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Nanostructure, excitations, and thermoelectric properties of Bi2Te3-based nanomaterials

 
: Aabdin, Z.; Peranio, N.; Eibl, O.; Töllner, W.; Nielsch, K.; Bessas, D.; Hermann, R.P.; Winkler, M.; König, J.; Böttner, H.; Pacheco, V.; Schmidt, J.; Hashibon, A.; Elsässer, C.

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Journal of Electronic Materials 41 (2012), No.6, pp.1792-1798
ISSN: 0361-5235
ISSN: 1543-186X
International Conference on Thermoelectrics (ICT) <30, 2011, Traverse City/Mich.>
Deutsche Forschungsgemeinschaft DFG
SPP 1386;
Nanostrukturierte Thermoelektrika: Theorie, Modellsysteme und kontrollierte Synthese
English
Journal Article, Conference Paper
Fraunhofer IPM ()
Fraunhofer IFAMDD ()
Fraunhofer IWM ()
thermoelectric effect; nanostructured material; XRD; TEM; lattice dynamics; point defects; DFT

Abstract
The effect of dimensionality and nanostructure on thermoelectric properties in Bi2Te3-based nanomaterials is summarized. Stoichiometric, single-crystalline Bi2Te3 nanowires were prepared by potential-pulsed electrochemical deposition in a nanostructured Al2O3 matrix, yielding transport in the basal plane. Polycrystalline, textured Sb2Te3 and Bi2Te3 thin films were grown at room temperature using molecular beam epitaxy and subsequently annealed at 250°C. Sb2Te3 films revealed low charge carrier density of 2.6 × 10(exp 19) cm-3, large thermopower of 130 µV K(exp -1), and large charge carrier mobility of 402 cm2 V(exp -1) s(exp -1). Bi2(Te0.91Se0.09)3 and (Bi0.26Sb0.74)2Te3 nanostructured bulk samples were prepared from as-cast materials by ball milling and subsequent spark plasma sinter ing, yielding grain sizes of 50 nm and thermal diffusivities reduced by 60%. Structure, chemical composition, as well as electronic and phononic excitations were investigated by x-ray and electron diffraction, nuclear resonance scattering, and analytical energy-filtered transmission electron microscopy. Ab initio calculations yielded point defect energies, excitation spectra, and band structure. Mechanisms limiting the thermoelectric figure of merit ZT for Bi2Te3 nanomaterials are discussed.

: http://publica.fraunhofer.de/documents/N-206145.html