TW201329289A - Method for producing gallium hydroxide, method for producing gallium oxide powder, gallium oxide powder, gallium oxide sintered compact and sputtering target formed from sintered compact - Google Patents

Abstract

A method for producing gallium hydroxide is characterized in that gallium hydroxide is crystallized by electrolysis in an aqueous ammonium nitrate solution using liquid gallium metal as the anode. A method for producing a gallium oxide powder is characterized in that gallium hydroxide is dried and calcined to obtain gallium oxide powder. Provided is technology relating to a gallium oxide and gallium oxide powder that can be produced easily and inexpensively, as well as a sintered compact and sputtering target produced from the powder. A high-density target can be produced without the formation of cracks or sintering defects during the target production steps.

Description

Method for producing gallium hydroxide, method for producing gallium oxide powder, gallium oxide powder, sintered body of gallium oxide, and sputtering target composed of the sintered body

The present invention relates to a gallium oxide powder used as a raw material for sputtering a sputtering target, a method for producing gallium hydroxide powder as a raw material of the gallium oxide powder, and a sintered body using a gallium oxide and a sintered body sputtering target.

In recent years, development of a thin film transistor using a transparent oxide semiconductor has been progressing, and a transparent oxide semiconductor has been attracting attention from the viewpoints of low-temperature film formation and high mobility. Among them, In-Ga-Zn-O (hereinafter referred to as "IGZO") material having indium, gallium, zinc, and oxygen as constituent elements or Ga-Zn-O containing gallium, zinc, and oxygen as constituent elements (described below) The material "GZO" is considered to be the best.

The method of producing the IGZO film or the GZO film is most suitable for the sputtering method excellent in mass productivity, and therefore, the IGZO target or the GZO target needs to have a high density. However, in the case of manufacturing a high-density IGZO target or a GZO target, it is often troublesome to have a product (batch) whose density is often lowered or a crack or poor sintering of the target.

In order to solve such a problem, efforts have been made since the prior art to improve the properties of the gallium oxide powder which improves the main raw material. For example, Patent Document 1 discloses a method in which a neutralization method is used to neutralize under specific conditions in the presence of oxalic acid, thereby obtaining a gallium oxide powder having a sharp particle size distribution, and a high density can be obtained by using the powder. target. However, according to the toxic and hazardous substance management law, oxalic acid is designated as a non-medical hazardous substance, which is not good for industrial production.

Non-Patent Document 1 discloses a method in which α-type Ga ₂ O ₃ is obtained by sintering crystalline α-GaOOH at 400 to 600 °C. However, since a method of neutralizing gallium chloride by sodium hydroxide is employed, chlorine and sodium remain in the raw material powder and remain in the sintered body produced using the same.

Patent Document 2 describes a method in which metal gallium is dissolved in nitric acid to obtain an aqueous solution of gallium nitrate, neutralized with aqueous ammonia, and the resulting precipitate is filtered, washed, dried, and then calcined at 600 ° C to produce oxidation. Gallium powder. However, since the neutralization conditions are not optimized, a large amount of fine powder of 1 μm or less or coarse particles of less than about 100 μm is produced.

Patent Document 3 discloses a method for producing gallium oxide by an electrolytic method. In this method, it is necessary to cool the electrolyte to store the gallium anode as a solid. Therefore, the cooling of the electrolyte requires a great amount of power. Further, even when the electrolytic solution is cooled, heat is generated by the energization from time to time, so that the temperature of the electrode and the vicinity thereof locally rises due to the heat generation, so that the gallium anode dissolves and falls off and falls into a state in which electrolysis is impossible, and the risk is high. . Therefore, there is a problem that it is difficult to operate stably and is not suitable for mass production.

