X-ray spectroscopic investigation of metamictization and annealing in crystalline phosphates, silicates and complex Ti-Nb-Ta oxides. Final report

Metamict minerals have been damaged by the radioactive decay of their U and Th components and have been exposed to geologic processes over periods of many hundreds of millions of years. These metamict minerals can be considered to be the products of a natural long-term radiation damage experiment, hence there will be increased interest in the long term stability of these minerals because of their crystal-chemical similarities with phases in proposed waste-forms. A study was initiated of the effects of metamictization and annealing on crystalline phosphates, silicates and complex A/sub x/B/sub y/O/sub z/-type Ti-Nb-Ta oxides. This study included a detailed examination of the near neighbor site geometries of metal atoms in metamict minerals [e.g., A (Ca) and B (Ti) site cations] as determined by extended x-ray absorption fine structure (EXAFS) and x-ray absorption near edge structure (XANES) spectroscopy