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 ×25.4 mm) and circular (25.4 mm diameter) cross-sections. Figures of merit of up to 3.2×10^-3 K^-1 for p-type alloys and 2.8×10^-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.