Patent Document 1: Japanese Laid-Open Patent Publication No. Hei 11-322335

Patent Document 2: Japanese Patent No. 4178485

Patent Document 3: Japanese Patent Laid-Open No. Hei 10-273318

Non-patent literature

Non-Patent Document 1: Taichi Sato et al., Thermochimica Acta 53, p. 281-288 (1982)

The present invention has been made in view of such circumstances, and an object thereof is to efficiently and easily manufacture and provide a transparent half which is suitable for high-density fabrication by sputtering. A gallium oxide powder of a sputtering target required for a conductor IGZO film or a GZO film, and gallium hydroxide used for the gallium oxide powder. Further, after painstaking research on the causes of density reduction or target cracking and poor sintering in the production of IGZO targets or GZO targets, it was found that the frequency of such problems and the chlorine content and sodium content of impurities which are unavoidable impurities. Related, so you need to reduce it.

Moreover, the prior art method for producing gallium oxide powder by the neutralization method has the following problems: in the initial stage and the final stage, the number and balance of ions in the bath are different, the properties of the powder are unstable, and a large amount of NOx is generated during nitric acid leaching. Moreover, since the liquid after neutralization is a high-concentration nitrogen-based wastewater, the environmental load is extremely large.

On the other hand, in the case of the electrolysis method, the pH of the bath is fixed, and since the hydroxide can be precipitated by stable leaching by electrolysis, the properties of the powder are uniform, and the sinterability can be improved. The NOx gas is not generated at the time of taking, and the electrolyte can be repeatedly used, so that the amount of waste water itself can be reduced and the concentration of nitrogen in the wastewater can be lowered.

However, in the previous electrolysis method, it was necessary to cool the electrolyte to store the gallium anode as a solid, and the cooling of the electrolyte required energy. Further, since the temperature of the electrode and its vicinity rises due to heat generation during electrolysis, there is a risk that the gallium anode dissolves and falls off, so that it is difficult to operate stably and is not suitable for mass production.

Based on this finding, the following invention is provided.

(1) A method for producing gallium hydroxide by crystallizing gallium hydroxide by using liquid metal gallium as an anode and performing electrolysis in an aqueous solution of ammonium nitrate.

(2) The method for producing gallium hydroxide according to (1) above, wherein the electrolyte is The liquid temperature was set to 30 to 60 ° C, the pH was set to 4 to 7, and the electrolytic solution concentration was set to 0.5 to 2 mol/L to carry out electrolysis.

(3) A method for producing gallium oxide powder, which comprises drying and calcining gallium hydroxide produced by the above (1) or (2) to obtain gallium oxide powder.

(4) A gallium oxide powder obtained by the production method of the above (3), wherein the gallium oxide powder has a chlorine content of 10 wtppm or less, a sodium content of 10 wtppm or less, an average particle diameter of 0.5 μm to 3 μm, and a particle size distribution. It is 0.1 to 10 μm and has a BET specific surface area of 5 to 20 m ² /g.

(5) A gallium oxide sintered body obtained by using the gallium oxide powder of the above (4) as a raw material.

(6) A gallium oxide sputtering target comprising the gallium oxide sintered body of the above (5).

The invention has the following effects, and can solve the disadvantages of the prior art method for manufacturing gallium oxide powder by the neutralization method, that is, the following problems: in the initial stage and the final stage, the number and balance of ions in the bath are different, and the properties of the powder are unstable. A large amount of NOx is generated during the leaching of nitric acid, and the neutralized liquid is a high-concentration nitrogen-based wastewater, so the environmental load is extremely large.

Further, the present invention provides a new electrolysis method which eliminates the disadvantages of the prior electrolysis method, that is, it is necessary to cool the electrolyte to store the gallium anode as a solid, and the cooling of the electrolyte requires energy, and the electrode and the electrode thereof can be eliminated. The risk of melting and falling off the gallium anode caused by the nearby temperature rise. Thereby, there is an effect that the operation can be stably performed and the mass productivity can be improved.

Further, the cause of the target crack or the poor sintering, that is, the chlorine content of the impurity and the content of the sodium can be reduced.

Thereby, there is an excellent effect that gallium oxide powder suitable for producing a sputtering target required for forming a transparent semiconductor IGZO film or a GZO film by sputtering at a high density can be efficiently and easily manufactured, and used for the oxidation Gallium hydroxide of gallium powder. Further, it has an effect of suppressing a decrease in density or suppressing generation of target cracks or poor sintering in the production of an IGZO target or a GZO target.

