Thermoelectric properties as a function of electronic band structure and microstructure of textured materials

A tool has been developed at Fraunhofer-IPM to calculate the transport properties of thermoelectric material by using its band structure described in terms of effective masses and the location of the ellipsoids in reciprocal space. The calculated transport properties are compared with experimental data measured on bismuth telluride, antimony telluride, and bismuth antimony telluride. Polycrystalline specimens have been prepared by spark plasma sintering (Fraunhofer-IFAM). Electron backscattering diffraction analysis of sample cross-sections yields the frequency distribution of grain orientations. This texture information permits the generation of appropriate finite-element models of the polycrystalline microstructure (TU Dresden). By means of the commercial code COMSOL, which allows anisot ropic thermoelectric properties to be taken into account, the effective electrical and thermal conductivities as well as the Seebeck coefficient both parallel and perpendicular to the pressing direction have been calculated.