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Title: Local structure investigation of Ga and Yb dopants in Co 4 Sb 12 skutterudites

We report our x-ray absorption spectroscopy studies at both Ga K-edge and Yb L 2-edge to elucidate the local structure of Ga and Yb dopants in Yb xGa yCo 4Sb 12. Our extended x-ray absorption fine structure (EXAFS) data confirm that Ga atoms occupy two crystallographic sites: one is the 24g site replacing Sb, and the other is the 2a site in the off-center void position. We find that the occupancy ratio of these two sites varies significantly as a function of the filling fraction of additional Yb, which exclusively occupies the 2a on-center site. At low concentrations of Yb, Ga 24g and Ga 2a dopants coexist and they form a charge-compensated compound defect proposed by Qiu et al. [Adv. Mater. 23, 3194 (2013)]. The Ga 24g occupancy increases gradually with increasing Yb concentration, and almost all Ga occupies the 24g site for the highest Yb concentration (x = 0.4). In addition to the local crystal structure evidence provided by our EXAFS data, we also present x-ray absorption near-edge structure (XANES) spectra, which show a small Ga K-edge energy shift as a function of Yb concentration consistent with the change from predominantly Ga 2a to Ga 24g states. Our resultmore » suggests that the increased solubility of Yb in Yb-Ga co-doped Co 4Sb 12 skutterudites is due to the increased Ga 24g electron acceptor, and thus provides an important strategy to optimize the carrier concentration in partially filled skutterudites.« less
Authors:
 [1] ;  [2] ;  [1] ;  [3] ;  [2] ;  [4] ;  [4] ;  [1]
  1. Univ. of Toronto, ON (Canada). Dept. of Physics
  2. Canadian Light Source, Saskatoon (Canada)
  3. General Motors, Warren, MI (United States). Chemical and Materials Systems Lab, R&D Center
  4. Brookhaven National Lab. (BNL), Upton, NY (United States). Condensed Matter Physics and Materials Science Dept.
Publication Date:
Report Number(s):
BNL-203537-2018-JAAM
Journal ID: ISSN 2469-9950; PRBMDO
Grant/Contract Number:
SC0012704; EE0005432; RGPIN-2014-06071
Type:
Accepted Manuscript
Journal Name:
Physical Review B
Additional Journal Information:
Journal Volume: 96; Journal Issue: 22; Journal ID: ISSN 2469-9950
Publisher:
American Physical Society (APS)
Research Org:
Brookhaven National Laboratory (BNL), Upton, NY (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); USDOE Office of Energy Efficiency and Renewable Energy (EERE), Vehicle Technologies Office (EE-3V)
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY
OSTI Identifier:
1433993
Alternate Identifier(s):
OSTI ID: 1416449

Hu, Yanyun, Chen, Ning, Clancy, J. P., Salvador, James R., Kim, Chang-Yong, Shi, Xiaoya, Li, Qiang, and Kim, Young-June. Local structure investigation of Ga and Yb dopants in Co4Sb12 skutterudites. United States: N. p., Web. doi:10.1103/PhysRevB.96.224107.
Hu, Yanyun, Chen, Ning, Clancy, J. P., Salvador, James R., Kim, Chang-Yong, Shi, Xiaoya, Li, Qiang, & Kim, Young-June. Local structure investigation of Ga and Yb dopants in Co4Sb12 skutterudites. United States. doi:10.1103/PhysRevB.96.224107.
Hu, Yanyun, Chen, Ning, Clancy, J. P., Salvador, James R., Kim, Chang-Yong, Shi, Xiaoya, Li, Qiang, and Kim, Young-June. 2017. "Local structure investigation of Ga and Yb dopants in Co4Sb12 skutterudites". United States. doi:10.1103/PhysRevB.96.224107.
@article{osti_1433993,
title = {Local structure investigation of Ga and Yb dopants in Co4Sb12 skutterudites},
author = {Hu, Yanyun and Chen, Ning and Clancy, J. P. and Salvador, James R. and Kim, Chang-Yong and Shi, Xiaoya and Li, Qiang and Kim, Young-June},
abstractNote = {We report our x-ray absorption spectroscopy studies at both Ga K-edge and Yb L2-edge to elucidate the local structure of Ga and Yb dopants in YbxGayCo4Sb12. Our extended x-ray absorption fine structure (EXAFS) data confirm that Ga atoms occupy two crystallographic sites: one is the 24g site replacing Sb, and the other is the 2a site in the off-center void position. We find that the occupancy ratio of these two sites varies significantly as a function of the filling fraction of additional Yb, which exclusively occupies the 2a on-center site. At low concentrations of Yb, Ga24g and Ga2a dopants coexist and they form a charge-compensated compound defect proposed by Qiu et al. [Adv. Mater. 23, 3194 (2013)]. The Ga24g occupancy increases gradually with increasing Yb concentration, and almost all Ga occupies the 24g site for the highest Yb concentration (x = 0.4). In addition to the local crystal structure evidence provided by our EXAFS data, we also present x-ray absorption near-edge structure (XANES) spectra, which show a small Ga K-edge energy shift as a function of Yb concentration consistent with the change from predominantly Ga2a to Ga24g states. Our result suggests that the increased solubility of Yb in Yb-Ga co-doped Co4Sb12 skutterudites is due to the increased Ga24g electron acceptor, and thus provides an important strategy to optimize the carrier concentration in partially filled skutterudites.},
doi = {10.1103/PhysRevB.96.224107},
journal = {Physical Review B},
number = 22,
volume = 96,
place = {United States},
year = {2017},
month = {12}
}

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