Texture formation in extruded rods of (Bi,Sb)2(Te,Se)3 thermoelectric alloys.

The anisotropy in both the electrical and mechanical properties of (Bi,Sb)(2)(Te,Se)(3) thermoelectric alloys, and in turn in their overall performance, requires a close control of the alloy texture. In this work we have investigated extruded rods of n- and p- type thermoelectric alloys with square (25.4 mm x 25.4 mm) and circular (25.4 mm diameter) cross-sections. Figures of merit of up to 3.2 x 10(-3) K-1 for p-type alloys and 2.8 x 10(-3) K-1 for n-type alloys have been obtained for all extruded sizes. Texture investigations were made by X-ray diffraction. Electrical characterization and mechanical strength were measured in the longitudinal and radial directions. Comparison of the experimental data with numerical simulations shows that there is a correlation between the sample texture and the value of the equivalent plastic strain experienced by the material during the hot extrusion process.