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

Abstract

Crystallisation of a glass with the composition 16Na₂O·10CaO·49SiO₂·25Fe₂O₃ 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).