JPH0742109B2 - Method for producing indium oxide powder - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a high-density ITO (indium oxide containing tin oxide, which is an abbreviation of Indium-Tin-Oxide) for forming a transparent conductive film, which is a raw material powder for manufacturing a sputtering target. The present invention relates to a method for producing indium powder and a high density sintered body.

[0002]

2. Description of the Related Art The following methods have been proposed as a method for producing indium oxide, but there are still many problems to be solved.

I) Ammonia water in an aqueous solution of indium salt,
This is a method for producing an indium oxide by adding an alkali hydroxide such as sodium hydroxide to obtain a hydroxide, and drying and firing the hydroxide. The hydroxide produced by this method is gel-like and difficult to pass through, and the oxide obtained by firing is also a hard lump and is extremely difficult to pulverize.

II) The following is a method of directly oxidizing and decomposing indium metal or salt to produce indium oxide, but in this method, a large amount of nitrogen oxide is generated when the salt is decomposed, which is not environmentally preferable. In addition, it is difficult to oxidize the metal sufficiently to the center of the lump. Furthermore, the oxide obtained by this method is in the form of a hard lump, and it is extremely difficult to grind it as in the above method I).

III) The following is the method described in JP-A-54-45697, that is, urea is added to an indium salt solution and heated to generate ammonia to generate indium hydroxide, This is a method for producing indium oxide by drying and firing it.

IV) The following are the methods described in JP-A-62-7627 and JP-A-1-290527, that is, the hydroxide obtained by the above method I) is washed with alcohol or acetone. This is a method for facilitating the crushing, or a method for replacing the solvent by adding an organic solvent and distilling. However, this method requires a large amount of the organic solvent.

However, the above-mentioned conventional techniques have many problems, particularly the following drawbacks.

B) In the above methods I) and II), the oxide particles obtained are coarse and the particles are hard, so that they cannot be practically pulverized.

(B) Next, in the method of III), particles are not generated unless the temperature is kept high for a long time, and the oxide finally obtained by the method has a characteristic acicular particle-like coagulation. It will be a collection. If this form is left as it is, for example, when it is molded by a pressure molding method, the moldability is poor and the final properties of the molded product are adversely affected.

C) In the above method IV), since a large amount of expensive organic solvent is used, the cost is remarkably high.

As described above, the prior art has many problems to be solved, and has the drawbacks such as fatal (a), b) and c).

[0012]

DISCLOSURE OF THE INVENTION The present invention solves many problems and drawbacks of the prior art as described above, can be dispersed and pulverized by a simple crushing process, and particles can be obtained. An object of the present invention is to provide a method for producing an indium oxide fine powder having a primary particle shape close to a sphere without orientation and at a low cost, and a method for producing a high density sintered body having a relative density of 70% or more for a sputtering target.

[0013]

According to the present invention, when indium oxide is produced from an indium salt aqueous solution, easily disintegratable indium oxide can be produced by producing a precipitate of indium carbonate as an indium oxide synthesis intermediate. It is a technology developed as a result of earnest research based on the knowledge.

That is, in the first invention, at least one selected from an alkali carbonate and an alkali bicarbonate is added to an aqueous solution of indium salt at 60 ° C. or lower, and the mixture is reacted, followed by solid-liquid separation to obtain a precipitate. A method for producing indium oxide powder having a specific surface area of 20 m ² / g or more, which comprises drying and calcination

In a second aspect of the present invention, at least one selected from alkali carbonate and alkali bicarbonate is added to an indium salt aqueous solution at 60 ° C. or lower, and the mixture is reacted, followed by solid-liquid separation and drying the resulting precipitate. , Specific surface area obtained by calcination 2
A method for producing tin oxide-added indium oxide powder, which comprises mixing 85 to 95% by weight of indium oxide powder of 0 m ² / g or more and 5 to 15% by weight of tin oxide.

In a third aspect of the invention, at least one selected from an alkali carbonate and an alkali bicarbonate is added to an indium salt aqueous solution at 60 ° C. or lower, and the mixture is reacted, followed by solid-liquid separation, and drying the obtained precipitate. , Specific surface 20 obtained by calcination
Relative density 70 for a sputtering target, characterized by mixing 85 to 95% by weight of indium oxide powder of m ² / or more and 5 to 15% by weight of tin oxide, followed by pressure molding and firing.
% Of the high density sintered body is manufactured.

Next, the present invention will be described in detail.

