Thermoelectric Properties of Bi2Te3-Sb2Te3-Sb2Se3 Pseudo-Ternary Alloys in the Temperature Range 77 to 300 degrees K

The electrical resistivity, thermoelectric power and thermal conductivity of pseudo-ternary Bi2Te3-Sb2Te3-Sb2Se3 alloys were measured in the temperature range 77 to 300 degrees K. From these measurements, figures of merit at various temperatures were calculated and compared with effective figures of merit obtained from the results of Peltier cooling. Best n-type figure of merit, 3.2 x 10(-3) deg at 300 degrees K, was found at the Bi2Te3-rich region of the alloy system and the best room temperature p-type figure of merit, 3.4 x 10(-3) deg, was obtained at the Sb2Te3-rich end. Peltier couples constructed from these alloys reproducibly yielded a maximum cooling of 77.6 degrees K from room temperature. The superior thermoelectric properties of these alloys were attributed to the reduction in the lattice thermal conductivity and its small temperature dependence, and the increase in the energy band gap of the alloys upon additions of Sb2Se3.