Recently, unusual Raman signals were observed in different works conducted on thin zirconia layers grown on zirconium alloys simulating in-reactor materials after high fluence ion irradiation or for samples cut from fuel rods irradiated in nuclear plants. As such, these spectra clearly do not correspond to any known spectrum of a pure standard zirconia phase. Therefore, the analysis conducted in this paper aims to provide a better understanding of these peculiar Raman features. For that purpose, specific ion-irradiated samples were analysed. In situ Raman spectroscopy was first used to follow the irradiation process. Then, samples were characterized using different excitation wavelengths. Finally, the effects of oxygen isotopic substitution were examined in details. Results are discussed in terms of disorder and size-related effects.

The damage induced in uranium dioxide (UO 2) during ion irradiation at low energy was studied by micro-Raman spectroscopy. Polycrystalline UO 2 samples were irradiated by 0.9-MeV I, 2-MeV Au at 25°C and by 4-MeV Kr ions at-160°C in a wide range of fluence. In situ Raman measurements reveal similar spectra evolution no matter the ion beam used. The T 2g band centred at 445 cm-1 related to the fluorine structure reveals a broadening with the irradiation damage increase. In addition, several bands ranging from 500 to 700 cm-1 , which are attributed to sub-or sur-stoichiometric structural defects, are observed at the first time of irradiation. Their intensities rise up with the irradiation fluence increase to a similar asymptotic relative values for all the irradiation conditions. The obtained Raman kinetics are compared with data from the literature on the microstructure evolution observed by Transmission Electronic Microscopy (TEM) and on the fraction of displaced atoms determined by Rutherford Backscattering Spectroscopy in channelling mode (RBS-C).

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