Ion Irradiation Effects for Two Pyrochlore Compositions: Gd2Ti2O7 and Gd2Zr207

1998 ◽  
Vol 540 ◽  
Author(s):  
S. X. Wang ◽  
L. M. Wang ◽  
R. C. Ewing ◽  
K. V. Govindan Kutty
Keyword(s):  
Nuclear Waste ◽  
Ion Irradiation ◽  
Pyrochlore Structure ◽  
Fluorite Structure ◽  
Irradiation Effects ◽  
Critical Temperatures ◽  
Short Range Ordering ◽  
Radiation Induced ◽  
Diffraction Patterns ◽  
Ion Species

AbstractPyrochlore is an important nuclear waste form phase for actinide immobilization. Two synthetic pyrochlores, Gd2Ti2O7 and Gd2Zr2O7 were irradiated at various temperatures (25 K to 1073 K) by different ion species (1.5 MeV Xe+, 1.0 MeV Kr+, and 0.6 MeV Ar+). The titanate pyrochlore amorphized at relatively low doses (0.5 ∼ 0.6 dpa). Temperature dependence of the amorphization dose for titanate pyrochlore was measured, and the critical temperatures for amorphization were 1300 K, 1100 K and 950 K by 1.5 MeV Xe+, 1.0 MeV Kr+ and 0.6 MeV Ar+, respectively. The higher critical temperature for the heavier ion irradiation is consistent with an amorphization mechanism by which the heavier ion produces a larger cascade. The zirconate pyrochlore, Gd2Zr2O7, showed a strong amorphization “resistance”. Gd2Zr2O7did not become amorphous under 1.0 MeV Kr+ and 1.5 MeV Xe+ irradiation. After prolonged irradiation (up to 7 dpa) even at a temperature of 25 K, no amorphization was observed. The irradiated zirconate pyrochlore showed abundant dislocations as observed by TEM. The pyrochlore structure of Gd2Zr2O7 transformed to the fluorite structure after irradiation. The diffraction patterns of irradiated Gd2Zr2O7 showed the existence of short-range ordering of cations. The large difference between these two pyrochlores emphasizes the strong effect of chemical composition on radiation-induced amorphization.

TEM Study of Short-Range-Order in Zirconolite Induced by High Temperature Ion Irradiation

1999 ◽  
Vol 5 (S2) ◽  
pp. 756-757
Author(s):  
S. X. Wang ◽  
L. M. Wang ◽  
R. C. Ewing
Keyword(s):  
Oxygen Vacancies ◽  
Ion Irradiation ◽  
Pyrochlore Structure ◽  
Fluorite Structure ◽  
Waste Immobilization ◽  
Temperature Irradiation ◽  
High Level Nuclear Waste ◽  
Nuclear Waste Immobilization ◽  
Shortrange Order ◽  
High Level

Zirconolite (CaZrTi207) is an important phase proposed for high level nuclear waste immobilization. Zirconolite was irradiated by 1 MeV Kr+ at various temperatures. At room temperature, zirconolite became amorphous after a dose of 7x1014 ions/cm2.1 Amorphization dose increased with temperature due to thermal annealing. The critical temperature, above which amorphization does not occur, was estimated to be 654 K. During the low temperature irradiation (<654 K), concurrent with amorphization, zirconolite transformed from a monoclinic structure to the cubic pyrochlore structure and then to the fluorite substructure. The structural change is due to the disordering between cations and between oxygen and oxygen vacancies.After an irradiation at 673 K to a dose of 3.6x1015 ions/cm, the zirconolite samples remained crystalline. The diffraction pattern consists of strong maxima from the fluorite structure and diffuse maxima surrounding the Bragg positions of the pyrochlore superlattice (FIG. 1). Diffuse scattering patterns have been reported in other phases, and were generally attributed to the shortrange- order (SRO) domains.

scholarly journals Electron Beam Effects during In-Situ Annealing of Self-Ion Irradiated Nanocrystalline Nickel

2015 ◽  
Vol 1809 ◽  
pp. 13-18 ◽  
Author(s):  
Brittany Muntifering ◽  
Rémi Dingreville ◽  
Khalid Hattar ◽  
Jianmin Qu
Keyword(s):  
Electron Beam ◽  
Nuclear Reactor ◽  
Ion Irradiation ◽  
Nanocrystalline Nickel ◽  
Transmission Electron ◽  
Radiation Induced ◽  
Reactor Materials ◽  
Diffraction Patterns ◽  
Underlying Mechanisms

ABSTRACTTransmission electron microscopy (TEM) is a valuable methodology for investigating radiation-induced microstructural changes and elucidating the underlying mechanisms involved in the aging and degradation of nuclear reactor materials. However, the use of electrons for imaging may result in several inadvertent effects that can potentially change the microstructure and mechanisms active in the material being investigated. In this study, in situ TEM characterization is performed on nanocrystalline nickel samples under self-ion irradiation and post irradiation annealing. During annealing, voids are formed around 200 °C only in the area illuminated by the electron beam. Based on diffraction patterns analyses, it is hypothesized that the electron beam enhanced the growth of a NiO layer resulting in a decrease of vacancy mobility during annealing. The electron beam used to investigate self-ion irradiation ultimately significantly affected the type of defects formed and the final defect microstructure.

