A method for preparing tin dioxide powder

Abstract

The present invention relates to the field of synthesis and preparation technology of nanomaterials, and in particular to a method for preparing tin dioxide powder, comprising the following steps: S1, configuring a 0.1-5 mol / L tin salt solution, adding a composite auxiliary agent to the tin salt solution, and performing ball milling after ultrasonic dispersion to obtain a pretreated tin salt solution; S2, freezing the pretreated tin salt solution in an ultra-low temperature environment to obtain a frozen sample; S3, transferring the frozen sample to a vacuum freeze dryer for dehydration to obtain a solid powder; S4, calcining the solid powder at high temperature to obtain tin dioxide powder. During the preparation process of the present invention, zero sewage discharge is achieved, the sewage discharge and treatment problems of traditional liquid phase powder making are overcome, and the phenomenon of sintering agglomeration accompanied by traditional solid phase calcination can be avoided, thereby achieving high-quality ultrafine tin dioxide powder preparation. This method is simple and safe in process and is easy to implement industrial large-scale production preparation.

Description

Technical Field

[0001] The present invention relates to the technical field of synthesis and preparation of nanomaterials, in particular to a method for preparing tin dioxide powder. Background Art

[0002] Tin dioxide (SnO2) is a wide-bandgap n-type semiconductor with a bandgap of 3.6 eV. It is chemically stable and insoluble in acidic or alkaline solutions. Due to its unique electronic structure and high visible light transmittance, it is widely used in optical electronic devices, energy storage devices, and sensor devices. In the field of optical electronic devices, ITO conductive film, composed of a mixture of indium oxide and tin dioxide, is an important optical device. Because the uniformity of the doping in the film is highly dependent on the uniformity and quality of the ITO target material, the preparation of ultrafine and highly uniform tin dioxide powder is of great significance for the synthesis of high-quality ITO targets.

[0003] At present, the main methods for preparing nano-sized tin dioxide powder include liquid phase precipitation, spray pyrolysis, sol-gel method, hydrothermal synthesis, solid-phase chemical synthesis, etc. The liquid phase reaction has a good particle size control effect and is easy to achieve large-scale industrial preparation of tin dioxide powder. For example, the existing patent CN202110213767.2 relates to a method for preparing nano-tin dioxide, comprising the following steps: dissolving analytically pure tin tetrachloride pentahydrate in pure water to obtain a tin tetrachloride solution with a concentration of 3 to 5 mol / L; adding a precipitant, controlling the reaction temperature to 60 to 80 ° C, and the pH value of the reaction liquid to 6.5 to 7.5; adding a conversion agent, controlling the pH value of the feed liquid to 9.0 to 10.0, heating to near boiling, and keeping warm for 20 to 30 minutes; adding a neutralizing agent, controlling the pH value of the feed liquid to 6.5 to 7.5; washing, filtering, drying; decomposing, cooling, crushing, and screening to obtain. However, the synthesis process requires a large amount of ultrapure water and wastewater, resulting in costly water treatment. The necessary filtration also increases production costs and inevitably consumes some of the tin source. Furthermore, solid-phase chemical synthesis methods, due to the difficulty in dispersing tin, are prone to sintering at high temperatures, resulting in coarsening of the tin dioxide particles. Therefore, finding a simple, pollution-free, large-scale tin dioxide production process is extremely important. Summary of the Invention

[0004] In view of this, the present invention proposes a method for preparing tin dioxide powder to solve the technical problems in the existing technology that the liquid phase synthesis method produces a large amount of waste liquid and has a large loss of raw materials, and the solid phase synthesis method is prone to sintering and resulting in particle coarsening, thereby realizing an efficient, environmentally friendly and particle size-controllable tin dioxide powder preparation process.

[0005] The technical solution of the present invention is achieved as follows: The present invention provides a method for preparing tin dioxide powder, comprising the following steps:

[0006] S1. Prepare a 0.1-5 mol / L tin salt solution, add a composite additive to the tin salt solution, ultrasonically disperse, and then perform ball milling to obtain a pretreated tin salt solution;

[0007] S2, placing the pretreated tin salt solution in an ultra-low temperature environment and freezing it to obtain a frozen sample;

[0008] S3, transferring the frozen sample to a vacuum freeze dryer for dehydration to obtain a solid powder;

[0009] S4. calcining the solid powder at high temperature to obtain tin dioxide powder.

