Characterisation of Ti and Sr atomic environments in SrTiO3 before and after ion beam irradiation by X-ray absorption spectroscopy

Perovskite phases and particularly SrTiO3 are good candidates for radioactive waste immobilisation. To simulate disorder induced by recoil-nuclei, SrTiO3 has been irradiated with Pb ions and characterized by X-ray absorption spectroscopy and X-ray diffraction. The absorption coefficients have been measured at the Ti K and Sr K edges. The analysis of the absorption coefficients (near edge structures and fine structures above the edge) provide a description of the atomic surrounding of Ti and Sr atoms in a virgin single crystal sample and in a disordered one considered as amorphous. A phase transformation from SrTiO3 to Sr2TiO4 has been detected that is confirmed by X-ray diffraction. The occurrence of this phase transformation allows us to explain the nature of the defects and the dechanneling yield obtained in previous experiments by Rutherford backscattering spectrometry associated with channelling.