CPM Seminar

The Fe_1+xTi_2-xO₅, 0<x<1, solid solution series has been systematically investigated by means of X-ray diffraction, Mössbauer spectroscopy and neutron diffraction. The results confirm that the Fe_1+xTi_2-xO₅, 0<x<1, pseudobrookite series has orthorhombic structure, contains four molecules per unit cell and belongs to the space group D_2h¹⁷(Cmcm). The site occupancies fitted with both Mössbauer spectra and neutron diffraction data indicate that the cation, Fe²⁺, Fe³⁺ and Ti⁴⁺, distributions in the available sites, 4c and 8f, are random, although most (up to ∼70%) of the fourfold sites are preferred by either Fe²⁺ in FeTi₂O₅, Fe³⁺ in Fe₂TiO₅ or by both Fe²⁺ and Fe³⁺ in Fe_1+xTi_2-+xO₅. The assignments that the fourfold sites in less distorted oxygen octahedra are occupied by either Fe²⁺, Fe³⁺ or both of them with larger quadrupole splittings suggest that the Fe²⁺ in FeTi₂O₅ and Fe³⁺ in Fe₂TiO₅ are in high spin and low spin states, respectively. Good agreement between the site occupancies of Fe²⁺ obtained from Mössbauer analysis and neutron diffraction data suggest that the chemical reaction factor, i.e. stoichiometric ratio between the Fe²⁺ and Fe³⁺, plays an important role to govern the iron cation distribution both in the whole system and in the different sites.

Monday, April 26th 1999, 12:30
Ernest Rutherford Physics Building, Board Room