A method for preparing an indium oxide / tin hydroxide composite, an ITO target

Abstract

The application provides an indium oxide / tin hydroxide composite and a preparation method of an ITO target material, and belongs to the field of ITO target materials. The application provides a preparation method of an indium oxide / tin hydroxide composite, which comprises the following steps: mixing nano indium oxide, a tin salt solution, an inorganic base containing hydroxyl ions and water to perform a precipitation reaction, and granulating the obtained precipitation reaction product to obtain the indium oxide / tin hydroxide composite; the molar ratio of indium elements in the nano indium oxide to tin elements in the tin salt solution is 20-100:1. The nano indium oxide is directly introduced in the application, so that the operation of a large amount of precipitation is avoided; the trace-doped tin hydroxide is obtained by using the precipitation method, so that the uniform distribution of the tin hydroxide on the surface of the indium oxide can be ensured, the distribution of tin oxide in the ITO target material prepared by the method is uniform, and the density of the ITO target material is improved.

Description

Technical Field

[0001] This invention relates to the field of ITO targets, and more particularly to an indium oxide / tin hydroxide composite and a method for preparing an ITO target. Background Technology

[0002] Indium tin oxide (ITO) is an important optoelectronic thin film material, mainly composed of In₂O₃ and SnO₂. Its conductivity is enhanced by doping tetravalent tin into the indium oxide lattice. Due to its excellent comprehensive properties such as transparency, conductivity, thermal insulation, infrared reflection, and radar wave transmission, ITO thin films have broad application prospects in high-tech fields such as optoelectronics, sensors, solar energy, and broadband stealth.

[0003] In existing technologies, nano-ITO powder is commonly used to prepare ITO targets. There are two main conventional ITO powder preparation processes: one is the co-precipitation process, in which metallic indium and tin are dissolved together in a nitric acid solution, and then indium hydroxide and tin hydroxide are precipitated by adding an alkaline solution. After aging, cleaning, spray granulation, and calcination, nano-ITO powder is finally obtained; the other is the ball milling process, in which nano-indium oxide powder and nano-tin oxide powder are directly mixed by wet ball milling.

[0004] The two processes mentioned above have been widely used for the production of traditional ITO targets (indium oxide / tin oxide = 99 / 1 to 90 / 5 wt%). In particular, the wet ball milling process can easily and quickly obtain nano-ITO powder. However, both processes also have obvious drawbacks, especially for the preparation of trace-doped nano-ITO powder with tin oxide content of 0.1 to 5 wt%.

[0005] Although co-precipitation can produce uniformly distributed nano-ITO powder, its process is complex. While ball milling is widely used on ITO targets with 99 / 1 to 90 / 5 wt%, it is difficult to achieve a uniform distribution of tin oxide and indium oxide in the ITO target for micro-doped ITO targets, which results in low density of the sintered ITO target. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing an indium oxide / tin hydroxide composite and an ITO target. The method for preparing the indium oxide / tin hydroxide composite is simple and the ITO target prepared using the indium oxide / tin hydroxide composite has high density.

[0007] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0008] This invention provides a method for preparing an indium oxide / tin hydroxide composite, comprising the following steps:

[0009] Nano-sized indium oxide, tin salt solution, inorganic alkali containing hydroxide ions and water are mixed to carry out a precipitation reaction, and the resulting precipitation reaction product is granulated to obtain the indium oxide / tin hydroxide composite.

[0010] The molar ratio of indium to tin in the nano-indium oxide solution is 20–100:1.

[0011] Preferably, the hydroxide-containing inorganic base includes ammonia.

[0012] Preferably, the tin salt comprises tin nitrate.

[0013] Preferably, the raw materials used in the mixing process also include binders and / or plasticizers.

[0014] Preferably, the mass of the binder is 0.5% to 1% of the total mass of indium oxide and tin hydroxide in the indium oxide / tin hydroxide composite.

[0015] Preferably, the mass of the plasticizer is 0.1% to 0.5% of the total mass of indium oxide and tin hydroxide in the indium oxide / tin hydroxide composite.

