Crystallisation of iron containing glass-ceramics and the transformation of hematite to magnetite

Crystallisation of a glass with the composition 16Na(2)O center dot 10CaO center dot 49SiO(2)center dot 25Fe(2)O(3) led to the formation of hematite and magnetite crystals with various morphologies. Crystals containing both the hematite and the magnetite phases were detected and a strict orientation relationship between the phases is described. It is argued that hematite (Fe2O3) is the phase primarily crystallised and magnetite (Fe3O4) is the result of a phase transformation after the primary crystal growth. The main method of characterization was scanning electron microscopy (SEM) combined with electron backscatter diffraction (EBSD).