KR102129451B1 - Method for producing indium hydroxide powder, method for producing indium oxide powder, and sputtering target - Google Patents

Abstract

Indium hydroxide powder having a uniform particle size and a narrow particle size distribution is prepared. In the method of producing indium hydroxide powder by electrolysis using metal indium on the anode, the electrolyte concentration of the electrolyte is 0.1 to 2.0 mol/L, the pH is 2.5 to 5.0, the liquid temperature is 20 to 60°C, and the electrode current The density is set to ⁴ to 20 A/dm ² , and electrolysis is performed so that the concentration of the electrolytic slurry containing the precipitated indium hydroxide powder is within a range of 2 to 15%.

Description

METHOD FOR PRODUCING INDIUM HYDROXIDE POWDER, METHOD FOR PRODUCING INDIUM OXIDE POWDER, AND SPUTTERING TARGET}

The present invention relates to a method for producing indium hydroxide powder and an indium oxide powder capable of obtaining indium hydroxide powder having excellent particle size uniformity and a narrow particle size distribution width, and a sputtering target using the obtained indium oxide powder. . This application claims priority based on Japanese Patent Application No. Patent Application No. 2013-111289 filed on May 27, 2013 in Japan, and this application is incorporated in this application by reference.

In recent years, the use of a transparent conductive film as an application for a solar cell or a touch panel is increasing, and the demand for materials for forming a transparent conductive film, such as a sputtering target, is increasing. Indium oxide-based sintered materials are mainly used for the material for forming the transparent conductive film. Indium oxide powder is used as the main raw material for forming a transparent conductive film. It is preferable that the indium oxide powder used for the sputtering target has a small particle size distribution as much as possible in order to obtain a high density target.

As an indium oxide powder production method, it is mainly produced by a so-called neutralization method in which the precipitation of indium hydroxide produced by neutralizing an acidic aqueous solution such as an indium nitrate aqueous solution or an indium chloride aqueous solution with an alkaline aqueous solution such as ammonia water is dried and calcined.

In the neutralization method, in order to suppress aggregation of the obtained indium oxide powder, a method of obtaining acicular indium hydroxide by alkali addition to an aqueous indium nitrate solution at a high temperature of 70 to 95°C has been proposed (for example, see Patent Document 1). It has been disclosed that by calcining the needle-like indium hydroxide, an indium oxide powder with little aggregation can be obtained.

However, the indium oxide powder produced by the neutralization method tends to have uneven particle size and particle size distribution, and there is a problem that particles of relatively large size coexist. For this reason, when a sputtering target is produced using such indium oxide, there arises problems such as voids between particles caused by large particles and difficulty in improving density.

In addition, in the neutralization method, there is a problem that the wastewater treatment cost increases because a large amount of nitrogen drainage occurs after the production of indium oxide powder.

As a method for improving this, a method of producing an indium oxide powder by calcining the metal indium to produce a precipitate of indium hydroxide powder, and so-called electrolytic method has been proposed (for example, see Patent Document 2). In this method, compared to the neutralization method, the amount of nitrogen drainage after the production of indium oxide powder can be significantly reduced, and the particle size of the obtained indium oxide powder can be made uniform.

However, the indium hydroxide powder obtained by the electrolytic method has a problem that the pH of the electrolytic solution is close to neutral and is very fine and easy to aggregate. Although the primary particle diameter of the indium oxide powder obtained by calcining it is relatively uniform, it is easy to obtain agglomerated powder in which these particles are strongly aggregated. Since the width of the particle size distribution is widened by agglomeration, there is a problem that densification of the target is inhibited.

Therefore, in the method for producing indium hydroxide powder, there is a need for a method for obtaining indium hydroxide powder having a uniform particle size and a narrow particle size distribution by using an electrolytic method with a small amount of nitrogen after production.

Patent Document 1: Japanese Patent No. 3314388 Patent Document 2: Japanese Patent No. 2829556

Therefore, the present invention has been proposed in view of such a situation, and it is difficult to aggregate, the particle size is uniform, and the method for producing an indium hydroxide powder capable of obtaining an indium hydroxide powder having a narrow particle size distribution width and the obtained indium hydroxide powder are calcined. An object of the present invention is to provide a method for producing an indium oxide powder to obtain an indium oxide powder and a sputtering target produced using the obtained indium oxide powder.

The method for producing indium hydroxide powder according to the present invention for achieving the above object is a method for preparing indium hydroxide powder by electrolysis using metal indium on an anode, wherein the concentration of the electrolyte is 0.1 to 2.0 mol/ L, the pH is 2.5 to 5.0, the liquid temperature is 20 to 60°C, the electrode current density is 4 to 20 A/dm ² , and the concentration of the electrolytic slurry containing precipitated indium hydroxide powder is in the range of 2 to 15%. It is characterized in that electrolysis is performed as much as possible.

