JP3289335B2 - Method for producing indium oxide powder and ITO sintered body - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an indium oxide powder and an ITO sintered body using the same. IT
The O sintered body is mainly used as an ITO target, and is widely known as a transparent conductive film forming material.

[0002]

2. Description of the Related Art In recent years, as a transparent conductive film used for a solar cell, a transparent electrode of a liquid crystal display, a touch panel, and the like, I.
The demand for TO thin films is increasing. Examples of a method for forming such an ITO thin film include a method of applying ITO fine particles to a substrate, a method of sputtering an IT alloy target or an ITO sintered body target, and a method of forming an ITO film on a substrate surface by a vacuum evaporation method. However, at present, the sputtering method of the ITO sintered body is generally used because a high-performance film can be obtained.

When performing sputtering film formation industrially,
It is preferable that the sputtering operability is excellent, and improvements such as an increase in sputtering rate, prevention of generation of black nodules generated on the target surface, and prevention of cracks due to thermal shock and the like are desired.

[0004] In recent years, with the demand for higher performance of ITO transparent conductive films, development of a technique for forming low-resistance ITO transparent conductive films on low-temperature substrates has been eagerly desired. For example,
The necessity of forming a low-resistance transparent conductive film on a substrate at a lower temperature has been increasing with the colorization of liquid crystal, the miniaturization of display elements, the adoption of an active matrix system, and the introduction of TFTs and MIMs.

Heretofore, it has been known that when the density of an ITO target is increased, the operability of the above-described sputtering and the low-temperature film forming characteristics are improved.

[0006] Usually, an ITO sintered body is manufactured by press-molding a mixed powder of an indium oxide powder and a tin oxide powder (ITO powder) and then sintering it. With indium oxide alone,
Sintered from around 1000 ° C and relatively easy to sinter,
In the case of ITO powder, tin oxide, which is difficult to sinter, becomes a sintering inhibitor and hardly sinters, and it is very difficult to obtain a high-density sintered body by a general normal pressure sintering method.

So far, indium oxide powder has been calcined,
A method in which indium oxide having an average particle diameter of 3 to 6 μm is used by mixing it with tin oxide (see, for example, JP-A-62-2
1751) and a method of using a coprecipitated ITO powder as a raw material for a sintered body (for example, Japanese Patent Application Laid-Open No. 62-12009) has been proposed, but the theoretical density (7.15 g / cm ³ ) has been proposed.
Of about 70% (5 g / cm ³ ), which is not sufficiently high.

On the other hand, some special sintering methods other than the normal pressure sintering method have been proposed, but they are not always satisfactory. For example, a hot press method (for example, see JP-A-56-5)
No. 4702) does not exhibit the expected sputtering characteristics because the surface portion of the target is reduced, and further has high manufacturing costs and poor economic efficiency. Also, a method of manufacturing a high-density ITO target at a high temperature by an oxygen pressure sintering method has been proposed (for example, Japanese Patent Application Laid-Open No. 3-207858), but the equipment cost is high and a high temperature of 1600 ° C. or higher. Due to sintering, the sintered body tends to undergo abnormal grain growth, which may cause a problem in thermal shock resistance of the target.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to propose a fine and highly dispersed indium oxide powder, and 6.0 g / cm ³ obtained by normal pressure sintering by using this powder. The present invention proposes a method for manufacturing a high-density ITO sintered body.

[0010]

Means for Solving the Problems The present inventors have conducted intensive studies on indium oxide powder when producing an ITO sintered body by normal pressure sintering, and as a result, the density of the ITO sintered body was found to be lower than that of indium oxide. They have found that they depend on physical properties, and have completed the present invention.

That is, according to the present invention, the BET surface area is 15 m
² / g or more and 30 m ² / g or less, a ratio of BET diameter to crystallite diameter of 2 or less, indium oxide powder having an average primary particle diameter of 0.1 μm or less, determined by particle size distribution measurement; Mix tin oxide powder with indium oxide powder,
Molding and sintering, characterized by a sintering density of 6.0 g /
The present invention relates to a method for producing an ITO sintered body having a size of cm ³ or more.

