Intermediate Phases in Some Rare Earth Metal-Iridium Systems

摘要

Crystal structures of all the possible phases encountered in several Ln-Ir(Ln = La, Ce, Nd, Gd, Y and Er) systems were investigated using powder X-ray diffraction technique and comparison with powder patterns of known phases in the Ln-Rh and Ln-Ru systems. Fe3C Mn5C2 Pu5Rh3 and MgCu2 type structures occur in most of these rare earth systems. The Th7Fe3-type structures occur only in the La and Ce systems with Ir. The CaCu5-type structure occurs in the Ir systems with light rare earths from La to Nd, unlike its occurrence only in the heavy rare earth-Rh systems. Ir behaves like Ru in the rare earth-rich alloys, but it shows more similarity with Rh in alloys having > 30 at % Ir. Mean atomic volume considerations indicate Ir-atom contractions in the rare earth-rich alloy phases, whereas the rare earth atoms seem to contract a lot in the Ir-rich phases. Ir seems to have slightly larger atomic volume in these Ir-rich alloy phases. Reprints. (JHD)