Small angle X-ray scattering studies on structural evolution during calcination of sol-gel ITO nano-powders

ITO nano-powders are prepared by sol-gel method followed by a calcination process. The microstructure responses with thermal treatments are performed by the control of annealing temperature and holding time, and the structures are characterized by small angle X-ray scattering (SAXS) and X-ray diffraction (XRD) technique. It is found that, the structural evolution shows different characters at low temperature (≤800 °C) and high temperature (>800 °C). At low temperature, sample is densified and has a transition from a hierarchical to a surface fractal structure due to the diffusion and elimination of interaggregate pores with increasing annealing time or temperature. At high temperature, samples all show surface fractal structures at whole length scale and the surface roughness increases due to the growth of crystalline grains with increasing annealing temperature, in contrast the roughness is slowly decreased because of the diffusion along the crystalline boundary with holding time.