AVS 45th International Symposium
    Applied Surface Science Division Monday Sessions
       Session AS-MoA

Paper AS-MoA1
Aqueous Leachability of Single Crystal and Polycrystalline Calcium Titanate

Monday, November 2, 1998, 2:00 pm, Room 307

Session: Oxides and Insulators - Surface Characterization and Applications
Presenter: Z. Zhang, Australian Nuclear Sci. and Tech. Organisation
Authors: Z. Zhang, Australian Nuclear Sci. and Tech. Organisation
E.R. Vance, Australian Nuclear Sci. and Tech. Organisation
Correspondent: Click to Email
Calcium titanate (CaTiO@sub 3@) constitutes about 20% of Synroc-C, a titanate-based ceramic designed for the immobilization of high level nuclear waste from Purex-type reprocessing. The chemical durability of calcium titanate in an aqueous environment is, therefore, an important issue. We have investigated the aqueous leachability of both single crystal and polycrystalline CaTiO@sub 3@ primarily using X-ray Photoelectron Spectroscopy (XPS). Static leaching tests were conducted in doubly deionized water at room temperature (RT), 90°C and 150°C for various periods of time. A reduction in the surface concentration of Ca (with respect to Ti) was observed after all leaching tests. The calcium leach rate of single crystal CaTiO@sub 3@ is found to be slightly lower than that of polycrystalline CaTiO@sub 3@ at all leaching temperatures. For both single crystal and polycrystalline samples, the calcium leach rate increases with increasing leaching temperature: the leach rate at 90°C is slightly higher than that at RT, while the leach rate at 150°C is substantially higher than that at 90°C. The effect of surface cation impurities, resulting from thermally induced segregation from the bulk, on the leaching behavior will be discussed. Other techniques employed in the study include Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) of CaTiO@sub 3@ surfaces before and after leaching tests, and Inductively Coupled Plasma Mass Spectrometry (ICP-MS) and Atomic Emission Spectroscopy (ICP-AES) of the leaching solutions. These results will also be shown.