[0010] Specifically, the present invention combines ball milling assistance, freeze drying and pyrolysis processes, and cooperates with a specific composite auxiliary agent system to prepare a tin dioxide powder with the advantages of narrow particle size distribution and uniform morphology. It can meet the strict requirements of high-performance optoelectronic devices, ITO targets, gas sensors and other fields. It not only avoids the shortcomings of liquid phase precipitation method that produces a large amount of waste liquid and material loss, but also overcomes the sintering and particle coarsening problems caused by high temperature in solid phase synthesis method. Among them, the composite auxiliary agent system can effectively control the uniform dispersion of tin elements and suppress the agglomeration phenomenon during high-temperature calcination; low-temperature freeze drying technology maintains the high dispersion state of the precursor and ensures that the final product has a uniform particle size. In addition, the entire preparation process is environmentally friendly, no waste liquid is generated, and it is in line with the concept of green chemistry.

[0011] On the basis of the above technical solution, preferably, in step S1, the tin salt solution is a stannous chloride solution or a stannous sulfate solution, and the composite auxiliary agent includes polyethylene glycol, polyoxyethylene castor oil and citric acid.

[0012] The composite auxiliary agent system used in the present invention is composed of three key components: polyethylene glycol, polyoxyethylene castor oil and citric acid. The synergistic effect of the three not only ensures the uniform dispersion of the tin salt solution during the ball milling process, but also maintains the high dispersion state of the precursor during the subsequent freeze-drying and pyrolysis processes, thereby achieving precise control of the particle size and morphology of the final product.

[0013] Based on the above technical solution, preferably, in step S1, in the composite auxiliary agent, the added amount of polyethylene glycol is 5-7% of the mass of the tin salt, the added amount of polyoxyethylene castor oil is 1.2-1.8% of the mass of the tin salt, and the added amount of citric acid is 18-22% of the mass of the tin salt.

[0014] As the basic component of the composite auxiliary agent, polyethylene glycol has good water solubility and biocompatibility. During the ball milling process, polyethylene glycol molecules prevent the local enrichment and agglomeration of tin ions through steric hindrance effects; polyethylene glycol also acts as a cryoprotectant during the freeze-drying process, slowing down the destruction of the dispersed state of tin salts during the ice crystal growth process. The molecular structure of polyoxyethylene castor oil has both hydrophilic and hydrophobic parts, which can form micelle structures in aqueous solutions, effectively encapsulating high-concentration tin ions, and synergizing with polyethylene glycol to build a multi-level protective barrier, which can significantly inhibit the migration and aggregation of particles caused by ice crystal extrusion during the freeze-drying process. Citric acid, as a polycarboxylic organic acid, can react with Sn 2+ The ions form a stable complex, which not only prevents premature hydrolysis and precipitation of tin ions during ball milling but also reduces the adverse effects of local pH fluctuations on surfactant adsorption. In the subsequent pyrolysis stage, citric acid decomposes to form small molecules such as CO2 and H2O, creating a uniform and porous precursor network structure, which is conducive to obtaining smaller tin dioxide particles.

[0015] Based on the above technical solution, preferably, in step S1, the ball milling temperature is 20-25°C, the ball-to-material ratio is 7-8:1, the ball milling medium is zirconium balls or alumina balls, the ball milling time is 40-80 min, and the ball milling speed is 300-400 rpm.

[0016] On the basis of the above technical solution, preferably, when the tin salt concentration is ≤1 mol / L, the ball milling is performed for 40-60 min; when the tin salt concentration is >1 mol / L, the ball milling is performed for 60-80 min.

[0017] The ball milling process introduced in this invention achieves deep homogenization of the tin salt solution and composite additives through mechanical impact and shearing. The microscopic shear force generated during ball milling promotes the formation of a more uniform and stable micelle structure in the polyoxyethylene castor oil, significantly enhancing its coating effect on tin ions. Ball milling also enables citric acid to form a more stable complex with tin ions, preventing localized hydrolysis and precipitation during freezing.

