A core-shell structure to realize high thermoelectric performance in Fe and Sb co-doped GeTe materials

Abstract

GeTe is a promising medium-temperature thermoelectric material. However, an excessively high concentration of Ge holes leads to a high hole carrier concentration, which can degrade its performance. Though carrier concentration reduction via doping has been pursued as a principal optimization approach, the strong interdependence between key transport parameters and carrier concentration severely limited the overall enhancement efficacy. In this work, a simple composite method is employed to achieve synergistic optimization of carrier concentration and carrier mobility, thereby increasing the power factor and reducing the lattice thermal conductivity. Sb and Fe form a core-shell structure, which effectively scatters phonons and reduces the lattice thermal conductivity, achieving a minimum value of 0.59 W⸱m^–1⸱K^–1 at 723 K. Additionally, Fe doping enhances the effective mass, improves the Seebeck coefficient, and significantly boosts the power factor, which reaches a peak value of 43.0 μW⸱cm^–1⸱K^–2 at 623 K. The results demonstrate that the sample Ge_0.885Sb_0.1Fe_0.015Te achieves a maximum zT of approximately 2.13 at 723 K and an average zT (zT_avg) of 1.43 within the temperature range of 323 K to 773 K. This work provides an effective path to enhance the performance of GeTe-based thermoelectric materials.