JP3173440B2 - Method for producing tin oxide powder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing tin oxide powder for high-density ITO targets.

[0002]

2. Description of the Related Art Tin oxide powder for high-density ITO targets is produced by dissolving metallic tin with nitric acid as a first step in Japanese Patent Application Laid-Open No. Hei 6-199523, "Method for producing tin oxide powder". The deposit (tin hydroxide) is filtered, washed and dried. Next, as a second step, the obtained tin hydroxide is calcined to obtain a tin oxide powder, and this powder and indium oxide are mixed, pressed into a predetermined shape, sintered using a sputtering target. A technique used for forming a thin film by sputtering, tin is used as an anode, an aqueous solution of ammonium nitrate is used as an electrolytic solution to perform tin electrolysis, and the obtained tin hydroxide is calcined to obtain a tin oxide powder. A technique used for forming a thin film in the same manner as described above is described.

[0003]

However, in recent years, the use of high-speed sputtering has been increasingly used, and a stable discharge during this sputtering and the formation of a high-quality ITO film accompanying this are required. -High density is required for the sintered body used for the get.
Therefore, a tin oxide powder as a raw material powder used for forming a sintered body must have characteristics necessary for increasing the density of the sintered body. However, the tin oxide powder obtained by the neutralization method obtained by the above-described conventional technique has irregular particle sizes and a wide particle size distribution, and thus it is difficult to improve the density of the sintered body. Also, in recent years, a method for producing indium oxide for producing a high-quality ITO film has been developed, and accordingly, a tin oxide powder having high characteristics has been required, and the present applicant has filed a patent application No. 9-58978. Application for tin oxide having characteristics, BET specific surface area of primary particles of 2 to 10 m ² / g, crystal particle diameter of 800 ° or more, and particle diameter of secondary particles of 3 to 30
It discloses a tin oxide having a physical property of 50% by weight or more in a range of μm and a method for producing the same, thereby enabling production of a tin oxide having high characteristics. However, as a result of conducting research to obtain more high-quality tin oxide powder at low cost and in a stable manner, it was found that the improvement of the physical properties of the tin oxide powder, the method for producing the same, and the quality of the metallic tin used as the raw material also become problems. did.

[0004]

Means for Solving the Problems Accordingly, the present inventors have
As a result of intensive research and development to solve the above problems, to a heated ammonium nitrate solution, add metal tin powder, add nitric acid to the solution, and precipitate metastannic acid in a strong acid region of pH 2 or less, The tin oxide powder obtained by the method of calcining the precipitated metastannic acid is a powder having sharp characteristics and high characteristics similar to the tin oxide having a large crystallite, which solves the above problem. He gained the knowledge.

[0005] The present invention has been made based on the above findings, and (1) a heated ammonium nitrate solution
Metal tin powder is added, nitric acid is added to the solution to precipitate metastannic acid, and the precipitated metastannic acid is calcined to produce a tin oxide powder, (2) the average particle size of the metal tin is (1) The method for producing tin oxide powder according to (1), wherein the ratio between the peak particle diameter and the average particle diameter of the tin oxide powder is 0.8 to 2.0. (1)
And a method for producing a tin oxide powder according to (2). (4) The method for producing tin oxide powder according to any one of (1) to (3), wherein the formation and precipitation of metastannic acid according to (1) is performed in a strong acid region having a pH of 2 or less.

[0006]

Embodiments of the present invention will be described below. When nitric acid is applied to metal tin, it is directly oxidized to generate Sn + 2HNO ₃ = H ₂ SnO ₃ + NO + NO ₂ metastannic acid (H ₂ SnO ₃ ) by the reaction shown in the following formula. First, a metal tin powder is prepared, and ammonium nitrate (NH ₄ N) is used as a buffer.
An O ₃ ) (1 to 4 mol / l) solution is prepared. After heating the buffer to 50 ° C. or higher, metal tin powder is added and stirred. A predetermined amount of HNO ₃ is slowly added slowly (over 4 hours) to the solution thus prepared. Then, the above reaction proceeds slowly, and gradually white metastannic acid is generated. Due to the presence of the buffer, metastannic acid can be formed with good sedimentation. Next, when metastannic acid is calcined at 500 to 1100 ° C., tin oxide (SnO ₂ ) powder having a uniform particle size distribution is obtained. The obtained SnO ₂ powder has the characteristics that secondary particles are small, the distribution is sharper than before, and the crystallite is large. Using this SnO ₂ powder, a sintered body for a sputtering target is obtained. With this configuration, a high-density sintered body can be obtained, the discharge is stable even in high-speed sputtering, and a high quality film can be obtained.

