Preparation of indium-tin oxide (ITO) nano-aciculae by a simple precipitation near boiling point and post-calcination method

ITO nano-aciculae (needle-like nanometer crystals) were prepared by post-calcination of ITO precursor nano-aciculae, which were synthesized by a simple precipitation near boiling point method. Transparent conductive film formed of ITO nano-aciculae was prepared by a simple coating process. ITO precursor nano-aciculae, ITO nano-aciculae and films were characterized with morphology, phase structure, optical and electrical properties, etc. The cross-sectional diameters of most of ITO nano-aciculae were mainly in the range of 20 to 60 nm, and the aspect ratios were mostly in the range of 4 to 12. Moreover, the ITO nano-aciculae had smaller cross-sectional diameters and bigger aspect ratios in comparison with the ITO precursor nano-aciculae on the whole. ITO precursor nano-aciculae were composed of very subtle nano-wires of 3 to 4 nm in cross-sectional diameter, and the nano-wires were regularly arranged to be parallel to the axial direction of ITO precursor nano-aciculae. However, ITO nano-aciculae were composed of caky subunits (flaky grain) whose flat surfaces were perpendicular to the axial direction. ITO precursor nano-aciculae were composed of In(OH)3 and Sn3O2(OH)2, and growth of nano-wires in ITO precursor nano-aciculae was along the [1 0 0] direction of In(OH)3. ITO nano-aciculae were ITO solid solution being not well-crystallized. ITO nano-aciculae were interlaced with each other and formed an alveolate meshwork (meshed texture). The average transmittance of the film was about 85% in a wide visible light range of 400 to 1000 nm, and the sheet resistance of the film was 4.3 kΩ/□. The ITO nano-aciculae film was used as low and middle-grade transparent conductive film.