Glass formation from iron-rich phosphate melts

Iron-rich phosphate glasses with nominal Fe/P ratios between 1.0 and 1.6 were prepared by a roller-quenching technique. The critical cooling rates (CCR) for glass formation were estimated by differential thermal analysis and found to be in the range of 103–104 °C/s for the iron-rich melts, compared to 1–10 °C/s for conventional iron phosphate melts with nominal Fe/P ratios near 0.50. The Fe(II)/Fetotal fraction in the quenched glasses increases with melt time and temperature, and ranges between 0.30 and 0.55 for the glasses studied. Raman spectroscopy indicates that the structures of the iron-rich phosphate glasses are based on isolated orthophosphate tetrahedra, similar to what are found in α-FePO4.