Low-temperature sintering behavior of nanocrystalline indium tin oxide prepared from polymer-containing sols

Indium tin hydroxide (ITH) xerogel powders and thin films with different polyvinylpyrrolidone (PVP) contents (0–22%, w/w) were prepared by a classical sol–gel method. To obtain nanocrystalline indium tin oxide (ITO), the ITH xerogels were calcined at 550 °C. The effect of the initial polymer content on the structure of the ITO powders was studied by means of N2-sorption measurements, small-angle X-ray scattering (SAXS), transmission and scanning electron microscopy. The N2-sorption measurements revealed that the ITO powders obtained contained micropores and both their porosity and specific surface area decreased with increasing PVP content of the ITH xerogels. The SAXS measurements confirmed the enhanced sintering of the particles in the presence of PVP. The calculated mass fractal dimensions of the ITO powders increased significantly, indicating a significant compaction in structure. The pre-sintered structure could be achieved at relatively low temperature, which induced a significant decreasing (three orders of magnitude) in the electrical resistance of the ITO films.