Laboratory based X-ray absorption spectroscopy of iron phosphate glasses for radioactive waste immobilisation: a preliminary investigation.

We report the application of laboratory based X-ray absorption spectroscopy to the speciation of Fe in iron phosphate glasses prepared by conventional and microwave melting. Analysis of the weak pre-edge features in Fe K-edge XANES data demonstrated glasses produced by microwave melting to have a higher fraction of reduced Fe2+ species, since microwave melts do not have sufficient time to equilibrate with the prevailing oxygen partial pressure, compared to counterparts produced by conventional melting. Furthermore, our laboratory XANES data are consistent with the formation of octahedral Fe2+ at the expense of tetrahedral Fe3+ species, with increasing Fe2+ content. These findings are consistent with the previous findings of our 57Fe Mossbauer study, synchrotron XANES data, and current understanding of the structure of iron phosphate glasses, and demonstrate the utility of laboratory based XANES for routine speciation of Fe in these and other materials.