Effect of microstructure and composition on thermoelectric properties of Te-rich Sb/sub 2/Te/sub 3/

The effect of excess tellurium, including tellurium content and its dispersion state, on the thermoelectric properties of Te-rich Sb/sub 2/Te/sub 3/ was studied. The Sb/sub 2/Te/sub 3/ boules with 60/spl sim/90 mass%Te were grown by Bridgman-Stockbarger method and identified by means of X-ray diffraction (XRD). The microstructure and Sb-distribution in the boules were observed by SEM and EPMA. The boules containing from 60 to 61.9 mass%Te were a single phase of Sb/sub 2/Te/sub 3/, while the boules containing more than 62 mass%Te consisted of Sb/sub 2/Te/sub 3/ phase and eutectic phase with Te-Sb/sub 2/Te/sub 3/ lamella structure, and the boule containing 90.7 mass%Te was only Te-Sb/sub 2/Te/sub 3/ lamella structure. Hall coefficient and electrical resistivity /spl rho/ were measured over the temperature range from 100 to 500 K. Seebeck coefficient /spl sigma/ was measured over the temperature range from 300 to 500 K. Hall concentration of a boule with 60.7 mass% was of 1.09/spl times/10/sup 26//m/sup 3/ at room temperature. Hall concentration decreased with increasing Te contents. The boule containing 70.0 mass%Te showed a largest /spl alpha/ /sup 2///spl rho/ value of 7.05/spl times/10/sup -3/ W/(K/sup 2/m) at 350 K.