JP2002020122A - Gallium compound powder, gallium oxide powder and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide gallium compound powder having an isotropic polyhedral form and controlled particle size and to provide gallium oxide powder obtained by calcining the above powder and having controlled particle size and form. SOLUTION: An aqueous solution of a gallium salt is made to react in the presence of sulfate ions and ammonium ions to produce NH4Ga3(SO4)2(OH)6.H2O having an isotropic polyhedral particle form, and then the obtained particles are calcined to produce gallium oxide (Ga2O3) powder which maintains the original particle form.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gallium compound powder and a gallium oxide having a controlled particle shape, which are useful as a raw material for producing a gallium oxide-based material used for optical materials, transparent conductive materials, catalyst supports and the like. The present invention relates to a method for producing a powder.

[0002]

2. Description of the Related Art Normally, gallium oxide is synthesized in a solution into a gallium compound as an intermediate raw material, and the gallium compound is calcined to obtain a desired gallium oxide.

Conventionally, gallium compounds as intermediate materials have been disclosed in JP-B-56-38661 and JP-B-60-383.
Gallium hydroxide and GaOOH are used as in JP-A No. 39 and JP-A-11-263619.

[0004] However, gallium hydroxide produced by the neutralization reaction of gallium salt is an amorphous hydrate like white gelatin, which is difficult to filter and wash after the reaction, and the dried product becomes a solid aggregate. It was difficult to handle.
Gallium oxide obtained by calcining gallium hydroxide has irregular particle sizes and a wide particle size distribution, and thus requires a pulverizing / classifying step. Moreover, although GaOOH can provide dispersed particles, it tends to be columnar particles or plate-like crystals having a large aspect ratio, and it has been difficult to obtain particles having an isotropic shape.

For this reason, conventionally, gallium compounds and gallium oxides have been desired to have particles having a uniform particle size distribution and an isotropic particle shape.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a gallium compound powder having an isotropic polyhedral shape, a controlled particle size, and a particle size and shape that can be obtained by firing the same. It provides a controlled gallium oxide powder.

[0007]

Means for Solving the Problems The present inventors have made intensive studies to solve the above-mentioned problems, and as a result, have found that when an aqueous solution of a gallium salt is allowed to react with a sulfate ion and an ammonium ion in the coexistence, etc. N with anisotropic polyhedral particle shape
It has been found that H ₄ Ga ₃ (SO ₄ ) ₂ (OH) ₆ .H ₂ O is produced, and that the particle size can be arbitrarily controlled by the reaction conditions. Then, this gallium compound is fired and gallium oxide (Ga) is maintained in a state where its particle shape is maintained.
_The present invention was found to be convertible to ₂ O ₃ ) powder and completed the present invention.

Hereinafter, the present invention will be described in detail.

(1) Gallium compound (NH ₄ Ga ₃ (SO
₄ ) ₂ (OH) ₆ .H ₂ O) powder This gallium compound powder can be produced by firing to produce gallium oxide (Ga ₂ O ₃ ) powder, and further mixed with other metal elements to form a gallium composite oxide. Can also be used for the production of

The gallium compound powder has an isotropic polyhedral shape. Here, the isotropic polyhedron is
It shows a polyhedral shape such as a cubic or octahedral shape and isotropic particle shape with relatively good symmetry.

More strictly, the maximum value of the distance from one point to another point on the surface of the powder is defined as the maximum diameter X of the particles. Further, the minimum value of two points at which the perpendicular bisector of the straight line X intersects the powder is defined as the minimum diameter Y. At this time, 1 ≦
A powder satisfying (maximum diameter / minimum diameter = X / Y) ≦ 2 is defined as isotropic.

The gallium compound powder is easily formed into a cubic or octahedral shape, but need not be a complete cubic or octahedral polyhedron. In the present invention, “polyhedral particles” indicate powders in which most of the constituent particles are composed of polyhedrons, and it is not necessary that all the constituent particles have a polyhedral shape.

The particle size of the gallium compound powder ranges from submicron to several tens of microns depending on the application and required characteristics such as reactivity with other substances, sinterability, powder filling property, slurry applicability, and the like. Can be controlled arbitrarily.

