Thermoelectric properties of Zn/Sc codoped GeTe prepared by melt-spinning method

Abstract

GeTe thermoelectrics have received widespread attention due to their excellent thermoelectric performance. In this paper, GeTe samples are prepared by a melt spinning process combined with hot-pressing. The samples have a lower carrier concentration compared to those prepared by the traditional melting method, and the enhanced grain boundary scattering leads to a reduction in thermal conductivity. Zn doping is found to increase the density of states effective mass, leading to an enhanced Seebeck coefficient while maintaining a high mobility. The intensified phonon scattering of point defects and stacking faults in Ge_1-xZn_xTe samples leads to significantly reduced lattice thermal conductivity, with a minimum value of only ∼0.51 Wm⁻¹K⁻¹ at 775 K. The Ge_0.98Zn_0.02Te sample achieves a maximum zT∼1.4 at 775 K. The further introduced Sc not only enhances the phonon scattering from multi-scale microstructures to reduce the lattice thermal conductivity, resulting in the lowest value of ∼0.29 Wm⁻¹K⁻¹, but also improves the Vickers hardness, which is about 43 % higher than the Zn doped samples. This work demonstrates the Zn and Sc co-doped GeTe samples as excellent thermoelectric materials for practical applications.