“Nanoscale Zippers” in the Crystalline Solid. Structural Variations in the Giant Magnetocaloric Material Gd5Si1.5Ge2.5

The magnetocaloric material Gd5Si1.5Ge2.5 has been synthesized and its crystal structures at 292 and 163 K are reported from single-crystal X-ray diffraction experiments. At room temperature, orthorhombic Sm5Ge4-type and twinned, monoclinic Gd5Si2Ge2-type phases coexist in single crystal specimens....

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Bibliographic Details
Published in:Chemistry of materials 2003-04, Vol.15 (7), p.1413-1419
Main Authors: Choe, Wonyoung, Miller, Gordon J, Meyers, John, Chumbley, Scott, Pecharsky, A. O
Format: Article
Language:English
Subjects:
Condensed matter: structure, mechanical and thermal properties
Exact sciences and technology
GADOLINIUM ALLOYS
GERMANIUM ALLOYS
Hydrides, borides, nitrides, etc., and metalloidal compounds
Inorganic compounds
MAGNETIC PROPERTIES
MATERIALS SCIENCE
MORPHOLOGY
NANOSTRUCTURES
Physics
SILICON ALLOYS
Structure of solids and liquids
crystallography
Structure of specific crystalline solids
VARIATIONS
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Summary:The magnetocaloric material Gd5Si1.5Ge2.5 has been synthesized and its crystal structures at 292 and 163 K are reported from single-crystal X-ray diffraction experiments. At room temperature, orthorhombic Sm5Ge4-type and twinned, monoclinic Gd5Si2Ge2-type phases coexist in single crystal specimens. This phenomenon is mainly due to the covalent bond breaking and formation of (Si,Ge)−(Si,Ge) dimers during the crystallographic phase transition. We suggest an atomic-level model for the interface of the two distinct domains. A detailed TEM analysis also confirms the coexistence of both phases in a polycrystalline sample. The structural relationship between such nanoscale zippers and other known phases is identified.
ISSN:0897-4756
1520-5002
DOI:10.1021/cm020928l