Dresden 2011 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Aktualisierungen | Downloads | Hilfe
DS: Fachverband Dünne Schichten
DS 60: Thermoelectric Materials, Thin Films, and Nanostructures II (Focused Session -- Organisers: Nielsch, Rastelli, Balke)
DS 60.7: Vortrag
Freitag, 18. März 2011, 15:30–15:45, GER 37
Electronic structure and thermoelectric properties of doped Heusler compounds. — •G. H. Fecher, S. Ouardi, and C. Felser — Institute of Inorganic and Analytical Chemistry, Johannes Gutenberg - University, Mainz, Germany
Different substitutional series of Heusler compounds XTi1−xYxZ (where X = Co, Ni, Y = Sc, V and 0<x<0.2, and Z = Sn, Sb) were investigated by ab-initio calculations of their electronic structure, mechanical, optical, and transport properties. Different theoretical methods were applied. The results from the ground state electronic structure calculations were used together with Boltzmann transport theory to calculate the thermoelectric transport properties. The mixed compounds with random site occupancy were treated by the virtual crystal and coherent potential approximations. It is found that the in-gap states observed for the pure compound arise from anti-site disorder by partially filling the vacant site of the lattice by Ti through swap and contain about 0.1 electrons per cell. This "self-doping" results in the excellent thermoelectric properties of the pure material. The calculated carrier concentration and temperature dependence of electrical conductivity, Seebeck coefficient, and thermal conductivity were calculated in the range from 10 K to 300 K and agree very well with the experimental observation. The sign of the Seebeck coefficient changes from negative for V to positive for Sc substitution. The calculations reveal that the high n-type and low p-type power factors are explained by differences in the chemical disorder scattering induced electric resistivity.