Temperature-dependent elastic moduli of lead telluride-based thermoelectric materials

In the open literature, reports of mechanical properties are limited for semiconducting thermoelectric materials, including the temperature dependence of elastic moduli. In this study, for both cast ingots and hot-pressed billets of Ag-, Sb-, Sn- and S-doped PbTe thermoelectric materials, resonant ultrasound spectroscopy (RUS) was utilized to determine the temperature dependence of elastic moduli, including Young's modulus, shear modulus and Poisson's ratio. This study is the first to determine the temperature-dependent elastic moduli for these PbTe-based thermoelectrics, and among the few determinations of elasticity of any thermoelectric material for temperatures above 300 K. The Young's modulus and Poisson's ratio, measured from room temperature to 773 K during heating and cooling, agreed well. Also, the observed Young's modulus, E, versus temperature, T, relationship, E(T) = E0(1-bT), is consistent with predictions for materials in the range well above the Debye temperature. A nanoindentation study of Young's modulus on the specimen faces showed that both the cast and hot-pressed specimens were approximately elastically isotropic.