Crystal structure and cation distributions in the FeTi2O5-Fe2TiO5 solid solution series

The Fe1+xTi2-xO5, 0 less than or equal to x less than or equal to 1, solid solution series has been systematically investigated by means of x-ray diffraction, Mossbauer spectroscopy and neutron diffraction. The results confirm that the Fe1+2Ti2-xO5, 0 less than or equal to x less than or equal to 1 pseudobrookite series has an orthorhombic structure with the D-2h(17) (Cmcm) space group. The unit cell contains four formula units. The site occupancies obtained from both Mossbauer spectra and neutron diffraction data indicate that the cation (Fe2+, Fe3+ and Ti4+) distributions in the available sites, 4c and 8f, are neither random nor perfectly ordered. At x = 0, most of the iron is in the 4c site, and the 8f site fills progressively as x --> 1. The agreement between the Mossbauer and neutron site occupancies indicates that the Fe3+ and Fe2+ site preferences are the same.