Crystallization process of glass-ceramic for substrate of hard disks

The crystallization process of MgO-Al2O3-SiO2 glass containing TiO2 and ZrO2 was studied by means of DTA, thermal expansion curve and XRD. Magnesium aluminium titanate appearing at 780°C promotes the crystallization of Mg-petalite at 800°C, and then the crystal phases transform to sapphirine, rutile and Zr/Ti solid solution at 930°C. β-quartz solid solution appears at 1030°C and transforms at temperature higher than 1125°C to α-cordierite, cristobalite and enstatite, while rutile and Zr/Ti solid solution transform to zircon and magnesium titanate. According to the crystallization process, a glass-ceramic with sapphirine as main phase can be prepared at 930°-1050°C. The glass-ceramic with a fine-grained structure has large elastic modulus (120 GPa) and good surface properties, so that it is an excellent material for substrate of hard disks.