Solvent effect on synthesis of indium tin oxide nano-powders by a solvothermal process

Abstract

Well-crystallized and nano-sized indium tin oxide (ITO) powders were prepared by a solvothermal process from a mixed solution consisting of indium nitrate and tin chloride. The characteristics of the solvothermally synthesized ITO powders were studied to investigate the contribution of the processing variables (solvent, working temperature, working pressure) on the physico-chemical properties. The results of this study show that the nano-sized blue ITO powders with a single phase could be directly obtained by changing the medium from water to organic solvent. Comparison of the yellow ITO powders synthesized by the coprecipitation using calcination of precipitates and blue ITO powders synthesized by the solvothermal process indicated that the solvothermal process led to an in situ reduction reaction. Solvent viscosity in the solvothermal process strongly influences both electrical and optical properties of ITO materials for transparent conducting oxides (TCOs). The size of synthesized ITO particles increased with increasing solvent viscosity due to steric hindrance. Moreover, the shape of the synthesized ITO particles became more square with increasing solvent viscosity, because the preferred orientation of ITO materials for crystallization is the fastest in the 〈1 0 0〉 direction.