Abstract
Lead iron–phosphate glasses were investigated for use as wasteform because of their improved chemical durability. There is a controversy if lead should or should not be used in iron phosphate glasses, and on the role of Fe in the inhibition of corrosion. The structure of the 43.3PbO·13.7Fe 2O 3·43P 2O 5 (mol%) glass, which has a dissolution rate in aqueous solution at 90 °C of 1.26×10 −9 g/cm −2 min −1, and the same O/P ratio, 3.5, as the lead-free 40Fe 2O 3·60P 2O 5 glass, was investigated. Glass samples were produced by melting batches of Fe 2O 3, PbO, and NH 4H 2PO 4 at 1100 °C for 1 h, and pouring the liquid into steel mold. Samples were annealed at 450 °C for 3 h. Some samples were crystallized by heating at 700 °C for 24 h. X-ray diffraction, Mössbauer, EPR, infrared, and Raman scattering spectroscopy were performed and compared to spectra obtained after crystallization. The crystalline phase Fe 2Pb(P 2O 7) 2 was identified after crystallization. The hyperfine parameters from the Mössbauer spectrum indicates that Fe 2+ and Fe 3+ ions are in octahedral coordination, and some of the Fe 3+ ions in the starting batch are reduced to Fe 2+ ions after melting. The infrared and Raman scattering spectra are representative of a mixture of chain-terminating Q 1 species and chain-forming Q 2 species. No Raman bands related to PO vibrations and Q 0 species were observed. From the EPR measurements it is concluded that all Fe 3+ ions are not constrained to central positions of tetrahedral and octahedral sites of the glass formers.
Published Version
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