Further, since the gallium compound powder is composed of substantially single crystal particles, it is possible to prevent impurities from being mixed into the particles and to obtain a high-purity gallium compound powder. As a result, high-purity gallium oxide (Ga ₂
O ₃ ) powder can be obtained.

Next, a method for producing the gallium compound powder will be described.

A substance containing a sulfate ion and an ammonium ion is added to the gallium salt solution and heated. Generated N
The precipitate of H ₄ Ga ₃ (SO ₄ ) ₂ (OH) ₆ .H ₂ O is filtered off,
After washing with water, the gallium compound (NH ₄ Ga ₃ ) having an isotropic particle shape whose particle diameter is arbitrarily controlled by drying.
(SO ₄ ) ₂ (OH) ₆ .H ₂ O) powder can be obtained. This particle diameter is 0.5 to 30 μm in volume average particle diameter.
Can be arbitrarily controlled within the range of. The particle diameter is determined by the raw material concentration, the raw material supply ratio of gallium / sulfate ion / ammonium ion,
It can be controlled by the reaction temperature and the reaction time.

As the gallium salt, chloride, nitrate, sulfate, acetate and the like are used. The concentration of the solution of the gallium element salt is not particularly limited, but is preferably 0.01 to 1 mol / l to obtain a sharp powder having a small particle size distribution with little aggregation.
Is preferred.

Although various substances can be used as the substance containing sulfate ions, sulfuric acid or ammonium sulfate is used when it is desired to avoid mixing metal ions into the product. In consideration of the yield of the gallium compound, the remaining unreacted sulfate ions in the product, and the like, the amount of sulfate ions is preferably 0.2 mol to 10 mol, more preferably 0.5 mol to 1 mol, per mol of gallium element. 5 moles.

Examples of the substance containing an ammonium ion include:
Although various types are possible, when it is not desirable to mix metal ions into the product, ammonia or ammonium sulfate, ammonium chloride, ammonium nitrate, urea, or the like that evaporates as a gas component by firing is used.

The amount of ammonium ions is preferably 0.2 mol to 10 mol per mol of gallium element in consideration of the yield of the gallium compound, the remaining unreacted ammonium ions, and the like. More preferably, it is 0.5 to 5 mol.

Among them, ammonium sulfate is a preferable raw material because sulfate ion and ammonium ion can be added simultaneously.

Sulfate ions and ammonium ions may be added by mixing them before heating, or may be added after reaching the reaction temperature. The addition may be performed simultaneously or separately. Further, the addition may be carried out by a method of dropping at a constant rate.

The pH of the solution is 1.5 to
It is preferable to adjust the amount of an acid or a base such as ammonia so as to be in the range of 3.

The gallium salt solution is heated to a predetermined temperature to carry out the reaction. The reaction is heated to a temperature not lower than room temperature and not higher than the boiling point, and maintained for 1 hour or longer. More preferably 60 to 90
Hold at ℃ for 1 hour or more.

It is preferable that the pH of the gallium element salt solution in which sulfate ions and ammonium ions coexist is in the range of 1.5 to 3 at the start of the reaction. The start of the reaction means the time when the reaction occurs and the precipitation of gallium compounds (gallium hydroxide, NH ₄ Ga ₃ (SO ₄ ) ₂ (OH) ₆ .H ₂ O, etc.) starts. Within this range, a gallium compound (NH ₄ Ga) having a high monodispersity and a sharp particle size distribution
₃ (SO ₄ ) ₂ (OH) ₆ .H ₂ O) powder is preferable because it can be obtained. The reason is that it is difficult to uniformly nucleate the target gallium compound in the solution, but when the pH of the aqueous solution is in the range of 1.5 to 3, the reaction starts with the formation of amorphous particles having a particle size of about 1 μm or less. Gallium hydroxide containing high-quality sulfate ions is generated, and a target gallium compound is generated from the surface of the particles by heterogeneous nucleation and grows, and gallium compound (NH ₄ Ga ₃ (SO ₄ )) having a uniform particle diameter is obtained. ₂ (O
H) ₆ · H ₂ O) powder is produced. Gallium hydroxide containing amorphous sulfate ions generated at the beginning is re-dissolved when the pH of the solution decreases as the reaction proceeds,
Finally, only a gallium compound powder having a sharp particle size distribution can be obtained.

