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This content will become publicly available on May 4, 2018

Title: Disorder-induced transition from grain boundary to bulk dominated ionic diffusion in pyrochlores

In this paper, we use molecular dynamics simulations to investigate the role of grain boundaries (GBs) on ionic diffusion in pyrochlores, as a function of the GB type, chemistry of the compound, and level of cation disorder. We observe that the presence of GBs promotes oxygen transport in ordered and low-disordered systems, as the GBs are found to have a higher concentration of mobile carriers with higher mobilities than in the bulk. Thus, in ordered samples, the ionic diffusion is 2D, localized along the grain boundary. When cation disorder is introduced, bulk carriers begin to contribute to the overall diffusion, while the GB contribution is only slightly enhanced. In highly disordered samples, the diffusive behavior at the GBs is bulk-like, and the two contributions (bulk vs. GB) can no longer be distinguished. There is thus a transition from 2D/GB dominated oxygen diffusivity to 3D/bulk dominated diffusivity versus disorder in pyrochlores. Finally, these results provide new insights into the possibility of using internal interfaces to enhance ionic conductivity in nanostructured complex oxides.
Authors:
ORCiD logo [1] ;  [1] ; ORCiD logo [1]
  1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Publication Date:
Report Number(s):
LA-UR-17-23205
Journal ID: ISSN 2040-3364; TRN: US1703116
Grant/Contract Number:
AC52-06NA25396
Type:
Accepted Manuscript
Journal Name:
Nanoscale
Additional Journal Information:
Journal Volume: 9; Journal Issue: 20; Journal ID: ISSN 2040-3364
Publisher:
Royal Society of Chemistry
Research Org:
Los Alamos National Lab. (LANL), Los Alamos, NM (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
OSTI Identifier:
1402631