Formation of manganese- and manganese,zinc-bearing ferrites by oxidation of aqueous suspensions and analysis of their cation distributions

摘要

Oxidized manganese-bearing and manganese,zinc-bearing ferrites have been prepared by air oxidation of iron(Ⅱ) hydroxide suspensions at initial Mn: Fe_(tot) mol ratios (r_(Mn)) of 0.20:2.80 to 1.40:1.60 and initial (Mn + Zn): Fe_(tot) mol ratios (r_(Mn+Zn)) of 0.20:2.80 to 1.00:2.00, respectively, at pH 10.0 and 65℃. Moessbauer spectra at room temperature and chemical analysis of the manganese-bearing ferrites suggest that Mn~(2+) ions are incorporated into the tetrahedral sites in the ferrites with manganese compositions of less than 0.74 and into both the tetrahedral and the octahedral sites at compositions of 0.74 to 1.06. In addition, manganese ions in a higher valence state than 3+ are incorporated into the octahedral sites at manganese compositions above 0.74. Moessbauer spectra at room temperature of the man-ganese,zinc-bearing ferrites prepared at r_(Mn+Zn) = 1.00:2.00 indicate that Mn~(2+) ions are incorporated on the lattice points in the ferrites and in both the tetrahedral and the octahedral sites at manganese compositions of 0.33 to 0.51. Moessbauer spectra and chemical analysis also suggest the incorporation of manganese ions in valence states higher than 3+. Moessbauer spectra and the lattice constants imply that the octahedral lattice sites in the ferrites with manganese compositions equal to or greater than 0.51 are distorted. Moessbauer spectra at room temperature of the manganese,zinc-bearing ferrites prepared at r_(Mn+Zn) = 0.20:2.80 to 0.80:2.20 suggest that Mn~(2+) ions are incorporated into both the tetrahedral and the octahedral sites in the ferrites, and that the amounts of Mn~(2+) ions on the octahedral sites increase with-increases in the manganese composition of the ferrites prepared at each r_(Mn+Zn) value.