Oriented growth of a β-quartz solid solution from a MgO–Al2O3–SiO2 glass coated by a sol–gel ZrO2 layer

Abstract

Glass sheets with the mol% composition 22.5MgO·22.5Al₂O₃·55SiO₂ were coated with a thin ZrO₂ layer on both sides via sol–gel dip coating. The samples were heated in a two-step process to 850 °C for 1 h and to 1000 °C for another 3 or 20 h. X-ray diffraction (XRD), optical microscopy and scanning electron microscopy (SEM), including electron backscatter diffraction (EBSD), were performed to investigate the crystallization of this surface modified glass. Two types of indialite and a β-quartz solid solution (β-QSS) crystallize at, or near, the glass surface. After a growth selection during the first ca. 500 μm of growth, only a highly oriented β-QSS layer aligned with the c-axis perpendicular to the initial surface continues to grow into the bulk. The β-QSS was not observed if the glass was not coated with ZrO₂ before annealing. The influence of ZrO₂ on the crystallization in this system is discussed.