Abstract:
The transport coefficients (the Nernst–Ettingshausen coefficient $Q_{123}$, electrical conductivity $\sigma_{11}$, thermal conductivity $\kappa_{ii}$, the Seebeck coefficients $S_{11}$ and $S_{33}$, and the Hall coefficient $R_{213}$) in samples of layered compounds of the homologous series A$^{\mathrm{IV}}$B$^{\mathrm{VI}}$–A$^{\mathrm{V}}_2$B$^{\mathrm{VI}}_3$ (A$^{\mathrm{IV}}$–Ge, Sn, Pb; A$^{\mathrm{V}}$–Bi, Sb; B$^{\mathrm{VI}}$–Te), specifically, SnBi$_4$Te$_7$ and PbBi$_4$Te$_7$ (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 SnBi$_4$Te$_7$ and PbBi$_4$Te$_7$ 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 GeBi$_4$Te$_7$ to SnBi$_4$Te$_7$ and PbBi$_4$Te$_7$. It is found that additional doping of PbBi$_4$Te$_7$ with cadmium and silver significantly affects its electronic and phonon systems, just as doping with copper affects the electric and thermal properties of GeBi$_4$Te$_7$.
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