Enhanced microwave absorption properties of Zn-substituted Y-type hexaferrites

A partial substitution of Zn2+ for the Fe2+ site of BaY-type hexaferrite was found to be effective for the improvement of microwave absorption properties in 0.5–18 GHz. For this study, the composites of polycrystalline Ba2Fe2-xZnxFe12O22 (Ba2Fe2-xZnxY, 0.5 ≤ x ≤ 2.0) and epoxy resin were fabricated with various hexaferrite volume fractions (Vf) of 30–90%. As a result, Ba2ZnxFe2-xY (x = 0.5–1.5) composites having the partial substitution of Zn2+ exhibited larger complex permittivity values than fully Zn2+ substituted composite of Ba2Zn2Y (x = 2.0) due to an electron hopping between Fe2+ and Fe3+ ions. Because of the enhanced permittivity, Ba2Fe2-xZnxY (x = 0.5–1.5) composites with 30% of Vf possessed better impedance matching characteristics compared with other composites having larger Vf values. Consequently, Ba2Fe2-xZnxY (x = 0.5–1.5) composites exhibited excellent RL values lower than −50 dB with the thickness values ranging from 1.52 to 1.80 mm.