LAUSR

Abstract Phase transformation of MnO 2 and Fe 2 O 3 roasted in air atmosphere at temperatures of 500–1400 °C for synthesizing manganese ferrite (Mn x Fe 3 − x O 4 ) has been reported. In current work, the morphologies and properties of the Mn x Fe 3 − x O 4 products with various x values during the synthesis process were characterized by XRD, XPS, SEM-EDS, AFM, VSM and Vickers-type microhardness analyses to further understand the formation mechanism of Mn x Fe 3 − x O 4 from MnO 2 and Fe 2 O 3 by solid-state reaction. Results showed that the x value in the Mn x Fe 3 − x O 4 gradually increased to 1 with the extension of roasting time from 30 min to 120 min at 1300 °C. Morphology measurements indicated the Mn x Fe 3 − x O 4 particles presented polyhedron structure and the shape of polyhedron particles gradually became regular with the increasing of x value. In addition, it's interesting to find that the polyhedron particles had multi-layer stacking structure and the thickness of each layer was about 5 nm. The saturation magnetization of the Mn x Fe 3 − x O 4 samples increased with the rising of x value. A polyhedral MnFe 2 O 4 (x = 1) product with saturation magnetization of 78.5 emu/g was obtained when the MnO 2 and Fe 2 O 3 briquettes with molar ratio of 1:1 were roasted at 1300 °C for 120 min. Moreover, the Hv hardness of the Mn x Fe 3 − x O 4 increased from 154.8 kg/mm 2 to 339.4 kg/mm 2 with elevating the temperature from 1000 °C to 1300 °C.