The method for producing an indium oxide powder according to the present invention for achieving the above object is characterized by being obtained by calcining the indium hydroxide powder described above.

The sputtering target according to the present invention, which achieves the above object, is characterized in that it is produced by using the indium oxide powder obtained by the indium oxide production method.

In the present invention, the concentration of the electrolytic solution, pH, liquid temperature, electrode current density is controlled, and electrolysis is performed so that the concentration of the electrolytic slurry containing the precipitated indium hydroxide powder is within a specific range. Indium hydroxide powder having a uniform particle size and a narrow particle size distribution width can be produced. Accordingly, in the present invention, by using the obtained indium hydroxide powder, an indium oxide powder having a uniform particle size and a narrow particle size distribution width can be obtained, and a high-density sputtering target can be obtained.

1 is a schematic view of an electrolytic device used in Examples and Comparative Examples.
2 is a schematic view showing the arrangement of a cathode and an anode in the electrolytic apparatus.

Hereinafter, a method for producing an indium oxide powder to which the present invention is applied and a sputtering target using indium oxide powder obtained by the production method will be described. In addition, this invention is not limited to the following detailed description, unless there is particular limitation. The method of manufacturing the indium oxide powder to which the present invention is applied and the embodiment of the sputtering target will be described in detail in the following procedure.

1. Manufacturing method of indium oxide powder

1-1. Manufacturing process of indium hydroxide powder

1-2. Indium hydroxide powder recovery process

1-3. Drying process of indium hydroxide powder

1-4. Production process of indium oxide powder

2. Sputtering target

1. Manufacturing method of indium oxide powder

(1-1. Manufacturing process of indium hydroxide powder)

The indium hydroxide powder production method uses an electrolytic reaction to produce indium hydroxide powder.

In the method of manufacturing indium hydroxide powder, indium is used as an anode (anode), a conductive metal or carbon electrode is used for a cathode (cathode), and the anode and cathode are immersed in an electrolyte to generate a potential difference between the anodes to generate electric current. By doing so, the anode metal is dissolved. In electrolysis, by controlling the pH of the electrolytic solution to a region that is lower than the solubility of indium hydroxide, precipitation of indium hydroxide powder is caused, thereby obtaining indium hydroxide powder.

For the anode, for example, metal indium or the like is used. The metal indium to be used is not particularly limited, but a high-purity one is preferable to suppress the incorporation of impurities into the indium oxide powder. As an appropriate metal indium, a purity of 99.9999% (commonly called 6N product) is used as a suitable product.

As the cathode, a conductive metal, carbon electrode, or the like is used, for example, insoluble titanium or the like can be used.

As the electrolytic solution, an aqueous solution of a general electrolyte salt such as water-soluble nitrate, sulfate, or chloride salt can be used. Among them, an aqueous solution of ammonium nitrate using ammonium nitrate that does not leave impurities after drying and calcination after precipitation of indium hydroxide powder is preferred.

The concentration of the electrolytic solution is 0.1 to 2.0 mol/L. The lower the concentration of the electrolytic solution, the cheaper it is, but when the concentration is lower than 0.1 mol/L, the electrical conductivity of the electrolytic solution is too low to generate current, or it is not preferable because the required voltage exceeds the practical range. On the other hand, if the concentration of the electrolytic solution is 2.0 mol/L, sufficient electrical conductivity is ensured, and if it is higher than 2.0 mol/L, it is not economical, and there is no need to increase it further.

The pH of the electrolytic solution is in the range of 2.5 to 5.0. When the pH is less than 2.5, precipitation of the hydroxide does not occur, and when it is greater than 5.0, the precipitation rate of the hydroxide is too fast, and the precipitate is formed with a concentration unevenness, so that the particle size distribution is wide, which is undesirable. In addition, since the pH at which the hydroxide causes precipitation is also influenced by the coexisting ions, it is necessary to adjust the pH within the range of 2.5 to 5.0. In addition, since the dissolution stability of the hydroxide is improved by coexistence of an oxygen-containing chelating compound such as citric acid, tartaric acid and glycolic acid, or a nitrogen-containing chelating agent such as ethylenediamine tetraacetic acid (EDTA), the presence of these hydroxides is appropriately considered. It is necessary to adjust the pH to precipitate.

The liquid temperature of the electrolytic solution is 20 to 60°C. When the temperature is lower than 20°C, the precipitation rate of the hydroxide becomes too slow, and when the temperature is higher than 60°C, the precipitation rate becomes too fast, so that the precipitate is formed with concentration unevenness, thereby increasing the particle size distribution width and controlling the particle size distribution width small. It is not desirable because it cannot be done.