[0018] Based on the above technical solution, preferably, in step S2, the temperature of the ultra-low temperature environment is below -60°C, the freezing time is 60-120 minutes, and the spreading thickness of the solution after ball milling is 5-15 mm.

[0019] Based on the above technical solution, preferably, in step S3, the vacuum degree of the dehydration treatment is 10-20 Pa, and the frozen sample is first freeze-dried at -45~-55℃ for 12-14h, and then heated to -20~-30℃ and dried for 10-12h.

[0020] The present invention achieves perfect preservation of the precursor's microstructure through precisely controlled ultra-low temperature freezing and a two-stage sublimation process. Rapidly freezing the solution in an ultra-low temperature environment below -60°C forms tiny, uniform ice crystals, avoiding phase separation and component enrichment caused by slow freezing. In the subsequent two-stage freeze-drying, the main sublimation process is first carried out at -45 to -55°C, removing most of the ice crystals while maintaining the solid skeleton structure. The temperature is then raised to -20 to -30°C to remove adsorbed water and residual moisture, while avoiding skeleton collapse caused by excessive heating.

[0021] On the basis of the above technical solution, preferably, in step S4, the high-temperature calcination temperature is 600-800° C., the calcination atmosphere is air atmosphere, and the calcination time is 1-4 hours.

[0022] Based on the above technical solution, preferably, in step S4, the solid powder is first heated from room temperature to 300-400°C at a heating rate of 10-20°C / min and kept warm for 25-35 minutes; then the temperature is continued to be raised to 600-800°C at a heating rate of 1-10°C / min and kept warm for 1-3.5 hours.

[0023] The first stage involves rapidly heating to 300-400°C and holding the temperature for a short period. This is primarily used to remove residual organic matter and volatile components after freeze-drying, preventing sudden combustion of organic matter that could cause the precursor skeleton to collapse. The second stage involves slowly heating to 600-800°C and holding the temperature for an extended period. This is a critical process for the formation and growth of tin dioxide crystals. The appropriate heating rate ensures controlled grain growth and avoids local overheating and agglomeration caused by excessive heating. The 600-800°C temperature range precisely matches the requirements for tin dioxide crystal phase formation. Temperatures below 600°C prevent a fully crystallized product, while temperatures above 800°C lead to excessive grain growth.

[0024] The present invention provides tin dioxide powder prepared by any of the above methods.

[0025] The method for preparing tin dioxide powder of the present invention has the following beneficial effects compared with the prior art:

[0026] (1) The present invention adopts the process of "ball milling pretreatment-ultra-low temperature freezing-freeze drying-stage calcination". This method achieves zero wastewater discharge during the preparation process, overcoming the wastewater discharge and treatment problems of traditional liquid phase powder preparation, while avoiding the sintering and agglomeration phenomenon associated with traditional solid phase calcination, and achieving the preparation of high-quality ultrafine tin dioxide powder. This method is simple and safe, the synthesis yield can reach 100%, and it is easy to realize industrial large-scale production;

[0027] (2) The composite additive system (polyethylene glycol, polyoxyethylene castor oil, and citric acid) used in the present invention achieves multi-level protection and control of tin ions. Polyethylene glycol prevents tin ion aggregation through steric hindrance, polyoxyethylene castor oil forms a micellar structure that efficiently encapsulates tin ions and inhibits the ice crystal squeezing effect, and citric acid forms a stable complex with tin ions to control the hydrolysis rate. The synergistic effect of the three significantly improves the dispersion and uniformity of the precursor, laying the foundation for the preparation of high-quality tin dioxide powder.

[0028] (3) The ball milling pretreatment process introduced in the present invention breaks up the microscopic aggregates that may exist in the solution through mechanical shear force, thereby promoting sufficient contact and interaction between the additive molecules and the tin ions; ultra-low temperature rapid freezing forms tiny uniform ice crystals, avoiding phase separation caused by slow freezing; the dehydration treatment removes water while maintaining the precursor skeleton structure, effectively preventing the migration and agglomeration of components caused by capillary forces in traditional drying methods; finally, a staged calcination process (first rapidly heating to 300°C and keeping warm, then slowly heating to 600-800°C) is used to achieve precise control of the growth of tin dioxide grains. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0030] Figure 1 This is the X-ray diffraction pattern of the tin dioxide powder prepared in Example 1 of the present invention;

