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@ARTICLE{Li:852543,
author = {Li, Haijian and Langer, Eike and Kegler, Philip and Modolo,
Giuseppe and Alekseev, Evgeny},
title = {{F}ormation of {O}pen {F}ramework {U}ranium {G}ermanates:
{T}he {I}nfluence of {M}ixed {M}olten {F}lux and {C}harge
{D}ensity {D}ependence in {U}-{S}ilicate and {U}-{G}ermanate
{F}amilies},
journal = {Inorganic chemistry},
volume = {57},
number = {17},
issn = {1520-510X},
address = {Washington, DC},
publisher = {American Chemical Society},
reportid = {FZJ-2018-05463},
pages = {11201 - 11216},
year = {2018},
abstract = {Seven novel open-framework uranyl germanates, K2(UO2)GeO4,
K6(UO2)3Ge8O22, α-Cs2(UO2)Ge2O6, β-Cs2(UO2)Ge2O6,
Cs2(UO2)GeO4, and A(UO2)3(Ge2O7)2 (A = [NaK6Cl]6+,
[Na2Cs6Cl2]6+), were grown from different mixed molten
fluxes. The three-dimensional (3D) structure of K2(UO2)GeO4
with 8-ring channels can be built upon [UGe4] pentamer
secondary building units (SBUs). The 3D framework of
K6(UO2)3Ge8O22 with trapezoid (Ge8O22)12– clusters
consists of two types of [UGe4] pentamers. The 3D framework
of α-Cs2(UO2)Ge2O6 with 10-ring channels, crystallizing in
the P21/n space group, is constructed by [UGe4] pentamers.
The structure of β-Cs2(UO2)Ge2O6 contains achter (eight)
single germanate chains and is composed of [UGe6] heptamers
and [UGe4] pentamers. The structure of Cs2(UO2)GeO4 with
hexagonal 10-ring channels is composed of [U3Ge4] heptamers
and twisting five-fold GeO4 tetrahedra in four-membered
Ge4O12 rings occur. 3D frameworks of NaK6Cl(UO2)3(Ge2O7)2
(space group Pnnm) and Na2Cs6Cl2(UO2)3(Ge2O7)2 (P21/c) can
be constructed from the same SBUs [UGe4] pentamers. Thermal
stability of salt-inclusions was studied by TG and PXRD
analysis. Analysis of charge density for the U–Si–O
system indicates that the polymerization of silicate units
reduces the cross-links of the 3D frameworks. The concept of
SBUs combined with the cutting and gluing strategy was
applied to understand and analyze the distinct 8-, 10-, 12-,
and 14- membered channels for the uranyl germanate family.
The charge density of all known 3D U–Si/Ge–O frameworks
has been investigated, which shows strong correlations with
chemical composition of corresponding phases. The increase
of Si/O (Ge/O) ratios in silicate units results in the
decrease of negative charge density. Moreover, the charge
density increases with decreasing countercation size within
the same Si/O ratio. The correlations can be used to predict
inclusion phase formation within U–Si/Ge–O families.
Raman spectra of the studied uranyl germanates were
measured, and bands were assigned on the basis of structural
features.},
cin = {IEK-6},
ddc = {540},
cid = {I:(DE-Juel1)IEK-6-20101013},
pnm = {161 - Nuclear Waste Management (POF3-161) / Helmholtz Young
Investigators Group: Energy (HGF-YIG-Energy)},
pid = {G:(DE-HGF)POF3-161 / G:(DE-HGF)HGF-YIG-Energy},
typ = {PUB:(DE-HGF)16},
pubmed = {pmid:30125085},
UT = {WOS:000443923700076},
doi = {10.1021/acs.inorgchem.8b01781},
url = {https://juser.fz-juelich.de/record/852543},
}