Study on crystallization and microstructure of Li2O-Al2O3-SiO2 glass ceramics

Lithium aluminosilicate (LAS) glasses are generally difficult to prepare because of their high melting temperature. In this study, the preparation of LAS glasses was achieved at a relatively low melting temperature. The batch containing MgO-ZnO-Li2O-Al2O3-SiO2 was melted in a platinum crucible at 1550°C for 2 h and was then followed by two- or three-step heat treatment processes for nucleation and crystal growth. The characterizations were carried out by differential thermal analysis, X-ray diffraction, infrared spectroscopy, scanning electron microscopy, and UV-Vis-NIR scanning spectrophotometry. The hexagonal stuffed β-eucryptite solid solution crystallized at 840-960°C. Most of the hexagonal β-eucryptite solid solution transformed into the tetragonal β-spodumene solid solution at 1100°C. Almost all the aluminum atoms entered into the tetrahedral sites in the aluminosilicate network of the β-eucryptite/β-quartz solid solution. All of the Al atoms did not belong to the aluminosilicate network of the β-spodumene solid solution. The glass ceramic with a mean grain size of 10-20 nm is transparent, the transmittance reaches ∼85% in the visible light wavelength.