Crystal structure of ytterbium copper stannides in the range 14–32 at.% tin

The crystal structures of four new intermetallic compounds of the Yb-Cu-Sn system were determined by X-ray diffraction on powders and single crystals and by optical and electron microscopy: Yb 3.63Cu 23.13Sn 10.83 - hexagonal, P6/mmm, hP50-12.41, a=1195.7(2) pm, c=516.2(1) pm, R=0.022, 402 reflections, has a new structure with a disordered part localised in channels parallel to the six-fold axis and centred at the origin of the unit cell; YbCu 9Sn 4 - tetragonal, I4/mcm, tI56, a=861.7(1) pm, c=1239.2(2) pm, R=0.021, 325 reflections, is isotypic with LaFe 9Si 4, ordered ternary derivative of the cubic NaZn 13 type; Yb 7.2Cu 10Sn 8 - hexagonal, P6 3/mmc, hP26-0.8, a=453.0(1) pm, c=3042.3(5) pm, R=0.055, 233 reflections, and Yb 14.4Cu 18Sn 15 - trigonal, R 3 ¯ m , hR48-0.6, a=451.9(1) pm, c=5664(1) pm, R=0.050, 263 reflections. The structures of the last two phases are built up by different stacking of the same units, taken from the GdPt 2Sn and SrPtSb (ordered AlB 2) types. In the Cu-rich alloys containing 10 to 28 at.% tin, compounds were found with the atomic arrangements of the orthorhombic CeCu 5Au, Ce 2Cu 9Sn 2.65 and hexagonal CeNi 5Sn types