After completion of the reaction, the resulting precipitate is filtered, washed,
By drying, the desired gallium compound (NH ₄
Ga ₃ (SO ₄ ) ₂ (OH) ₆ .H ₂ O) powder can be obtained. Filtration, washing, and drying can be performed by a known method.

The gallium compound (NH ₄ Ga ₃ (SO ₄ ) ₂ (OH) ₆ .H ₂ O) powder thus prepared has a high crystallinity, a controlled particle size, a sharp particle size distribution, and the like. Since they are anisotropic particles and have high purity, they are very useful as intermediate raw materials for producing a target gallium oxide (Ga ₂ O ₃ ) powder.

(2) Gallium oxide (Ga ₂ O ₃ ) powder Since the above gallium compound powder has high purity, it must be fired at a temperature and for a time sufficient to produce gallium oxide (Ga ₂ O ₃ ) powder. And high-purity gallium oxide (Ga ₂ O ₃ )
A powder can be obtained.

The gallium oxide (Ga ₂ O ₃ ) powder obtained has a polyhedral shape with an isotropic particle shape. Here, the isotropic polyhedron has a polyhedral shape such as a cube or an octahedron, and indicates an isotropic particle shape having relatively good symmetry.

More strictly, the maximum value of the distance from one point to another point on the surface of the powder is defined as the maximum particle diameter X. Further, the minimum value of two points at which the perpendicular bisector of the straight line X intersects the powder is defined as the minimum diameter Y. At this time, 1 ≦
A powder satisfying (maximum diameter / minimum diameter = X / Y) ≦ 2 is defined as isotropic.

The gallium compound powder easily takes a hexahedral or octahedral shape. However, it need not be a perfect cube, octahedron, or other polyhedron. In the present invention, “polyhedral particles” indicate powders in which most of the constituent particles are composed of polyhedrons, and it is not necessary that all the constituent particles have a polyhedral shape.

Next, a method for producing gallium oxide (Ga ₂ O ₃ ) powder will be described.

The gallium compound (NH ₄ G) formed above
By baking the a ₃ (SO ₄ ) ₂ (OH) ₆ .H ₂ O) powder at a temperature of 750 ° C. or higher, NH ₄ , OH, and SO ₄ , which are constituent components of the gallium compound powder, are gasified and evaporated. Therefore, gallium oxide (Ga ₂ O ₃ ) powder is finally produced. If the temperature is lower than 750 ° C., the conversion from the gallium compound powder to the gallium oxide (Ga ₂ O ₃ ) powder does not easily occur, and sulfur tends to remain. In this pyrolysis stage, gallium oxide (Ga ₂ O ₃ ) powder having a high specific surface area is generated, and sintering within the particles proceeds by raising the firing temperature, and gallium oxide (Ga ₂ oxide) having a small specific surface area is obtained. O ₃ ) powder is obtained.

That is, the specific surface area of the gallium oxide (Ga ₂ O ₃ ) powder can be controlled by the sintering temperature.
When the temperature is from 100 to 1000 ° C, the specific surface area is about 100 to 10 m ² / g.
Gallium oxide (Ga ₂ O ₃ ) powder having a relatively large specific surface area can be obtained. When the firing temperature is 1000 ° C. or higher, a dense gallium oxide (Ga ₂ O ₃ ) powder having a small specific surface area of 10 to 1 m ² / g can be obtained.

The gallium oxide (Ga ₂ O ₃ ) powder can control the specific surface area and the pore volume in addition to the particle diameter depending on the use. For example, as a raw material for sintering, dense powder particles having a specific surface area of several m ² / g or less are preferable,
As a catalyst or a separating agent, gallium oxide (Ga ₂ O ₃ ) powder having a specific surface area of several tens m ² / g is preferable.

(3) Gallium composite oxide The above gallium compound (NH ₄ Ga ₃ (SO ₄ ) ₂ (OH)
₆ · H ₂ O) powder or gallium compound (NH ₄ Ga ₃ (S
A gallium composite is obtained by calcining a mixture of gallium oxide (Ga ₂ O ₃ ) powder obtained by calcining O ₄ ) ₂ (OH) ₆ · H ₂ O) powder and an oxide or salt of another metal element. An oxide can be produced.