Structural modifications of Gd2Zr2-xTixO7 pyrochlore induced by swift heavy ions: Disordering and amorphization

2009 ◽  
Vol 24 (4) ◽  
pp. 1322-1334 ◽  
Author(s):  
M. Lang ◽  
F.X. Zhang ◽  
R.C. Ewing ◽  
Jie Lian ◽  
Christina Trautmann ◽  
...  
Keyword(s):  
Heavy Ions ◽  
Structural Changes ◽  
Pyrochlore Structure ◽  
Fluorite Structure ◽  
Structure Type ◽  
Electronic Energy ◽  
Inert Matrix ◽  
Swift Heavy Ions ◽  
Transmission Electron ◽  
Radiation Induced

The isometric, pyrochlore structure type, A2B2O7, exhibits a wide variety of properties that find application in a large number of different technologies, from electrolytes in solid oxide fuel cells to actinide-bearing compositions that can be used as nuclear waste forms or inert matrix nuclear fuels. Swift xenon ions (1.43 GeV) have been used to systematically modify different compositions in the Gd2Zr2-xTixO7 binary at the nanoscale by radiation-induced phase transitions that include the crystalline-to-amorphous and order-disorder structural transformations. Synchrotron x-ray diffraction, Raman spectroscopy, and transmission electron microscopy provide a complete and consistent description of structural changes induced by the swift heavy ions and demonstrate that the response of pyrochlore depends strongly on chemical composition. The high and dense electronic energy deposition primarily results in amorphization of Ti-rich pyrochlore; whereas the formation of the fully disordered, defect-fluorite structure is the dominant process for Zr-rich pyrochlore.

Heavy-ion irradiation effects on Gd2Zr2O7 ceramics bearing complex nuclear waste

2019 ◽  
Vol 771 ◽  
pp. 973-979 ◽  
Author(s):  
Xirui Lu ◽  
Xiaoyan Shu ◽  
Lan Wang ◽  
Dadong Shao ◽  
Haibin Zhang ◽  
...  
Keyword(s):  
Nuclear Waste ◽  
Ion Irradiation ◽  
Heavy Ion ◽  
Irradiation Effects ◽  
Heavy Ion Irradiation

Ion-Induced Amorphization of Murataite

2002 ◽  
Vol 713 ◽  
Author(s):  
Jie Lian ◽  
Sergey V. Yudintsev ◽  
Sergey V. Stefanovsky ◽  
Olga I. Kirjanova ◽  
Rodney C. Ewing
Keyword(s):  
Ion Irradiation ◽  
Ion Beam ◽  
National Laboratory ◽  
Argonne National Laboratory ◽  
Pyrochlore Structure ◽  
Fluorite Structure ◽  
In Situ Tem ◽  
Cell Parameters ◽  
Unit Cells ◽  
Radiation Resistant

ABSTRACTMurataite A4B2C7O22-x, where A = Na+, Ca2+, REE3+, An3+/4+; B = Mn2+/3+, Zn2+; C = Ti4+, Fe3+, Al3+; 0≤x≤1, is an isometric, derivative of the fluorite-structure. Murataite is potentially suitable as a phase for the immobilization of rare earth (REE) and actinide elements (An). Murataite structures with three-(3C), five-(5C), and eight-fold (8C) multiples of the fluorite unit cell parameters have been identified. Radiation-induced amorphization of murataite has been investigated by 1 MeV Kr+ ion irradiation of three ceramic samples produced by melting in a resistive furnace and a cold crucible at 1400-1600 °C. The 1 MeV Kr+ ion irradiations were performed at room temperature using IVEM-Tandem Facility at Argonne National Laboratory. Radiation damage was observed by in-situ TEM. Initially, the irradiation caused disordering of the murataite structure. Murataite was rendered fully amorphous at a dose of (1.7∼1.9)Á1018 ion/m2. The pyrochlore structure phase (2C) is more radiation resistant to ion irradiation-induced amorphization than the murataite structure. Combining results on murataite with those pyrochlore and fluorite, a generally increasing trend in the susceptibility to ion beam damage is found in the fluorite-related structures as a function of the increasing multiples of the fluorite unit cells.

