Synthesis and Structure of YbCuGe and YbIrGe

Abstract

The equiatomic ytterbium–transition metal–germanides YbCuGe and YbIrGe were synthesized in single crystalline form from CuGe and IrGe master alloys and ytterbium via the Bridgman technique and they were characterized through their X-ray powder patterns. The structures were refined from X-ray single crystal diffractometer data: NdPtSb type, P63mc, a=421.36(8), c=703.9(1) pm, wR2=0.0234, 210 F2 values, 11 variable parameters, BASF=0.35(9) for YbCuGe and TiNiSi type, Pnma, a=671.09(6), b=421.55(5), c=757.16(7) pm, wR2=0.0782, 519 F2 values, 20 variable parameters for YbIrGe. The copper (iridium) and germanium atoms build up [CuGe] and [IrGe] networks. In YbCuGe the two-dimensional [CuGe] network consists of puckered layers of Cu3Ge3 hexagons (247 pm Cu–Ge) that are charge balanced and separated by the ytterbium atoms. In contrast, the ordered Ir3Ge3 hexagons show a strong orthorhombic distortion and the [IrGe] network is three-dimensional with a distorted tetrahedral germanium coordination around iridium with almost equal Ir–Ge distances (252–259 pm). The ytterbium atoms fill cages within this network. The cell volumes of YbCuGe and YbIrGe are indicative for purely trivalent ytterbium.