Transport phenomena in the anisotropic layered compounds MeBi4Te7 (Me = Ge, Pb, Sn)

Abstract

The transport coefficients (the Nernst-Ettingshausen coefficient Q123, electrical conductivity σ11, thermal conductivity κii, the Seebeck coefficients S11 and S33, and the Hall coefficient R213) in samples of layered compounds of the homologous series AIVBVI-A2VB3VI (AIV = Ge, Sn, Pb; AV = Bi, Sb; BVI = Te), specifically, SnBi4Te7 and PbBi4Te7 (of n-type conductivity), have been experimentally studied in the temperature range of 77–400 K. The crystals were grown by the Czochralski method. Analysis showed that the obtained data on the transport phenomena in SnBi4Te7 and PbBi4Te7 can be considered in the one-band energy spectrum model. Comparison of the parameters found for the stoichiometric samples demonstrated that the electron density of states and the fraction of electrons scattered at impurity ions increase when passing from GeBi4Te7 to SnBi4Te7 and PbBi4Te7. It is found that additional doping of PbBi4Te7 with cadmium and silver significantly affects its electronic and phonon systems, just as doping with copper affects the electric and thermal properties of GeBi4Te7.