Synthesis and characterization of Sn doped InO₃ (ITO) nanowires by carbothermal reduction method

Full text: The indium tin oxide (ITO) is a solid solution composed by In₂O₃ -SnO₂ and this material is known due to its exceptional transparence in the visible range and high conductivity, which has many potential applications [1]. The practical application of ITO is strongly dependent on the structure and morphology of the material. For this reason it is very important to have a fine control over these characteristics during the synthesis process. We do believe that carbothermal reduction method (CRM) is a good process to reach the desired structure and morphology control when is desired to obtain 1D ITO, which is the main objective of this work. The CRM consists in generating indium and tin oxides in gas phase below its sublimation temperature due to the reducing characteristic of carbon mixed to the oxide. The SnO₂ was mixed with carbon black, the reducer used in this work, in molar proportion 1:1 and this mixture is placed in alumina boat. After, a mixture of In₂O₃ and carbon black in the same molar ratio was placed in other alumina boat. So, the boat with indium oxide was placed in the center of tubular furnace where the temperature was kept at 1150 °C, while the boat with tin oxide was placed in a region of tube where temperature was 850 °C. The extremities of tube were sealed and a flux of 100 sccm of N₂ was kept during the synthesis. The structure of the materials collected after the synthesis was analyzed by XRD and its morphology was analyzed using a FE-SEM and TEM. Preliminary results showed the resulting material is composed of nanowires of width between 100 nm to 400 nm and lengths of 50 µm to 600 µm. Moreover, it will be discussed the influence of the boats position inside the tube on the chemical composition of the final structures, which is important for practical applications. Reference: [1] K. L. Chopra, S. Major, D. K. Pandya, Transparent conductors – a status review, Thin solid films. 102 (1983) 1-46. (author)