Enhancement in thermoelectric power factor of polycrystalline Bi0.5Sb1.5Te3 by crystallite alignment

It is known that the random orientation of crystallites in polycrystalline Bi0.5Sb1.5Te3 reduces its thermoelectric power factor. An efficient method for growing ordered bulk polycrystalline Bi0.5Sb1.5Te3 was used and the enhancement of thermoelectric power factor was demonstrated. For comparison, samples with randomly and preferentially oriented crystallites were sintered from similar powder of Bi0.5Sb1.5Te3. A press process similar to extrusion was used to align the crystallites during the hot press. The crystallites alignment was verified by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The dominant orientation in the aligned sample was in c-plane (0,0,15). The aligned sample demonstrated significant increase in electrical conductivity while the Seebeck coefficient remained unchanged. As a result, the thermoelectric power factor of the aligned sample was improved by similar to 50%. (C) 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim