Microstructures and thermoelectric properties of GeSbTe based layered compounds

Microstructures and thermoelectric properties of Ge1Sb2Te4 and Ge2Sb2Te5 chalcogenide semiconductors have been investigated to explore the possibility of their thermoelectric applications. The phase transformation from the face-centered cubic to hexagonal structure was observed in Ge2Sb2Te5 compounds prepared by the melt spinning technique. The Seebeck coefficient and electrical resistivity of the alloys were increased due to the enhanced scattering of charge carriers at grain boundaries. The maximum power factors of the rapidly solidified Ge1Sb2Te4 and Ge2Sb2Te5 attained 0.975 x 10(-3) Wm(-1)K(-2) at 750 K and 0.767 x 10(-3) Wm(-1)K(-2) at 643 K respectively, higher than those of water quenched counterparts, implying that thermoelectric properties of GeSbTe based layered compounds can be improved by grain refinement. The present results show this class of chalcogenide semiconductors is promising for thermoelectric applications.