As a representative use of gallium oxide, there is a sputtering target. In order to use as a target and to improve film properties and sinterability after sputtering, high purity is required.

When hydrochloric acid or sodium hydroxide is used, impurities are not easily cleaned. Therefore, as a method for high purity, a nitric acid leaching ammonia neutralization method is mainly known.

However, in the neutralization method, the amount and balance of ions in the bath may be different in the initial stage and the final stage of the reaction, and the properties of the powder are unstable. Further, there is a problem in that since a large amount of NOx is generated during the leaching of nitric acid and the liquid after neutralization is a high-concentration nitrogen-based wastewater, the environmental load is extremely large.

On the other hand, in the case of the electrolysis method, the pH of the bath is fixed, and since the hydroxide can be precipitated by stable leaching by electrolysis, the properties of the powder are uniform, and the sinterability can be improved. No NOx gas is produced during electrolytic leaching. Further, since the electrolytic solution can be reused, it is characterized in that the amount of waste water itself can be reduced and the concentration of nitrogen in the wastewater can be lowered.

Patent Document 3 discloses a method for producing gallium oxide by an electrolytic method. As described above, it is necessary to cool the electrolytic solution to store the gallium anode as a solid, and the cooling of the electrolytic solution requires energy. Also, the electrode and its vicinity Since the temperature rises due to heat generation during electrolysis, there is a risk that the gallium anode dissolves and falls off, so that it is difficult to operate stably and is not suitable for mass production.

In the present invention, an electrolytic method is employed. The method for producing gallium hydroxide according to the present invention uses liquid metal gallium as an anode and electrolyzes in an aqueous solution of ammonium nitrate to crystallize gallium hydroxide. That is, the anode does not use a solid, but uses liquid gallium as an anode.

Fig. 1 shows an example of a method for producing gallium hydroxide by electrolysis according to the present invention. As shown in Fig. 1, liquid metal gallium 1 is present in the lower portion of the electrolytic cell, and the liquid gallium 1 is an anode. Symbol 2 is a metal for energization. Symbol 3 denotes a cathode.

Gallium hydroxide 6 is crystallized in an electrolytic solution (aqueous ammonium nitrate solution) 5 by electrolysis. Symbol 4 is an insulating portion. Further, the current-carrying metal 2 is a material which does not solidify with gallium and has good wettability with liquid metal gallium, and is not particularly limited as long as it has such properties.

As a result, there is an advantage that the gallium anode is stored as a solid without cooling the electrolytic solution, and there is no risk that the gallium anode dissolves and falls off, so that stable operation can be achieved. This can be said to be a new concept not disclosed in the prior art. Moreover, since the neutralization method is not used, there is no problem in sinterability, and there is no environmental load (nitrogen-based wastewater, NOx generation), and it is an excellent method.

That is, since NOx gas is not generated in the electrolysis method and the electrolytic solution can be repeatedly used, the amount of waste water can be reduced, and the concentration of nitrogen in the wastewater can be reduced.

Further, the production of gallium oxide is carried out by preliminarily manufacturing gallium hydroxide and baking it to form gallium oxide. Therefore, it can be used in gallium hydroxide High purity is achieved in the manufacturing step.

In the production of the above-mentioned gallium hydroxide, it is preferred to set the liquid temperature of the electrolytic solution to 30 to 60 ° C, set the pH to 4 to 7, and set the electrolytic solution concentration to 0.5 to 2 mol/L for electrolysis. It is usually manufactured within this range.

If the liquid temperature is too low, gallium will solidify, so that stable production is difficult. Further, if liquid gallium is present in a range where electrolysis does not occur, even if a part of the electrolytic cell is solidified, there is no particular problem.

