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The dynamics of the guests in filled germanium clathrates
Hermann, Raphaël; Grandjean, Fernande; Keppens, V. et al.
2006In Mater. Res. Soc. Symp. Proc. Vol. 886
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Abstract :
[en] In the filled gallium-germanium clathrates, R8Ga16Ge30, where R is Ba, Sr, or Eu, the guests are located in two large cages and are weakly bound to the crystalline clathrate framework. The caged guests exhibit a localized "rattling" vibrational mode that provides an efficient mechanism for reducing the thermal conductivity. Inelastic neutron scattering and nuclear inelastic scattering measurements have yielded the phonon density of states in R8Ga16Ge30; the line width of the localized vibrational modes is found to be an important parameter in determining the lattice thermal conductivity. Neutron diffraction studies on R8Ga16Ge30 have shown that the guests in the larger cage are located off-center, and it was proposed that their jumping about the four off-center locations is responsible for the observed glass-like thermal conductivity at temperatures below 10 K. The detection of such slow guest motion is challenging because the typical time and energy scales involved are ca. 4 ns and 1 mu eV, respectively. We have studied the slow europium tunneling dynamics in Eu4Sr4Ga16Ge30 by both Mossbauer and microwave absorption spectroscopy.
Disciplines :
Materials science & engineering
Electrical & electronics engineering
Physics
Author, co-author :
Hermann, Raphaël ;  Université de Liège - ULiège > Département de physique > Département de physique
Grandjean, Fernande ;  Université de Liège - ULiège > Département de physique > Département de physique
Keppens, V.
Schweika, W.
Nolas, G. S.
Mandrus, D. G.
Sales, B. C.
Christen, H. M.
Bonville, P.
Long, Gary J
Hogan, T. P.
Funahashi, R.
Language :
English
Title :
The dynamics of the guests in filled germanium clathrates
Publication date :
2006
Event name :
MRS 2005 Fall Meeting
Event date :
November 2005
Main work title :
Mater. Res. Soc. Symp. Proc. Vol. 886
Publisher :
Materials Research Society
Pages :
389-394
Peer reviewed :
Peer reviewed
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