Preparation of indium-tin oxide (ITO) aciculae by a novel concentration-precipitation and post-calcination method

Indium-tin oxide (ITO) aciculae were prepared by adding tin into indium hydroxide aciculae, which were synthesized by a concentration-precipitation method, and subsequent calcining. X-ray powder diffraction (XRD) indicated that indium hydroxide aciculae were partially crystallized and ITO aciculae were a well-crystallized solid solution, and both of them had a cubic structure. Using scanning electron microscope (SEM), it was found that the cross-sectional diameters of most of ITO aciculae were in the range of 2 to 9 μm, and the aspect ratios of about 95% of aciculae were more than 6. Energy dispersion spectrometer (EDS) and phenylfluorone spectrophotometry analysis were used to measure Sn content of ITO aciculae, and it was revealed that the Sn content of the surface layer was higher than that of the bulk. Thermogravimetric analysis (TGA) and differential thermal analysis (DTA) showed that the intensive dehydration of In(OH)3 took place in the temperature rage of 260–280 °C and the formation of ITO solid solution started at temperature higher than 280 °C. According to the results of XRD, TGA–DTA and N content analysis, indium-containing nitrates or nitrites maybe existed in indium hydroxide aciculae. The specific resistance of the pellet formed by pressing ITO aciculae at a pressure of 10 MPa was measured by a four-probe method at room temperature, and it was as low as 1.2×10−2 Ω cm.