Phase stability of Ce, La and U oxides in the presence of hydrogen and water: Thermodynamic modeling and experimental insights
Year: 2025
Type: article
Abstract: Standard metal-oxygen or metal-hydrogen phase diagrams neglect the presence of water vapor. However, water vapor present in the environment often destabilizes the oxide or hydride phase, leading to the stabilization of hydroxide, oxy-hydroxide or hydrate phases. Appropriate phase diagrams are required to properly describe and predict the chemistry of a metal and its oxide or hydride in realistic conditions. In the present work, M-O-H phase stability diagrams were computed for uranium, lanthanum and cerium (U, La and Ce), based on previously compiled as well as newly assessed thermodynamic data, in CALPHAD (CALculations of PHAse Diagrams) formalism. We show how the ternary phase diagrams relate to diverse experimental observations on the behavior of these elements in environments containing hydrogen or water vapor. The phase diagrams allow the identification of common trends as well as differences between the systems studied. For example, all the elements form hydride phases but minor concentrations of oxygen or water are sufficient to destabilize the hydride. The oxide phases have a wide range of stability, but the oxide may react in the presence of water vapor to form a hydroxide (in the case of La) or hydrates (in the case of U). The range of stability of the hydroxide and hydrate phases increases as the temperature is lowered.
Authors: Danielle Schweke, Daniel Rabin, Eli Brosh
Institution: Shimon Peres Negev Nuclear Research Center
Language: English
Subfield: Materials Chemistry
Field: Materials Science
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $1,350
OpenAlex ID: W4411089795