The synthesis and characterization of crystalline phosphates of thorium, uranium and neptunium

The high temperature synthesis and stability of phosphates of thorium, uranium and neptunium have been studied by Raman spectroscopy, X-ray diffraction and chemical analyses. For these actinides, the only orthophosphate An3(PO4)4 (An = actinide) that could be prepared was thorium orthophosphate. The high temperature (α, cubic) forms of all three metal pyrophosphates were synthesized. For the oxypyrophosphate compounds (AnO)2P2O7, only the thorium compound was not obtained, and (NpO)2P2O7 is reported here for the first time. The results of these studies are discussed and compared with published data on actinide phosphates. (Auth.)