Metastable phase separation and crystallization of Li2OAl2O3SiO3 glasses: Determination of miscibility gap from the lattice parameters of precipitated β-quartz solid solution

Glasses of the SiO2Li2O·1.34 Al2O3 system were separated by heat-treatment into two liquid phases: silica rich droplets and silica poor matrix glass. The metastable miscibility gap was determined from the composition dependence of the lattice parameters of β-quartz solid solution precipitated in the glasses. On the basis of the miscibility gap, it was confirmed that β-quartz solid solution crystallized within the silica poor liquid phase surrounding the silica rich droplets. The silica rich phase remained in the form of droplets during heat-treatment below the immiscibility temperature, and it was dissolved in the β-quartz solid solution upon heat-treatment above the immiscibility temperature.