Microscale preparation and characterization of selected lanthanide and actinide phosphates

Selected lanthanide and actinide phosphates were prepared on the microscale from reaction of a lead pyrophosphate (Pb₂P₂O₇) flux medium or boron phosphate (BPO₄) reagent with corresponding lanthanide and actinide oxides. Characterization of these phosphates involved X-ray diffraction and both absorption and laser Raman spectrophotometric analyses. When heated in the Pb₂P₂O₇ flux, cerium dioxide (Ce0₂) was not reduced to form the corresponding orthophosphate, CePO₄. Higher oxides of praseodymium and terbium were reduced to the orthophosphate, however. Correlation of these experimental results with published reduction potentials of the M(IV)/M(III) couples of the lanthanides and actinides allowed a prediction to be made: only americium of the actinides uranium, neptunium, plutonium, and americium would form the orthophosphate by reaction of the corresponding actinide dioxide with Pb₂P₂O₇). The prediction was confirmed experimentally and the other actinide products were tentatively identified as actinide(IV) pyrophosphates, e.g., UP₂O₇. The significance of these results lies in the ultimate goal of this area of research: to prepare transamericium orthophosphates, especially EsPO₄, for characterization and for determination of the chemical and physical consequences of their radioactive decay.