Structural Transformations in (Bi, Sb)2Te3 Solid Solutions Grown by Spark Plasma Sintering

Abstract

We have studied the dependence of the thermoelectric properties of the bulk (Bi,Sb)2Te3 material on the temperature of spark plasma sintering (SPS). For analysis of the experimental results we took into account the regularities of structure formation in the material. The average crystallite size decreases with an increase in the SPS temperature to above 400 °C. Transmission electron microscopy showed that at above 400 °C the bulk and boundaries of the initial grains that are several micrometers in size contain a large number of nanosized grains (approx 10 - 20 nm) having the same composition. We show that the dependence of the thermoelectric properties of the material on SPS temperature correlates with changes in the fine structure of the material which is controlled by the redistribution of the intrinsic point defects. Our results suggest that, along with the well-known nanostructure formation processes, there is one more high-temperature self-organizing process of the formation of the nanostructural material based on the redistribution and change in the form of occurrence of the nonequilibrium point defects. This information can be used to broaden the possibilities of controlling the properties of the bulk thermoelectric material on the basis of (Bi,Sb)2Te3.