HIGH PERFORMANCES BORON DOPED GAMMA-FE2O3 PARTICLES PREPARED FROM OXALIC PRECURSORS

We have prepared, from oxalic precursors, γ-Fe2O3 particles (L ≃ 0.15 to 0.2 µm, L/D ≃ 2 à 5) with coercivity up to 400 Oe. To preserve the particles form we have doped the oxalates by boron. We have studied tne effects due to this element during the different thermal treatments which effect the pseudomorphous transformation of oxalate particles into spinel ferrite. By ESCA spectroscopy, X-ray measurements we were able to point out the presence of Fe3BO5 phase at surface of γ-Fe2O3 particles. In spite of the important mass losses (H2O, CO, CO2) and the important crystallographic structure modifications occuring during the transformation of oxalate into magnetic oxide, γ-Fe2O3 particles obtained by this method have very good textural characteristics. These ones were compared to textural characteristics of commercially oxides by microscopic observations (TEM light and dark field, high resolution and microdiffraction). Boron doped γ-Fe2O3 particles were used to make experimental 3″1/2 diskettes with standard formulation. In these conditions, media properties were comparable to trading diskettes properties. © 1990 IEEE