MICROSTRUCTURES OF ALKOXIDE-DERIVED BARIUM OSUMILITE (BAMG2AL6SI9O30)GLASS-CERAMICS

The crystallisation sequence of stoichiometric barium osumilite prepar ed by partial-alkoxide (PAR) and all-alkoxide routes (AAR) and the mic rostructure of the fully crystallised glass ceramic were examined. Com paring the crystallisation behaviours of the gel-glasses obtained reve aled that the first phase to crystallise was mullite in PAR but hexace lsian in AAR. Barium osumilite crystals grew randomly and more homogen eously in PAR while in AAR larger barium osumilite crystals grew in cl usters. Cordierite formed as a secondary phase in both routes and it c rystallised on and between the osumilite lamellae. Mullite and hexacel sian also persisted up to the stage when full crystallisation had take n place.