Freeze-drying was used to obtain a homogeneous fine powder containing (CH3COO)(2)Mn-2H2O and ct-Fe2O3 (molar ratio Fe:Mn = 3: 1), which was thermally treated for 2 h in N-2 atmosphere, at 400 degrees C. This composite system was further annealed for 4 h in the same atmosphere, either at 700 degrees C or at 1000 degrees C. The 700 degrees C annealed sample was thermally treated in air at 1200 degrees C and then rapidly quenched. The phase transformations that occurred in the freeze-dried and heat-treated powders were investigated by thermal analyses, X-ray diffractometry, scanning electron microscopy and Mossbauer spectroscopy. Results showed that MnO-alpha-Fe2O3-Fe3O4 compounds were obtained after the first heat-treatment. Samples subsequently annealed in N atmosphere revealed the formation of Fe-rich manganese ferrites and manganowUstite phases. However, a single spinel phase was obtained for the sample that had been annealed and quenched in air. (c) 2007 Elsevier B.V. All rights reserved.