 Bismuth Telluride by 2T3 and its alloys are widely used as materials for thermoelectric refrigeration and thermoelectric generators. At moderate temperatures, they have the highest thermoelectric power factor, or ZT, among all known materials. However, at higher temperatures, ZT decreases due to the presence of minority carriers. To optimize performance, compositions can be adjusted to reduce the amount of tellurium vaporized. This paper compares theoretical predictions of thermo power and electrical conductivity with experimental data obtained from by 2T3-based thermo elements at elevated temperatures. This article was authored by H. Julian Goldsmith.