Effect of disorder on the thermal transport and elastic properties in thermoelectric Zn4 Sb3

Zn4 Sb3 undergoes a phase transition from α to β phase at T1 ≈250 K. The high temperature β- Zn4 Sb3 phase has been widely investigated as a potential state-of-the-art thermoelectric (TE) material, due to its remarkably low thermal conductivity. We have performed electronic and thermal transport measurements exploring the structural phase transition at 250 K. The α to β phase transition manifests itself by anomalies in the resistivity, thermopower, and specific heat at 250 K as well as by a reduction in the thermal conductivity as Zn4 Sb3 changes phase from the ordered α to the disordered β -phase. Moreover, measurements of the elastic constants using resonant ultrasound spectroscopy (RUS) reveal a dramatic softening at the order-disorder transition upon warming. These measurements provide further evidence that the remarkable thermoelectric properties of β- Zn4 Sb3 are tied to the disorder in the crystal structure.