Structural and Electrical Properties of Iron Manganite Spinels in Relation with Cationic Distribution

摘要

Single-phase iron manganite spinels, Mn_(3-x)Fe_xO_4 with O ≤ x ≤ 1.05, were prepared by thermal processing of iron-manganese co-precipitated formate precursors. Powder X-ray diffraction (XRD) analysis shows a cubic-tetragonal transition for x = 1.05. The Mossbauer spectroscopy indicates the presence of only trivalent iron ions in both sites of the spinel structure. The electrical measurements show that these iron manganites have the characteristics of negative temperature coefficient thermistors. Moreover, in these solid solutions, the resistivity p decreases with increasing of iron content x. Correlation of the results obtained by XRD, Mossbauer spectroscopy and electrical measurements permits one to infer the cationic distribution, given by Mn_(1-y)~(2+) Fe_y~(3+) (Fe_z~(3+) Mn_(2-x)~(3+) Mn_y~(2+)) O_4~(2-) with x = y + z.