother liquor. Presumed. On the other hand, on the alkali side, precipitates with low solubility such as (NH ₄ ) ₂ .U ₂ O ₇ .3H ₂ O are formed and remain in the basic zirconium sulfate.

  This filtration can be performed using industrially used equipment such as a filter press and a centrifuge, but the residual ratio of uranium and thorium in the filtered basic zirconium sulfate is attached to the precipitate. Since it is determined by the ratio a / v of the mother liquor total amount v with respect to the remaining mother liquor amount a, for example, if v = 6000 l and a = 100 to 200 l, the residual ratio of uranium and thorium is 1/30 in one mother liquor separation. It will be about 1/60.

  By repeating such filtration while maintaining the pH at 7 or more, the residual amounts of uranium and thorium can be drastically reduced. For example, by repeating the process of filtering the basic zirconium sulfate cake obtained by filtration in a mineral acid such as sulfuric acid and hydrochloric acid and then filtering again, the residual radioactive elements such as uranium can be kept below the target value. Can be reduced.

  The basic zirconium sulfate cake obtained by the above filtration is dispersed again in water, and a zirconium hydroxide slurry can be obtained by performing a neutralization operation in which an alkali is added thereto. Since basic zirconium sulfate has a pH of 7 or higher and sulfate ions are substituted to form zirconium hydroxide, neutralization may be carried out so that the pH is 7 or higher. As the alkali, alkalis usually used industrially, for example, sodium hydroxide, potassium hydroxide, aqueous ammonia and the like can be widely used. In order to completely replace the sulfate ion with the hydroxyl group ion by neutralization, it is preferable to perform agitation operations usually performed industrially, such as agitation with a stirring blade and circulation with a pump.

  In this case, in order to contain a stabilizer such as yttria, a compound that forms an appropriate stabilizer containing yttrium, for example, yttrium chloride, is added in the form of an aqueous solution before or after the neutralization step. Can do.

  Zirconium hydroxide is formed by the above neutralization operation, and then filtered and washed to obtain a zirconium hydroxide cake from which impurities such as sulfate ions and chloride ions are removed. For filtration and washing, a filter press, a centrifuge, etc., which are usually used industrially can be used. Although it is desirable to continue the filtration and washing until contaminant ions become 3 mol% or less with respect to zirconium, for example, it is not always necessary to remove sulfate ions and chloride ions by subsequent calcination. .

  Zirconium hydroxide obtained in this manner can be dried and subjected to dehydration of adhering water to obtain a zirconium hydroxide product. This drying can be carried out by maintaining the temperature at about 60 ° C. to 200 ° C. using an external combustion type or internal combustion type drying apparatus which is usually used industrially.

  The obtained zirconium hydroxide can be further calcined to give zirconium oxide. The under temperature can be appropriately selected according to the use of the product, but in practice it is preferably 400 to 1400 ° C. or less.

  The zirconium oxide obtained by calcination is pulverized as necessary to adjust the particle size. For pulverization, those that can be adjusted to a desired particle size such as a stamp mill, a roller mill, a jet mill, a media mill, a vibration mill, and a ball mill, which are usually used industrially, can be used.

  Through the above series of operations, zirconium hydroxide such as uranium and thorium can be obtained with very little zirconium hydroxide such as uranium and thorium. In that case, stabilizers, such as a yttria, a ceria, magnesia, a calcia, can be contained. As means for containing these stabilizers, known means can be used. For example, prior to the neutralization operation, an element chloride or the like forming these stabilizers is added, or As disclosed in Japanese Patent No. -293564, various means such as calcining after adding yttrium chloride to a zirconium hydroxide slurry and adsorbing it can be used.

(Example 1)
A basic zirconium sulfate slurry was obtained by heating a solution obtained by adding 0.50 mol of ammonium sulfate to zirconium oxide in 2 l of a ZrO2 converted concentration of 50 g / l to 95 ° C. while stirring. The pH of the slurry was 1 or less. The obtained slurry was cooled to 60 ° C. and filtered with a Nutsche to separate basic zirconium sulfate from the mother liquor.