On the other hand, if the liquid temperature is too high, the amount of chemical reagent consumption increases due to the excessive evaporation of the electrolyte and ammonia, which is not preferable. Further, when the temperature is higher than the required temperature, the heating device for maintaining the liquid temperature is increased in size or the material of the device is limited, so the liquid temperature of the above electrolyte is preferred. When the pH is too high, the particles aggregate and the sinterability is deteriorated. Further, when the pH is too low, since gallium hydroxide is chemically dissolved to lower the yield, it is preferably in the above range.

When the concentration of the electrolytic solution is too high, the particles aggregate and the sinterability is deteriorated. If the concentration is too low, the pH fluctuation due to electrolysis tends to be large. In order to cope with this pH fluctuation, nitric acid and ammonia water are added, but since it is easily added to the required amount or more at this time, the pH becomes unstable. Therefore, the above range is a preferred condition.

However, depending on the amount or condition of manufacture, some modifications may be tolerated outside of this range.

Then, the crystallized Ga(OH) ₃ particles were subjected to solid-liquid separation, and then dried at about 120 ° C to obtain GaO (OH). Then, it is baked at 400 ° C or more for 1 to 10 hours to obtain a gallium oxide (Ga ₂ O ₃ ) powder. The upper limit of the calcination temperature is not limited by the change in physical properties, but it is preferably set to 1200 ° C or less from the viewpoint of the material of the apparatus, the life, and the like.

Thereby, a gallium oxide powder having a chlorine content of 10 wtppm or less, a sodium content of 10 wtppm or less, an average particle diameter of 0.5 μm to 3 μm, a particle size distribution of 0.1 to 10 μm, and a BET specific surface area of 5 to 20 m ² /g can be produced. In order to avoid the influence of impurities on the density decrease, it is preferred to use a raw material having a purity of 4 N or more. Furthermore, the purity does not include impurities that are inevitably contained.

If the content of chlorine and sodium exceeds 10 wtppm, the BET specific surface area of the gallium oxide (Ga ₂ O ₃ ) powder is lowered, which is not preferable. On the other hand, since chlorine and sodium are inevitable impurities, they cannot be completely removed, but it is preferable to reduce them as much as possible. The average particle diameter is set to 0.5 μm to 3 μm, the particle size distribution is set to 0.1 to 10 μm, and the BET specific surface area is set to 5 to 20 m ² /g, which is a condition for improving the sinterability, and is preferably in the form of a gallium oxide powder. Gallium oxide powder having the preferred conditions can be produced by the present invention.

Further, the gallium oxide powder of the present invention may have a crystal structure of an α type or a β type. In addition to the α type or the β type, gallium oxide has a crystal structure of γ type, δ type, and ε type.

When sintering is performed using gallium oxide powder, α-type or β-type gallium oxide powder having good mass productivity is usually used, but powders of other crystal structures may also be used. The phase structure of the above (α, β) gallium oxide powder can be arbitrarily obtained by adjusting the baking temperature. Further, when the gallium oxide powder having the phase structure is sintered, it is usually transformed into a β phase.

The gallium oxide powder can be produced by using the gallium oxide powder described above as a raw material, and the gallium oxide sputtering target composed of the gallium oxide sintered body can be suitably used as an In-Ga-Zn-O (IGZO) oxide sintered compact target, for example. Ga-Zn-O (GZO)-based oxide sintered body target.

The oxide sintered body sputtering target of the present invention has a chlorine content of 10 wtppm or less, a sodium content of 10 wtppm or less, an average particle diameter of 0.5 μm to 3 μm, a particle size distribution of 0.1 to 10 μm, and a BET specific surface area of 5 Å as described above. 20 m ² /g, a gallium oxide powder having a crystal structure of α type is used as a raw material, and by using the gallium oxide powder, cracks or sintering defects due to gallium oxide are not generated in the target production step, and can be easily produced. Density sputtering target.

The oxide sintered body sputtering target of the present invention can be applied to all targets containing the above-mentioned gallium oxide as a target component. Therefore, it is easy to understand that other components and contents are not particularly limited.

Example

Hereinafter, description will be made based on examples and comparative examples. Furthermore, the present embodiment is merely an example and is not limited by the examples. That is, the present invention is only limited by the scope of the claims, and includes various modifications other than the embodiments included in the present invention.

