The crystallisation of glasses based on eutectic compositions in the system Li2O-Al2O3-SiO2

Structural transformations have been studied in glasses related in composition to the binary eutectic between lithium metasilicate and -spodumene. Crystallisation processes and changes in microstructure during the controlled heating of the glasses have been followed using X-ray diffraction, electron microscopy, high temperature microscopy, thermal analysis and electron spin resonance spectroscopy.The influence exerted by titanium dioxide on the phase relationships, crystal growth rates and micromorphology of the polycrystalline products of heat-treatment has been investigated and the findings used as a basis for proposals on the rôle of TiO₂ during nucleation and crystal growth.