Plutonium and Americium Aluminate Perovskites.

Both AmAlO and PuAlO perovskites have been synthesized and characterized using powder X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared spectroscopy (FT-IR), and Al magic angle spinning nuclear magnetic resonance spectroscopy (MAS NMR). AmAlO perovskite showed a rhombohedral configuration (space group 3̅) in agreement with previous studies. The effect of americium α-decay on this material has been followed by XRD and Al MAS NMR analyses. In a first step, a progressive increase in the level of disorder in the crystalline phase was detected, associated with a significant crystallographic swelling of the material. In a second step, the crystalline AmAlO perovskite was progressively converted into amorphous AmAlO, with a total amorphization occurring after 8 months and 2 × 10 α-decays/g. For the first time, PuAlO perovskite was synthesized with an orthorhombic configuration (space group ), showing an interesting parallel to CeAlO and PrAlO lanthanide analogues. High-temperature XRD was performed and showed a → 3̅ phase transition occurring between 473 and 573 K. The thermal behavior of 3̅ PuAlO was followed from 573 to 1273 K, and extrapolation of the data suggests that cubic plutonium perovskite should become stable at around 1850 K (3̅ → 3̅ transition).