Crystal nucleation in P2O5-doped lithium disilicate glasses

摘要

The bulk (volume) crystallisation of Li2O·2SiO2(LS2) glasses with additions of 1,2 and 5 mol%P2O5 (G1P,G2Pand G5P) was investigated. In the G1P and G2P glasses heated at454℃metastable α'-and β'-LS2 crystal phases formed initiallyand only stable LS2 and later stages. In G1P heated at 463℃transmission electron microscopy (TEM) revealed particles (≥2μm) of stable LS2 but also smaller (<0.1μm) crystalline particleswhich were unstable under the electron beam and could not beidentified. Crystalline lithium orthophosphate (Li3PO4) wasdetected by XRD and 31P magic angle spinning nuclear magneticresonance (MAS-NMR) in both as-quenched and heat treated G5Pbut not in G1P and G2P. In G5P heated at 476℃ , metastableα'-LS2 phase initially formed and at later times stable LS2.