Power & Industrial Systems R&DCenter, Toshiba Corporation, 2-4 Suehiro-cho Tsurumi-ku, Yokohama 230-0045,Japan

High efficiency and low costbismuth telluride thermoelectric modules have been developed. A long directionallysolidified bismuth telluride rod is necessary to reduce the material loss andimprove the thermoelectric properties.

Directionally solidifiedbismuth telluride rods were made by Bridgman type furnace. Mold materials,melting temperature, growing rate of crystal, growing temperature were changed.We investigated the effect of these manufacturing parameters on themicrostructure and on the thermoelectric properties, such as Seebeckcoefficient, thermal conductivity and electrical resistance.

Many porosities were formedusing with small diameter quartz and alumina tubes. The porosity fraction wasover 40% using 4mm dia. quartz tube. However, the porosity fraction can bedecreased to less than 1% with using a carbon mold.

Effects of melting temperature,growing temperature and growing rate on the properties of thermoelectricmodules were investigated. In the manuscript, we will also describe theseresults.