Crystal structure and transport properties of Ba8Ge43square3.
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.
Aydemir
U
U
Max-Planck-Institut für Chemische Physik fester Stoffe, Nöthnitzer Str. 40, 01187, Dresden, Germany.
Candolfi
C
C
Borrmann
H
H
Baitinger
M
M
Ormeci
A
A
Carrillo-Cabrera
W
W
Chubilleau
C
C
Lenoir
B
B
Dauscher
A
A
Oeschler
N
N
Steglich
F
F
Grin
Yu
Y