Electrical properties of lead telluride single crystals doped with Gd
Temperature dependences of electric conductivity, free carrier concentration and mobility in single-crystalline PbTe: Gd samples with a varied impurity content are investigated. The features of electron transport in PbTe: Gd may be caused by a variable gadolinium valence. The striking result from the Seebeck coefficient measurements is that the thermoelectric power factor increases dramatically. Measurements of the magnetic susceptibility at low temperatures permit us to suggest that Gd ions exist in different charge states.
Two charge states of Gd-impurities in the PbTe : Gd crystals
Abstract On the basis of EPR and magnetic susceptibility (MS) data it is shown that Gd ions in the PbTe : Gd crystals appear in two charge states Gd 2+ and Gd 3+ simultaneously. Gd 2+ state is dominant. The number of Gd 3+ is always far lower in comparison with total Gd concentration. A model explaining the existence of both Gd 2+ and Gd 3+ states on the basis of existence of the Gd substitution impurity and the complex `Gd substitution impurity–Te vacancy’ is presented.
Investigation of Transport Properies in Pb1-xSnxTe Doped with Indium
The electrical resistivity and the Hall coefficient (RH) vs temperature (4.2K≦T≦300 K) in Pb1-xSnxTe/In (0.21≦x≦0.35) have been measured. In the semi-insulating region (x=0.30), a sign inversion of RH with respect to the magnetic field is observed at (60 K≦T≦100 K), and this is due to the coexistence of electrons and holes. From this phenomenon, the mobility ratio of electrons and holes has been determined for the first time in this system. Using these results, the composition and temperature dependence of the chemical potential in Pb1-xSnxTe/In have been determined systematically. The results can be explained qualitatively by the autocompensation model (the Anderson negative U model).