For example, MgGa ₂ O ₄ , ZnGa ₂ O ₄ , G
It is useful for producing a spinel structure compound such as dGa ₂ O ₄ and a β-Ga ₂ O ₃ structure compound such as InGaO ₃ . The firing temperature depends on the target gallium composite oxide.
It can be obtained by firing at 500 ° C. or less.

[0038]

EXAMPLES The present invention will be described below in more detail with reference to examples, but the present invention is not limited to these examples. The measurement method used in the examples was performed as follows.

(1) Particle Shape The shape of the powder was observed with a scanning electron microscope.

(2) Crystal Structure The crystal phase of the powder was identified using a powder X-ray diffractometer (MPX3 manufactured by Mac Science). Cu as an X-ray source
-Kα radiation was used.

(3) Particle Size Distribution The particle size distribution of the powder was measured by a particle size distribution analyzer (COULTER LS-130 manufactured by Beckman Coulter, Inc.).

(4) Specific Surface Area The specific surface area of the powder was measured with a one-point specific surface area measuring device (MONOSORB manufactured by Yuasa Ionics).

Example 1 <Gallium compound (NH ₄ Ga ₃ (SO ₄ ) ₂ (OH) _6.
Synthesis of H ₂ O) Powder> 750 ml of an aqueous solution of> 0.05 mol / l gallium chloride was placed in a three-necked round bottom flask, and ammonium sulfate was added in an amount twice as large as the number of moles of Ga. PH of solution using 1 mol / l HCl aqueous solution
Was adjusted to 2.4. The temperature was raised from room temperature to 70 ° C. while stirring the solution with a stirring blade at 200 rpm. When the temperature reaches 70 ° C., cloudiness due to formation of a gallium compound starts. The solution at this time was pH = 2.1.
After holding at 70 ° C. for 6 hours, stirring was stopped and the mixture was allowed to cool to room temperature. The solution at this time had a pH of 1.4. Next, the precipitate was separated by suction filtration. This precipitate is distilled water 2
After redispersing in 00 ml, the precipitate was separated by suction filtration. The precipitate was dried in a dryer at 60 ° C. for 12 hours to obtain 3.8 g of the intended gallium compound powder.

The gallium compound powder produced was evaluated as follows.

FIG. 1 shows the result of X-ray diffraction of the gallium compound powder. NH ₄ Ga ₃ (SO ₄ ) ₂ (OH) ₆ .H ₂ O
Was confirmed. The specific surface area was 0.4 m ² / g. FIG. 2 shows an SEM image of the gallium compound powder. The shape was close to a cube, and it was confirmed that the particles had an isotropic particle shape. FIG. 3 shows the results of the particle size distribution of the gallium compound powder. It exhibited a relatively sharp particle size distribution with a volume average particle size of 9.5 μm.

Example 2 <Gallium compound (NH ₄ Ga ₃ (SO ₄ ) ₂ (OH) _6.
Synthesis of H ₂ O) Powder> A 750 ml aqueous solution of> 0.01 mol / l gallium sulfate was placed in a three-necked round bottom flask. 1
The pH of the solution was adjusted to 2.0 with an aqueous HCl / mol solution.
Was adjusted. The temperature was raised from room temperature to 80 ° C. while stirring the solution with a stirring blade at 200 rpm. Then 1
Aqueous ammonia at mol / l was gradually added dropwise until cloudiness due to the formation of the gallium compound started. The solution at this time is p
H = 2.3. After maintaining at 80 ° C. × 20 hours, stirring was stopped and the mixture was allowed to cool to room temperature. The solution at this time is pH =
1.6. Next, the precipitate was separated by suction filtration. This precipitate was redispersed in 200 ml of distilled water, and then filtered by suction to separate the precipitate. This precipitate is
Drying was performed in a dryer at 12 ° C. for 12 hours to obtain 1.5 g of the target gallium compound powder.

The gallium compound powder produced was evaluated as follows.

