Structure formation by hot extrusion of thermoelectric bismuth chalcogenide solid solution rods

Major advantage of extruded Bi₂Te₃ based thermoelectric materials is high mechanical strength compared with that of melt-crystallized materials. Mechanical properties are of special importance for thermogenerator module applications where thermogenerator branches may undergo elevated thermal stresses due to large temperature differences at the modules. Since extrusion is typically a high-temperature process the structure of extruded materials is controlled by the plastic deformation in multiple slip systems resulting in the formation of a final deformed structure. The grain orientations are predominantly such that the most probable cleavage plane orientation is parallel to the extrusion axis. Recovery processes occur simultaneously and different recrystallization stages may take place. In the latter case the deformed texture may be destroyed.