Abstract:

The layered PbBi₄Te₇ compound is considered a promising thermoelectric material due to its unusually high electrical transport properties in ternary compound systems. However, its high carrier concentration leads to relatively high thermal conductivity and low Seebeck coefficient, limiting the enhancement of its thermoelectric performance. In this work, we introduce Se alloying and Cu doping to synergistically regulate the thermoelectric transport properties of PbBi₄Te₇. Se alloying induces strong lattice contraction and increased interlayer electron scattering, significantly reducing lattice thermal conductivity while enhancing the Seebeck coefficient. Besides, Cu doping forms interlayer electron transport channels thus optimizing carrier mobility and electrical transport properties. Cu substitution also enhances point defect scattering further suppressing phonon transport. Ultimately, the strong anharmonic structure formed by Se alloying and Cu-induced phonon scattering results in a remarkably low lattice thermal conductivity of 0.27 W m⁻¹ K⁻¹ at 300 K in PbBi₄Te₅Se₂-0.1% Cu samples. The maximum thermoelectric figure of merit (ZT_max) is increased to 0.68, with an average thermoelectric figure of merit (ZT_ave) of 0.56 in the near-room temperature range (300-573 K), outperforming other typical ternary Pb-Bi-based compounds.

Key words: PbBi₄Te₇, Lattice contraction, Lattice thermal conductivity, Power factor, Thermoelectric figure of merit