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Title: In-situ transmission electron microscopy study of oxygen vacancy ordering and dislocation annihilation in undoped and Sm-doped CeO 2 ceramics during redox processes

Ceria (CeO 2) based ceramics have been widely used for many applications due to their unique ionic, electronic, and catalytic properties. We report our findings in investigating into the redox processes of undoped and Sm-doped CeO 2 ceramics stimulated by high-energy electron beam irradiation within a transmission electron microscope (TEM). The reduced structure with oxygen vacancy ordering has been identified as the CeO 1.68 (C-Ce 2O 3+δ) phase via high-resolution TEM. The reduction of Ce 4+ to Ce 3+ has been monitored by electron energy-loss spectroscopy. The decreased electronic conductivity of the Sm-doped CeO 2 (Sm 0.2Ce 0.8O 1.9, SDC) is revealed by electron holography, as positive electrostatic charges accumulated at the surfaces of SDC grains under electron beam irradiation, but not at CeO 2 grains. The formation of the reduced CeO 1.68 domains corresponds to lattice expansion compared to the CeO 2 matrix. Therefore, the growth of CeO 1.68 nuclei builds up strain inside the matrix, causing annihilation of dislocations inside the grains. By using in-situ high-resolution TEM and a fast OneView camera recording system, we investigated dislocation motion inside both CeO 2 and SDC grains under electron beam irradiation. The dislocations prefer to dissociate into Shockley partials boundedmore » by stacking faults. Then, the partials can easily glide in the {111} planes to reach the grain surfaces. Even the Lomer-Cottrell lock can be swept away by the phase change induced strain field. Our results revealed the high mobility of dislocations inside CeO 2 and SDC grains during their respective redox processes« less
Authors:
ORCiD logo [1] ;  [1] ;  [1] ;  [1] ;  [1]
  1. Georgia Inst. of Technology, Atlanta, GA (United States). School of Materials Science and Engineering
Publication Date:
Grant/Contract Number:
AR0000502; DMR-1505319
Type:
Accepted Manuscript
Journal Name:
Journal of Applied Physics
Additional Journal Information:
Journal Volume: 120; Journal Issue: 21; Journal ID: ISSN 0021-8979
Publisher:
American Institute of Physics (AIP)
Research Org:
Georgia Inst. of Technology, Atlanta, GA (United States). Georgia Tech Research Corp. (GTRC)
Sponsoring Org:
USDOE Advanced Research Projects Agency - Energy (ARPA-E); National Science Foundation (NSF)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 47 OTHER INSTRUMENTATION; high resolution transmission electron microscopy; stacking faults; doping; redox; electron energy loss spectroscopy; dislocations; electron beams; electron radiation effects; vacancies
OSTI Identifier:
1465125
Alternate Identifier(s):
OSTI ID: 1334351