| Indium tin oxide (ITO) is a kind of important materials of indium, accounting for about 60% of the total of indium products. ITO is a kind of highly degenerate n-type semiconductor. Because of the excellent photoelectric properties, ITO are widely used in the field of electronics, automobile,military, and light-emitting materials and equipments etc.The structure performance, application and the consumer market of ITO powders are introduced in this paper. Comparing with different kinds of the preparation methods and principles, Ultrasonic Atomization Combined With Micro-wave Pyrolysis routing is chose to prepare ITO powders. Meanwhile, the principle and characteristics of Ultrasonic Atomization Combined With Micro-wave Pyrolysisare discussed, and the formation mechanism of ITO powders is also investigated in this paper.The ITO powders are prepared using precursor solution containing SnCl4·5H2o and InCl3, and the adding amounts of these two chemicals was calculated by the final products ITO which the final composition ratiois In2O3:SnO2=9:1wt%. A few ml of HCl was added to the solution to prevent the formation of hydroxide precipitate. The starting solution is atomized by an ultrasonic nebulizer, and the atomized droplets are dried and decomposed to ITO powders in horizontal microwave furnace. The purity and microstructures of ITO powders are characterized by X-ray diffractometer (XRD), scanning electron microscope (SEM) and Transmission electron microscopy.Different process parameters such as liquid precursor concentration, microwave pyrolysis temperature and the adding the surface active agent of ethanol and complex clathrate of citeic acid effect on the structure and properties of ITO powder. The experimental results show that the suitable concentration of the precursors and the temperature of microwave pyrolysis are the key factors to prepare the high quality of indium tin oxide (ITO) powders. The XRD results show that the diffraction peaks are In2O3 and no other peaks including SnO2 can be observed when the pyrolysis temperature is above 650℃. It is shown that SnO2 is dissolved in the crystal lattice of In2O3 and the powder of ITO is a solid solution composition. However, the higher pyrolysis temperature can more rapidly decompose the precursor solutions, the agglomeration of ITO powders will be produced as the temperature rises.When the carrier gas flow rate is too slow, the agglomeration of the powder is particularly serious, and the rate of carrier gas flow rate is too fast, it is easy to cause the crystallization of the powder. Similarly, when the concentration of precursor solutions increases from 0.01 mol/L to 0.1 mol/L, the conversion rates of ITO powders per unit times are increased. However, the diameter of the powders increases with the increasing precursor’s concentration.Citric acid added at high temperature does not affect the purity of the product, but citric acid addition will affect the morphology and dispersion, small amount of citric acid was added to the increase of broken shell powder, citric acid content increase does not appear to be a regular morphology of powder; increase the filter mesh, product sizes will more fine; microwave pyrolysis temperature affect the purity of the product; anhydrous ethanol addition makes the product even better.The results demonstrated that appropriate precursor solution concentration, temperature and proper quantity of additive are the key factors that have effect on the morphology of ITO powders. The extraordinarily fine ITO particles which have relatively small diameter, good dispersibility property and spherical shape morphology were prepared at the following parameters:650 "C pyrolysis temperature, 0.01 mol/1 concentration,0.61/min carrier gas,0.002 g/1 citric acid, and 30% alcohol. |
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