Crystal structure refinements of In x Fe3−x O4(x ≤ 0.3) spinels by the Rietveld method

The distribution of In3+ between tetrahedral and octahedral sites and coordinate of oxygen in In x Fe3−x O4 (x = 0, 0.1, 0.2, and 0.3) spinels have been determined on powder samples by the Rietveld method. The weight function with a form wYi = l/Yoi 2 (Yoi = the observed profile intensity at the ith step) was incorporated in the present Rietveld refinement. Structures thus refined were satisfactory not only in their internal consistency but also in their conformity with single crystal data. These results corroborate earlier study, which indicated a preference of In3+ for the tetrahedral site. ivIn–O distances in the present specimens [1.97(3) Å–2.00(5) Å] were close to the value calculated from a bond-valence scheme. In In x Fe3−x O4, calculated viFe2+–O distances increased with increasing x, and they were in between two viFe2+–O distances in Fe3O4 and γ-Fe2SiO4 (spinel structure). A change of semimetallic nature to semiconductive one by In-doping in Fe3O4 would be responsible for the elongation of viFe2+–O distance.