Since the 1960’s, NASA has implemented Radioisotope Thermoelectric Generators to supply energy for many of its satellites and space probes. Nonetheless, mechanical integrity for the full operational life of the thermoelectric modules has not been given much consideration in such applications. Among many contributors, clamping forces, vibrational stresses, and thermally-induced mismatch stresses may combine to give stress levels high enough to deform the thermoelectric module by creep, thus diminishing its useful lifetime.
In the present talk, we show the case of the compressive creep deformation behavior of two thermoelectric materials; half-Heusler Hf0.3Zr0.7NiSn0.98Sb0.02 and Skutterudite Yb0.3CoSb3¬ alloys, at 500-705 ºC. Hf0.3Zr0.7NiSn0.98Sb0.02 exhibits Newtonian flow, consistent with diffusional creep of its fine-grain microstructure. In addition to its promising thermoelectric performance at high temperatures, this alloy sustains very high compressive stresses (359 MPa) at 600⁰C without macroscopic failure. On the other side, Yb0.3CoSb3¬ showed modest creep resistance, governed by viscous glide of dislocations.