A. Teresiak

Structure Relations and XRD Patterns of the Disorder-Order Transition of Metastable RE2TM17 Alloys

By using non-equilibrium methods and subsequent annealing, rare-earth transitionΠmetal-alloys with the nominal chemical composition 2:17 show a hexagonal metastable TbCu7 like structure. This disordered hexagonal (P6/mmm) metastable compound can be represented by a rhombohedral cell by using a cell transition of the hexagonal space group P6/mmm into the translationsgleiche subgroup P -31m (162) and subsequently into the klassengleiche subgroup II b R -3m. The atomic positions of the obtained rhombohedral cell correspond to appropriate coordinates in the hexagonal cell. In that way, a partial order of the 2:17 structure can be described. For the binary system Sm-Fe, a compound with similar structure and the formula SmFe8.5 exists. Examples are given for the obtained phases after ball milling the elemental powders Fe and Sm and subsequent annealing, and also after HDDR of Sm2Fe17.