Non-stoichiometric crystallization of Li2SiO3-CaSiO3 glasses: Residual glass composition from ionic conductivity

Abstract All the properties of glass-ceramics are strongly dependent upon their nano or microstructure, including the percentage, composition and, structure of the residual glass phase. Unfortunately, however, determining the chemical composition of residual glass is far from trivial and there are very few publications on this matter. In this paper, we used electrical conductivity measurements by impedance spectroscopy to infer the composition of the residual glass in partially crystallized Li2SiO3-CaSiO3 glasses. The glass-ceramics were obtained by heat-treatment at 560 °C for distinct periods, in conditions where only lithium-metasilicate (Li2SiO3) crystallized. Consequently, residual glasses of the resulting glass-ceramics became depleted in lithium, and their ionic conductivity and the respective activation energies changed accordingly. Therefore, we obtained the compositions of residual glasses by comparing the glass-ceramics ionic conductivities and activation energies with those of reference glasses having known chemical composition. We validated these two methods by comparing the obtained residual glass compositions with those obtained using a technique that relates the glass transition temperatures of reference glasses with those of glass-ceramics. These novel methods employing ionic conductivity and activation energy yield similar results to those obtained using the glass transition temperature method. However, the electrical property techniques are non-destructive and can be used to follow the crystallization process in situ.