Nanoscaleα-structural domains in the phonon-glass thermoelectric materialβ−Zn4Sb3

A study of the local atomic structure of the promising thermoelectric material $\beta \text{−}{\mathrm{Zn}}_4{\mathrm{Sb}}_3$, using atomic pair distribution function (PDF) analysis of x-ray- and neutron-diffraction data, suggests that the material is nanostructured. The local structure of the $\beta$ phase closely resembles that of the low-temperature $\alpha$ phase. The $\alpha$ structure contains ordered zinc interstitial atoms which are not long range ordered in the $\beta$ phase. A rough estimate of the domain size from a visual inspection of the PDF is $\lesssim 10\mathrm{nm}$. It is probable that the nanoscale domains found in this study play an important role in the exceptionally low thermal conductivity of $\beta \text{−}{\mathrm{Zn}}_4{\mathrm{Sb}}_3$.