Thermoelectric properties of Bi‐Sb samples grown by mechanical alloy

Abstract

Seebeck coefficient S(T), electric resistivity ϱ(T) and thermal conductivity κ(T) measurements are reported on polycrystalline Bi0.88Sb0.12 samples grown by mechanical alloy (MA) by using different milling time. The electrical and thermal characterization was carried out in the temperature range between 77 K and 300 K. The Seebeck coefficient is negative in whole measurement range and its magnitude increases with the temperature, S(T) exhibit an enhancement with the milling time up to reach values close to –300 µV/K in the samples milled through 45 hours. The electrical resistivity shows a weak semiconductor behavior with the temperature, ϱ(T) was increasing with the processing time, but in all cases it shown values close to 10–3 Ω cm. The thermal conductivity measurements were carried out by using a steady-state heat-flow method. κ(T) show a linear behavior with the temperature and its magnitude decreases with processing time up to values smaller than 1 W/mK. By using SEM analysis the behavior of the granularity of the samples was studied as a function of the milling time. The dimensionless thermoelectric figure of merit ZT, reaches values close to 0.3, which are characteristic values for single crystalline alloys of these kind compounds. These results show that the mechanical alloy could be a useful technique in the production of thermoelectric materials. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)