XRD investigation of metastable phase formation in Li2O-2SiO(2) glass

Metastable crystal phase formation in lithium disilicate glass has been a s ubject of controversy for many years. However, recent evidence mainly obtai ned via the use of electron microscopy has provided strong evidence for for mation of metastable phases during the early stages of crystallization in t his composition. Very recently, however, a study has appeared which suggest s that these metastable phases are long-lived and can be detected with the aid of XRD. Here, we present XRD results obtained for lithium disilicate gl asses which were heated for various time periods at several temperatures in the nucleation regime. In no case do we find any evidence for metastable p hase formation. possible causes for the discrepancy between the present and previous experimental results are discussed. (C) 1999 Elsevier Science B.V . All rights reserved.