The effect of Ce content on structure and stability of Gd1-xCexPO4: Theory and experiment

Abstract

The structure distortion, bonding character, defect stability and chemical stability of Gd1-xCexPO4 (x = 0, 0.25, 0.5, 0.75 and 1) have been investigated by combined with experimental and first principles calculations to understand the effect simulate actinides on the structural stability of Gd-monazite. The result shows that the Gd1-xCexPO4 (x = 0–1) ceramics could be prepared at 1450 °C, and Ce3+ is easily incorporated into Gd-monazite lattice. The structural analysis indicates that the symmetry of [GdO9] polyhedron decreases with increasing Ce content. The evolution of Gd defect stability and chemical stability in Gd1-xCexPO4 (x = 0–1) is tightly associated with the distortion of [GdO9] polyhedron, in which a greater distortion will induce more unstable. The best chemical stability in pH = 3 and 11 leachates is CePO4, followed by GdPO4, Gd0.75Ce0.25PO4, Gd0.5Ce0.5PO4, and finally Gd0.25Ce0.75PO4, revealing the GdPO4 monazite is perfectly suitable to immobilize actinides with relative low dose ratio.