As the obtained tin oxide powder, the particle size distribution has an effect on the quality of the fluidity of the powder and the density of the sintered body. Is excellent as a powder for a high-performance sintered body for sputtering, and therefore, in the particle size distribution, the peak particle size, which is the particle size indicating the maximum amount of the distribution amount for each particle size, and the distribution for each particle size It is desirable that the total amount is in the range of 0.8 to 2.0 with respect to the arithmetic mean value of the average particle diameter. If the ratio is outside this range, the fluidity of the powder is poor, and The density of the sintered body obtained does not increase so much.

The concentration of the buffer NH ₄ NO ₃ is involved in the formation of metastannic acid. If the value is 1 mol / l or less, the generated metastannic acid has an irregular particle size and coarsens. If it is 4 mol / l or more, it is economically disadvantageous, so its value is desirably 1 mol / l to 4 mol / l.

If the heating temperature of the buffer solution is low, the reaction is slow, and the formed metastannic acid does not age and becomes a powder with poor sedimentation. If the heating temperature is lower than 50 ° C., the reaction does not proceed. The above is desirable, and the upper limit temperature is not particularly limited, but if it is used at 70 ° C. or more, the specifications of the container and the like become severe and uneconomical. Therefore, it is desirable to set the upper limit of the temperature to about 70 ° C. ~ 70 ° C is desirable.

If the particle size of the metal tin used is small, the contact area with the added nitric acid increases, and the reaction proceeds quickly. If the particle size increases, the progress of the reaction slows down, which affects the particle size of the product. The average particle size is 3 mmφ or less, but if the particle size is too small, the cost of metallic tin used for the effect increases, which is uneconomical. Therefore, the lower limit may be determined in consideration of the rate of addition of nitric acid and economy. The rate of addition of nitric acid has an effect of determining the particle size of the finally obtained SnO ₂ powder, but if the value is high, the reaction is fast and the powder particles become too fine, while taking too long time is uneconomical. Therefore, 4 to 10 hours are desirable.

The metastannic acid obtained in the present invention is 500 to 1
By calcining at 100 ° C., tin oxide powder having a uniform particle size distribution can be obtained, but in order to obtain more stable and high quality powder, 850 to 1050 ° C. is desirable.

In the present invention, after the metastannic acid formation reaction,
The liquid property is S by adjusting the pH to a strongly acidic region of 2 or less.
Those other than n remain in the liquid, and impurities can be removed efficiently.
Therefore, it is possible to reduce the purity of the metallic tin used.
Become. For example, 4N SnO _TwoIn order to obtain
4N metal tin had to be used.
Use of 3N metal tin when using the method of Ming
Can be. If the pH is 2 or more, unreacted Sn remains.
With high possibility to distill, preferably at pH 1.5 or less
Range.

[0013]

EXAMPLES Examples of the present invention will be specifically described below. (Example 1) First, 25 g of tin metal having an average particle size of 3 mm was used.
Prepare and mix this with NH ₄ NO ₃ powder: 80 g, H ₂ O: 50
The solution was poured into a NH ₄ NO ₃ solution adjusted to 0 ml, and while maintaining the temperature at 60 ° C., 62 ml of concentrated HNO was stirred and 1.7 ml every 10 minutes from the separating funnel for 4 hours. It was added over time. After that, stirring was continued while maintaining the temperature at 60 ° C. until the precipitate was formed and the cloudy state of the solution was not changed. The time required during this time was 4 hours. Thereafter, the solution was naturally cooled to room temperature, and filtered (1.
0 mv of PTEE), and water filtration and washing 3 times (about 10 times).
0 cc), and the residue was dried at 105 ° C., crushed lightly and then divided into two portions, one of which was 900 ° C., 4 hr. It was calcined to obtain tin oxide powder 1 of the present invention. And the other one
000 ° C., 4 hr. It was calcined to obtain tin oxide powder 2 of the present invention. The pH of the solution during stirring after the addition of nitric acid was 0.5.

