Study of the devitrification behaviour of a barium magnesium aluminosilicate glass-ceramic

This work presents the most important aspects of the devitrification behaviour of a barium magnesium aluminosilicate (BMAS) glass-ceramic with the Ba-osumilite stoichiometry. The melt-derived BMAS glass-ceramic was first pulverised and subsequently hot pressed to produce sintered powder compacts, some of which were subjected to post-sintering heat treatments in air. The BMAS glass devitrification behaviour was studied by means of scanning electron microscopy (SEM), electron probe microanalysis (EPMA), transmission electron microscopy (TEM), and X-ray diffraction (XRD). This study revealed that at temperatures <1000 °C, the BMAS glass crystallisation yielded several metastable crystalline phases (i.e. celsian, hexacelsian, α/β-cordierite, and β-quartzss) instead of the thermodynamically stable Ba-osumilite. On the other hand, annealing of the BMAS glass at temperatures ≥1000 °C caused the transformation of all metastable phases to Ba-osumilite. Understanding the crystallisation behaviour of the BMAS glass-ceramic is essential in order to use this material as matrix in fibre-reinforced composites suitable for high-temperature structural applications.