A Novel Metastable Pentavalent Plutonium Solid Phase on the Pathway from Aqueous Plutonium(VI) to PuO2 Nanoparticles

Here we provide evidence that the formation of PuO2 nanoparticles from oxidized Pu-VI under alkaline conditions proceeds through the formation of an intermediate Pu-V solid phase, similar to NH4PuO2CO3, which is stable over a period of several months. For the first time, state-of-the-art experiments at Pu M-4 and at L-3 absorption edges combined with theoretical calculations unambiguously allow to determine the oxidation state and the local structure of this intermediate phase.