Light ion irradiation effects on stuffed Lu2(Ti2−xLux)O7−x/2 (x=0, 0.4 and 0.67) structures

Li, Y.H.; Wang, Y.Q.; Zhou, Mi; Xu, Chunping; Valdez, James A.; Sickafus, Kurt E.

doi:10.1016/j.nimb.2011.05.036

Cited by 23 publications

(16 citation statements)

References 20 publications

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“…This is consistent with the results reported by Li [21]. This is also consistent with the results reported by Li [21]. 3(a) may due either to "particle size broadening" or "strain broadening" [22,23].…”

Section: Unirradiated Gd 2 Ce X Zr 2-x O 7 (0≤x≤2)supporting

confidence: 92%

Preparation and heavy-ion irradiation effects of Gd₂Ce_xZr_2−xO₇ ceramics

Ding

Shu

et al. 2015

RSC Adv.

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A number of compositions with general stoichiometry of Gd 2 Ce x Zr 2-x O 7 (0≤x≤2) ceramics have been synthesized and received irradiation test at room temperature with Xe 20+ ions in a broad fluence range. X-ray diffraction (XRD) measurements shows that Gd 2 Ce x Zr 2-x O 7 (0≤x≤0.2) samples adopt the pyrochlore structure, whereas Gd 2 Ce x Zr 2-x O 7 (0.2≤x≤2.0) samples predominantly displayed an anion deficient fluorite structure, indicating that the structures of Gd 2 Ce x Zr 2-x O 7 are determined by the content of doped Ce 4+ ion. XRD results of irradiated samples (Gd 2 Zr 2 O 7 , Gd 2 Ce 2 O 7 ) indicate that Gd 2 Zr 2 O 7 was transformed into a radiation resistant anion deficient fluorite structure with increasing fluence, whereas the Gd 2 Ce 2 O 7 was partially amorphized. It was found that the structural evolutions induced by irradiation are strongly dependent on the samples composition and ions fluence. In addition, SEM results show that the density and hardness of waste forms play an important role in the morphology modifications induced by irradiation. These results would be considered for design and elaboration of future matrices for actinide immobilization or transmutation. 2 actinide wastes. They have been considered as a key component in synroc-based pyrochlore ceramics for geological immobilization of surplus Pu in the US [1]. It is very important that suitable waste form materials should be radiation resistant in geological repository. During long term storage, nuclear waste forms are submitted to severe radiations which induce atomic rearrangements. These structural modifications lead to the deterioration of physic-chemical properties of waste form materials.The pyrochlores under consideration in this study typically exhibit the A 2 B 2 O 7 stoichiometry, where actinides or lanthanides can be incorporated into the eight-coordinated A-site and metals occupy the six-coordinated B-site. Ordered A 2 B 2 O 7 pyrochlores belong to the Fd-3m space group, which is a superstructure of the ideal fluorite structure (Fm-3 space group) with twice the lattice constant. A and B cations occupy the 16c (0,0,0) and 16d (0.5,0.5,0.5) sites, respectively, and oxygens are located at the 48f (x,0.125,0.125) and 8b (0.375,0.375,0.375) positions (using Wyckoff notation). The anion sublattice can be completed by adding missing oxygens in the 8a site to form the anion-deficient fluorite structure. It is well known that the stability of pyrochlore structure is governed by the ratio of the ionic radii of A and B cation (rA/rB). The range of pyrochlore stability extends from 1.46 for Gd 2 Zr 2 O 7 to 1.78 for Sm 2 Ti 2 O 7 . For smaller ionic radii ratios, rA/rB < 1.46, anion-deficient fluorite is a stable structure, whilst the monoclinic structure is stable for ionic radii ratios rA/rB >1.78 [2,3].Given that nuclear waste forms will be subject to considerable α-recoil radiation damage in geological repository, it is important to understand effect of radiation on the pyrochlore structure. Considerable work has been carri...

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Section: Unirradiated Gd 2 Ce X Zr 2-x O 7 (0≤x≤2)supporting

confidence: 92%

Preparation and heavy-ion irradiation effects of Gd₂Ce_xZr_2−xO₇ ceramics

Ding

Shu

et al. 2015

RSC Adv.

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“…The increase in the intensity of the hump located near the (222) diffraction peak (∼30°) in the diffraction patterns from the implanted Gd 2 Ti 2−x Sn x O 7 materials also shows that these materials become partially amorphous with increasing dose (i.e., 1 × 10 15 to 5 × 10 15 ions/ cm 2 ). 58 Comparison of the μ-XRD patterns from the Gd 2 Ti 2−x Sn x O 7 and Gd 2 Zr 2 O 7 samples that were implanted to the same dose (5 × 10 15 ions/cm 2 ; Figure 3) shows that Gd 2 Ti 2−x Sn x O 7 becomes partially amorphous while the diffraction pattern from implanted Gd 2 Zr 2 O 7 does not show an amorphous hump at ∼30°. This observation is likely a result of Gd 2 Zr 2 O 7 preferring to undergo a phase transition to the defect-fluorite structure upon ion implantation rather than become amorphous.…”

