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 SiO 2 ‐poor/rich MgO‐CaO‐SiO 2 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 Mg 2 SiO 4 , γ ‐Ca 2 SiO 4 , and MgCaSiO 4 crystals and quantum chemistry ab initio simulations of Q 0 species ( Q 0 refers to tetrahedral Si‐O units without bridging oxygen) of SiO 2 ‐poor series MgO‐CaO‐SiO 2 molten samples certified that with the substitution of CaO by MgO, the variation of Raman intensity at 900–1100 cm −1 of x MgO‐(2‐ x )CaO‐SiO 2 melts was caused by the antisymmetric stretching vibration modes of distorted silicon‐oxygen tetrahedra. The experimental result of SiO 2 ‐rich series of MgO‐CaO‐SiO 2 molten samples could identify various Q i species quantitatively and demonstrated that with the substitution of CaO by MgO, the abundance of Q 3 species dramatically decreased, but Q 4 species increased slightly, whereas Q 1 and Q 2 species maintain insignificant change. A positive correlation between viscosity and the abundance ratio of Q 3 to Q 4 was assumed and illustrated.