Effects of Li2O on the Crystallization of Fluorosilicate Glass and Molecular Dynamics Simulation Analysis

Abstract

Alkali oxides are generally known as network modifiers which accelerate the kinetics of silicate glass. However, several kinetics studies have revealed that the addition of Li2O delayed nucleation in the fluorosilicate glass without knowing the reason. In this study, Molecular Dynamics (MD) simulation was applied to elucidate the veiled effect of Li2O addition on the fluorosilicate glass and compared with Raman / NMR spectroscopy, DSC, and FactsageTM. The tetrahedral coordination environment of fluorine changed drastically with the addition of Li2O, and consequently, the self-diffusion coefficient of fluorine decreased. The self-diffusion coefficient of fluorine was germane to the crystallization rate, and the diffusion of fluorine was the rate-determining step of the crystallization. Interestingly, delayed nucleation with Li2O was only effective in the presence of Na2O, and it rather accelerated crystallization without Na2O. It is an inaduditus form of Mixed Alkali Effect (MAE) on the crystallization of fluorosilicate, and it is expected to contribute to the effective crystallization rate control of fluorosilicate