Effect of Molybdenum on Structure of Iron Phosphate Glasses

Molybdenum is one of elements concentrated in power reactor high-level waste liquid. The dissolution of MoO₃ in iron phosphate glass and the influence of MoO₃ content on glass structure are the focus of researches on the iron phosphate glass formulation for immobilizing power reactor high-level waste liquid. To investigate the dissolution of MoO₃ in iron phosphate glass and the effect of MoO₃ content on the glass structure, a series of 60% P₂O₅–19%Fe₂O₃–8%Al₂O₃–13%Na₂O(in mole fraction, the same below) samples doped with MoO₃ at different ratios (i.e., 1%–8%) were prepared by a melting-quenching method. The phase and microscopic morphology were analyzed by X-ray diffraction (XRD) and electron probe microanalysis (EPMA). The structure of the samples was characterized by Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and Mössbauer spectroscopy. Molybdenum can be completely dissolved into the glass structure without forming the crystallite and phase separation when the actual content of MoO₃ is less than 6.38%. Molybdenum exists mainly in the form of [MoM₆] octahedral in the glass, and Mo—O—P bonds are observed with the MoO₃ content of more than 4%. The Q¹ and Q² units are the main structures in the glass phase, and the relative content of the Q¹ unit increases with MoO₃ doping content. The content of Fe³⁺ decreases slightly, while the valence state of Mo ions remains unchanged with the increase of MoO₃ doping content.