  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 obtained zirconium hydroxide cake was dried at 120 ° C. and crushed to obtain a zirconium hydroxide product. This was uniaxially molded with a mold to obtain a molded body having a density of ³ Mg / m ³ , the α-ray surface emission rate was measured with a ZnS scintillation detector, and the α-ray surface emission rate of the molded body: 0.07 ± 0.05 α / A result of cm ² h was obtained. Further, the contents of uranium and thorium were chemically analyzed by ICP mass spectrometry, and the results of uranium: 0.1 ppm or less and thorium: 0.1 ppm or less were obtained.

(Example 2)
Zirconium hydroxide obtained in Example 1 was calcined at 800 ° C. in an external heating furnace to obtain zirconium oxide. As a result of measuring the characteristic value as a molded body in the same manner as in Example 1, α-rays of the molded body were obtained. Surface release rate: 0.07 ± 0.04α / cm ² h, uranium: 0.1 ppm or less, thorium: 0.1 ppm or less.

(Example 3)
A basic zirconium sulfate slurry was obtained by heating a solution obtained by adding 0.50 mol of ammonium sulfate to zirconium oxide in 2 l of a ZrO ₂ converted concentration of 50 g / l to 95 ° C. while stirring. The pH of the slurry was 1 or less. After cooling the obtained slurry to 60 ° C., basic zirconium sulfate was separated from the mother liquor with Nutsche, and then washed twice with 1N hydrochloric acid to obtain basic zirconium sulfate.

The obtained basic zirconium sulfate was dispersed in water and then neutralized by adding aqueous ammonia to obtain zirconium hydroxide. Filtration-washing of the resulting slurry was repeated 3 times to obtain a zirconium hydroxide cake. The obtained zirconium hydroxide cake was dried at 120 ° C. and crushed to obtain a zirconium hydroxide product. The characteristic values were measured in the same manner as in Example 1. As a result, the α-ray surface emission rate of the molded product was 0.01 ± 0.02α · cm ² h, uranium: 0.1 ppm or less, thorium: 0.1 ppm or less.

(Example 4)
The zirconium hydroxide obtained in Example 3 was calcined at 800 ° C. in an external heating furnace to obtain zirconium oxide, and the characteristic values were measured in the same manner as in Example 1. As a result, the α-ray surface emission rate of the molded body : 0.01 ± 0.02α / cm ² h, uranium: 0.1 ppm or less, thorium: 0.1 ppm or less.

(Example 5)
A solution obtained by adding 0.60 mol of ammonium sulfate to zirconium oxide in 600 l of an aqueous zirconium oxychloride solution having a concentration of 60 g / l in terms of ZrO ₂ was heated to 95 ° C. with stirring to obtain a basic zirconium sulfate slurry. The pH of the slurry was 1 or less.

After cooling the obtained slurry to 60 ° C., basic zirconium sulfate was separated from the mother liquor with a filter press, and the solid content was neutralized with ammonia water to obtain zirconium hydroxide. The obtained zirconium hydroxide was dispersed in water, and filtration and washing were repeated three times to obtain a zirconium hydroxide cake, which was dried at 120 ° C. and crushed to obtain a zirconium hydroxide product. The product characteristic values were α-ray surface emission rate of the molded product: 0.04 ± 0.04 α / cm ² h, uranium: 0.1 ppm or less, and thorium: 0.1 ppm or less.

(Example 6)
The zirconium hydroxide obtained in Example 5 was calcined at 800 ° C. in an external heating furnace to obtain zirconium oxide, and the characteristic values were measured in the same manner as in Example 1. As a result, the molded body α-ray surface emission rate: 0.04 ± 0.03α / cm ² h, uranium: 0.1 ppm or less, thorium: 0.1 ppm or less.

(Example 7)
A solution obtained by adding 0.60 mol of sulfuric acid to zirconium oxide in 600 l of an aqueous zirconium oxychloride solution having a concentration of 60 g / l in terms of ZrO ₂ was heated to 80 ° C. with stirring to obtain a basic zirconium sulfate slurry. The pH of the slurry was 1 or less.

After cooling the obtained slurry to 60 ° C., basic zirconium sulfate was separated from the mother liquor with a filter press, and the solid content was neutralized with caustic soda (NaOH) to obtain zirconium hydroxide. The obtained zirconium hydroxide was dispersed in water, and filtration and washing were repeated three times to obtain a zirconium hydroxide cake, which was dried at 120 ° C. and crushed to obtain a zirconium hydroxide product. The product characteristic values were α-ray surface emission rate of the molded product: 0.13 ± 0.04 α / cm ² h, uranium: 0.1 ppm or less, and thorium: 0.1 ppm or less. Moreover, this was calcined at 800 ° C. in an external heating furnace to obtain zirconium oxide, and the characteristic values were measured in the same manner as in Example 1. As a result, the molded body α-ray surface emission rate: 0.04 ± 0.03α. / Cm ² h, uranium: 0.1 ppm or less, thorium: 0.1 ppm or less.