[0031] Figure 2 This is a high-magnification scanning electron microscope image of the tin dioxide powder prepared in Example 1 of the present invention;

[0032] Figure 3 This is a high-magnification scanning electron microscope image of the tin dioxide powder prepared in Example 2 of the present invention;

[0033] Figure 4 This is a high-magnification scanning electron microscope image of the tin dioxide powder prepared in Example 3 of the present invention. DETAILED DESCRIPTION

[0034] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0035] Polyethylene glycol was purchased from Hai'an (Linyi) Guoli Chemical Co., Ltd. with the model number of PEG-2000; polyoxyethylene castor oil was purchased from Shanghai Yuanye Biotechnology Co., Ltd. with the product specification of EL-40. Example 1

[0036] This embodiment provides a method for preparing tin dioxide powder, comprising the following steps:

[0037] S1, take 10g of stannous chloride to prepare 2.5mol / L stannous chloride solution, add composite auxiliary agent to the stannous chloride solution, the composite auxiliary agent includes 0.6g polyethylene glycol, 0.15g polyoxyethylene castor oil and 2.0g citric acid, after ultrasonic dispersion for 15min, transfer the mixed solution to a ball mill, add zirconium balls with a ball-to-material ratio of 7.5:1, ball milling at 22°C, speed 350rpm, ball milling for 70min, pausing for 1-2min every 15min during the ball milling process to avoid local overheating, and filtering to obtain a pretreated tin salt solution after the treatment is completed;

[0038] S2. Transfer the pretreated tin salt solution to a stainless steel or Teflon container, control the spreading thickness to 10 mm, and quickly freeze it in an ultra-low temperature environment below -60°C for 90 minutes to obtain a frozen sample;

[0039] S3. Transfer the frozen sample to a vacuum freeze dryer, set the vacuum degree to 15 Pa, freeze-dry the frozen sample at -50°C for 13 h, then heat it to -25°C and dry it for 11 h to obtain a solid powder;

[0040] S4. Place the solid powder in a quartz crucible, transfer it to a muffle furnace, and calcine it in an air atmosphere. First, heat the solid powder from room temperature to 350°C at a heating rate of 15°C / min and keep it warm for 30 minutes; then continue to heat it to 700°C at a heating rate of 5°C / min and keep it warm for 2.5 hours. Naturally cool it to room temperature to obtain tin dioxide powder. Example 2

[0041] S1, take 10g of stannous chloride to prepare 0.5mol / L stannous chloride solution, add composite auxiliary agent to the stannous chloride solution, the composite auxiliary agent includes 0.5g polyethylene glycol, 0.12g polyoxyethylene castor oil and 1.8g citric acid, after ultrasonic dispersion for 10min, transfer the mixed solution to a ball mill, add zirconium balls with a ball-to-material ratio of 7:1, ball milling at 20°C, speed 300rpm, ball milling for 40min, pausing for 1-2min every 15min during the ball milling process to avoid local overheating, and filtering after the treatment to obtain the pretreated tin salt solution;

[0042] S2. Transfer the pretreated tin salt solution to a stainless steel or Teflon container, control the spreading thickness to 5 mm, and quickly freeze it in an ultra-low temperature environment below -60°C for 120 minutes to obtain a frozen sample;

[0043] S3, transferring the frozen sample to a vacuum freeze dryer, setting the vacuum degree to 10 Pa, first freeze-drying the frozen sample at -55°C for 12 hours, then heating it to -30°C and drying it for 10 hours to obtain a solid powder;

[0044] S4. Place the solid powder in a quartz crucible, transfer it to a muffle furnace, and calcine it in an air atmosphere. First, raise the temperature of the solid powder from room temperature to 300°C at a heating rate of 10°C / min and keep it warm for 35 minutes; then continue to raise the temperature to 600°C at a heating rate of 1°C / min and keep it warm for 3.5 hours. Naturally cool it to room temperature to obtain tin dioxide powder. Example 3

