The electromagnetic and microwave absorbing properties of polycrystalline Y-type Ba_(1.5)Sr_(0.5)CoZnFe_(12-x)Al_xO_(22) hexaferrites over the microwave range

摘要

The influence of Al-substitution on the magnetic properties and microwave absorbing properties of single phase Ba_(1.5)Sr_(0.5)CoZnAl_xFe_(12-x)O_(22) (x = 0-1) hexaferrites has been discussed in the present work. The phase composition, morphology and saturation magnetization of the hexaferrites were investigated by X-ray diffraction, scanning electron microscopy and vibrating sample magnetometer. The results show that the structure of Y-type hexaferrite has not been affected by the substitution of Al. The morphologies of all samples display plate-like. The hysteresis loops of all samples show ferromagnetic behavior. The Ms decreases with the substitution of Al and the values of coercivity are only a few decade oersteds. The complex permittivity and permeability of Ba_(1.5)Sr_(0.5)-CoZnAl_xFe_(12-x)O_(22) were determined by microwave vector network analyzer and then the reflection loss (RL) was calculated in the frequency range of 1-18 GHz. The sample exhibits the maximum absorption of -19 dB at 11.5 GHz with an bandwidth (RL ＜ -10 dB) of more than 6 GHz for x = 0.3.