Title: In-situ re-crystallization of heavily-irradiated Gd₂Ti₂O₇

Abstract

Gadolinium titanate (Gd₂Ti₂O₇, or GTO) and other lanthanide pyrochlores are interesting candidates for actinide waste disposal and fast ion conduction because the relevant material properties are intimately dependent on local cation structure. Therefore, a deep understanding of the kinetics associated with cation ordering and disordering is required if such material properties are to be tuned for specific device designs. To this end, single crystals of GTO were irradiated with 190 keV helium ions to a total fluence of 1 × 10¹⁷ ions/cm², amorphizing the sample surface to a depth of ~1 μm and resulting in significant He bubble accumulation. FIB lamellae lifted out from the irradiated sections were examined during heat treatment in the (scanning) transmission electron microscope. Two distinct stages of the re-crystallization of the amorphized material were observed. The material near the end of the ions’ range transformed first and with the same orientation as the pristine material. This was due to the close proximity of the pristine material and the presence of small defect fluorite seeds, but the propagation of this growth front was frustrated by the large pores (formerly bubbles) in the He accumulation layer. This was followed by heterogeneous nucleation of new crystallites at randommore » orientations at the top of the He accumulation layer, which is attributed to the high surface area associated with the many small He bubbles in that region. Finally, it is inferred that the kinetics of grain growth in this material are significantly faster than the kinetics of grain nucleation.« less

Authors:

Janish, Matthew Thomas  ^[1];

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• Search DOE PAGES for ORCID "0000-0002-4844-7931"

Schneider, Matthew M.  ^[1];

• Search DOE PAGES for author "Schneider, Matthew M."
• Search DOE PAGES for ORCID "0000-0002-7425-7736"

Valdez, James Anthony ^[1]; Mcclellan, Kenneth James  ^[1];

• Search DOE PAGES for author "Mcclellan, Kenneth James"
• Search DOE PAGES for ORCID "0000-0002-3503-6754"

Byler, Darrin David  ^[1];

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• Search DOE PAGES for ORCID "0000-0002-5456-8334"

Wang, Yongqiang  ^[1];

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• Search DOE PAGES for ORCID "0000-0002-2938-5640"

Chen, Di ^[2]; Holesinger, Terry George  ^[1];

• Search DOE PAGES for author "Holesinger, Terry George"
• Search DOE PAGES for ORCID "0000-0002-1155-1006"

Uberuaga, Blas P.  ^[1]

• Search DOE PAGES for author "Uberuaga, Blas P."
• Search DOE PAGES for ORCID "0000-0001-6934-6219"

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+ Show Author Affiliations

1. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
2. Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Univ. of Houston, TX (United States)

Publication Date:

Thu May 14 00:00:00 EDT 2020

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); USDOE National Nuclear Security Administration (NNSA)

OSTI Identifier:

1630875

Report Number(s):

LA-UR-19-32263
Journal ID: ISSN 1359-6454

Grant/Contract Number:  

89233218CNA000001

Resource Type:

Accepted Manuscript

Journal Name:

Acta Materialia

Additional Journal Information:

Journal Volume: 194; Journal Issue: C; Journal ID: ISSN 1359-6454

Publisher:

Elsevier

Country of Publication:

United States

Language:

English

Subject:

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; pyrochlore; ion irradiation; in situ; STEM; crystallization