Nucleation, Crystallization and Characterization of Mica-Based Glass-Ceramics with Fluorapatite

摘要

The glass system of SiO_2-Al_2O_3-MgO-MgF_2-SrCO_3-CaCO_3-CaF_2-P_2O_5 was used to prepare machinable glass-ceramics for restorative dental applications. The aim of this study was to apply various heat treatments to produce mica-based glass-ceramics. Differential Thermal Analysis (DTA) was used to determine the optimal heat treatment conditions for nucleation and growth of the crystalline phases in the quenched glass. It was found that the optimum nucleation temperatures for the first and the second crystallization temperatures (T_(p1) and T_(p2)) were 642°C and 635°C, respectively, and the optimum nucleation times were between 2 and 4 hours. X-ray Diffraction (XRD) showed the phases developed were anorthite, calcium-mica, fluorapatite, strontium apatite, forsterite, fluorite and stishovite phases. The microstructures of glass-ceramics were observed by Scanning electron microscope (SEM), found to exhibit plate-like mica crystals with high interlocking and randomly oriented with a higher soaking temperature and prolongation of the soaking time for crystallization.