The temperature dependence of thermal expansion for p-type Ce _0.9Fe _3.5Co _0.5Sb ₁₂ and n-type Co _0.95Pd _0.05Te _0.05Sb ₃ skutterudite thermoelectric materials

During waste heat recovery applications, thermoelectric (TE) materials experience thermal gradients and thermal transients, which produce stresses that scale with the TE material's coefficient of thermal expansion (CTE). Thus, the temperature-dependent CTE is an important parameter for the design of mechanically robust TE generators. For three skutterudite thermoelectric compositions, n-type Co _0.95Pd _0.05Te _0.05Sb ₃ (with and without 0.1 at. % cerium doping) and p-type Ce _0.9Fe _3.5Co _0.5Sb ₁₂, the CTE was measured using two methods, i.e. X-ray diffraction on powder and bulk specimens and dilatometry on bulk specimens. Each bulk specimen was hot pressed using powders milled from cast ingots. Between 300K and 600 K, the mean CTE values were 9.8-10.3 times;10 ^-6 K ^-1 for the noncerium-doped n-type, 11.6times;10 ^-6 K ^-1 for the 0.1 at. % cerium-doped n-type and from 12.7 to 13.3 times;10-6 K ^-1 for the p-type. In the literature, similar CTE values are reported for other Sb-based skutterudites. For temperatures >600 K, an unrecovered dilatational strain (perhaps due to bloating) was observed, which may impact applications. Also, the submicron particle sizes generated by wet milling were pyrophoric; thus, during both processing and characterization, exposure of the powders to oxygen should be limited.