A comparison of the local structure in ball-milled and hand ground skutterudite samples using EXAFS

Abstract

a b s t r a c tSkutterudites are considered to be good thermoelectrics with high figures of merit, ZT. After synthesis, electrodes are created by grinding and hot pressing the resulting powder. Materials such as NdFe 4 Sb 12 exhibit a significantly greater figure of merit, ZT, (about 43%) when it is ball milled to produce fine powders (inital powder 160 nm; after hot pressing~330 nm). This enhancement is typically attributed to the reduced particle size, 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 particles formed by ball milling, which could also affect its thermal conductivity. Using a temperature dependent, Extended X-ray Absorption Fine Structure (EXAFS) analysis of a hand ground and ball milled sample of the skutterudite Nd y Fe 4 Sb 12 , we have determined that ball milling causes no significant damage to the local structure around any site. Consequently further improvements in ZT may be possible with smaller particles.

CoSb3-based skutterudite nanocomposites prepared by cold sintering process with enhanced thermoelectric properties

“…The skutterudites form a large class of compounds with many novel properties depending on their composition [1,2]. Particularly, skutterudites usually exhibit potential thermoelectric properties due to a high Seebeck coefficient and a reasonable electrical conductivity, but a relatively high thermal conductivity [3][4][5][6][7]. Many of the interesting properties of skutterudites as thermoelectric materials depend on their unusual cubic crystal structure, containing two large voids often filled with a variety of atoms: e.g., rare earths, alkaline earths, etc.…”

Local structure investigation of Ga and Yb dopants in Co4Sb12 skutterudites

“…The interference patterns in the EX-AFS spectra can be used to obtain quantitative information about the local structure near an absorbing atom. During the past three decades, an accurate and general theoretical treatment of EXAFS spectra has emerged, and the development of analysis packages such as FEFF has made the EXAFS technique a reliable method for local structure determination [46][47][48][49][50][51][52] . EXAFS has significant advantages for detecting doped impurities at very low atomic concentrations, thanks to its element sensitivity.…”