Development of Z-type hexaferrites for high frequency EMI shielding applications

摘要

Highlights • This research work has been initiated with the aim of enhancing high frequency microwave absorption properties. • Z-type hexaferrites has been selected to achieve broad bandwidth for employing them at high frequency absorbing applications. • This work has involved in modifying Z-type structure by substituting Cr3+ ions for Fe3+ ions. Abstract Barium Z-type hexaferrites (Ba3Co2Cr2 x Fe24−2 x O41 with x=0, 0.3, 0.6 and 0.9) were synthesised using solid state reaction technique. X-ray diffraction (XRD) analysis confirmed the formation of single phase Z-type hexaferrite structure. From transmission electron microscopy (TEM) analysis platelet morphologies were observed in all the studied samples and the average grain size were calculated, which were around 100nm. Magnetisation measurements (M-H) and (M-T) were carried out using vibrating sample magnetometer (VSM). Saturation magnetisation (Ms) was found to decrease with increasing Cr content in the samples whereas, magnetic coercive field (Hc) and remanent magnetisation (Mr) were increased. Electromagnetic absorption properties of all the ferrite samples were tested in 2–18GHz frequency range using Agilent Vector Network Analyser. The sample Ba3Co2Cr1.2Fe22.8O41 (x=0.6) had exhibited maximum microwave absorption of 99.8% at 5.34GHz. All the samples showed broad absorption bandwidth of 3–3.2GHz as well significantly high enough reflection loss of −10dB. Therefore, the developed Z-type hexaferrites can be used for good electromagnetic shielding/absorber applications.