Chemical reactivity and ion beam irradiation behaviour of perovskite- and zirconolite-nuclear ceramics type

摘要

Oxide ceramics of two neighboring families: perovskite A(Ⅱ)B(Ⅳ)O_3 and zirconolite A(Ⅱ)B(Ⅳ)C(Ⅳ)_2O_7 have been synthesized by a classical solid route. Substitution of divalent cation (Ca) by trivalent cation (Nd) was tested on zirconolite compositions. Then, the ceramic pellets were submitted to aqueous leaching tests at 90℃ in deionized water. Some of them were previously ion irradiated with 150 keV Xe~+ within a fluence range 5 x 10~(13)-1 x 10~(15) cm~(-2) in order to study the effect of ion damaging on their intrinsic chemical reactivity. X-ray diffraction (XRD), electron microprobe analysis (EMA), scanning electron microscopy (SEM) and ion beam analysis (IBA) methods were used to characterize the evolution of the crystallinity level and the surface chemical composition of the ceramics after each step (synthesis, irradiation, leaching). The alteration mechanism of unirradiated titanate ceramics appears to be not uniform at the sample surface. Chemical durability of zirconolite is shown to be dependent both on the pH of the aqueous solution and the ceramic composition. Surface hydration only concerns a very thin layer, typically 200 nm and the hydrogen content does not go beyond 1-2 at.%. No differences have been detected in the leaching behaviour of unirradiated or irradiated perovskite samples.