INFLUENCE OF OXYGEN PARTIAL-PRESSURE ON THE QUASI-TERNARY SYSTEM CR-MN-TI OXIDE

The quasi-ternary system Cr-Mn-Ti oxide was investigated at 1000-degrees-C under oxygen partial pressures ranging from 0.21 bar to 10(-21) bar (I bar = 10(5) Pa). X-ray diffraction analysis was used to identify phases and determine lattice parameters. The positions of phase boundaries as a function of oxygen partial pressure were measured using the emf method. The spinel MnCr2O4 may be regarded as the most interesting compound in this system. Part of the chromium can be replaced by trivalent titanium at low oxygen partial pressures and by trivalent manganese at high pressures, and the formation of a limited solid solution with the spinel Mn2TiO4 is possible in all cases. As a result, a coherent single-phase spinel region exists over the entire oxygen partial pressure range at 1000-degrees-C.