Heavy Ion Irradiation of Zirconate Pyrochlores

2002 ◽  
Vol 713 ◽  
Author(s):  
J. Lian ◽  
L. M. Wang ◽  
J. Chen ◽  
R. C. Ewing ◽  
K. V. G. Kutty
Keyword(s):  
Ion Irradiation ◽  
Ion Beam ◽  
Amorphous State ◽  
Pyrochlore Structure ◽  
Fluorite Structure ◽  
Heavy Ion ◽  
Ionic Radii ◽  
Radiation Resistant ◽  
A Site ◽  
Nuclear Waste Forms

ABSTRACTZirconate pyrochlores, A2Zr2O7, are important potential nuclear waste forms for Puimmobilization. The binary Gd2(Ti2-xZrx)O7 has been shown to have increasing resistance to ionirradiation damage with the increasing Zr content, and Gd2Zr2O7 is radiation resistant to a 1 MeV Kr+ ion irradiation at 25 K to a dose of 5 dpa. In this study, a 1.5 MeV Xe+ irradiation was completed for zirconate pyrochlores A2Zr2O7 (A=La, Nd, Sm, Gd). The radiation resistance decreases with an increase of the ionic radius of A-site cation. La2Zr2O7 is the first zirconate pyrochlore to be amorphized by ion beam irradiation, and the critical amorphization temperature, Tc, is ∼310 K. The susceptibility of La2Zr2O7 to ion beam damage is related to its structure, which shows the largest deviation from the ideal fluorite structure. These results are also consistent with calculations of the cation antisite formation energy in the pyrochlore structure. The ion irradiation-induced pyrochlore-to-fluorite transformation occurred in all of the irradiated zirconate pyrochlore phases. Based on the results for Gd2Ti2-xZrxO7 and A2Zr2O7, the defect fluorite structures are stable when the ionic radii ratio rA/rB≤1.54; beyond this limit, the defect fluorite structure becomes increasingly unstable relative to the amorphous state.

Heavy-ion irradiation effects on uranium-contaminated soil for nuclear waste

2020 ◽  
pp. 124273
Author(s):  
Guilin Wei ◽  
Wenhong Han ◽  
Xiaoyan Shu ◽  
Fen Luo ◽  
Hexi Tang ◽  
...  
Keyword(s):  
Nuclear Waste ◽  
Contaminated Soil ◽  
Ion Irradiation ◽  
Heavy Ion ◽  
Irradiation Effects ◽  
Heavy Ion Irradiation

Radiation Induced Structural Changes in Normal Spinels

2007 ◽  
Vol 1043 ◽  
Author(s):  
David Simeone ◽  
Gianguido Baldinozzi ◽  
Dominique Gosset ◽  
Leo Mazerolles ◽  
Lionel Thome
Keyword(s):  
Radiation Effects ◽  
Structural Changes ◽  
Ion Irradiation ◽  
Atomic Scale ◽  
X Ray Diffraction ◽  
Unified Framework ◽  
X Ray ◽  
Transmission Electron ◽  
Radiation Induced ◽  
Diffraction Patterns

AbstractIon irradiation induced phase transformations in three normal spinel compounds MgAl2O4, MgCr2O4 and ZnAl2O4 have been investigated by X-ray diffraction, Raman spectroscopy and Transmission Electron Microscopy. This work presents a unified framework to describe the radiation effects in normal spinels. Irradiation modifies the atomic and mesoscopic structures of theses spinels in different ways. At the atomic scale, it produces the inversion of the cations in the spinel structure which can always be described within its usual Fd-3m space group. At the mesoscopic scale, it produces microdomains, responsible for the important changes in the X-ray diffraction patterns.

Microchemical and crystallographic characterisation of fluorite-based ceramic wasteforms

2006 ◽  
Vol 932 ◽  
Author(s):  
Martin C. Stennett ◽  
Neil C. Hyatt ◽  
Ewan R. Maddrell ◽  
Fergus G. F. Gibb ◽  
Guenter Moebus ◽  
...  
Keyword(s):  
Nuclear Waste ◽  
Spectroscopic Analysis ◽  
Pyrochlore Structure ◽  
Fluorite Structure ◽  
Chemical Compositions ◽  
Waste Streams ◽  
Major Phase ◽  
Electron Energy Loss ◽  
Quantitative Chemical ◽  
Ceramic Matrices

ABSTRACTA number of possible options have been proposed for the encapsulation and immobilisation of long lived actinide (Act) fractions in nuclear waste. Ceramics offer superior durability against chemical migration and the ability to be tailored to accommodate a variety ofdifferent waste streams. Research on the fabrication of dense, durable crystalline matrices for the safe disposal of fissile plutonium is ongoing and this study reports quantitative chemical, structural and spectroscopic analysis on fluorite based host phases.Ceramics based on the fluorite structure are known to be able to incorporate a variety of actinides and in this work two candidate ceramic matrices were investigated: a pyrochlore, Gd2Zr1.60Ce0.20Hf0.20O7; and a zirconolite, (Ca0.90Gd0.10)(Zr0.50Ce0.20Hf0.20Gd0.10)Ti2O7. The chemical compositions of the two major phases observed in the ‘zirconolite’ sample were consistent with the 2M and 4M zirconolite polytypes and the presence of the 4M structure was confirmed by Electron Diffraction (ED). The major phase in the ‘pyrochlore’ ceramic was confirmed by ED to have the pyrochlore structure. Electron Energy Loss Spectroscopy (EELS) data indicated the presence of both Ce3+ and Ce4+ in all the samples.

Sign in / Sign up

Export Citation Format

Share Document