Hereinafter, the present invention will be described in detail.

In order to obtain a high-density ITO sintered body by normal pressure sintering, the raw material indium oxide powder needs to have fine and highly dispersed particle characteristics.

The indium oxide powder of the present invention needs to have a BET surface area of 15 m ² / g or more and 30 m ² / g or less. If the BET surface area is less than 15 m ² / g, the particles are agglomerated and a high-density ITO sintered body cannot be provided. In addition, particles having a particle size of more than 30 m ² / g are such that the primary particles are porous or the particles are too fine, so that it is difficult to provide a high-density sintered body.

The indium oxide powder of the present invention needs to have a ratio of BET diameter to crystallite diameter (BET diameter / crystallite diameter) of 2 or less. In particular, 1.5 or less is preferable. BE
The lower limit of the ratio between the T diameter and the crystallite diameter is about 1. At this time, the primary particles can be considered to be in a state close to a single crystal. The crystallite diameter is preferably in the range of 200 to 600 angstroms, and the BET diameter is preferably in the range of 300 to 1000 angstroms. When the ratio between the BET diameter and the crystallite diameter exceeds 2, the state of aggregation of the primary particles is strong, and the sintering activity is reduced.
It becomes difficult to provide a high-density sintered body.

The size of the crystallite diameter can be determined from the half value width of the (222) diffraction peak by XRD measurement of indium oxide. The BET diameter is the BE of the powder.
This is a value obtained by measuring the T value and approximating the particle to a sphere.

The indium oxide powder of the present invention has an average primary particle diameter of 0.1 μm as determined by particle size distribution measurement.
m. When the average particle diameter of the primary particles exceeds 0.1 μm, the primary particles are aggregated, and it is difficult to provide a high-density sintered body.

The average particle size of the primary particles by the particle size distribution measurement is determined as follows. That is, the particles are sufficiently dispersed in an aqueous solution (for example, a small amount of a dispersant is added and ultrasonically dispersed for 1 hour or more), and the average particle size is determined by measuring the particle size distribution of 0.12 μm or less. The average particle size of the secondary particles can also be determined by measuring the particle size distribution subjected to the same dispersion treatment, but the average particle size is fine particles of 0.5 μm or less.

Next, a preferred embodiment for providing the indium oxide powder of the present invention will be described. The indium oxide powder is obtained by mixing an aqueous solution of indium salt and an alkali solution to adjust the pH of the solution to 7 or more, and then calcining the needle-like indium hydroxide obtained by aging, filtering and drying. be able to.

As the indium salt aqueous solution, for example, an indium nitrate solution or an indium sulfate solution can be used. As the alkaline solution, an aqueous solution such as aqueous ammonia or sodium hydroxide can be used. For example, 0.0
Ammonia water can be added to a 1 to 2 mol / L indium nitrate solution to precipitate indium hydroxide particles at a pH of 7 or more.

The reaction temperature is not particularly limited, but generally it can be carried out in the range of room temperature to 90 ° C. Stirring is generally used to carry out a homogeneous reaction.

In order to improve the uniformity and dispersibility of the obtained indium hydroxide slurry, it is necessary to add an aging operation. Aging means maintaining the slurry in the reaction system. The conditions at the time of aging are not particularly limited, but it is preferable to hold the mixture at a temperature of 70 ° C. or higher for several hours or more while stirring. By aging, indium hydroxide fine particles in an insufficiently reacted state disappear, and needle-like fine particles having good dispersibility can be obtained, which serves as a precursor for providing fine and highly dispersed indium oxide powder.

The aged indium hydroxide slurry is dried after solid-liquid separation. The drying temperature is 90-260 ° C
It can be carried out within the range. The dried cake is lightly crushed before calcining.

The crushed indium hydroxide powder is calcined to obtain indium oxide powder. The calcination temperature is 600 ~
1,050 ° C, especially 650-950 ° C, is preferred. If the drying temperature is too low, the primary particles are in a porous state, for example, BET
If the surface area is 30 m ² or more, or if the calcination temperature is too high, the BET surface area will be less than 15 m ² ,
In some cases, the indium oxide powder of the present invention cannot be provided.

