Structural characteristics of sodium iron phosphate glasses.

Bushra AL Hasni* & Gavin Mountjoy, School of Physical Sciences, University of Kent

Iron phosphate glasses are promising for nuclear waste immobilization. Such glasses will include sodium since it is a component of the waste stream. We have carried out a detailed structural on sodium iron phosphate glasses xNa2O-40-xFe2O3-60P2O5 with x = 10, 20, 30 through Fe K-edge x-ray absorption spectroscopy (both near-edge, XANES, and extended, EXAFS), and the complementary x-ray and neutron diffraction techniques. P-O, Fe-O, Na-O and O-O first neighbour peaks are well resolved at 1.5, 1.98, 2.3 and 2.5 Å respectively. The glasses contained PO4 tetrahedra with the experimental mean value of the coordination number (CN) is equal to 3.8. The local environment around iron has been studied and the samples have shown the mean CN of iron is decreased from 5.8 to 5.3 as the Fe2O3 content increase and the bond length decrease slightly as expected. The NaOx polyhedra remain largely unaffected with an average CN=5. In addition, the Mössbauer spectra provide an evidence for the dominant of Fe3+ ions with a small amount of Fe2+ in these glasses. The isomer shift, quadruple splitting and have been measured and the results are comparable with those from diffraction studies.