The aim of this project was to investigate, both experimentally and theoretically, the perovskite mineral calcium titanate CaTiO3β and to gain a greater insight into its properties. Primarily, the properties studied were the defect chemistry of the material and the effect of doping on the structure, with particular attention being given to strontium and yttrium incorporation. This focus was chosen due to the potential applications of calcium titanate in radioactive waste immobilisation, primarily as one of the constituent phases in SYNROC.1 Experimentally, the effect on the structure of significant levels of strontium impurity was studied, with attention being given to phase changes and possible implications for the maximum level of doping in the structure. To compliment this, a theoretical investigation was undertaken into how defects within the CaTiO3β structure manifest themselves, how charge imbalances may be accounted for and the implications this has for radioactive waste immobilisation. Initially, substitutional defects were examined, followed by defect clustering and how multiple defects may interact with each other in the system. Strontium doping is of major concern in the CaTiO3β structure due to the use of the mineral in radioactive waste immobilisation, and consequently the effect of yttrium and zirconium doping is also of relative importance due to their formation in the 90Sr decay chain.
1 A. Ringwood, S. Kesson, N. Ware, W. Hibberson and A. Major, Nature, 1979, 278, 219-223
