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Title: Structure and Stoichiometry in Supervalent Doped Li7La3 Zr2O12

The oxide garnet material Li7La3 Zr2O12 shows remarkably high ionic conductivity when doped with supervalent ions that are charge compensated by Li vacancies and is currently one of the best candidates for development of a technologically relevant solid electrolyte. Determination of optimal dopant concentration, however, has remained a persistent problem due to the extreme difficulty of establishing the actual (as compared to nominal) stoichiometry of intentionally doped materials and by the fact that it is still not entirely clear what level of lattice expansion/contraction best promotes. ionic diffusion. By combining careful synthesis, neutron diffraction, high-resolution X-ray diffraction (XRD), Raman measurements, and density functional theory calculations, we show that structure and stoichiometry are intimately related such that the former can in many cases be used as a gauge of the latter. We show that different Li-vacancy creating supervalent ions (Al3+ vs Ta5+) affect the structure very differently, both in terms of the lattice constant, which is easily measurable, and hi terms of the local structure, which can be difficult or impossible to access experimentally but may have important ramifications for conduction. We carefully correlate the lattice constant to dopant type/concentration via Vegard's law and then further correlate these quantities to relevantmore » local structural parameters. In conclusion, our work opens the possibility of developing a codopant scheme that optimizes the Li vacancy concentration and the lattice size simultaneously.« less
Authors:
 [1] ;  [2] ;  [2] ;  [3] ;  [4] ;  [4] ;  [5] ;  [1] ;  [5]
  1. Cornell Univ., Ithaca, NY (United States). Nanoscale Facility
  2. Michigan State Univ., East Lansing, MI (United States). Dept. of Chemical Engineering and Materials Science
  3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  4. Army Research Laboratory, Adelphi, MD (United States)
  5. Naval Research Lab. Washington, DC (United States). Center for Computational Materials Science
Publication Date:
OSTI Identifier:
1261440
Grant/Contract Number:
AC05-00OR22725; 1066406; SC001054
Type:
Accepted Manuscript
Journal Name:
Chemistry of Materials
Additional Journal Information:
Journal Volume: 27; Journal Issue: 10; Journal ID: ISSN 0897-4756
Publisher:
American Chemical Society (ACS)
Research Org:
Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE