CN1412117A - Method for preparing indium tin oxide powder by aqueous solution method - Google Patents

Abstract

A process for preparing indium tin oxide powder by aqueous solution method includes such steps as dissolving indium compound and tin compound in water respectively by water and proper additive to obtain two clear solutions, adding proper additive to generate metal hydroxide, filtering, washing with water, adding proper additive to peptize to make the particular components of different metal hydroxides undergo hydrolysis and condensation reactions, drying and calciningTo a high quality nano-scale (nano-meter, 10)^－9) Indium tin oxide powder. The indium tin oxide powder prepared by the method has higher density.

Description

Method for preparing indium tin oxide powder by aqueous solution method

technical field

The present invention relates to a method for preparing indium tin oxide powder (hereinafter referred to as ITO) by an aqueous solution method, in particular to processing different sources of materials to prepare high-quality nano-scale (nanomelter, 10 ^-9 ) ITO powder.

Background technique

Since ITO powder is the raw material for preparing ITO sputtering targets, if you want to obtain high-quality, high-density ITO sputtering targets, you need to form uniform nano-scale ITO powder.

Indium Tin Oxide (Indium Tin Oxide) is a kind of tin-doped indium oxide, generally called indium tin oxide, which belongs to n-type semiconductor. In indium, the electron concentration of free carriers increases, thereby improving its conductivity.

The thin film made of ITO has high conductivity, high transmittance to visible light, and high reflectivity to infrared rays, so it is widely used in transparent electrodes of solar cells, driving devices of flat panel displays and photodetectors , transparent heating components, antistatic film, electromagnetic wave protective film and other electronic, optical and optoelectronic devices, especially transparent conductive electrode materials for liquid crystal displays (LCD).

ITO thin films can be prepared by vacuum evaporation, magnetron sputtering, chemical vapor deposition, and dip coating. Among them, the sputtering method is more suitable for large-area substrates, and the process temperature is lower, which saves energy and does not produce harmful substances, which is environmentally friendly. Therefore, the sputtering method is often used in the preparation of ITO thin films.

The sputtering method mainly uses high-energy ions to hit a suitable target, knock out the substance of the target, sputter it onto the target substrate, and deposit the required substance on the substrate, and the deposited substance is closely related to the composition of the target. That is, it is related to factors such as the purity, composition and uniformity, density, and particle size distribution of the microstructure of the target material.

Generally, the target material for sputtering is made by mixing oxides, mainly by mixing different oxide raw material powders mechanically, and then using a solid-state reaction method of hot (uniform) pressure or cold (uniform) pressure. into targets with mixed oxides.

The traditional solid-state reaction method is to mix the powders of indium oxide and tin oxide mechanically (such as ball milling), dry them and then calcinate them to obtain ITO powder.

The mixing uniformity of different oxides in the target has its limit, because the oxides may contain impurities, as well as the composition and particle size distribution of the raw materials, which in turn affect the conductivity, light transmittance and adhesion with the substrate of the ITO film. adhesion.

Another method that can be used to prepare ultrafine powders for target materials is the aqueous solution method, which uses water to dissolve the metal compound to be mixed, and then undergoes appropriate treatment to polymerize the dissolved metal compound into a stable suspension in water, and has a high Molecular weight particles form a suspension solution, and finally remove all solvents by heating and drying to obtain ultrafine powder for preparing sputtering targets.

The known solid-state reaction method has the defect of imprecise preparation, and the inventor also found that the finished product obtained by the aqueous solution method also has the defect of imprecise, especially the known aqueous solution method without degumming procedure, the particle size of the obtained product Larger, and the composition is less uniform, in order to better meet the actual needs, the inventor is to carry out research and development, in order to solve the problem that the known technology cannot achieve precision preparation.

