Influence of La-Substitution and SiO2 Additives on Structure, Magnetic and High Frequency Dielectric Properties of Co2W Hexagonal Ferrites Synthesized by Sol–Gel Auto-Combustion Method

Abstract

The technique employed to prepare nanostructured powder of La-substituted barium ferrite of W-type, BaCo₂La_xFe_16-xO₂₇ (x = 0, 0.1) and BaCo₂La_0.1Fe_15.9O₂₇/SiO₂ is sol gel autocombustion in this research study. This study has the objective to observe the influence of SiO₂ and La-substitution on dielectric, magnetic in addition to structural parameters of W-type hexagonal lattice. All the samples sintered at 1000 °C have hexagonal crystal structure as observed by X-ray Diffraction patterns, in addition, the diffraction peaks of SiO₂ were not observed due to its amorphous nature. Fourier transform infrared spectroscopy provides indication of co-existence of SiO₂ along with two typical absorption bands for hexa-ferrites. The grain sizes and microstructures of all samples were observed by scanning electron microscopy that have range in nanometers. Vibrating sample magnetometer was used to determine the magnetic parameters including remanence (M_r), saturation magnetization (M_s), coercivity (H_c), anisotropy constant, magnetic moments (n_B) and anisotropy field. The measured AC susceptibility of hexagonal ferrites was observed to decrease with increasing temperature and shows a minimum value at Curie temperature (T_c). After substituting lanthanum (La) and adding SiO₂ in the samples, the reduction in T_c was also observed which might be due to the nonmagnetic nature of these constituents. The values of dielectric constant and dielectric loss were observed to decrease when frequency was increased and increased with increase in temperature following the Maxwell Wagner model. The addition of SiO₂ and La-substitution in hexaferrites increased DC resistivity to make these materials suitable for high frequency microwave devices such as dielectric resonators etc.