[0016] Preferably, the mixing includes: first mixing nano-indium oxide with water to obtain nano-indium oxide slurry;

[0017] The slurry is mixed with a tin salt solution to obtain a mixed slurry;

[0018] The mixed slurry is then mixed a third time with an inorganic alkali containing hydroxide ions, a binder, and a plasticizer.

[0019] Preferably, the second and third mixing methods include ball milling; during the second and third mixing, the ball milling speed is independently 1500-2500 rpm, the time is independently 0.5-5 h, and the grinding balls are independently 0.2-0.4 mm zirconia balls.

[0020] This invention also provides a method for preparing an ITO target, comprising the following steps:

[0021] The indium oxide / tin hydroxide composite prepared by the preparation method described above is subjected to compression molding and sintering to obtain the ITO target material.

[0022] The sintering temperature is 1400–1600℃.

[0023] Preferably, the compression molding pressure is 150-250 MPa and the time is 2-10 min; the sintering time is 15-35 h.

[0024] This invention provides a method for preparing an indium oxide / tin hydroxide composite, comprising the following steps:

[0025] Nano-indium oxide, tin salt solution, inorganic alkali containing hydroxide ions and water are mixed to carry out a precipitation reaction. The resulting precipitation product is granulated to obtain the indium oxide / tin hydroxide composite. The molar ratio of nano-indium oxide to tin in the tin salt solution is 5-100:1.

[0026] This invention introduces nano-indium oxide directly, avoiding the need for extensive precipitation. The trace amount of doped tin hydroxide is obtained through precipitation, which ensures the uniform distribution of tin hydroxide on the surface of indium oxide. This results in a uniform distribution of tin oxide in the prepared ITO target, thereby improving the density of the ITO target.

[0027] In existing co-precipitation processes, indium and tin are first dissolved in nitric acid, then ammonia is added dropwise to obtain indium hydroxide and tin hydroxide precipitates. After washing, indium hydroxide and tin hydroxide powders are obtained by spray granulation. Because the powders contain a large amount of hydroxide ions, calcination is required before molding and sintering to obtain the ITO target material. If calcination is not performed and molding and sintering are carried out directly, the ceramic will crack as indium hydroxide and tin hydroxide decompose. However, this invention controls the molar ratio of indium in nano-indium oxide to tin in the tin salt solution, resulting in a low tin hydroxide content in the indium oxide / tin hydroxide composite. Therefore, even if tin hydroxide decomposes, calcination will not cause the ITO target material to crack or reduce its density.

[0028] Furthermore, this invention employs ball milling to further improve the uniformity of tin hydroxide distribution on the indium oxide surface. Pure indium oxide is difficult to sinter densely; even at sintering temperatures above 1600°C, it is impossible to prepare a dense ceramic. However, adding tin oxide can lower the sintering temperature and promote the dense sintering of indium oxide ceramics. The uniformity of the mixing of tin oxide powder with tin oxide powder determines the sintering aid strength of tin oxide powder for indium oxide ceramics. Ideally, both powders would be co-precipitated to form uniformly mixed nanoparticles, but this method requires large amounts of acids and alkalis and a specialized calcination process, making it cumbersome and costly. This invention, by using tin hydroxide to precipitate separately, achieves a uniform distribution of tin hydroxide on the indium oxide powder surface, thereby promoting a uniform distribution of tin oxide on the indium oxide powder surface, and further enhancing the sintering strength of the ITO target material.

[0029] Meanwhile, compared with the traditional method of ball milling and mixing indium oxide powder and tin oxide powder, this process significantly improves the mixing uniformity and enhances the sintering activity and sintering density of the ITO target material.

[0030] Furthermore, when the tin salt is tin nitrate and the inorganic alkali containing hydroxide ions is ammonia, the residual nitrate ions and ammonium ions can decompose during the sintering process, thus avoiding any impact on the sintering performance of the ITO target material.

