Berlin 2015 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 24: Thermoelectricity
HL 24.5: Vortrag
Dienstag, 17. März 2015, 10:30–10:45, EW 202
Chemical ordering in inorganic clathrates and its effect of thermoelectric performance — •Paul Erhart, Mattias Ångqvist, and Daniel Lindroth — Chalmers University of Technology, Gothenburg, Sweden
Inorganic clathrates are of interest due their very good thermoelectric performance at elevated temperatures. Here, we consider type-I clathrates with composition A8B16C30, where A=Ba is the guest species while B=Al/Ga and C=Si/Ge comprise the matrix. Cluster expansions and Monte Carlo simulations are employed to explore chemical ordering in these materials. The cluster expansion models are parametrized with respect to density functional theory calculations using a compressive sampling approach. The calculated site occupancy factors are in very good agreement with experiment. The Al-Al and Ga-Ga nearest neighbor pair interaction is always repulsive, which is in accord with the empirical rule that Al-Al/Ga-Ga pairs are to be avoided. Using Boltzmann transport theory we then quantify the effect of chemical order on the electrical and thermal conductivity as well as the Seebeck coefficient. The results are discussed with respect to their implications on thermoelectric performance and the potential for property modification via controlling the degree of order in the system.