(Example 8)
A basic zirconium sulfate slurry was obtained by heating a solution obtained by adding 0.50 mol of ammonium sulfate to zirconium oxide in 600 l of an aqueous solution of zirconium oxychloride having a concentration of 180 g / l in terms of ZrO ₂ with stirring to 80 ° C. The pH of the slurry was 1 or less.

After cooling the obtained slurry to 60 ° C., basic zirconium sulfate was separated from the mother liquor with a filter press, and the solid content was neutralized with caustic soda (NaOH) to obtain zirconium hydroxide. The obtained zirconium hydroxide was dispersed in water, and filtration and washing were repeated three times to obtain a zirconium hydroxide cake, which was dried at 120 ° C. and crushed to obtain a zirconium hydroxide product. The characteristic values of the product were as follows: molded body α-ray surface emission rate: 0.09 ± 0.03 α / cm ² h, uranium: 0.1 ppm or less, thorium: 0.1 ppm or less. Moreover, this was calcined at 800 ° C. in an external heating furnace to obtain zirconium oxide, and the characteristic values were measured in the same manner as in Example 1. As a result, the molded body α-ray surface emission rate: 0.04 ± 0.03α. / Cm ² h, uranium: 0.1 ppm or less, thorium: 0.1 ppm or less.

Example 9
A basic zirconium sulfate slurry was obtained by heating a solution obtained by adding 0.70 mol of sulfuric acid to zirconium oxide in 600 l of a ZrO ₂ converted concentration of 120 g / l to 90 ° C. while stirring. The pH of the slurry was 1 or less.

After cooling the obtained slurry to 60 ° C., basic zirconium sulfate was separated from the mother liquor with a filter press, and the solid content was neutralized with ammonia water to obtain zirconium hydroxide. The obtained zirconium hydroxide was dispersed in water, and filtration and washing were repeated three times to obtain a zirconium hydroxide cake, which was dried at 120 ° C. and crushed to obtain a zirconium hydroxide product. Characteristic values of the product were as follows: molded body α-ray surface emission rate: 0.20 ± 0.05 α / cm ² h, uranium: 0.1 ppm or less, thorium: 0.1 ppm or less. Moreover, this was calcined at 800 ° C. in an external heating furnace to obtain zirconium oxide, and the characteristic values were measured in the same manner as in Example 1. As a result, the molded body α-ray surface emission rate: 0.04 ± 0.03α. / Cm ² h, uranium: 0.1 ppm or less, thorium: 0.1 ppm or less.

(Example 10)
A solution obtained by adding 0.60 mol of ammonium sulfate to zirconium oxide in 2 l of an aqueous solution of zirconium oxychloride having a concentration of 10 g / l in terms of ZrO ₂ was heated to 90 ° C. with stirring to obtain a basic zirconium sulfate slurry. The pH of the slurry was 1 or less.

After cooling the obtained slurry to 60 ° C., basic zirconium sulfate was separated from the mother liquor with Nutsche, the solid content was dispersed again in water, an aqueous solution containing 8 mol of yttrium chloride (YCl ₃ ) was added, and then with aqueous ammonia Neutralization gave zirconium hydroxide. The obtained zirconium hydroxide was dispersed in water, and filtration and washing were repeated three times to obtain a zirconium hydroxide cake, which was dried at 120 ° C. and crushed to obtain a stabilizer-containing zirconium hydroxide product. The characteristic values of the product were the molded body α-ray surface emission rate: 0.15 ± 0.04α / cm ² h, uranium: 0.1 ppm or less, and thorium: 0.1 ppm or less. Moreover, this was calcined at 800 ° C. in an external heating furnace to obtain zirconium oxide, and the characteristic values were measured in the same manner as in Example 1. As a result, the molded body α-ray surface emission rate: 0.04 ± 0.03α. / Cm ² h, uranium: 0.1 ppm or less, thorium: 0.1 ppm or less.

