Interstitial positions of tin ions in α-(${\mathrm{Fe}}_{\mathrm{rich}}$Sn${)}_2$${\mathrm{O}}_3$ solid solutions prepared by mechanical alloying

The microstructure of samples of 94, 85, and 71 mol % α-${\mathrm{Fe}}_2$ ${\mathrm{O}}_3$-${\mathrm{SnO}}_2$, prepared by mechanical alloying, has been studied by x-ray diffraction with Rietveld structure refinements. On the basis of the structure refinements to the whole x-ray diffraction patterns for the four as-milled samples, it is found that tin ions do not substitute iron ions in the solid solution, although this model is generally assumed in the literature. The ${\mathrm{Sn}}^{4+}$ ions occupy the empty octahedral holes in the lattice of the α-${\mathrm{Fe}}_2$ ${\mathrm{O}}_3$ phase.