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Similar local order in disordered fluorite and aperiodic pyrochlore structures

Shamblin, Jacob and Tracy, Cameron L. and Palomares, Raul I. and O'Quinn, Eric C. and Ewing, Rodney C. and Neuefeind, Joerg and Feygenson, Mikhail and Behrens, Jason and Trautmann, Christina and Lang, Maik (2018):
Similar local order in disordered fluorite and aperiodic pyrochlore structures.
In: Acta Materialia, Elsevier Science Publishing, pp. 60-67, 144, ISSN 13596454,
DOI: 10.1016/j.actamat.2017.10.044,
[Online-Edition: https://doi.org/10.1016/j.actamat.2017.10.044],
[Article]

Abstract

A major challenge to understanding the response of materials to extreme environments (e.g., nuclear fuels/waste forms and fusion materials) is to unravel the processes by which a material can incorporate atomic-scale disorder, and at the same time, remain crystalline. While it has long been known that all condensed matter, even liquids and glasses, possess short-range order, the relation between fully-ordered, disordered, and aperiodic structures over multiple length scales is not well understood. For example, when defects are introduced (via pressure or irradiation) into materials adopting the pyrochlore structure, these complex oxides either disorder over specific crystallographic sites, remaining crystalline, or become aperiodic. Here we present neutron total scattering results characterizing the irradiation response of two pyrochlores, one that is known to disorder (Er2Sn2O7) and the other to amorphize (Dy2Sn2O7) under ion irradiation. The results demonstrate that in both cases, the local pyrochlore structure is transformed into similar short range configurations that are best fit by the orthorhombic weberite structure, even though the two compositions have distinctly different structures, aperiodic vs. disordered-crystalline, at longer length scales. Thus, a material's resistance to amorphization may not depend primarily on local defect formation energies, but rather on the structure's compatibility with meso-scale modulations of the local order in a way that maintains long-range periodicity.

Item Type: Article
Erschienen: 2018
Creators: Shamblin, Jacob and Tracy, Cameron L. and Palomares, Raul I. and O'Quinn, Eric C. and Ewing, Rodney C. and Neuefeind, Joerg and Feygenson, Mikhail and Behrens, Jason and Trautmann, Christina and Lang, Maik
Title: Similar local order in disordered fluorite and aperiodic pyrochlore structures
Language: English
Abstract:

A major challenge to understanding the response of materials to extreme environments (e.g., nuclear fuels/waste forms and fusion materials) is to unravel the processes by which a material can incorporate atomic-scale disorder, and at the same time, remain crystalline. While it has long been known that all condensed matter, even liquids and glasses, possess short-range order, the relation between fully-ordered, disordered, and aperiodic structures over multiple length scales is not well understood. For example, when defects are introduced (via pressure or irradiation) into materials adopting the pyrochlore structure, these complex oxides either disorder over specific crystallographic sites, remaining crystalline, or become aperiodic. Here we present neutron total scattering results characterizing the irradiation response of two pyrochlores, one that is known to disorder (Er2Sn2O7) and the other to amorphize (Dy2Sn2O7) under ion irradiation. The results demonstrate that in both cases, the local pyrochlore structure is transformed into similar short range configurations that are best fit by the orthorhombic weberite structure, even though the two compositions have distinctly different structures, aperiodic vs. disordered-crystalline, at longer length scales. Thus, a material's resistance to amorphization may not depend primarily on local defect formation energies, but rather on the structure's compatibility with meso-scale modulations of the local order in a way that maintains long-range periodicity.

Journal or Publication Title: Acta Materialia
Volume: 144
Publisher: Elsevier Science Publishing
Divisions: 11 Department of Materials and Earth Sciences > Material Science > Ion-Beam-Modified Materials
11 Department of Materials and Earth Sciences > Material Science
11 Department of Materials and Earth Sciences
Date Deposited: 29 Dec 2017 12:38
DOI: 10.1016/j.actamat.2017.10.044
Official URL: https://doi.org/10.1016/j.actamat.2017.10.044
Funders: This work was supported as part of by the Materials Science of Actinides, an Energy Frontier Research Center funded by the US Department of Energy, Office of Science, Basic Energy Sciences under Award # DE-SC0001089., J.S. acknowledges support from an Organized Research Unit from the Office of Research at the University of Tennessee., This research used resources at the Spallation Neutron Source, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory., R.I.P. acknowledges support from the US Department of Energy (DOE) National Nuclear Security Administration (NNSA) through the Carnegie DOE Alliance Center (CDAC) under grant number DE-NA-0002006.
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