In the examples and comparative examples shown below, various measurements or evaluations were required, and the conditions are as follows.

(Measurement of particle size distribution)

The measurement of the particle size distribution was carried out using a particle size distribution measuring apparatus (manufactured by Nikkiso Co., Ltd., Microtrac MT3000).

(Measurement of specific surface area)

The measurement of the specific surface area (BET) was carried out using an automatic surface area meter β-sorb (manufactured by Nikkiso Co., Ltd., MODEL-4200).

(Example 1)

The liquid metal gallium having a purity of 4N is charged to the electrolysis shown in FIG. In the tank, the electrolytic solution was electrolyzed using an aqueous solution of ammonium nitrate. The electrolyte temperature at this time was set to 30 ° C, the pH was set to 6, and the electrolyte concentration was set to 1.0 mol/L.

As other conditions, DSE was used as a material for energizing the anode, Ti was used for the cathode, and the current density was set to 10 A/dm ² .

Thereby, Ga(OH) ₃ crystallized in the solution was obtained. An SEM image of the crystallized particles is shown in Fig. 2 . As shown in Fig. 2, finely dispersed particles can be obtained. Then, the Ga(OH) _{3 was} suction-filtered to carry out solid-liquid separation, and then dried at about 120 ° C to obtain GaO(OH). Then, the dried powder was baked at about 1000 ° C for 4 hours to produce a gallium oxide powder.

As a result, the content of chlorine and sodium in the gallium oxide powder is less than the detection limit, that is, less than 10 wtppm. Further, the BET specific surface area was as high as 12.58 m ² /g, and the average particle diameter determined from the particle size distribution was 0.83 μm, which was within the range of the present invention. The crystal of the calcined powder is a β phase (β-form).

Further, the obtained gallium oxide powder was used as a raw material for production, and the (111) composition of the IGZO sintered body target was produced, and the density was measured. As a result, the Archimedes density was as high as 6.25 g/cm ³ . It is considered that this is because the pulverization property of the obtained gallium oxide is good, and the effect by mixing and pulverization is easy in the sintering operation. The above results are shown in Table 1.

(Example 2)

The liquid metal gallium having a purity of 4 N was charged into the electrolytic cell shown in Fig. 1 in the same manner as in Example 1, and the electrolytic solution was electrolyzed using an aqueous solution of ammonium nitrate. The temperature of the electrolytic solution at this time was set to 40 ° C, the pH was set to 4, and the electrolytic solution concentration was set to 1.0 mol/L.

As other conditions, DSE was used as a material for energizing the anode, Ti was used for the cathode, and the current density was set to 10 A/dm ² .

Thereby, Ga(OH) ₃ crystallized in the solution was obtained. As in Example 1, finely dispersed particles were obtained. Then, the Ga(OH) _{3 was} suction-filtered to carry out solid-liquid separation, and then dried at about 120 ° C to obtain GaO(OH). Then, the dried powder was baked at about 1000 ° C for 4 hours to produce a gallium oxide powder.

As a result, the content of chlorine and sodium in the gallium oxide powder is less than the detection limit, that is, less than 10 wtppm. Further, the BET specific surface area was as high as 10.72 m ² /g, and the average particle diameter determined from the particle size distribution was 0.86 μm, which was within the range of the present invention. The crystal of the calcined powder is a β phase (β-form).

Further, the obtained gallium oxide powder was used as a raw material for production, and the (111) composition of the IGZO sintered body target was produced, and the density was measured. As a result, the Archimedes density was as high as 6.25 g/cm ³ . It is considered that this is because the pulverization property of the obtained gallium oxide is good, and the effect by mixing and pulverization is easy in the sintering operation. The above results are also shown in Table 1.

(Example 3)

The liquid metal gallium having a purity of 4 N was charged into the electrolytic cell shown in Fig. 1 in the same manner as in Example 1, and the electrolytic solution was electrolyzed using an aqueous solution of ammonium nitrate. The electrolyte temperature at this time was set to 40 ° C, the pH was set to 7, and the electrolyte concentration was set to 1.0 mol/L.

