Dalton Trans. 2010 Jan 28;39(4):1078-88. doi: 10.1039/b919726e. Epub 2009 Dec 14.

Crystal structure and transport properties of Ba8Ge43square3.

Dalton transactions (Cambridge, England : 2003)

U Aydemir, C Candolfi, H Borrmann, M Baitinger, A Ormeci, W Carrillo-Cabrera, C Chubilleau, B Lenoir, A Dauscher, N Oeschler, F Steglich, Yu Grin

PMID: 20066194 DOI: 10.1039/b919726e

Abstract

The single phase clathrate-I Ba(8)Ge(43)square(3) (space group Ia3d (no. 230), a = 21.307(1) A) was synthesized by quenching the melt between cold steel plates. Specimens for physical property measurements were characterized by microstructure analysis and X-ray diffraction on polycrystalline samples as well as single crystals. Transport properties including thermopower, electrical resistivity, thermal conductivity and specific heat were investigated in a temperature range of 2-673 K. The electrical resistivity exhibits a metal-like temperature dependence below 300 K turning into a semiconductor-like behaviour above 300 K. The analysis of the specific heat at low temperature indicates a finite density of states at the Fermi level, thus corroborating the metallic character below 300 K. The temperature dependence of the specific heat was modelled assuming Einstein-like localized vibrations of Ba atoms inside the cages of the Ge framework. A conventional crystal-like behaviour of the thermal conductivity with a low lattice contribution (kappa(l)(300 K) = 2.7 W m(-1) K(-1)) has been evidenced.

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