Oxygen and phosphorus coordination around iron in crystalline ferric ferrous pyrophosphate and iron-phosphate glasses with UO2 or Na2O

Fe K-edge x-ray absorption fine-structure (XAFS) measurements were performed on glass samples of (Fe3O4)(0.3)(P2O5)(0.7) With various amounts of Na2O or UO2, Near-edge and extended XAFS regions are studied and comparisons are made to several reference compounds. We find that iron in the base glass is similar to 25% divalent and that the Fe2+ coordination is predominantly octahedral, while Fe3+ sites are roughly split between tetrahedral and octahedral coordinations, Also, we measure roughly one Fe-O-P link per iron. Substitution of Na2O or UO2 up to 15 mol% primarily affects the first Fe-O shell. The results are compared to data from the related material Fe-3(P2O7)(2).