Evolution of thermoelectric transport properties of Sb2Te3–Sb2Se3 solid-solution alloys depending on phase formation behavior.

Sb 2 Te 3 -based alloys exhibit decent thermoelectric transport properties in the mid-temperature range above 550 K. However, the study on Sb 2 Te 3 alloys has been limited in simple doping approach. Herein, evolution in the thermoelectric transport properties associated with the phase formation of solid solution alloys of Sb 2 (Te 1− x Se x) 3 (x = 0, 0.25, 0.33, 0.5, 0.75, and 1.0) compositions is investigated to widen the strategy to solid solution alloying. A single phase of the Sb 2 Te 3 rhombohedral structure formed from x = 0 to 0.5, whereas mixed phases with an orthorhombic structure of Sb 2 Se 3 was observed at x = 0.75. The electrical conductivity weighted mobility were gradually decreased as Se content increases to x = 0.75. Consequently, the power factor was decreased gradually and significantly to 0.076 mW/mK2 for x = 0.75 (Sb 2 (Te 0·25 Se 0.75) 3) compared with 2.6 mW/mK2 of the pristine sample. The total thermal conductivity of 2.0 W/mK for the Sb 2 Te 3 was significantly reduced gradually to 0.64 W/mK for x = 0.75 owing to simultaneous decrease in electrical and lattice thermal conductivities. The reduction in lattice thermal conductivity is mainly owing to the addition point defect scattering caused by the Se addition. Nevertheless, thermoelectric figure of merit zT of Sb 2 Te 3 is gradually decreased from 0.64 to 0.11 for x = 0.75 at 650 K due to the degradation in electrical transport properties. Furthermore, the theoretical zT was estimated for all samples with varying carrier concentration based on single parabolic band model. [ABSTRACT FROM AUTHOR]