[0045] S1, take 10g of stannous chloride to prepare 5mol / L stannous chloride solution, add composite auxiliary agent to the stannous chloride solution, the composite auxiliary agent includes 0.7g polyethylene glycol, 0.18g polyoxyethylene castor oil and 2.2g citric acid, after ultrasonic dispersion for 20min, transfer the mixed solution to a ball mill, add alumina balls with a ball-to-material ratio of 8:1, ball milling at 25°C, speed 400rpm, ball milling for 80min, pausing for 1-2min every 15min during the ball milling process to avoid local overheating, and filtering after the treatment to obtain the pretreated tin salt solution;

[0046] S2. Transfer the pretreated tin salt solution to a stainless steel or Teflon container, control the spreading thickness to 15 mm, and quickly freeze it in an ultra-low temperature environment below -60°C for 60 minutes to obtain a frozen sample;

[0047] S3, transferring the frozen sample to a vacuum freeze dryer, setting the vacuum degree to 20 Pa, first freeze-drying the frozen sample at -45 ° C for 14 h, then heating it to -20 ° C and drying it for 10 h to obtain a solid powder;

[0048] S4. Place the solid powder in a quartz crucible, transfer it to a muffle furnace, and calcine it in an air atmosphere. First, raise the temperature of the solid powder from room temperature to 400°C at a heating rate of 20°C / min and keep it warm for 25 minutes; then continue to raise the temperature to 800°C at a heating rate of 10°C / min and keep it warm for 1 hour. Naturally cool it to room temperature to obtain tin dioxide powder.

[0049] Comparative Example 1

[0050] This comparative example provides a method for preparing tin dioxide powder, comprising the following steps:

[0051] S1, take 10g of stannous chloride to prepare 2.5mol / L stannous chloride solution, add composite auxiliary agent to the stannous chloride solution, the composite auxiliary agent includes 0.6g polyethylene glycol, 0.15g polyoxyethylene castor oil and 2.0g citric acid, ultrasonically disperse for 15min, and filter after the treatment to obtain the pretreated tin salt solution;

[0052] The remaining steps are the same as in Example 1.

[0053] Comparative Example 2

[0054] This comparative example provides a method for preparing tin dioxide powder, comprising the following steps:

[0055] S1. Prepare a 2.5 mol / L stannous chloride solution with 10 g of stannous chloride, add a composite additive to the stannous chloride solution, and the composite additive includes 0.6 g of polyethylene glycol, 0.15 g of deionized water, and 2.0 g of citric acid. After ultrasonic dispersion for 15 min, transfer the mixed solution to a ball mill, add zirconium balls with a ball-to-material ratio of 7.5:1, and ball mill at 22 ° C., a speed of 350 rpm, and ball milling for 70 min. During the ball milling process, pause for 1-2 min every 15 min to avoid local overheating. After the treatment is completed, filter to obtain a pretreated tin salt solution;

[0056] The remaining steps are the same as in Example 1.

[0057] Comparative Example 3

[0058] This comparative example provides a method for preparing tin dioxide powder, comprising the following steps:

[0059] S1, take 10g of stannous chloride to prepare 2.5mol / L stannous chloride solution, add composite auxiliary agent to the stannous chloride solution, the composite auxiliary agent includes 0.6g deionized water, 0.15g polyoxyethylene castor oil and 2.0g citric acid, after ultrasonic dispersion for 15min, transfer the mixed solution to a ball mill, add zirconium balls with a ball-to-material ratio of 7.5:1, and ball mill at 22°C, a speed of 350rpm, and ball milling for 70min. During the ball milling process, pause for 1-2min every 15min to avoid local overheating. After the treatment is completed, filter to obtain a pretreated tin salt solution;

[0060] The remaining steps are the same as in Example 1.

[0061] Comparative Example 4

[0062] This comparative example provides a method for preparing tin dioxide powder. The preparation method is the same as that in Example 1, except that in step S2, no pre-freezing in an ultra-low temperature environment is performed. The specific method is as follows:

[0063] S2. Transfer the pretreated tin salt solution to a stainless steel or Teflon container, control the spreading thickness to 10 mm, and quickly place it in a low-temperature environment of -60°C to -10°C for pre-freezing. The freezing time is 90 minutes to obtain a frozen sample.

[0064] Comparative Example 5

[0065] This comparative example provides a method for preparing tin dioxide powder. The preparation method is the same as that in Example 1, except that no staged calcination is performed in step S4. The specific method is as follows:

[0066] S4. Place the solid powder in a quartz crucible, transfer it to a muffle furnace, and calcine it in an air atmosphere. First, raise the temperature of the solid powder from room temperature to 700°C at a heating rate of 15°C / min, keep it warm for 3 hours, and naturally cool it to room temperature to obtain tin dioxide powder.

