Clathrate formation in the systems Sr-Cu-Ge and {Ba,Sr}-Cu-Ge
- Author(s)
- I. Zeiringer, R. Moser, F. Kneidinger, R. Podloucky, E. Royanian, A. Grytsiv, Ernst Bauer, G. Giester, M. Falmbigl, P. Rogl
- Abstract
In the ternary system Sr-?Cu-?Ge, a novel clathrate type-?I phase was detected, Sr8CuxGe46-?x (5.2=x<5.4)?, which exists close to the Zintl limit in a small temp. interval. Sr8Cu5.3Ge40.7 decomps. eutectoidally on cooling at 730±3 °C into (Ge)?, SrGe2 and t1-?SrCu2-?xGe2+x. Phase equil. at 700 °C have been established for the Ge rich part and are characterized by the appearance of only one ternary compd., t1-?SrCu2-?xGe2+x, which crystallizes with the ThCr2Si2 structure type and forms a homogeneity range up to x=0.4 (a=0.42850(4)?, c=1.0370(1) nm)?. Addnl., the extent of the clathrate type-?I solid soln. Ba8-?ySryCuxGe46-?x (0=y=~5.6; 5.2=x=5.4, from as cast alloys) has been studied at various temps. The clathrate type-?I crystal structure (space group Pm3[n.773]?n) has been proven by X-?ray single crystal diffraction on two single crystals with the compn. (from refinement)?: Sr8Cu5.36Ge40.64 (a=1.06368(2) nm at 300 K) and Ba4.86Sr3.14Cu5.36Ge40.64 (a=1.06748(2) nm at 300 K) measured at 300, 200 and 100 K. From the temp. dependence of the lattice parameters and the at. displacement parameters, thermal expansion coeffs., Debye- and Einstein-?temps. and the speed of sound have been detd. From heat capacity measurements of Sr8Cu5.3Ge40.7 at low temps. the Sommerfeld coeff. (?=24 mJ?/mol K2) and the Debye temp. (TLTD=273 K) have been extd. From a detailed anal. of these data at higher temps., Einstein branches of the phonon dispersion relation have been derived and compared to those obtained from the at. displacement parameters. Elec. resistivity measurements of Sr8Cu5.3Ge40.7 reveal a rather metallic behavior in the low temp. range (<300 K)?. D. function theory calcns. provide densities of states, electronic resistivity and Seebeck coeff. as well as the vibrational spectrum and sp. heat.
- Organisation(s)
- Department of Physical Chemistry, Department of Mineralogy and Crystallography
- External organisation(s)
- Technische Universität Wien
- Journal
- Journal of Solid State Chemistry
- Volume
- 217
- Pages
- 169-179
- No. of pages
- 11
- ISSN
- 0022-4596
- DOI
- https://doi.org/10.1016/j.jssc.2014.05.014
- Publication date
- 09-2014
- Peer reviewed
- Yes
- Austrian Fields of Science 2012
- 104017 Physical chemistry, 105113 Crystallography, 104003 Inorganic chemistry, 104011 Materials chemistry
- Keywords
- ASJC Scopus subject areas
- Condensed Matter Physics, Inorganic Chemistry, Physical and Theoretical Chemistry, Ceramics and Composites, Electronic, Optical and Magnetic Materials, Materials Chemistry
- Portal url
- https://ucrisportal.univie.ac.at/en/publications/ab53be82-2160-48d6-aa8e-ff91c613e2fc