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[(UO2(GaP2O8)2] (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[(UO2(GaP2O8)2] (1) and Cs2UO2Ga2O5 (2), which are gallium analogs to the previously reported aluminates, Cs4[(UO2(AlP2O8)2] and Cs2UO2Al2O5 (2). 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 is reported for all compositions and is found to be typical for uranyl compounds.