X-ray photoelectron and Mössbauer spectroscopic studies of iron phosphate glasses containing U, Cs and Bi

Abstract

The atomic structure of iron phosphate glasses and those containing common high level nuclear waste components such as UO 2, Cs 2O and Bi 2O 3 has been investigated using X-ray photoelectron spectroscopy (XPS) and Mössbauer spectroscopy. Oxygen 1s spectra indicate that only 16–26% of the oxygen ions are bridging oxygens (BOs). The addition of waste components such as UO 2, Cs 2O and Bi 2O 3 does not change the BO/(BO + NBO) ratio appreciably. Some structural similarities in the short range order was found between the glass and crystalline Fe 3(P 2O 7) 2 which crystallizes from the glass upon heat treatment. The Mössbauer hyperfine parameters, isomer shift and quadrupole splitting, showed that the environment around iron ions was independent of the composition. In general, the addition of waste elements does not alter the basic features of the parent glass. The measured isomer shifts and quadrupole splittings indicate that the Fe 3+ and Fe 2+ ions in these glasses are in octahedral or distorted octahedral coordination. The fraction of Fe 2+ in the glass increases with the melting temperature. However, most physical properties of these glasses do not depend appreciably on the valence state of iron ions.