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Title: Electronic Structure and Phase Stability of Yb-filled CoSb3 Skutterudite Thermoelectrics from First Principles

Journal Article · · Chemistry of Materials

Filling the large voids in the crystal structure of the skutterudite CoSb3 with rattler atoms R provides an avenue for both increasing carrier concentration and disrupting lattice heat transport, leading to impressive thermoelectric performance. While the influence of R on the lattice dynamics of skutterudite materials has been wellstudied, the phase stability of R-filled skutterudite materials and the influence of the presence and ordering of R on the electronic structure remain unclear. Here, focusing on the Ybfilled skutterudite YbxCo4Sb12, we employ first-principles methods to compute the phase stability and electronic structure. Yb-filled CoSb3 exhibits (1) a mild tendency for phase separation into Yb-rich and Yb-poor regions and (2) a strong tendency for chemical decomposition into Co-Sb and Yb-Sb binaries (i.e., CoSb3, CoSb2, and YbSb2). We find that, at reasonable synthesis temperatures, configurational entropy stabilizes single-phase solid solutions with limited Yb solubility, in agreement with experiments. Filling CoSb3 with Yb increases the band gap, enhances the carrier effective masses, and generates new low-energy “emergent” conduction band minima, which is distinct from the traditional band convergence picture of aligning the energies of existing band extrema. The explicit presence of R is necessary to achieve the emergent conduction band minima, though the rattler ordering does not strongly influence the electronic structure. The emergent conduction bands are spatially localized in the Yb-rich regions, unlike the delocalized electronic states at the Brillouin zone center that form the unfilled skutterudite band edges.

Research Organization:
Northwestern Univ., Evanston, IL (United States)
Sponsoring Organization:
USDOE Office of Science (SC), Basic Energy Sciences (BES)
Grant/Contract Number:
SC0014520; AC02-05CH11231; ACI-1548562
OSTI ID:
1546770
Alternate ID(s):
OSTI ID: 1776862
Journal Information:
Chemistry of Materials, Vol. 31, Issue 16; ISSN 0897-4756
Publisher:
American Chemical Society (ACS)Copyright Statement
Country of Publication:
United States
Language:
English
Citation Metrics:
Cited by: 15 works
Citation information provided by
Web of Science

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