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Title: Effects of partial La filling and Sb vacancy defects on CoS b 3 skutterudites

Over the past decade, the open frame ("cagey") structure of CoSb 3 skutterudite has invited intensive filling studies with various rare-earth elements for delivering state-of-the-art mid-temperature thermoelectric performance. In order to rationalize previously reported experimental results and provide new insight into the underexplored roles of La fillers and Sb vacancies, ab initio density functional theory studies, along with semi-classical Boltzmann transport theory calculations, are performed for pristine CoSb 3 of different lattice settings and La-filled CoSb 3 with and without Sb s mono- and di-vacancy defects. We examine the effects of van der Waals (vdW) interactions, spin-orbit coupling (SOC), spin polarization, partial La-filling, and Sb vacancy defects on the structural, electronic, and thermoelectric properties. The vdW interactions profoundly affect the lattice constant, which in turn affects the band gap. The SOC shows minor effects on the electronic and thermoelectric properties. The peculiar quasi-Dirac band in the pristine CoSb 3 largely survives La filling but not Sb vacancies, which instead introduce dispersive bands in the band gap region. Importantly, the band structure, density of states, and Fermi surface of La-filled CoSb 3 are significantly spin polarized, giving rise to spin-dependent thermoelectric properties. Seebeck coefficients directly calculated as a function of chemicalmore » potential are interpreted in connection with the electronic structures. Temperature-dependent Seebeck coefficients derived for the experimentally studied materials agree well with available experimental data. Seebeck coefficients obtained as a function of charge carrier concentration corroborate a thermoelectrically favorable role at high filling fractions played by the electron/hole pockets on the Fermi surface associated with the degenerate valleys/hills in the conduction/valence bands, respectively. Our results serve to advance the understanding of CoSb 3 skutterudite, a class of materials with important fundamental and application implications for thermoelectrics and spintronics.« less
Authors:
 [1] ;  [2] ;  [2] ;  [2] ;  [3] ;  [2] ;  [2] ;  [4] ;  [4] ;  [4] ;  [4]
  1. Clemson Univ., SC (United States). Dept. of Mechanical Engineering; Univ. of Minnesota, Minneapolis, MN (United States). Dept. of Mechanical Engineering
  2. Clemson Univ., SC (United States). Dept. of Physics and Astronomy
  3. Clemson Univ., SC (United States). Dept. of Mechanical Engineering
  4. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Center for Nanophase Materials Sciences and Computational Sciences and Engineering Division
Publication Date:
Grant/Contract Number:
AC05-00OR22725; AC02-05CH11231
Type:
Accepted Manuscript
Journal Name:
Physical Review B
Additional Journal Information:
Journal Volume: 95; Journal Issue: 16; Journal ID: ISSN 2469-9950
Publisher:
American Physical Society (APS)
Research Org:
Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States). Center for Nanophase Materials Sciences (CNMS)
Sponsoring Org:
USDOE Office of Science (SC)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE
OSTI Identifier:
1354662
Alternate Identifier(s):
OSTI ID: 1353134