THE VARIATION IN MICROSTRUCTURE OF LITHIUM DISILICATE GLASS AND GLASS-CERAMICS

The microstructural transformation from lithium disilicate glass with the chemical composition (mol. %) SiO2 (65.35), Li2O (30.23), K2O (1.76), Al2O3 (1.77), and P2O5 (0.89) to a glass-ceramic (GC) was detailed in this study. The X-ray diffraction and Fourier Transform Infrared Spectroscopic analysis detected the crystalline phases in the GC sample, including lithium disilicate, lithium metasilicate, and traces of other crystals. The scanning electron microscopic images illustrated the characteristic interlocking microstructure of the lithium disilicate GC. The [SiO4]4- tetrahedra arranged and linked together through n shared O2- vertices to create a characteristic structural framework of each silicate phase (symbolised as Qn species). The examination of the Si 2p and O 1s high-resolution XPS spectra revealed that the structure of the GC sample possessed a broader distribution of Qn species and an increase in the proportion of low n-index Qn species compared to the glass sample. The Si 2p3/2 peak position of the glass sample shifted to a 0.26 eV lower binding energy level than that of the GC sample. This change demonstrates that lithium silicate glass readily crystallises into GC, the more stable state. The results are the arguments to determine the crystallisation mechanism and structural variation of the studied lithium disilicate system.