Indium–tin nanoscaled oxides synthesized under hydrothermal supercritical and postannealing pathway: Phase dynamics and characterization

Abstract With the aim of synthesizing the mixed nanoparticle system x In 2 O 3 –(1− x )SnO 2 over all molar concentration range 0 ≤  x  ≤ 1, Δ x  = 0.1, we performed hydrothermal supercritical experiments on indium–tin hydrogel resulted from InCl 3 –SnCl 4 water solution. Nanophases isostructural with InOOH and SnO 2 were obtained by hydrothermal reaction at 400 °C, in the molar concentration range of 0.1 ≤  x  ≤ 0.7; at x  = 0.8 and x  = 0.9 only one phase, isostructural with InOOH, was observed. Samples calcined at 500 °C with x in the range of 0.2 ≤  x  ≤ 0.7 contain a nanoscaled phase isostructural with rhombohedral In 2 O 3 and a second one isostructural with tetrahedral SnO 2 . At x  = 0.8 and x  = 0.9 only one phase isostructural with rhombohedral In 2 O 3 appears: rhombohedral ITO phase. The determined band gap energies could recommend the rhombohedral ITO structure for visible light photocatalytic applications. The phase dynamics together with the concentration range for existence of the solid solutions in the InOOH–SnO 2 and In 2 O 3 –SnO 2 composite semiconducting nanoparticle systems have been evidenced and discussed.