FORMATION OF MANGANESE-BEARING AND MANGANESE,ZINC-BEARING FERRITES BYOXIDATION OF AQUEOUS SUSPENSIONS AND ANALYSIS OF THEIR CATION DISTRIBUTIONS

Oxidized manganese-bearing and manganese,zinc-bearing ferrites have be en prepared by air oxidation of iron(II) hydroxide suspensions at init ial Mn:Fe-tot mol ratios (r(Mn)) of 0.20:2.80 to 1.60:1.60 and initial (Mn + Zn):Fe-tot mol ratios (T-Mn+Zn) of 0:20:2 80 to 1.00:2.00, resp ectively, at pH 10.0 and 65 degrees C. Mossbauer spectra at room tempe rature and chemical analysis of the manganese-bearing ferrites suggest that Mn2+ ions are incorporated into the tetrahedral sites in the fer rites 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 inco rporated into the octahedral sites at manganese compositions above 0.7 4. Mossbauer spectra at room temperature of the manganese,zinc-bearing ferrites prepared at r(Mn+Zn) = 1 00:2 00 indicate that Mn2+ ions are incorporated on the lattice points in the ferrites and in both the te trahedral and the octahedral sites at manganese compositions of 0.33 t o 0.51. Mossbauer spectra and chemical analysis also suggest the incor poration of manganese ions in valence states higher than 3+. Mossbauer spectra and the lattice constants imply that the octahedral lattice s ites in the ferrites with manganese compositions equal to or greater t han 0.51 are distorted. Mossbauer spectra at room temperature of the m anganese,zinc-bearing ferrites prepared at r(Mn+Zn) = 0 20:2.80 to 0.8 0:2.20 suggest that Mn2+ ions are incorporated into both the tetrahedr al and the octahedral sites in the ferrites, and that the amounts of M n2+ ions on the octahedral sites increase with increases in the mangan ese composition of the ferrites prepared at each r(Mn+Zn) value.