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

Abstract

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 β-spodumene (LiAlSi2O6), lithium disilicate (Li2Si2O5), lithium metasilicate (Li2SiO3), and lithium orthophosphate (Li3PO4) crystalline phases. β-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.