Radiation effects in ferrate garnet
Journal
Journal of Nuclear Materials
Journal Volume
336
Journal Issue
2-3
Start Page
251
End Page
260
ISSN
0022-3115
Date Issued
2005-02
Author(s)
Abstract
Radiation effects in four synthetic ferrate garnets (A3B 2(XO4)3, Ia3d, Z = 8) were examined by ion beam irradiations with in situ observation (T = 298-873 K) using transmission electron microscopy (TEM) at the IVEM Tandem Facility at Argonne National Laboratory. The garnet compositions include: A = Ca, Gd, Th, and Ce; B = Zr, Fe. The critical amorphization temperatures (Tc), the temperature above which the target material cannot be amorphized due to dynamic annealing, were between 820 and 870 K. The amorphization doses at room temperature are between 0.17 and 0.19 dpa (displacement per atom), which is similar to that of silicate- and aluminate-garnets. The small variations in the amorphization dose and Tc of the different compositions suggest that radiation effects in ferrate garnets are structurally constrained. Qualitative analyses of the valence states of Ce and Fe in garnet before and after irradiation were completed using electron energy-loss spectroscopy (EELS). The Ce and Fe in the unirradiated garnet were dominantly trivalent and divalent, respectively. The characteristic peaks of Ce4+, at ∼5 eV higher energy for the M-edges, were present in unirradiated garnet as a minor peak, and the peaks did not disappear after complete amorphization, suggesting that the valence state did not change significantly. EELS analysis was conducted on a nearly pure andradite, Ca3Fe2Si3O12, which ideally contains only ferric iron. The andradite was amorphized at 0.18 dpa. EELS analysis revealed that some of ferric iron was converted to ferrous iron during the irradiation.
Subjects
Amorphization
Electron beams
Energy dissipation
Ion beams
Ion bombardment
Ionization
Oxidation
Radiation effects
Reduction
Silicates
Amorphization temperature
Electron energy-loss spectroscopy (EELS)
Ferrate garnet
Ferric iron
Garnets
Publisher
Elsevier BV
Type
journal article