Effect of K2O on structure–property relationships and phase transformations in Li2O–SiO2 glasses

• Published in: Journal of the European Ceramic Society 2012-02, Vol.32 (2), p.291-298
• Main Authors: Fernandes, H R, Tulyaganov, D U, Goel, A, Ferreira, J M F
• Format: Article
• Language: English
• Subjects: Devitrification; Droplets; Glass; Lithium; Matrices; Nanostructure; Networks; Phase separation
• ISSN: 0955-2219
• DOI: 10.1016/j.jeurceramsoc.2011.09.017

Glass compositions with the formula (71.78-x)SiO2-2.63Al2O3-(2.63+x)K2O-23.7Li2O (mol%, x = 0-10) and SiO2/Li2O molar ratios far beyond that of stoichiometric lithium disilicate (Li2Si2O5) were prepared by a conventional melt-quenching technique to investigate the influence of K2O content on the structural transformations and devitrification behaviour of glasses in the Li2O-SiO2 system. SEM examination of the as cast non-annealed glasses revealed the presence of nanosized droplets in the glassy matrices suggesting the occurrence of liquid-liquid phase separation. An overall trend towards depolymerisation of the silicate glass network with increasing K2O content was demonstrated by MAS-NMR. The distribution of structural units in the experimental glasses was estimated using 29Si MAS-NMR suggesting the appearance of Q2, enhancement of Q3 and diminishing of Q4 groups with increasing K2O contents. XRD and DTA were used to assess the influence of K2O on the devitrification process and the formation of lithium disilicate (Li2Si2O5) and/or lithium metasilicate (Li2SiO3) crystalline phases.