The current density is in the range of 4 to ²⁰ A/dm ² . When the current density is lower than 4 A/dm ² , the production rate of indium hydroxide powder is lowered. In addition, if the current density is too high, the reaction in which indium precipitates on the cathode begins to take precedence over the occurrence of hydroxide precipitation, and as a result, the precipitated indium metal is mixed with the indium hydroxide metal, which is not preferable. When it is higher than 20 A/dm ² , the tendency becomes remarkable, which is undesirable. In addition, it is not preferable because an increase in the electrolytic voltage may easily cause a rise in liquid temperature, and a problem such as difficulty in electrolysis due to passivation of the surface of the metal indium of the anode.

It is preferable that the distance between the electrodes between the anode and the cathode is within a range of 1 cm to 4 cm. When it is narrower than 1 cm, it is not preferable because physical contact easily occurs and short circuits and the like easily occur. When it is wider than 4 cm, it is not preferable because no current is generated or the required voltage is outside the practical range.

The electrolysis is carried out within a range of 2 to 15% of the concentration of the electrolytic solution (hereinafter also referred to as electrolytic slurry) deposited by indium hydroxide powder. The amount of precipitation of the indium hydroxide powder increases with the progress of electrolysis, but when the concentration is lower than 2%, the concentration is too low, so the efficiency of solid-liquid separation is low, which is undesirable. In addition, when it is higher than 15%, the viscosity of the electrolyte is too high, and since it is inhibited from uniformly diffusing in the electrolyte, precipitation is formed while the concentration is uneven, and the particle size distribution width is not reduced, which is not preferable.

(1-2. Recovery process of indium hydroxide powder)

The indium hydroxide powder obtained by electrolysis is solid-liquid-separated from the electrolytic solution, and the separated indium hydroxide powder is washed with pure water to separate and collect again.

Although it does not specifically limit as a solid-liquid separation method, For example, a rotary filter, centrifugation, a filter press, pressure filtration, reduced pressure filtration, etc. are mentioned, for example.

(1-3. Drying process of indium hydroxide powder)

Next, the recovered indium hydroxide powder is dried.

The drying method is performed with a dryer such as a spray dryer, an air convection type drying furnace, or an infrared drying furnace.

The drying conditions are not particularly limited as long as the moisture of the indium hydroxide powder can be removed, but the drying temperature is preferably in the range of 80°C to 150°C, for example. When the drying temperature is lower than 80°C, drying becomes insufficient, and when it is higher than 150°C, it changes from indium hydroxide to indium oxide. The drying time varies depending on the temperature, but is about 10 hours to 24 hours.

In the above-described method for producing indium hydroxide powder, in the electrolysis, the concentration of the electrolytic solution is 0.1 to 2.0 mol/L, the pH is 2.5 to 5.0, the liquid temperature is in the range of 20 to 60°C, and the positive electrode and the negative electrode are immersed in the electrolytic solution. By performing electrolysis within a range in which the electrode current density is in the range of 4 A/dm ² to 20 A/dm ² and the concentration of the electrolytic slurry is ² to 15%, it is difficult to aggregate, the particle size is uniform, and the particle size distribution width A narrow indium hydroxide powder can be obtained.

In addition, the shape of the primary particles of the obtained indium hydroxide powder becomes a columnar shape. As the primary particles of the indium hydroxide powder are columnar, aggregation is appropriately suppressed, and spherical secondary particles having a narrow particle size distribution of submicron or submicron are obtained.

(1-4. Indium oxide powder production process)

In the production process of indium oxide powder, indium hydroxide powder after calcination is calcined to produce indium oxide powder. The calcination conditions are preferably performed at a calcination temperature of 600°C to 800°C and a calcination time of 1 hour to 10 hours, for example. Further, in the indium oxide powder production step, pulverization or pulverization may be performed, if necessary, in order to make the indium hydroxide powder a more desired particle size. In the indium oxide powder production step, when ammonium nitrate is used for the electrolytic solution, decomposition of ammonium nitrate occurs by calcination, so that incorporation into the indium oxide powder can be prevented.

In the production method of the indium oxide powder as described above, when the indium hydroxide powder is produced by the electrolytic method, the concentration, pH, liquid temperature, and electrode current density of the electrolytic solution are controlled as described above, and the electrolysis containing the precipitated indium hydroxide powder As electrolysis is performed so that the concentration of the slurry is within a specific range, the produced indium hydroxide powder has a uniform particle size and a narrow particle size distribution width can be produced. Accordingly, in the method for producing indium oxide powder, indium oxide powder having a uniform particle size and a narrow particle size distribution width can be calcined, thereby obtaining indium oxide powder having a uniform particle size and a narrow particle size distribution width.

