Oriented growth of a β-quartz solid solution from a MgO–Al₂O₃–SiO₂glass coated by a sol–gel ZrO₂layer

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.