Influence of heat treatment regimes on crystalline phase formation and physical properties of Li2O-SiO2-Al2O3 glass system

The purpose of this research is to examine the influence of heat treatment regimes on crystalline phase formation and physical properties of Li2O-SiO2-Al2O3 glass system. The LAS glass samples with the composition 13.32 Li2O-65.98 SiO2-10.84 Al2O3-4.16 P2O5-2.35 Na2O-1.44 CaO-0.84 BaO-0.52 K2O-0.52 ZrO2-0.03 TiO2 (in wt%) were prepared via melt-quench method. The glass samples underwent triple-step heat treatment regimes according to the Differential Thermal Analysis (DTA) data. The glass sample composition and phase identification were determined using x-ray fluorescence spectroscopy and x-ray diffractometer (XRD) respectively. The average crystal size of the crystalline phases was determined using Debye-Scherrer equation. The hardness, compressional wave velocity, Elastic modulus, and density of the prepared glass and glass-ceramics samples were measured. Results of the analysis revealed beta-spodumene (LiAlSi2O6), lithium disilicate (Li2Si2O5), lithium metasilicate (Li2SiO3), and lithium orthophosphate (Li3PO4) crystalline phases. beta-spodumene shows dominance over other crystalline phases. The LAS glass-ceramics recorded an average hardness of 6.0 GPa, compressional wave velocity of 6882 m s(-1), and Elastic modulus of 93.5 +/- 0.42 GPa. The increasing crystallinity of LiAlSi2O6 and Li2Si2O5 phases and the reduction of the average crystal size of the Li2Si2O5 phase (from 72.56 nm-21.81 nm) guaranteed the improvement of the mechanical properties. The LAS glass-ceramics show higher bulk density compared to the parent glass. The results suggest that the developed LAS glass-ceramics can be used as dental restorative materials.