Moreover, in the manufacturing method of an indium oxide powder, nitrogen drainage amount after manufacture of an indium oxide powder can be suppressed compared with the neutralization method.

2. Sputtering target

The indium oxide powder obtained by calcining the indium hydroxide powder obtained by the above-described method for producing indium hydroxide powder is used, for example, as a raw material for a sputtering target used for forming a transparent conductive film.

A granulated powder obtained by mixing the above-described indium oxide powder with other raw materials of a target such as tin oxide powder at a predetermined ratio is produced. Next, a molded body is produced using, for example, a cold press method using granulated powder. Next, the molded body is sintered under atmospheric pressure in a temperature range of 1300°C to 1600°C, for example. Next, if necessary, processing such as polishing the plane or side surface of the sintered body is performed. Then, by bonding the sintered body to a Cu backing plate, an indium tin oxide sputtering target (ITO sputtering target) can be obtained.

In the manufacturing method of the sputtering target, since the particle size of the indium oxide powder serving as a raw material is uniform and the particle size distribution width is narrow, a high-density sintered body can be obtained and the target density can be increased. Thereby, cracking does not occur during processing of the target, and abnormal discharge during sputtering can be suppressed.

In addition, indium oxide powder is added not only to the raw material of the sputtering target, but also to the conductive paste and the transparent conductive film coating. Since the indium oxide powder has a uniform particle size, it exhibits high dispersion when added to a conductive paste or a transparent conductive film coating.

Example

Hereinafter, specific examples to which the present invention is applied will be described, but the present invention is not limited to these examples.

In the following examples and comparative examples, indium hydroxide powder was produced using the electrolytic device 1 shown in FIG. 1. The specific configuration of the electrolytic device will be described in Example 1.

(Example 1)

The electrolytic device 1 is provided with a 36 L electrolyzer 2 with a length of 30 cm, a width of 40 cm, and a depth of 30 cm, and an 80 L adjustment tank 3 with a length of 40 cm, a width of 40 cm, and a depth of 50 cm. (2) and the adjustment tank (3) are adjacent. The electrolytic tank 2 and the adjusting tank 3 are connected by a circulation pump 4.

The electrolytic cell 2 is provided with a punch plate 6 for dispersing the liquid flow of the electrolytic solution 5 parallel to the floor at a height of 2 cm from the bottom. That is, in the punch plate 6, holes of 5 mm long, 5 rows wide, and 25 diameters 3 mm per 10 cm square are opened at regular intervals in a checkerboard shape. Accordingly, in the electrolytic cell 2, the electrolytic solution 5 injected into the lower part of the electrolytic cell 2 by the circulation pump 4 passes through the punch plate 6, and each of the fluids provides a substantially uniform liquid flow without drift. Can be secured.

In addition, the cathode 7 and the anode 8 were arranged in the electrolytic cell 2 as shown in FIG. 2. On the negative electrode (cathode) 7, five titanium metal plates with a thickness of 1 mm, a width of 30 cm, and a height of 25 cm were prepared. Four anodes (anodes) 8 were prepared by molding 99.9999% indium metal in a plate shape of 30 cm wide, 25 cm high, and 5 mm thick. As shown in Fig. 2, these five cathodes 7 and four anodes 8 were vertically arranged on the punch plate 6 in the electrolytic cell 2 such that the anodes were parallel to each other. The distance between the cathode 7 and the anode 8 was adjusted to 3.0 cm and arranged. The five cathodes 7 are electrically connected by a conducting wire 9.

The adjustment tank 3 is provided with a temperature control heater 11 and a cooler 12 for controlling and maintaining the temperature of the electrolyte. In addition, the adjustment tank 3 is provided with a stirring bar 13 for stirring the electrolyte 5 in the tank.

In the electrolytic device 1, 60 L of 2.0 mol/L aqueous ammonium nitrate solution is contained in the adjustment tank 3. In the adjustment tank 3, 1N nitric acid was added to the aqueous ammonium nitrate solution of the electrolytic solution 5, and the pH of the hydrogen ion concentration index was adjusted to 4.0. The pH was measured using the pH electrode 10 attached to the adjustment tank 3. While maintaining this state, the temperature of the electrolytic solution 5 was maintained at 25°C using the temperature-controlled heater 11 and the cooler 12 as well. In the adjustment tank 3, the electrolytic solution 5 in the tank was stirred with the stirring bar 13 to adjust the electrolytic solution 5.

During electrolysis, the electrolytic solution 5 in the adjustment tank 3 was sent to the electrolytic bath 2 at a rate of 20 L/min by the circulation pump 4. The electrolytic solution 5 of the electrolytic bath 2 is returned to the adjustment bath 3 by overflow.

