Dimensionality, nanostructure, excitations and thermoelectric properties of Bi2Te3 and CoSb3 based nanomaterials

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Bi2Te3 and CoSb3 (skutterudite) based nanomaterials will be prepared as nanowires, thin films and nanostructured bulk to study the effects of dimensionality, nanostructure on excitations and thermoelectric properties. Advanced synthesis methods include potential-pulsed electrodeposition, molecular beam epitaxy and spark plasma sintering. Advanced characterization methods include energy-filtered analytical transmission electron microscopy, high-energy X-ray diffraction, nuclear inelastic scattering and neutron scattering. Thermoelectric properties will be measured over a wide temperature range up to 700 K. Controlled variation of stoichiometry of binary compounds will yield a fundamental understanding for controlling charge carrier densities in these nanomaterials and will yield optimized thermoelectric properties. Specific elements of the nanostructure were found to limit charge carrier mobilities and their density will be optimized. Doping and alloying of binary compounds will be used to control charge carrier densities but also to introduce filler atoms in skutterudite-type structures. Artificially designed structures will be obtained by a multilayer approach and by three dimensional defect structures for increasing phonon scattering. The theory group will investigate the effects of nanostructures on transport properties on the atomic length scale.