Effect of disorder on the thermal transport and elastic properties in thermoelectric Zn₄Sb₃

Zn₄Sb₃ undergoes a phase transition from α to β phase at T₁≈250 K. The high temperature β-Zn₄Sb₃ 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 Zn₄Sb₃ 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-Zn₄Sb₃ are tied to the disorder in the crystal structure.