Compound tellurides and their alloys for peltier cooling—A review

The most recent data on the thermoelectric properties of cooling materials suitable for use near room temperature have been reviewed. The materials discussed include Bi2Te3 and its pseudo-binary Bi2Te3-Sb2Te3 and Bi2Te3-Bi2Se3 alloys, with the major emphasis on the pseudo-ternary alloys in the system Bi2Te3-Sb2Te3-Sb2Te3. The data presented include (1) the Seebeck coefficient, thermal conductivity, and figure of merit as a function of electrical resistivity; (2) the variations in the lattice thermal conductivity with alloying; (3) the temperature dependence of thermoelectric properties of the pseudo-ternary alloys. Presented also are the results of a recent study of growth variables on the thermoelectric properties of these alloys. The pseudo-ternary Bi2Te3-Sb3-Sb2Te2-Sb2Se3 system provided the best n- and p-type materials. These materials, which gave an average figure of merit of 3·3 × 10−3 deg−1 at room temperature, achieved a maximum Peltier cooling from room temperature of 78°K in a single-stage refrigerating couple. Furthermore, a temperature as low as 159°K was attained continuously from 300°K by a six-stage Peltier refrigerator constructed from these ternary alloys. The superior thermoelectric properties of these ternary alloys were interpreted on the basis of a large reduction and a small temperature dependence of the lattice thermal conductivity, and an increase in the energy band gap of the alloys with additions of Sb2Se3.