As other conditions, DSE was used as a material for energizing the anode, Ti was used for the cathode, and the current density was set to 10 A/dm ² .

Thereby, Ga(OH) ₃ crystallized in the solution was obtained. As in Example 1, finely dispersed particles were obtained. Then, the Ga(OH) _{3 was} suction-filtered to carry out solid-liquid separation, and then dried at about 120 ° C to obtain GaO(OH). Then, the dried powder was baked at about 1000 ° C for 4 hours to produce a gallium oxide powder.

As a result, the content of chlorine and sodium in the gallium oxide powder is less than the detection limit, that is, less than 10 wtppm. Further, the BET specific surface area was as high as 8.73 m ² /g, and the average particle diameter determined from the particle size distribution was 1.06 μm, which was within the range of the present invention. The crystal of the calcined powder is a β phase (β-form).

Further, the obtained gallium oxide powder was used as a raw material for production, and the (111) composition of the IGZO sintered body target was produced, and the density was measured. As a result, the Archimedes density was as high as 6.26 g/cm ³ . It is considered that this is because the pulverization property of the obtained gallium oxide is good, and the effect by mixing and pulverization is easy in the sintering operation. The above results are shown in Table 1 in the same manner.

(Example 4)

The liquid metal gallium having a purity of 4 N was charged into the electrolytic cell shown in Fig. 1 in the same manner as in Example 1, and the electrolytic solution was electrolyzed using an aqueous solution of ammonium nitrate. The electrolyte temperature at this time was set to 40 ° C, the pH was set to 6, and the electrolyte concentration was set to 0.5 mol/L.

As other conditions, DSE was used as a material for energizing the anode, Ti was used for the cathode, and the current density was set to 10 A/dm ² .

Thereby, Ga(OH) ₃ crystallized in the solution was obtained. As in Example 1, finely dispersed particles were obtained. Then, the Ga(OH) _{3 was} suction-filtered to carry out solid-liquid separation, and then dried at about 120 ° C to obtain GaO(OH). Then, the dried powder was baked at about 1000 ° C for 4 hours to produce a gallium oxide powder.

As a result, the content of chlorine and sodium in the gallium oxide powder is less than the detection limit, that is, less than 10 wtppm. Further, the BET specific surface area was as high as 10.46 m ² /g, and the average particle diameter determined from the particle size distribution was 0.91 μm, which was within the range of the present invention. The crystal of the calcined powder is a β phase (β-form).

Further, the obtained gallium oxide powder was used as a raw material for production, and the (111) composition of the IGZO sintered body target was produced, and the density was measured. As a result, the Archimedes density was as high as 6.27 g/cm ³ . It is considered that this is because the pulverization property of the obtained gallium oxide is good, and the effect by mixing and pulverization is easy in the sintering operation. The above results are shown in Table 1 in the same manner.

(Example 5)

The liquid metal gallium having a purity of 4 N was charged into the electrolytic cell shown in Fig. 1 in the same manner as in Example 1, and the electrolytic solution was electrolyzed using an aqueous solution of ammonium nitrate. The electrolyte temperature at this time was set to 50 ° C, the pH was set to 6, and the electrolyte concentration was set to 2.0 mol/L.

As other conditions, DSE was used as a material for energizing the anode, Ti was used for the cathode, and the current density was set to 10 A/dm ² .

Thereby, Ga(OH) ₃ crystallized in the solution was obtained. As in Example 1, finely dispersed particles were obtained. Then, the Ga(OH) _{3 was} suction-filtered to carry out solid-liquid separation, and then dried at about 120 ° C to obtain GaO(OH). Then, the dried powder was baked at about 1000 ° C for 4 hours to produce a gallium oxide powder.

As a result, the content of chlorine and sodium in the gallium oxide powder is less than the detection limit, that is, less than 10 wtppm. Further, the BET specific surface area was as high as 7.85 m ² /g, and the average particle diameter determined from the particle size distribution was 1.41 μm, which was within the range of the present invention. The crystal of the calcined powder is a β phase (β-form).

