University of California, Santa Cruz

Skutterudites are excellent thermoelectric materials with applications such as waste heat reclamation, where a temperature gradient is used to generate electrical current. The SmOs₄Sb₁₂  skutterudite has unusual properties that are speculated to arise from the large amplitude vibrations of the Sm “Rattler” atom in the surrounding "cage" of atoms. We used the Extended X-ray Absorption Fine Structure (EXAFS) technique to analyze the local structure about the Sm atom; this technique requires high intensity flux, available at Stanford Synchrotron Radiation Lightsource (SSRL). For the Sm data, the Sm-Sb and Sm-Os pairs both contribute to the EXAFS peak near 3.5 A. and the fit must include both pairs. The temperature dependence of σ² for each atom pair was determined as a function of temperature from 8-190 K and fit to an Einstein model.