Effect of K<sub>2</sub>O/SiO<sub>2</sub> ratio on the crystallization of leucite in silicate-based glasses
Keywords:Leucite, Quenching, Heat treatment, Glass-ceramics, X-ray diffraction
AbstractLeucite-based glass-ceramics were prepared by controlled crystallization of suitable glass compositions to give required crystalline phase/s. Three glass batches in the system SiO2 - K2O - NaO2 - Al2O3 - TiO2 - CaO were prepared by varying K2O/SiO2 ratio, then melted and quenched. Glasses were characterized for onset of crystallization temperatures by differential thermal analysis (DTA), and heat treatments were carried out from 850 â€“ 1000Â°C for 4 hours for controlled crystallization of leucite phase. Physical, chemical and crystal structure characterizations were carried out using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). XRD found leucite as a major phase in all heat treatment temperatures. Increasing the heat treatment temperature as well as increasing the amount of K2O/SiO2 ratio caused the amount of leucite phase to increase also. The silicate chain structure was found from FT-IR analysis, which confirmed the appearance of leucite phase. SEM indicated that increasing K2O/SiO2 ratio in the glass batch led to a slight increase in the crystal size, and also a slight change in the morphology of the leucite phase. Glass with the highest K2O/SiO2 ratio in this study, when heat-treated at 1000Â°C, showed an increased amount of secondary phase/s as opposed to the main leucite phase according to XRD data.
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