Contents of the invention

The object of the present invention is to provide a method for preparing indium tin oxide powder with an aqueous solution method, and provide a method for preparing a target material for sputtering with the obtained finished product. The raw materials obtained by different preparation methods are prepared by using an aqueous solution process (Solution Process). Appropriate solvents and additives are used to dissolve compounds of different metals to prepare two clear solutions, and then mix the two solutions uniformly by stirring to prepare a uniform aqueous solution, so that specific components in different compounds undergo condensation reactions. The special degumming procedure of adding acid solution after adding alkali solution makes it form a stable suspension of suspended hydroxide particles with appropriate molecular weight, uniform composition and small particle size; the fine powder obtained after removing the solvent is homogenized Press forming and sintering process to prepare a sputtering target with better chemical uniformity, which can increase the service life of the target and improve the characteristics of the film formed after sputtering.

The above-mentioned stable suspension solution prepared according to the present invention can be used to remove the solvent by means of general heating and drying procedures to obtain nano-scale powders, which are subjected to equal pressure molding and sintering to prepare sputtering targets.

Use the aqueous solution process to prepare the sputtering target for ITO thin film, because the particle size and composition uniformity of the constituent particles of the sputtering target will affect the conductivity and light transmittance of the indium tin oxide thin film, and the aqueous solution process is because The coalescence reaction is triggered in the form of a solution to generate a target with molecular-level composition uniformity, so the prepared sputtering target can improve the conductivity and light transmittance of the sputtering film, and because the composition particles are small , to further reduce the temperature required for sintering and save energy consumption. In addition, a target with a small particle size in the microstructure can improve the shrinkage of the target during sputtering, strengthen the contact with the cooling water, and avoid overheating, so it can increase the service life of the target.

The present invention is a method for preparing indium tin oxide powder by an aqueous solution method, and the method for preparing a stable suspension solution is to use inorganic salts as starting materials, and the inorganic salts used in the present invention can be divided into three types according to different acquisition methods. Type: the first type is inorganic salts obtained by dissolving metals in acid solution; the second type is inorganic salts obtained by dissolving recycled waste targets in acid solution; the third type is generally commercially available Inorganic salts for sale.

In the preparation of aqueous solution starting from inorganic salts, inorganic metal salts will undergo hydrolysis and condensation reactions in water, in which metal cations will first react with water to produce indium ions, then undergo hydrolysis reactions, and then undergo nucleophilic reactions Substitution and nucleophilic addition two condensation reactions to produce M'-O-M bonded inorganic polymer suspended particles, after adding an appropriate amount of lye, the M'-O-M bonded inorganic polymer suspended particles are converted into M (OH) and M'(OH) hydroxide suspended particles, and then add a small amount of acid to inhibit the coalescence of the hydroxide to form a stable suspension.

Flow chart as shown in Figure 1, is a kind of method for preparing indium tin oxide powder with aqueous solution method of the present invention, according to flow chart, explain as follows:

a. Dissolution: Appropriate amounts of indium compound and tin compound are dissolved in water respectively. It is also possible to dissolve metal indium and metal tin, or the recovered waste target material in an appropriate amount of acid solution, and then dissolve it in water, so that the concentration of indium and tin ions contained in the aqueous solution is about 0.1M-5.0M as the dissolved The acid solution can be concentrated nitric acid, which can form indium nitrate with indium, and the acid solution can also be concentrated hydrochloric acid or a mixture of concentrated nitric acid and concentrated hydrochloric acid in an appropriate proportion. Wherein said tin compound is formed tin chloride.

b. Mixing: Mix the above two solutions thoroughly and stir them.

c. Precipitation: add an appropriate amount of lye to the mixed solution, adjust to an appropriate pH value, and cause the originally clear solution to precipitate, wherein the concentration of lye is 1N-12N, and the adjustment range of pH value is 3-9; The lye can be ammonia water or an ammonium hydroxide compound containing alkyl substitution such as 1-methylammonium hydroxide. Wherein this step may further comprise a stirring operation.

d. Filtration and water washing: The above solution is filtered through an appropriate method such as reduced pressure filtration, and the filter cake is broken up again with pure water, and this action is repeated more than once. That is, a water-washed suspension is formed.

e. Degumming: add an appropriate amount of acid solution to the washed suspension to control the pH value of the solution in an appropriate range, and stir for an appropriate time to degumming. The concentration of the acid solution is 1N-15N, the adjustment range of the pH value is 1-6, and the stirring time is 2-72 hours; the acid solution can be nitric acid, hydrochloric acid, acetic acid, oxalic acid or formic acid, etc.

