K8(K5F)U6Si8O40: An Intergrowth Uranyl Silicate

Morrison, Gregory; Tran, T. Thao; Halasyamani, P. Shiv; Loye, Hans‐Conrad zur

doi:10.1021/acs.inorgchem.6b00242

Cited by 22 publications

(28 citation statements)

References 33 publications

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“…11 Interestingly, in the case of uranyl saltinclusion compounds, these phases exhibit intense lumines-cence at room temperature, whereas in uranyl oxides the luminescence is typically thermally quenched. 20,21 Similar behavior has been observed for uranyl oxychlorides 22,23 and is likely due to the softening of the vibrational modes by the halide anion. Besides luminescence, many salt-inclusion phases are noncentrosymmetric, making them potential second harmonic generation materials.…”

Section: ■ Introductionsupporting

confidence: 69%

Understanding the Formation of Salt-Inclusion Phases: An Enhanced Flux Growth Method for the Targeted Synthesis of Salt-Inclusion Cesium Halide Uranyl Silicates

2016

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Salt-inclusion compounds (SICs) are known for their structural diversity and their potential applications, including luminescence and radioactive waste storage forms. Currently, the majority of salt-inclusion phases are grown serendipitously and the targeted growth of SICs has met with only moderate success. We report an enhanced flux growth method for the targeted growth of SICs. Specifically, the use of (1) metal halide reagents and (2) reactions with small surface area to volume ratios are found to favor the growth of salt-inclusion compounds over pure oxides and thus enable a more targeted synthetic route for their preparation. The Cs-X-U-Si-O (X = F, Cl) pentanary phase space is used as a model system to demonstrate the generality of this enhanced flux method approach. Single crystals of four new salt-inclusion uranyl silicates, [Cs3F][(UO2)(Si4O10)], [Cs2Cs5F][(UO2)2(Si6O17)], [Cs9Cs6Cl][(UO2)7(Si6O17)2(Si4O12)], and [Cs2Cs5F][(UO2)3(Si2O7)2], were grown using this enhanced flux growth method. A detailed discussion of the factors that favor salt-inclusion phases during synthesis and why specifically uranyl silicates make excellent frameworks for salt-inclusion phases is given.

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Section: ■ Introductionsupporting

confidence: 69%

Understanding the Formation of Salt-Inclusion Phases: An Enhanced Flux Growth Method for the Targeted Synthesis of Salt-Inclusion Cesium Halide Uranyl Silicates

2016

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“…The zur Loye group has focused on synthesizing novel uranium-containing SIMs via alkali halide fluxes and while the majority of these have been prepared from ACl-AF eutectics, some success was achieved with the use of ABI fluxes. A novel intergrowth uranyl silicate, K 8 (K 5 F)U 6 Si 8 O 40 , was grown from a KF-KBr flux (Morrison et al, 2016b ), and unlike many other uranyl compounds, K 8 (K 5 F)U 6 Si 8 O 40 was found to exhibit intense luminescence behavior possibly attributable to the salt-inclusion. Similarly, a KF-KBr flux was used to prepare [KK 6 Br 0.6 F 0.4 ][(UO 2 ) 3 (Ge 2 O 7 ) 2 ] (Juillerat et al, 2018 ) in a study to explore the adaptability of the uranyl germanate SIM framework.…”

Section: Salt-inclusion Materialsmentioning

confidence: 99%

“Soft” Alkali Bromide and Iodide Fluxes for Crystal Growth

et al. 2020

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In this review we discuss general trends in the use of alkali bromide and iodide (ABI) fluxes for exploratory crystal growth. The ABI fluxes are ionic solution fluxes at moderate to high temperatures, 207 to ∼1,300 • C, which offer a good degree of flexibility in the selection of the temperature profile and solubility. Although their main use is to dissolve and recrystallize "soft" species such as chalcogenides, many compositions with "hard" anions, including oxides and nitrides, have been obtained from the ABI fluxes, highlighting their unique versatility. ABI fluxes can serve to provide a reaction and crystallization medium for different types of starting materials, mostly the elemental and binary compounds. As the use of alkali halide fluxes creates an excess of the alkali cations, these fluxes are often reactive, incorporating one of its components to the final compositions, although some examples of non-reactive ABI fluxes are known.

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“…An increase of the U:Si ratio is also related to a change of linkage mode between U and Si polyhedra, from edge-to corner-sharing. The high U:Si is characteristic for the synthetic compounds [23][24][25][26][27][28][29], which will not be mentioned in the following text. The approach concerning secondary-building units (SBUs)is a useful tool for highlighting differences in mineral groups mentioned above.…”

Section: Mineralogy and Crystallography Of Natural Uranyl Silicatesmentioning

confidence: 99%

“…Infrared and Raman spectroscopy data for natural uranyl silicates have been reported by [21] and also recently by a thorough review of Raman spectroscopy of uranyl minerals and phases [22]. With increased attention many synthetic uranyl silicate compounds have been synthesized, usually with crystal chemistry divergent from the natural ones [23][24][25][26][27][28][29], and also both experimental [30][31][32] and theoretical studies [33,34] have been undertaken in order to determine the thermodynamic properties of uranyl silicate minerals.…”

Section: Introductionmentioning

confidence: 99%

Mineralogy, Crystallography and Structural Complexity of Natural Uranyl Silicates

Plášil

2018

Minerals

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Naturally occurring uranyl silicates are common constituents of the oxidized parts (i.e., supergene zone) of various types of uranium deposits. Their abundance reflects the widespread distribution of Si4+ in the Earth’s crust and, therefore, in groundwaters. Up to date, 16 uranyl silicate minerals are known. Noteworthy is that the natural uranyl silicates are not extremely diverse regarding their crystal structures; it is a result of possible concentrations (activity) of Si4+ in aqueous solutions derived from dissolution of primary Si minerals or the composition of late hydrothermal fluids. Therefore, in natural systems, we distinguish in fact among two groups of uranyl silicate minerals: uranophane and weeksite-group. They differ in U:Si ratio (uranophane, 1:1; weeksite, 2:5) and they form under different conditions, reflected in distinctive mineral associations. An overview of crystal-chemistry is provided in this paper, along with the new structure data for few members of the uranophane group. Calculations of the structural complexity parameters for natural uranyl silicates are commented about as well as other groups of uranyl minerals; these calculations are also presented from the point of view of the mineral paragenesis and associations.

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K₈(K₅F)U₆Si₈O₄₀: An Intergrowth Uranyl Silicate

Cited by 22 publications

References 33 publications

Understanding the Formation of Salt-Inclusion Phases: An Enhanced Flux Growth Method for the Targeted Synthesis of Salt-Inclusion Cesium Halide Uranyl Silicates

Understanding the Formation of Salt-Inclusion Phases: An Enhanced Flux Growth Method for the Targeted Synthesis of Salt-Inclusion Cesium Halide Uranyl Silicates

“Soft” Alkali Bromide and Iodide Fluxes for Crystal Growth

Mineralogy, Crystallography and Structural Complexity of Natural Uranyl Silicates

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