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

The anisotropy in both the electrical and mechanical properties of (Bi,Sb)/sub 2/(Te,Se)/sub 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 /spl times/25.4 mm) and circular (25.4 mm diameter) cross-sections. Figures of merit of up to 3.2/spl times/10/sup -3/ K/sup -1/ for p-type alloys and 2.8/spl times/10/sup -3/ K/sup -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.