Hole Effective Mass and Impurity Levels in Undoped AgTlTe. Optimum Thermoelectric Figure of Merit

Transport properties of undoped AgTlTe single crystals and sintered samples, in the range 125 to 450 K, are reported. The hole effective mass, the density of shallow and deep acceptors, and the ionisation energy of the deep center are calculated using conductivity, Hall effect, and thermopower measurements. The optimal thermoelectric figure of merit, which may be obtained by optimal doping, largely exceeds that of the best known thermoelements near room temperature.