Heterogeneous in-situ nanostructure contributes to the thermoelectric performance of Zn4Sb3

Single-phase Zn4Sb3 and ZnSb-containing samples were prepared by Plasma Activated Sintering. An abrupt decrease of thermal conductivity was found at about 400 K, which is attributed to the microstructure change of Zn4Sb3. Nanoscale inclusions and compositional inhomogeneities were found in Zn4Sb3 sample at 473 K by high-resolution transmission electron microscopy. The phonon scattering is enhanced by increasing grain boundaries and chaotic structure, which reduces the thermal conductivity and increases the thermoelectric performance of Zn4Sb3 at elevated temperature. The Rietveld refinement results show that large ZnSb grains in ZnSb-containing samples will accommodate excess Zn atoms, and then reduce thermoelectric performance.