Damage accumulation and amorphization in samarium titanate pyrochlore

Damage accumulation in Sm2Ti2O7 single crystals irradiated with Au2+ ions at 170, 300 and 700 K was studied by Rutherford backscattering spectrometry using a 2.0 MeV He+ beam along the channeling direction. The relative disorder on the Sm sublattice follows a nonlinear dependence on ion fluence. The nonlinear behavior is described well by a disorder accumulation model that indicates a predominant role of a defect-stimulated amorphization process. The critical dose for amorphization at 300 K is similar to0.14 dpa, which is in good agreement with in situ transmission electron microscopy results for polycrystalline Sm2Ti2O7 irradiated with 600 keV Bi+ ions and with Gd2Ti2O7 doped with Cm-244. Despite the six orders of magnitude difference in damage rates, the good agreement between the amorphization doses in Sm2Ti2O7 at 300 K and Cm-244-doped Gd2Ti2O7 at 340 K indicates that damage accumulation at these temperatures is relatively independent of dose rate. (C) 2003 Elsevier B.V. All rights reserved