Influence of Transition Metal Charge Compensation Species on Phase Assemblage in Zirconolite Ceramics for Pu Immobilisation
Influence of Transition Metal Charge Compensation Species on Phase Assemblage in Zirconolite Ceramics for Pu Immobilisation
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DOI：
10.1557/adv.2020.100
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发表时间：
2020-01-01
期刊：
影响因子：
0.8
通讯作者：
Hyatt, N. C.
中科院分区：
文献类型：
--
作者：
Blackburn, L. R.;Sun, S. K.;Hyatt, N. C.
Pu在锆英石基质（CaZrTi 2 O 7）中的固定化是一种可行的处置途径。以Ce ~（4+）作为Pu ~（4+）的结构类似物，系统地研究了Pu ~（4+）进入锆英石Ca ~（2+）位的A位置换，以及三价M_3 ~+/Ti ~（4+）置换（其中M_3 ~+ = Fe，Al，Cr）。一个大致相似的相组合的锆英石-2M和次要的钙钛矿时，观察到目标低水平的Ce掺入。随着目标Ce分数升高，第二相形成受到M3+物质选择的影响。Ce/Fe的共掺入导致少量含Ce的钙钛矿相在高废物负荷下的稳定化，而对于Cr 3+掺入观察到相当大的相分离。最有利的取代方法似乎是使用Al 3+实现的，因为没有观察到钙钛矿或游离CeO 2。然而，含铝试样的高温处理导致形成二次含Ce的灰云母相。
Immobilisation of Pu in a zirconolite matrix (CaZrTi2O7) is a viable pathway to disposition. A-site substitution, in which Pu4+ is accommodated into the Ca2+ site in zirconolite, coupled with sufficient trivalent M3+/Ti4+ substitution (where M3+ = Fe, Al, Cr), has been systematically evaluated using Ce4+ as a structural analogue for Pu4+. A broadly similar phase assemblage of zirconolite-2M and minor perovskite was observed when targeting low levels of Ce incorporation. As the targeted Ce fraction was elevated, secondary phase formation was influenced by choice of M3+ species. Co-incorporation of Ce/Fe resulted in the stabilisation of a minor Ce-containing perovskite phase at high wasteloading, whereas considerable phase segregation was observed for Cr3+ incorporation. The most favourable substitution approach appeared to be achieved with the use of Al3+, as no perovskite or free CeO2 was observed. However, high temperature treatments of Al containing specimens resulted in the formation of a secondary Ce-containing hibonite phase.