Electrode current density was adjusted to 15 A/dm ² to continue electrolysis for 6 hours. The indium hydroxide powder precipitated by electrolysis was collected by filtering under reduced pressure with a Nutsche filter bottle.

Table 1 shows the results of measuring the particle size distribution of the recovered indium hydroxide powder by a laser light Doppler method. The particle size distribution of the indium hydroxide powder was 0.3 μm in minimum diameter and 1.2 μm in maximum diameter, and had a well-defined range of particle size distribution.

Next, the obtained indium hydroxide powder was dried under static conditions in the air at 120°C for 12 hours, and calcined at 700°C in the air. The obtained indium oxide had a particle size distribution of 0.5 µm minimum diameter and 1.2 µm maximum diameter, and had a particle size distribution in a well-defined range. From the results of examining the weight of the solid content, the concentration of the electrolytic slurry in electrolysis was 3.2 wt%.

Thereafter, a sintered body of indium oxide alone was produced by a cold press atmospheric pressure sintering method. As a result, the density of the sintered body was 99.5% high with respect to the true specific gravity of indium oxide 7.18 g/cm ³ .

(Example 2)

In Example 2, electrolysis was performed in the same manner as in Example 1, except that the ammonium nitrate aqueous solution of the electrolytic solution was 0.5 mol/L under the conditions of Example 1. Then, an indium oxide sintered body was produced from the obtained indium hydroxide powder in the same manner as in Example 1.

In Example 2, the concentration of the indium hydroxide powder in the electrolytic solution was 3.2 wt%. In addition, the particle size distribution of the indium hydroxide powder measured in the same manner as in Example 1 was a minimum diameter of 0.3 μm and a maximum diameter of 1.0 μm, and had a well-defined range of particle size distribution. Similarly, the particle size distribution of the indium oxide powder was 0.5 μm in the minimum diameter and 1.2 μm in the maximum diameter, and was a particle size distribution in the same limited range. The density of the indium oxide sintered body was as high as 99.6% relative to the specific gravity.

(Example 3)

In Example 3, electrolysis was performed in the same manner as in Example 1, except that the electrolysis temperature was set to 50°C under the conditions of Example 1. Then, an indium oxide sintered body was produced from the obtained indium hydroxide powder in the same manner as in Example 1.

In Example 3, the concentration of the indium hydroxide powder in the electrolytic solution was 3.2 wt%. In addition, the particle size distribution of the indium hydroxide powder measured in the same manner as in Example 1 was a minimum diameter of 0.3 μm and a maximum diameter of 1.2 μm, and had a well-defined range of particle size distribution. Similarly, the particle size distribution of the indium oxide powder was 0.5 μm in the minimum diameter and 1.2 μm in the maximum diameter, and was a particle size distribution in the same limited range. The density of the indium oxide sintered body was 99.5% high density relative to the true specific gravity.

(Example 4)

In Example 4, electrolysis was performed in the same manner as in Example 1, except that the electrode current density was 8 A/dm ² under the conditions of Example 1. Then, an indium oxide sintered body was produced from the obtained indium hydroxide powder in the same manner as in Example 1.

In Example 4, the concentration of the indium hydroxide powder in the electrolytic solution was 2.0 wt%. In addition, the particle size distribution of the indium hydroxide powder measured in the same manner as in Example 1 was a minimum diameter of 0.3 μm and a maximum diameter of 1.2 μm, and had a well-defined range of particle size distribution. Similarly, the particle size distribution of the indium oxide powder was 0.5 μm in the minimum diameter and 1.2 μm in the maximum diameter, and was a particle size distribution in the same limited range. The density of the indium oxide sintered body was 99.5% high density with respect to true specific gravity.

(Example 5)

In Example 5, electrolysis was performed in the same manner as in Example 1, except that the electrode current density was 17 A/dm ² under the conditions of Example 1. Then, an indium oxide sintered body was produced from the obtained indium hydroxide powder in the same manner as in Example 1.

In Example 5, the concentration of the electrolytic slurry was 3.2 wt%. In addition, the particle size distribution of the indium hydroxide powder measured in the same manner as in Example 1 was 0.3 μm in the minimum diameter and 1.2 μm in the maximum diameter, and had a particle size distribution in a limited range. Similarly, the particle size distribution of the indium oxide powder was 0.5 μm in the minimum diameter and 1.2 μm in the maximum diameter, and was a particle size distribution in the same limited range. The indium oxide sintered compact had a high density of 99.3% relative to the true specific gravity.

(Example 6)

In Example 6, electrolysis was performed in the same manner as in Example 1, except that the current density was 19 A/dm ² and the electrolysis time was 15 hours under the conditions of Example 1. Then, an indium oxide sintered body was produced from the obtained indium hydroxide powder in the same manner as in Example 1.

