In-situ TEM studies of nanostructured thermoelectric materials: An application to Mg-doped Zn4Sb3 alloy

We demonstrate an advanced approach using advanced in-situ transmission electron microscopy (TEM) to understand the interplay between nanostructures and thermoelectric (TE) properties of high-performance Mg-doped Zn4Sb3 TE system. With the technique, microstructure and crystal evolutions of TE material have been dynamically captured as a function of temperature from 300 K to 573 K. On heating, we have observed clearly precipitation and growth of a Zn-rich secondary phase as nanoinclusions in the matrix of primary Zn4Sb3 phase. Elemental mapping by STEM-EDX spectroscopy reveals enrichment of Zn in the secondary Zn6Sb5 nanoinclusions during the thermal processing without decomposition observed. Such nanostructure strongly enhances the phonon scattering resulting in the decrease in the thermal conductivity leading to a zT value of 1.4 at 718 K.