3 de maig de 2024
Errandonea, D., Turnbull, R., Sánchez-Martín, J., Oliva, R., Muñoz, A., Radescu, S., Mujica, A., Blackburn, L., Hyatt, N. C., Popescu, C., & Ibáñez-Insa, J. (2024). A comparative study of the high-pressure structural stability of zirconolite materials for nuclear waste immobilisation. Results in Physics, 61, 107704. https://doi.org/10.1016/j.rinp.2024.107704
Abstract
We present a comparative study of the high-pressure behaviours of the nuclear waste immobilisation materials zirconolite-2M, −4M, –3O, and −3T. The materials are studied under high-pressure conditions using synchrotron powder X-ray diffraction. For zirconolite-2M we also performed density-functional theory calculations. A new triclinic crystal structure (space group P 1¯), instead of the previously assigned monoclinic structure (space group C2/c) is proposed for zirconolite-2M. We named the triclinic structure as zirconolite-2TR. We also found that zirconolite-2TR undergoes a phase transition at 14.7 GPa to a monoclinic structure described by space group C2/c, which is different than the high-pressure structure previously proposed in the literature. These results are discussed in comparison with previous studies on zirconolite-2M and the related compound calzirtite. For the other three zirconolite structures (4M, 3O, and 3T) this is the first high-pressure study, and we find no evidence for pressure induced phase transitions in any of them. The linear compressibility of the studied compounds, as well as a room-temperature pressure–volume equation of state, are also presented and discussed.