|Understanding the Enhancement of the Figure of Merit of Ball Milled Skutterudites|
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UC Santa Cruz
Skutterudites are considered to be good thermoelectrics with high figures of merit, ZT. Generally they are created by grinding and hot pressing the resulting powder. Materials such as NdFe4Sb12 exhibit a significantly greater figure of merit (about 22%) when it is ball milled to produce powders of order 100 nm. This enhancement is typically attributed to the reduced particle size (two orders of magnitude), which in turn decreases the mean free path of phonons, and consequently decreases the thermal conductivity. This work aims to investigate whether there is any damage to the crystal structure in the 100 nm particles formed by ball milling which could also affect its thermal conductivity. Using temperature dependent, Extended x-ray absorption fine structure (EXAFS) analysis of a hand ground and ball milled sample of the skutterudite NdFe4Sb12, we have determined that ball milling causes no significant damage to the local structure.