(Example 2) 12 g of tin metal having an average particle size of 0.5 mm was put into 500 ml of an NH ₄ NO ₃ solution adjusted to a concentration of 1 mol / l, and while the temperature was maintained at 50 ° C., the concentration was increased. HNO ₃ : 25 ml was added from the separatory funnel every 10 minutes in 0.5 ml portions. Thereafter, stirring was continued while maintaining the temperature at 50 ° C., and the process was continued until a precipitate was formed and the cloudy state of the solution did not change. The time required during this time is 5 hours
Met. Thereafter, the solution was naturally cooled to room temperature, filtered (using 1.0 mv of PTEE), washed with water filtration three times (about 100 cc), and the residue was dried at 105 ° C.
After crushing this lightly, 900 ° C, 4 hr. By firing, a tin oxide powder 3 of the present invention was obtained. The pH of the solution at the time of stirring after the addition of nitric acid was 1.2.

Example 3 The temperature of the NH ₄ NO ₃ solution was set to 80
Except for ° C, metastannic acid was formed under the same conditions as in Example 1, filtered and dried under the same conditions, and calcined at a temperature of 900 ° C for 4 hours to obtain tin oxide powder 4 of the present invention.

(Comparative Example 1) 12 g of tin metal having an average particle size of 3 mm was prepared, and this was 80 g of NH ₄ NO _{3 and} 5 of H ₂ O.
The solution was poured into a NH ₄ NO ₃ solution adjusted to 00 ml, and while maintaining the temperature at 30 ° C., 25 ml of concentrated HNO ₃ was added to the solution and stirred at a rate of 0.8 ml every 10 minutes from a separating funnel. did. After that, stirring was continued while maintaining the temperature at 30 ° C., but it was confirmed that unreacted tin metal remained even after 10 hours.

(Comparative Example 2) 12 g of tin metal having an average particle size of 3 mm was prepared, and this was 80 g of NH ₄ NO _{3 and} 5 of H ₂ O.
The solution was poured into an NH ₄ NO ₃ solution adjusted to 00 ml, and while keeping the temperature at 60 ° C., 25 ml of concentrated HNO ₃ was added thereto, and 0.8 ml was added every 5 minutes from a separating funnel while stirring. did. After that, stirring was continued while maintaining the temperature at 60 ° C. until the precipitate was formed and the cloudy state of the solution was not changed. The required time during this period was 5 hours. Thereafter, the solution was naturally cooled to room temperature, and filtered (1.0 mv PT
EE) and water filtration washing three times (about 100 cc), and the residue was dried at 105 ° C. After crushing this lightly, the temperature was 900 ° C., 4 hr. By calcining, comparative tin oxide powder 2 was obtained.

(Comparative Example 3) 12 g of tin metal having an average particle diameter of 5 mm was prepared, and this was 80 g of NH ₄ NO _{3 and} 5 of H ₂ O.
The solution was poured into the NH ₄ NO ₃ solution adjusted to 00 ml, and while maintaining the temperature at 60 ° C., 25 ml of concentrated HNO ₃ was added thereto, and 0.8 ml was added every 10 minutes from the separating funnel while stirring. did. After that, stirring was continued while maintaining the temperature at 60 ° C. until the precipitate was formed and the cloudy state of the solution was not changed. The required time during this period was 6 hours. Thereafter, the solution was naturally cooled to room temperature, and filtered (1.0 mv PT
EE), and water filtration and washing were performed three times (about 100 cc), and the residue was dried at 105 ° C. After crushing this lightly, the temperature was 900 ° C., 4 hr. By calcining, comparative tin oxide powder 3 was obtained.

(Conventional Example 1) Shot-shaped tin metal is
g of HNO ₃ : 25 ml was added thereto and dissolved.
Meta tin was produced. The deposit (metastannous acid) generated by this dissolution precipitation action was filtered, dried at 105 ° C.
° C, 4 hr. It was calcined to obtain conventional tin oxide powder 1.

(Conventional example 2) Tin electrolysis was performed using tin metal as an anode, an aqueous solution of ammonium nitrate having a concentration of 2 mol / l as an electrolytic solution, a bath temperature of an electrolytic cell at 20 ° C, and a current density of 600 A / m ² . The obtained metastannic acid was dried at 105 ° C, and then dried at 900 ° C for 4 hours. It was calcined to obtain conventional tin oxide powder 2.

Using the tin oxide powders 1, 2, 3 and 4 of the present invention and the conventional tin oxide powders 1 and 2 obtained as described above, the particle size distribution was determined by a laser microtrack method. It was measured. The results are shown in FIGS.

