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The Phase Co(1)(-)(x)()Ni(x)()Sn(2): Structural Variations Based on the Stacking of Two Different Planar Nets
Ulrich Häussermann1, Angel R. Landa-Cánovas, Sven Lidin
1Department of Inorganic Chemistry 2, Lund University, P.O. Box 124, S-22100 Lund, Sweden.
Inorganic Chemistry
|October 24, 2001
Summary
The Co/Ni/Sn system forms Co(1-x)Ni(x)Sn(2) with two crystal structures depending on synthesis conditions. Tin-rich melts yield a tetragonal PdSn(2)-type structure, while stoichiometric mixtures or higher temperatures produce an orthorhombic CoGe(2)-type structure.
Area of Science:
- Materials Science
- Solid State Chemistry
- Crystallography
Background:
- The Co/Ni/Sn ternary system is explored to understand phase formation and structural properties.
- Investigating tin-rich compositions is crucial for identifying novel intermetallic compounds.
Purpose of the Study:
- To characterize the Co(1-x)Ni(x)Sn(2) phase within the Co/Ni/Sn ternary system.
- To determine the crystal structures and formation conditions of different Co(1-x)Ni(x)Sn(2) polymorphs.
Main Methods:
- Single-crystal X-ray diffraction was used to determine the atomic structures of Co(0.625)Ni(0.375)Sn(2).
- Electron diffraction and high-resolution electron microscopy were employed to study stacking variants and faults.
Main Results:
- The Co(1-x)Ni(x)Sn(2) phase exists for 0.23 < x < 0.59.
- Two distinct crystal structures were identified: tetragonal PdSn(2)-type (from tin-rich melts) and orthorhombic CoGe(2)-type (from stoichiometric mixtures or higher temperatures).
- Both structures share a common building unit of tin nets, differing in stacking sequences (ABCD vs. AB).
Conclusions:
- The synthesis conditions significantly influence the crystal structure of Co(1-x)Ni(x)Sn(2).
- Complex stacking sequences and stacking faults were observed, highlighting the structural complexity of this system.