Title: In-situ transmission electron microscopy study of oxygen vacancy ordering and dislocation annihilation in undoped and Sm-doped CeO₂ ceramics during redox processes

Abstract

Ceria (CeO₂) 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 CeO₂ 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-Ce₂O_3+δ) phase via high-resolution TEM. The reduction of Ce⁴⁺ to Ce³⁺ has been monitored by electron energy-loss spectroscopy. The decreased electronic conductivity of the Sm-doped CeO₂ (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 CeO₂ grains. The formation of the reduced CeO_1.68 domains corresponds to lattice expansion compared to the CeO₂ 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 CeO₂ and SDC grains under electron beam irradiation. The dislocations prefer to dissociate into Shockley partials bounded by stacking faults. Then, the partials can easily glide in the {111} planes to reach themore » 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 CeO₂ and SDC grains during their respective redox processes« less

Authors:

Ding, Yong  ^[1];

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Chen, Yu ^[1]; Pradel, Ken C. ^[1]; Liu, Meilin ^[1]; Lin Wang, Zhong ^[1]

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+ Show Author Affiliations

1. Georgia Inst. of Technology, Atlanta, GA (United States). School of Materials Science and Engineering

Publication Date:

Fri Dec 02 00:00:00 EST 2016

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)

OSTI Identifier:

1465125

Alternate Identifier(s):

OSTI ID: 1334351

Grant/Contract Number:  

AR0000502; DMR-1505319

Resource 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)

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