Hydrothermal synthesis of NaxFexTi2-xO4 from natural ilmenite sand:: A CaFe2O4 structure type compound

NaxFexTi2-xO4 a compound from the CaFe2O4 structure type group, was obtained via hydrothermal route at a temperature lower than 200 degrees C for the first time. Natural ilmenite sand, a low cost reagent, was used as a precursor and reacted with 10 mol/l NaOH for 70 h to obtained high yield (92% wt) of NaxFexTi2-xO4 with x similar to 0.76-0.79, as evaluated through the Rietveld refinement and quantitative phase analysis of X-ray powder diffraction data. Transmission Electron Microscopy showed that NaxFexTi2-xO4 appears in submicron to micron crystals with well-defined facets, growing along the [001] crystallographic direction, which means that the tunnels, a peculiarity of this crystal structure, are oriented along the direction of growth. (C) 2007 Elsevier Ltd. All rights reserved.