Phase evolution and aqueous durability of Zr1−x−yCexNdyO2−y/2 ceramics designed to immobilize actinides with multi-valences

Abstract

Zr1−x−yCexNdyO2−y/2 ceramics, which were designed as waste form materials, were obtained by simultaneous substitution of Ce4+ and Nd3+ for Zr4+ in ZrO2. The influences of the simultaneous substitution of Ce and Nd on phase transformation of ZrO2 were investigated systematically. Also, the aqueous durability of the ceramics was evaluated. The results show that the phase transformation caused by the simultaneous substitution mainly relates to the total content of Ce and Nd. The ZrO2 ceramics containing Ce + Nd < 30 mol% exhibit both monoclinic and cubic phases, while the ceramics containing Ce + Nd ≥ 30 mol% are cubic phase. And the cubic phase can be stabilized by incorporating 30 mol% Ce + Nd. Moreover, LRi are modified by the incorporation of Ce and Nd, because of the presence of oxygen vacancies. The Nd and Ce co-doped zirconia waste form exhibit excellent aqueous durability (∼10−5 g m−2 d−1).