A study of microwave absorbing properties in Co–Gd doped M-type Ba–Sr hexaferrites prepared using ceramic method

M-type Barium-Stronium hexaferrites with the chemical composition Ba_0.5Sr_0.5Co_xGd_xFe_12−2xO₁₉ (x = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0) were prepared using a conventional ceramic method. X-ray diffraction (XRD) technique was used to explore the structure characterization and phase purity of the prepared compositions. The absorber testing device method was adopted for investigating the dependence of microwave absorption of ferrite compositions on substitution and thickness from 8.2 to 12.4 GHz. The quarter wavelength and impedance matching mechanism are explored to evaluate the microwave absorption. XRD analysis revealed formation of M (magnetoplumblite) phase in compositions x = 0.0, 0.2, while doped compositions (x = 0.4, 0.6, 0.8 and 1.0) displayed coexistence of M-phase along with orthorhombic phase (BaFe₂O₄). For maximum microwave absorption, the doping of Co²⁺ and Gd³⁺ leads to the reduction in thickness of composition and frequency shift from the high to low frequency region. Composition x = 0.8 exhibits good microwave absorber characteristics with 96.90% absorbed power and reflection loss of −15.0 dB at matching frequency and thickness of 8.2 GHz and 2.9 mm respectively.