f. Drying: Dry the above-mentioned suspension after degumming to obtain a white indium hydroxide/tin (Indium Tin Hydroxide, hereinafter referred to as ITH) powder. The method of drying the indium tin oxide powder can be direct drying in an oven or use Spray dryer to dry.

g. Calcining: put the white ITH powder into a high-temperature furnace, and calcinate it into yellow-green ITO powder after proper heating rate, holding temperature and holding time. Wherein, the heating rate is 1-20°C/min, the holding temperature is 300-1100°C, and the holding time is 0.5-5 hours.

Description of drawings

In order to further understand the technology, means and effects adopted by the present invention to achieve the intended purpose, a preferred and feasible embodiment will be described in detail below in conjunction with the accompanying drawings.

Fig. 1 is the aqueous solution process flowchart of the present invention;

Fig. 2 is the EPMA figure of embodiment five of the present invention;

Fig. 3 is the EPMA diagram of the sixth embodiment of the present invention.

Detailed ways

Embodiment one (commercially sold inorganic salt)

a. Get 50.05g indium nitrate (containing one crystal water, purity 99.99% molecular weight is 318.85) and 5.67g tin chloride (containing five crystal waters, purity 99%, molecular weight is 350.50) and dissolve them in deionized water respectively, and make The final volumes of the solutions were 155 mL and 16 mL respectively, and the concentrations of indium and tin ions were 1.0 M at this time.

b. Thoroughly mix and stir the above two clear solutions. At this time, the molar ratio of indium tin ions is 95:5.

c. In the state of stirring, add 35mL concentrated ammonia water (25wt%) quickly, so that the originally clear solution produces white precipitate, and the pH value at this time is 7.25.

c1. The above solution containing the white precipitate was continuously stirred for at least 12 hours.

d. Filter the water from the above solution by vacuum filtration to obtain a white filter cake, then put it into deionized water and re-stir to break up the filter cake, and repeat this action three times. After the last filtration, deionized water was added to bring the volume of the solution to approximately 180 mL to obtain a suspension.

e. Add 3 mL of concentrated nitric acid (70 wt%) to the suspension after washing and filtering with water to make the pH of the solution 3.58, and stir for 24 hours.

e1. The above solution was measured by a particle size analyzer, and its particle size was 153nm.

f. Spray-dry the above degummed suspension to obtain a total of 32.61 g of white indium hydroxide/tin (Indium Tin Hydroxide, hereinafter referred to as ITH) powder. Through thermogravimetric analysis (TG analysis) result, its loss rate is 28.1%.

g. Put the above-mentioned white ITH powder into a high-temperature furnace, and keep the temperature at 800° C. for 3 hours at a heating rate of 10° C./min to obtain a yellow-green ITO powder.

Embodiment two (the metal of commercial sale is made inorganic salt)

a. Take 25.02g metal indium (purity 99.99% molecular weight 114.8), dissolve it in 100mL concentrated nitric acid (70wt%), add appropriate amount of deionized water, make the final volume of the solution be 218mL, and the indium ion concentration at this time is 1.0M. Get 7.94g of tin chloride (containing five crystal waters, purity 99%, molecular weight 350.50) and dissolve it in deionized water, and make the final volume of the solution 22mL, so that the concentration of indium and tin ions are each 1M.

b. Thoroughly mix and stir the above two clear solutions. At this time, the molar ratio of indium tin ions is 95:5.

c. In the state of stirring, add 75mL concentrated ammonia water (25wt%) quickly, so that the originally clear solution produces white precipitate, and the pH value is 7.11 at this time.

c1. The above solution containing the white precipitate was continuously stirred for at least 12 hours.

d. Filter the water from the above solution by vacuum filtration to obtain a white filter cake, then put it into deionized water and re-stir to break up the filter cake, and repeat this action three times. After the last filtration, deionized water was added to make the solution volume about 240 mL to obtain a suspension.

