Coordinated Electronic-Transport Regulation and Multiscale Phonon Scattering in Sb-La Co-Doped GeTe

GeTe is a promising p-type thermoelectric material for mid-to-high temperature applications because of its favorable electronic structure and excellent transport potential. However, its thermoelectric performance is still limited by excessive hole concentration and insufficient phonon scattering. Herein, rare-earth La was co-doped with Sb into GeTe via a melting-annealing-spark plasma sintering process, and the microstructure and thermoelectric transport properties of the samples were systematically evaluated. The thermoelectric characterization reveals that the co-doping strategy significantly lowers the thermal conductivity without compromising electrical performance, thereby contributing to enhanced thermoelectric performance. The incorporation of Sb effectively regulates the hole concentration, preserves the electrical transport properties, and reduces the electronic thermal conductivity. In addition, La doping induces strain-field fluctuations and local structural disorder, introducing multiscale micro- and nano-structural features, which significantly strengthen phonon scattering and thereby suppress the lattice thermal conductivity. As a result, the Ge_0.89Sb_0.1La_0.01Te composition achieves a peak zT of 2.8 at 793 K. These results demonstrate that rare earth-assisted composition tuning is an effective strategy for improving the thermoelectric performance of GeTe-based materials.