Porosity dependence of elastic moduli in LAST (Lead–antimony–silver–tellurium) thermoelectric materials

Porosity in thermoelectric materials affects the thermal, electrical and mechanical properties of the materials. In this study, the resonant ultrasound spectroscopy technique was used to determine the Youngʹs modulus, E, shear modulus, G, and Poissonʹs ratio, ν, of 12 hot pressed and five cast polycrystalline specimens of the thermoelectric material LAST (lead–antimony–silver–tellurium) as a function of volume fraction porosity, P, for P ranging from 0.01 to 0.14. A least-squares fit of the Youngʹs and shear moduli data to the relationships E = ED(1 − bPEP) and G = GD(1 − bPGP), respectively yielded ED = 58.4 ± 0.6 GPa and GD = 23.0 ± 0.2 GPa, where ED and GD are the estimated Youngʹs modulus and shear modulus at room temperature for theoretically dense specimens, respectively. The unitless, material-dependent constants bPE and bPG were bPE = 3.5 ± 0.2 and bPG = 3.5 ± 0.2.