Observation of the Same New Sheet Topology in Both the Layered Uranyl Oxide-Phosphate Cs11[(UO2)12(PO4)3O13] and the Layered Uranyl Oxyfluoride-Phosphate Rb11[(UO2)12(PO4)3O12F2] Prepared by Flux Crystal Growth

Abstract

Single crystals of four new layered uranyl phosphates, including three oxyfluoride-phosphates, were synthesized by molten flux methods using alkali chloride melts, and their structures were determined by single-crystal X-ray diffraction. Cs 11 [(UO 2 ) 12 (PO 4 ) 3 O 13 ] ( 1 ) and Rb 11 [UO 2 ) 12 (PO 4 ) 3 O 12 F 2 ] ( 2 ) contain uranyl phosphate layers exhibiting a new sheet topology that can be related to that of β-U 3 O 8 , while Cs 4.4 K 0.6 [(UO 2 ) 6 O 4 F(PO 4 ) 4 (UO 2 )] ( 3 ) and Rb 4.4 K 0.6 [(UO 2 ) 6 O 4 F(PO 4 ) 4 (UO 2 )] ( 4 ) contain layers of a known isomer of the prominent phosphuranylite topology. The location of the fluorine in structures 2 - 4 is discussed using bond valence sums. First principles calculations were used to explore why a pure oxide structure is obtained for the Cs containing phase ( 1 ) and in contrast an oxyfluoride phase for the Rb containing phase ( 2 ). Ion exchange experiments were performed on 1 and 2 and demonstrate the ability of these structures to exchange approximately half of the parent alkali cation with a target alkali cation in an aqueous concentrated salt solution. Optical measurements were performed on 1 and 2 and the UV-vis and fluorescence spectra show features characteristic of the uranyl group.

Structure and stability of alkali gallates structurally reminiscent of hollandite

“…Recent publications by our group have detailed that reaction vessel size, in addition to the vessel material, significantly influences the products that are obtained in a reaction 22‐24 . While the reaction vessel material has always been regarded as important in the solid‐state community, as elements from the reaction vessel have been known to incorporate into the final product under certain reaction conditions, reaction vessel size is not always reported especially for alumina and metal crucibles, as vessel shape is not typically assumed to affect product formation.…”

“…Recent publications by our group have detailed that reaction vessel size, in addition to the vessel material, significantly influences the products that are obtained in a reaction. [22][23][24] While the reaction vessel material has always been regarded as important in the solid-state community, as elements from the reaction vessel have been known to incorporate into the final product under certain reaction conditions, reaction vessel size is not always reported especially for alumina and metal crucibles, as vessel shape is not typically assumed to affect product formation. Traditional solid-state reactions were attempted by pressing pellets of stochiometric amounts of Ga 2 O 3 and CsNO 3 (in 10% excess) and heating at temperatures of 600, 700, 800, 900, 1000, and 1200°C in order to obtain CsGa 7 O 11 ; however, in all cases, Ga 2 O 3 persists and does not react to produce the desired product.…”

Expanding the Chemistry of Salt-Inclusion Materials: Utilizing the Titanyl Ion as a Structure Directing Agent for the Targeted Synthesis of Salt-Inclusion Titanium Silicates

“…To achieve charge balance, this site must be 75% oxygen and 25% fluorine. The formation of oxyfluorides with mixed O/F sites is common in alkali fluoride containing melts. ,,, …”

Flux Growth of Uranyl Titanates: Rare Examples of TiO4 Tetrahedra and TiO5 Square Bipyramids

“…For much of their history, the focus was on the investigation of uranyl minerals and the exploration of new materials through ceramic and hydrothermal syntheses, the latter of which resembles the conditions under which most minerals form. In the past decade, the flux growth of uranyl compounds, especially using halide fluxes, has become quite prolific, resulting in many new uranyl silicates, − germanates, − phosphates, − borates, − aluminates, and others. ,, …”