Electrical activity of metal vacancies in Pb/sub 1-x/Sn/sub x/Te solid solutions and thermoelectric properties of compositions for p-type leg of middle-temperature range thermogenerator

The maximum densities of holes generated by cation vacancies, as well as thermoelectric parameters of (Pb/sub 1-x/Sn/sub x/)/sub 1-y/Te/sub y/ solid solutions with tin content x in the range from 0.4 to 0.6, were studied. It is shown that each vacancy produces four holes in the valence band and that only for small x can the concept of a doubly charged vacancy be used. The maximum figure of merit Z is (1.0-1.1) /spl times/ 10/sup -3/ K/sup -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.