Effect of CaF₂ Addition on the Crystallization and Phase Formation in Li₂O–ZnO–Al₂O₃–SiO₂ Glass–Ceramic

Abstract

Four sets of Li 2 O-ZnO-Al 2 O 3 -SiO 2 (LZAS) glass-ceramics containing different content of fluorine were fabricated. With CaF 2 content increasing, the glass transition temperature (T g ) and crystallization temperature (T c1 , or T c2 ) decreased as differential scanning calorimetry results showed; this phenomenon could be explained based on the Fourier-transformed infrared spectra analysis. X-ray diffraction (XRD) results indicated that CaF 2 did influence the crystallization temperatures of some crystal phase in the LZAS glass-ceramics, the transformations from glass to b-quartz ss solid solution and b-quartz ss to b-spodumene occurred at lower temperatures, and the decrease could reach to 80°C. According to the scanning electron microscope analysis, the addition of F À ions can contribute to a microstructure with higher crystallinity and finer grain size. The density and average thermal coefficients of the studied glass-ceramics were influenced by the content of F À ions. All the results showed that CaF 2 did promote initial crystallization of LZAS glass and can be used as an effective nucleating agent in the LZAS system. *