FIG. 1 shows the result of X-ray diffraction of the gallium compound powder. NH ₄ Ga ₃ (SO ₄ ) ₂ (OH) ₆ .H ₂ O
Was confirmed. The specific surface area was 0.8 m ² / g. FIG. 4 shows an SEM image of the gallium compound powder. The shape was close to a cube, and it was confirmed that the particles had an isotropic particle shape. In addition, the particle size distribution indicates that the average particle size is 1.
At 8 μm, a relatively sharp particle size distribution was exhibited.

Example 3 <Synthesis of Gallium Oxide (Ga ₂ O ₃ ) Powder>
750 ml of a 1 / l gallium nitrate aqueous solution was placed in a three-necked round bottom flask, and ammonium sulfate was added in an amount twice as large as the number of moles of Ga. The pH of the solution was adjusted to 2.5 using a 1 mol / l aqueous HCl solution. The solution was heated from room temperature to 80 ° C. without stirring. When the temperature reaches 80 ° C., white turbidity starts due to the formation of a gallium compound.
After holding at 80 ° C. × 24 hours, the mixture was allowed to cool to room temperature. The solution at this time was pH = 1.5. Next, the precipitate was separated by suction filtration. 200 ml of distilled water
After redispersion in the solution, suction filtration was performed to separate a precipitate.
The precipitate is dried in a dryer at 60 ° C. for 12 hours,
4.5 g of the desired gallium compound powder was obtained.

The resulting gallium compound powder had a volume average particle size of 25.1 μm.

2 g of the obtained gallium compound powder was weighed and placed in an alumina crucible. The crucible was set in a box-type electric furnace and fired at 750 ° C. for 2 hours to obtain gallium oxide (Ga ₂ O ₃ ) powder.

FIG. 5 shows the result of X-ray diffraction of gallium oxide (Ga ₂ O ₃ ) powder. It was a Ga ₂ O ₃ crystal phase which was almost amorphous. Table 1 shows the specific surface area of the gallium oxide (Ga ₂ O ₃ ) powder. The specific surface area was 82 m ² / g, and a porous gallium oxide (Ga ₂ O ₃ ) powder was obtained. FIG.
₂ shows an SEM photograph of the obtained gallium oxide (Ga ₂ O ₃ ) powder. The shape was close to a cube, and it was confirmed that the particles had an isotropic particle shape.

[0053]

[Table 1]

Example 4 <Synthesis of Gallium Oxide (Ga ₂ O ₃ ) Powder> A gallium compound powder obtained in the same manner as in Example 1 was prepared at 1000 ° C. ×
By baking for 2 hours, gallium oxide (Ga ₂ O ₃ ) powder was obtained.

FIG. 5 shows the result of X-ray diffraction of gallium oxide (Ga ₂ O ₃ ) powder. The resulting gallium oxide (Ga
₂ O ₃ ) powder was confirmed to be a single phase of β-Ga ₂ O ₃ phase. Table 1 shows the specific surface area of the gallium oxide (Ga ₂ O ₃ ) powder. The specific surface area was 9 m ² / g. FIG. 3 shows the results of the particle size distribution of gallium oxide (Ga ₂ O ₃ ) powder. It exhibited a relatively sharp particle size distribution with a volume average particle size of 6.2 μm. It was confirmed by SEM observation that the particles had an isotropic particle shape close to a cube.

Example 5 <Synthesis of gallium oxide (Ga ₂ O ₃ ) powder> A gallium compound powder obtained in the same manner as in Example 1 was prepared at 1200 ° C. ×
By baking for 2 hours, gallium oxide (Ga ₂ O ₃ ) powder was obtained.

FIG. 5 shows the result of X-ray diffraction of gallium oxide (Ga ₂ O ₃ ) powder. The resulting gallium oxide (Ga
₂ O ₃ ) powder was confirmed to be a single phase of β-Ga ₂ O ₃ phase. Also, the diffraction peak became sharper than that of the sintering at 1000 ° C. in Example 4. Table 1 shows that gallium oxide (Ga
The specific surface area of ₂ O ₃ ) powder was shown. Specific surface area is 1m ² / g
Met. It was confirmed by SEM observation that the particles had an isotropic particle shape close to a cube.

