Anomalous temperature-dependent Young's modulus of a cast LAST (Pb-Sb-Ag-Te) thermoelectric material

Thermomechanical characterization is important to material evaluation and device design in the development of thermoelectric technology. In this study, we utilize the resonant ultrasound spectroscopy (RUS) technique to examine the elastic behavior of a cast LAST (Pb-Sb-Ag-Te) material with a composition of Ag_0.86Pb₁₉Sb_1.0Te₂₀ between room temperature and 823 K. The temperature-dependent Young's modulus exhibits a monotonically decreasing trend with increasing temperature. However, an abnormal slope change in the Young's modulus-temperature curve around 500 K is observed. In addition, hysteresis between heating and cooling data in the temperature range of 450-550 K is observed, which appears to be dependent on the heating/cooling rate during the RUS experiments such that the hysteresis disappears when the heating/cooling rate was decreased from 5 to 2 K min^-1. In this study we propose an order-disorder transition model for the anomalous temperature-dependent Young's modulus behavior observed in this study.