Chemical Co-precipitation Method To Prepare Nano Ito Powder

In scattered metals, indium is one of the advantage resources in our country. Although China is the first on the indium resources and yields all over the world, there is a big margin with the developed countries in high and new technologies, the yield of deep processing products, the occupancy of the market and the economic effect. At present, 70～80% indium is export abroad, but the higher value products are imported from other countries. So it is necessary to exploit the indium deep processing products and to improve the indium industry structure.Indium tin oxide (ITO) is a tin-doped oxide semiconductor material. 80% of the indium total quantity is used in transparent electrodes. And they are used mainly for the thin film transistor(TFT), liquid crystal display(LCD), electroluminescent device(ELD), electroluminescent color device(ECD), plasma display panel(PDP), saving energy windows in the building, car windshield, microwave shield, protection mirror and transparent electrode for solar cell etc. But how to prepare the high-quality ITO powder is one of the key problems to produce the high-quality transparent conducting thin films. In this paper, the high purity indium from some companies was as the main raw material, the ammonia water as precipitator to produce ITO powders by the chemistry co-precipitation process.Based on the theory analysis of the chemistry co-precipitation for preparing ITO powders. The fabrication for ITO powders, in which ammonia water is used as precipitator to prepare the indium tin hydroxide in certain temperature, then through filtering, washing, drying, grinding and calcinating procedures is feasible. In order to obtain the nanosized, homogeneous and spheroidal ITO grains with large specific surface and good flowing ability, it is necessary to control the experiment conditions strictly and use the dispersant properly. In the experiments, the influences of several factors, such as Sn content, reaction temperature, indium ion concentration, the pH value at reaction end point, the temperatue and time of calcination are analyzed and discussed by some analysis methods such as chemical analysis, diffractional scanning calorimeter (DSC), thermogravimetry (TG), X-ray powder diffraction (XRD), transmission electron microscopy (TEM), electron probe microanalysis (EPMA) and Brunauer-Emmett-Teller analysis (BET) etc. And the optimum conditions to prepare nanosized ITO powder are obtained, 10% Sn content, 70℃reaction temperature, 20% ammonia water concentration, 50g/L indium ion concentration, 8.0ml/min injection rate ammonia water, pH=6.5～7.0 at reaction end point, aging 30 minutes at reaction temperature and then aging 2～3 hours at normal temperature, and then calcined at 760℃and for 4 hours. By this typical procedure , spheroidal ITO nano-particles with a narrow distribution of 20～35nm, specific surface area with 25 ~ 40m2/g are prepared, that measure up the requirement which desire grain size less than 100nm, specific surface area more than 15m~2/g, spheroidal morphology and non-aggregated, for producing the high definition ITO target.In order to investigate the feasibility adopting chemical co-deposition produce ITO powder in industry, three large-scale laboratory experiments with 50g, 60g and 60g metal indium for main raw material individually were carried on the above optimum conditions and the samples were characterized by XRD, TEM and BET motheds, the results indicated that the ITO powders have spheroidal morphology, 13.8nm the average crystal diameter with, 54.01m~2/g the specific surface area, 15~35nm dimension distribution and 1.1 the aggregation coefficient. Therefore, it is concluded that produce nano-sized ITO powders by chemical co-deposition process is feasible.