Synthesis and investigations of structural, magnetic and dielectric properties of Cr-substituted W-type Hexaferrites for high frequency applications

In current study, Cr-substituted W-type hexaferrites with chemical formula (BaNi2CrxFe16-xO27 for x = 0.0, 0.1, 0.2, 0.3 and 0.4) have been investigated in order to tailor the structural, magnetic and electromagnetic properties of these ferrites which can be suitable at higher working frequencies. The desired samples were prepared by the sol-gel auto-combustion technique and thereafter investigated by thermal gravimetric/differential thermal analysis (TGA/DTA), X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy(SEM), energy dispersive X-ray (EDX) spectroscopy, vibrating sample mangnetometer (VSM) and vector network analyzer (VNA). The XRD peaks showed that single phase formation of these ferrites could be successfully done at a temperature of 1300 degrees C which was further confirmed from the length of minor and major axis (a, and c), unit or single cell volume (V) and theoretical density (d(x)). It was observed that the values of all these parameters were consistent with the previously reported literature. The SEM images exhibited platelet like and hexagonal shape morphology which is very suitable shape for microwave absorbing applications.IR spectrum for sintered sample revealed two well defined absorption peaks which correspond to tetrahedral A- and octahedral B-sites present in W-type hexagonal lattice. The magnetic hysteresis loops for all the prepared samples were found to be thinner having a low value of coercivity (similar to a few hundred Oersted) revealing the soft magnetic nature which is a pre-requisite of high frequency applications. The high frequency dielectric parameters were also studied in frequency range (1-6GHz) and all the parameters follow the Koop's phenomenological theory which is consistent with the Maxwell-Wegner model. The observed properties indicate that these ferrites will have high prospects in high frequency applications such as dielectric resonators, multilayer chip inductors (MLCIs) and for camouflaging the important military arsenals such as aircraft, ship and tank etc.