Hydrothermal processings to produce magnetic particulates

α-Fe₂O₃, γ-Fe₂O₃ , and α-FeOOH powders were used as starting materials to prepare barium hexaferrite hydrothermally. Since strontium hexaferrite and lanthanum-doped calcium hexaferrite have coercivities similar to that of barium ferrite, the hydrothermal synthesis of strontium hexaferrite and lanthanum-doped calcium hexaferrite were also explored. The reaction products obtained with the various starting materials are described. Electron micrographs showed that α-Fe₂O₃, γ-Fe₂O₃, or α-FeOOH dissolved in the solution first, and then barium hexaferrite nucleated and grew from the solution