Crystallisation of iron phosphate glasses

The crystallisation of xFe(2)O(3)(100-x)P2O5, (14 less than or equal to x less than or equal to 40) glasses has been investigated by differential thermal analysis, x-ray, diffraction analysis and Raman spectroscopy. The glasses were heat treated in dry argon from 298 to 1143 K. The crystallisation temperature and number of crystallised phases depended upon the glass composition, atmosphere and heat treatment temperature. With increasing Fe2O3 content the structure of phosphate glass changes from metaphosphate chain structures to the pyrophosphate and eventually, to orthophosphate structures. The relative amount of iron (II) and iron (III) present during the crystallisation process was found to have a significant effect on the resulting crystalline phases. The results suggest that the glass and its crystalline counterpart both have the same basic phosphate structure.