Formation mechanism and magnetic properties of barium hexaferrite quasi-single crystals fabricated via magnetic forming and liquid participation sintering

Highly textured barium hexaferrite material is a good candidate as the high performance gyromagnetic ferrite for self-biased and low loss millimeter wave devices. To fabricate it, a magnetic forming and liquid phase participation sintering route has been developed and its formation mechanism has been discussed based on the heating behaviors of starting powders and micro-structural characteristics of sintered bulk materials. The results indicated that the diffusion and re-crystallization of liquid phase from melting of small crystallites promoted fast densification and high orientation and led to the formation of highly textured structures. The highest grain orientation degree achieved to 0.986 at the optimum sintering temperature of 1280°C. As the grain orientation degree increased, the coercive forces of the obtained barium hexaferrite materials dramatically decreased from 5185Oe to 120Oe, while the apparent magneto-crystalline anisotropic fields linearly decreased to the value very similar to the theoretical value of single crystals. ► The formation mechanism of quasi-single crystal was diffusion and re-crystallization. ► Liquid phase from unaligned crystallites led to high densification and orientation. ► The grain orientation degree achieved 0.986 at the sintering temperature of 1280°C. ► The apparent magneto-crystalline anisotropic field decreased in the linear form. ► The coercive forces decreased from 5185 to 120Oe as grain orientation degree increased.