Speciation of sulphate ions in sodium alumino(iron)phosphate glasses

Speciation of sulphate ions in sodium alumino(iron)phosphate glasses was studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), infrared and Raman spectroscopy. The high-sulphate glasses are subject to devitrification segregating minor sodium sulphates. As followed from SEM data iron-bearing glasses were higher homogeneous than the iron-free glasses. Vibrational (IR and Raman) spectra demonstrated occurrence of some bands typical of vibrations of S-O bonds in the sulphate ions: 620-640 cm(-1) (v(4) SO4 in IR spectra) and similar to 460-470 (v(2)), similar to 620-640 (v(4)), 967-1008 (v(1)) and similar to 1105-1130 cm(-1) (v(3)) in the Raman spectra. This exhibits that the sulphate ions have been shown to maintain their identity being independent in the aluminophosphate glass network. Sulfur leach rate is associated with that for sodium due to formation of a sodium sulphate enriched areas in the glasses.