TRANSPORT PHENOMENA IN PB0.78SN0.22TE WITH HIGH IN IMPURITY CONCENTRATIONS

The electrical conductivity, Hall coefficient, and thermoelectric powe r of (Pb0.78Sn0.22)1-yInyTe solid solutions with indium concentrations from 2 to 20 at. % have been measured in the temperature range 4.2-40 0 K. Activation-type temperature dependences were observed in the case of the electrical conductivity and the Hall density of electrons. The sip of the thermoelectric power of samples with high In (5 at. % or m ore) concentrations changed to positive as a result of cooling, but th e Hall coefficient remained negative. A qualitative explanation of the se observations was provided by invoking the concept of hopping conduc tivity and the model of the energy spectrum with a pseudogap between t he band and the impurity states.