Nanostructure, Excitations, and Thermoelectric Properties of Bi2Te3-Based Nanomaterials
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 × 1019 cm−3, large thermopower of 130 μV K−1, and large charge carrier mobility of 402 cm2 V−1 s−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 sintering, 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.
KeywordsThermoelectric effects nanostructured materials x-ray diffraction (XRD) analytical transmission electron microscopy (TEM) lattice dynamics point defects density functional theory (DFT)
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