The effect of cation substitution and non-stoichiometry on the sintering behavior and permeability of M-type barium hexaferrite

This paper demonstrated the effect of cation substitution and cation deficiency in M-type hexaferrite on the phase formation, sintering behavior and magnetic properties. Bi substitution effectively promotes the mass transfer in the sintering process by forming liquid phase, so the Bi–Co–Ti substituted samples have a sintering temperature about 200 °C lower than that of the sample with Co–Ti substitution only. Moreover, Bi substitution remarkably improves the soft magnetic properties in very high frequency (VHF). With the aid of Bi–Co–Ti substitution, proper Fe3+ deficiency decreases the sintering temperature by enhancing the mass transfer in solid phase. Among them, the x=0.15, y=0.75 sample can be sintered well at 950 °C with high density of 5.0 g/cm3, and be of the best magnetic property with both high permeability of 25 and high cut-off frequency of 480 MHz, which well facilitates the VHF applications.