Urea-based hydrothermal synthesis of ITO nanopowders

Abstract

Nanosized tin-doped indium oxide (ITO) powders were prepared by hydrothermally treating either the coprecipitated hydroxides of tin and indium gels with the addition of a small amount of urea or the solution of indium and tin aqueous salts in presence of urea at 240°C for about two days followed by calcination at 600°C for one hour. The effect of urea in the two different processing routes on the crystal structure and morphology of the ITO nanopowders has been investigated. Weakly-aggregated nanosized ITO powders with the uniform spherical morphology were obtained by the calcination of the hydrothermally treated coprecipitated indium and tin gels with 10 wt.% urea. However, by directly using urea as an alkaline solution during the hydrothermal treatment, the obtained ITO powders exhibit a composite morphology consisting of spheres and rods. Both of the processing routes yield a two-phase mixture consisting of rhombohedral and cubic forms of ITO.