Thermal and spectroscopic characterization of glasses and glass-ceramics of Li2O-Al2O3-SiO2 (LAS) system

Research were focused on obtaining Li2O-Al2O3-SiO2 glass-ceramics where crystallization of both Li-di-silicate and Li-alumina-silicates occurs. DTA techniques were used to determine the basic glass temperature/time crystallization profile of the set chemical composition (wt%): SiO2 66.3%; Al2O3 10.2%; Li2O 12.1%; CaO 1.46%; K2O 0.53%; Na2O 2.59%; P2O5 4.28%; ZrO2 0.56%; CeO2 1.5%; V2O5 0.04%. In order to define in material the crystallization degree and phase composition after particular thermal treatments, XRD method was used. On this base the proportion of main, Li-di-silicate and Li-Al-silicates, crystalline phases was defined. As a complementary, the spectroscopic FTIR examinations has been performed. After temperature/time thermal treatment of basic glass, FTIR spectra were changing: bands correlated with crystalline phases became sharper and split. This indicated increase the crystallization in material after particular heat treatments. For the investigated glasses and glass-ceramics Al-27 MAS NMR and Si-29 MAS NMR spectra was also measured. These spectra indicated what was the local structure of the alumina Al and silica Si in examined glasses and glass-ceramics. On this base various Q(n) units of aluminum Al3+ and silicon Si4+ were identified. (C) 2014 Elsevier B.V. All rights reserved.