Abstract: SrFeO3-δ products with microcube-shaped tetragonal type, and nano lamellae-shaped brounmillerite and orthorhombic mixed type were successfully synthesized by a molten salt route through controlling temperature and time and lid-closure reaction. The synthesized products were systematically studied by X-ray powder diffraction, field-emission scanning electron microscopy, transmission electron microscopy, and energy dispersive X-ray spectroscopy as well as thermogravimetric analysis. The results show that the sample SrFeO2.86 has a tetrahedral symmetry with I4/mmm supercell. Evidence of weak superstructures, reflecting local oxygen ordering, is also obtained from electron diffraction. SrFeO2.62 was found to be a composite material by combination of a brownmillerite phase with Ibma space group and an orthorhombic structure with Cmmm space group. The results of magnetic properties indicate that the morphology of the SrFeO3-δ products has great effects on their properties. Reduced spin frustration is associated with an increasing ferromagnetic interaction. The shape anisotropy results in distinct difference of magnetic properties in different oxides with nearly the same composition.

Key words: Perovskite, Nanometer, Molten salts, Magnetism