Comparison of different pressing techniques for the preparation of n-type silicon-germanium thermoelectric alloys

Improvements to state-of-the-art Si/sub 80/Ge/sub 20/ thermoelectric alloys have been observed in laboratory-scale samples by the application of the powder metallurgical techniques of mechanical alloying and hot pressing. Incorporating these improvements in large scale compacts for the production of thermoelectric generator elements is the next step in achieving higher efficiency RTG's. This paper discusses consolidation of large quantities of mechanically alloyed powders into production size compacts. Differences in thermoelectric properties are noted between the compacts prepared by the standard technique of hot uniaxial pressing and hot isostatic pressing. Most significant is the difference in carrier concentration between the alloys prepared by the two consolidation techniques.