Hole concentration and thermoelectric figure of merit for Pb1−xSnxTe:Te solid solutions

The maximum densities of holes generated by cation vacancies, as well as thermoelectric parameters of (Pb1−xSnx)1−yTey solid solutions with tin content x in the range from 0.4 to 0.6, were investigated. It is shown that each vacancy produces four holes in the valence band and that only for small x can the concept of doubly charged vacancy be used. The maximum thermoelectric figure of merit Z is (1.0−1.1)×10−3 K−1 at T=800–850 K. The relatively high value of Z achieved without doping is due to the high electrical conductivity provided, first, by the small effective mass of holes and, second, by the high electrical activity of the vacancies.