抄録
Solid solutions of ilmenite (MgTiO3, MnTiO3, FeTiO3, CoTiO3 and NiTiO3) and hematite (αFe2O3) were prepared and their crystal structure was investigated by an X-ray analysis. It was confirmed that the solid solutions could be classified into three groups: 1) The specimens of ilmenite side and hematite side in the solid solution have the different crystal symmetries; R\bar3 and R\bar3c respectively and there exists a miscibility gap between them (MnTiO3, MgTiO3 and CoTiO3 series). 2) Ilmenite and hematite make the solid solution in the whole range of composition and the crystal symmetry changes from R\bar3 to R\bar3c continuously (NiTiO3 series). 3) The ranges of the crystal symmetries R\bar3 and R\bar3c of the solid solution are overlapped with each other and a transformation from R\bar3 to R\bar3c is observed in one specimen of the overlapped range (FeTiO3 series). Such differences among different ilmenite and hematite systems may be attributed to the following three factors; differences in ionic radii, in electronic conductivity and in stability of other two solid solution series with spinel and pseudobrookite structures which exist in a ternary system of MeO-Fe2O3-TiO2.
