Targeted crystal growth of uranium gallophosphates via the systematic exploration of the UF4–GaPO4–ACl (A = Cs, Rb) phase space.

The molten flux synthesis of a uranium gallophosphate and a uranium gallate, Cs4[UO2Ga2(PO4)4] (1) and Cs2UO2Ga2O5 (2), and four uranium phosphates, [Rb2Rb3.93Cl0.93][(UO2)5(PO4)5] (3), Rb11[(UO2)8(PO4)9] (4), Rb7.6[(UO2)8O8.6F0.4(PO4)2] (5), and Rb6[(UO2)5O2(PO4)4] (6), is reported. A systematic exploration of the UF4–GaPO4–ACl (A = Cs, Rb) phase space resulted in the synthesis of targeted Cs4[UO2Ga2(PO4)4] (1) and Cs2UO2Ga2O5 (2), which are gallium analogs of the previously reported aluminates, Cs4[UO2Al2(PO4)4] and Cs2UO2Al2O5. The exploration of this phase space simultaneously led to the synthesis and characterization of four new uranium phosphate phases: [Rb2Rb3.93Cl0.93][(UO2)5(PO4)5] (3), a salt inclusion material, and Rb11[(UO2)8(PO4)9] (4), both of which have complex 3D, porous, framework structures, and Rb7.6[(UO2)8O8.6F0.4(PO4)2] (5) and Rb6[(UO2)5O2(PO4)4] (6), both of which are layered structures related to the U3O8 topology. Fluorescence spectroscopy data are reported for all the compositions and are found to be typical for uranyl compounds. [ABSTRACT FROM AUTHOR]