BiFeO3 tailored low loss M-type hexaferrite composites having equivalent permeability and permittivity for very high frequency applications

Co-Ti substituted M-type hexaferrite composites, consisting of Ba(CoTi)1.2Fe9.6O19 with various amounts of Bi2O3 (0-8 wt%), were successfully synthesized by conventional ceramic processes. The effects of Bi2O3 upon the composite microstructure, magnetic properties, and magnetic and dielectric properties sintered at low temperatures were systematically investigated. The present studies aim to develop magneto-dielectric materials possessing equivalent values of permeability and permittivity, as well as low magnetic and dielectric losses, which allow for miniaturizing efficient antennas at the very high frequency band (VHF, 30-300 MHz). The present experiments show that addition of BiFeO3, observed in the polycrystalline hexaferrite composites, acts to reduce loss factors (i.e., tan δμ/μ′ = 0.014, tan δε/ε′ = 0.00071) while concomitantly retaining high and equivalent values of permeability and permittivity (i.e., μ′ ∼ 12 and ε′ ∼ 12 at 300 MHz).