Structural characterisation and thermo-physical properties of glasses in the Li2O-SiO2-Al2O3-K2O system

This article aims to shed some light on the structure and thermo-physical properties of lithium disilicate glasses in the system Li2O-SiO2-Al2O3-K2O. A glass with nominal composition 23Li(2)O-77SiO(2) (mol%) (labelled as L23S77) and glasses containing Al2O3 and K2O with SiO2/Li2O molar ratios (3.13-4.88) were produced by conventional melt-quenching technique in bulk and frit forms. The glass-ceramics (GCs) were obtained from nucleation and crystallisation of monolithic bulk glasses as well as via sintering and crystallisation of glass powder compacts. The structure of glasses as investigated by magic angle spinning-nuclear magnetic resonance (MAS-NMR) depict the role of Al2O3 as glass network former with four-fold coordination, i.e., Al(IV) species while silicon exists predominantly as a mixture of Q (3) and Q (4) (Si) structural units. The qualitative as well as quantitative crystalline phase evolution in glasses was followed by differential thermal analysis (DTA), X-ray diffraction (XRD) adjoined with Rietveld-reference intensity ratio (R.I.R.) method, Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The possible correlation amongst structural features of glasses, phase composition and thermo-physical properties of GCs has been discussed.