Order-disorder phase structure, microstructure and aqueous durability of (Gd, Sm)2(Zr, Ce)2O7 ceramics for immobilizing actinides

Abstract

Abstract In this paper, to identify the order-disorder structure and performance of (Gd, Sm)2(Zr, Ce)2O7 ceramic as the host matrices for immobilizing actinides, various contents of Sm/Ce co-incorporated (Gd, Sm)2(Zr, Ce)2O7 ceramics were designed and fabricated. The influences of various Sm/Ce doping contents on the order-disorder structure of the samples were investigated systematically by XRD and Raman analysis. The microstructure, elemental composition and distribution of the samples were analyzed by SEM-EDX approach. The aqueous durability of the specimens was also evaluated by a static leaching experiment. The results showed that the Gd/Zr-sites of Gd2Zr2O7 pyrochlore could be concurrently substituted by various contents of Sm/Ce. The phase structure of the as-prepared (Gd, Sm)2(Zr, Ce)2O7 ceramics were transformed from the ordered pyrochlore phase to the disordered defect-fluorite phase with decreasing the average r[(Gd, Sm)3+]/r[(Zr, Ce)4+] radius ratio after substitution. And the ceramics fabricated in this study presented high densification and excellent aqueous durability.