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Struktur und Dynamik Poster: Mi., 14:00–16:30 M-P133
Microheterogeneous atomic structure of liquid Cu-Sn alloys
S. Gruner 1 , I. Kaban 1 , R. Kleinhempel 1 , W. Hoyer 1
1 Chemnitz University of Technology, Institute of Physics, D-09107 Chemnitz
In the solid state, Cu-Sn alloys exhibit a number of intermetallic phases. Structuresensitive
properties such as the dynamic viscosity and the electrical conductivity show
a non-monotonous composition dependence with maxima at the compound’s composition.
Assuming that the interactions between the atoms in these alloys are basically
unchanged when heating to the liquid state, on can expect signs of cluster formation
similar to the corresponding intermetallic phases in the liquid state. Thus, a detailed
study on the structure of liquid Cu-Sn alloys over the entire concentration range is
presented in this work.
The samples under investigation have been prepared from granules of the pure elements
Cu and Sn (purity 99.999 %). The X-ray diffraction experiments have been performed
using a high-temperature θ-θ-Diffractometer at the TU Chemnitz as well as at the
BW5 experimental station [1] at HASYLAB at DESY, Hamburg. Neutron diffraction
has been done at the SLAD diffractometer [2] at the Neutron Research Laboratory
NFL Studsvik, Sweden.
The course of the analysis of the diffraction data followed two major techniques: (i) the
coherently scattered X-ray intensities for numerous samples over the whole composition
range were evaluated with the model of micro-inhomogeneous structure as proposed by
Il’inskii and co-workers [3]; (ii) samples with selected compositions were investigated
by means of X-ray and neutron scattering at a temperature near the liquidus line.
The results of these scattering experiments have been used to derive partial correlation
functions by using the reverse Monte Carlo (RMC) method [4]. Partial co-ordination
numbers as well as short-range ordering parameters have been calculated.
Using the example of the Cu6Sn5 alloy it was shown by comparison with partial structure
factors determined from neutron scattering using isotopic substitution [5] that
simultaneous RMC-modelling of two total structure factors obtained from X-ray and
neutrondiffraction yield reliable pair correlation functions. Both, the evaluation following
Il’inskii’s model as well as the RMC modelling suggest a heterogeneous structure
and confirm the existence of clusters of the Cu3Sn-stoichiometry.
[1] H. F. Poulsen, J. Neuefeind, H.-B. Neumann, J. R. Schneider, M. D. Zeidler, J.
Non-cryst. solids 188 (1995) 63
[2] A. Wannberg et. al., J. Neutron Res. 8 (1999) 133
[3] A. G. Il’inskii, L. E. Mikhajlova, A. V. Romanova, A. V. Rosenfeld, W. Hoyer,
Magnetic and Electronic Properties of Materials, vol. 2, Naukova Dumka Kiev 1990,
p. 75
[4] R. L. McGreevy, L. Pusztai, Mol. Simul. 1 (1988) 359
[5] J. E. Enderby, D. M. North, P. A. Egelstaff Phil. Mag. 14 (1966) 961