Abstract
Hydrothermal crystallization of a series of mixed iron and titanium oxide coprecipitates at 2.2 kbar and at temperatures in the range 150-260°C produced single-phase pseudorutile-related products for the composition range 0.3 ≤ Ti/(Ti+Fe) ≤ 0.6. The samples were characterized using thermal analysis (DTA/DTG) and X-ray powder diffraction (XRD) techniques, as being poorly ordered unit-cell intergrowths of iron oxyhydroxide (goethite type) and titanium oxide (rutile type). A parallel study on natural pseudorutile showed that the mineral has very similar properties to the synthetic phases and that it should properly be considered as an oxyhydroxide mineral rather than as an oxide or oxide-hydrate as it has been previously described. Its structure comprises a statistical distribution of twin-variants of a goethite-rutile intergrowth structure in microdomains of average dimension 40-50Å.
