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Title: Temperature Dependence Discontinuity in the Stability of Manganese doped Ceria Nanocrystals

CeO 2 has strong potential for chemical-looping water splitting. It has been shown that manganese doping decreases interface energies of CeO 2, allowing increased stability of high surface areas in this oxygen carrier oxide. The phenomenon is related to the segregation of Mn3+ at interfaces, which causes a measurable decrease in excess energy. Here in the present work, it is shown that, despite the stability of nanocrystals of manganese-doped CeO 2 with relation to undoped CeO 2, the effect is strongly dependent on the oxidation state of manganese, i.e., on the temperature. At temperatures below 800 °C, Mn is in the 3+ valence state, and coarsening is hindered by the reduced interface energetics, showing smaller crystal sizes with increasing Mn content. At temperatures above 800 °C, Mn is reduced to its 2+ valence state, and coarsening is enhanced with increasing Mn content. Atomistic simulations show the segregation of Mn to grain boundaries is relatively insensitive to the charge state of the dopant. However, point defect modeling finds that the reduced state causes a decrease in cation vacancy concentration and an increase in cation interstitials, reducing drag forces for grain boundary mobility and increasing growth rates.
Authors:
 [1] ;  [2] ; ORCiD logo [2] ; ORCiD logo [1]
  1. Univ. of California, Davis, CA (United States). Dept. of Materials Science & Engineering and NEAT ORU
  2. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Publication Date:
Report Number(s):
LA-UR-16-23824
Journal ID: ISSN 1528-7483
Grant/Contract Number:
AC52-06NA25396
Type:
Accepted Manuscript
Journal Name:
Crystal Growth and Design
Additional Journal Information:
Journal Volume: 17; Journal Issue: 2; Journal ID: ISSN 1528-7483
Publisher:
American Chemical Society
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; 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
OSTI Identifier:
1369181