Influence of dysprosium addition on the structural, morphological, electrical and magnetic properties of nano-crystalline W-type hexaferrites

Abstract

Dysporium (Dy)-substituted W-type barium hexaferrites were prepared by the citrate sol-gel-method. Crystalline structure, morphology, magnetic properties, DC resistivity and microwave absorption properties of BaNi2 Dyx Fe16-x O27 (x = 0-0.9) were studied using X-ray diffraction, transmission electron microscope (TEM), vibrating sample magnetometer and vector network analyzer and sensitive source meter, respectively. Single-phase W-type barium hexaferrites, with a chemical composition of BaNi2 Dyx Fe16-x O27 (x = 0-0.9), were formed by being heated at 1250°C for 4 h in air. The magnetic properties such as saturation magnetization (Ms), and coercivity (Hc) were calculated from hysteresis loops. Hysteresis loop measurements show that the coercivity values lie in the range of 530-560 Oe with increasing Dy content. It was also observed that magnetization decreases with the increase of Dy content. The DC resistivity was observed to increase from 0.83 × 107 to 6.92 × 107 Ω cm with increasing Dy contents due to the unavailability of Fe3+ ions. Microwave absorption properties of hexaferrite (70 wt%)-acrylic resin (30 wt%) composites were measured by the standing-wave-ratio (SWR) method in the range from 12 to 20 GHz. For sample with x = 0.6, a minimum reflection loss of -40 dB was obtained at 16.2 GHz for a layer of 1.7 mm in thickness. Sample with x = 0.9 had wide bandwidth absorption in the frequency range of 13.5-18 GHz with reflection losses less than -15 dB. Meanwhile the minimum reflection point shifts toward higher frequency with the increase of Dy content.