[0031] This invention controls the sintering temperature to enable tin hydroxide to undergo a metathesis reaction during sintering, generating tin oxide, thus avoiding the calcination step of the co-precipitation process in existing technologies. Attached Figure Description

[0032] Figure 1 Metallographic image of nano-ITO powder in Example 1. Detailed Implementation

[0033] This invention provides a method for preparing an indium oxide / tin hydroxide composite, comprising the following steps:

[0034] Nano-sized indium oxide, tin salt solution, inorganic alkali containing hydroxide ions and water are mixed to carry out a precipitation reaction, and the resulting precipitation reaction product is granulated to obtain the indium oxide / tin hydroxide composite.

[0035] The molar ratio of the nano-indium oxide to the tin element in the tin salt solution is 5 to 100:1.

[0036] In this invention, the purity of the nano-indium oxide is preferably higher than 99.99%, and the specific surface area is preferably 7-12 g / m². 2 More preferably 8-10 g / m 2 .

[0037] In this invention, the method for preparing the tin salt solution preferably includes dissolving tin in a strong acid solution. In this invention, the purity of the tin is preferably greater than 99.99%, the concentration of the strong acid solution is preferably 1 mol / L, and the molar ratio of tin to the strong acid solution is preferably 1:2 to 5. In this invention, the tin salt preferably includes tin nitrate. When the tin salt is tin nitrate, the strong acid solution used to prepare the tin salt solution is a nitric acid solution.

[0038] In this invention, the hydroxide-containing inorganic base preferably includes ammonia water, and the concentration of the ammonia water is preferably 1-5 mol / L. This invention does not have a specific limitation on the amount of the hydroxide-containing inorganic base used; the pH value of the mixture obtained by mixing nano-indium oxide, tin salt solution, hydroxide-containing inorganic base, and water can be adjusted to 8-10.

[0039] In this invention, the raw materials used in the mixing process preferably further include a binder and a plasticizer; the mass of the binder is preferably 0.5-1% of the total mass of indium oxide and tin hydroxide in the indium oxide / tin hydroxide composite, more preferably 0.6-0.8%; the binder preferably includes PVA; the mass of the plasticizer is preferably 0.1-0.5% of the total mass of indium oxide and tin hydroxide in the indium oxide / tin hydroxide composite, more preferably 0.2-0.4%; the plasticizer preferably includes PEG. The binder and plasticizer can improve molding strength.

[0040] In this invention, when the raw materials for mixing include binders and / or plasticizers, the mixing preferably includes a first mixing of nano-indium oxide with water to obtain a nano-indium oxide slurry;

[0041] The slurry is mixed with a tin salt solution to obtain a mixed slurry;

[0042] The mixed slurry is then mixed a third time with an inorganic alkali containing hydroxide ions, a binder, and a plasticizer.

[0043] In this invention, the solid content of the slurry is preferably 30-60 wt%, more preferably 40-55 wt%, and even more preferably 45-50 wt%.

[0044] In this invention, the second and third mixing methods preferably include ball milling; during the second and third mixing, the ball milling speed is independently 1500-2500 rpm, the time is independently 3-5 h, and the grinding balls are independently 0.2-0.4 mm zirconia balls.

[0045] This invention also provides a method for preparing an ITO target, comprising the following steps:

[0046] The indium oxide / tin hydroxide composite prepared by the above method is molded and sintered to obtain the ITO target.

[0047] In this invention, the compression molding pressure is preferably 150-250 MPa, more preferably 180-200 MPa, and the time is preferably 2-10 min, more preferably 4-8 min, and even more preferably 5-6 min;

[0048] In this invention, the raw materials used in the mixing process also include binders and / or plasticizers, and preferably, after the compression molding, degumming is also performed. During the degumming process, the binders and plasticizers are discharged due to decomposition.

[0049] In this invention, the sintering temperature is preferably 1400-1600℃, more preferably 1450-1500℃; the sintering time is preferably 15-35h, more preferably 20-30h, and even more preferably 24-28h.

[0050] The following detailed description, in conjunction with embodiments, illustrates the preparation methods of the indium oxide / tin hydroxide composite and ITO target provided by the present invention. However, these descriptions should not be construed as limiting the scope of protection of the present invention.

[0051] Example 1

[0052] A specific surface area of ​​990g is 9.5m². 2 / g of nano-indium oxide powder was mixed with pure water to prepare nano-indium oxide slurry with a solid content of 45%.

