Effect of sintering temperature on the thermoelectric properties of pulse discharge sintered (Bi0.24Sb0.76)2Te3 alloy

P-type thermoelectric material (Bi0.24Sb0.76)(2)Te-3 was sintered with pulse discharge sintering (PDS) process at temperatures of 345-495 degrees C. The microstructures of sintered materials were found to be well aligned along the basal planes on the transverse direction, particularly when sintered at lower sintering temperatures. The carrier concentration was found to be higher in the transverse direction than in the longitudinal, and to increase with sintering temperature, particularly when sintered at temperatures higher than 445 degrees C. On the other hand, the carrier mobility shows a peak value in the sintering temperature axis at a temperature of about 465 degrees C for the longitudinal and 445 degrees C in the transverse direction. Electrical and thermal conductivities were found to be higher in the transverse than the longitudinal direction, by a factor of about 2 when sintered at low temperature. Generally, both the electrical and thermal conductivity of the material increased with an increase in the sintering temperature. Seebeck coefficient was found to be higher in the longitudinal than in the transverse direction, and showed a general decreasing tendency with an increase in sintering temperature, particularly when the sintering temperature is higher than 445 degrees C. In terms of the figure of merit, the optimum sintering temperature was found to be 445 degrees C or 465 degrees C for a maximum Z value of around 3.1 x 10(-3)/K, in the longitudinal and transverse directions, respectively. (c) 2005 Elsevier B.V. All rights reserved.