Effects of P2O5 and heat treatment on crystallization and microstructure in lithium disilicate glass ceramics

This paper investigated the effects of P2O5 content and heat treatment on the species of crystalline phase and microstructure of lithium disilicate glass ceramics. As P2O5 increased from 0.0 to 4.0 mol.% (G0, G1P, G2P and G4P), the crystallization temperature decreased and nucleation density increased. Therefore, the microstructure was refined from plate-like polycrystalline aggregates to interlocking rod-shaped crystals and even spherical crystalline phases. Li3PO4 crystals acted as the heterogeneous nucleation sites for Li2SiO3 crystals, which could be the precursors of Li2Si2O5 crystals. Furthermore, Li2Si2O5 probably crystallized by epitaxial growth on Li2SiO3 crystals. With increasing P2O5 content, the relative content of Li2Si2O5 crystals decreased and Li2SiO3 and Li3PO4 crystals increased in one- and two-stage treatments. Moreover, the precipitation of Li2Si2O5 crystals was hampered during the one-stage treatment. Two-stage treatment was favorable for the growth of stable Li2Si2O5 crystals. (C) 2007 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.