e. Add 5 mL of concentrated nitric acid (70 wt%) to the suspension after washing and filtering to make the pH of the solution 3.42, and stir for 24 hours.

e1. The above solution was measured by a particle size analyzer, and its particle size was 142nm.

f. Spray-dry the above degummed suspension to obtain a total of 43.18 g of white indium hydroxide/tin hydroxide (Indium Tin Hydroxide, hereinafter referred to as ITH) powder. According to the result of thermogravimetric analysis (TG analysis), the loss rate is 25.54%

g. Put the above-mentioned white ITH powder into a high-temperature furnace, and keep the temperature at 800° C. for 3 hours at a heating rate of 10° C./min to obtain a yellow-green ITO powder.

Embodiment three (metal dissolves into inorganic salt with acid) (comparison known implementation)

a. Take 25.11g metal indium (purity 99.99%, molecular weight is 114.8), dissolve in 100mL concentrated nitric acid (70wt%), add appropriate amount of deionized water, make the final volume of the solution be 218mL, and the indium ion concentration is 1.0M at this moment. Get 7.96g tin chloride (containing five crystal waters, purity 99%, molecular weight is 350.50) and dissolve in deionized water, and make the final volume of solution be 22mL, make indium, tin ion concentration each be 1M.

b. Thoroughly mix and stir the above two clear solutions. At this time, the molar ratio of indium tin ions is 95:5.

c. In the state of stirring, add 100mL concentrated ammonia water (25wt%) quickly, so that the originally clear solution produces white precipitate, and the pH value is now 7.16.

c1. The above solution containing the white precipitate was continuously stirred for at least 12 hours.

d. Filter the water from the above solution by vacuum filtration to obtain a white filter cake, then put it into deionized water and re-stir to break up the filter cake, and repeat this action three times. After the last filtration, deionized water was added to bring the volume of the solution to approximately 240 mL to obtain a suspension.

e. The above-mentioned suspension after washing and filtering with water was stirred for 24 hours without adding any acid.

e1. The above solution is measured by a particle size analyzer, and its particle size is 2350nm.

f. The above degummed suspension was dried by a spray drying method to obtain a total of 43.18 g of white indium hydroxide/tin (Indium Tin Hydroxide, hereinafter referred to as ITH) powder. Through thermogravimetric analysis (TG analysis) result, its loss rate is 25.54%.

g. Put the above-mentioned white ITH powder into a high-temperature furnace, and keep the temperature at 800° C. for 3 hours at a heating rate of 10° C./min to obtain a yellow-green ITO powder.

Embodiment 4 (recycled and reused ITO waste target material)

a. Take 10.03g of ITO waste target material and dissolve it in 100mL concentrated hydrochloric acid (37wt%). After the dissolution is complete, remove undissolved impurities by filtration.

The solution was quantified by ICP-AES (inductively coupled plasma-atomic emission spectrometer) with inductively coupled ions and atoms, and the indium/tin ratio was 15. An appropriate amount of deionized water was added to make the final volume of the solution 150 mL.

a1. Get 6.10g of tin chloride (containing five crystal waters, with a purity of 99%, and a molecular weight of 350.50) and dissolve it in 25mL of deionized water.

b. Thoroughly mix and stir the above two clear solutions. At this time, the molar ratio of indium tin ions is 95:5.

c. In the state of stirring, quickly add 150mL concentrated ammonia water (25wt%), so that the originally clear solution produces white precipitate, and the pH value is now 7.30.

c1. The above solution containing the white precipitate was continuously stirred for at least 12 hours.

d. Filter the water from the above solution by vacuum filtration to obtain a white filter cake, then put it into deionized water and re-stir to break up the filter cake, and repeat this action three times. After the last filtration, deionized water was added to bring the solution volume to approximately 175 mL to obtain a suspension.

e. Add 5 mL of concentrated nitric acid (70 wt%) to the suspension after washing and filtering with water to make the pH of the solution 3.50, and stir for 24 hours.

e1. The above solution was measured by a particle size analyzer, and its particle size was 127nm.

f. The above degummed suspension was dried by spray drying to obtain a total of 9.64 g of white indium hydroxide/tin (Indium Tin Hydroxide, hereinafter referred to as ITH) powder. Through thermogravimetric analysis (TG analysis) result, its loss rate is 25.15%.

g. Put the above-mentioned white ITH powder into a high-temperature furnace, and keep the temperature at 800° C. for 3 hours at a heating rate of 10° C./min to obtain a yellow-green ITO powder.

