Thermoelectric properties of cation-substituted solid solutions based on layered tetradymite-like compounds

It is shown that isovalent cation substitutions in the Ge(Bi1-xSbx)(4)Te-7 (0 < x < 1) and Pb1-xSnxBi4Te7 (0 < x < 1) solid-solution systems ensure a markedly reduced lattice thermal conductivity in comparison with the constituent ternary chalcogenides. In the Ge(Bi1-xSbx)(4)Te-7 system, increasing the Sb content leads to a conversion from n- to p-type. Cu-doped PbBi4-xCdxTe7 solid solutions (heterovalent substitution) arc n-type and surpass PbBi4Te7 in the thermoelectric figure of merit.