The ion irradiation tolerance of the fluorite RE2MO5 (RE = Sm, and Yb, M = Ti, Zr, and Sn) system

Abstract

In the search for novel ceramics for use within nuclear fuel-related applications and nuclear waste-form matrices, a major focus has been on the development of radiation-tolerant materials. Of particular interest in this field have been numerous compounds with either pyrochlore or the related fluorite-type structures. In this study, we look to expand the family of compounds with defect fluorite-type structure. We have fabricated three new compounds; Yb 2 Sn 1.125 O 5.25 , Yb 2 Sn 1.25 O 5.5 , and Yb 2 Sn 1.375 O 5.75 . The compound Yb 2 Sn 1.125 O 5.25 was determined, via x-ray diffraction, to have the long-range defect fluorite structure, Fm-3 m symmetry, with cell parameter a = 5.17233(1). Further to this, Sm 2 ZrO 5 and Yb 2 TiO 5 compounds were also fabricated and crystal structures characterised. The use of transmission electron microscopy has revealed a much more complex crystal structure than that of the relatively high symmetry fluorite, with the presence of structural modulations being detected. The ion-irradiation response of these compounds was tested via bulk specimen irradiation using 15-MeV gold ions with grazing incidence x-ray diffraction characterisation. The results show that both Sm 2 ZrO 5 and Yb 2 Sn 1.25 O 5.5 are highly tolerant to ion-irradiation exposure whilst Yb 2 TiO 5 is susceptible to amorphisation.