Diffusion in Doped and Undoped Amorphous Zirconia

Dopants such as Fe, Cr, and Ni, are added to Zr-based alloys to improve properties when used as nuclear fuel cladding. Due to the presence of coolant water, a zirconium oxide passivation layer forms to initially protect against corrosion. Experimental work found in literature reports that Ni and Fe are observed to segregate towards grain boundaries in the ZrO₂ layer formed on Zr-based alloys. Segregation of dopants to the grain boundaries may change the morphology along the boundary, possibly inducing amorphous regions which may act as high diffusion pathways for corrosion species, such as oxygen and hydrogen. This work uses classical molecular dynamics to analyse diffusion in undoped and trivalent lanthanide doped, crystalline and amorphous, ZrO₂at a range of concentrations and temperatures. Comparisons have been made between the crystalline and amorphous counterparts, to deduce whether amorphous grain boundary regions may be acting as high diffusion pathways for corrosion species, contributing towards the overall corrosion of the material.