Orientational changes during the surface crystallisation of cordierite from a B2O3/Al2O3/MgO/SiO2 glass

Abstract

A glass of the wt% composition 6B₂O₃·25Al₂O₃·10MgO·59SiO₂ was melted and annealed in order to study the influence of boron on the surface crystallisation of cordierite. The samples were annealed at 1050 °C for up to 3 h in order to crystallise indialite and analysed using XRD, AFM and SEM-based techniques, especially EBSD. The results show significant orientational changes within single grains along the immediate surface of the sample as well as the formation of a diffusion layer of residual glass during crystallisation. During cooling, a liquid/liquid phase separation occurs in this residual glass and silimanite is formed as an additional crystalline phase.