A Mossbauer effect study of Fe3+ bearing γ-Fe2SiO4

Three synthetic Fe3+ bearing gamma -Fe2SiO4 were analyzed using electron probe method, and the Mossbauer spectra of the samples at 298 K, 150 K, and 95 K were measured. Each spectrum at three temperatures is composed of two doublets. These two doublets are assigned to Fe2+ in the octahedral sites and Fe3+ in the tetrahedral sites, respectively. Site occupancies were determined. The results show that Fe3+ and a small amount of Si4+ are in the tetrahedral and octahedral sites, respectively. The average bond lengths of the octahedral and tetrahedral sites were calculated according to the equations primarily given by Hill et al., O'Neill and Navrotsky and modified by the authors. Furthermore, the octahedral and tetrahedral bond lengths were used to calculate cell parameters and oxygen parameters. In addition, Fe3+ line broadening in the Mossbauer spectra of Fe3+ bearing gamma -Fe2SiO4 were interpreted by using the next nearest neighbor effects.