Abstract:
Barium W-type hexagonal ferrites are significant materials having tremendous
applications in microwave absorbing materials, high-frequency devices, and
memory gadgets on account of soft magnetic nature, low priced, high efficiency,
and high saturation magnetization. In the present research work, the single-phase
and nanosized cobalt W-type hexaferrite with composition BaCo2-xNixFe16O27
(x=0.0, 0.5, 1.0, 1.5, 2.0) synthesized by chemical co-precipitation method. Powder
specimens were calcined at 1250 ⁰C for four hours. The structural properties were
investigated by XRD, SEM, and FT-IR instrumental techniques. The pure single
phase of W-type hexaferrite was affirmed by XRD. Average crystallite size was
measured in the range of 20-28nm that makes them good for EMI shielding
applications. The FT-IR absorption peaks confirmed the metal-oxygen bending and
stretching vibration of synthesized products. Magnetic measurements showed an
increase in coercivity and remanent magnetization from 136.93-531.63Oe and 5.18-
22.42 emu/g with increasing concentration of substituent. The dielectric studies
revealed enhancement of dielectric constant, dielectric loss, and tangent loss till
x=1.5 and then decreased for x=2.0 due to cation distribution. The AC impedance
spectroscopy confirmed the resistance caused by the contribution of grain
boundaries. The decreasing trend of impedance with the incorporation of Ni2+
represents that conductivity increases in substituted samples which ultimately rise
absorption of EM waves. High EMI shielding effectiveness for absorption (-
31.02dB) and low shield efficiency for reflection were measured (-3.7dB) in the
frequency range of 12-18GHz with nickel substitution (x=1.5) which make nickel
substituted W-type hexaferrites best coefficient for EMI shielding applications with
SET > -20dB.
