Synthesis and Crystal Structures of New RRuxGa1-x (R = Er, Tm, Lu) Gallides and R2Ru1-xIn1+x (R = Dy, Ho, Er, Tm, Lu) Indides

A number of new intermetallic compounds of variable composition, RRuxGa1- x (R = Er, Tm, Lu) and R-2 Ru1 - xIn1+ x (R = Dy, Ho, Er, Tm, Lu), whose structures belong to known structure types, have been identified in a systematic study of R-Ru-Ga and R-Ru-In systems in their rare-earth-rich region. The Ga and Ru atoms in the RRuxGa1- x intermetallic phases with the CsCl structure (Pm (3) over barm) occupy the Cs site at random. The R2Ru1 - xIn1 + x compounds have the Pt2ZnCd structure (P4/mmm), derived from the CsCl structure via doubling of its c cell parameter, and the Ru and In atoms in these compounds occupy the Cs site in an ordered manner. All of the synthesized compounds have a homogeneity range, whose extent is highly dependent on the nature of the RE element. In the R-Ru-Ga (R = Er, Tm) systems, we have identified new compounds with the general formula RRuyGa1 - y and the MoB structure (I4(1)/amd), which is in turn derived from the CrB structure type (Cmcm). The homogeneity range of the RRuyGa1 - y intermetallic phases with the MoB structure is 0.05 < y < 0.20.