Gas-to-solid condensation in a Mg–SiO–H2–O2 vapor: metastable eutectics in the MgO–SiO2 phase diagram

Abstract

Kinetically controlled gas-to-solid condensation in Mg–SiO–H₂–O₂ vapors resulted in the formation of amorphous, chemically ordered, solid compositions at 26 ± 7, 46.5 ± 2 and 87 ± 3.5 wt.% MgO. The first two solid compositions match those of metastable eutectics in existing MgO–SiO₂ phase diagrams. An explanation for the highest-MgO metastable solid compositions requires a revision of this phase diagram to include a eutectic at ∼95 wt.% MgO.