Section: Methodsmentioning

confidence: 99%

Investigation of the Structural Stability of Ion-Implanted Gd₂Ti_2–xSn_xO₇ Pyrochlore-Type Oxides by Glancing Angle X-ray Absorption Spectroscopy

et al. 2014

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Rare-earth titanate and stannate pyrochlore-type oxides have been investigated in the past for the sequestration of nuclear waste elements because of their resistance to radiation-induced structural damage. In order to enhance this property, it is necessary to understand the effect of radioactive decay of the incorporated actinide elements on the local chemical environment. In this study, Gd 2 Ti 2−x Sn x O 7 materials have been implanted with Au − ions to simulate radiation-induced structural damage. Glancing angle X-ray absorption near-edge spectroscopy (GA-XANES), glancing angle X-ray absorption fine structure (GA-EXAFS) analysis, and powder X-ray diffraction have been used to investigate changes in the local coordination environment of the metal atoms in the damaged surface layer. Examination of GA-XANES/EXAFS spectra from the implanted Gd 2 Ti 2−x Sn x O 7 materials collected at various glancing angles allowed for an investigation of how the local coordination environment around the absorbing atoms changed at different depths in the damaged surface layer. This study has shown the usefulness of GA-XANES to the examination of ion-implanted materials and has suggested that Gd 2 Ti 2−x Sn x O 7 becomes more susceptible to ion-beam-induced structural damage with increasing Sn concentration.

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“…The intensity of the amorphous hump located at $30°in the diffraction patterns from the implanted RE 2 Ti 2 O 7 materials gradually decreases with decreasing ionic radii of the RE cation (Sm ? Yb) [50,67]. It has been previously demonstrated by examination of ion-implanted crystallites of RE 2 Ti 2 O 7 by TEM that these materials become less prone to ion-beam induced amorphization with decreasing ionic radii of the RE cation [7].…”

Section: Powder X-ray Diffraction Before and After Ion Implantationmentioning

confidence: 99%

An investigation of the electronic structure and structural stability of RE2Ti2O7 by glancing angle and total electron yield XANES

Aluri

Grosvenor

2014

Journal of Alloys and Compounds

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a b s t r a c tPyrochlore-type oxides (A 2 B 2 O 7 ) have been investigated for nuclear waste sequestration applications due to their overall resistance to radiation-induced structural damage. This damage can be simulated by implanting the materials with high-energy ions to aid in understanding how the structure of a crystalline material responds to radioactive decay of incorporated nuclear waste elements. RE 2 Ti 2 O 7 (RE = La-Lu), Yb 1.85 Ca 0.15 Ti 2 O 7Àd , and Yb 2 Ti 1.85 Fe 0.15 O 7Àd were synthesized by the ceramic method and investigated by Ti K-edge X-ray absorption near edge spectroscopy (XANES) and powder X-ray diffraction before and after being implanted by 2 MeV Au À ions. Surface sensitive total electron yield (TEY) XANES spectra and glancing-angle (GA) XANES spectra were collected to study the ion-implanted materials. It was necessary to use these surface sensitive detection methods because the 2 MeV Au À ions only implant to $450 nm into the surface of the materials. An effective sample mounting procedure has been developed that uses conductive silver paint to collect high quality TEY-XANES spectra from the damaged surface layer of the implanted pellets so as to minimize charging effects. This investigation has shown that the local coordination number of Ti decreased after implantation, and that the degree of damage observed decreases with decreasing radius of the RE cation. The study has also shown that the oxygen vacancies generated by a slight substitution of Yb 3+ for Ca 2+ or Ti 4+ for Fe 3+ does not considerably affect the resistance of Yb 2 Ti 2 O 7 to radiation-induced damage.

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Light ion irradiation effects on stuffed Lu2(Ti2−xLux)O7−x/2 (x=0, 0.4 and 0.67) structures

Cited by 23 publications

References 20 publications

Preparation and heavy-ion irradiation effects of Gd₂Ce_xZr_2−xO₇ ceramics

Preparation and heavy-ion irradiation effects of Gd₂Ce_xZr_2−xO₇ ceramics

Investigation of the Structural Stability of Ion-Implanted Gd₂Ti_2–xSn_xO₇ Pyrochlore-Type Oxides by Glancing Angle X-ray Absorption Spectroscopy

An investigation of the electronic structure and structural stability of RE2Ti2O7 by glancing angle and total electron yield XANES

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Light ion irradiation effects on stuffed Lu2(Ti2−xLux)O7−x/2 (x=0, 0.4 and 0.67) structures

Cited by 23 publications

References 20 publications

Preparation and heavy-ion irradiation effects of Gd2CexZr2−xO7 ceramics

Preparation and heavy-ion irradiation effects of Gd2CexZr2−xO7 ceramics

Investigation of the Structural Stability of Ion-Implanted Gd2Ti2–xSnxO7 Pyrochlore-Type Oxides by Glancing Angle X-ray Absorption Spectroscopy

An investigation of the electronic structure and structural stability of RE2Ti2O7 by glancing angle and total electron yield XANES

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About

Preparation and heavy-ion irradiation effects of Gd₂Ce_xZr_2−xO₇ ceramics

Preparation and heavy-ion irradiation effects of Gd₂Ce_xZr_2−xO₇ ceramics

Investigation of the Structural Stability of Ion-Implanted Gd₂Ti_2–xSn_xO₇ Pyrochlore-Type Oxides by Glancing Angle X-ray Absorption Spectroscopy