Effect of extrusion temperature and dopant on thermoelectric properties for hot-extruded p-type Te-doped Bi0.5Sb1.5Te3 and n-type SbI3-doped Bi2Te2.85Se0.15

The p-type Te-doped Bi0.5Sb1.5Te3 and n-type SbI3-doped Bi2Te2.85Se0.15 compounds were fabricated by hot extrusion in the temperature range of 300–440°C under an extrusion ratio of 20:1. The grains of the two compounds contained many dislocations and were fine equiaxed (∼1.0 μm) owing to the dynamic recrystallization during the extrusion. The hot extrusion gave rise to a slightly preferred orientation of grains. The bending strength and the figure of merit of the two compounds increased with increasing the extrusion temperature. In addition, the Te and SbI3 dopants significantly increased the figure of merit. The values of the figure of merit for the p-type 4.0 wt.% Te-doped Bi0.5Sb1.5Te3 and n-type 0.05 wt.% SbI3-doped Bi2Te2.85Se0.15 compounds hot extruded at 440°C were 2.94×10−3 and 3.05×10−3 K, respectively.