(Example 11)
A basic zirconium sulfate slurry was obtained by heating a solution obtained by adding 0.55 mol of sulfuric acid to zirconium oxide in 2 l of an aqueous solution of zirconium oxychloride having a concentration of 80 g / l in terms of ZrO ₂ with stirring to 90 ° C. The pH of the slurry was 1 or less.

After cooling the obtained slurry to 60 ° C., basic zirconium sulfate was separated from the mother liquor with Nutsche, the solid content was neutralized with aqueous ammonia, and then an aqueous solution containing 8 mol of yttrium chloride (YCl ₃ ) was added, followed by ammonia. Neutralization with water gave a stabilizer-containing zirconium hydroxide. The obtained stabilizer-containing zirconium hydroxide was dispersed in water, and filtration and washing were repeated three times to obtain a zirconium hydroxide cake, which was dried at 120 ° C. and crushed to obtain a zirconium hydroxide product. Characteristic values of the product were as follows: molded body α-ray surface emission rate: 0.10 ± 0.03 α / cm ² h, uranium: 0.1 ppm or less, thorium: 0.1 ppm or less. Moreover, this was calcined at 800 ° C. in an external heating furnace to obtain zirconium oxide, and the characteristic values were measured in the same manner as in Example 1. As a result, the molded body α-ray surface emission rate: 0.04 ± 0.03α. / Cm ² h, uranium: 0.1 ppm or less, thorium: 0.1 ppm or less.

(Comparative Example 1)
A basic zirconium sulfate slurry was obtained by heating a solution obtained by adding 0.50 mol of ammonium sulfate to zirconium oxide in 2 l of an aqueous solution of zirconium oxychloride having a ZrO ₂ conversion concentration of 50 g / l to 95 ° C. while stirring. The pH of the slurry was 1 or less.

The obtained slurry was cooled to 60 ° C. and immediately neutralized with aqueous ammonia to obtain zirconium hydroxide. The process of dispersing the obtained zirconium hydroxide slurry in water and filtering and washing was repeated three times to obtain a zirconium hydroxide cake, which was dried at 120 ° C. and crushed to obtain a product, which was the same as in Example 1. The characteristic values were measured as follows. Molded body α-ray surface release rate: 1.4 ± 0.1 α / cm ² h, uranium: 0.5 ppm or less, thorium: 0.3 ppm or less.

(Comparative Example 2)
The zirconium hydroxide obtained in Comparative Example 1 was calcined at 800 ° C. in an external heating furnace to obtain zirconium oxide. The obtained powder was molded under the same conditions as in Example 1 and the characteristic values were measured. As a result, α-ray surface emission rate: 1.6 ± 0.1 α / cm ² h, uranium: 0.6 ppm or less, thorium: It was 0.4 ppm.

Claims (5)

Hydroxylation characterized in that the contents of uranium and thorium are each limited to 0.2 mass ppm or less, and the α-ray surface emission rate when formed into a molded body is 0.5 α / cm ² h or less. zirconium. Zirconium oxide characterized in that the contents of uranium and thorium are each limited to 0.2 mass ppm or less, and the α-ray surface emission rate when formed into a molded body is 0.5 α / cm ² h or less Powder. Preparing a zirconium oxychloride solution;
Sulfate ion is added to the obtained zirconium oxychloride solution in an amount sufficient for basic zirconium sulfate (Zr (OH) _(4-2X) (SO ₄ ) _X · nH ₂ O) to form 0 <X <2. And heating to produce basic zirconium sulfate,
Separating the produced basic zirconium sulfate from the mother liquor while maintaining the pH of the mother liquor at 7 or less,
Adding alkali to the resulting basic zirconium sulfate to produce zirconium hydroxide,
Separating and washing the produced zirconium hydroxide,
The content of uranium and thorium content is limited to 0.2 mass ppm or less, and the α-ray surface emission rate when formed into a molded body is 0.5 α / cm ² h or less. A method for producing zirconium hydroxide, comprising: 2. The hydroxide according to claim 1, wherein a stabilizer-forming agent is added before alkali is added to basic zirconium sulfate or after alkali is added to basic zirconium sulfate to form zirconium hydroxide. A method for producing zirconium. The zirconium hydroxide powder produced by the method according to claim 1 or 2 is calcined, and the contents of uranium and thorium are each limited to 0.2 mass ppm or less, and A production method of zirconium oxide powder, wherein the α-ray surface emission rate is 0.5α / cm ² h or less.