JP3254697B2 - Indium oxide powder and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an indium oxide powder and a method for producing the same. More specifically, the present invention relates to a plate-like indium oxide powder having a highly oriented (222) crystal orientation and a method for producing the same.

By using the plate-like indium oxide powder of the present invention as a raw material for a sintered body, it is possible to produce a crystal oriented sintered body. Further, by producing a conductive powder by dissolving tin or the like that gives carrier electrons, the present invention can be applied to a conductive filler or the like.

[0003]

2. Description of the Related Art Functional ceramics (sintered bodies) are manufactured by molding and sintering oxide powder. The characteristics of the sintered body
Often attributed to the properties of the oxide powder used, for example, electrical properties such as conductivity, mechanical properties such as breaking strength, denseness, sintered body properties such as crystal orientation, the shape of the oxide powder used, It changes greatly depending on characteristics such as particle size, dispersibility, and crystal orientation.

For example, a crystallographically oriented sintered body is manufactured by using a crystallographically oriented powder having anisotropic powder shape, aligning the powder during pressure molding, and sintering the molded body with the powder aligned. It is possible.

Conventionally, in the production of indium oxide powder, an indium source such as indium metal is dissolved with an acid such as nitric acid, sulfuric acid or hydrochloric acid, a precipitant such as an alkali is added to form indium hydroxide, and then calcined. Is done in a way. In the thus produced indium oxide powder, the ratio of (222) plane diffraction intensity / (400) plane diffraction intensity in the X-ray diffraction pattern was almost 3, and the powder shape did not have anisotropy. .

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a highly oriented (222) crystallized indium oxide powder and a method for producing it in a simple and easy manner.

[0007]

The present inventors have made intensive studies on the above-mentioned indium oxide powder and the method for producing the same, and as a result, have found that sulfate ion / indium (molar ratio).
After concentrating the aqueous solution of indium sulfuric acid having a value of 1.5 to 10, the plate-like indium sulfate hydroxide obtained by adding excess sulfuric acid is filtered, dried, and calcined,
The ratio of (222) plane diffraction intensity / (400) plane diffraction intensity by X-ray diffraction is 5 or more, and the average particle size is 0.1 μm to 10 μm.
It has been found that a powder of indium oxide having a plate shape of 0 μm can be obtained, and the present invention has been completed.

Hereinafter, the present invention will be described in detail.

The indium oxide powder of the present invention has a ratio of (222) plane diffraction intensity / (400) plane diffraction intensity by X-ray diffraction of 5 or more, has an average particle size of 0.1 μm to 100 μm, and has a plate shape. FIG. (222)
The diffraction of the plane appears around 2Θ = 30 degrees, and the diffraction of the (400) plane appears around 2Θ = 35 degrees.

The diffraction intensity ratio referred to in the present invention means the integrated intensity of the diffraction peak on the (222) plane and the integrated intensity of the diffraction peak on the (400) plane in the X-ray diffraction pattern of indium oxide powder. Is the ratio of

The diffraction intensity ratio of the powder of the present invention is (222)
The ratio of the plane diffraction intensity / (400) plane diffraction intensity is 5 or more, particularly preferably 10 or more. This is larger than the diffraction intensity ratio of 3 of the conventional indium oxide powder,
2) It is a new powder that shows a strong orientation on the surface.

The average particle size of the powder of the present invention is 0.1 μm to 1 μm.
00 μm. When the particle size of the powder is less than 0.1 μm, the powder is not preferable because the powder is agglomerated and the (222) crystal oriented indium oxide powder cannot be obtained. Further, when the powder particle size is 100
A particle size exceeding μm is not preferred because the dispersibility of the powder becomes poor.

Next, a method for producing the indium oxide powder of the present invention will be described.

The indium oxide powder of the present invention may be, for example, an indium sulfate hydroxide ([H ₅ O ₂ ] [In (H ₂ O)
₂ (SO ₄ ) ₂ ]). Indium hydroxide hydroxide containing sulfur forms a layer in the C-axis direction,
A layered compound exhibiting C-axis orientation, especially (002) crystal orientation, and exhibiting a plate-like powder shape. That is, the C-axis-oriented plate-like indium sulfate hydroxide is thermally decomposed to produce indium oxide.
The crystal growth in the in-plane direction is suppressed, and the
2) It is possible to produce a plate-like indium oxide powder rich in the crystal orientation of the plane, and by using the plate-like powder, it is possible to maintain the plate-like shape even after thermal decomposition.

A method for producing the indium sulfate hydroxide-containing powder will be described.

Sulfur-containing indium hydroxide powder is obtained by concentrating an aqueous solution of indium sulfuric acid having a sulfate ion / indium (molar ratio) of 1.5 to 10, adding excess sulfuric acid, filtering and drying. .

