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High-entropy ceramic strategy for immobilizing multi-radionuclides in zirconolite structure.

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Title: High-entropy ceramic strategy for immobilizing multi-radionuclides in zirconolite structure.
Authors: Wang, Keshen1 (AUTHOR), Fang, Shuohai1 (AUTHOR), Luo, Hui1 (AUTHOR), Yu, Lu1 (AUTHOR), Li, Dongmei1 (AUTHOR), Wu, Jiani1 (AUTHOR), Yin, Xiangbiao1,2 (AUTHOR) yinxb@usc.edu.cn, Yang, Wenchao1 (AUTHOR), Ma, Shengshou3 (AUTHOR), Shih, Kaimin3 (AUTHOR), Liao, Changzhong1,3 (AUTHOR) liaocz29@connect.hku.hk
Source: Ceramics International. May2026:Part B, Vol. 52 Issue 12, p20417-20425. 9p.
Subjects: Radioactive waste disposal, Oxide ceramics, Zirconium, Phase equilibrium, X-ray diffraction, Radioactive waste sites, Doping agents (Chemistry), Radioisotopes
Abstract: Effective high-level radioactive waste (HLW) immobilization is crucial for advancing nuclear energy. Zirconolite ceramics are a key material, known for their stability and durability. This study explores the potential of high-entropy zirconolite ceramics for disposing of multi-radionuclide high-level radioactive waste. A series of Ca 1-5x REE 5x ZrTi 2-5x Al 5x O 7 (REE-Al), Ca 1-5x REE 5x ZrTi 2-5x Fe 5x O 7 (REE-Fe) and Ca 1-5x REE 5x ZrTi 2-5x Al 2.5x Fe 2.5x O 7 (REE-Fe-Al) (REE = Nd, Sm, Gd, Ho, Yb; x = 0.05-0.20) were synthesized and characterized using XRD, SEM, XPS, and XAS techniques. Results show that zirconolite-2M remains the dominant phase up to x = 0.15. At higher doping levels (x ≥ 0.18), secondary phases such as cubic zirconia, baddeleyite in the REE-Al samples. In REE-Fe and REE-Al-Fe samples, both zirconolite-2M and zirconolite-3O can form, with a phase transformation from 2M to 3O occurring at x ≥ 0.18. XPS results confirm that the chemical states of all elements remain stable after high-temperature sintering. XANES analysis indicates that Al3+ ions substitute both Ti sites within the TiO 5 and TiO 6 coordination environments, with a preference for occupying the TiO 5 sites. EXAFS analysis indicates that while Zr substitution for Ca is minimal at low dopant levels, a substantial amount of Zr starts occupying Ca sites as doping concentration increases. This work demonstrates that high-entropy strategies dramatically enhance the compositional flexibility of zirconolite, enabling simultaneous incorporation of diverse charge-compensating dopants while maintaining structural and phase stability. [ABSTRACT FROM AUTHOR]
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Database: Engineering Source
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Abstract:Effective high-level radioactive waste (HLW) immobilization is crucial for advancing nuclear energy. Zirconolite ceramics are a key material, known for their stability and durability. This study explores the potential of high-entropy zirconolite ceramics for disposing of multi-radionuclide high-level radioactive waste. A series of Ca 1-5x REE 5x ZrTi 2-5x Al 5x O 7 (REE-Al), Ca 1-5x REE 5x ZrTi 2-5x Fe 5x O 7 (REE-Fe) and Ca 1-5x REE 5x ZrTi 2-5x Al 2.5x Fe 2.5x O 7 (REE-Fe-Al) (REE = Nd, Sm, Gd, Ho, Yb; x = 0.05-0.20) were synthesized and characterized using XRD, SEM, XPS, and XAS techniques. Results show that zirconolite-2M remains the dominant phase up to x = 0.15. At higher doping levels (x ≥ 0.18), secondary phases such as cubic zirconia, baddeleyite in the REE-Al samples. In REE-Fe and REE-Al-Fe samples, both zirconolite-2M and zirconolite-3O can form, with a phase transformation from 2M to 3O occurring at x ≥ 0.18. XPS results confirm that the chemical states of all elements remain stable after high-temperature sintering. XANES analysis indicates that Al3+ ions substitute both Ti sites within the TiO 5 and TiO 6 coordination environments, with a preference for occupying the TiO 5 sites. EXAFS analysis indicates that while Zr substitution for Ca is minimal at low dopant levels, a substantial amount of Zr starts occupying Ca sites as doping concentration increases. This work demonstrates that high-entropy strategies dramatically enhance the compositional flexibility of zirconolite, enabling simultaneous incorporation of diverse charge-compensating dopants while maintaining structural and phase stability. [ABSTRACT FROM AUTHOR]
ISSN:02728842
DOI:10.1016/j.ceramint.2026.03.135