EFFECT OF PRESSURE ON CRYSTALLIZATION KINETICS OF CORDIERITE GLASS

The effect of pressure on the crystal growth rate and bulk nucleation rate of cordierite (2MgO.2Al2O3.5SiO2) in glass of the stoichiometric composition was measured. The crystal nucleation barrier was eliminated by seeding the surface of the cordierite glass with crystals. Crystal growth kinetics were determined independently from the nucleation kinetics by comparing the amount of surface seeded crystal growth and bulk-nucleated growth. Time dependence of crystal growth changes from linear at low pressure (0-2 kbar) to square root of time at high pressure (> 5 kbar). In both regimes of growth, increasing pressure was found to retard the crystal growth rate and increase bulk nucleation time. The pressure effect is discussed in terms of structure and transport properties in cordierite and in other silicates melts and glasses.