Crystallisation of silicate and phosphate glasses

An overview is given of recent studies of crystal nucleation and growth in silicate and phosphate based glasses, emphasising microstructural characterisation. The following topics are discussed: nucleation kinetics in silicate systems, comparisons with classical theory, and new evidence in the early stages of crystallisation of Li2O . 2SiO(2) glass for the appearance of previously unreported metastable precursor phases, probably crystalline polymorphs of lithium disilicate; the role of P2O5 as a nucleating agent in lithia-silica glasses; volume nucleation and glass ceramic formation in CaO-P2O5 based glasses, particularly the roles of additions of Al2O3, TiO2, SiO2 and B2O3; crystallisation of aluminosilicate glasses including celsian and barium osumilite compositions, and marked differences in crystallisation between melt-derived and sol-gel derived compositions. (C) 1997 Elsevier Science B.V.