Sinterability, crystallization and properties of glass-ceramic tiles belonging to CaF_2-CaO-MgO-Al_2O_3-SiO_2 system

摘要

The effect of CaO substitution by different amounts of MgO on crystallization and various properties of CaF_2-CaO-Al_2O_3-SiO_2 glass system were investigated. It was shown that the properties of obtained glass-ceramics are greatly influenced by MgO contents. The Avrami exponent and activation energy for crystallization of the most promising and the MgO-free specimens were determined. Results suggested that surface crystallization was the main precipitation mechanism of both samples and while the activation energy for crystallization of MgO containing sample was less than MgO-free one, its ability to crystallize was diminished. SEM results confirm occurrence of surface crystallization of samples and depicts the phenomenon of microstructure coarsening by increasing MgO content and also reduced densification of specimen with magnesium oxide more than 9 wt. percent.