Criteria for bombardment-induced structural changes in non-metallic solids

Naguib, Hala F.; Kelly, Roger

doi:10.1080/00337577508242047

Cited by 528 publications

(107 citation statements)

References 73 publications

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“…It appears clearly that the GdO bond has the same ionicity in Gd 2 Ti 2 O 7 and Gd 2 Zr 2 O 7 , whereas a signicant dierence between the Ti-O and ZrO bonds is observed: TiO is signicantly more covalent than ZrO . Several works suggested that the bond type should be taken into account to explain the radiation behaviour of pyrochlores [23,35]. Naguib and Kelly correlated the radiation tolerance of non-metallic solids with the relative ionicity of the materials, demonstrating that more covalently bonded materials are more readily amorphized under heavy ion irradiation [35].…”

Section: Resultsmentioning

confidence: 99%

“…Several works suggested that the bond type should be taken into account to explain the radiation behaviour of pyrochlores [23,35]. Naguib and Kelly correlated the radiation tolerance of non-metallic solids with the relative ionicity of the materials, demonstrating that more covalently bonded materials are more readily amorphized under heavy ion irradiation [35]. Consequently, as it was experimentally observed that Gd 2 Zr 2 O 7 is more resistant to amorphization than Gd 2 Ti 2 O 7 , we conrm that the radiation tolerance of non-metallic compounds can be related to the covalent character of the metal oxygen bond.…”

Section: Resultsmentioning

confidence: 99%

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Phase Transformations in Pyrochlores Irradiated with Swift Heavy Ions: Influence of Composition and Chemical Bonding

et al. 2013

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Gd2Ti2O7 and Gd2Zr2O7 pyrochlores were irradiated with swift heavy ions in order to investigate the eects of the chemical composition on the structural changes induced by high electronic excitation. The XRD results show that the structural modications induced by irradiation with 93 MeV Xe ions are strongly dependent on the sample composition: Gd2Ti2O7 is readily amorphized, whereas Gd2Zr2O7 is transformed into a radiation-resistant anion-decient uorite structure. Atomistic simulations with the second-moment tight-binding QEq model allow us to calculate the lattice properties of both Gd2Ti2O7 and Gd2Zr2O7, and also to quantify the degree of covalency and ionicity in these compounds. These calculations clearly show that Gd2Ti2O7 is more covalent than Gd2Zr2O7, thus conrming that the amorphization resistance can be related to the covalent character of insulators.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Phase Transformations in Pyrochlores Irradiated with Swift Heavy Ions: Influence of Composition and Chemical Bonding

et al. 2013

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“…It possesses a high ionicity, undamaged state after being heated for less (NAGUIB and KELLY, 1975), and the Ca atoms than one hour at temperatures as low as 950°C. are arranged in cubic closest-packing.…”

Section: Zirconolitementioning

confidence: 99%

“…This is in contrast to the behav oxides with the fluortie-type structure have also iour of heavily damaged zircons. These miner been found to remain crystalline when bom als, when heated, reconstitute to a complex mix barded with high doses ( 10"ions/cm2) of ture of the oxides (CARTZ and FOURNELLE, energetic heavy ions (NAGUIB andKELLY, 1975). 1979).…”

Section: Zirconolitementioning

confidence: 99%

Alpha-recoil damage in natural zirconolite and perovskite.

Sinclair¹,

Ringwood²

1981

Geochem. J.

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Zirconolite (CaZrTi207) and perovskite (CaTi03) are key minerals in SYNROC , a ceramic material developed for the immobilization of high level nuclear reactor wastes. When these are incorporated in SYNROC, the long-lived radioactive actinide elements are preferentially partitioned into zirconolite and perovskite which are therefore subjected to the effects of alpha-recoil, resulting from the decay of these elements. These effects have been studied via X-ray and electron diffraction investigations of natural samples of zirconolite and perovskite of varying ages and varying uranium and thorium contents . The samples studied have received cumulative alpha doses ranging from 1.0 X 1018 to 1 .1 X 1020a/g. The upper limit corresponds to the alpha irradiation which would be received by the zirconolite in SYNROC containing 10 percent of high level waste over a period of 5 X 108 years.These studies show that zirconolites remain crystalline up to and beyond alpha doses of 2 X 1019a/g . This dose would have accumulated in such a SYNROC zirconolite after a million years of storage . Elec tron microscopy revealed that the grains were composed of small crystalline domains which possessed the defect fluorite-type structure. After a dose exceeding that which would be received by SYNROC in 100 million years, zirconolites appeared metamict when studied by X-ray diffraction . However, the elec tron micrographs and diffraction patterns clearly demonstrate that the mineral continues to retain a large degree of short range order and in no way resembles a glass. The density changes produced in these zir conolites by irradiation are small and range from 0 to 3 % at saturation.Perovskite samples which have SYNROC ages up to 20 ,000 years decrease in density by 1.8 ± 0.1 %. Their X-ray powder patterns are essentially unaffected. Comparative studies show that the perovskite lat tice is even more resistant to the effects of alpha-recoil than the zirconolite lattice. The results demonstrate that zirconolite and perovskite are extremely resistant to the effects of nuclear radiation and will provide stable crystal structures for the containment of the radioactive waste elements during the time required for the radioactivity to decay to safe levels (typically 101_106 years).

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“…An alternate, crystal -structure criterion was proposed by several investigators [citations in Naguib and Kelly, 1975]. In its usual formulation, this criterion states that anisotropic substances tend to amorphize under ion irradiation, whereas cubic substances tend to remain crystalline.…”

Section: Principles Of Materials Selectionmentioning

confidence: 99%

Irradiation damage in inorganic insulation materials for ITER magnets:

1994

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Criteria for bombardment-induced structural changes in non-metallic solids

Cited by 528 publications

References 73 publications

Phase Transformations in Pyrochlores Irradiated with Swift Heavy Ions: Influence of Composition and Chemical Bonding

Phase Transformations in Pyrochlores Irradiated with Swift Heavy Ions: Influence of Composition and Chemical Bonding

Alpha-recoil damage in natural zirconolite and perovskite.

Irradiation damage in inorganic insulation materials for ITER magnets:

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