Thermoelectric materials based on anion-substituted solid solutions in the Pb,Bi‖Se,Te ternary reciprocal system

The quaternary PbBi2(Te1 − x Se x )4, Pb2Bi6(Te1 − x Se x )11, PbBi4(Te1 − x Se x )7, and PbBi6(Te1 −x Se x )10 (0 < x < 0.8) anion-substituted solid solution alloys, which are of interest as thermoelectric materials, are investigated by X-ray diffraction and metallography. The dependences of the Seebeck coefficient and electrical and thermal conductivity of the solid solutions on the degree of anion substitution and temperature, along with their microhardness at room temperature, are studied. It is established that broad ranges of solid solutions with the trigonal symmetry based on tetradymite-like compounds belonging to the [PbTe] m [Bi2Te3] n homologous series exist in the Pb,Bi‖Se,Te ternary reciprocal system. It enables variation in thermoelectric properties over a wide range and establishment of the interdependence “composition-structure-properties.” The dependences of the above-mentioned kinetic coefficients on the alloy composition at 300 K and those of the microhardness of alloys are determined. These dependences are nonmonotonic. The behavior of the concentration dependences changes at alloy compositions in the range of x ∼ 0.3–0.4. The investigation of the temperature dependences of the thermoelectric properties for the PbBi6(Te1 − x Se x )10 and Pb2Bi6(Te1 − x Se x )11 solid solution alloys with long-period structures reveals that they enjoy low lattice heat conductivity (κ ph ), comparable to that of amorphous materials.