The present invention provides a method for producing an ITO sintered body having a density of 6.0 g / cm ³ or more, more preferably 6.4 g / cm ³ (relative density of 90% or more). That is, the tin oxide powder is mixed with the fine and highly dispersed indium oxide powder disclosed in the present invention, molded, and sintered to obtain a density of 6.0 g / cm ³ or more, more preferably 6.4 g / cm ^3. cm ^{3 of} an ITO sintered body can be obtained.

As the tin oxide powder to be mixed, for example, B
An ET specific surface area of 3 to ²⁰ m ² / g is used. The mixing amount of tin oxide is preferably 3 to 15% by weight.

Next, the ITO powder is molded. As a molding method, it is only necessary to select a molding method that matches the intended shape,
Examples include a die molding method and a casting method, but are not particularly limited.

In order to increase the density of the sintered body, it is preferable that the molded body is subjected to a pressure treatment by a cold isostatic press (CIP). If necessary, the CIP process may be repeated about 2 to 5 times.

The sintering temperature of the molded product is 1250 ° C. or more and 160
The temperature is particularly preferably 0 ° C or lower and 1350 ° C or higher and 1550 ° C or lower. When the sintering temperature is less than 1250 ° C., a sintered body having a density of less than 6.0 g / cm ³ is obtained,
If the sintering temperature exceeds 1600 ° C., evaporation of the tin component and abnormal growth of the sintered particle diameter may occur, and stable production may be difficult. The sintering time is preferably several hours to several tens of hours, and the sintering atmosphere is not particularly limited and may be sufficient in the air, but may be any conditions such as oxygen, vacuum, or inert gas.

The ITO sintered body obtained according to the present invention has the following characteristics. The sintered particle size of the sintered body is 1 μm or more and 20 μm or less, and the specific resistance of the sintered body is 7.0 × 10
⁻⁴ Ωcm or less. The transverse rupture strength can achieve 10 kg / mm ² or more. When such a sintered body is used as a sputtering target material, the film formation rate is high, stable discharge is possible during sputter film formation, and the generation of black nodules generated on the target surface is suppressed. Excellent in low-temperature film forming characteristics.

[0031]

The indium oxide powder of the present invention is a fine and highly dispersed powder. By using the indium oxide powder, a high-density ITO sintered body can be manufactured by normal pressure sintering.

When this ITO sintered body is used as a sputtering target material, it has excellent sputtering characteristics, and its industrial value is extremely high.

[0033]

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 An indium nitrate solution having an indium ion concentration of 0.5 mol / L was prepared, and the mixture was stirred at a temperature of 85.degree.
l. % Aqueous ammonia was added for about 30 minutes to precipitate an indium hydroxide slurry, and the pH was adjusted to 8. Thereafter, the slurry was aged at the same temperature and stirring conditions for 10 hours. After filtering and washing the aged indium hydroxide,
Dried at 110 ° C. 700 ° C. of this indium hydroxide
For 4 hours to obtain indium oxide powder. The obtained indium oxide powder had a BET surface area of 25 m ² / g and a BET surface area of 25 m ² / g.
The ET diameter was 330 Å and the crystallite diameter was 270 Å. The ratio of the BET diameter to the crystallite diameter was about 1.2, and the primary particles were 0.08 μm.

The indium oxide powder and the tin oxide powder were mixed (tin oxide: 10 wt%), press-molded by a die press, and further subjected to CIP (2 t / cm ² ) treatment. Sintered. The sintered body had a diameter of 80φ, and the sintered density was 6.8 g / cm ³ (95%).

Using this sintered body as a target material,
A sputtering test was performed under the conditions shown in Table 1.

[0037]

The specific resistance of the obtained film is as follows.
1.8 × 10 ⁻⁴ Ω at 200 ° C., 120 ° C.
cm, 2.2 × 10 ⁻⁴ Ωcm, 2.4 × 10 ⁻⁴ Ωc
m.

