Influence of Thermal Annealing on the Microstructural Properties of Indium Tin Oxide Nanoparticles

In this work, we studied the microstructural changes of ITO during the annealing process. ITO nanoparticles were prepared by the sol-gel method using indium tin hydroxide as the precursor. The prepared sample was investigated using TEM, powder XRD, XPS, DRIFT, and 2D correlation analysis. The 0 is XPS spectra suggested that the microstructural changes during the annealing process are closely correlated with the oxygen sites of the ITO nanoparticles. The temperature-dependent in situ DRIFT spectra suggested that In-OH in the terminal sites is firstly decomposed and, then, Sn-O-Sn is produced in the ITO nanoparticles during the thermal annealing process. Based on the 2D correlation analysis, we deduced the following sequence of events: 1483 (due to In-OH bending mode) -> 2268, 2164 (due to In-OH stretching mode) -> 1546 (due to overtones of Sn-O-Sn modes) -> 1412 (due to overtones of Sn-O-Sn modes) cm(-1).