PHASE RELATIONS AND STABILITIES OF COMPOUNDS IN SYSTEM COO-TIO2

Phase relations in the system CoOTiO2 in the temperature range 1130-1569°C have been determined by the quenching technique. Three crystalline phases, in addition to the end members CoO and TiO2, are stable in equilibrium with liquids, viz. Co2TiO4, CoTiO3 and CoTi2O5. The two former melt congruently at 1562 and 1463°C, respectively, whereas the latter melts incongruently at 1482°C. The phase CoTi2O5 is unstable relative to the phase assemblage CoTiO3 + TiO2 below ≈ 1140°C. The free energies of formation of the three crystalline phases from their oxide components at 1100 and 1300°C were determined by studying equilibria between pairs of crystalline oxide phases, metallic cobalt and a gas phase of known oxygen pressures. The instability of CoTi2O5 relative to the phase assemblage CoTiO3 + TiO2 below ≈ 1140°C is confirmed by the free-energy data obtained. © 1969.