Ceramics-Silikáty 55 (2) 188-194 (2011)

CRYSTALLIZATION KINETICS OF GLASS-CERAMICS BY DIFFERENTIAL THERMAL ANALYSIS

M. Ghasemzadeh, A. Nemati, A. Nozad, Z. Hamnabard, S. Baghshahi

The crystallization behavior of fluorphlogopite, a glass-ceramic in the MgO–SiO₂–Al₂O₃–K₂O–B₂O₃–F system, was studied by substitution of Li₂O for K₂O in the glass composition. DTA, XRD and SEM were used for the study of crystallization behavior, formed phases and microstructure of the resulting glass-ceramics. Crystallization kinetics of the glass was investigated under non-isothermal conditions, using the formal theory of transformations for heterogeneous nucleation. The crystallization results were analyzed, and both the activation energy of crystallization process as well as the crystallization mechanism were characterized. Calculated kinetic parameters indicated that the appropriate crystallization mechanism was bulk crystallization for base glass and the sample with addition of Li₂O. Non-isothermal DTA experiments showed that the crystallization activation energies of base glasses was in the range of 234-246 KJ/mol and in the samples with addition of Li₂O was changed to the range of 317-322 KJ/mol.

Keywords: Crystallization kinetics; Activation energies; Glass ceramics; Microstructure; Phlogopite