Nucleation and crystallisation of some Na2OAl2O3SiO2 and Na2OBaOAl2O3SiO2 glasses

Na2O Al2O3 2.7 SiO2 and BaO Al2O3 2 SiO2 3(Na2O Al2O3 2 SiO2) type glass compositions with P2O5, TiO2 and CaF2 as additives were studied for nucleation and Crystallisation to obtain glass-ceramics. Structural OH groups seemed to be responsible for the initiation of crystallisation. Metastable sodium zeolite was the first phase to crystallise in the glasses. This subsequently transformed into cubic carnegieite on further heat treatment. In nephelene type composition glasses the crystalline assemblage in the glass-ceramics was nephelene and rutile. In nephelene plus celsian type composition glasses, nephelene, celsian and rutile were the major crystalline phases in the glass-ceramics. © 1980