Structural modification of doped and undoped nanocrystalline TiO2 by temperature-resolved XRPD

Nanocrystalline titania pigments were produced by a novel synthesis route consisting of a high temperature forced hydrolysis in a coordinating high-boiling solvent. The effect of synthesis conditions as well as doping with Cr, Sb and V on the particle size and on the anatase-to-rutile transformation was studied by temperature-resolved synchrotron powder diffraction. The experiments were performed directly on as-synthesized low concentration suspensions of titania nanoparticles (up to 230°C) and on dried titania nanoparticles (up to 950°C). Crystallite size of as-synthesized nanoparticles is in the 5 to 50 nm range, being affected by the synthesis conditions as well as by doping and exhibits a slow-rate coarsening trend with temperature. The anatase-to-rutile transformation is drastically influenced by both synthesis conditions and doping. In particular, doping affected the anatase-to-rutile transformation rate, while the synthesis conditions influenced the phase composition, causing the appearance of brookite.