The indium sulfate hydroxide containing powder can be produced by concentrating a solution of indium and indium sulfate (Acta Crystallogr.,
Sec. B. , 35, 1580 (1979)). Even if the solution in which the composition of the sulfate ion and the indium in the aqueous solution of indium sulfate was adjusted to the stoichiometric ratio of the indium sulfate hydroxide was concentrated, the indium sulfate hydroxide was crystallized. Takes a lot of time. However, after concentrating the aqueous solution of indium sulfuric acid,
It has been found that when an excessive amount of sulfuric acid is added, indium hydroxide sulfate containing water is crystallized simultaneously with the addition of sulfuric acid, and the crystallization time can be greatly reduced. It is a feature of the present invention that after the aqueous solution of indium sulfuric acid is concentrated, excess sulfuric acid is added.

The method for producing the indium sulfate hydroxide-containing powder will be described in more detail.

The sulfate ion / indium (molar ratio) of the aqueous solution of indium in sulfuric acid is preferably 1.5 to 10, particularly preferably 2 or more and 8 or less. If the ratio of sulfate ion / indium (molar ratio) is smaller than 1.5, indium is not preferable because it is not completely soluble in sulfuric acid. Further, even if the ratio of sulfate ion / indium (molar ratio) exceeds 10 and a large amount of sulfuric acid is present, no effect is exhibited, which is not economically preferable.

The source of indium used for producing the aqueous solution of indium sulfuric acid is not particularly limited as long as it does not contain any negative ions other than sulfate ions in the solution. Indium metal, indium oxide and the like can be used. , Indium hydroxide, indium sulfate and the like are applicable. The source of sulfuric acid can be used without any particular limitation, and indium sulfate, concentrated sulfuric acid and the like may be used.

The production of an aqueous solution of indium sulfuric acid is carried out by mixing the above-mentioned indium source and sulfuric acid source. The mixing method is not particularly limited, and a sulfuric acid source may be added to the indium source, or an indium source may be added to the sulfuric acid source. Further, if necessary, the mixing may be carried out in the presence of distilled water.

The temperature at the time of mixing is not particularly limited and may be at room temperature or the like. In addition, the heating may be performed while heating to accelerate the dissolution of the indium source.

Further, if necessary, mixing may be carried out with stirring. At this time, the stirring speed is not particularly limited.

Next, the indium sulfate aqueous solution is concentrated.
Concentration refers to evaporating the water in the solution. Examples of the concentration method include a method of performing the treatment under reduced pressure using an evaporator, and a method of performing the treatment by heating under normal pressure. Indium hydroxide hydroxide containing sulfuric acid is not preferable because it emits white smoke and decomposes.

To reduce the crystallization time of the indium sulfate hydroxide, after concentration, excess sulfuric acid is added. The amount of sulfuric acid added was 0.1-1 based on the number of moles of indium charged.
The amount is 00 times, particularly preferably 1-10 times. If the amount of sulfuric acid is less than 0.1 times the amount, the effect of shortening the crystallization time of indium sulfate hydroxide is not exhibited. Further, even if sulfuric acid is added in an amount exceeding 100 times the amount, the effect of shortening the crystallization time of indium sulfate hydroxide is saturated, which is not economically preferable.

After the obtained indium sulfate-containing indium hydroxide is separated from excess sulfuric acid, washing may be carried out if necessary. The solvent used for washing may be an organic solvent such as insoluble acetone, ethanol, methanol, dimethyl sulfoxide, etc. since indium sulfate hydroxide is soluble in water.

Next, the powder is dried. The drying temperature is 150 ° C. or lower, particularly preferably 120 ° C. or lower.
Drying at a temperature exceeding 150 ° C. is not preferable because water of crystallization in indium sulfate hydroxide is eliminated and partial decomposition occurs.

The indium hydroxide sulfate-containing powder is obtained by the above-mentioned method. Next, the method for producing the indium oxide powder of the present invention will be described.

The indium oxide powder of the present invention is produced by calcining indium sulfate hydroxide-containing powder. Calcination temperature is 20
0 ° C to 700 ° C, particularly preferably 300 ° C to 600 ° C
Range. If the calcination temperature is lower than 200 ° C., the thermal decomposition of indium sulfate hydroxide is insufficient, and
At a temperature exceeding 0 ° C., crystal growth of indium oxide proceeds, and a powder having a crystal orientation of the powder of the present invention, that is, a powder having a (222) plane diffraction intensity / (400) plane diffraction intensity ratio of 5 or more may not be obtained. is there.

The calcination time is 30 minutes to 10 hours, particularly preferably 1 hour to 5 hours. If the calcination time is less than 30 minutes, the decomposition of indium sulfate hydroxide containing water is insufficient, and even if it is longer than necessary, the particle size of the powder, the crystal orientation, etc. do not change, and it is economically preferable. Absent.

The atmosphere during calcination is not particularly limited, and may be performed in the air or the like.

[0032]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the present invention is limited thereto.

