Crystallization of Glasses in the System SiO2-Li2O-TiO2-Al2O3, Investigated

The processes of crystallization of fibres (diameter 10-15 μm) and coarse powders (grain size 500-1000 μm) with four compositions in the system SiO2-Li2O-TiO2-Al2O3 were studied by conventional and in situ high-temperature XRD, DTA, SEM and optical microscopy. Activation energies of crystallization and morphological indices were deduced from the kinetic curves obtained by recording the high-temperature XRD peak intensity as a function of time. The glass-ceramic fibres drawn from compositions which exhibit glass-inglass phase separation show prevailing not-oriented bulk crystallization, whereas prevailing surface crystallization was found for single-phase glass fibres. Homogeneously-dispersed crystallization was obtained on heating fibres of these compositions. The partially cocrystallized glass fibres of eutectic composition between Li-metasilicate and β-spodumene gave rise to a very fine and homogeneously-dispersed sub-microstructure. © 1984 Wiley Heyden Ltd., Chichester and Akadémiai Kiadó, Budapest.