Composition and texture of barium silicate crystals in fresnoite glass-ceramics by various scanning electron microscopic techniques

Abstract

Highly oriented fresnoite glass-ceramics were prepared from a non-stoichiometric melt (Ba₂TiSi₂O₈ + 0.75 SiO₂) by electrochemically induced nucleation. By using electron microscopy, cathodoluminescence (CL), electron backscatter diffraction (EBSD) and energy dispersive X-ray (EDX) spectroscopy as well as wavelength dispersive X-ray (WDX) spectroscopy, two additional barium silicate phases free of titanium were identified besides the fresnoite phase predominantly occurring throughout the sample. A barium disilicate phase (BaSi₂O₅) was found within a radius of approximately 300 µm from the Pt-wire where the nucleation was induced. At distances >300 µm a phase with the composition BaSiO₃ was detected which occurred in between the large dendritic fresnoite crystals next to an additional glassy phase which mainly consists of SiO₂. Both barium silicate phases show more intense cathodoluminescence than the fresnoite phase and the maxima in the attributed spectra were shifted to smaller wavelengths in comparison to fresnoite.