Improved zT in Nb₅Ge₃-GeTe thermoelectric nanocomposite

Robust electronic transport properties is a crucial in designing high performance thermoelectrics. A key similarity between superconductor and thermoelectric lies in their generally high electrical conductivity, even at above its superconducting temperature. In this work, we design a nanocomposite between Nb₅Ge₃ and GeTe-based thermoelectric to improve its thermoelectric figure of merit zT. Phase and microstructural characterization shows distinct Nb₅Ge₃ precipitates embed in Ge_0.9Sb_0.1Te matrix. In addition, experimental electronic and thermal transport analysis, together with density functional theory calculation were employed to show the synergistic effect of doping Sb and Nb₅Ge₃ nanocomposite approach. 10% Sb doping was found to optimize the electronic properties of the GeTe-based matrix. Further addition of 2 wt% Nb₅Ge₃ nanocomposite to the matrix enhances the phonon scattering, which consequently lowers the lattice thermal conductivity, which results in zT of up to 2.0 at 723 K. Such superconductor nanocomposite approach shown in this work can be employed to enhance the properties of other thermoelectric materials.