Embodiment five (preparation embodiment of the present invention)

(1). Take 50g of the ITO powder prepared by the method of the above-mentioned embodiment 2, put it into a 1L ball mill jar, add 50g of water, prepare a slurry with a solid content of 50wt%, and ball mill for 24 hours.

(2). The above slurry is dried to obtain ball-milled ITO powder.

(3). Put the powder into the mold at 1.6 o'clock, and undergo cold pressing and cold equalizing molding respectively to obtain the green body of the ITO target.

(4). Put the above-mentioned target green body into a high-temperature calcination furnace, and the calcination conditions are as follows:

Step 1: From room temperature to 1000°C at a heating rate of 10°C/min;

Step 2: Raise the temperature from 1000°C to 1550°C at a heating rate of 0.5°C/min, and keep the temperature for 12 hours, and at this time, inject -atmospheric oxygen;

Step 3: Decrease the temperature from 1550°C to 1000°C at a cooling rate of 0.5°C/min, while maintaining oxygen at one atmosphere;

Step 4: Cool to room temperature in a natural furnace below 1000°C.

(5). The ITO target material at 1.3 hours can be obtained through the above steps, and the density of the target material is 96% as measured by the Archimedes method.

Embodiment six (the comparative example of known preparation)

(1). Take 45g of commercial indium oxide powder and 5g of tin oxide powder respectively, put them into a 1L ball mill jar, add 50g of water, prepare a slurry with a solid content of 50wt%, and ball mill for 24 hours.

(2). The above slurry is dried to obtain ball-milled ITO powder.

(3). Put the powder into the mold at 1.6 o'clock, and undergo cold pressing and cold isostatic pressing respectively to obtain the green body of the ITO target.

(4). Put the above-mentioned target green body into a high-temperature calcination furnace, and the calcination conditions are as follows:

Step 1: From room temperature to 1000°C at a heating rate of 10°C/min;

Step 2: Raise the temperature from 1000°C to 1550°C at a rate of 0.5°C/min, and keep the temperature for 12 hours, and then inject oxygen at one atmosphere;

Step 3: Decrease the temperature from 1550°C to 1000°C at a cooling rate of 0.5°C/min, while maintaining oxygen at one atmosphere;

Step 4: Cool to room temperature in a natural furnace below 1000°C.

(5). Calcining the above-mentioned green target material to obtain a 1.3-hour ITO target material, the density of the target material is 95% as measured by the Archimedes method.

Result comparison:

The targets obtained in the above-mentioned Example 5 and Example 6 were respectively measured by electron probe microanalysis EPMA (electron probe microanalysis), and the distribution state of indium and tin was observed. Figures 2 and 3 are examples 5 and 3 respectively. In the EPMA diagram of the target in Example 6, the white dots are the distribution of tin oxide. It can be found that the distribution of tin oxide in the target prepared by the powder prepared in Example 2 of the present invention is even greater than that of the target prepared by the traditional solid-state method. good.

In summary of the above-mentioned treatment procedures, the present invention mainly uses the method of stirring to promote the homogenization of the solution, and then uses the control mode of the degumming process to suppress the coalescence of hydroxides. Preparation process and known preparation process, the obtained particle size is 142, 2350nm, and the difference is 16.5 times, thus we can know that the fineness of the present invention, when using the embodiment one, two, four to prove that the present invention can use three All kinds of raw materials can reach the object of the present invention, and then further make finished products with the foregoing embodiment five and six, the result of comparison also proves that the present invention has higher density than the known ones; therefore, the process of the present invention has practical properties, to produce progressive performance different from known ones.

The above description is the detailed description and drawings of the preferred embodiments of the present invention, and is not intended to limit the present invention. Any approximate structures that do not deviate from the spirit of the present invention and make similar changes thereof should be included in the present invention. middle.