Comparative Example 1 <Synthesis of Gallium Hydroxide Compound (Ga (OH) ₃ )>
200 ml of a 0.2 mol / l gallium chloride aqueous solution was placed in a beaker, and 1 mol of the solution was stirred while stirring the solution.
/ L of 100 ml of aqueous ammonia was added dropwise. The solution became cloudy and the formation of gallium hydroxide was confirmed. The solution at this time is p
H = 4.0. Next, the precipitate was separated by suction filtration, and this precipitate was dried in a drier at 60 ° C. for 12 hours to obtain the desired gallium hydroxide compound (Ga (O
H) ₃ ) was obtained.

The gallium hydroxide compound (Ga (O (O
H) ₃ ) was strongly agglomerated in blocks, did not retain its shape, and was indefinite.

Comparative Example 2 <Synthesis of Gallium Compound (GaOOH)> 0.05 mol
200 ml of a 1 / l aqueous solution of gallium chloride was placed in a three-necked round bottom flask, and urea was added in an amount 8 times the number of moles of Ga. The temperature was raised from room temperature to 90 ° C. while stirring the solution at 200 rpm with a stirring blade. 90 ° C ×
After holding for 12 hours, stirring was stopped and the mixture was allowed to cool to room temperature.
At this time, the solution had a pH of 8.35. Next, the precipitate was separated by suction filtration, and the precipitate was separated from 200 ml of distilled water.
After re-dispersing in ml, suction filtration was performed to separate a precipitate. This precipitate was dried in a dryer at 60 ° C. for 12 hours to obtain 0.92 g of a gallium compound (GaOOH).

The gallium compound (GaOOH) powder produced was evaluated as follows. As a result of X-ray diffraction, a GaOOH single phase was confirmed. FIG. 7 shows an SEM image of the obtained gallium compound (GaOOH). This shape was columnar, and it was confirmed that the particles were large in aspect ratio.

[0062]

According to the present invention, any gallium compound powder having an isotropic shape can be easily controlled, and the gallium compound powder having an isotropic shape can be easily provided. Gallium oxide (Ga) with controlled particle size and shape
It is useful because ₂ O ₃ ) powder can be easily produced.

[Brief description of the drawings]

FIG. 1 shows the results of X-ray diffraction of the gallium compound powders obtained in Examples 1 and 2.

FIG. 2 shows the SE of the gallium compound powder obtained in Example 1.
It shows an M photograph.

FIG. 3 shows the particle size distribution of the gallium compound powders obtained in Examples 1 and 4.

FIG. 4 shows the SE of the gallium compound powder obtained in Example 2.
It shows an M photograph.

FIG. 5 shows the results of X-ray diffraction of the gallium oxide (Ga ₂ O ₃ ) powders obtained in Examples 3, 4 and 5.

FIG. 6 shows gallium oxide (Ga ₂ O ₃ ) obtained in Example 3.
3 shows an SEM photograph of the powder.

FIG. 7 shows SE of the gallium compound powder obtained in Comparative Example 2.
It shows an M photograph.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tsutomu Takahata 1-4-5 Akanedai, Aoba-ku, Yokohama-shi, Kanagawa F-term (reference) 4G069 AA01 BB05A BB05B BB10A BB10B BC17A BC17B BD01A BD01B BD06A BD06B DA05 EA01X EA01Y FB30

Claims (5)

[Claims] 1. A particle shape, gallium compounds, characterized in that the isotropic polyhedral shape _{(NH 4 Ga 3 (SO 4} ) 2
(OH) ₆ .H ₂ O) powder. 2. The gallium compound (NH ₄ Ga ₃ ) according to claim 1, wherein a sulfuric acid ion and an ammonium ion coexist in an aqueous solution of a gallium salt to cause a heating reaction.
A method for producing (SO ₄ ) ₂ (OH) ₆ .H ₂ O) powder. 3. The pH of a gallium aqueous solution in which sulfate ions and ammonium ions coexist at the start of the reaction is 1.5 to 3
3. The method according to claim 1, wherein
3. The method for producing a gallium compound powder according to item 1. 4. A gallium oxide (Ga ₂ O ₃ ) powder obtained by firing the gallium compound powder according to any one of claims 1 to 3. 5. The gallium oxide (Ga) according to claim 4,
₂ O ₃ ) Method for producing powder.