abstract
Glass compositions with formula (71.78 - x)SiO2-2.63Al(2)O(3) (2.63 + x)K2O-23.7Li(2)O (mol.%, x = 0-10) and SiO2/Li2O molar ratios far beyond that of stoichiometric lithium disilicate (Li2Si2O5) were prepared by conventional melt-quenching technique to investigate the influence of K2O content on structural transformations and devitrification behaviour of glasses in the Li2O-SiO2 system. The scanning electron microscopy (SEM) examination of as cast non-annealed glasses revealed the presence of nanosized droplets in glassy matrices suggesting occurrence of liquid liquid phase separation. An overall trend towards depolymerization of the silicate glass network with increasing K2O content was demonstrated by employing magic angle spinning-nuclear magnetic resonance (MAS-NMR) spectroscopy. The distribution of structural units in the experimental glasses was estimated using Si-29 MAS-NMR spectroscopy suggesting the appearance of Q(2), enhancement of Q(3) and diminishing of Q(4) groups with increasing K2O contents. X-ray diffraction (XRD) and differential thermal analysis (DTA) were used to assess the influence of K2O on devitrification process and formation of lithium disilicate (Li2Si2O5) and/or lithium metasilicate (Li2SiO3) crystalline phases. (C) 2011 Elsevier Ltd. All rights reserved.
keywords
LITHIUM DISILICATE GLASS; CRYSTALLIZATION KINETICS; MAS-NMR; CERAMICS; STRENGTH; MICROSTRUCTURE; AL2O3
subject category
Materials Science
authors
Fernandes, HR; Tulyaganov, DU; Goel, A; Ferreira, JMF
our authors
Hugo Alexandre Gonçalves da Rocha Fernandes
Researcher
José Maria da Fonte Ferreira
Associate Professor with Aggregationacknowledgements
Hugo R. Fernandes is grateful for the financial support of CICECO and for the PhD grant (SFRH/BD/41307/2007) from the FCT, Portugal.