YPdSn and YPd2Sn: Structure, 89Y solid state NMR and 119Sn Mossbauer spectroscopy

The stannides YPdSn and YPd2Sn were synthesized by high-frequency melting of the elements in sealed tantalum tubes. Both structures were refined on the basis of single crystal X-ray diffractometer data: TiNiSi type, Pnma, a=715.4(1), b=458.8(1), c=789.1(1) pm, wR2 = 0.0461, 510 F-2 values, 20 variables for YPdSn and MnCu2Al type, Fm (3) over barm, a = 671.44(8), wR2 =0.0740, 55 F-2 values, 5 parameters for YPd2Sn. The yttrium atoms in the new stannide YPdSn are coordinated by two tilted Pd3Sn3 hexagons (ordered AlB2 superstructure). In the Heusler phase YPd2Sn each yttrium atom has octahedral tin coordination and additionally eight palladium neighbors. The cubic site symmetry of yttrium is reflected in the Sn-119 Mossbauer spectrum which shows no quadrupole splitting. In contrast, YPdSn shows a single signal at delta = 1.82(1) mm/s subjected to quadrupole splitting of Delta E-Q = 0.93(1) mm/s. Both compounds have been characterized by high-resolution Y-89 solid state NMR spectroscopy, which indicates the presence of strong Knight shifts. The spectrum of YPd2Sn is characterized by an unusually large linewidth, suggesting the presence of a Knight shift distribution reflecting local disordering effects. The range of Y-89 Knight shifts of several binary and ternary intermetallic yttrium compounds is briefly discussed. (C) 2012 Elsevier Inc. All rights reserved.