Coupled substitution of NiO and TiO2 in hematite

The partitionings of NiO and of NiO and TiO2 between hematite and Na2O 2B(2 )O(3) melts were studied by the flux growth method as a function of solute concentration. The substitution mechanisms of NiO and/or TiO2 in -Fe2O3 lat tice were discussed based on the concentration dependence of the distributi on coefficients. The substitution of Ni2+ ion for Fe3+ was accompanied by t he charge compensating oxygen ion vacancies, while the coupled substitution of Ni2+ and Ti4+ ions for Fe3+ was accompanied by the formation of Fe2+ io n, which was confirmed by chemical analysis.