THE EFFECT OF EXCESS TELLURIUM ON THE THERMOELECTRIC PROPERTIES OF BI2TE3-SB2TE3 SOLID-SOLUTIONS

The thermoelectric properties of Bi2Te3-Sb2Te3 solid solutions are closely related to excess Te in the melt during growth of ingots. The role of excess Te in connection with various process parameters which affect the thermoelectric properties of p-type Bi2Te3-Sb2Te3 solid solutions have been studied using the zone melting and Bridgman methods. The growth speed and amount of excess Te are important in optimizing the figure of merit. When the process parameters were optimized, a maximum figure of merit of 2.95 x 10(-3) K-1 was obtained by the zone melting method at a rate of 0.1 mm min(-1) for a composition 22.5% Bi2Te3-77.5%Sb2Te3 with 5 wt% excess Te in the melt. The effect of annealing of as-grown ingots on the thermoelectric properties is also reported.