Phase transformation of stabilised zirconia in water and 1.0 M LiOH

Abstract The phase transformation of stabilised zirconia was studied after exposure to water and lithiated (1 M LiOH) water for 3 days at 400°C, with the aim to evaluate a proposed reason for the enhanced Zircaloy corrosion observed in the presence of lithium hydroxide. Three different tetragonal zirconia samples were investigated, stabilised by addition of yttrium, cerium and by small crystallite size, respectively. One stabilised cubic zirconia sample, with addition of calcium, was also included in the investigation. The corrosion test was performed in mini autoclaves and the crystal structure of the material, before and after the autoclave test, was characterised with X-ray diffraction. For the three zirconia versions with tetragonal phase, a majority of the material transformed to monoclinic phase in both environments, i.e., the transformation rate was found to be independent of the presence of lithium hydroxide. The fraction transformed to monoclinic zirconia was about 63% for size-stabilised sample and 84–94% for the yttria- and cerium-stabilised zirconia, while the cubic zirconia was unaffected by the corrosion test. Based on our result no evidence of preferential dissolution of stabilised zirconia is found in LiOH solution, compared to test in pure water.