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Title: Structure and Stoichiometry in Supervalent Doped Li 7La 3 Zr 2O 12

The oxide garnet material Li 7La 3 Zr 2O 12 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 (Al 3+ vs Ta 5+) 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 thenmore » further correlate these quantities to relevant 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
 [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:
Grant/Contract Number:
AC05-00OR22725; 1066406; SC001054
Accepted Manuscript
Journal Name:
Chemistry of Materials
Additional Journal Information:
Journal Volume: 27; Journal Issue: 10; Journal ID: ISSN 0897-4756
American Chemical Society (ACS)
Research Org:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
OSTI Identifier: