ic8b01072_si_001.pdf (2.21 MB)
Comparison of Uranium(VI) and Thorium(IV) Silicates Synthesized via Mixed Fluxes Techniques
journal contribution
posted on 2018-05-16, 13:59 authored by Haijian Li, Philip Kegler, Vladislav V. Klepov, Martina Klinkenberg, Dirk Bosbach, Evgeny V. AlekseevTwo 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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K 2 ThSi 2 O 7BO3 D frameworkK 2 ThSi 3 O 9UO 2Noncentrosymmetric K 2 ThSi 3 O 9 crystallizesk 2 ThSi 2 O 7 crystallizessilicate chainsThO 6 octahedrathorium silicatesNa 2 Si VI Si 2 O 7 structure typemineral wadeite-type structureSBU3 Si 10 O 30 crystallizesK 23 Si 10 O 30diorthosilicate Si 2 O 7 groupP 6 3 space grouptriorthosilicate Si 3 O 9 ringsMixed Fluxes Techniques
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