Further, the obtained gallium oxide powder was used as a raw material for production, and the (111) composition of the IGZO sintered body target was produced, and the density was measured. As a result, the Archimedes density was as high as 6.25 g/cm ³ . It is considered that this is because the pulverization property of the obtained gallium oxide is good, and the effect by mixing and pulverization is easy in the sintering operation. The above results are shown in Table 1 in the same manner.

(Example 6)

The liquid metal gallium having a purity of 4 N was charged into the electrolytic cell shown in Fig. 1 in the same manner as in Example 1, and the electrolytic solution was electrolyzed using an aqueous solution of ammonium nitrate. The electrolyte temperature at this time was set to 40 ° C, the pH was set to 5, and the electrolyte concentration was set to 1.0 mol/L.

As other conditions, DSE was used as a material for energizing the anode, Ti was used for the cathode, and the current density was set to 10 A/dm ² .

Thereby, Ga(OH) ₃ crystallized in the solution was obtained. As in Example 1, finely dispersed particles were obtained. Then, the Ga(OH) _{3 was} suction-filtered to carry out solid-liquid separation, and then dried at about 120 ° C to obtain GaO(OH). Then, the dried powder was baked at about 500 ° C for 4 hours to produce a gallium oxide powder.

As a result, the content of chlorine and sodium in the gallium oxide powder is less than the detection limit, that is, less than 10 wtppm. Further, the BET specific surface area was as high as 19.83 m ² /g, and the average particle diameter determined from the particle size distribution was 0.55 μm, which was within the range of the present invention. The crystal of the calcined powder is an α phase (α type).

Further, the obtained gallium oxide powder was used as a raw material for production, and the (111) composition of the IGZO sintered body target was produced, and the density was measured. As a result, the Archimedes density was as high as 6.26 g/cm ³ . It is considered that this is because the pulverization property of the obtained gallium oxide is good, and the effect by mixing and pulverization is easy in the sintering operation. The above results are shown in Table 1 in the same manner.

(Comparative Example 1)

The liquid metal gallium having a purity of 4 N was charged into the electrolytic cell shown in Fig. 1 in the same manner as in Example 1, and the electrolytic solution was electrolyzed using an aqueous solution of ammonium nitrate. Set the electrolyte temperature at this time to 30 ° C, set the pH to 6, and electrolyze. The liquid concentration was set to 4.0 mol/L. This electrolyte concentration is not a condition of this case.

As other conditions, DSE was used as a material for energizing the anode, Ti was used for the cathode, and the current density was set to 10 A/dm ² .

Thereby, Ga(OH) ₃ crystallized in the solution was obtained. An SEM image of the crystallized particles is shown in Fig. 3 . As shown in Fig. 3, aggregated particles were obtained. Then, the Ga(OH) _{3 was} suction-filtered to carry out solid-liquid separation, and then dried at about 120 ° C to obtain GaO(OH). Then, the dried powder was baked at about 1000 ° C for 4 hours to produce a gallium oxide powder.

As a result, the content of chlorine and sodium in the gallium oxide powder is less than the detection limit, that is, less than 10 wtppm. Further, the BET specific surface area was as low as 1.02 m ² /g, and the average particle diameter determined from the particle size distribution was 32.92 μm, which was far beyond the scope of the present invention.

The obtained gallium oxide powder was used as a raw material for production, and the (111) composition of the IGZO sintered body target was produced, and the density was measured. As a result, the Archimedes density was as low as 6.05 g/cm ³ . It is considered that this is because the pulverizability of the obtained gallium oxide is poor, and the effect of mixing and pulverization is insufficient during the sintering operation. The above results are shown in Table 1 in the same manner.

(Comparative Example 2)

The liquid metal gallium having a purity of 4 N was charged into the electrolytic cell shown in Fig. 1 in the same manner as in Example 1, and the electrolytic solution was electrolyzed using an aqueous solution of ammonium nitrate. The electrolyte temperature at this time was set to 30 ° C, the pH was set to 9, and the electrolyte concentration was set to 2.0 mol/L. The pH of this case is not the condition of this case.

