Phase Relations and Thermoelectric Properties of the Alloy Systems SnTe-Bi[sub 2]Te[sub 3] and PbTe-Sb[sub 2]Te[sub 3]

The phase relations in the quasi‐binary systems SnTe ‐ Bi 2 Te 3 and PbTe ‐ Sb 2 Te 3 have been determined using differential thermal analysis, x‐ray diffraction, electron microprobe, and optical metallographic techniques. The system SnTe ‐ Bi 2 Te 3 forms a continuous series of solid solutions from 45 to 100% Bi 2 Te 3 and the maximum solubility of Bi 2 Te 3 in SnTe was found to be about 5%. The system PbTe ‐ Sb 2 Te 3 contains a eutectic and exhibits little solubility of either component in the other. Measurements of the thermal and electrical properties of the SnTe ‐ Bi 2 Te 3 alloys showed that they are either n‐type or p‐type depending on composition, and that the carrier concentrations are degenerate ( ≥ ± 6 × 10 19 / cm 3 ) . At 300°K Seebeck coefficients are typically 90 µv/°K. The thermal conductivity is about 1.3 × 10 − 2 watts / ° K ‐ cm and nearly independent of temperature and composition. The maximum thermoelectric figure of merit obtained at 300°K for these alloys was 0.66°K −1