The structural state of iron in multicomponent aluminum iron borosilicate glass depending on their composition and synthesis conditions

The oxidation states and coordination environment of iron ions in borosilicate glass used for the immobilization of iron-containing radioactive waste are studied by the methods of Mossbauer and Fourier transform IR spectroscopies. In homogeneous glass, containing no more than 50 wt % of waste oxides, iron is present in the form of Fe3+ and Fe2+ ions in octahedral coordination with oxygen. The phase of a iron-containing spinel, in which iron atoms with an oxidation number of +3 in the magnetically ordered state surrounded tetrahedrally by oxygen atoms (Fe3+O4) and iron in the two- and trivalent states in the octahedral oxygen environment (Fe3+O6 + Fe2+O6) are present, is precipitated at higher waste concentrations. Both the Mossbauer and IR spectra of glass crystalline materials are combinations of the corresponding individual spectra. The quantitative ratio of the doubly- and triply-charged iron ions in samples depends on the synthesis conditions. The maximum fraction of iron in the glass phase (about 28%) and, at the same time, the maximum fraction of the Fe3+ ions (91.3%) are observed in the sample prepared in a crucible by heating in a laboratory furnace in the air environment and subsequent quenching on a metal sheet.