Claims (12)

1. A method for preparing indium tin oxide powder with an aqueous solution method, the steps are: a. Dissolution: Dissolve the indium compound and the tin compound in water respectively, so that the concentration of indium and tin ions is about 0.1M-5.0M; b Mixing: fully mix the above two solutions and stir them; c. Precipitation: Add lye to the mixed solution, adjust to an appropriate pH value, and cause the originally clear solution to precipitate, wherein the concentration of lye is 1N-12N, and the adjustment range of pH value is 3-9; d. Filtration and water washing: filter the above solution under reduced pressure, and break up the filter cake again with pure water. Repeat this action more than once to form a suspension after washing; e. Degumming: add acid solution to the suspension after washing, adjust to an appropriate pH value, and stir to degumming, wherein the concentration of the acid solution is 1N-15N, the adjustment range of the pH value is 1-6, and the stirring time is 2-72 hours; f. Drying: drying the above-mentioned suspension after degumming to obtain white indium hydroxide/tin powder; and g. Calcining: put white indium hydroxide/tin powder into a high-temperature furnace, and calcinate into yellow-green indium tin oxide powder through appropriate heating rate, holding temperature and holding time, wherein the heating rate is 1- 20°C/min, the holding temperature is 300-1100°C, and the holding time is 0.5-5 hours. 2. the method for preparing indium tin oxide powder with aqueous solution method as claimed in claim 1, wherein said indium compound, tin compound are the waste target material that reclaims, and waste target material is dissolved in the acid solution and forms, and waste target material It refers to the used sputtering target. 3. The method for preparing indium tin oxide powder by an aqueous solution method as claimed in claim 2, wherein said acid solution is concentrated nitric acid or concentrated hydrochloric acid, or a mixed solution of concentrated nitric acid and concentrated hydrochloric acid. 4. The method for preparing indium tin oxide powder by aqueous solution method as claimed in claim 1, wherein said indium compound and tin compound are respectively dissolving metal indium and metal tin in acid solution. 5. The method for preparing indium tin oxide powder by an aqueous solution method as claimed in claim 4, wherein said acid solution is nitric acid, and forms indium nitrate. 6. The method for preparing indium tin oxide powder with an aqueous solution method as claimed in claim 4, wherein said tin compound forms tin chloride. 7. The method for preparing indium tin oxide powder by an aqueous solution method as claimed in claim 1, wherein in the c step, the lye is ammonia or an alkyl-containing ammonium hydroxide compound. 8. The method for preparing indium tin oxide powder by an aqueous solution method as claimed in claim 7, wherein said alkyl ammonium hydroxide compound is 1-methylammonium hydroxide. 9. The method for preparing indium tin oxide powder with an aqueous solution method as claimed in claim 1, wherein said step C further comprises a stirring operation. 10. The method for preparing indium tin oxide powder by an aqueous solution method as claimed in claim 1, wherein the acid solution in the step e is nitric acid, hydrochloric acid, acetic acid, oxalic acid or formic acid. 11. The method for preparing indium tin oxide powder with an aqueous solution method as claimed in claim 1, wherein the method of drying in step f is drying directly in an oven or using a spray dryer to dry. 12. A method for preparing indium tin oxide powder with an aqueous solution method, the steps of which are: a. Dissolution: dissolve the substances containing metal indium and metal tin in water respectively; b. Mixing: fully mix the above two solutions and stir them; c. Precipitation: add lye to the mixed solution, adjust to an appropriate pH value, and cause the originally clear solution to precipitate; d. Filtration and water washing: filter the above solution under reduced pressure, and re-disperse the filter cake with pure water. Repeat this action several times to form a suspension after washing; e. Degumming: add acid solution to the suspension after washing, adjust to an appropriate pH value, and stir to degumming; f. Drying: drying the above-mentioned suspension after degumming to obtain white indium hydroxide/tin powder; g. Calcining: put white indium hydroxide/tin powder into a high-temperature furnace, and calcinate into yellow-green indium tin oxide powder after proper heating rate, holding temperature and holding time.

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