The MgO–TiO 2 –SiO 2 system: Experiments and thermodynamic assessment

Phase relations in the MgO–TiO 2 –SiO 2 system have been investigated in air over a wide temperature range using the equilibration method. X‐ray powder diffraction, scanning electron microscopy combined with wave length X‐ray spectroscopy (SEM/EPMA), and differential thermal analysis (DTA) have been used for sample characterization. Based on the obtained experimental results, isothermal sections of the system at 1523, 1673, and 1773 K have been established. The solid‐state invariant reaction MgTi 2 O 5 + T‐SiO 2 ⇋P‐MgSiO 3 + TiO 2 has been detected at 1625 ± 8 K by step‐wise heat treatment. A partial liquidus projection has been suggested, and the temperatures and compositions of three eutectic invariant reactions have been experimentally measured by DTA and ex‐situ analysis of the sample microstructures after melting using SEM/EPMA. Considering the newly obtained experimental data, thermodynamic parameters describing the system have been thermodynamically evaluated within the CALPHAD approach.