Rare earth–germanium and –silicon compounds at 5:4 and 5:3 compositions

Abstract

Thirteen new rare earth germanides and eleven new rare earth silicides of 5:4 stoichiometry have been prepared. Lattice constants and structure-types have been determined, principally by single-crystal techniques. For the RsGe4 compounds, all of the lanthanide elements studied show the orthorhombic 5 : 4 phase previously found for SmsGe4. (Rare earth metals not studied were Pm, Eu and Yb; in addition to these, Ho and Tm were not studied in the RsSi4 series.) The situation for the analogous silicon compounds is more complex. TbsSi4, DysSi4, ErsSi4 and YsSi4 crystallize with the SmsGe4-type structure; Sm and Gd probably do also, although no single crystals were obtained from these two preparations. LasSi4, CesSi4, PrsSi4 and NdsSi4 form tetragonal crystals, possibly of the ZrsSi4 type, whereas LusSi4 exhibits a monoclinic distortion of the orthorhombic phase. CesSi3 and PrsSi3 were found to form tetragonal crystals of the CrsB3 structure type. Powder-pattern data in the literature for LasSi3 could also be indexed on the basis of this structure type.