Example 2 Indium oxide powder having a BET surface area of 15 m ² / g, a BET diameter of 560 Å, a crystallite diameter of 380 Å, a ratio of crystallite diameter to BET diameter of about 1.5, and primary particles of 0.09 μm was prepared. In the same manner as in Example 1, tin oxide powder was mixed, molded using a slip casting method, and then sintered at 1400 ° C. The sintered density of the obtained ITO sintered body was 6.4 g / cm ³ (90%).

Example 3 The BET surface area was 20 m ² / g, the BET diameter was 420 Å, the crystallite diameter was 300 Å, the ratio of the crystallite diameter to the BET diameter was 1.4, and the particle size distribution of the primary particles was 0.0.
Indium oxide powder of 7 μm and tin oxide powder were mixed (tin oxide: 5 wt%). The prepared ITO powder is press-molded by a mold press, and then CIP (5 t / c).
m ² ) After the treatment, sintering was performed at 1500 ° C. in an atmospheric pressure atmosphere. The sintered body has a diameter of 80φ, and the sintered density is 7.0 g /
cm ³ (98%).

Comparative Example 1 An indium hydroxide slurry was prepared in the same manner as in Example 1.
An indium oxide powder was prepared in the same manner as in Example 1 without aging. The obtained indium oxide powder,
The BET surface area was 13 m ² / g, the BET diameter was 640 Å, the crystallite diameter was 360 Å, the ratio between the BET diameter and the crystallite diameter was 1.8, and the primary particles were 1.0 μm. When the obtained indium oxide powder was sintered by the same operation as in Example 1, the sintered density was 5.8 g / cm.
³ (81%).

Using this sintered body as a target material, sputtering was performed under the same conditions as in Example 1.

The specific resistance of the obtained film is as follows.
2.0 × 10 ⁻⁴ Ω at 200 ° C., 120 ° C.
cm, 2.7 × 10 ⁻⁴ Ωcm, 3.8 × 10 ⁻⁴ Ωc
m.

Comparative Example 2 Indium oxide powder having a BET surface area of 40 m ² / g, a BET diameter of 210 Å, a crystallite diameter of 200 Å, a ratio of crystallite diameter to BET diameter of about 1, and primary particles of 0.09 μm; Tin oxide powder was mixed (tin oxide: 10 wt%). The prepared ITO powder was press-molded by a mold press, further subjected to CIP (5 t / cm ² ) treatment, and then sintered at 1500 ° C. in an atmospheric pressure atmosphere. 8 for sintered body
0φ diameter, and the sintered density is 5.7 g / cm ³ (80
%)Met.

Comparative Example 3 Indium oxide powder having a BET surface area of 10 m ² / g, a BET diameter of 840 Å, a crystallite diameter of 500 Å, a ratio of crystallite diameter to BET diameter of 1.7, and primary particles of 1.0 μm. And tin oxide powder (tin oxide: 10 wt%). The prepared ITO powder was press-molded by a mold press, further subjected to CIP (5 t / cm ² ) treatment, and then sintered at 1500 ° C. in an atmospheric pressure atmosphere. 8 for sintered body
0φ diameter and sintering density of 5.8 g / cm ³ (81
%)Met.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-219315 (JP, A) JP-A-3-207858 (JP, A) JP-A-62-121751 (JP, A) JP-A-56-216 54702 (JP, A) JP-A-62-12009 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C01G 15/00 C04B 35/457 C23C 14/34

Claims (3)

(57) [Claims] (1) a BET surface area of 15 m ² / g or more;
0 m ² / g or less, the ratio of BET diameter to crystallite diameter is 2 or less, and the average particle diameter of primary particles determined by particle size distribution measurement is 0.1 μm.
m or less. 2. An indium salt aqueous solution and an alkaline aqueous solution are mixed, the pH of the mixed solution is adjusted to 7 or more, and then the needle-like indium hydroxide obtained by aging, filtering and drying is calcined. For producing indium oxide powder. ^3. An ITO sintered body having a sintering density of 6.0 g / cm ³ or more, wherein the indium oxide powder according to claim 1 is mixed with a tin oxide powder, molded and sintered. Production method.