Crystal growth in a multicomponent lithia aluminosilicate glass

An industrially melted glass with complex composition in the Li2O-Al2O3-SiO2 system was annealed at temperatures in the range from 700 to 1000 degrees C. At temperatures up to 825 degrees C, a beta-quartz solid solution crystallized, while at higher annealing temperatures keatite was formed. Up to an annealing temperature of 850 degrees C, the samples were transparent. During annealing at 750 degrees C, the concentration of the formed beta-quartz crystals increased up to a value of 80 wt%, however, the number of crystals remained constant (within the limits of error) for annealing times from 4 to 120 h. Within that period of time, a slight increase in the mean crystallite size (from 16 to 22 nm) was observed, while the lattice parameter (a-axis) decreased. As shown by Rietveld refinement, during annealing, the SiO2-concentration of the crystals increased continuously, and the beta-quartz solid solution was depleted in Li2O, MgO and Al2O3. During crystallization, the viscosity of the glass phase increased which decelerated further crystal growth. Finally, the crystallization was frozen in. (C) 2009 Elsevier B.V. All rights reserved.