Comparison of Uranium(VI) and Thorium(IV) Silicates Synthesized via Mixed Fluxes Techniques

Li, Haijian; Alekseev, Evgeny; Kegler, Philip; Bosbach, Dirk; Klinkenberg, Martina; Klepov, Vladislav V.

doi:10.1021/acs.inorgchem.8b01072

Journal Article

FZJ-2018-03052

Comparison of Uranium(VI) and Thorium(IV) Silicates Synthesized via Mixed Fluxes Techniques

Li, H.FZJ* ; Kegler, P.FZJ* ; Klepov, V. V. ; Klinkenberg, M.FZJ* ; Bosbach, D.FZJ* ; Alekseev, E. (Corresponding author)FZJ*

2018
American Chemical Society Washington, DC

Inorganic chemistry 57(11), 6734-6745 (2018) [10.1021/acs.inorgchem.8b01072]

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Please use a persistent id in citations: doi:10.1021/acs.inorgchem.8b01072

Abstract: Two uranium and two thorium silicates were obtained using high temperature mixed fluxes methods. K14(UO2)3Si10O30 crystallizes in the P21/c space group and contains open-branched sechser (six) single silicate chains, whereas K2(UO2)Si2O6 crystallizes in the C2/c space group and is built of unbranched achter (eight) silicate chains. The crystals of K14(UO2)3Si10O30 and K2(UO2)Si2O6 are related by increasing U/Si molar ratios, and both structures contain the same secondary building units (SBUs), [USi6] heptamers. The triangle diagram for all known A+–UO22+–SiO44– phases demonstrates the high polymerization level of silicate groups in the system, which was compared with the family of A+–UO22+–BO33–/BO45– compounds. For both thorium silicates, the transformation of K2ThSi2O7 to K2ThSi3O9 was found to be a factor of the reaction time. K2ThSi2O7 crystallizes in the C2/c space group and belongs to the Na2SiVISi2O7 structure type. Its 3D framework consists of diorthosilicate Si2O7 group and ThO6 octahedra. Noncentrosymmetric K2ThSi3O9 crystallizes in the hexagonal P63 space group and adopts mineral wadeite-type structure based upon triorthosilicate Si3O9 rings and ThO6 octahedra. The coordination environment of thorium for all existing oxo-anion compounds including B, Si/Ge, P/As, Cr/Mo/W, and S/Se/Te are summarized and analyzed. Additionally, spectroscopic properties of all novel materials have been studied.

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