Abstract:

GeTe-based alloys have attracted considerable attention as promising mid-temperature thermoelectric materials owing to their excellent performance. In this study, a series of Ge_0.8-xMn_0.1Pb_0.1Bi_xTe alloys were synthesized by vacuum melting followed by hot-press sintering. The results demonstrate that Bi incorporation significantly enhances the Seebeck coefficient. With increasing Bi content, the crystal structure gradually evolves from a rhombohedral to a cubic phase. Simultaneously, Bi-induced lattice distortion intensifies phonon scattering, leading to a marked reduction in lattice thermal conductivity, while the electronic thermal conductivity also decreases as a result of reduced electrical conductivity. At 773 K, the total thermal conductivity of Ge_0.8-xMn_0.1Pb_0.1Bi_0.02Te reaches a low value of 1.34 W/(m·K). Consequently, the alloys exhibit enhanced thermoelectric figure of merit (Z_T) values in the low-to-mid temperature range while maintaining high Z_Tat elevated temperatures, yielding a high average thermoelectric figure of merit (Z_T,avg) of 0.80.

Key words: thermoelectric materials, doping, GeTe, thermal conductivity, thermoelectric figure of merit