Composition and crystallization kinetics of R2O–Al2O3–SiO2 glass–ceramics

The crystallization behavior and microstructure of R2O–Al2O3–SiO2 (R means K, Na and Li) glass were investigated by means of differential scanning calorimeter (DSC), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The crystallization kinetic parameters including the crystallization apparent activation energy (Ea), the Avrami parameter (n), glass transition temperature (Tg) and the activity energy of glass transition (Et) were also measured with different methods. The results have shown that: the DSC traces of composition A parent glass have two different precipitation crystallization peaks corresponding to Ea1(A) = 151.4 kJ/mol (Li2SiO3) and Ea2(A) = 623.1 kJ/mol (Li2Si2O5), the average value of n = 1.70 (Li2Si2O5) for the surface crystallization and Et(A) = 202.8 kJ/mol. And Ea(B) = 50.7 kJ/mol (Li2SiO3), the average value of n = 3.89 (Li2SiO3) for the bulk crystallization and Et (B) = 220.4 kJ/mol for the composition B parent glass. Because of the content of R2O is bigger than composition A, composition B parent glass has a lower Ea, Tg and a larger n, Et.