Zhang Xu, Bo Tao, Huang Zhi-Wei, Zhou Zhi-Heng, Hu Kong-Qiu, Shi Wei-Qun, Mei Lei
College of Nuclear Science and Technology, Harbin Engineering University, Harbin 150001, China.
Laboratory of Nuclear Energy Chemistry, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China.
Inorg Chem. 2024 Mar 18;63(11):5281-5293. doi: 10.1021/acs.inorgchem.4c00497. Epub 2024 Mar 2.
The attributes of good solubility and the redox-neutral nature of molten salt fluxes enable them to be useful for the synthesis of novel crystalline actinide compounds. In this work, a flux growth method under an inert atmosphere is proposed to explore the valence diversity of uranium, and a series of five uranium silicate structures, [KCl][(UO)(SiO)] (), Cs[(UO)(SiO)] (), K[U(SiO)] (), K[(UO)(UO)(SiO)] (), and Cs[U(UO)(SiO)] (), were synthesized using different metal halide salt and feeding U/Si ratios. Crystal structure analysis reveals that the utilization of argon atmosphere that helps to avoid possible oxidation of low-valence uranium generates a variety of oxidation states of uranium including U(VI), U(V), U(IV), mixed-valence U(V) and U(VI), and mixed-valence U(IV) and U(V). Characterization of physicochemical properties of representative compounds shows that all these uranium silicate compounds have bandgaps among the range of 2.0-3.4 eV, and mixed-valence uranium silicate compounds have relatively narrower bandgaps. Density functional theory calculations on formation enthalpies, lattice energies, and bandgaps of all five compounds were also performed to provide more structural information about these uranium silicates. This work enriches the library of variable-valence uranium silicate compounds and provides a feasible way to produce novel actinide compounds with intriguing properties through the flux growth method that might show potential application in relevant fields such as storage media for nuclear waste.
熔盐助熔剂良好的溶解性和氧化还原中性的特性使其可用于新型晶态锕系化合物的合成。在本工作中，提出了一种在惰性气氛下的助熔剂生长方法来探索铀的价态多样性，并使用不同的金属卤化物盐和进料U/Si比合成了一系列五种铀硅酸盐结构，即[KCl][(UO)(SiO)] ()、Cs[(UO)(SiO)] ()、K[U(SiO)] ()、K[(UO)(UO)(SiO)] ()和Cs[U(UO)(SiO)] ()。晶体结构分析表明，使用有助于避免低价铀可能被氧化的氩气气氛会产生多种氧化态的铀，包括U(VI)、U(V)、U(IV)、混合价态的U(V)和U(VI)以及混合价态的U(IV)和U(V)。代表性化合物的物理化学性质表征表明，所有这些铀硅酸盐化合物的带隙在2.0 - 3.4 eV范围内，且混合价态的铀硅酸盐化合物具有相对较窄的带隙。还对所有五种化合物的生成焓、晶格能和带隙进行了密度泛函理论计算，以提供有关这些铀硅酸盐的更多结构信息。这项工作丰富了可变价铀硅酸盐化合物库，并提供了一种可行的方法，通过助熔剂生长法制备具有有趣性质的新型锕系化合物，这可能在核废料存储介质等相关领域显示出潜在应用。
