2007 Volume 48 Issue 8 Pages 2056-2061
Bismuth antimony telluride has the best performance among the p-type thermoelectric materials used in the range of temperature between 300 K and 500 K. This material has a trigonal-hexagonal scalenohedral crystal structure and the cleavage parallel to the basal plane of the crystal can readily occur. Suppression of the electrical resistivity and the thermal conductivity will be effective for further improvement of the performance of the thermoelectric elements made from this material. The compressive torsion forming is the severe plastic deformation technique, in which the loads of compression and distortion are simultaneously subjected to the materials without change in its shape. In this work, we have applied this technique to the powder of bismuth antimony telluride for consolidation and improvement of the thermoelectric performance by refining the grain structure and by controlling the crystal orientation. The samples consolidated under various forming conditions were investigated with respect to density, microstructure, XRD, texture, and thermoelectric properties. It was found out that the compressive torsion forming is effective for the microstructure control, the grain structure less than 10 μm can be obtained, and the thermoelectric performance is obviously improved by the compressive torsion forming.
