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

A study of the local atomic structure of the promising thermoelectric material $\ensuremath{\beta}\text{\ensuremath{-}}{\mathrm{Zn}}_{4}{\mathrm{Sb}}_{3}$, 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 $\ensuremath{\beta}$ phase closely resembles that of the low-temperature $\ensuremath{\alpha}$ phase. The $\ensuremath{\alpha}$ structure contains ordered zinc interstitial atoms which are not long range ordered in the $\ensuremath{\beta}$ phase. A rough estimate of the domain size from a visual inspection of the PDF is $\ensuremath{\lesssim}10\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$. It is probable that the nanoscale domains found in this study play an important role in the exceptionally low thermal conductivity of $\ensuremath{\beta}\text{\ensuremath{-}}{\mathrm{Zn}}_{4}{\mathrm{Sb}}_{3}$.