Structure-property relationships and densification-crystallization behaviours of simplified lithium disilicate glass compositions

authors	Fernandes, HR; Tulyaganov, DU; Pascual, MJ; Ferreira, JMF
nationality	International
journal	CERAMICS INTERNATIONAL
author keywords	Microstructure-final; Thermal properties; Glass; Glass-ceramics
keywords	MAS-NMR; LI2O-SIO2 GLASS; FORMING ABILITY; CERAMICS; K2O; MICROSTRUCTURE; STRENGTH; SYSTEM; AL2O3; MELTS
abstract	The role of each oxide component on the structure of molten glass and on their densification and crystallization behaviours is expected to be more easily assessed for compositions comprising a small number of components. In the present work, binary (Li2O-SiO2), ternary (Li2O-Al2O3-SiO2), and quaternary (Li2O-K2O-Al2O3-SiO2) glass compositions were selected. The aim was to investigate the relationships between the compositions and structure of the glasses, namely, the effects of each component on the extent of liquid-in-liquid phase separation, their thermal behaviour and the phase assemblage in the disilicate glass-ceramics. The distribution of structural units in the experimental glasses was assessed using Si-29 MAS-NMR spectroscopy. Adding Al2O3 played a dual role as network former and modifier when added to the binary system by enhancing Q(2) and diminishing Q(3) structural units. The processing window for sintering, the difference between the onset of crystallisation and glass-transition temperature (T-c-T-g), was too narrow for the less polymerised network structures (binary and ternary systems), hindering the densification of the corresponding glass powder compacts. Oppositly, compositions in the quaternary system featured excellent densification behaviour coupled with high mechanical strength. These features derive from a more rigid glass network comprising four coordinated (AlO4/2)(-) units and K+ cations in its vicinity. (C) 2013 Elsevier Ltd and Techna Group S.r.l. All rights reserved.
publisher	ELSEVIER SCI LTD
issn	0272-8842
year published	2014
volume	40
issue	1
beginning page	129
ending page	140
digital object identifier (doi)	10.1016/j.ceramint.2013.05.113
web of science category	Materials Science, Ceramics
subject category	Materials Science
unique article identifier	WOS:000330820500018