New insights on the thermal decomposition of lanthanide(III) and actinide(III) oxalates: from neodymium and cerium to plutonium

摘要

Lanthanides are often used as surrogates to study the properties of actinidecompounds. Their behaviour is considered to be quite similar as they bothpossess f valence electrons and are close in size and chemical properties. Thisstudy examines the potential of using two lanthanides (neodymium and cerium) assurrogates for plutonium during the thermal decomposition of isomorphic oxalatecompounds, in the trivalent oxidation state, into oxides. Thus, the thermaldecomposition of neodymium, cerium and plutonium (III) oxalates areinvestigated by several coupled thermal analyses (TG-DTA/DSC-MS/FT-IR) andcomplementary characterisation techniques (XRD, UV-vis, FT-IR, SEM, carbonanalyser) under both oxidizing and inert atmosphere. The thermal decompositionmechanisms determined in this study confirmed some previous results reported inthe literature, among diverging propositions, while also elucidating someoriginal mechanisms not previously considered. Calculated thermodynamic andkinetic parameters for the studied systems under both atmospheres are reportedand compared with available literature data. Similarities and differencesbetween the thermal behaviour of plutonium(III) and lanthanide(III) oxalatesare outlined.