Creep behavior and post-creep thermoelectric performance of the n-type Skutterudite alloy Yb_0.3Co₄Sb₁₂

Upon uniaxial compressive loading at 500 °C (T/T_m = 0.67, where T_m is the absolute melting point), the n-type Skutterudite alloy Yb_0.3Co₄Sb₁₂ deforms plastically by creep via a power-law, with a stress exponent ∼3 consistent with dislocation viscous glide. An activation energy of 171 kJ/mol is measured over the temperature range of 500–587 °C (T/T_m = 0.67–0.75) at a stress of 30 MPa. Yb_0.3Co₄Sb₁₂ is ductile at 500 °C, exhibiting a compressive strain of 25% when subjected to stresses ranging from 22 to 90 MPa for up to 28 days. Among the thermoelectric materials tested so far for creep, Yb_0.3Co₄Sb₁₂ exhibits a creep resistance intermediate between low-melting (Bi₂Te₃, TAGS-85) and high-melting thermoelectrics (Mg₂Si and ZrNiSn). A relatively modest drop in the figure of merit zT, from 0.67 to 0.52, is displayed by Yb_0.3Co₄Sb₁₂ after accumulating 3.7% compressive creep strain at 500 °C, mostly due to a drop in electrical conductivity.