Synthesis and crystalline phase of monazite-type Ce1−xGdxPO4 solid solutions for immobilization of minor actinide curium

Gadolinium (Gd3+) was used to simulate trivalent minor actinide curium (Cm3+), and monazite-type solid solutions with composition of Ce1−xGdxPO4 (x = 0–1) were prepared by the solid state reaction method using Ce2(C2O4)3·10H2O, NH4H2PO4, and Gd2O3 as starting materials. The effects of Gd content on the crystalline phase and microstructure of Ce1−xGdxPO4 solid solutions were investigated, and the calcining parameters of Ce0.9Gd0.1PO4 solid solution were optimized by means of XRD, TG-DSC and SEM. The results show that pure monazite-type crystalline phase was obtained for the Ce1−xGdxPO4 with x = 0–1, and the incorporation of minor actinide curium simulated by gadolinium in monazite was confirmed. The change of Gd content had no significant effect on the microstructure of Ce1−xGdxPO4 solid solutions, and the grain size was approximately 0.1–1 μm. Besides, the optimal calcining temperature and holding time of Ce0.9Gd0.1PO4 solid solution were 1000 °C and 2 h, respectively.