Natural nanostructure and superlattice nanodomains in AgSbTe₂

AgSbTe₂ has long been of interest for thermoelectric applications because of its favorable electronic properties and its low lattice thermal conductivity of ∼0.7 W/mK. In this work, we report new findings from a high-resolution transmission electron microscopy study revealing two nanostructures in single crystal Ag_1-xSb_1+xSb _2+x (with x = 0, 0.1, 0.2); (i) a rippled natural nanostructure with a period of ∼2.5-5 nm and (ii) superlattice ordered nanodomains consistent with cation ordering predicted in previous density functional theory studies. These nanostructures, combined with point-defects, probably serve as sources of scattering for phonons, thereby yielding a low lattice thermal conductivity over a wide temperature range.