Structural and valence state of iron ions in sodium-aluminum-phosphate glass

The purpose of this paper is to study the structural and valence state of iron ions in sodium-aluminum-phosphate glass for the application of liquid radioactive waste solidification. Electron paramagnetic resonance, Moessbauer spectroscopy, and nuclear magnetic resonances were used to conduct the study. Results were used to determine the characteristics of the occupancy and distribution of iron ions over tetra- and octahedral positions as a function of the ratio of the concentration of iron and aluminum oxides, to determine the concentration of Fe{sup 3}{sup +} and Fe{sup 2}{sup +} ions and the number of phosphorus and aluminum atoms in the nearest neighbor environment of the impurity iron ions, and estimate the effect of the concentration of aluminum oxide on the average distance between the phosphorus atoms in the glass. Results indicate that it must be assumed that tetrahedral glass-forming positions of ions are more stable than octahedral positions. Therefore, the long-term fixation of iron ions in sodium-aluminum-phosphate glasses will be more reliable with lower iron-aluminum ratios. These results will apparently extend to radioactive ions due to similar valence properties. 8 refs., 4 figs., 3 tabs.