A topotactic technique for the production of mechanically oriented planar hexaferrites

Polycrystalline oriented specimens of planar hexagonal ferrites, Ba2Co2xZn2-2xFe12O22, were obtained by chemical reaction of an oxide mixture containing a mechanically oriented component. The method was simply to subject to uniaxial pressure the starting mixture containing acicular particles of α-FeOOH, without any external magnetic field. The degree of orientation of sintered specimens depends on the preparation parameters and the chemical sample composition. The prepared samples were tested by magnetic and X-ray measurements and optical microscopy. The pressure was found to have a direct influence on the sample orientation, while the sintering temperature determined the grain dimensions and the final product quality. The best orientation is observed in Co rich samples.