Sintered strontium hexaferrite shaped by injection moulding in unidirectional magnetic and electromagnetic field

Abstract

Strontium hexaferrite permanent magnets were produced by powder injection molding (PIM). The feedstock for powder injection molding was prepared by mixing strontium hexaferrite powder with a "Solvent system" organic binder. Injection was performed in the cylindrical cavity of the mold both for isotropic and anisotropic green samples. Diametrical alignment was attained using high energy permanent magnets embedded in the mold (unidirectional magnetic field), while axial magnetic alignment was done by DC current passing through a solenoid placed around the cavity (electromagnetic field). Green samples (with and without magnetic alignment) were subjected to solvent debinding and subsequent thermal debinding followed by sintering. Sintering conditions were optimized in order to achieve maximum energy product. Magneto-crystalline aligning in strontium hexaferrite was studied on both green and sintered samples using X-ray diffraction, scanning electron microscopy (SEM) and magnetic measurements (hysteresisgraphs). All measurements were made in the direction parallel to the aligning magnetic field. The obtained results confirmed a high degree of magneto-crystalline alignment.