Positron annihilation lifetime study of radiation-damaged natural zircons

Roberts, J. and Gaugliardo, P. and Farnan, I. and Zhang, M. and Vance, E. R. and Davis, J. and Karatchevtseva, I. and Knott, R. B. and Mudie, S. and Buckman, S. J. and Sullivan, J. P. (2016) Positron annihilation lifetime study of radiation-damaged natural zircons. Journal of Nuclear Materials, 471. pp. 44-50. ISSN 0022-3115 DOI 10.1016/j.jnucmat.2015.12.008

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Abstract

Zircons are a well-known candidate waste form for actinides and their radiation damage behaviour has been widely studied by a range of techniques. In this study, well-characterised natural single crystal zircons have been studied using Positron Annihilation Lifetime Spectroscopy (PALS). In some, but not all, of the crystals that had incurred at least half of the alpha-event damage of ∼1019 α/g required to render them structurally amorphous, PALS spectra displayed long lifetimes corresponding to voids of ∼0.5 nm in diameter. The long lifetimes corresponded to expectations from published Small-Angle X-ray Scattering data on similar samples. However, the non-observation by PALS of such voids in some of the heavily damaged samples may reflect large size variations among the voids such that no singular size can be distinguished or. Characterisation of a range of samples was also performed using scanning electron microscopy, optical absorption spectroscopy, Raman scattering and X-ray scattering/diffraction, with the degree of alpha damage being inferred mainly from the Raman technique and X-ray diffraction. The observed void diameters and intensities of the long lifetime components were changed somewhat by annealing at 700 °C; annealing at 1200 °C removed the voids entirely. The voids themselves may derive from He gas bubbles or voids created by the inclusion of small quantities of organic and hydrous matter, notwithstanding the observation that no voidage was evidenced by PALS in two samples containing hydrous and organic matter.

Item Type: Article
Uncontrolled Keywords: 2015AREP; IA70
Subjects: 03 - Mineral Sciences
Divisions: 03 - Mineral Sciences
Journal or Publication Title: Journal of Nuclear Materials
Volume: 471
Page Range: pp. 44-50
Identification Number: 10.1016/j.jnucmat.2015.12.008
Depositing User: Sarah Humbert
Date Deposited: 28 Apr 2016 11:29
Last Modified: 28 Apr 2016 11:29
URI: http://eprints.esc.cam.ac.uk/id/eprint/3648

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