[0053] Add 7.8g of 99.993% pure metallic tin to 200mL of 1mol / L dilute nitric acid to dissolve it, and a tin salt solution is obtained;

[0054] 200 mL of tin nitrate solution was mixed with nano-indium oxide slurry. The mixing was carried out in a sand mill at 1800 rpm with 0.3 mm zirconia balls for 4 h. Then, 1.5 mol / L ammonia water was added to the resulting slurry to adjust the pH to 8.9. Then, 0.8% of the total mass of indium oxide and tin hydroxide in the mixture was added as binder PVA and 0.4% of the total mass of indium oxide and tin hydroxide in the mixture as plasticizer PEG. The mixture was then sand-milled for another 40 min.

[0055] The slurry after sand milling was spray-granulated at 150°C to obtain nano-indium oxide / tin hydroxide composite.

[0056] The obtained indium oxide / tin hydroxide composite was formed into a preform under a pressure of 200 MPa, and after debinding, it was sintered at 1580 °C for 35 h to obtain an ITO target material (the mass ratio of In2O3 to SnO2 was 99:1).

[0057] The density of the ITO target material was determined to be 7.11 g / cm³ based on Archimedes' principle of water displacement. 3 The density was 99.4%, and the internal structure was observed using a metallographic microscope, with the following results: Figure 1 As shown. By Figure 1 It can be seen that the average grain size of the ITO target is 5.5 micrometers.

[0058] Example 2

[0059] Take 970g with a specific surface area of ​​12m² 2 / g of nano-indium oxide powder was mixed with pure water to prepare nano-indium oxide slurry with a solid content of 60%;

[0060] Add 23.4g of 99.993% pure metallic tin to 400mL of 1mol / L dilute nitric acid to dissolve it, and a tin salt solution is obtained;

[0061] 400 mL of tin nitrate solution was mixed with nano-indium oxide slurry. The mixing was carried out in a sand mill at 1500 rpm and milled for 4 h with 0.3 mm zirconia balls. Then, 1.5 mol / L ammonia water was added to the resulting slurry to adjust the pH to 10. Then, 0.8% of the total mass of indium oxide and tin hydroxide in the mixture was added as binder PVA and 0.4% of the total mass of indium oxide and tin hydroxide in the mixture as plasticizer PEG. The mixture was then milled for another 60 min.

[0062] The slurry after sand milling was spray-granulated at 150°C to obtain nano-indium oxide / tin hydroxide composite.

[0063] The obtained indium oxide / tin hydroxide composite was formed into a preform under a pressure of 250 MPa, and after debinding, it was sintered at 1550 °C for 25 h to obtain an ITO target material (the mass ratio of In2O3 to SnO2 was 97:3).

[0064] The density of the ITO target material was determined to be 7.11 g / cm³ based on Archimedes' principle of water displacement. 3 The density was 99.4%, and the internal structure was observed using a metallographic microscope, with an average grain size of 5.8 micrometers.

[0065] Example 3

[0066] Take 950g with a specific surface area of ​​12m² 2 / g of nano-indium oxide powder was mixed with pure water to prepare nano-indium oxide slurry with a solid content of 30%;

[0067] Add 39g of 99.993% pure metallic tin to 500mL of 1mol / L dilute nitric acid to dissolve it, and a tin salt solution is obtained.

[0068] 500 mL of tin nitrate solution was mixed with nano-indium oxide slurry. The mixing was carried out in a sand mill at a speed of 2100 rpm and milled for 3 h with 0.3 mm zirconia balls. Then, 1.5 mol / L ammonia water was added to the resulting slurry to adjust the pH to 10. Then, 0.8% of the total mass of indium oxide and tin hydroxide in the mixture was added as binder PVA and 0.4% of the total mass of indium oxide and tin hydroxide in the mixture as plasticizer PEG. The mixture was then milled for another 30 min.

[0069] The slurry after sand milling was spray-granulated at 150°C to obtain nano-indium oxide / tin hydroxide composite.

[0070] The obtained indium oxide / tin hydroxide composite was formed into a preform under a pressure of 150 MPa, and after debinding, it was sintered at 1500℃ for 20 h to obtain an ITO target material (the mass ratio of In2O3 to SnO2 was 95:5).

