Understanding the structural origin of intermediate glasses

Abstract

Abstract Intermediate glasses show nearly constant elastic moduli with temperature and/or pressure. These glasses would prove useful in designing a‐thermal optical fibers for enhanced telecommunication, fiber sensing applications, and in designing glass products for applications where a broad range of thermal and mechanical stimulation is expected. In this study, intermediate glasses belonging to the Na 2 O–SiO 2 , Na 2 O–Al 2 O 3 –SiO 2 , and Na 2 O–TiO 2 –SiO 2 glass systems were identified from in situ high‐temperature Brillouin light scattering (BLS) experiments. Glasses important for engineering applications like the international simple glass (ISG) and the less brittle glass (LBG) were also found to exhibit intermediate behaviors. In situ Raman spectroscopy was used to investigate their structural evolution from room temperature to temperatures beyond T g . Raman spectra along with molecular dynamics simulations revealed common structural signatures that intermediate glasses with different compositions possess. Our study showed that the intermediate elastic behaviors come from a delicate balance between the stiffening effect associated with conformation changes in the medium‐range flexible rings and the softening effect due to the weakening of short‐range chemical bonds with temperature.