Microstructure, mechanical properties, and thermoelectric properties of hot-extruded p-type Te-doped Bi0.5Sb1.5Te3 compounds

The p-type Bi0.5Sb1.5Te3 compounds with Te dopant (4.0 and 6.0 wt%) and without dopant were fabricated by hot extrusion in the temperature range of 300 to 510 degrees C under an extrusion ratio of 20:1. The undoped and Te doped compounds were highly dense and showed high crystalline quality. The grains contained many dislocations and were fine equiaxed (similar to 1.0 mu m) owing to the dynamic recrystallization during the extrusion. The hot extrusion gave rise to the preferred orientation of grains. The bending strength and the figure of merit of the undoped and Te doped compounds were increased with increasing the extrusion temperature. The Te dopant significantly increased the figure of merit. The values of the figure of merit of,the undoped and 4.0 wt% Te-doped compounds hot extruded at 440 degrees C were 2.11x10(-3)/K and 2.94x10(-3) /K, respectively.