Crystal Structure and Thermoelectric Properties of Bulk Polycrystalline (Sbxbi1-X)2se3 Alloys

Samples of (SbxBi1-x)2Se3 compounds were synthesized from pure elements via simple melting in evacuated quartz tubes. Internal crystal structure, distribution of constituent elements and surface morphology were examined by X-ray diffraction analysis, energy dispersive x-ray spectroscopy and scanning electron microscope, respectively. Over a temperature range of 300-480 K, electrical and thermoelectrical properties were investigated. The electrical conductivity showed semi-metallic behavior against temperature increasing till a certain point, thereafter, exhibited semiconducting trend. A significant increase was observed due to Sb-doping. Seebeck coefficient exhibited notable increase as temperature increases, reaching its maximum. However, a serious decrease was observed with further temperature increasing. The most Sb-doped compound (Sb0.1Bi0.9)2Se3 showed a maximum power factor of 13.29 mu W cm-1 K-2 at 373 K. Temperature dependence of the thermoelectric figure of merit ZT was studied, showing that the values increase with temperature increasing and then decrease. For the pristine Bi2Se3 compound, at room temperature, ZT increased from 0.014 to 0.68 at 363 K and then decreased again to 0.13 at 473 K. Doping with Sb at x = 0.1 resulted in remarkable increase in the ZT values over the entire temperature range. The improvement in electrical conductivity and the power factor are responsible for the greatly enhanced ZT throughout the whole temperature range. The maximum ZT was found at 0.87 for (Sb0.1Bi0.9)2Se3 at 373 K.