In the tin oxide powder of the present invention, the distribution of the particle size range is relatively narrow, and the distribution is one peak, whereas in the conventional tin oxide powder, the distribution of the particle size is comparatively small. It is spread and has a two-mountain distribution.

Next, the purity of impurities was examined by chemical analysis using the tin oxide powders 1 and 3 of the present invention and the tin oxide powders 1 and 2 of the prior art, and the results shown in the following Table 1 were obtained.

[0024]

[Table 1] Next, using the tin oxide powders 1, 2, 3 and 4, the comparative tin oxide powders 2 and 3, and the conventional tin oxide powders 1 and 2, the peak particle diameter, the average particle diameter, and the specific surface area were measured, respectively. . Table 2 shows the results.

[0025]

[Table 2] As is clear from FIGS. 1 to 6 and Table 2, the tin oxide powders 1, 2, 3 and 4 of the present invention have a sharp particle size distribution as compared with the comparative tin oxide powders 2, 3 and 4 and the conventional tin oxide powder. It can be seen that the variation in particle size is small, the secondary particles are relatively small, the crystallite is large, and the purity is high.

Using the tin oxide powders 1, 2, 3 and 4 of the present invention, 10 g each, an indium oxide powder 9 having a specific surface area of 2.5 m ² / g and an average secondary particle diameter of 10.5 μm
The mixture was mixed into 0 g each, uniformly stirred, put into molds, and formed into a plate under a pressure of 1.5 t / cm ^2.
At a temperature of 600 ° C., a hydrostatic pressure of 500 kg / cm ² was applied for 2 hours and hot press firing was performed to obtain target materials 1, 2, 3, and 4, respectively. As shown in Table 2, the density of this target material sintered body was 99.5 to 9 of the theoretical density.
It was 8.8%.

For comparison, a comparative and conventional target material was obtained in the same manner as described above, using the comparative and conventional tin oxide powders. The density of this target material sintered body was also as shown in Table 2.

A sputtering test was conducted under the following high-speed sputtering conditions using the target material using the tin oxide of the present invention obtained as described above, a comparative target material and a conventional target material. . High-speed sputtering conditions Substrate temperature: 200 ° C. Oxygen partial pressure: 3 × 10 ⁻⁵ Torr As a result, when the sputtering targets 1 to 4 of the present invention were used, the discharge was stable and the formed film was uniform. It was of good quality. (The specific resistance of the obtained film is
As low as 1.7 × 10 ^{over 4} Omega), but on the other hand, comparison and conventional sputtering data - when using the target discharge is sometimes unstable, resulting membranes found in some unevenness of film quality It was hard to recognize it as a good quality film. The specific resistance of the obtained film was about 4.5 × 10 to 2.5 × 10Ω.

[0029]

The tin oxide powder of the present invention has a sharp particle size distribution, a small variation in particle size, relatively small secondary particles, a large crystallite, and a high purity, as compared with the comparative and conventional tin oxide powders. Therefore, when the tin oxide powder of the present invention is mixed with an appropriate indium oxide powder and press-molded, the press density is high.
When the sintered body is used as a target material for high-speed sputtering, a stable discharge can be obtained, and a high-quality ITO sputtering thin film can be obtained, which greatly contributes to a related field.

[Brief description of the drawings]

FIG. 1 shows the particle size distribution of tin oxide powder 1 of the present invention.

FIG. 2 shows the particle size distribution of tin oxide powder 2 of the present invention.

FIG. 3 shows the particle size distribution of the tin oxide powder 3 of the present invention.

FIG. 4 shows the particle size distribution of the tin oxide powder 4 of the present invention.

FIG. 5 shows the particle size distribution of conventional tin oxide powder 1.

FIG. 6 shows the particle size distribution of conventional tin oxide powder 2.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C01G 19/02 C04B 35/00 C23C 14/34

Claims (4)

(57) [Claims] 1. A tin oxide obtained by adding metallic tin to a heated ammonium nitrate solution, adding nitric acid to the solution to precipitate metastannic acid, and calcining the precipitated metastannic acid. Powder manufacturing method. 2. The method for producing tin oxide powder according to claim 1, wherein the average particle size of the metal tin is 3 mm or less. 3. The production of tin oxide powder according to claim 1, wherein the ratio of the peak particle diameter to the average particle diameter of the tin oxide powder is 0.8 to 2.0. Method. 4. The method for producing tin oxide according to claim 1, wherein the precipitation of metastannic acid according to claim 1 is performed in a strongly acidic region.