THE PHASE-DIAGRAMS OF THE SC-SN AND SC-PB SYSTEMS

The phase diagrams of the Sc-Sn and Sc-Pb systems have been investigated using differential thermal analysis (DTA), metallographic analysis, X-ray diffraction (XRD) and electron microscopy. The Sc-rich side of both systems (0-30 at.% Sn or Pb) has not been studied owing to the high melting temperatures of the corresponding alloys and contamination of the samples by the container material (Mo). The two systems are very similar to one another; with tin, however, two more intermediate phases are formed. Sc(5)X(3) and Sc(6)X(5) compounds are isomorphous, Mn5Si3 and Ti6Ge5 types respectively. ScSn2 is a new intermetallic compound with a new structure type. The impossibility of finding single crystals for XRD prevented the determination of the structure and then of the exact stoichiometry for ScSn which was assigned taking into account the results of DTA, XRD, optical and electronic microanalysis. Sc(5)X(3), different from the other intermediate phases, shows appreciable solid solution range towards compositions richer in X.