In Example 6, the concentration of the electrolytic slurry was 12.0 wt%. In addition, in the particle size distribution of indium hydroxide measured in the same manner as in Example 1, the minimum diameter was 0.2 μm and the maximum diameter was 1.4 μm, and the particle size distribution was within a limited range. Similarly, the particle size distribution of indium oxide was a minimum diameter of 0.6 μm and a maximum diameter of 1.4 μm, and was a particle size distribution in the same limited range. Further, the density of the indium oxide sintered body was high density of 99.2% relative to the true specific gravity.

(Example 7)

In Example 7, electrolysis was performed in the same manner as in Example 1, except that the electrolyte concentration was set to 1.0 mol/L and the distance between electrodes was 1.5 cm under the conditions of Example 1. Then, an indium oxide sintered body was produced from the obtained indium hydroxide powder in the same manner as in Example 1.

In Example 7, the concentration of the electrolytic slurry was 3.2 wt%. In addition, the particle size distribution of the indium hydroxide powder measured in the same manner as in Example 1 was 0.3 μm in the minimum diameter and 1.2 μm in the maximum diameter, and had a particle size distribution in the same limited range. Similarly, the particle size distribution of the indium oxide powder was 0.5 μm in the minimum diameter and 1.2 μm in the maximum diameter, and the particle size distribution was equally well defined. In addition, the density of the indium oxide sintered body was high density of 99.5% relative to the true specific gravity.

(Comparative Example 1)

In Comparative Example 1, electrolysis was performed in the same manner as in Example 1, except that the electrolyte concentration was 0.04 mol/L and the electrode current density was 6 A/dm ² under the conditions of Example 1.

As a result, the voltage applied in order to meet the predetermined current density greatly deviated from the commercial range, and a stable voltage value could not be maintained.

(Comparative Example 2)

In Comparative Example 2, electrolysis was performed in the same manner as in Example 1, except that the electrolyte concentration was 3.0 mol/L under the conditions of Example 1.

In Comparative Example 2, the concentration of the electrolytic slurry was 3.2 wt%. In addition, the particle size distribution of the indium hydroxide powder measured in the same manner as in Example 1 is a minimum diameter of 0.3 μm and the maximum diameter of 3.0 μm. Similarly, the particle size distribution of an indium oxide powder is the minimum diameter of 0.3 μm and the maximum diameter of 3.0 μm. The distribution was wider than the results in Examples 1-7. Further, the relative density of the indium oxide sintered body was 89.7%, and was obviously lower than in Examples 1 to 7.

(Comparative Example 3)

In Comparative Example 3, electrolysis was performed in the same manner as in Example 1, except that the pH of electrolysis was 2.3, the electrolysis temperature was 30° C., and the electrolysis time was 4 hours under the conditions of Example 1.

As a result, electrolysis of the anode indium did not proceed, and precipitation of indium hydroxide did not proceed at all.

(Comparative Example 4)

In Comparative Example 4, electrolysis was performed in the same manner as in Example 1, except that the pH of electrolysis was set to 6.5 under the conditions of Example 1. Then, an indium oxide sintered body was prepared from the obtained indium hydroxide powder in the same manner as in Example 1.

As a result, the concentration of the electrolytic slurry was 3.2 wt%. In addition, the particle size distribution of the indium hydroxide powder measured in the same manner as in Example 1 is a minimum diameter of 0.1 μm, the maximum diameter of 9.0 μm, the same is the particle size distribution of the indium oxide powder is a minimum diameter of 0.2 μm, the maximum diameter of 8.8 μm, all examples The distribution was broad compared to the results in 1 to 7. Further, the relative density of the indium oxide sintered body was 87.0%, which was an apparently lower value than Examples 1 to 7.

(Comparative Example 5)

In Comparative Example 5, electrolysis was performed in the same manner as in Example 1, except that the electrolysis temperature was 18°C under the conditions of Example 1. Then, an indium oxide sintered body was produced from the obtained indium hydroxide powder in the same manner as in Example 1.

In Comparative Example 5, the concentration of the electrolytic slurry was 3.2 wt%. In addition, the particle size distribution of the indium hydroxide powder measured in the same manner as in Example 1 is a minimum diameter of 0.8 μm, the maximum diameter is 2.8 μm, the same is the particle size distribution of the indium oxide powder is a minimum diameter of 0.9 μm, the maximum diameter is 3.0 μm, all of the Examples The distribution was broad compared to the results in 1 to 7. Further, the relative density of the indium oxide sintered body was 91.0%, which was an apparently lower value than Examples 1 to 7.

(Comparative Example 6)

In Comparative Example 6, electrolysis was performed in the same manner as in Example 1, except that the electrolysis temperature was 65°C under the conditions of Example 1. Then, an indium oxide sintered body was produced from the obtained indium hydroxide powder in the same manner as in Example 1.

