Effect of Al2O3 and K2O content on structure, properties and devitrification of glasses in the Li2O-SiO2 system
authors Fernandes, HR; Tulyaganov, DU; Goel, A; Ribeiro, MJ; Pascual, MJ; Ferreira, JMF
nationality International
journal JOURNAL OF THE EUROPEAN CERAMIC SOCIETY
author keywords Sintering; Microstructure-final; Glass; Glass ceramics; Lithium disilicate
keywords LITHIUM DISILICATE GLASS; FIXED VISCOSITY POINTS; CRYSTALLIZATION KINETICS; SILICATE-GLASSES; PHASE-CHANGE; CERAMICS; MICROSTRUCTURE; NUCLEATION; P2O5; TEMPERATURE
abstract The effect of Al2O3 and K2O content on structure, sintering and devitrification behaviour of glasses in the Li2O SiO2 system along with the properties of the resultant glass ceramics (GCs) was investigated. Glasses containing Al2O3 and K2O and featuring SiO2/Li2O molar ratios (3.13-4.88) far beyond that of lithium disilicate (Li2Si2O5) stoichiometry were produced by conventional melt-quenching technique along with a bicomponent glass with a composition 23Li(2)O-77SiO(2) (mol.%) (L23S77). The GCs were produced through two different methods: (a) nucleation and crystallization of monolithic bulk glass, (b) sintering and crystallization of glass powder compacts. Scanning electron microscopy (SEM) examination of as cast non-annealed monolithic glasses revealed precipitation of nanosize droplet phase in glassy matrices suggesting the occurrence of phase separation in all investigated compositions. The extent of segregation, as judged from the mean droplet diameter and the packing density of droplet phase, decreased with increasing Al2O3 and K2O content in the glasses. The crystallization of glasses richer in Al2O3 and K2O was dominated by surface nucleation leading to crystallization of lithium metasilicate (Li2SiO3) within the temperature range of 550-900 degrees C. On the other hand, the glass with lowest amount of Al2O3 and K2O and glass L23S77 were prone to volume nucleation and crystallization, resulting in formation of Li2Si2O5 within the temperature interval of 650-800 degrees C. Sintering and crystallization behaviour of glass powders was followed by hot stage microscopy (HSM) and differential thermal analysis (DTA), respectively. GCs from composition L23S77 demonstrated high fragility along with low flexural strength and density. The addition of Al2O3 and K2O to Li2O-SiO2 system resulted in improved densification and mechanical strength. (c) 2010 Elsevier Ltd. All rights reserved.
publisher ELSEVIER SCI LTD
issn 0955-2219
year published 2010
volume 30
issue 10
beginning page 2017
ending page 2030
digital object identifier (doi) 10.1016/j.jeurceramsoc.2010.04.017
web of science category Materials Science, Ceramics
subject category Materials Science
unique article identifier WOS:000278651400005
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journal analysis (jcr 2017):
journal impact factor 3.794
5 year journal impact factor 3.536
category normalized journal impact factor percentile 98.148
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