Thermoelectric Properties of Directionally Solidified Bi2Te3 Alloys under High Thermal Gradient

Abstract

Thermoelectric Bi2Te3bulk alloys were directionally solidified successfully at the pulling rate ranging from 1 μm/s to 50 μm/s under a high temperature gradient of 200 K/cm. Preferred crystal orientations of (0 1 5), (1 0 10) and (1 1 0) faces appeared at the pulling rate of 50 μm/s. In the Bi2Te3alloys directionally solidified at 5 μm/s, the maximum Seebeck coefficient of -253 μV/K was obtained and the maximum electrical resistivity of 2.26 mΩ•cm was measured at 300 K. Besides, the optimum Power Factor (PF) value reached 3.83×10-3W/K2m at 1 μm/s and the measured results show that the thermoelectric Bi2Te3 bulk alloys grown at low growth rates supply the large PF value at ambient temperate, while at high temperature, the alloy grown at 50 μm/s has a better PF value.