Structural, physicochemical and dielectric features of Gd3+ substituted Ba–Zn–Y-hexa-ferrites for microwave absorption applications

Abstract

Hexa-ferrites have been superior for their spectacular performance in several fields, such as EMI shielding, microwave or radar absorption, and stealth applications. At the same time, this performance is based on minimizing reflection loss, a key feature of hexaferrites. In this work, Gd- substituted Y-type ferrites with chemical composition Ba₂Zn₂Gd_xFe_12-xO₂₂ (0.00 ≤ x ≤ 0.10, with a single step of 0.025) were fabricated using the sol-gel auto ignition technique. All materials were kept at 1150 °C for five and a half hours for sintering. The Gd³⁺ substituted samples were investigated via the XRD technique to study phase development. The obtained XRD patterns confirmed the formation of pure Y-type hexagonal ferrites. Microstructure analysis is done through a scanning electron microscope (SEM). By FTIR spectroscopy in the range 400–4000 cm⁻¹, IR vibrational bands appeared. These bands from 400 to 600 cm⁻¹ were for structural confirmation. Raman spectroscopy was another source of structural investigation in terms of active Raman modes. Variation in Raman spectra with substitution was also observed. The change in surface composition was observed using X-ray photoelectron spectroscopy (XPS). The dielectric parameters, including Real and imaginary permittivity (ε′ and ε''), Loss Tan factor, Complex electric modulus, and AC conductivity, were calculated from 1 MHz to 6 GHz. These parameters showed decreasing behavior with Gadolinium substitution. The Cole-Cole plots showed a single semicircle and revealed the involvement of grain walls for conduction. Due to low values of losses, the Y-Ferrites are employed in hyper-frequency range applications and are applicable as (multi-layer chip inductor) MLCI. The minimum reflection loss is −60.98 dB for sample x = 0.025. As a result, the prepared materials are crucial, such as microwave/radar absorbers and designing EMI shielding materials.