Zone inversion in the Bi/sub 2/Se/sub 3/ rich side of Bi/sub 2/Te/sub 3/-Bi/sub 2/Se/sub 3/ solid solution

Abstract

Solid solutions of Bi/sub 2/Te/sub 3/-Bi/sub 2/Se/sub 3/ pseudo-binary system were mechanically alloyed, cold pressed and then sintered at different temperatures between 250/spl deg/C and 380/spl deg/C. By sintering specimens for several hours in evacuated ampoules, the equilibrium thermoelectric properties were obtained. Significant differences in thermoelectric properties were found between the sintered materials and the single crystals grown by the conventional solidification processes. Besides the well known composition of Bi/sub 2/Te/sub 2/Se, singular properties were found at the composition of Bi/sub 2/TeSe/sub 2/. In the Bi/sub 2/Se/sub 3/ rich region, the thermal conductivity at room temperature showed unusual behaviour. The most plausible explanation for such phenomena appeared to be the inversion of conduction and valence zones. Detailed examination of the temperature dependence of the electrical conductivity confirmed this explanation.