[0071] The density of the ITO target material was determined to be 7.12 g / cm³ based on Archimedes' principle of water displacement. 3 The density was 99.55%, and the internal structure was observed using a metallographic microscope, with an average grain size of 6.4 micrometers.

[0072] Example 4

[0073] The indium oxide / tin hydroxide composite of Example 3 was formed into a preform under a pressure of 200 MPa, and after debinding, it was sintered at 1400 °C for 35 h to obtain an ITO target material (the mass ratio of In2O3 to SnO2 was 95:5).

[0074] The density of the ITO target material was determined to be 7.08 g / cm³ based on Archimedes' principle of water displacement. 3 The density was 99%, and the internal structure was observed using a metallographic microscope, with an average grain size of 4.5 micrometers.

[0075] Example 5

[0076] The indium oxide / tin hydroxide composite of Example 3 was formed into a preform under a pressure of 200 MPa, and after debinding, it was sintered at 1600 °C for 25 h to obtain an ITO target material (the mass ratio of In2O3 to SnO2 was 95:5).

[0077] The density of the ITO target material was determined to be 7.13 g / cm³ based on Archimedes' principle of water displacement. 3 The density was 99.7%, and the internal structure was observed using a metallographic microscope, with an average grain size of 6.9 micrometers.

[0078] Comparative Example 1

[0079] 950g with a specific surface area of ​​12m² 2 / g of nano-indium oxide powder, 50g of powder with a specific surface area of ​​12m² 2 / g of nano-tin oxide powder and water were mixed to prepare a slurry with a solid content of 30%. The mixing was carried out in a sand mill at a speed of 2100 rpm and milled with 0.3 mm zirconia balls for 3 hours to obtain the slurry.

[0080] Add 0.8% of the total mass of nano-indium oxide and nano-tin oxide PVA binder and 0.4% of the total mass of nano-indium oxide and nano-tin oxide PEG plasticizer to the slurry, and then grind it with 0.3 mm zirconia balls at a speed of 2100 rpm for 30 min.

[0081] The slurry after sand milling is spray-granulated at 150°C to obtain nano ITO powder.

[0082] The obtained ITO powder was formed into an ITO preform under a pressure of 150 MPa, and after debinding, it was sintered at 1500℃ for 35 h to obtain an ITO target material (the mass ratio of In2O3 to SnO2 was 95:5).

[0083] The density of the ITO target material was determined to be 6.92 g / cm³ based on Archimedes' principle of water displacement. 3 The density was 96.7%, and the internal structure was observed using a metallographic microscope, with an average grain size of 5.8 micrometers.

[0084] Comparative Example 2

[0085] The nano-ITO powder of Comparative Example 1 was formed into an ITO preform under a pressure of 150 MPa. After debinding, it was sintered at 1600℃ for 35 h to obtain an ITO target material (the mass ratio of In2O3 to SnO2 was 95:5).

[0086] The density of the ITO target was determined to be 7.01 g / cm³ based on Archimedes' principle of water displacement. 3 The density was 98%, and the internal structure was observed using a metallographic microscope, with an average grain size of 8.5 micrometers.

[0087] Comparative Example 3

[0088] 990g with a specific surface area of ​​12m² 2 / g of nano-indium oxide powder, 10g of which has a specific surface area of ​​12m² 2 / g of nano-tin oxide powder and water were mixed to prepare a slurry with a solid content of 30%. The mixing was carried out in a sand mill at a speed of 2100 rpm and milled with 0.3 mm zirconia balls for 3 hours to obtain the slurry.

[0089] Add 0.8% of the total mass of nano-indium oxide and nano-tin oxide PVA binder and 0.4% of the total mass of nano-indium oxide and nano-tin oxide PEG plasticizer to the slurry, and then grind it with 0.3 mm zirconia balls at a speed of 2100 rpm for 30 min.

[0090] The slurry after sand milling is spray-granulated at 150°C to obtain nano ITO powder.

[0091] The obtained ITO powder was formed into an ITO preform under a pressure of 150 MPa, and after debinding, it was sintered at 1600℃ for 35 h to obtain an ITO target material (the mass ratio of In2O3 to SnO2 was 99:1).