In producing the precipitate of the indium compound, at least one selected from alkali carbonate and alkali bicarbonate, preferably ammonium salt, is used in the indium salt aqueous solution as a precipitant, and the indium concentration is 50 to 80 g / l. 1.2 to 3.0 equivalents of a precipitating agent was added to the aqueous solution of 1 while maintaining the liquid temperature of the aqueous solution at 40 to 60 ° C. to cause a reaction, and a precipitate of an indium compound was generated. The obtained precipitate is a compound mainly composed of indium carbonate. In this indium compound formation reaction, the liquid temperature is an important condition, and when the reaction is carried out at the liquid temperature above 60 ° C., the compound mainly containing indium hydroxide precipitates.

Here, the present inventors use indium carbonate-based precipitates and indium hydroxide-based precipitates as bases to dry and calcine both precipitates to produce indium oxide. Comparing the characteristics, it was found that indium oxide produced by using indium carbonate as an intermediate product is remarkably easy to disintegrate, and the specific surface area value of indium oxide obtained by calcination is also extremely high. The invention was made.

In contrast to the above, ammonia water was used as a precipitant, and an indium salt aqueous solution having an indium concentration of 70 g / l was maintained at a liquid temperature of 40 to 60 ° C. to cause a reaction to cause precipitation of an indium compound, which was obtained. The precipitate was a compound mainly composed of indium hydroxide. When this precipitate was dried and calcined to produce indium oxide in the same manner as above, a hard lump was formed, which was difficult to pulverize, and the specific surface area value was extremely low, and thus good indium oxide as described above could not be obtained. .

Next, indium carbonate was produced as an intermediate product (that is, according to the method of the present invention) to change the firing temperature to produce fine powders having various specific surface area values. The specific surface area value of this indium oxide powder is from 2 m ² / g to 55
After setting the range to m ² / g, and adding and mixing tin oxide powder to each so as to be 5% by weight, a test piece with a diameter of 1 inch is molded by cold press at a molding pressure of 1 Ton / cm ^2. After that, it was sintered at 1500 ° C. for 60 minutes, and the relative density of the test piece corresponding to the sample having each specific surface area value was measured. The result is shown in FIG.

In FIG. 1, the horizontal axis represents the raw powder specific surface area value (m ² /
g) and the relative density (%) of the sintered body on the vertical axis, and the relationship between the raw material powder specific surface area value and the relative density of the sintered body (1500 ° C. × 60
Is a graph showing (calcining for 1 minute), and ○ indicates a molding pressure of 1To.
n / cm ² , ● indicates a molding pressure of 1.5 Ton / cm ² , and Δ indicates a molding pressure of 3.0 Ton / cm ² .

When used as an ITO target,
It is necessary that the relative density is 60% or more, preferably 70% or more. When the relative density is less than 60%, the wear rate is fast and the mechanical strength is weak, and the product is destroyed by thermal shock during use. Easy and not practical.

The ITO target provided by the present invention has a specific surface area value of the raw material powder of 1 as can be seen from FIG.
When the molding pressure is 0 m ² / g or more and the pressure is 1 Ton / cm ² or more, the relative density of the sintered body is 60% or more, which is almost practical, and when the specific surface area value is 20 m ² / g or more, the relative Density is almost 70% or more, further 30m ² / g
With the above, the relative density exceeds 80%, and depending on the conditions, a high-density target material having a relative density of about 95% can be obtained.

As described above, in the production of indium oxide from an indium salt aqueous solution, a precipitate mainly composed of indium carbonate is produced as an intermediate product, which is then washed, dried and calcined so that it can be easily disintegrated. Indium oxide can be produced. Therefore, fine pulverization is not necessary at all, a high-density sintered body can be obtained, and since there is no contamination due to pulverization, high purity is maintained.

[0026]

Example 1 1000 g of indium metal was dissolved in nitric acid to obtain a pH of 1.
After adjusting to 0, water was added to make 14 l of indium salt aqueous solution, and ammonium bicarbonate 329 was added as a precipitant.
0 g was prepared, and an indium carbonate aqueous solution was added and reacted so that the liquid temperature did not exceed 60 ° C. to generate a precipitate of indium carbonate. This precipitate was separated by filtration, washed with water and dried at 100 ° C., and then the calcination temperature shown in Table 1 (500 to 1100).
Calcination) and crushing, and then tin oxide fine powder (specific surface area value of 4 m ² / g) was added and mixed so as to be 5% by weight respectively, and then at a molding pressure of 1 to ³ Ton / cm ^2. Molded, 150
A sintered body of ITO was produced by firing at 0 ° C. for 60 minutes. In addition, as a comparative example, ammonia water (28%
Concentration and other conditions were the same as those in the above-described example, and a powder and a sintered body thereof were manufactured as a prototype.

