Microstructure and thermoelectric properties of hot-extruded Bi-Te-Se bulk materials

Highly dense n-type Bi2Te2.85Se0.15 bulk thermoelectric materials were fabricated by a mechanical alloying (MA) and hot-extrusion technique. The extrusion behavior, microstructure, texture, thermoelectric and mechanical properties have been investigated. The extruded samples exhibited fine-grained microstructure and preferred grain orientation. The basal planes in the extrudates were preferentially oriented parallel to the extrusion direction. As the extrusion temperature increased, the absolute value of the Seebeck coefficient and electrical resistivity were found to decrease, while the thermal conductivity increased. A largest dimensionless figure of merit value of 0.47 was achieved at room temperature for the sample extruded at 400 °C. Moreover, the extruded samples showed high hardness values.