  Lanthanides are often used as surrogates to study the properties of actinide
compounds. Their behaviour is considered to be quite similar as they both
possess f valence electrons and are close in size and chemical properties. This
study examines the potential of using two lanthanides (neodymium and cerium) as
surrogates for plutonium during the thermal decomposition of isomorphic oxalate
compounds, in the trivalent oxidation state, into oxides. Thus, the thermal
decomposition of neodymium, cerium and plutonium (III) oxalates are
investigated by several coupled thermal analyses (TG-DTA/DSC-MS/FT-IR) and
complementary characterisation techniques (XRD, UV-vis, FT-IR, SEM, carbon
analyser) under both oxidizing and inert atmosphere. The thermal decomposition
mechanisms determined in this study confirmed some previous results reported in
the literature, among diverging propositions, while also elucidating some
original mechanisms not previously considered. Calculated thermodynamic and
kinetic parameters for the studied systems under both atmospheres are reported
and compared with available literature data. Similarities and differences
between the thermal behaviour of plutonium(III) and lanthanide(III) oxalates
are outlined.
