Novel approach to link between viscosity and structure of silicate melts via Darken's excess stability function:: Focus on the amphoteric behavior of alumina

The effect of alumina on the relationship between viscosity and structure of the CaO-SiO2-Al2O3-MgO system is investigated by employing viscometer using the rotating cylinder method and Fourier transform-infrared (FT-IR) spectra, respectively. In addition, the original Darken's excess stability function was introduced in order to understand the thermophysical phenomena and the role of alumina based on thermodynamics. Alumina behaves as an amphoteric oxide in the CaO-SiO2-Al2O3-MgO melts, and this is not only experimentally confirmed but also thermodynamically proved by taking the Darken's excess stability function into account.