In-situ Raman analysis of the evolution of U3O8 with temperature

U 3 O 8 was prepared and subjected to a heating treatment in air, with the aim of in-situ analysing by Raman spectroscopy its evolution with temperature. The experiment was conducted from room temperature up to 600 °C and Raman spectra were acquired every 25 °C in order to track any occurring changes. The marked change of spectral features observed along the 100–175 °C temperature range leads to the assumption that some sort of structure reordering might be starting to take place. In particular, the disappearance of the Raman band at ∼160 cm −1 around that temperature suggests that it relates to the transition to the higher-symmetry hexagonal structure. Moreover, XRD and Raman characterisation carried out at room temperature before and after the heating treatment revealed the same U 3 O 8 orthorhombic structure, implying that the deduced orthorhombic-hexagonal phase transition is dependent on temperature and reversible. • In-situ Raman analysis of U 3 O 8 up to 600 °C in air has been successfully conducted. • The orthorhombic-to-hexagonal transition of U 3 O 8 has been tracked by Raman. • Correlations between Raman bands and U 3 O 8 structure evolution have been established. • The detected phase transition is dependent on temperature and reversible.