Structural and thermal characterization of Sm₃Nbo₇ obtained by high energy milling

Samarium oxide (Sm₂O₃) and metallic Niobium (Nb) elementary powders were submitted to Mechanical Alloying technique and their structural evolution was investigated by X Ray Diffraction (XRD) measurements, Rietveld method and DSC. It was observed that after 2 hours of milling the precursor materials reached crystals with a mean size of 14 nm. New peaks emerge after 17 hours, revealing an unexpected high-temperature Sm₃NbO₇ phase overlapped with an amorphous phase. The Sm₃NbO₇ phase is normally obtained in a sintering process at temperatures above 1000 ° C.In our knowledge, is the first time that this phase was obtained at a temperature near to the ambient. In order to investigate its thermal stability, the sample was submitted to thermal analysis with DSC. Thus, thermal treatments were performed at 800 ° C and 1100 ° C. Was observed an increase of the crystallites of Sm₃NbO₇ at least 1100°C at the expense of the amorphous phase. Future work involves Density Functional Theory in order to understand energetically and thermodynamically the ambient nucleation temperature. (author)