Thermal and spectroscopic characterization of glasses and glass-ceramics of Li_2O-Al_2O_3-SiO_2 (LAS) system*

摘要

Research were focused on obtaining Li_2O-Al_2O_3-SiO_2 glass-ceramics where crystallization of both Lidi- 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%): SiO_2 66.3%; Al_2O_3 10.2%; Li_2O 12.1%; CaO 1.46%; K_2O 0.53%; Na_2O 2.59%; P_2O_5 4.28%; ZrO_2 0.56%; CeO_2 1.5%; V_2O_5 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 ~(27)Al MAS NMR and ~(29)Si 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 Al~(3+) and silicon Si~(4+) were identified.