[0067] Performance testing

[0068] ICP-MS was used to analyze and calculate the chemical elements of the powder, and TEM was used to measure the particle size of the powder. The test results are shown in Table 1.

[0069] Table 1 Performance test

[0070]

[0071] Figure 1 The X-ray diffraction pattern of the tin dioxide powder prepared in Example 1 is shown. Figure 2 The high-magnification scanning electron microscope image of the tin dioxide powder prepared in Example 1 is shown. Figure 3 A high-magnification scanning electron microscope image of the tin dioxide powder prepared in Example 2 is shown; Figure 4The following is a high-magnification scanning electron microscope image of the tin dioxide powder prepared in Example 3. As can be seen from the image, the product is pure tin dioxide, and the SEM image shows that the average particle size is less than 50 nm.

[0072] As can be seen from Table 1, the technical solution of this embodiment achieves the preparation of high-purity, small-particle-size tin dioxide powder by optimizing the ball milling treatment, composite auxiliary agent coordinated dispersion, ultra-low temperature pre-freezing and staged calcination process. In Comparative Example 1, the particle size increases due to uneven particle dispersion; in Comparative Examples 2-3, the particle agglomeration is not completely suppressed due to the weakened effect of the surfactant, and the particle size is inferior to that of the embodiment; in Comparative Example 4, the porous structure is destroyed due to the coarsening of ice crystals; in Comparative Example 5, the grains sinter due to rapid heating, and the particle size increases.

[0073] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing tin dioxide powder, characterized in that: The following steps are involved: S1. Prepare a 0.1-5 mol / L tin salt solution, add a composite auxiliary agent to the tin salt solution, ultrasonically disperse, and then perform ball milling to obtain a pretreated tin salt solution; the composite auxiliary agent includes polyethylene glycol, polyoxyethylene castor oil, and citric acid; S2, placing the pretreated tin salt solution in an ultra-low temperature environment and freezing it to obtain a frozen sample; S3, transferring the frozen sample to a vacuum freeze dryer for dehydration to obtain a solid powder; S4, calcining the solid powder at a high temperature to obtain tin dioxide powder; In step S1, the tin salt solution is a stannous chloride solution or a stannous sulfate solution; In step S1, the amount of polyethylene glycol added to the composite auxiliary agent is 5-7% of the mass of the tin salt, the amount of polyoxyethylene castor oil added is 1.2-1.8% of the mass of the tin salt, and the amount of citric acid added is 18-22% of the mass of the tin salt; In step S1, the ball milling temperature is 20-25° C., the ball-to-material ratio is 7-8:1, the ball milling medium is zirconium balls or alumina balls, the ball milling time is 40-80 min, and the ball milling speed is 300-400 rpm; In step S2, the temperature of the ultra-low temperature environment is below -60°C, the freezing time is 60-120 minutes, and the solution after ball milling is spread to a thickness of 5-15 mm.

2. A method for preparing tin dioxide powder according to claim 1, characterized in that: When the tin salt concentration is ≤1 mol / L, ball milling is performed for 40-60 min; when the tin salt concentration is >1 mol / L, ball milling is performed for 60-80 min.

3. A method for preparing tin dioxide powder according to claim 1, characterized in that: In step S3, the vacuum degree of the dehydration treatment is 10-20 Pa. The frozen sample is first freeze-dried at -45~-55℃ for 12-14h, and then heated to -20~-30℃ and dried for 10-12h.

4. A method for preparing tin dioxide powder according to claim 1, characterized in that: In step S4, the high-temperature calcination temperature is 600-800° C., the calcination atmosphere is air atmosphere, and the calcination time is 1-4 hours.

5. A method for preparing tin dioxide powder according to claim 4, characterized in that: In step S4, the solid powder is first heated from room temperature to 300-400°C at a heating rate of 10-20°C / min and kept warm for 25-35 minutes; then the temperature is continued to be raised to 600-800°C at a heating rate of 1-10°C / min and kept warm for 1-3.5 hours.

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