JPH1095615A - Indium oxide powder for high density sintered compact - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an indium oxide powder capable of forming a high density sintered compact having a density close to a theoretical value on burning at a high temperature after forming the powder by imparting specific characteristics such as a particle diameter, a particle diameter distribution, a specific surface area and a crystallite diameter to the powder. SOLUTION: This indium oxide powder for a high density sintered compact has characteristics having <=3.0μm mean particle diameter, <=3 fold ratio of the mean particle diameter (Da) to a peak diameter (Dp), (Da/Dp), <=10m<2> /g specific surface area (BET value) and >=900Å crystallite diameter. The indium oxide powder having these particle characteristics can be produced performing an electrolysis by keeping the liquid in a suspended state with an agitation and a liquid temperature of an electrolytic liquid at 50-80 deg.C based on an electrolytic method.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an indium-tin film (ITO).
The present invention relates to indium oxide powder used for a high-density sintered body such as a target material for producing a film.

In recent years, the use of flat displays, mainly liquid crystal displays, has been rapidly expanding, and at present, ITO films are most widely used as the transparent conductive films. As a method of manufacturing an ITO film, a chemical manufacturing method such as a spray method or a coating method, and a physical manufacturing method such as a vacuum evaporation method or a sputtering method are known. In practice, the ITO film is mainly manufactured by a magnetron sputtering method. This method uses I
This is a method of obtaining a film by applying a high voltage to a TO target and causing target material particles to collide with a substrate surface with high energy. An oxide sintered body obtained by mixing and sintering indium oxide and tin oxide as a target material is used. Mainly used.

[0003]

2. Description of the Related Art The indium oxide powder used as a raw material of the above-mentioned ITO film target material is obtained by recovering a precipitate of indium hydroxide produced by neutralizing an indium nitrate solution, drying and roasting. However, conventional indium oxide powder obtained by such a neutralization precipitation method has a non-uniform average particle size and apparent specific gravity, so that a high-density target material can be obtained. There is a problem that there is no.

A method using an indium oxide powder obtained by an electrolytic method in place of such a precipitation method is known (Japanese Patent Application Laid-Open No. Hei 6-191937). In this electrolysis method, the average particle size and apparent density of the indium oxide powder can be controlled by adjusting the electrolysis conditions.
It is stated that an O film can be produced. Specifically, the average particle size is 0.47 to 2.8 μm, and the apparent density is 0.84 to 1.99 g / c.
An m ³ indium oxide powder is illustrated. However, the indium oxide powder obtained by the manufacturing method in the exemplified range has a large variation in particle size and the like, and it is difficult to manufacture a high-density target material.

On the other hand, a method of obtaining a high-density target material by mixing powders having different particle sizes has been proposed (Japanese Patent Laid-Open No. 6-183732). In this method, tin oxide powder having a specific surface area (BET value) of less than 3 m ² / g and a specific surface area (BET value)
A high-density ITO sintered body is manufactured by mixing and using indium oxide powder having an average particle diameter of 15 to ³⁰ m ³ / g, an average particle diameter of 0.03 to 0.1 μ or less, and a crystallite diameter of 200 to 600 °. I have. However, the density of the sintered body exemplified here is 95 to 97% of the theoretical density, which is not yet sufficient. The average particle size and the crystallite size of the indium oxide used are too small, and it is suggested that the particle size control simply based on the average particle size is insufficient.

As described above, after the indium oxide powder obtained by the conventional neutralization precipitation method and the electrolytic method is pressed into a plate (1.5 t / cm ² ), it is further hot-pressed (500 kg / cm ² ).
Looking at the target obtained by sintering at 1600 ° C. for 2 hours while adding m ² ), its density is in the order of 94 to 96% of the theoretical density. Is not enough.

[0007]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problem in the conventional indium oxide powder used as a raw material powder for a target material. An object is to provide an indium oxide powder from which a body can be obtained.

[0008]

That is, the present invention provides (1) a method in which the average particle size is 3.0 μm or less and the ratio of the average particle size to the peak particle size is 3 μm;
And a specific surface area (BET value) of 10 m ² / g or less and a crystallite diameter of 900 ° or more. The indium oxide powder of the present invention preferably has (2) an average particle size of 1.0 to 3.0 μm and a specific surface area (BET value) of 9 m ² / g or less.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to embodiments. The indium oxide powder according to the present invention has a specific surface area.
It is a powder having a (BET value) of 10 m ² / g or less, preferably 9 m ² / g or less. Most of the conventional indium oxide powder used for the ITO sintered body has a specific surface area (BET value) of more than 10 m ² / g. I can't get my body. Specific surface area is 10m ²
If it exceeds / g, the average particle size becomes too small and the bulk density also decreases.

As described above, the indium oxide powder of the present invention has a smaller specific surface area than the conventionally optimized indium oxide powder, and therefore has a slightly larger particle size, but has a particle size distribution within a predetermined range as described later. In addition, the particles have a uniform particle size and are excellent in dispersibility without individual particles being aggregated. Conventionally, powders having a specific surface area (BET value) of less than 15 m ² / g are considered to be undesirable because the particles are agglomerated or have a large primary particle size and are sintering inactive powders. The indium powder is a powder that is suitable for a high-density sintered body by specifying the average particle size, the particle size distribution, and the crystallite size along with the specific surface area.

