Abstract
The Mössbauer spectra of titanomagnetites, Fe3-xTixO4 (0≤x≤1), synthesized at 1200°C were redetermined to clarify the cation distribution in titanomagnetite. Nine samples from x=0 to x=0.33 were used in the experiments. The spectra were very distinct for samples between x=0 and x=0.20, and in that compositional range satisfactory fits were obtained with theoretical curves by nonlinear regression. Uncertainty in the fitting becomes a severe problem for x larger than 0.20, but the trend in the change of spectra can be traced nearly continuously from x=0 to x=0.33. The variation of the isomer shift with x suggests that the spectra can be divided into three subsets a, b, and c which are attributed to Fe3+ in A site, Fe2.5+ in B site (arising from the electron hopping between the Fe3+ and Fe2+ pair), and other iron ions with locally varying energy states, respectively. The change of the fractional area (fa) of subset a with composition shows that the cation distribution in the present samples follows the Akimoto model (AKIMOTO, 1954). This conclusion is in good agreement with the neutron diffraction study by WECHSLER et al. (1984). It was also concluded from the change of the fractional area (fb) of subset b that the proportion of Fe3+-Fe2+ pairs which participate in electron hopping is much less than expected from the model.
