Crystallization kinetics of MgO-Al2O3-SiO2 transparent glass-ceramics

The non-isothermal crystallization kinetics of the MgO-Al2O3-SiO2 (MAS) glasses were analyzed with the Kissinger equation and the Augis-Bennett equation by differential scanning calorimeter (DSC) and X-ray diffraction (XRD). The results showed that two crystal phases of spinel (MgAl2O4) and SiO2 were generated sequentially in the heat treatment process. When the spinel was the only crystal phase, the MAS glass-ceramic was transparent. For glass A (containing one type alkali metal Na2O), the corresponding activation energy was Ep1 (A)=325.27kJ/mol, Ep2(A)=364.99kJ/mol; for glass B (containing Na2O and K2O), the activation energy is Ep1(B)=233.79kJ/mol, Ep2(B)=273.85kJ /mol. The average crystallization index for spinet crystal phase was n(A1)=1.99, n(B1)=2.58, By adding K+, which suggested that the spinel crystal phase precipitation have the trend to change from two-dimensional pattern to bulk crystallization.