As other conditions, DSE was used as a material for energizing the anode, Ti was used for the cathode, and the current density was set to 10 A/dm ² .

Thereby, Ga(OH) ₃ crystallized in the solution was obtained. The crystallized particles were the same as in Comparative Example 1, and aggregated particles were obtained. Then, the Ga(OH) _{3 was} suction-filtered to carry out solid-liquid separation, and then dried at about 120 ° C to obtain GaO(OH). Then, the dried powder was baked at about 1000 ° C for 4 hours to produce a gallium oxide powder.

As a result, the content of chlorine and sodium in the gallium oxide powder is less than the detection limit, that is, less than 10 wtppm. Further, the BET specific surface area was 3.77 m ² /g, and the average particle diameter determined from the particle size distribution was 10.39 μm, which was outside the present invention.

The obtained gallium oxide powder was used as a raw material for production, and the (111) composition of the IGZO sintered body target was produced, and the density was measured. As a result, the Archimedes density was as low as 6.13 g/cm ³ . It is considered that this is because the pulverizability of the obtained gallium oxide is poor, and the effect of mixing and pulverization is insufficient during the sintering operation. The above results are shown in Table 1 in the same manner.

[Industrial availability]

In the present invention, gallium hydroxide produced by the following method is used as a starting material by crystallizing gallium hydroxide by using liquid metal gallium as an anode and electrolyzing in an aqueous solution of ammonium nitrate, by using the powder thereof. The target can be made highly dense, and the present invention has the following excellent effects: it can prevent cracks or poor sintering in the manufacturing step of the target, and can further limit the generation of nodule in sputtering to suppress abnormal discharge. And stable sputtering can be achieved.

The gallium oxide powder produced according to the present invention is particularly suitable for the production of a sputtering target of In-Ga-Zn-O (IGZO) or Ga-Zn-O (GZO), and has high industrial value.

1‧‧‧Anode (Liquid Metal Gallium)

2‧‧‧Metal for energizing the anode

3‧‧‧ cathode

4‧‧‧Insulation

5‧‧‧ electrolyte (aqueous solution of ammonium nitrate)

6‧‧‧Gallium hydroxide

Fig. 1 is a schematic view showing an example of a method for producing gallium hydroxide by electrolysis according to the present invention.

Figure 2 is an SEM image of Ga(OH) ₃ particles crystallized in solution in Example 1.

Fig. 3 is a SEM image of Ga(OH) ₃ particles crystallized in a solution of Comparative Example 1.

1‧‧‧Anode (Liquid Metal Gallium)

2‧‧‧Metal for energizing the anode

3‧‧‧ cathode

4‧‧‧Insulation

5‧‧‧ electrolyte (aqueous solution of ammonium nitrate)

6‧‧‧Gallium hydroxide

Claims (6)

A method for producing gallium hydroxide by using liquid metal gallium as an anode and performing electrolysis in an aqueous solution of ammonium nitrate to crystallize gallium hydroxide. The method for producing gallium hydroxide according to the first aspect of the patent application, wherein the liquid temperature of the electrolyte is set to 30 to 60 ° C, the pH is set to 4 to 7, and the electrolyte concentration is set to 0.5 to 2 mol/L. Perform electrolysis. A method for producing a gallium oxide powder, which comprises drying and calcining gallium hydroxide produced by the first or second aspect of the patent application to prepare a gallium oxide powder. A gallium oxide powder obtained by the manufacturing method of claim 3, wherein the gallium oxide powder has a chlorine content of 10 wtppm or less, a sodium content of 10 wtppm or less, an average particle diameter of 0.5 μm to 3 μm, and a particle size distribution of 0.1 to 10 μm, and a BET specific surface area of 5 to 20 m ² /g. A gallium oxide sintered body obtained by using gallium oxide powder of the fourth aspect of the patent application as a raw material. A gallium oxide sputtering target consisting of a gallium oxide sintered body of claim 5 of the patent application.