[0092] The density of the ITO target material was determined to be 6.45 g / cm³ based on Archimedes' principle of water displacement. 3 The density was 90.2%, and the internal structure was observed using a metallographic microscope, with an average grain size of 9.7 micrometers.

[0093] Comparative Example 4

[0094] Take 785.6g of indium metal with a purity of 99.993% and 39g of tin metal with a purity of 99.993%, add them together to 3000mL of 2mol / L dilute hydrochloric acid for dissolution, then adjust the pH of the resulting solution to 8.5 with 1.5mol / L ammonia water, then add 0.8% of the total mass of the indium hydroxide / tin hydroxide composite binder PVA and 0.4% of the total mass of the indium hydroxide / tin hydroxide composite plasticizer PEG to the resulting precipitate mixture, and mill at 1800rpm for 1h.

[0095] The slurry after sand milling is spray-granulated at 150°C to obtain nano ITO powder.

[0096] The obtained ITO powder was molded into ITO preforms under a pressure of 200 MPa. After debinding, the preforms were sintered at 1580℃ for 20 hours. However, the ITO preforms cracked at 600℃ and crumbled into more than a dozen pieces at 900℃, making further sintering impossible.

[0097] Table 1. Sintering performance of trace-doped nano-ITO powder

[0098]

[0099] As shown in Table 1, directly ball-milling indium oxide and tin oxide powders cannot produce ITO targets with high sintering activity; the resulting ITO targets have low density, failing to meet the requirement of ≥99%. However, by introducing trace components through precipitation, the density of the ITO target can reach ≥99%. Furthermore, the process is simple, requiring no aging, cleaning, or calcination; the powder can be directly shaped and sintered after spray granulation. Nitrates and ammonium salts decompose during sintering, having no impact on the sintering performance of the ITO target. In contrast, co-precipitated indium hydroxide and tin hydroxide, without calcination, result in severe cracking and cannot produce dense ITO ceramic targets.

[0100] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method of producing an ITO target material, characterized by, Includes the following steps: The indium oxide / tin hydroxide composite was molded and sintered to obtain the ITO target material; The preparation method of the indium oxide / tin hydroxide composite includes the following steps: Nano-sized indium oxide, tin salt solution, hydroxide-containing inorganic base and water are mixed to carry out a precipitation reaction. The resulting precipitation product is granulated to obtain the indium oxide / tin hydroxide composite. The hydroxide-containing inorganic base is ammonia water, and the concentration of the ammonia water is 1~5 mol / L. The molar ratio of indium in the nano-indium oxide to tin in the tin salt solution is 20~100:

1.

2. The production method according to claim 1, characterized by, The tin salt includes tin nitrate.

3. The preparation method according to claim 1, characterized in that, The raw materials used in the mixing process also include binders and / or plasticizers.

4. The preparation method according to claim 3, characterized in that, The mass of the binder is 0.5-1% of the total mass of indium oxide and tin hydroxide in the indium oxide / tin hydroxide composite.

5. The preparation method according to claim 3, characterized in that, The mass of the plasticizer is 0.1 to 0.5% of the total mass of indium oxide and tin hydroxide in the indium oxide / tin hydroxide composite.

6. The preparation method according to claim 3, characterized in that, The mixing includes: mixing nano-indium oxide with water to obtain nano-indium oxide slurry; The slurry is mixed with a tin salt solution to obtain a mixed slurry; The mixed slurry is then mixed a third time with an inorganic alkali containing hydroxide ions, a binder, and a plasticizer.

7. The preparation method according to claim 6, characterized in that, The second and third mixing methods include ball milling; during the second and third mixing, the ball milling speed is independently 1500~2500 rpm, the time is independently 0.5~5h, and the grinding balls are independently 0.2~0.4mm zirconia balls.

8. The preparation method according to claim 1, characterized in that, The sintering temperature is 1400~1600℃.

9. The preparation method according to claim 1, characterized in that, The compression molding pressure is 150~250MPa, and the time is 2~10min; the sintering time is 15~35h.

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