Structural investigations of (Ca,Sr)ZrO3(Ca,Sr)ZrO_{3} and Ca(Sn,Zr)O3Ca(Sn,Zr)O_{3} perovskite compounds.

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An attempt to correlate ion irradiation behaviour and chemical durability of titanate- and zirconate-based ceramics

International audienceTitanate and zirconate samples from perovskite and pyrochlore families have been submitted to low energy heavy ion irradiation in order to pre-damage their crystalline structure. Samples irradiated below or near their amorphisation threshold were then leached in deionised water at 90 degrees C in static mode while samples irradiated above their amorphisation threshold were leached at 100 degrees C in dynamic mode. Below the amorphisation threshold, only slight effects of the pre-irradiation have been found on the chemical durability of titanate and zirconate from the perovskite family. Above the amorphisation threshold, perovskite surfaces exhibit a stronger hydration and an increase of the growth kinetics of secondary phases identified as TiOOH and ZrOOH compounds mainly. The pre-irradiated pyrochlore (Nd(2)Zr(2)O(7)) exhibits both a higher hydration degree and a higher Nd-Zr surface co-enrichment due to the destabilization of their network by the pre-irradiation. (C) 2008 Elsevier B.V. All rights reserved

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

International audienceOxide ceramics of two neighboring families: perovskite A(II)B(IV)O-3 and zirconolite A(II)B(IV)C(IV)(2)O-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 degrees C 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. (c) 2006 Elsevier B.V. All rights reserved