Further, the indium oxide powder of the present invention has a primary particle having a crystallite diameter of 900 ° or more. The crystallite diameter is a value determined by the X-ray diffraction method. As shown in the test examples described below, in the case where the crystallite diameter is less than 600 to 900 °, the density of the sintered body remains at 94 to 96% of the theoretical density. On the other hand, indium oxide powder having a crystallite diameter of 900 ° or more can provide a high-density sintered body having a theoretical density range substantially in combination with the specific surface area, average particle size and peak particle size conditions specified in the present invention.

The indium oxide powder of the present invention has an average particle size of 3.0 μm or less, preferably 1.0 to 3.0 μm, and has a ratio of the average particle size to the peak particle size of 3 times or less. If the average particle size exceeds 3.0 μm, the particle size is too large to obtain a high density sintered body. On the other hand, if the average particle size is much smaller than 1.0 μm, the bulk density is remarkably reduced, so that a high-density sintered body cannot be obtained.

Further, when the ratio of the average particle size to the peak particle size exceeds 3 times, the uniformity of the particle size is poor, and it is not suitable as a raw material for a high-density sintered body. Here, the peak particle size means the particle size having the largest distribution amount in the particle size distribution. The peak particle size is several μ
The distribution amount of the particle size distribution divided step by step (for example, 1 μm) can be measured and determined based on the particle size having the largest distribution amount. The average particle size is a simple arithmetic average of the whole particles, and does not necessarily indicate the state of the particle size distribution. Therefore, even if the average particle size is the same, the uniformity of the particle size is not the same.
On the other hand, the peak particle size is the particle size with the largest distribution amount,
The closer the peak particle size is to the average particle size, the higher the particle size uniformity. The present invention uses two indices of an average particle size and a peak particle size, and obtains a sintered body having a much higher density by using particles included in a certain range thereof. That is, the ratio (Dp / Da or Da / Dp) of the peak particle diameter (Dp) to the average particle diameter (Da) needs to be 3 times or less. A high-density sintered body equivalent to the density cannot be obtained.

The indium oxide powder having the above-mentioned particle properties can be produced by electrolysis while maintaining the temperature of the electrolytic solution at 50 to 80 ° C. and stirring the solution in a suspended state, based on the electrolysis method. As a method for producing indium oxide powder, metal indium is used as an anode, ammonium nitrate, ammonium sulfate, or ammonium chloride is used as an electrolytic solution, the temperature of the solution is kept at 10 to 50 ° C., electrolysis is performed at pH 4 to 9, and the resulting indium hydroxide is removed. After recovery, an electrolysis method of producing by roasting is conventionally known (JP-A-06-1719).
No. 37). However, the indium oxide of the present invention cannot be obtained only under these conditions. The indium oxide powder of the present invention is obtained by performing electrolysis while stirring the electrolyte in a suspended state at a temperature higher than the liquid temperature in the conventional electrolysis method. Alternatively, those suitable for the above conditions may be selected from the indium oxide powder obtained by the neutralization precipitation method.

[0015]

Examples of the present invention and comparative examples (test examples) are shown below. Examples and Comparative Examples Using metal indium (purity 99.99%) as an anode, ammonium nitrate or ammonium chloride as an electrolyte,
pH 3-9, current density 700A / m ² , electrolyte concentration 1-2mo
l / l, and electrolysis at the liquid temperature and stirring conditions shown in Table 1,
The indium hydroxide precipitate was collected from the bottom of the electrolytic cell, dried and then roasted at 700 to 900 ° C. to obtain an indium oxide powder. Table 1 shows the specific surface area (BET value), crystallite size, average particle size, peak particle size, and bulk density of this indium oxide powder. Using 90 g of the above-mentioned indium oxide powder, 10 g of tin oxide powder having an average particle diameter of 10 μm mixed with the mixture and uniformly stirred, put into a mold, and molded into a plate under a pressure of 1.5 t / cm ² , 500 kg / cm ² at 1600 ° C. for 2 hours
The target material was obtained by performing hot press sintering (hot press sintering) with the application of hydrostatic pressure. Table 1 shows the density of the target material and the density of the green body before firing together with values such as the BET specific surface area of the indium oxide powder.

As a comparative sample, a target material was manufactured in the same manner using indium oxide powder obtained by a neutralization precipitation method. Table 1 shows the density of the target material and the density of the green body before firing together with values such as the BET specific surface area of the indium oxide powder.

As shown in Table 1, the sintered body density of the target material using the indium oxide powder suitable for the conditions of the present invention has reached the theoretical density (7.2 g / cm ³ ) within the range of the measurement error. , A very high density sintered body. When an ITO film was formed using this high-density target material, a nodule causing short-circuit was not generated, and a conductive thin film stable over a long period of time was obtained. On the other hand, in the case of using indium oxide powder outside the scope of the present invention, the density of the sintered body is in the range of 94% to 96% of the theoretical density, and the high density obtained when the indium oxide powder of the present invention is used. It is not possible to produce a sintered body having a high density.

[0018]

[Table 1]

[0019]

The indium oxide powder of the present invention is made of ITO
Ideal as a target material raw material used in film production,
By using this powder, a high-density sintered body having a theoretical density range can be obtained.

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[Procedure amendment]

[Submission date] June 30, 1997

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0018

[Correction method] Change

[Correction contents]

[0018]

[Table 1]

Claims (2)

[Claims] The average particle size is 3.0 μm or less, the ratio of the average particle size to the peak particle size is 3 times or less, and the specific surface area (BET
Value) Indium oxide powder for a high-density sintered body, having an average particle diameter of 10 m ² / g or less and a crystallite diameter of 900 ° or more. 2. The indium oxide powder according to claim 1, having an average particle size of 1.0 to 3.0 μm and a specific surface area (BET value) of 9 m ² / g or less.