Journal
INORGANIC CHEMISTRY
Volume 59, Issue 14, Pages 9919-9926Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acs.inorgchem.0c01089
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Funding
- National Natural Science Foundation of the People's Republic of China [11505122, 11775152]
- Science and Technology Innovation Team of Sichuan Province [15CXTD0025]
- Department of Chemistry
- WSU-PNNL Nuclear Science and Technology Institute at Washington State University
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As efficient and stable nuclear waste forms, single- phase uranium (U6+)-incorporated La2Zr2O7 nanoparticles were designed and synthesized in an air atmosphere. To obtain a high U loading, divalent magnesium (Mg2+) was introduced to balance the extra charge from the substitution of tetravalent zirconium (Zr4+) by U6+ with a minimized impact to the lattice. There is a composition-driven phase transition from order pyrochlore to defect fluorite as the U concentration increases from 10 to 30 mol %, demonstrating both good solubility and stability of the La2Zr2O7 host for U and potentially for other actinides. La-2(UxMgxZr1-2x)(2)O-7 (x = 0-0.3) nanopartides showed good dispersity and crystallinity with an average particle size of similar to 48 nm. Furthermore, X-ray photoelectron spectroscopy, Raman spectroscopy, and emission spectroscopy revealed that U was stabilized in the hexavalent state in the form of a UO22+ ion. Spectroscopic methods also demonstrated that our samples caused a scintillating response with an orange emission (597 nm) by 230 nm excitation. In addition, density functional theory simulations were employed to investigate the atomic structures and electronic properties of the U-incorporated pyrochlores. The calculated bond lengths, atomic charges, and charge density confirm the existence of UO22+ ions. Supported by both experimental and computational results, a novel geometrical structure was proposed to explain the Mg2+-U(6+ )substitution. This work demonstrated the successful development of U-incorporated La2Zr2O7 nanoparticles and provided an efficient way to immobilize U in these ceramic waste matrixes.
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