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Abstract:
Ternary samples with the composition Yb(Cu,Ag,Au,Pd,Pt)xGa4-x have been
synthesized from the elements by high frequency melting followed by heat
treatment at 600-degrees-C.
The crystal structure of all compounds was investigated using X-ray
single-crystal or powder techniques and belongs to the BaAl4 type of
structure. The homogeneity regions of the Yb(Cu,Ag,Au,Pd,Pt)xGa4-x
phases have been established from X-ray powder diffraction analyses and
lie in the range x = 0.30-0.95 for Cu, 0.25-0.43 for Ag, 0.22-1.45 for
Au, 0.23-0.65 for Pt and near x = 0.25 for Pd. The unit cell dimensions
vs. composition reveal a significant deviation from Vegard's rule for Cu
and Au and a slight deviation for Ag and Pt. A partially ordered
occupation of the 4d and 4e sites in the BaAl4 structure type has been
found depending on the M/Ga ratio in the homogeneity range.
The weak temperature-dependent paramagnetism of these compounds is due
to the non-magnetic ground state of ytterbium (Yb2+). However, for
YbPt0.5Ga3.5 a rather intermediate valence behaviour (Yb2+ --> Yb3+) is
encountered.
