The influence of process parameters on the carrier generation during the hot pressing of Bi/sub 2/Te/sub 3/-Bi/sub 2/Se/sub 3/ solid solutions

Abstract

Hot pressed Bi/sub 2/Te/sub 3/-Bi/sub 2/Se/sub 3/ alloys show different thermoelectric properties compared to alloys grown by the ordinary zone melting growth method. When specimens were hot pressed, thermoelectric properties changed according to different particle size, pressing time and hot pressing temperature. The effects of these individual parameters on the thermoelectric properties of hot pressed materials were examined. Special emphasis was put on carrier generation mechanisms related to the following parameters; oxidation, mechanical deformation during pulverization and the hot pressing temperature. It was found that all processing parameters influence the generation of electrically active defects. Defects induced by the mechanical deformation and oxygen cause generation of donors. Defect concentration is also altered with different hot pressing temperatures depending on the amount of previously received mechanical deformation. A figure of merit of 2.4/spl times/10/sup -3/ K/sup -1/ could be obtained at an optimal process condition.