Transport and Thermoelectric Properties of Bi2Te2.7Se0.3 Prepared by Mechanical Alloying and Hot Pressing

Bi2Te2.7Se0.3 was prepared by mechanical alloying (MA) and hot pressing (HP), after which the effects of HP temperature on the transport and the thermoelectric properties were evaluated. Bismuth chalcogenide phases were synthesized after MA for 4 h, and no secondary phases were observed. The relative densities of all hot-pressed specimens were higher than 95%. The carrier concentration and the mobility increased with increasing HP temperature, possibly due to the grain growth and the reduced number of lattice defects. All specimens showed n-type conductions in the temperature range from 323 K to 523 K. The electrical conductivity slightly decreased with increasing temperature, exhibiting a degenerate semiconductor behavior. With increasing HP temperature, an increase in the electrical conductivity and a decrease in the Seebeck coefficient were observed. The maximum dimensionless figure of merit obtained was 0.72 at 473 K for the Bi2Te2.7Se0.3 hot-pressed at 673 K due to its low thermal conductivity and high electrical conductivity