Raman spectroscopy study of damage induced in cerium dioxide by swift heavy ion irradiations

The damage induced in cerium dioxide by swift heavy ion irradiation was studied by micro-Raman spectroscopy. For this purpose, polycrystalline sintered pellets were irradiated by 100-MeV Kr, 200-MeV Xe, 10-MeV, and 36-MeV W ions in a wide range of fluence and stopping power (up to ∼28 MeV μm^-1). No amorphization of ceria was found whatsoever, as shown by the presence of the peak of Raman-active T_2g mode (centered at 467 cm^-1) of the cubic fluorite structure for all irradiation conditions. However, a clear decrease of the T_2g mode peak intensity was observed as a function of ion fluence to an asymptotic relative value of about 45%. Similar decays were also observed for satellite peaks and second-order peaks. Track radii deduced from the decay kinetics for the 36-MeV W ion data are in good agreement with previous determinations by X-ray diffraction and reproduced by the inelastic thermal spike model for low ion velocities. However, interaction between the nuclear and electronic stopping powers is needed to describe the decay kinetics of 10-MeV W ion data by the thermal spike process. Moreover, the asymmetrical broadening of the main T_2g peak after irradiation was analyzed with different theoretical models.