Impact of iron oxide incorporation on the physicochemical properties of phosphate glasses

This study examined the influence of iron oxide incorporation on the durability of phosphate glasses with the following formula 50P2O5 –33·33K2O–(11·11−x/2)CaO–(5·56−x/2)MgO–xFe2O3 with 0≤x≤2 mol%. Indeed, the effects of adding iron on the glass structure, physicochemical properties, thermal properties, and especially, dissolution behaviours were investigated. The glasses were prepared using the classical melt quenching technique at 1000°C. The characterisation was performed using differential thermal analysis, x-ray diffraction, density measurements, Raman spectroscopy and Fourier transform infrared spectroscopy. Dissolution behaviours were followed by measuring weight loss and pH. The substitution of calcium and magnesium for iron increased the characteristic temperatures (Tg, Tc, Tf) and reduced the molar volume, showing a more compact phosphate glasses network. Structural characterisation showed that the glass network is composed mainly of metaphosphate chains. The dissolution behaviours of the processed glasses revealed that the introduction of Fe2O3 to the phosphate glasses can improve the chemical durability due to the ionic crosslinking between the nonbridging oxygen atoms of the phosphate chains, which explains the changes in their physicochemical properties.