The relative density of the sintered bodies of the sintered body according to the present invention and the comparative sintered body produced as described above was measured. The results are shown in Table 1.

[0028]

[Table 1]

As can be seen from the results in Table 1, the calcination temperature is 98
Sintered body No. produced as a trial at each forming pressure (1 to 3 Ton / cm ² ) at 0 ° C. or less. 3 to No. 6 has a relative density of 60%
, Especially No. 4 to No. In No. 6, the relative density is 75% or more. In addition, Comparative Example No. Even with No. 7, a sintered body having a relative density of about 70% can be obtained. 4, N
o. 5, No. It is understood that it is much inferior to that of No. 6, and it is difficult to improve the relative density.

Example 2 An indium nitrate solution and ammonium bicarbonate were prepared in the same manner as in Example 1, and the reaction temperature (liquid temperature) for producing the indium carbonate precipitate was changed within the range of 20 to 65 ° C. After the indium precipitate was generated, washed with water and dried, the calcination temperature was further changed to 570 ° C, 650 ° C, 720 ° C,
After calcination by changing the temperature to 900 ° C. and 1000 ° C. and crushing, tin oxide fine powder was added and mixed in the same manner as in Example 1, molded at a molding pressure of 3.0 Ton / cm ² , and fired at 1500 ° C. for 60 minutes. Then, an ITO sintered body was manufactured as a prototype. The relative densities of these prototype sintered bodies were measured, and the relationship between the reaction temperature and the relative density of the sintered bodies during the wet formation reaction of indium carbonate was determined. The result is shown in FIG.

In FIG. 2, the reaction temperature (° C.) is plotted on the horizontal axis and the relative density (%) of the sintered body is plotted on the vertical axis, and the relationship between the reaction temperature and the relative density of the sintered body plotted by calcination temperature is shown. It is a graph, the mark is calcination temperature 570 ° C, and the triangle is calcination temperature 650
℃, ● indicates calcination temperature 720 ℃, ○ indicates calcination temperature 900
℃, ▲ is a curve when the calcination temperature is 1000 ℃.

As can be seen from FIG. 2, when the calcination temperature is 900 ° C. or lower, the reaction temperature is 60 ° C. or lower, preferably 35 to 60.
By forming the indium carbonate precipitate in the range of ° C, the relative density of the obtained sintered body becomes approximately 70% or more. Further, in the reaction temperature range of 40 to 55 ° C., the relative density is 7
It can be seen that the relative density is 5% or more, and the relative density is 85% or more in the range of the calcination temperature of 550 to 700 ° C. and the reaction temperature of 40 to 55 ° C.

[0033]

According to the method of the present invention, when synthesizing indium oxide by a wet reaction, indium carbonate is produced as an intermediate product instead of indium hydroxide, so that the crushability of indium oxide is significantly increased. As a result, a high-density sintered body having a relative density of 70% or more for a sputtering target can be manufactured at low cost by a room temperature pressure molding-normal pressure sintering process, which requires almost no fine pulverization step. .

Further, according to the method of the present invention, since the reached relative density is high and contamination due to crushing can be prevented, a high-purity high-density sintered body can be manufactured.

[Brief description of drawings]

FIG. 1 is a graph showing a relationship between a specific surface area of raw material powder and a relative density of a sintered body.

FIG. 2 is a graph showing the relationship between reaction temperature and relative density of a sintered body.

Claims (3)

[Claims] 1. An indium salt aqueous solution at 60 ° C. or lower is added with at least one selected from an alkali carbonate and an alkali bicarbonate, and the mixture is reacted, followed by solid-liquid separation, and the obtained precipitate is dried and calcined. Specific surface area of 20 m ²
/ G or more of the method for producing indium oxide powder. 2. At least one selected from an alkali carbonate and an alkali bicarbonate is added to an aqueous indium salt solution having a temperature of 60 ° C. or lower and reacted, followed by solid-liquid separation, and the obtained precipitate is dried and calcined. 85 to 95% by weight of indium oxide powder having a specific surface area of 20 m ² / g or more and tin oxide of 5 to 15
A method for producing tin oxide-added indium oxide powder, characterized by being mixed with a weight percentage. 3. At least one selected from alkali carbonate and alkali bicarbonate is added to an aqueous solution of indium salt at 60 ° C. or lower to react, then solid-liquid separation is performed, and the obtained precipitate is dried and calcined. 85 to 95% by weight of indium oxide powder having a specific surface area of 20 m ² / g or more and tin oxide of 5 to 15
A method for producing a high-density sintered body having a relative density of 70% or more for a sputtering target, characterized in that the mixture is mixed with 1% by weight and pressure-molded and fired.