This paper presents the results of a study that analyses the effect of fluorine content on glass forming ability (GFA), glass stability (GS) and preferred crystallisation mechanism for a series of glasses in the SiO2-Al2O3-MgO-K2O-F system. Three glass compositions, with fluorine contents ranging from 4.50 to 5.70 wt. %, were investigated by differential scanning calorimetry (DSC). The GS was established by estimating different parameters derived from characteristic temperatures of non-isothermal DSC curves, namely, the working range (TTS), reduced glass transition temperature (Tgr), Weinberg (Kw), Hrubÿ (KH) and Lu-Liu (KLL) parameters. The prevalent crystallisation mechanism for each glass was assessed by determining the dissimilarity in crystallisation temperature (Tp) between fine ( 120°C/min) and obtaining amorphous glasses is only possible by fast cooling of the melt. In a subsequent thermal treatment, a volume crystallization mechanism will be prevalent in the process of devitrification of these F-phlogopite based glasses. Nevertheless, the increasing on the fluorine content in the glass composition leads to a variation in the location of the first developed crystals from the internal volume of the glass particle to surface sites. The results established by DSC analyses are verified by the results obtained from field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD).

R. Casasola and J. M. Pérez express their gratitude to the Spanish National Research Council (CSIC) for their contract through the JAE Program (JAEPre-08-00456 and JAEDoc-08-00362, respectively), which is co-financed by the European Social Fund. The financial support through the projects MAT 2006-05977 and MAT2013-40477-P is also recognised.

Peer reviewed