Effect of MgO on the structure of SiO 2 ‐poor/rich MgO‐CaO‐SiO 2 melts by in situ high temperature time‐gated Raman spectroscopy and theoretical calculation

The effect of MgO on the microstructures and macroscopic properties of SiO2-poor/rich MgO-CaO-SiO2 melts was investigated by in situ high temperature time-gated Raman spectroscopy coupled with aerodynamic levitation heating of molten samples. Results of density functional theory calculations of Mg2SiO4, γ-Ca2SiO4, and MgCaSiO4 crystals and quantum chemistry ab initio simulations of Q0 species (Q0 refers to tetrahedral Si-O units without bridging oxygen) of SiO2-poor series MgO-CaO-SiO2 molten samples certified that with the substitution of CaO by MgO, the variation of Raman intensity at 900–1100 cm−1 of xMgO-(2-x)CaO-SiO2 melts was caused by the antisymmetric stretching vibration modes of distorted silicon-oxygen tetrahedra. The experimental result of SiO2-rich series of MgO-CaO-SiO2 molten samples could identify various Qi species quantitatively and demonstrated that with the substitution of CaO by MgO, the abundance of Q3 species dramatically decreased, but Q4 species increased slightly, whereas Q1 and Q2 species maintain insignificant change. A positive correlation between viscosity and the abundance ratio of Q3 to Q4 was assumed and illustrated.