Contrasting the Roles of Cu Interstitials and Sb Substitutions in Regulating Ferroelectric Distortions and Thermoelectric Properties of α-GeTe

Abstract

α-GeTe has attracted intensive attention recently due to its intriguing ferroelectric distortion as a freedom to engineer thermoelectric properties. However, pristine α-GeTe features overhigh carrier concentration (∼1021 cm–3) that degrades the overall performance. In this study, Sb substitutions and Cu interstitials are employed to neutralize the excess holes in α-GeTe. It is revealed that, while both Sb and Cu dopants serve as effective electron donors, they have notably different influences on the structural parameters of α-GeTe. Cu interstitials exert negligible impact on the ferroelectric distortion of α-GeTe. By contrast, Sb substitutions for Ge tend to improve the structure symmetry and valence band degeneracy. As a consequence, Ge1–x Sb x Te shows a much enhanced Seebeck coefficient. Meanwhile, Ge1–x Sb x Te displays lower lattice thermal conductivities than Cu y GeTe, particularly around ambient temperatures, because of the pronounced ferroelectric instability. Ge0.92Sb0.08Te shows a highest ZT value of ∼1.5 at 723 K, which is ∼60% higher than that of the pristine α-GeTe.

Enhancing the thermoelectric performance of GeTe through Sb doping and nanocompositing with SiC for reduced thermal conductivity

“…Sb, serving as an efficient dopant that enables precise regulation of carrier concentration across a broad range, effectively reduces electronic thermal conductivity while concurrently enhancing electrical transport properties with excellent reproducibility. [18][19][20][21] Doping antimony (Sb) in GeTe not only optimizes the carrier concentration but also adjusts the energy band structure. [22][23][24] Temperaturedependent electrical transport properties of Ge 1−x Sb x Te (x = 0, 0.02, 0.04, 0.06, 0.08, and 0.10) samples are presented in Fig.…”

Leveraging the Cu2SnTe3 additive for an improved thermoelectric figure of merit and module efficiency in Bi0.5Sb1.5Te3-based composites

“…Additionally, Cu 2− x Te can further potentially generate multiscale nano-defects, including dislocations and ordered/disordered Cu vacancies. (iii) The beneficial effects of copper-containing compounds have been extensively demonstrated in various TE materials, such as SnSe, 37 PbTe, 38 GeTe, 39 and half-Heusler alloys, 40 and compared to other additives, its most notable characteristic is the minimal adverse impact on carrier mobility. Based on a process combining BM-SPS, the substitution of Cu and Sn for Bi/Sb, leading to the injection of hole concentration ( p H ) and an augmentation in the density-of-states effective mass , in turn facilitates a net increase in the weighted mobility ( μ W ) and the corresponding power factor ( S 2 σ , PF).…”

Understanding the origin of the high thermoelectric figure of merit of Zintl-phase KCaBi

“…Large PF and optimized values of S and σ can be obtained simultaneously due to the presence of converged dispersed and non-dispersed bands at the band edges of the electronic band structure, 1,2 high and steep density of states in the vicinity of the Fermi level, 3–6 etc. , which may be present by default in some materials 7–10 due to their unusual structural properties or can be achieved by doping/substituting heavy elements, 11–18 nanostructuring, 19,20 application of pressure, 21 electric field, 22 and lattice strain, 23–26 and so on.…”