Example 1 9.51 g of indium sulfate nonahydrate was dissolved in 100 ml of distilled water, and 1.49 g of 97% concentrated sulfuric acid was added.
An indium sulfate aqueous solution having an indium molar ratio of 2 was produced. After evaporating the aqueous solution of indium sulfuric acid under reduced pressure using an evaporator, an excessive amount of concentrated sulfuric acid three times the number of moles of indium was added to the solution of indium sulfuric acid. Was analyzed. The obtained crystallized product was filtered and washed with ethanol to obtain a powder of indium sulfate hydroxide.

FIG. 1 shows the powder X-ray diffraction spectrum and the crystal structure of the indium sulfate hydroxide-containing powder.
And FIG.

The indium hydroxide hydroxide containing sulfur obtained by the above method was calcined at 300 ° C. in the air to obtain indium oxide powder.

FIG. 3 shows the powder X-ray diffraction spectrum and the crystal structure of the obtained indium oxide powder, respectively.
And FIG. Powder shape is plate, average particle size is 50μm
A powder having a (222) plane diffraction intensity / (400) plane diffraction intensity ratio of 19 and having a high (222) crystal orientation was obtained.

Example 2 165.8 g of indium hydroxide was added to 300 ml of distilled water and stirred to prepare an indium hydroxide slurry, and 202.1 g of 97% concentrated sulfuric acid was added to the slurry, and sulfuric acid / indium was added. Was obtained at a molar ratio of 2. The obtained aqueous solution was evaporated under reduced pressure in the same manner as in Example 1, and sulfuric acid in an amount twice as much as the mole number of indium was added to crystallize indium sulfate hydroxide. The obtained crystallization product was washed in the same manner as in Example 1 to obtain indium sulfate hydroxide.

The indium hydroxide hydroxide containing sulfur obtained by the above method was calcined at 500 ° C. in the air to obtain indium oxide powder.

FIG. 5 shows the powder X-ray diffraction spectrum of the obtained indium oxide powder. The ratio of (222) plane diffraction intensity / (400) plane diffraction intensity was 5.5, and (222)
A powder having a high crystal orientation was obtained. Average particle size is 70 μm
Met.

Example 3 229.8 g of indium metal was added to 500 g of 97% concentrated sulfuric acid.
To produce an indium sulfuric acid solution having a sulfuric acid / indium molar ratio of 2.5. After evaporating this solution under reduced pressure in the same manner as in Example 1, 10 times the amount of concentrated sulfuric acid with respect to the mole number of indium was added to crystallize indium sulfate hydroxide. The obtained crystallization product was washed in the same manner as in Example 1 to obtain indium sulfate hydroxide.

The indium hydroxide hydroxide containing sulfur obtained by the above method was calcined in the same manner as in Example 2 to obtain an indium oxide powder.

The resulting indium oxide powder (222)
The ratio of plane diffraction intensity / (400) plane diffraction intensity is 5.6,
(222) A powder having a high crystal orientation was obtained. The average particle size was 65 μm.

Comparative Example 1 Commercially available indium sulfate was heated at a temperature of 900 ° C. to obtain indium oxide. FIG. 4 shows the XRD pattern of the obtained powder. The ratio of (222) plane diffraction intensity / (400) plane diffraction intensity was 3.2, which was the same as the crystal orientation ratio of the conventional indium oxide.

[0044]

As described above, the indium oxide powder of the present invention comprises (22)
2) The crystal orientation of the surface is rich, and by using this powder, it is possible to produce a sintered body with controlled crystal orientation.
Further, a conductive powder is produced by dissolving a dopant such as tin in the powder of the present invention, and application to a conductive filler or the like is also possible.

[Brief description of the drawings]

FIG. 1 is a diagram showing a powder X-ray diffraction spectrum of the indium sulfate hydroxide powder obtained in Example 1.

FIG. 2 is a view showing the crystal structure of the indium sulfate hydroxide-containing powder obtained in Example 1.

FIG. 3 is a view showing a powder X-ray diffraction spectrum of the indium oxide powder obtained in Example 1.

FIG. 4 is a view showing a crystal structure of the indium oxide powder obtained in Example 1.

FIG. 5 is a view showing a powder X-ray diffraction spectrum of the indium oxide powder obtained in Example 2.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C01G 15/00 CA (STN)

Claims (2)

(57) [Claims] 1. The (222) plane diffraction intensity by X-ray diffraction /
(400) An indium oxide powder having a plane diffraction intensity ratio of 5 or more, an average particle size of 0.1 μm to 100 μm, and a powder shape of a plate. 2. An indium sulfuric acid aqueous solution having a sulfate ion / indium (molar ratio) of 1.5 to 10 is concentrated, and an excess of sulfuric acid is added to obtain a plate-like indium sulfate-containing indium hydroxide, which is filtered and dried. Then, calcined, characterized by (222) plane diffraction intensity / (400) by X-ray diffraction.
The plane diffraction intensity ratio is 5 or more, and the average particle size is 0.1 μm or more.
A method for producing an indium oxide powder having a plate shape of 100 μm.