Experimental Study of Phase Equilibria in the MnO-“TiO₂”-“Ti₂O₃” System

Abstract

Phase equilibria and liquidus in the system MnO-“TiO₂”-“Ti₂O₃” under controlled atmosphere have been investigated in the temperature range from 1300 to 1550°C and in the range of log pO₂ (in atm) from -7.2 (pCO/pCO₂=1) to -16.6 (C-CO equilibration). High-temperature equilibration, quenching and electron probe microanalysis (EPMA) were employed to obtain equilibrium compositions of liquid and several solid solutions. The following phases have been observed; molten oxide, manganosite (MnO (s.s.)), rutile (TiO_2-δ (s.s.)), spinel (Mn₂TiO₄-MnTi₂O₄), pyrophanite (MnTiO₃-Ti₂O₃) and pseudobrookite (“MnTi₂O₅”-Ti₃O₅) solid solutions. Liquidus of manganosite and rutile were measured and compared with previous investigations. “MnTi₂O₅” compound was confirmed to be unstable phase in the MnO-“TiO₂” system. It was found in the present study that sub-solidus phase equilibria are affected considerably by oxygen partial pressure.