Study of the crystallization and dopants effect on the semiconducting thermoelectric compounds with (Bi0.25 Sb0.75)2Te3 formula

The (Bi0.25 Sb0.75)2Te3 compound is a p-type thermoelectric semiconductor for application in thermoelectric cooling systems. To fabricate this single crystal, required elements, Bi, Sb and Te with 5N purity melted in quartz capsule at 10-6 torr pressure and rapidly quenched to room temperature. The sample crystallized by zone melting method with the rate of 8 mm per an hour at 700 oC and for heat stress relieving annealed at 370 oC.In this presentation; crystal growth process and effect of dopants on improving the thermoelectric property of crystals will be reported. Structural studies by XRD show the expected phases formed in single phase. Scanning electron microscopy (SEM) was used to characterize the quality of the crystal growth. Maximum figure of merit Z = 3.15×10-3 K-1in optimum condition was obtained.