Electron energy loss spectroscopy investigations through nano-ablated actinide dioxide samples

• Actinide dioxides lamella were produced by FIB.
• EEL spectra recorded for ThO2, and NpO2 as a function of the thickness.
• The O and P edges were recorded.
• ThO2 and NpO2 EEL spectra are compared with those of UO2.

Lamellas of actinide (Th, Np) dioxides (∼10 μm × ∼10 μm × ∼0.02–0.20 μm) were produced by focused ion beam for transmission electron microscopy and electron energy loss (EEL) spectroscopy examinations. These samples allow quantitative analysis of the EEL spectra recorded for ThO2, and NpO2 as a function of the thickness. The O and P edges were recorded over zero loss to 400 eV loss. ThO2 and NpO2 EEL spectra are compared with those reported earlier for UO2. The energy lost was studied through a range of thicknesses going from ∼20 to ∼200 nm. It was observed that the O and P edges are not thickness dependant as expected confirming the core loss nature of these edges. The edges allow reconstruction of the electronic transitions, the lowest energy loss edges for P transitions corresponds to P3 electron transitions (from 15 to 17 eV) from the 6p(2/3) level. Two next P1 and P2 edges are partially overlapping. The followed O edges are suggested to be a pre-peak and the O4,5 transitions. The edge analysis allows also better interpretation of the loss spectrum with identification of the plasmon peak of the core electron transition edges. The technique may be applied for identification of the actinide in fuels or waste forms.