Phase relations in the Sm2O3-Fe2O3 system: Structure and magnetic properties of perovskite SmFeO3 ceramics

The phase relations in the Sm 2 O 3 –Fe 2 O 3 system at 1300 and 1400°C were studied in the whole concentration range by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The samples were prepared with a concentration step of 1–5 mol %. The isothermal cross-sections of the Sm 2 O 3 –Fe 2 O 3 phase diagram at 1300 and 1400°C are characterized by the presence of four single-phase (B–Sm 2 O 3 , SmFeO 3 (R), Sm 3 Fe 5 O 12 , Fe 2 O 3 ), three two-phase (B–Sm 2 O 3 +SmFeO 3 , SmFeO 3 + Sm 3 Fe 5 O 12 , Sm 3 Fe 5 O 12 +Fe 2 O 3 ) regions. The refined lattice parameter of the unit cell and the boundaries of the homogeneity fields for solid solutions were determined. The range of homogeneity of solid solutions based on the R-phase extends from 49 to 52 mol % Sm 2 O 3 at 1300 and 1400 °C. Nanocomposites based on the perovskite phase (SmFeO 3 ) were obtained by the Pechini method and heterogeneous precipitation from nitrate solutions. The influence of the production method on the microstructure, morphology, and magnetic properties of nanopowders (SmFeO 3 ) was studied. According to XRD, infrared spectroscopy, SEM, the synthesized perovskite SmFeO 3 is single-phase with a particle size of 50-60 nm. The morphology of powder particles primarily depends on the method of material synthesis. The powders display superparamagnetic-like loops at 300 K, typical of nanoparticle ensembles.