Impact of Sm alloying and thermal annealing on the structural and thermoelectric properties of (GeTe)0.85(Pb1-xSmxTe)0.15 alloys

Abstract Besides the energy-conversion efficiency and production cost, the thermal stability is also a key parameter for the wide-spread use of a thermoelectric material in device-level. The rare-earth-element Sm content is introduced into the (GeTe) 0.85 (Pb 1- x Sm x Te) 0.15 alloys to tune the thermal stability and structural properties of these alloys, especially the spinodal decomposition. The Sm content shows suppression effect on the generation of secondary-phase PbTe-rich domains, and it also tend to stabilize the thermodynamically balanced state with stabilized microstructures and thermoelectric performance. The reduction of the lattice thermal conductivity by Sm alloying is mainly ascribed to the grain refining and the designing of all-scale hierarchical architectures for full-spectrum phonon scattering. By thermal annealing, the ZT values can increase by 25% and 76% for the (GeTe) 0.85 (Pb 1- x Sm x Te) 0.15 alloys with x  = 0.2 and x  = 0.28 respectively. The synergetic strategy of rare-earth element doping and thermal annealing in this study opens up a potential pathway to enhance the thermoelectric performance and thermal stability.