In Comparative Example 6, the concentration of the electrolytic slurry was 3.2 wt%. In addition, the particle size distribution of the indium hydroxide powder measured in the same manner as in Example 1 was 0.2 μm in the minimum diameter and 8.0 μm in the maximum diameter. Similarly, the particle size distribution in the indium oxide powder was 0.2 μm in the minimum diameter and 8.2 μm in the maximum diameter. The distribution was wider than the results in Examples 1-7. Further, the relative density of the indium oxide sintered body was 88.0%, which was an apparently lower value than Examples 1 to 7.

(Comparative Example 7)

In Comparative Example 7, electrolysis was performed in the same manner as in Example 1, except that the electrode current density was 2 A/dm ² and the electrolysis time was 12 hours under the conditions of Example 1. Then, an indium oxide sintered body was produced from the obtained indium hydroxide powder in the same manner as in Example 1.

In Comparative Example 7, the concentration of the electrolytic slurry was small, so that 1.0 wt% was not satisfied. In addition, the particle size distribution of the indium hydroxide powder measured in the same manner as in Example 1 was 0.2 μm in the minimum diameter and 2.8 μm in the maximum diameter. Similarly, the particle size distribution in the indium oxide powder was 0.8 μm in the minimum diameter and 3.1 μm in the maximum diameter. The distribution was wider than the results in Examples 1-7. Further, the relative density of the indium oxide sintered body was 90.0%, which was an apparently lower value than Examples 1 to 7.

(Comparative Example 8)

In Comparative Example 8, electrolysis was performed in the same manner as in Example 1 except that the temperature of the electrolytic solution was set to 28° C. and the electrode current density was set to 28 A/dm ² under the conditions of Example 1. Then, an indium oxide sintered body was produced from the obtained indium hydroxide powder in the same manner as in Example 1.

In Comparative Example 8, the concentration of the electrolytic slurry was 6.0 wt%. In addition, the particle size distribution of the indium hydroxide powder measured in the same manner as in Example 1 was 0.2 μm in the minimum diameter and 8.1 μm in the maximum diameter. Similarly, the particle size distribution in the indium oxide powder was 0.3 μm in the minimum diameter and 8.3 μm in the maximum diameter. The distribution was wider than the results in Examples 1-7. Further, the relative density of the indium oxide sintered body was 89.0%, which was an apparently lower value than Examples 1 to 7.

(Comparative Example 9)

In Comparative Example 9, electrolysis was performed in the same manner as in Example 1, except that the electrolysis time was set to 34 hours under the conditions of Example 1. Then, an indium oxide sintered body was produced from the obtained indium hydroxide powder in the same manner as in Example 1.

In Comparative Example 9, the concentration of the electrolytic slurry was 18.0 wt%. In addition, the particle size distribution of the indium hydroxide powder measured in the same manner as in Example 1 was 0.3 μm in the minimum diameter and 2.0 μm in the maximum diameter, and the particle size distribution in the indium oxide powder was 0.5 μm in the minimum diameter and 2.0 μm in the maximum diameter. The distribution was wider than the results in Examples 1-7. Further, the relative density of the indium oxide sintered body was 96.2%, which was an apparently lower value than Examples 1 to 7.

(Comparative Example 10)

In Comparative Example 10, electrolysis was performed in the same manner as in Example 1, except that the electrolysis time was 42 hours under the conditions of Example 1. Then, an indium oxide sintered body was produced from the obtained indium hydroxide powder in the same manner as in Example 1.

In Comparative Example 10, the concentration of the electrolytic slurry was 22.0 wt%. In addition, the particle size distribution of the indium hydroxide powder measured in the same manner as in Example 1 was 0.7 μm in the minimum diameter and 2.8 μm in the maximum diameter, and the particle size distribution in the indium oxide powder was 0.8 μm in the minimum diameter and 3.0 μm in the maximum diameter. The distribution was wider than the results in Examples 1-7. Further, the relative density of the indium oxide sintered body was 91.0%, which was an apparently lower value than Examples 1 to 7.

(Comparative Example 11)

In Comparative Example 11, electrolysis was performed in the same manner as in Example 1, except that the distance between the electrodes was 0.5 cm under the conditions of Example 1.

As a result, a short circuit occurred due to contact between the electrodes, and the current value was not stable, so that stable electrolysis could not be performed.

(Comparative Example 12)

In Comparative Example 12, electrolysis was performed in the same manner as in Example 1, except that the distance between the electrodes was 5.0 cm under the conditions of Example 1. However, if the distance between the electrodes is 5.0 cm, since the same number of electrode plates as in Example 1 cannot be placed in the electrolytic cell, three cathodes and two anodes were prepared and alternately arranged in the electrolytic cell. Then, an indium oxide sintered body was produced from the obtained indium hydroxide powder in the same manner as in Example 1.

