The contribution of Y2O3 and/or FeO3 to the crystallisation characteristics and crystalline phase assemblages developed from thermally treated glasses based on Li2O-SiO2 system have been investigated by differential thermal analysis (DTA), x-ray diffraction analysis (XRD) and scanning electron microscopy (SEM). Lithium disilicate- Li2Si2O5, lithium metasilicate - Li2SiO3, two forms of yttrium silicate Y2Si2O7 and Y2SiO5, iron yttrium oxide-YFeO3, lithium iron silicate-LiFeSi2O6 and a-quartz phases were mostly developed in the glasses. Increasing the Y2O3 content in the studied glasses decreased their tendency to crystallise. However, the addition of Fe2O3 together with, or instead of Y2O3, led to increases in the rate of crystallisation of the glasses.
