Dresden 2003 – scientific programme
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MA: Magnetismus
MA 4: Kondo / Schwer-Fermionen / Quasi-Niedrigdimensionale Systeme (gemeinsam mit TT)
MA 4.8: Talk
Monday, March 24, 2003, 12:00–12:15, HSZ/405
Transport properties of α - and β -Eu8Ga16−xGe30+x, 0.15‹x‹1.5 — •A. Bentien, V. Pacheco, S. Paschen, M. Baenitz, W. Carrillo-Cabrera, Yu. Grin, and F. Steglich — MPI für Chemische Physik fester Stoffe, Nöthnitzer Str. 40, D - 01187 Dresden
Clathrates are solids made up of large cages of silicon, germanium, or tin (or, in the well-known gashydrate-clathrate-I, of H2O) which encapsulate guest atoms. Eu8Ga16Ge30 is the only clathrate known so far where the guest positions are fully occupied by a rare-earth element. The Zintlrule predicts clathrates with ideal stoichiometry 8:16:30 to be semiconducting. However, all α - and β -Eu8Ga16Ge30 samples investigated so far have metal-like electrical resistivities. We believe that this is due to a small deviation from the ideal Ga/Ge stoichiometry. In this talk we present transport properties for several α and β samples with carrier concentrations ranging from 0.15 to 1.5 electrons per formula unit. Particular emphasis will be put on the thermoelectric properties since it is believed that clathrates have the potential to become very useful thermoelectric materials if the optimal charge-carrier concentration is found.