In Comparative Example 12, the concentration of the electrolytic slurry was 3.2 wt%. The particle size distribution of this indium hydroxide was measured in the same manner as in Example 1, and the minimum diameter was 0.6 μm and the maximum diameter was 3.0 μm. Similarly, the particle size distribution of the indium oxide powder was the minimum diameter was 0.8 μm, the maximum diameter was 3.0 μm, and all were performed. The distribution was wider than the results in Examples 1-7. Further, the relative density of the indium oxide sintered body was 93.0%, which was an apparently lower value than Examples 1 to 7.

(Comparative Example 13)

In Comparative Example 13, under the conditions of Example 1, the electrolyte concentration was 0.5 mol/L, the pH of the electrolyte was 8.0, the electrolysis temperature was 10°C, and the electrode current density was 12 A/dm ² Electrolysis was performed in the same manner as in Example 1 except for this. Then, an indium oxide sintered body was produced from the obtained indium hydroxide powder in the same manner as in Example 1.

In Comparative Example 13, the concentration of the electrolytic slurry was 2.6 wt%. In addition, the particle size distribution of the indium hydroxide powder measured in the same manner as in Example 1 is a minimum diameter of 0.1 μm and a maximum diameter of 8.5 μm. Similarly, the particle size distribution of indium oxide is a minimum diameter of 0.2 μm and a maximum diameter of 8.8 μm. The distribution was broad compared to the results in 1 to 7. Further, the relative density of the indium oxide sintered body was 87.0%, which was an apparently lower value than Examples 1 to 7.

(Comparative Example 14)

Comparative Example 14, except that the concentration of the electrolyte in the conditions of Example 1 to 1.0 mol / L, the pH of the electrolyte to 6.0, the electrolysis temperature to 50 ℃, and the electrode current density of 12 A / dm ² Electrolysis was performed in the same manner as in Example 1. Then, an indium oxide sintered body was produced from the obtained indium hydroxide powder in the same manner as in Example 1.

In Comparative Example 14, the concentration of the electrolytic slurry was 2.6 wt%. The particle size distribution of this indium hydroxide powder was measured in the same manner as in Example 1, and the minimum diameter was 0.1 μm and the maximum diameter was 8.0 μm. The distribution was broad compared to the results in Examples 1 to 7. Further, the relative density of the indium oxide sintered body was 87.0%, which was an apparently lower value than Examples 1 to 7.

As described above, from the results of Examples and Comparative Examples, as in Examples 1 to 7, the concentration of the electrolytic solution was 0.1 to 2.0 mol/L, the pH was 2.5 to 5.0, the liquid temperature was 20 to 60°C, and the electrode current density was 4 A/ By performing electrolysis so that the concentration of dm ² to 20 A/dm ² and the concentration of indium hydroxide powder in the electrolytic solution satisfies 2 to 15%, the particle size distribution width of the indium hydroxide powder and indium oxide powder is narrow, the particle diameter is uniform, and indium oxide It can be seen that the density of the sintered body is high.

Claims (7)

In the production method of the indium hydroxide powder to produce indium hydroxide powder by electrolysis using metal indium on the anode,
The concentration of the electrolyte is 0.1 to 2.0 mol/L, the pH is 2.5 to 5.0, the liquid temperature is 20 to 60°C,
The electrode current density is 4 to 20 A/dm ² , the distance between the electrodes is 1 to 4 cm,
Method for producing indium hydroxide powder, characterized in that electrolysis is performed so that the concentration of the electrolytic slurry containing the precipitated indium hydroxide powder is in the range of 2 to 15%. The method of claim 1, wherein the electrolytic solution is ammonium nitrate. The method for producing indium hydroxide powder according to claim 1 or 2, wherein the primary particles of the indium hydroxide powder have a columnar shape. In the method for producing an indium oxide powder obtained by calcining indium hydroxide powder obtained by electrolysis using metal indium as an anode, to obtain indium oxide powder,
The concentration of the electrolyte is 0.1 to 2.0 mol/L, the pH is 2.5 to 5.0, the liquid temperature is 20 to 60°C,
The electrode current density is 4 to 20 A/dm ² , the distance between the electrodes is 1 to 4 cm,
Method for producing indium oxide powder, characterized in that electrolysis is performed so that the concentration of the electrolytic slurry containing the precipitated indium hydroxide powder is in the range of 2 to 15%. The method of claim 4, wherein the electrolytic solution is ammonium nitrate. The method for producing an indium oxide powder according to claim 4 or 5, wherein the primary particles of the indium hydroxide powder have a columnar shape. delete

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