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On the Brass- and Silver-Colored Forms of PtGa2

Published online by Cambridge University Press:  15 February 2011

B. Morosin  and
D. Swenson
B. Morosin
Affiliation:
Sandia National Laboratories, Org. 1153, MS 1421, Albuquerque, NM 87185–1421
D. Swenson
Affiliation:
Materials Science Program, University of Wisconsin, 1509 University Avenue, Madison, WI 53706; currently at Department of Metallurgical and Materials Engineering, Michigan Technological University, 1400 Townsend Drive, Houghton, MI 49931–1295
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Abstract

PtGa2 has previously been reported to exist as both a brass-colored, fluorite-structured phase and as a silver-colored alloy of unknown crystal structure. The crystal structure of the silver-colored form is reported here, along with a discussion of the stoichiometric factors responsible for the polymorphy of this phase. The silver-colored form belongs to the space group 141/acd, with the lattice parameters a = 8.5544(4) and c = 21.574(17) Å, and Z = 32. The structure consists of layers of Pt and Ga stacked along the c axis, in which two crystallographically different Pt and Ga atoms have similar environments involving eight and nine nearest neighbors, respectively. This structural arrangement may be the prototype for a family of ternary platinum metal-Group B-based phases. The present investigation also necessitates changes in the currently accepted Ga-Pt phase diagram. Stoichiometric PtGa2 undergoes a structural transformation upon cooling from a brass-colored fluorite structure to this silver-colored, tetragonal structure. However, the transformation is inhibited if the composition of the fluorite-structured phase is Ga-poor.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 453: Symposium R – Solid State Chemistry of Inorganic Materials , 1996 , 373
Copyright
Copyright © Materials Research Society 1997

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References

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