Thermoelectric materials with low heat conductivity based on PbSe-Bi2Se3 compounds

Phase analysis of alloys in the PbSe-Bi2Se3 system is performed by the X-ray powder diffraction method (XRD), and the coefficient of thermoelectromotive force (thermo emf) and electric and heat conductivity of the layered ternary compounds Pb5Bi6Se14, Pb5Bi12Se23, and Pb5Bi18Se32 and alloys of PbSe-based solid solutions are measured at room temperature and in the temperature range of 80–350 K. Low lattice heat conductivity is typical of the ternary alloys, which is caused by effective phonon scattering on potential barriers on the boundaries between [(PbSe)5] and [(Bi2Se3)3] layered blocks typical of the structures for these compounds. In the range of PbSe-based solid solution, the concentration dependences of the thermo emf coefficient and electric and heat conductivity are plotted at 300 K. Two ranges of alloy compositions with different thermoelectric properties and microhardness are distinguished. For low concentration of Bi2Se3 (up to 5–7 mol %) in these alloys, low lattice heat conductivity and high microhardness are typical. At higher concentrations of Bi2Se3 (>7 mol %), the character of the properties changes: lattice heat conductivity increases, while microhardness decreases. It is assumed that this difference in properties is caused by different mechanisms of disordering of the crystal lattice of the solid solution with a change in Bi2Se3 concentration.