The Effects of Growth Rate on the Thermoelectric Properties of Bi[sub 2]Te[sub 3]-Sb[sub 2]Te[sub 3]-Sb[sub 2]Se[sub 3] Pseudoternary Alloys

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Abstract
The effects of growth rate on the thermoelectric properties of n‐ and p‐type pseudoternary alloys have been investigated and correlated with microstructures. The results show that higher values of the figure of merit (Z) are invariably associated with lower growth rates and hence greater homogeneity. For both n‐ and p‐type alloys, the improvement in Z was as large as 50% when the growth rate was reduced from about 6 to 0.6 cm/hr. However, the growth‐rate dependence of individual thermoelectric parameters was not the same for both alloys. For the n‐type alloy, which is a single‐phase alloy, slow growth rates resulted in an increase in the Seebeck coefficient, and a decrease both in the lattice thermal conductivity and electrical resistivity. For the p‐type alloy, the variations with growth rate in the Seebeck coefficient and, to a lesser extent, in the lattice thermal conductivity were similar to those for the n‐type alloy. However, its electrical resistivity increased with decreasing growth rates, and this was shown to be associated with the presence of a Te‐rich second phase in the p‐type alloy. Consistent with this interpretation are the results of an annealing study of these alloys.

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