Radiation effects in lanthanum pyrozircoiriate

The present paper reviews recent results on radiation resistance of lanthanum pyrozirconate La2Zr2O7 obtained through molecular dynamic simulations using empirical potentials. Detailed studies of displacement cascades carried out with a 6 keV U4+ cation, representing the a-recoil nucleus, have shown only point-defects formation, Frenkel pairs and cation antisites, indicating that in this material amorphization does not occur by a direct impact mechanism. In a more enhanced simulation study, the consequences of point-defect accumulation have been analyzed. The results show that cation Frenkel pair accumulation is the driving force for lanthanum zirconate amorphization. It is demonstrated that under cation Frenkel pair accumulation, the crystal undergoes a transition from the pyrochlore to the disordered fluorite structure, with the oxygen atoms simply rearranging around cations and next to the amorphous state. Consequently, these results provide atomic-level interpretation to experimental observations of a two-step phase transition under irradiation. (c) 2006 Elsevier B.V. All rights reserved.