Hot Extruded Bulk Polycrystalline (Bi1-xSbx)2(Te1-ySey)3 Alloys: Electron Transport and Lattice Thermal Conductivity

Hot extruded bulk polycrystalline n-type -(Bi1-xSbx)(2)(Te1-ySey)(3) quaternary alloys with low Sb and Se concentrations (< 10%) are anisotropic materials by virtue of their texture which is a result of severe shearing involved in the extrusion process. Harman-type measurements have provided the electrical and thermal conductivity, Seebeck coefficient, and thermoelectric figure of merit parallel to the extrusion axis, as a function of temperature, in the range similar to 220-420 K. Mobility and carrier concentration were determined by Hall effect measurements along a plane perpendicular to the extrusion axis in the range 15-420 K. Modeling the electronic transport properties allows the determination of the total (including thermodiffusion) electronic contribution to the thermal conductivity. Thus, the lattice thermal conductivity kappa(parallel to), along the extrusion axis, can be obtained with a reasonable degree of accuracy in the range 220-380 K. The results carry a rather large relative uncertainty at higher temperatures as kappa(parallel to). decreases with increasing temperature with a tendency which mimics that observed for the crystalline base compound -Bi2Te3.