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Ternary systems Sr-{Ni,Cu}-Si: Phase equilibria and crystal structure of ternary phases |
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| Authors: | Navida Nasir Andriy Grytsiv Gerald Giester Gerhard E. Nauer |
| Affiliation: | a Institute of Physical Chemistry, University of Vienna, A-1090 Wien, Austria b Institute of Mineralogy and Crystallography, University of Vienna, Althanstrasse 14, A-1090 Wien, Austria c CEST-Kompetenzzentrum für elektrochemische Oberflächentechnologie GmbH Victor-Kaplan-Strasse 2, A-2700 Wr. Neustadt, Austria |
| Abstract: | Phase relations were established in the Sr-poor part of the ternary systems Sr-Ni-Si (900 °C) and Sr-Cu-Si (800 °C) by light optical microscopy, electron probe microanalysis and X-ray diffraction on as cast and annealed alloys. Two new ternary compounds SrNiSi3 (BaNiSn3-type) and SrNi9−xSi4+x (own-type) were found in the Sr-Ni-Si system along with previously reported Sr(NixSi1−x)2 (AlB2-type). The crystal structure of SrNi9−xSi4+x (own-type, x=2.7, a=0.78998(3), c=1.1337(2) nm; space group P4/nbm) was determined from X-ray single crystal counter to be a low symmetry derivative of the cubic, parent NaZn13-type. At higher Si-content X-ray Rietveld refinements reveal the formation of a vacant site (□) corresponding to a formula SrNi5.5Si6.5□1.0. Phase equilibria in the Sr-Cu-Si system are characterized by the compounds SrCu2−xSi2+x (ThCr2Si2-type), Sr(CuxSi1−x)2 (AlB2-type), SrCu9−xSi4+x (0≤x≤1.0; CeNi8.5Si4.5-type) and SrCu13−xSix (4≤x≤1.8; NaZn13-type). The latter two structure types appear within a continuous solid solution. Neither a type-I nor a type-IX clathrate compound was encountered in the Sr-{Cu,Ni}-Si systems.Structural details are furthermore given for about 14 new ternary compounds from related alloy systems with Ba. |
| Keywords: | Phase equilibria X-ray single crystal and powder diffraction Crystal chemistry of intermetallics |
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