Temperature-dependent Young's modulus, shear modulus and Poisson's ratio of p-type Ce_0.9Fe_3.5Co_0.5Sb₁₂ and n-type Co_0.95Pd_0.05Te_0.05Sb₃ skutterudite thermoelectric materials

摘要

Effective models of the mechanical behavior of thermoelectric materials under device conditions require knowledge of temperature-dependent elastic properties. Between room temperature and 600 K, resonant ultrasound spectroscopy measurements of three skutterudite thermoelectric materials, i.e. n-type Co_0.95Pd_0.05Te_0.05Sb₃ (both with and without 0.1 at.% cerium dopant) and p-type Ce_0.9Fe_3.5Co_0.5Sb₁₂, showed that the Young's and shear moduli decreased linearly with temperature at a rate of −0.021 GPa/K to −0.032 GPa/K, and −0.011 GPa/K to −0.013 GPa/K, respectively. In contrast, the Poisson's ratio was approximately 0.22 for the three materials and was relatively insensitive to temperature. For temperatures >600 K, the elastic moduli decreased more rapidly and resonance peaks broadened, indicating the onset of viscoelastic behavior. The viscoelastic relaxation of the moduli was least for Ce-doped n-type material, for which grain boundary precipitates may inhibit grain boundary sliding which in turn has important implications concerning creep resistance. In addition, powder processing of the n- and p-type materials should be done cautiously since submicron-sized powders of both the n- and p-type powders were pyrophoric.