Free occupied design to immobilize CeO2 by high-entropy pyrochlore

Multi-component high-entropy pyrochlore (HEP) offers several advantages compared to single-component pyrochlore in solidifying radioactive waste , including the ability to solubilize multiple types of waste and lower leaching rates (LRs) of radionuclides . In this study, we successfully synthesized HEP (Y 0.2 Nd 0.2 Sm 0.2 Eu 0.2 Gd 0.2 ) 2 Zr 2 O 7 and immobilized Ce, a simulated nuclide of Pu at 1500 °C for 48 h using a free occupied design approach. The Raman, XRD , and Rietveld refinement results showed that the immobilization limit for Ce fell between 20  wt .% and 30  wt .%. Notably, the ordered pyrochlore phase gradually transformed into the defective fluorite phase with an increase in Ce content. Moreover, the leaching tests demonstrated the excellent stability of the matrix, with the normalized LR for Ce reaching 10 −7 g·m −2 ·L −1 after 42 days at 90 °C. These findings collectively suggest that HEP (Y 0.2 Nd 0.2 Sm 0.2 Eu 0.2 Gd 0.2 ) 2 Zr 2 O 7 holds promise as a substrate for immobilizing radioactive waste in the future.