The synthesis and chemical durability of Nd-doped single-phase zirconolite solid solutions

Abstract

Nd-doped single-phase zirconolite solid solutions was synthesized by solid-state reaction and following two steps of acid treatment. The phase composition, microstructure, and chemical durability of the zirconolite solid solutions were investigated. About 15 at% Nd was successfully stabilized into the zirconolite. The element mapping images of Ca, Zr, Nd and Ti show that all the elements are almost distributed homogeneously in the zirconolite waste forms. Product Consistency Test (PCT) was conducted under different pH values (pH = 5, 7 and 9) to evaluate the chemical durability of the Nd-doped zirconolite waste forms. The normalized element release rate of Ca (LRCa) in pH = 5 medium is higher than that of pH = 7 and 9, while the LRNd value remains almost unchanged under different pH values. The LRNd value is as low as 10−5 g m−2 d−1 after 42 days.