Vanadium-driven surface engineering to suppress Sr segregation in perovskite ceramics for nuclear waste immobilization

The safe immobilization of radiotoxic strontium (Sr) in high-level radioactive waste (HLW) remains a major challenge due to its tendency to segregate and leach under aqueous conditions. In this study, a surface vanadium (V) engineering strategy is proposed to enhance the chemical stability of Sr 2 Fe 1.5 Mo 0.5 O 6-δ (SFM) ceramics. V-doped samples (SFMV), synthesized via a sol-gel method with 0.05 mol V partially substituting Mo, show improved resistance to Sr migration. DFT calculations reveal that V modification increases the Sr migration barrier from 0.14 eV (in SFM) to 0.34 eV (in SFMV) and induces the formation of strong Fe-O-V, and Mo–O–V effectively suppressing Sr surface segregation. Additionally, the formation of SrMoO 4 phases may act as Sr sinks, further enhancing stability. Leaching tests show that the Sr release from SFMV drops from 7.43 × 10 −4 to 2.89 × 10 −6 g·cm −2 ·d −1 over 42 days, representing a 64 % reduction compared to pristine SFM. This work provides a promising strategy for designing durable ceramic hosts for Sr-containing HLW.