The influence of processing parameters on the orientation of barium ferrite platelets during electrophoretic deposition

Oriented deposits of hard-magnetic barium ferrite were prepared using electrophoretic deposition (EPD). A stable suspension of highly anisotropic particles with diameters of a few 100 nm and thicknesses of 10 nm was prepared in 1-butanol. The electrophoretic velocities for the two orientations of particles with respect to the electrode were calculated. The particles migrated to the electrode with the basal plane perpendicular to the electrode. The oriented deposits were formed under the influence of the hydrodynamic force near the electrode. The sintering was accompanied by an anisotropic and abnormal grain growth and the oriented, larger grains affected most significantly the overall orientation of the films. The grain size was investigated by SEM image analysis and the orientation of the films was calculated from XRD patterns and determined from magnetic measurements. The films with the best orientations were prepared with the lowest applied voltage, where the electrophoretic velocity was the slowest. The films that were prepared with step EPD and sintered at 1150 °C had a remanence-to-saturation magnetization of 0.9. The density of the film and the magnetization values were further increased by iso-static pressing of the deposits before sintering.