Berlin 2015 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 81: Electronic Structure Theory: Many-Body Effects (organized by O)
TT 81.4: Poster
Wednesday, March 18, 2015, 18:15–21:00, Poster A
Thermoelectric clathrates: stability of the Ba8AlxSi46−x and Sr8AlxSi46−x compounds — •Maria Troppenz, Santiago Rigamonti, and Claudia Draxl — Humboldt-Universität zu Berlin
On the search for high-efficiency thermoelectric materials, promising candidates are clathrate compounds. Their cage-like structure, capable of containing guest atoms, allows for exploiting the idea of the phonon-glass electron-crystal, proposed as a way to reach a large figure of merit.
In this work, we focus on the clathrates Sr8AlxSi46−x and Ba8AlxSi46−x . In contrast to the well-studied Ga-Ge based clathrates, Al-Si clathrates are of technological interest in terms of price, weight, and low environmental impact. The use of Sr and Ba as guests is motivated by the glass-like conductivity of Sr8Ga16Ge30 and the high thermoelectric efficiency of Ba8Ga16Ge30. The electronic transport properties are optimized at the Zintl composition, corresponding to x=16. However, it has not been possible to synthesize samples with x > 10 for Sr or x > 15 for Ba [1].
We explore the structural stability of the compositional range 0≤ x≤ 16 as well as the stability against competing phases that are observed in experiments (e.g. SrAl2Si2). Due to the large number of substitutional configurations we resort to a cluster expansion based on accurate calculations of a subset of substitutional configurations.
[1] J.H. Roudebush, N. Tsujii, A. Hurtando, H. Hope, Y. Grin, and S.M. Kauzlarich, Inorg. Chem. 51, 4161 (2012).