Aqueous Dissolution of Perovskite (CaTiO₃): Effects of Surface Damage and [Ca²⁺] in the Leachant

We have characterized thermally annealed perovskite (CaTiO₃) surfaces, both before and after aqueous dissolution testing, using scanning electron microscopy, cross-sectional transmission electron microscopy, x-ray photoelectron spectroscopy, and atomic force microscopy. It was shown that mechanical damage caused by polishing was essentially removed at the CaTiO₃ surface by subsequent annealing; such annealed samples were used to study the intrinsic dissolution behavior of perovskite in deionized water at RT, 90 °C, and 150 °C. Our results indicate that, although mechanical damage caused higher Ca release initially, it did not affect the long-term Ca dissolution rate. However, the removal of surface damage by annealing did lead to the subsequent spatial ordering of the alteration product, which was identified as anatase (TiO₂) by both x-ray and electron diffraction, on CaTiO₃ surfaces after dissolution testing at150 °C. The effect of Ca²⁺ in the leachant on the dissolution reaction of perovskite at 150 °C was also investigated, and the results suggest that under repository conditions, the release of Ca from perovskite is likely to be significantly slower if Ca²⁺ is present in ground water.