An investigation of the electronic structure and structural stability of pyrochlore-type oxides and glass-ceramic composites

Pyrochlore-type oxides (A2B2O7) and glass-ceramic composites have been investigated for nuclear waste sequestration applications due to the remarkable compositional diversity and structural flexibility of these materials. These properties can enhance the incorporation of radioactive waste elements a...

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Other Authors: Grosvenor, Andrew P.
Language:English
Published: 2015
Subjects:
Online Access:http://hdl.handle.net/10388/ETD-2015-10-2284
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spelling ndltd-USASK-oai-ecommons.usask.ca-10388-ETD-2015-10-22842015-11-15T04:55:11ZAn investigation of the electronic structure and structural stability of pyrochlore-type oxides and glass-ceramic compositesPyrochloreNuclear wasteformsRadiation induced structural damageIon beam implantationXANESPyrochlore-type oxides (A2B2O7) and glass-ceramic composites have been investigated for nuclear waste sequestration applications due to the remarkable compositional diversity and structural flexibility of these materials. These properties can enhance the incorporation of radioactive waste elements and resistance to radiation induced structural damage. Radiation induced structural damage can be simulated by bombarding materials using high-energy heavy ions. The study has shown how the metal-oxygen bond covalency, cationic radii ratio (rA/rB), and oxygen vacancies of pyrochlore type oxides affect the resistance of these materials to radiation induced damage. RE2Ti2O7 (RE=La–Lu), Yb1.85Ca0.15Ti2O7-δ, Yb2Ti1.85Fe0.15O7-δ, and Gd2Ti2-xSnxO7 were synthesized by the ceramic method and investigated by X-ray absorption near edge spectroscopy (XANES), which allows for the study of the effect of elemental substitution on the electronic structure of materials. Surface sensitive glancing angle and total electron yield XANES (GA/TEY XANES) spectra have been used to study the damaged surface of the materials, as the high energy ions can only implant in the near-surface region (~ 450 nm) of the pellets. These measurements have allowed for an investigation of how the local structure of the materials changed after ion implantation and discussed in terms of coordination number and bonding environment. After investigating the ceramic materials, the glass-ceramic composite materials containing Gd2Ti2O7 pyrochlore type crystallites in a (borosilicate- and Fe-Al-borosilicate) glass were investigated. These glass-ceramic materials were synthesized and analyzed by backscattered electron (BSE) images and XANES spectra. The study has shown how the Gd2Ti2O7 crystallites interact within a glass matrix depending on glass composition, pyrochlore loading, and annealing temperature. Further, the GA-XANES spectra from these materials have shown that the glass ceramic composite materials show a similar response to ion implantation as pure ceramics (i.e., Gd2Ti2O7). All of these studies and techniques could provide a better understanding of how to develop and design materials for nuclear waste sequestration applications.Grosvenor, Andrew P.2015-11-14T12:00:16Z2015-11-14T12:00:16Z2015-102015-11-13October 2015textthesishttp://hdl.handle.net/10388/ETD-2015-10-2284eng
collection NDLTD
language English
sources NDLTD
topic Pyrochlore
Nuclear wasteforms
Radiation induced structural damage
Ion beam implantation
XANES
spellingShingle Pyrochlore
Nuclear wasteforms
Radiation induced structural damage
Ion beam implantation
XANES
An investigation of the electronic structure and structural stability of pyrochlore-type oxides and glass-ceramic composites
description Pyrochlore-type oxides (A2B2O7) and glass-ceramic composites have been investigated for nuclear waste sequestration applications due to the remarkable compositional diversity and structural flexibility of these materials. These properties can enhance the incorporation of radioactive waste elements and resistance to radiation induced structural damage. Radiation induced structural damage can be simulated by bombarding materials using high-energy heavy ions. The study has shown how the metal-oxygen bond covalency, cationic radii ratio (rA/rB), and oxygen vacancies of pyrochlore type oxides affect the resistance of these materials to radiation induced damage. RE2Ti2O7 (RE=La–Lu), Yb1.85Ca0.15Ti2O7-δ, Yb2Ti1.85Fe0.15O7-δ, and Gd2Ti2-xSnxO7 were synthesized by the ceramic method and investigated by X-ray absorption near edge spectroscopy (XANES), which allows for the study of the effect of elemental substitution on the electronic structure of materials. Surface sensitive glancing angle and total electron yield XANES (GA/TEY XANES) spectra have been used to study the damaged surface of the materials, as the high energy ions can only implant in the near-surface region (~ 450 nm) of the pellets. These measurements have allowed for an investigation of how the local structure of the materials changed after ion implantation and discussed in terms of coordination number and bonding environment. After investigating the ceramic materials, the glass-ceramic composite materials containing Gd2Ti2O7 pyrochlore type crystallites in a (borosilicate- and Fe-Al-borosilicate) glass were investigated. These glass-ceramic materials were synthesized and analyzed by backscattered electron (BSE) images and XANES spectra. The study has shown how the Gd2Ti2O7 crystallites interact within a glass matrix depending on glass composition, pyrochlore loading, and annealing temperature. Further, the GA-XANES spectra from these materials have shown that the glass ceramic composite materials show a similar response to ion implantation as pure ceramics (i.e., Gd2Ti2O7). All of these studies and techniques could provide a better understanding of how to develop and design materials for nuclear waste sequestration applications.
author2 Grosvenor, Andrew P.
author_facet Grosvenor, Andrew P.
title An investigation of the electronic structure and structural stability of pyrochlore-type oxides and glass-ceramic composites
title_short An investigation of the electronic structure and structural stability of pyrochlore-type oxides and glass-ceramic composites
title_full An investigation of the electronic structure and structural stability of pyrochlore-type oxides and glass-ceramic composites
title_fullStr An investigation of the electronic structure and structural stability of pyrochlore-type oxides and glass-ceramic composites
title_full_unstemmed An investigation of the electronic structure and structural stability of pyrochlore-type oxides and glass-ceramic composites
title_sort investigation of the electronic structure and structural stability of pyrochlore-type oxides and glass-ceramic composites
publishDate 2015
url http://hdl.handle.net/10388/ETD-2015-10-2284
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