CRYSTALLIZATION CHARACTERISTICS OF IRON-CONTAINING SPODUMENE DIOPSIDE GLASSES

The crystallization characteristics of glasses based on a stoichiometric spodumene (LiAlSi2O6)-diopside (CaMgSi2O6) composition with addition of Fe2O3 replacing Al2O3 are described. The effects of compositional variation due to the Al2O3/Fe2O3 replacement and thermal treatment on the nature, type and stability fields of crystallizing phases as well as the resulting microstructure are traced by DTA, X-ray diffraction (XRD) and scanning electron microscopy (SEM). In most cases, intense uniform bulk crystallization with fine-grained microstructure were achieved on increase of iron oxide at the expense of alumina. The crystallizing phases, beta-eucryptite solid solution (ss), beta-spodumene ss, varieties of pyroxene solid solution of diopside, hedenbergite and augite nature are mostly formed together, in some cases, with alpha-quartz, lithium silicates, lithium ferrate (LiFeO2) and iron oxide. The type, stability and compatibility of the crystallized phases are discussed in relation to the compositional variation of the glass and thermal treatment.